Wikipedia:Reference desk/Science: Difference between revisions
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:::A brief explanation is given in our article: [[Rail adhesion]]. The part of the wheel in contact with the rail is not quite flat, and this slight tapering of the tread ensures that "when the train encounters a bend, the wheelset displaces laterally slightly, so that the outer wheel speeds up (linearly) and the inner wheel slows down, causing the train to turn the corner". Perhaps a rail expert can give a fuller explanation? [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 23:14, 4 December 2010 (UTC) |
:::A brief explanation is given in our article: [[Rail adhesion]]. The part of the wheel in contact with the rail is not quite flat, and this slight tapering of the tread ensures that "when the train encounters a bend, the wheelset displaces laterally slightly, so that the outer wheel speeds up (linearly) and the inner wheel slows down, causing the train to turn the corner". Perhaps a rail expert can give a fuller explanation? [[User:Dbfirs|''<font face="verdana"><font color="blue">D</font><font color="#00ccff">b</font><font color="#44ffcc">f</font><font color="66ff66">i</font><font color="44ee44">r</font><font color="44aa44">s</font></font>'']] 23:14, 4 December 2010 (UTC) |
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::::The trick is that the bit of the left wheel that's touching the rail isn't at the same distance from the axle as the bit of the right wheel that's touching the rail. One of them has to travel further because it's on the outer rail of the curve, but it does travel further because it's also further from the axle. --Anonymous, 04:44 UTC, December 5, 2010. |
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== problems with [[WWVB]] NIST time radio broadcast == |
== problems with [[WWVB]] NIST time radio broadcast == |
Revision as of 04:44, 5 December 2010
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November 30
Position of maximum depression on classical guitar top.
At present I am in the process of writing an article on the construction of the classical guitar, and am proposing a different method of reinforcing the top-plate. The method consists of a set of bars, radiating from a position in front of the bridge, which is where maximum deflection occurs, due to the action of the strings when plucked. Where that position is, can be calculated, I believe, with a formula to do with Modulus of Elasticity, when the following is known: The type of wood and thickness of the top-plate. The total tensile and torsional force applied to the bridge, from the strings. The edge pressure from the bridge. This little information is gained from the mechanical drafting certificate course I did more than 40 years ago, hence the sketchy description. —Preceding unsigned comment added by 58.175.87.33 (talk) 04:27, 30 November 2010 (UTC)
- And your question is . . . ? 87.81.230.195 (talk) 14:25, 30 November 2010 (UTC)
- We do have articles on Classical guitar and Classical guitar_making -- are they helpful? --- Medical geneticist (talk) 21:41, 30 November 2010 (UTC)
- How accurate do you want the results? There is no shortage of finite element analysis applied to guitar body: Modal analysis of an acoustic guitar by finite element came up in a web search; and you can find even more scholarly, technical, and accurate modeling with a little effort. Obviously, the specific node point of maximum vibration amplitude is going to depend on the guitar body shape, materials, and how accurately your mathematical model matches physical reality. Nimur (talk) 21:49, 30 November 2010 (UTC)
Relativity questions
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The Phenomenon of Far Event DilationFor a given event eA happened at time tA and location A, an observer at location O uses a camcorder with timer to record event eA, then the recorded event time ta will always behind tA, this is the phenomenon of Far Event Dilation. This is prepared for "Distance Relativity", please comment. 1. The Equation of Far Event Dilation The recorded event time ta can be calculated by ta=tA+(AO/c’) ---(1), c’ is the speed of light in the environment. 2. The Equation of Event Period If the event ends at location B and time tB, then the recorded time period can be calculated by (tb-ta)=(tB-tA)+((BO-AO)/c’) ---(2). 2-1. When BO=AO, that means, if A and B are located on the same sphere with center O, then, the recorded event period is always the same as the actual time period. 2-2. When BO>AO, that means, the event ends at a point farther away, then the recorded event period is larger than the actual event period. The event looks happening slower in the video. 2-3. When BO<AO, that means, the event ends at a point closer to O, then the recorded event period is smaller than the actual event period. The event looks happening quicker in the video.Jh17710 (talk) 06:27, 30 November 2010 (UTC) Distance RelativityNow, let us study the Far Event Dilation in one dimension space. We assume the event points A or B and the location O of the observer are always on the same line. We also focus on cases that either the event moves or the observer moves at constant velocity v. Then we will have two sets of time equations and one set of velocity equations. This is the main subject, please comment. 3. When observer moves, then |BO-AO|=v(tb-ta) 3-1. When BO>AO, (tb-ta)=(c’/(c’-v))(tB-tA) ---(3) 3-2. When BO<AO, (tb-ta)=(c’/(c’+v))(tB-tA) ---(4) 4. When event moves, then |BO-AO|=v(tB-tA) 4-1. When BO>AO, (tb-ta)=((c’+v)/c’)(tB-tA) ---(5) 4-2. When BO<AO, (tb-ta)=((c’-v)/c’)(tB-tA) ---(6) 5. Let the event be the motion of an object from A to B under the constant velocity of v and let the speed of that object be calculated as V by the observer, then: 5-1. When BO>AO, V=(c’/(c’+v))v ---(7), particularly when v=c’, we have V=c’/2. 5-2. When BO<AO, V=(c’/(c’-v))v ---(8), when v=c’, we find out V is infinitely fast. For example, if a base ball flies to me at the speed of c’ and when it passes the sign of 30 feet, that particular picture will take about 100 nanoseconds to reach my eyes, but, at around 99 nanoseconds, that base ball already hits my nose so that the speed of that base ball is unlimited fast to me. Actually, all photons run into our eyes at infinite fast speed.Jh17710 (talk) 06:27, 30 November 2010 (UTC) The Phenomenon of Far Ball ContractionWe can calculate the distance of a ball by the equation based on the phenomenon of Far Ball Contraction, which is “A ball looks smaller when it is farther away.” This is just to show the fact that we cannot see the dimension representing far and near, we calculate that dimension. 6. Far Ball Contraction Formula If we hold a ruler 1 foot away from our eyes and measure a ball of radius r feet at distance of L feet away from our eyes to get radius of R feet, then, when the ball moves to another distance of L’ feet, the measured radius R’ feet will be R’=(RL)/L’ ---(9). We should keep both of L and L’ larger than (1+2r) feet to make the measuring job practical. 7. When the Ball is Replaced by a Brick If we replace the far ball by a Brick and look at the length and height side of that brick, then, we don’t know how wide that brick is. That means, we judge the distance of an object by the image of the length and height of the object that is perpendicular to our sight line, and normally, we have no way to tell how wide or how deep that object is.Jh17710 (talk) 06:27, 30 November 2010 (UTC) |
Response
Jh17710: People who patrol the reference desk aren't going to answer homework questions for you; also we generally need questions to answer. It looks above like you have copied large swaths of text from some physics text somewhere. Is there a question anywhere in all of this? --Jayron32 06:48, 30 November 2010 (UTC)
- Thanks for allow this section to stay. Yes, some question is big like the idea of "infinite speed".Jh17710 (talk) 05:30, 1 December 2010 (UTC)
- There is no infinite speed. Speed is always relative between frames of reference. The practical limit to speed is the speed of light, which is very finite. The problem comes not in objects moving relative to each other; but in accelerating an object from "rest" (as defined in its own reference frame) to the speed of light. To do so would require infinite energy, which is impossible. --Jayron32 05:48, 1 December 2010 (UTC)
- Let us look at your comment one by one. I believe that there is no actual infinite speed in real world too. Yes, speed can be relative speed to a reference frame or even, visual speed like if a ball flies at speed of c/2, then, how a camcorder records that ball moving forward and backwards at distance marks of 300 feet, 600 feet, and 900 feet? We will find out the forward speed is c and the backward speed is c/3. The actual speed may not excess c, but, we are unable to prove it yet. The main reason that we are unable to accelerate an object to the speed c should be the limitation of the speed of force. If the speed of force is c, then, a force will not push or pull an object to a speed higher than c, that is reasonable. Isn't it? If a visual speed can excess c we can enjoy the feeling of the speed of light or ultralight when technology advances to certain level.Jh17710 (talk) 04:34, 2 December 2010 (UTC)
- There is no infinite speed. Speed is always relative between frames of reference. The practical limit to speed is the speed of light, which is very finite. The problem comes not in objects moving relative to each other; but in accelerating an object from "rest" (as defined in its own reference frame) to the speed of light. To do so would require infinite energy, which is impossible. --Jayron32 05:48, 1 December 2010 (UTC)
- Thanks for allow this section to stay. Yes, some question is big like the idea of "infinite speed".Jh17710 (talk) 05:30, 1 December 2010 (UTC)
- ... (earlier reply) ... and the point that the text seems to be trying to make appears false to me. For both ball and brick, we infer both distance and depth from past experience, and if we have doubt about our guess, we use parallax to check. The idea of "infinite speed" is also wrong. Have you read our article on Special relativity? Dbfirs 07:41, 30 November 2010 (UTC)
- I will read it again. However, what do you think about the recorded event time period may be smaller than the actual event time period when event started and moved closer to the observer? I can derive it in detail.Jh17710 (talk) 05:30, 1 December 2010 (UTC)
- I should also note that you're getting close to where fair use may give way to copyright violation, unless you're actually going to discuss bits and pieces of all that stuff in detail. Wnt (talk) 10:44, 30 November 2010 (UTC)
- This is my idea. I posted it once early 2008.Jh17710 (talk) 05:30, 1 December 2010 (UTC)
- Yes, there is the well-known Doppler effect where both the recorded time period and the frequency are changed by relative motion (as in an approaching emergency vehicle), but the equations are not the same for light as they are for sound (see Relativistic Doppler effect). Dbfirs 08:35, 2 December 2010 (UTC)
- Thanks for the response. I will look into the Doppler effect for sound. Could you tell me which step of the follwoing is wrong? 1. The Equation of Far Event Dilation, event happens at point A and time tA, a camcorder at point O recorded event time ta, then ta can be calculated by ta=tA+(AO/c’) ---(1), c’ is the speed of light in the environment. 2. The Equation of Event Period, if the event ends at location B and time tB, then the recorded time period can be calculated by (tb-ta)=(tB-tA)+((BO-AO)/c’) ---(2). 3. Now, let us study the Far Event Dilation in one dimensional space. We assume the event points A or B and the location O of the observer are always on the same line. We also focus on cases that event moves at constant velocity v, then |BO-AO|=v(tB-tA). When BO<AO, (tb-ta)=((c’-v)/c’)(tB-tA) ---(6), that is when event started at far end and finished at near end. 4. When v=c'/2, then (tb-ta)=(tB-tA)/2, for a base ball flies from A to B, the recorded time period is just half of the actual time period. 5. That means, the recorded speed of that base ball is twice as fast as the actual speed, from A to B. All above steps just show that the visual speed of an object can be very fast, even faster than the speed of light.Jh17710 (talk) 03:01, 3 December 2010 (UTC)
- Yes, the apparent speed of approach is given by without relativistic adjustment (could an expert please check the adjustment needed here?) so it appears to easily exceed c (the speed of light) from a Newtonian viewpoint. This does not mean that anything is actually travelling at a speed greater than c. An observer sitting on the baseball would see things differently. A similar effect can be seen when shining a rotating beam of light on a distant panorama. The reflection can appear to be travelling faster than light, but this is just an effect. No object, not even a single photon, is exceeding c. Dbfirs 15:02, 3 December 2010 (UTC)
- I told you that speed is a visual speed, not actual speed. That equation itself is the relativistic adjustment to the actual speed. I do like to understand your similar effect in more detail. Does a rotating beam of light on a distance panorama like on a big cylinder screen at far away? Does the reflection mean the refected light from the screen that the person at the center point sees? That will make a very good sample for "something" runs faster than the speed of light, but, that something is not one object. that circle of light appears at far distance are created by different photons being emitted to different directions. Do you think photons run into our eyes at unlimited fast speed?Jh17710 (talk) 06:56, 4 December 2010 (UTC)
- Photons always travel at the speed of light when they are travelling. They can be absorbed and re-emitted by transparent materials, and this explains why they appear to travel at a speed less than c in a medium with high refractive index. You might be interested in the article on phase velocity which can exceed c (and I think can approach infinity in recent experiments where photons are "stopped") Dbfirs 16:03, 4 December 2010 (UTC)
- Yes, I think we all understand this. I should ask my question differently; do you think our brain will calculate the speed of photons run into our eyes at unlimited fast of speed? I think that is the reason why every instant view in front of our eyes is so clear, no matter how fast we turn our focus points to different location. And the whole view appears right at the moment we open our eyes. Our brains do have a limit speed of images processing, however, the infinitely fast visual speed of incoming photons does help us to have very stable views. Thank God.Jh17710 (talk) 22:05, 5 December 2010 (UTC)
- Photons always travel at the speed of light when they are travelling. They can be absorbed and re-emitted by transparent materials, and this explains why they appear to travel at a speed less than c in a medium with high refractive index. You might be interested in the article on phase velocity which can exceed c (and I think can approach infinity in recent experiments where photons are "stopped") Dbfirs 16:03, 4 December 2010 (UTC)
- I told you that speed is a visual speed, not actual speed. That equation itself is the relativistic adjustment to the actual speed. I do like to understand your similar effect in more detail. Does a rotating beam of light on a distance panorama like on a big cylinder screen at far away? Does the reflection mean the refected light from the screen that the person at the center point sees? That will make a very good sample for "something" runs faster than the speed of light, but, that something is not one object. that circle of light appears at far distance are created by different photons being emitted to different directions. Do you think photons run into our eyes at unlimited fast speed?Jh17710 (talk) 06:56, 4 December 2010 (UTC)
- Yes, the apparent speed of approach is given by without relativistic adjustment (could an expert please check the adjustment needed here?) so it appears to easily exceed c (the speed of light) from a Newtonian viewpoint. This does not mean that anything is actually travelling at a speed greater than c. An observer sitting on the baseball would see things differently. A similar effect can be seen when shining a rotating beam of light on a distant panorama. The reflection can appear to be travelling faster than light, but this is just an effect. No object, not even a single photon, is exceeding c. Dbfirs 15:02, 3 December 2010 (UTC)
- Thanks for the response. I will look into the Doppler effect for sound. Could you tell me which step of the follwoing is wrong? 1. The Equation of Far Event Dilation, event happens at point A and time tA, a camcorder at point O recorded event time ta, then ta can be calculated by ta=tA+(AO/c’) ---(1), c’ is the speed of light in the environment. 2. The Equation of Event Period, if the event ends at location B and time tB, then the recorded time period can be calculated by (tb-ta)=(tB-tA)+((BO-AO)/c’) ---(2). 3. Now, let us study the Far Event Dilation in one dimensional space. We assume the event points A or B and the location O of the observer are always on the same line. We also focus on cases that event moves at constant velocity v, then |BO-AO|=v(tB-tA). When BO<AO, (tb-ta)=((c’-v)/c’)(tB-tA) ---(6), that is when event started at far end and finished at near end. 4. When v=c'/2, then (tb-ta)=(tB-tA)/2, for a base ball flies from A to B, the recorded time period is just half of the actual time period. 5. That means, the recorded speed of that base ball is twice as fast as the actual speed, from A to B. All above steps just show that the visual speed of an object can be very fast, even faster than the speed of light.Jh17710 (talk) 03:01, 3 December 2010 (UTC)
- Yes, there is the well-known Doppler effect where both the recorded time period and the frequency are changed by relative motion (as in an approaching emergency vehicle), but the equations are not the same for light as they are for sound (see Relativistic Doppler effect). Dbfirs 08:35, 2 December 2010 (UTC)
- This is my idea. I posted it once early 2008.Jh17710 (talk) 05:30, 1 December 2010 (UTC)
is it possible to blow up a planet like in Star Wars?
Lets say there were a really big gun or energy beam aimed at a planet the size of Earth? Could it actually cause the Earth to blow up, or would it just cause earthquakes and cause the rock to melt and things like this? I am not talking about an impact event, this is like something worse than that, like the Death Star, pretty much. But would the laws of phsics allow a planet to EXPLODE? is it even posible? —Preceding unsigned comment added by The Fat Man Who Never Came Back (talk • contribs) 03:42, November 30, 2010
- Sure, it's possible in some sense, but not like in Star Wars. All in all, you should realize this planet is basically a lump of metal several thousand miles in diameter, stuff that likes to congregate (gravity) and will not easily be scattered into a gazillion pieces. The energy required to actually blow it up as you describe would be an immense amount.--Rallette (talk) 09:00, 30 November 2010 (UTC)
- Someone worked out details on what you'll need to do it here. Have fun! --Sean 14:22, 30 November 2010 (UTC)
- Also, the Earth is largely magma already, but supplying enough energy to destroy it would surely melt the rest of it, so it would look more like blowing a raindrop apart than a solid object. Sci-fi shows never seem to get this right. StuRat (talk) 23:50, 30 November 2010 (UTC)
- Incidentally, the amount of energy required to vaporize a mass of iron the size of earth is around 3.7x10^31 Joules. That is equal to 9,232 trillion 1 megaton nuclear warheads, or 85 billion years of current human energy consumption. Googlemeister (talk) 16:51, 2 December 2010 (UTC)
What would happen if scientists blew up the moon?
What would be the consequences here on Earth if we blew up the moon? I imagine there would be all sorts of environmental disasters, but would there be any benefits?--The Fat Man Who Never Came Back (talk) 08:44, 30 November 2010 (UTC)
- Some of this was discussed at Wikipedia:Reference_desk/Archives/Science/2006_November 7#Blowing up the moon and Wikipedia:Reference_desk/Archives/Science/2007 May 6#Earth's Spin. Wnt (talk) 10:47, 30 November 2010 (UTC)
- This is one advantage. Paul (Stansifer) 14:41, 30 November 2010 (UTC)
- You attribute some pretty impressive powers to these 'scientists'. In any event, the answer depends on what you mean by 'blew up'. If you just fracture it without giving any of the chunks lunar escape velocity, then they'll pretty much settle back into a new Moon. (The surface features won't be the same, obviously, but if the whole system stays gravitationally bound then you'll eventually get a Moon-sized approximately-spherical lump back.) If you manage to compress enough of it into a wee tiny black hole (bigger than CERN LHC-sized, so it won't evaporate immediately) it will eventually all collapse into a stable Moon-massed black hole (see Roger MacBride Allen's The Ring of Charon). In either case, not a whole lot happens on Earth. The former case generates an impressive light show, and the latter case makes it a bit darker at night, but tides won't be appreciably affected and the Earth will carry on essentially unchanged.
- If you redistribute the mass of the Moon (as by pulverizing it into a ring in lunar orbit), or remove the Moon and all its mass entirely by some yet to be discovered magical phenomenon (or by virtue of it actually being a camouflaged alien spaceship, see David Weber's Mutineers' Moon) then you have serious effects on Earth. Getting rid of tides (well, most tides — there will still be miniscule tides from the Sun's attraction) will screw over a lot of coastal life. Depending on how quickly you remove or re-adjust the Moon's position, you might also get some serious earthquakes going on, as rapidly removing the Moon's pull on Earth may have the effect of 'twanging' crust.
- If you use some unimaginably violent explosion to 'blow up' the Moon in what might be the most conventional picture of such an event, you're very likely to have some Texas-size chunks hit the Earth. When that happens, we have a massive winter, and most life on Earth dies. What benefits did you have in mind? TenOfAllTrades(talk) 14:45, 30 November 2010 (UTC)
- Here's a fun article on the subject : The Straight Dope:I plan to destroy the moon. What effect would this have on the earth?
- APL (talk) 15:37, 30 November 2010 (UTC)
- Related question: does humanity at present time have the capacity to blow the Moon to smithereens? Bus stop (talk) 15:45, 30 November 2010 (UTC)
- Certainly not. --Sean 18:51, 30 November 2010 (UTC)
- Related question: does humanity at present time have the capacity to blow the Moon to smithereens? Bus stop (talk) 15:45, 30 November 2010 (UTC)
- All this and yet nobody mentions the late Alexander Abian. --Anonymous, 23:24 UTC, November 30, 2010.
Can we blow up comets?
A few years ago, we tried and failed to blow up a comet. We shot a missile at it, and it caused an explosion and released a dust cloud, but unfortunately the comet was not destroyed. In the future, if we shoot more powerful projectiles at comets, is it possible to destroy them altogether? What would happen to the galaxy if we eliminated all comets and meteors and asteroids?--The Fat Man Who Never Came Back (talk) 08:48, 30 November 2010 (UTC)
- I think you've read the article wrong if you think the Deep Impact space mission was an attempt to destroy a comet. Nil Einne (talk) 10:53, 30 November 2010 (UTC)
- If you blow it up, you just seperate a mass into smaller bits of mass. Each of the bits are still comets, just smaller. So nothing would "happen to the galaxy", except it would have smaller comets. --Lgriot (talk) 12:15, 30 November 2010 (UTC)
- As has been hinted at above you should read the galaxy article to adjust your mental image of the scale of things.
- It sounds like you may have meant solar system instead of 'galaxy'. If so, have a read of the Oort cloud article to get an idea of what sized job ridding the solar system of all comets would be. Blakk and ekka 12:33, 30 November 2010 (UTC)
- All the comets in the Solar System make up the mass of about 5 Earths, and less than 1% of the mass of the Solar System as a whole. There's nothing you can do to a comet to have much effect on the Solar System, much less the galaxy. --Sean 14:25, 30 November 2010 (UTC)
- First, Deep Impact was not attempting to blow up a comet any more then someone who crashes their car into the side of a mountain is trying to blow up the mountain. Second, the results of destroying a comet would have only the very smallest of effects on the solar system (and even then, only if you used something like antimatter to remove the mass entirely). It is unlikely that such changes would be detectable. On a local scale, if you exploded a comet that transected the earth's orbit, you might have some nice meteor showers in the future, but impacts to the planetary orbits would be essentially unaffected. Googlemeister (talk) 16:41, 2 December 2010 (UTC)
Which organelles contain DNA?
I always thought it was just the nucleus & either mitochondria (in animals) or chloroplasts (in plants). However, I found a passage in Lewis Thomas's "The Lives of a Cell" where he intimates that this property is shared by other organelles too:
Mitochondria are stable and responsible lodgers, and I choose to trust them. But what of the other little animals, similarly established in my cells, sorting and balancing me, clustering me together? My centrioles, basal bodies, and probably a good many other more obscure tiny beings at work inside my cells, each with its own special genome, are as foreign, and as essential, as aphids in anthills.
Is this an inaccuracy? The book was written in 1974. Thanks. AGradman / how the subject page looked at 12:19, 30 November 2010 (UTC)
- None of these sub-cellular bodies have their own genome. It sounds like Thomas may be putting forward a variation of Endosymbiotic theory. Blakk and ekka 12:49, 30 November 2010 (UTC)
- I'm not sure if it was just a poor choice of words or genuine confusion but do note nearly all eukaryotes have mitochondrion, including plants. Nil Einne (talk) 13:53, 30 November 2010 (UTC)
- In the case of centrioles, it may have been based on outdated research. From centrosome:
- Research in 2006 indicated that centrosomes from Surf clam eggs contain RNA sequences. The sequences identified were found in "few to no" other places in the cell, and do not appear in existing genome databases. One identified RNA sequence contains a putative RNA polymerase, leading to the hypothesis of an RNA based genome within the centrosome. However, subsequent research has shown that centrosome do not contain their own DNA-based genomes. While it was confirmed that RNA molecules associate with centrosomes, the sequences have still been found within the nucleus. Furthermore, centrosomes can form de novo after having been removed (e.g. by laser irradiation) from normal cells.
- --Sean 14:29, 30 November 2010 (UTC)
velocity of sound
why does the velocity of sound in water decrease after reaching a maximum velocity at a certain temperature —Preceding unsigned comment added by 41.221.209.6 (talk) 13:46, 30 November 2010 (UTC)
- The effect I'm familiar with is that as a function of depth, the sound speed increases after reaching a minimum at a certain depth (which turns out to be temperature-related). Our Speed of sound article shows the effect
but doesn't explain it welland explains it briefly. There's abetterfuller discussion at DOSITS. In a nutshell: the speed of sound in seawater is proportional to temperature, to pressure, and to depth. Temperature decreases as depth increases, which is why the sound speed initially decreases as you descend below the surface. But then, of course, pressure begins to increase, and so the sound speed goes back up as you go really deep. —Steve Summit (talk) 14:12, 30 November 2010 (UTC), tweaked 14:48, 30 November 2010 (UTC), again 23:58, 30 November 2010 (UTC)- Speed of sound is related to density. Water is densest at 34F, so sound will travel through water fastest at that temperature. Pressure has a minor impact on the speed of sound in seawater, but it is a smaller impact then temperature. Googlemeister (talk) 16:36, 2 December 2010 (UTC)
- 3.98°C is about 39°F not 34°F Dbfirs 16:11, 4 December 2010 (UTC)
Daytime flash dreams
Sometimes I tend to experience ultra-short (for about 0,5 sec) unconscious flash dreams while not sleeping, just resting. They look like normal night dreams, but appear even when my eyes are open. Most recently for example I saw a nice red motorcycle with bald biker. Is there a name for such phenomenon? —Preceding unsigned comment added by 89.77.158.172 (talk) 17:01, 30 November 2010 (UTC)
- Well, this is not really a medical question and is quite common, so see daytime parahypnagogia--Aspro (talk) 17:09, 30 November 2010 (UTC)
Margarine and oils without saturated fat
Are there any brands or kinds of margarines and oils with little saturated fat? Even the "Light" margarine I have in front of me is over 9% saturated fat. Thanks 92.28.247.40 (talk) 17:26, 30 November 2010 (UTC)
- Shortenings like margarine and crisco are just vegetable oil that's been "partially hydrogenated". Saturation is one of the main reasons these things are solid at room temperature. The unsaturated fat is lowers the melting temperature to make vegetable oil a liquid). The lowest saturated-fat content I see on that article's table is canola oil at 7%, and all the solid ones are somewhat higher. DMacks (talk) 17:34, 30 November 2010 (UTC)
- In general the more saturated the oil the lower the melting point. So unsaturated oils are liquid at room temperature. However the length of the molecule (called the chain length) also plays a role, the shorter the chain the lower the melting point. As far as health goes just looking at saturated vs unsaturated is not enough, there is plenty of evidence that certain chain lengths are much unhealthier. In general longer chains are less healthy. So you can have an unsaturated, long chain oil that is less healthy that a short chain, but saturated oil. This is the main reason people switched to saturated palm oils, they might be saturated, but their oil has few bad health effects, and some believe actually improve health! In general it's best to eat oils that are commonly found in food. The reason is that the health effects of the oil are directly related to how well the body can "burn" the oil (lipid) for fuel. To burn the lipid requires enzymes, and the body has more enzymes for some types than for others. Another thing, Essential fatty acids (EFA) are the best type of lipid to eat, but they are all liquid and polyunsaturated. A manufacturer has a choice - they can make the margarine with some saturated fat, and a little unsaturated, or they can make it with polyunsaturated and more saturated (the high and low melting points cancel each other out). Which is better? You are getting more saturated fat, but also more EFAs, or less saturated fat, but no EFAs. My feeling is that the version with saturated, but also polyunsaturated is better, but the exact answer on the proper balance requires lots of studies that as far as I know have not been done. A final point is that I think it's better to eat a margarine with a variety of fat types in it, vs. one that is just one kind of lipid - even if you have to eat some saturated fat in the process. Whew, this post was longer than I expected, I hope it helps you. Ariel. (talk) 19:17, 30 November 2010 (UTC)
- I cannot see the answer to my question in there, but thanks for trying. 92.28.247.40 (talk) 20:07, 30 November 2010 (UTC)
- Basically what he's? saying is 1) It's rather unlikely there are any margarines without saturated oils. 2) If your concerned about health, just avoiding all saturated fats likely isn't the way to go (technically you didn't ask about this but given your question I don't think it was an unresonable response). Note that considering no 2 even if someone could make an oil without saturated fats, it's not likely they would. According to [1] one of the lowest saturated fat oils is enova brand but um [2]... In any case it sounds like weird stuff [3] P.S. It's also possible Ariel missed your point about oils at first since you referred to the saturated fat content in margarine rather then oils. I did. Nil Einne (talk) 20:30, 30 November 2010 (UTC)
- One point is that the people who first made margarine wanted it to resemble butter, but it was a white liquid, not a yellow solid, so they added coloring and saturated fats (or the even worse trans-fats). Now that we know how unhealthy it is to solidify the margarine (which pretty much also will solidify in your veins), perhaps we should re-evaluate our need for it to be solid. You can get a squirt bottle of liquid margarine, and that sounds fine to me. You can probably butter your toast even quicker that way. StuRat (talk) 00:20, 1 December 2010 (UTC)
- I think it's important to bear in mind two things. First is that triglycerides and other lipids are a heterogeneous collection of compounds, with many individual variations of molecular structure, any and all of which may be significant. Each lipid chain of the triglyceride has a varying length and a variable pattern of double bonds. Things like omega-3 fatty acids, omega-6 fatty acids, conjugated linoleic acid, arachidonic acid, eicosapentanoic acid and so on all have their own special purposes and effects. They are not merely "fuel", but form the cell membrane, modify proteins, and are used to make potent signalling molecules like prostaglandins, ceramide, sphingolipids .... it's a whole branch of biochemistry.
- The other thing to bear in mind is that partially hydrogenated vegetable oil is not a natural fat, but a crude chemical mock-up of an animal fat in which the precise chemical components have been randomized. It's well known that trans fats have little place in normal biology, but there could be other random alterations.
- What I would draw from this is that one should be very conservative regarding lipid sources, choosing sources with a long history of use like olive oil over those which someone has just started pressing out of a new plant, or worse, which have been created chemically. Wnt (talk) 11:04, 1 December 2010 (UTC)
- It comes from a plant in either case, whether a biologic plant or a chemical plant. :-) StuRat (talk) 23:21, 1 December 2010 (UTC)
Bioluminescence
hi, Today I saw (in a video) a creature which made a Bioluminescence. It looked like fireworks. the liquid which he spitted (it was a marine animmal) had glown for 3 seconds,and then turn-off. and then, like a lightning it glew powerfully. does anyone know what that sea animmal's name? 84.228.119.63 (talk) —Preceding undated comment added 17:51, 30 November 2010 (UTC).
Well. There is this one, and as ever, Wikipedia has an article on it:Heterocarpus--Aspro (talk) 19:41, 30 November 2010 (UTC)
- We also have Bioluminescence of course which lists a bunch of animals Nil Einne (talk) 21:32, 30 November 2010 (UTC)
- The article on Heterocarpus however, features a shrimp which spits streams of blue luminous secretions and thus directly address the OP's question, which Bioluminescence does not. Otherwise, I would have provided that link. Which I did not, because it didn't. Yet, Heterocarpus links to any way -if you had read it!--Aspro (talk) 23:31, 30 November 2010 (UTC)
- Apologies I misread the OPs question as being about which when splited grew for 3 seconds which I thought could easily apply to many animals showing bioluminescence. However I still believe the link was helpful as it teaches the OP that we also have an article on general concepts such as this, which list animals which show the concept so they may be more aware they can look themselves in the future (although unfortunately in this case the bioluminescence article doesn't seem to list Heterocarpus either directly or indirectly). While it's true (and expected) the article links to the concept, it may not occur to the OP to click on it.
- Also, while it seems most likely your answer is what the OP is referring to, and this is not a field I know much about, I wonder if it's really the only possible correct answer as your second response seems to imply. As I understand the Vampyroteuthis infernalis article (which is linked from bioluminescence) they release a 'bioluminescent mucus containing innumerable orbs of blue light' (our article actually refers to fireworks although that may be a common description for bioluminescence). This may not be really liquid, although it's not clear how precise that term was meant (did the OP actually see the liquid, did they just see it in water and it looked like liquid?). (There may also be debate about whether spit is accurate for what the vampire squid does although again it seems possible the OP is using the term loosely.) Even less likely but perhaps still worth mentioning, our article says Antarctic krill spits out biolumiscent phytoplankton. If it is possible the OP is referring to something else, it seems to me there's even more merit to the general link
- Nil Einne (talk)
- P.S. [4] claims there's also planktonic protozoans that spit bioluminescent 'stuff' but unfortunately I've been unable to find what they're referring to from quite a few searches. Planktonic protozoans sounds unlikely to be thought of as marine animals, but who knows I guess. Nil Einne (talk) 12:55, 1 December 2010 (UTC)
- P.P.S. From what I can tell, we don't have any real videos of Vampyroteuthis infernalis releasing their bioluminescent liquid (some simulations are all I could find), perhaps not surprising given the depth they live in, so it seems unlikely this is what the OP saw. (Planet Earth did have video of it using its photophores.) Nil Einne (talk) 12:55, 1 December 2010 (UTC)
Aggression, dementia, disinhibition
1) Some elderly people seem to be habitually hostile - are there any other things apart from dementia that cause this aggression in some elderly? 2) Does having dementia make people disinhibited? Thanks 92.28.247.40 (talk) 18:00, 30 November 2010 (UTC)
- When any disease or injury effects the normal functioning of the pre-frontal cortex and especially when executive functions with in them are effected, it can result in more aggressive behaviour and/or dis-inhibition than would normally expected. Dementia does not always lead to more aggression but is more common than not. --Aspro (talk) 18:21, 30 November 2010 (UTC)
Ok, so aggression is a common result of dementia, but does being aggressive and elderly suggest dementia? Thanks. 92.28.247.40 (talk) 22:18, 30 November 2010 (UTC)
- On its own - no. In combination with other things - maybe. Try the alzheimers-research.org.uk website for some more information. --Tagishsimon (talk) 22:22, 30 November 2010 (UTC)
- Wouldn't hurt to check for it, but some old people can just be mean ol' bastards. HalfShadow 22:25, 30 November 2010 (UTC)
- I seem to recall reading an article on social inhibitions, which claimed they were maximised in teenagers/young adults, and gradually decreased after that. This would suggest that elderly people in general are going to be less inhibited than other adults, regardless of whether they have dementia. Does anyone know more about this, or know where to find a referenced discussion? 86.161.108.241 (talk) 14:10, 1 December 2010 (UTC)
- Being elderly and aggressive may suggest the effects of jading and nothing more. I wouldn't suggest that Grumpy Old Men have to have a medical reason for being that way when conditioning explains it quite well.
⋙–Berean–Hunter—► ((⊕)) 17:22, 2 December 2010 (UTC)
Why must some truffles be found and not grown?
This MSNBC article says that Piedmont white truffles cost around US$3,000 per pound because of low supply, and also claims "this is one food that can’t be formulated in a lab or grown in a greenhouse." Why? By now there must have been attempts to farm these truffles in order to try to cash in on this. What were the results? Comet Tuttle (talk) 19:02, 30 November 2010 (UTC)
- That is a misleading statement. Truffle farms are, essentially, tree farms. It takes about 30 years to grow the trees (and the truffles). So, that statement could be true of any large tree. For example, you could claim that Christmas Trees are the one decoration that can't be formulated in a lab or grown in a greenhouse. What you actually mean is that the tree is big. You need a lot of room. So, for a lot of trees, you'd need an enormous greenhouse. Obviously, you'd use a field instead - which is what truffle farms use, large fields. -- kainaw™ 19:09, 30 November 2010 (UTC)
- (after e/c)
- Truffles grow on the roots of Oak trees. Perhaps they simply mean that truffles need vast orchards to cultivate, even though the truffles themselves are rather small? (Literally, adult oak trees are unlikely to grow in either a lab or all but the largest greenhouses.) APL (talk) 19:11, 30 November 2010 (UTC)
- I see; thank you. I had jumped to the conclusion that finding truffles was a hunter/gatherer task and a crapshoot, rather than an organized and planned farming process. Comet Tuttle (talk) 19:26, 30 November 2010 (UTC)
- Note that unsurprisingly our article has a section on cultivation Truffle (fungus)#Cultivation Nil Einne (talk) 20:34, 30 November 2010 (UTC)
- The section is disappointingly sparse regarding information on which type of truffle is/has been cultivated. My understanding is that while black truffles are amenable to directed cultivation, white truffles are more recalcitrant. It isn't simply a matter of "plant tree->gather truffles". Not every tree of a host species will produce truffles, even if it's in a truffle producing area. We don't yet know exactly what the truffle is looking for in growing conditions. That's why it's said that (certain) truffles can't be cultivated. You can plant a bunch of host trees to increase the chance of getting truffles, but there's no guarantee that when they mature you'll be producing any significant amount of truffles from them. -- 140.142.20.229 (talk) 02:06, 1 December 2010 (UTC)
- And it's not just getting them to grow on a tree's roots, but getting them to fruit and catching them when they do so. --Sean 16:02, 1 December 2010 (UTC)
- The section is disappointingly sparse regarding information on which type of truffle is/has been cultivated. My understanding is that while black truffles are amenable to directed cultivation, white truffles are more recalcitrant. It isn't simply a matter of "plant tree->gather truffles". Not every tree of a host species will produce truffles, even if it's in a truffle producing area. We don't yet know exactly what the truffle is looking for in growing conditions. That's why it's said that (certain) truffles can't be cultivated. You can plant a bunch of host trees to increase the chance of getting truffles, but there's no guarantee that when they mature you'll be producing any significant amount of truffles from them. -- 140.142.20.229 (talk) 02:06, 1 December 2010 (UTC)
December 1
NGC identification in Veil Nebula
The Veil Nebula in Cygnus comprises several NGC/IC items: 6960 (the Witch's Broom), 6992/6995/IC1340 (Eastern Veil), 6974 (faint patch near north boundary) -- and the one I'm asking about: NGC 6979. This is frequently associated with Pickering's Triangle (see, e.g. Astronomy magazine, or indeed Google search for Pickering+triangle+"NGC+6979"), but the coords usually given for 6979 (and displayed in Uranometria) appear to be closer to 6974 -- and Pickering's Triangle was reputedly discovered only photographically, in the early 1900s. So the question is: is NGC 6979 really Pickering's Triangle, and is there a clear, definitive reference for the identity? -- Elphion (talk) 01:43, 1 December 2010 (UTC)
I should add, our own article on the Veil Nebula -- the one I've been working on -- is not yet "definitive" :-) -- Elphion (talk) 01:46, 1 December 2010 (UTC)
- I think I've found a reasonable definitive source: the NGC/IC Project (under NGC 1979) makes it clear that although Herschel's original position was none too precise, it referred not to Pickering's Triangle but to another knot of nebulosity. -- Elphion (talk) 21:33, 1 December 2010 (UTC)
- Although the error is trivial and obvious, do not be confused by Elphion above having inadvertantly mistyped "1979" intending 6979. Muphry strikes again! :-) 87.81.230.195 (talk) 14:18, 4 December 2010 (UTC)
Plastic-mirror
Can someone please tell if there's a material bendable and reflects (something like a plastic-mirror). If so, could you leave the name and the link in wikipedia (if exists).
Thank You. PD: sorry for my english, not my first language. —Preceding unsigned comment added by 190.218.125.158 (talk) 02:21, 1 December 2010 (UTC)
- You can get stainless steel mirror sheets down to fractions of a millimeter that would be quite bendable. Something like this. Vespine (talk) 02:34, 1 December 2010 (UTC)
- Also, aluminized mylar (we'll see if that comes up blue). --Trovatore (talk) 02:49, 1 December 2010 (UTC)
- See also deformable mirror. --Mr.98 (talk) 03:21, 1 December 2010 (UTC)
Thank you, learned a lot. Is there anything solid that reflects exactly like a mirror? —Preceding unsigned comment added by 190.218.125.158 (talk) 04:14, 1 December 2010 (UTC)
- I don't quite understand; if it's solid, and reflects like a mirror, then it is a mirror, right ? StuRat (talk) 05:25, 1 December 2010 (UTC)
- The 3 mm stainless steel mirror sheets in the link above would be quite stiff, if that's what you mean by "solid". Or the 0.8 mm mirror sheets would be more bendable, but still much stiffer than aluminized mylar. Or were you looking for something like a curved mirror, which is bent but very stiff? Red Act (talk) 05:45, 1 December 2010 (UTC)
haha sorry :P . What i meant was something like silly putty —Preceding unsigned comment added by 190.218.125.158 (talk) 09:15, 1 December 2010 (UTC)
- I don't think anything like putty could ever work as a mirror, because you need a even surface to make a recognizable reflection. A random blob would reflect light in all directions, and not make a clear image. StuRat (talk) 23:17, 1 December 2010 (UTC)
- Silly Putty is actually a viscoelastic fluid, a type of non-Newtonian fluid, rather than being a (Hookean) solid. Specular fluids certainly exist; liquid mercury comes to mind, or even water at a grazing angle. And Silly Putty itself exhibits some specular reflection, in addition to diffuse reflection. But I'm having no luck trying to find a viscoelastic fluid that's highly specular in the visible spectrum. Red Act (talk) 00:50, 2 December 2010 (UTC)
- What does the OP want to use it for? If they want to cast a mirrored shape, then an epoxy (or other casting resin) which contains a metal filler, can be rubbed with wire wool and buffed up to a mirror like shine. Resins and putties are available with a choice of several different fillers. Alternatively, coat the object with conductive paint, dry, then electroplate with chrome, etc. --Aspro (talk) 16:55, 2 December 2010 (UTC)
Laser distance meters
Are there any laser distance meters that are more-or-less equivalent to a Leica Disto (particularly in the sense of "having a range of at least 70 m"), but, rather than being hand-held units, come in the form of (essentially) a circuit board with a laser attached to it? That is to say, I'm looking for something programmable, intended for remote use, and long-range. --superioridad (discusión) 02:59, 1 December 2010 (UTC)
- What does the OP want to use it for? Are you thinking of something along these lines. Laser scanner--Aspro (talk) 17:02, 2 December 2010 (UTC)
- Those products are for imaging, i.e. constructing 3D models of objects. I want to use it to measure the distance between two objects that will be separated by several dozen meters, and measure how that distance changes (which will only be slightly, so the laser won't end up e.g. pointing in the wrong direction). --superioridad (discusión) 01:57, 3 December 2010 (UTC)
- Sounds like a Michelson interferometer might be useful here. From the initial positions, you can get changes in distance measured down to a fraction of the wavelenth of your laser (limited by the detector's ability to sense changes in light intensity). It requires that the object's reflection always point back towards your device. Another way is based on time-of-flight, using a gated laser pulse or a waveform. That lets you measure absolute distances (rather than just changes), limited by resolution of your timer. Both are pretty common undergraduate-level lab projects, with various types of detectors, data aquisition/processing, etc. I'm sure there are USB or serial devices available for hobbiests and teaching-labs, but I don't see a premade one off-hand in my PASCO catalog. DMacks (talk) 21:40, 3 December 2010 (UTC)
- Those products are for imaging, i.e. constructing 3D models of objects. I want to use it to measure the distance between two objects that will be separated by several dozen meters, and measure how that distance changes (which will only be slightly, so the laser won't end up e.g. pointing in the wrong direction). --superioridad (discusión) 01:57, 3 December 2010 (UTC)
Global Warming and Ice Age
In The Day After Tomorrow, global warming caused an Ice Age. Could this really possibly happen in real life? —Preceding unsigned comment added by 202.168.107.2 (talk) 03:11, 1 December 2010 (UTC)
- Global warming is a misnomer; the preferred term is "climate change", since what happens as a result of increased greenhouse gases is more nuanced than simply "the earth gets hotter". What is much more likely to happen is actually greater swings in climatic changes rather than simply a gradual increase in temperatures; one could envision decades or centuries that were markedly hotter OR colder than the current "normal" temperatures. The problem faced with anthropogenic climate change is not that it is predicted to make everything uniformly warmer; if it were that simple then it would be easier to design a fix; the earth is not merely going to get warmer on a regimented schedule. What is predicted to happen is an increasing unpredictability in climate; so there is no way to prepare for rapid and large changes. One of the problems with popular media when dealing with these problems is that there is a misinterpretation of these predictions. What most mainstream scientists who work in the area agree on is "We know climate is going to change in unpredictable ways", which gets misinterpreted as "We can't predict how climate will change" which gets further assumed to mean "We can't predict anything". You may also want to check out Snowball Earth for a past event with similar implication. --Jayron32 03:55, 1 December 2010 (UTC)
- Huh? For years and years we've been told about Global Warming, and now you say that global warming is not going to happen, but just "greater swings in climate changes", in other words the normal ups and downs of the weather. We've been had! 92.24.177.111 (talk) 12:08, 4 December 2010 (UTC)
- The movie is based on a genuine possibility but is vastly exaggerated. The climate of Europe is much warmer than it ought to be given its latitude, mainly because the Gulf Stream carries large amounts of heat there from the tropics. The Gulf Stream is ultimately driven by the sinking of cold salty water in the Arctic and North Atlantic, as part of the thermohaline circulation. There is a significant possibility that global warming, by eliminating Arctic ice, could cause the sinking of cold water to stop, thereby stopping the Gulf Stream and greatly chilling the climate of Europe. Such an interruption is thought to have happened during a cold period called the Younger Dryas, over 10,000 years ago, as a result of a sudden massive influx of fresh water into the North Atlantic. Even if it did happen, though, there is no way it could be anywhere near as rapid and dramatic as shown in the movie (as I've heard; I haven't seen it). Furthermore, the main effects would be on Europe, with lesser effects on North America. Looie496 (talk) 04:05, 1 December 2010 (UTC)
- For comparison, the abrupt climate change at the beginning of the Younger Dryas took place over the course of several years, as opposed to drastic climate change occurring over the course of several days in the movie. Red Act (talk) 06:23, 1 December 2010 (UTC)
- If you're in Britain at the moment, it feels like it's happening right now. Ghmyrtle (talk) 07:43, 1 December 2010 (UTC)
- Wow snow in winter. Who would have guessed? Googlemeister (talk) 16:27, 2 December 2010 (UTC)
- Snow in late autumn in southern England: actually surprising. 86.161.108.241 (talk) 17:14, 2 December 2010 (UTC)
- You mean this southern England? Googlemeister (talk) 19:43, 2 December 2010 (UTC)
- Snow in late autumn in southern England: actually surprising. 86.161.108.241 (talk) 17:14, 2 December 2010 (UTC)
- Wow snow in winter. Who would have guessed? Googlemeister (talk) 16:27, 2 December 2010 (UTC)
- If you're in Britain at the moment, it feels like it's happening right now. Ghmyrtle (talk) 07:43, 1 December 2010 (UTC)
- For comparison, the abrupt climate change at the beginning of the Younger Dryas took place over the course of several years, as opposed to drastic climate change occurring over the course of several days in the movie. Red Act (talk) 06:23, 1 December 2010 (UTC)
-
The Frozen Thames, Unknown 1677.
-
Thames Frost Fair, Thomas Wyke 1683.
-
Frost Fair of 1814, Luke Clennell 1814.
- Yes, but a bit before my time old chap ;-) [5] Alansplodge (talk) 23:46, 2 December 2010 (UTC)
- Wait, you consider a return to the conditions of the Little Ice Age unsurprising? Isn't that exactly what people are considering a surprising and potentially worrying thing? 86.161.108.241 (talk) 14:54, 3 December 2010 (UTC)
Cats and chocolate
Is it true that cats can die if they eat chocolate? Or is it just a myth? The UtahraptorTalk/Contribs 03:52, 1 December 2010 (UTC)
- Absoltely, 100% true. See Theobromine poisoning. You can get poisoned by chocolate too; its just that YOU have to eat a lot more than the cat. Whereas you, based on weight, would probably have to eat several pounds of chocolate to get sick, cats can have nasty effects from a single Hershey bar. Cats and dogs also metabolize chocolate differently, so on a per-pound basis chocolate is also much more poisonous to them than to us. --Jayron32 03:57, 1 December 2010 (UTC)
- I think a single pound of chocolate would make you pretty sick. Might not be from the theobromine. Just the same, the danger to cats and dogs is sometimes overstated a bit, I think. If you look up the LD50's by weight, they're not what you would call casual exposure.
- If I recall correctly, cats are a bit more sensitive than dogs, but tend not to be interested in chocolate, because they don't have taste receptors for sweet. I imagine they'd have to be really hungry. Dogs occasionally do get poisoned, but if the numbers in the article the last time I looked at it are accurate, they do have to eat quite a lot. --Trovatore (talk) 04:12, 1 December 2010 (UTC)
- It's probably better, however, to avoid feeding chocolate to pets. The toxicity level for theobromine is going to vary widely from pet to pet, given especially that a Chihuahua would get much sicker than a great dane eating the same chocolate bar. It's one of those things where, year, maybe your dog or cat would be fine, but it's not worth the risk. Just because someone can sprint accross a busy freeway and not get hit doesn't mean it isn't contraindicated to do so. Likewise, just because it may be possible to feed your pet chocolate and, by dumb luck, not end up with any ill effects doesn't mean its a good idea to do so. --Jayron32 05:52, 1 December 2010 (UTC)
- Oh, I wasn't even considering the possibility of actively feeding them chocolate. Why would you do that?
- I just mean that if you happen to drop the lemon creme from your box of See's and your German Shepard gets to it before you do, it's probably not worth bothering the emergency line at the vet. --Trovatore (talk) 09:58, 1 December 2010 (UTC)
- It's probably better, however, to avoid feeding chocolate to pets. The toxicity level for theobromine is going to vary widely from pet to pet, given especially that a Chihuahua would get much sicker than a great dane eating the same chocolate bar. It's one of those things where, year, maybe your dog or cat would be fine, but it's not worth the risk. Just because someone can sprint accross a busy freeway and not get hit doesn't mean it isn't contraindicated to do so. Likewise, just because it may be possible to feed your pet chocolate and, by dumb luck, not end up with any ill effects doesn't mean its a good idea to do so. --Jayron32 05:52, 1 December 2010 (UTC)
- I just want to add to this, late to the party, that different types of chocolate have different levels of risk. If you dog gets a small amount of milk chocolate, no need to freak out — the theobromine levels are low. If they get dark chocolate, be really wary, especially if it is a small dog. If baker's chocolate, call the vet. Etc.
- As a dog owner, I think the most dangerous situation is a dog accidentally getting into, say, a box of chocolates, which, depending on the dog, is not too impossible. I'm especially wary with presents at Christmastime because we have some relatives that will send us wrapped boxes of chocolate, and there's real danger that the dog would, in a moment of weakness, try to avail herself of these while we aren't home. Any package she takes an untoward interest in sniffing goes on top of the fridge until Christmas morning. ;-) --Mr.98 (talk) 13:21, 3 December 2010 (UTC)
That little black strap that depends from the backs of cars and scrapes along the road?
I'm seeing fewer of them these days (I'm in Australia) - but can anyone tell me what they're meant to be for, and what they're called?
Thanks Adambrowne666 (talk) 04:57, 1 December 2010 (UTC)
- If they are at the sides, they could be curb feelers. I suspect that backup cameras are replacing them as the high-end option to let you know how you are doing backing up.
- However, those really aren't meant to drag on the road. I can't think of anything that is, although theoretically they could use such a device to measure road friction and change shift points, etc., depending on how slippery the road is. I've not actually heard of this being done, though. One obvious problem would be that anything dragging on the road like that would quickly wear out. This could be handled by replacing the wearable portion, which just might be a cheap piece of plastic, but it would still be annoying to have to do this so often. Perhaps a system like a weed wacker could be used to automatically deploy the plastic string to the proper length from a large roll. The current traction-control system I am aware of detects slippage in the wheels and adjusts accordingly, but being able to prevent such slippage with proactive measures is certainly preferable to adjusting for it after it has happened. StuRat (talk) 05:10, 1 December 2010 (UTC)
- Aren't they antistatic ground straps or something like that ? Not sure whether there is an article about them. Sean.hoyland - talk 05:16, 1 December 2010 (UTC)
- List of auto parts has a link to ground strap but it redirects to a more general coverage of the topic. Sean.hoyland - talk 05:21, 1 December 2010 (UTC)
- Cool idea StuRat, but no, those things are grounding (earthing) straps, to avoid static shock. [6][7][8] I personally have never gotten a shock from a car (at least not that I can remember), but it's possible that in dry, slightly dusty areas it could be a bigger problem. The last link I posted seems to indicate people are buying them as snake oil. They are obviously much more important in vehicles that are carrying lots of flammables, like gas trucks. Ariel. (talk) 06:56, 1 December 2010 (UTC)
- Yes, the rubber in the neumatics isolates the car from the ground. I occasionally get static shocks when entering a car.
- These straps have a very small side issue, they can make you the target of rays. When you are isolated, the charges in the ground won't reach you during a storm. But the strap connects you to the ground, and the charges in the ground can climb up your car and attract a ray, the same way as trees and housetops. --Enric Naval (talk) 07:52, 1 December 2010 (UTC)
- I think you mean "lightning", not "rays" (or is this a national variant I'm unfamiliar with? "Lightning ray" seems to strike a chord...but given the many Manta rays and X-rays and gamma rays and orbital laser platform microwave rays, all of which can target you, it's probably better to be specific). I also think you are wrong. What keeps you safe in a car during a thunderstorm is not the isolation of the cars body from the ground (if it's raining, the water will conduct electricity, anyways), but the fact that the car is a Faraday's cage, and will conduct the electric charge from a lightning bolt into the ground on the outside of the vehicle. --Stephan Schulz (talk) 08:21, 1 December 2010 (UTC)
- Yeah, I meant lightning, it's just my bad English. Yes, the vehicle will protect you... but make sure you don't touch any metal surface. Especially, don't touch the metal surface at two different places, since part of the current might decide to travel through your body instead of travelling through the metal. The car is not a perfect faraday cage since it's not a closed metal surface (there are openings in the cage, and part of the current could travel through the inside surface of the car chassis, depending on the shape and position of the holes).
- I think you mean "lightning", not "rays" (or is this a national variant I'm unfamiliar with? "Lightning ray" seems to strike a chord...but given the many Manta rays and X-rays and gamma rays and orbital laser platform microwave rays, all of which can target you, it's probably better to be specific). I also think you are wrong. What keeps you safe in a car during a thunderstorm is not the isolation of the cars body from the ground (if it's raining, the water will conduct electricity, anyways), but the fact that the car is a Faraday's cage, and will conduct the electric charge from a lightning bolt into the ground on the outside of the vehicle. --Stephan Schulz (talk) 08:21, 1 December 2010 (UTC)
- These straps have a very small side issue, they can make you the target of rays. When you are isolated, the charges in the ground won't reach you during a storm. But the strap connects you to the ground, and the charges in the ground can climb up your car and attract a ray, the same way as trees and housetops. --Enric Naval (talk) 07:52, 1 December 2010 (UTC)
- I repeat that having a ground strap increases the chance of your car being hit by lighting. But I recognize that I don't know much the risk is increased. Maybe it's just increased by a tiny amount. I understand that car tires and not 100% rubber, they have conducting materials in their composition that make them resistors rather than insulators. A lighting has so much voltage that the little ground strap might not make much of a difference. Unfortunately, I can't find any definitive source on this topic. --Enric Naval (talk) 18:43, 1 December 2010 (UTC)
- I don't think this is true. Lighting has enough potential that it can travel through several miles of air - the tiny bit of rubber in your tires makes no difference to it whatsoever. Adding a grounding strap doesn't change anything. Ariel. (talk) 20:08, 1 December 2010 (UTC)
- Regardless of how far it has gone, most of it will still take the path of least resistance, or lightning rods would be useless. StuRat (talk) 23:14, 1 December 2010 (UTC)
- They are frequently marketed, not as anti-shock devices, but as anti-motion-sickness devices. The science behind this seems a little fuzzy to me, but the idea is that the small build up of static electricity that naturally occurs in a car contributes to the sense of motion sickness in sensitive people. By releasing this static to the ground, people who are sensitive to motion sickness are supposed to feel more comfortable. While the ones for cars look like strips of plastic or cloth, larger vehicles sometimes use chains. My wife and daughter get terribly motion sick, so we tried them. There seemed to be a benefit, but it could well be chalked up to expectations of it working than anything "real". Matt Deres (talk) 14:52, 1 December 2010 (UTC)
- Yes, I've seen them marketed as anti car-sickness devices. I think they work on the Tinkerbell principle. They certainly don't prevent static shocks when entering or alighting from cars in my experience. DuncanHill (talk) 15:29, 1 December 2010 (UTC)
- Re: static buildup: In many years of driving, I only had one car which produced a big static buildup. It was a little compact car, and I learned to touch metal on the car as I stepped onto the ground to discharge it; otherwise if I touched it later there would be an easily felt spark. This also presented an explosion hazard when fueling it, if a spark had occurred. I expect the tires were of a composition which was less conductive than typically, and had not yet gained a coating of dirt. A piece of conductive plastic, perhaps carbon fiber filled, would easily drain off such static charge, or perhaps an anti-static conductive sprays could be applied to the tires to conduct from the metal wheel to the ground. The parallel combination of the conductive path of the four tires might not be as good an insulator as some people assume, since the rubber quickly gets covered with conductive grime, especially when damp, as in a typical lightning storm. Edison (talk) 17:03, 1 December 2010 (UTC)
Thanks heaps everyone - but what are they called? Adambrowne666 (talk) 22:16, 2 December 2010 (UTC) -- actually, from googling, it looks like they're just called antistatic straps - bit disappointing - more a description than a name...
bladder-caused sleep interruption
I just spent 90 minutes, equally divided between Wikipedia and a Medical Advice Encyclopedia, trying to determine HOW LONG IT TAKES for water to become urine stored in the bladder!
NO ANSWER FROM EITHER!
The information is simple and would be extremely useful to many of us who use your service to AVOID getting lost in the thickets of hyper-information (the disease many information providers suffer from) and hypochondria.
How long before hs (hour of sleep) should an otherwise healthy adult or child avoid ingesting liquids as a simple preventative to avoid an over-full bladder demanding attention!
This is extremely useful consumer advice, and SHOULD be simply and easily found in ANY discussion of physiology, bladdders, urine, or piss (pre-13th Century use). —Preceding unsigned comment added by 63.193.182.226 (talk) 08:24, 1 December 2010 (UTC)
- Like so many simple questions this one does not have a simple answer that covers all eventualities. I have no source to point you at but my experience indicates that it can be somewhere between 30 and 45 minutes for ingested liquid to be excreted as urine in 'normal' circumstances. however there are a number of other factors that will affect this timing or the need to void urine. The age of the individual is a significant factor in determining the need for nocturnal voiding. More older people tend to have a reduced bladder capacity which is stimulated by smaller amounts of urine. A lot of food we eat contains water and this is likely to be extracted, processed and excreted over a longer time than my experience of 30 - 45 minutes. The activity of the kidneys is regulated to some degree by the individual's circadian rhythm which may reduce urine production during the night but start again at around dawn (or so). This widespread problem is not easily remedied and may be something that individuals have to accept as a consequence of ageing. And please, no-one come back to me on ageism - 'cos I am one of the aged! Richard Avery (talk) 08:51, 1 December 2010 (UTC)
- 63.193 you seem angry that the web is not up to your expectations. We are really sorry about that. I assure we will try to improve the web in order to avoid that you get angry again. --Lgriot (talk) 10:04, 1 December 2010 (UTC)
- The IP may be referring to last night's episode of QI XL in the UK, in which it was claimed that if they needed to get up early, American Indians would drink a lot of water before they went to sleep, so that they would have to get up early to urinate.--Shantavira|feed me 10:07, 1 December 2010 (UTC)
- Beer is much more efficient than water for that - but then, you can't get a good pint in America, or a good cup of tea either, so I suppose it's fair enough to make do with water. DuncanHill (talk) 15:32, 1 December 2010 (UTC)
- This is also handed down as Vietnam War lore: the person who was to take over the watch duties while a patrol was sacked out would drink a lot of water when he went to sleep, so he would wake up a couple of hours later. Also, anecdotally, parents of little bedwetters have been known to restrict the childrens' intake of fluids an hour before bedtime. Also anecdotally, an ageing male's bladder inevitably needs emptying in the middle of an 8 hour sleep period, even if there are no fluids in the hour before bedtime. Ageing females seem to do better on that count. Edison (talk) 16:53, 1 December 2010 (UTC)
- Beer is much more efficient than water for that - but then, you can't get a good pint in America, or a good cup of tea either, so I suppose it's fair enough to make do with water. DuncanHill (talk) 15:32, 1 December 2010 (UTC)
- Old men tend to have enlarged prostates, which limits bladder capacity. Also, drooling, sweating and respiration are other ways the body loses water at night, with the last two varying with temperature and humidity. StuRat (talk) 23:30, 1 December 2010 (UTC)
- Part of the difficulty with this question is that water does not go straight from the stomach to the bladder. water is absorbed into the blood stream from the intestines (at a rate governed in part by the body's need for water - it's an osmotic action). once in the bloodstream it is governed by other hormonal and chemical regulatory processes. once it passes through the kidneys and begins accumulating in the bladder, awareness of it will vary from person to person. remember that the body is mostly water - unless you drink a lot of water you are not significantly changing the quantity of water in the system, and so the body will not feel any great haste to expel it. --Ludwigs2 16:37, 1 December 2010 (UTC)
- The Reference Desks usually have a turnaround of several hours up to several days. Adjusting your expectations accordingly will reduce your frustration. --Sean 18:06, 1 December 2010 (UTC)
- I think the 90 minutes on Wikipedia and the MAE was before coming to the reference desk. Red Act (talk) 20:30, 1 December 2010 (UTC)
- There is such a thing as a Medical Advice Encyclopedia? It's the antimatter to the Wikipedia Reference Desk! Kill it with fire! Comet Tuttle (talk) 21:55, 1 December 2010 (UTC)
white poop
In an early episode of Life on Mars, Sam Tyler (shifted from 2006 to 1973) remarks, "White dog shit – that takes me back." Me too; I don't remember seeing it since 1965 (when I moved from Chicago to Pasadena). What changed? —Tamfang (talk) 09:47, 1 December 2010 (UTC)
- No idea if it's the same reason but the dog poop in my yard turns white after it dries out. I noticed the difference once we switched our dogs over to a raw chicken diet. So, maybe commercial dog food became more prevalent around 1965? Dismas|(talk) 10:01, 1 December 2010 (UTC)
- (e/c) Dog food contains much less bone meal than it used to. That used to get excreted as calcium carbonate. There are multiple discussion posts all over the place about this, such as here. Ghmyrtle (talk) 10:02, 1 December 2010 (UTC)
- I'm sure this has been asked on the RefDesks before - but I haven't been able to find the thread. Anyone else remember it? DuncanHill (talk) 15:38, 1 December 2010 (UTC)
- I've only seen a lot of white poop after a snow has cleared. I assume it's either something being leached out or something to do with the poop being preserved longer than usual. At any rate, perhaps the Chicago->Pasadena move would account for the change in frequency? Ask your friends back home to take a white shit census! --Sean 16:08, 1 December 2010 (UTC)
- My understanding is it's due to the reduction in tripe in dog diets.--DeKay01 (talk) 20:44, 1 December 2010 (UTC)
- In The London Labour and the London Poor (a factual description of the poorest people in London in the 1840s), the lowliest occupation belongs to an old lady who is a "Dog Dung Collector" or "pure finder". She made her meagre living by picking up white dog droppings and selling them to the tanneries, who used them to treat leather somehow. She'd be out of a job now! Alansplodge (talk) 23:39, 2 December 2010 (UTC)
Bismuth reaction with acid
Does bismuth or its oxide react with any acid? Chemicalinterest (talk) 14:36, 1 December 2010 (UTC)
- Yes. See the "Reactions with acids" section of this page. Red Act (talk)
- I added the data from the page to the bismuth article. --Chemicalinterest (talk) 19:05, 1 December 2010 (UTC)
Drinking seawater
In the most typical case, it would kill you. But does that hold true for any ocean? The salinity of the oceans vary, so if it kills you in the dead sea, it doesn't mean that it also kills you in the Antarctic. Quest09 (talk) 17:38, 1 December 2010 (UTC)
- We have an article about this. Drinking small amounts of seawater is not harmful, drinking large amounts can be. Exactly how much is "bad" will depend on the composition of the seawater and the person doing the drinking (including their hydration status, environment, level of exertion, any chronic health conditions, medications, etc). So, the direct answer to your question is almost certainly that any ocean's water can be harmful. A precise answer to the follow-on questions (how much of each would be) depends on many factors. -- Scray (talk) 18:06, 1 December 2010 (UTC)
- The most interesting thing about that article is the revelation that simply eating fish will probably supply all or most of the water you need. Along with the apparent fact that consuming small amounts of seawater along with fish is minimally damaging. That's assuming the water itself is germ-free, which would be another story. ←Baseball Bugs What's up, Doc? carrots→ 16:25, 2 December 2010 (UTC)
- (EC)Our Southern Ocean article, unhelpfully, does not provide information on its salinity. Ocean tells us that "Average oceanic salinity is around 35 parts per thousand (ppt) (3.5%), and nearly all seawater has a salinity in the range of 30 to 38 ppt" and elsewhere reminds us that there are localised variations, especially at river mouths and, presumably, ice melts. I think we can take it as a general rule that salinity will tend to be 3% or greater, and thus consumption is ill advised. --Tagishsimon (talk) 18:09, 1 December 2010 (UTC)
- More than ill advised, I'll say it is lethal in any situation - Dead Sea or Southern Ocean. Drinking water has a upper limit of 1,000 ppt salinity. Much less than the less salty ocean. Mr.K. (talk) 18:17, 1 December 2010 (UTC)
- Err, isn't 1,000 ppt salinity pure salt? Matt Deres (talk) 18:24, 1 December 2010 (UTC)
- Sorry, I meant 1,000 ppm instead of the typical 35,000 ppm that you normally find in seawater. Mr.K. (talk) 18:40, 1 December 2010 (UTC)
- Err, isn't 1,000 ppt salinity pure salt? Matt Deres (talk) 18:24, 1 December 2010 (UTC)
- More than ill advised, I'll say it is lethal in any situation - Dead Sea or Southern Ocean. Drinking water has a upper limit of 1,000 ppt salinity. Much less than the less salty ocean. Mr.K. (talk) 18:17, 1 December 2010 (UTC)
- Depending on your definition of "Ocean". If you include the Dead Sea (which is unusual ;-), you should also include the Baltic Sea. The Baltic surface water is 4-5 times less salty than the average ocean water, and the northernmost reaches of the Gulf of Bothnia are basically fresh. --Stephan Schulz (talk) 18:34, 1 December 2010 (UTC)
This information shows it is all the more remarkable that one group of mammals, the marine mammals, live in or on the sea, have no access to fresh water and yet they survive and have done for millions of years. Does Wikipedia have some information about how these remarkable creatures satisfy their need for fresh water in an environment that consists entirely of salt water? Dolphin (t) 11:44, 2 December 2010 (UTC)
- You should know that better than us, Dolphin.Mr.K. (talk) 16:14, 2 December 2010 (UTC)
- I was going to suggest salt glands, but it would appear from the article that marine mammals don't have these (there's no mention of them, anyway). Maybe evolution has made their kidney much more tolerant of salt than ours? --Kurt Shaped Box (talk) 11:59, 2 December 2010 (UTC)
- The problem with drinking seawater is not that it will damage our kidneys. Your kidneys won't be able to excrete it and the concentration of sodium chloride in your blood will increase to a dangerous level. Sea mammals, on the other side, have kidneys adapted to their environment. See: "In making the change from terrestrial to aquatic living, cetaceans needed a way to accommodate for the higher salinity of their environment. Unlike human kidneys, which are just two singular renules (or balls), dolphins have two kidneys with multiple renules. These renules all function as separate kidneys which help filter out the higher amount of salt content they must deal with in their daily environment." From [9].Mr.K. (talk) 16:12, 2 December 2010 (UTC)
- Our article on Sea Otters makes mention of the creatures large kidneys for the purpose of removing excess salt. Googlemeister (talk) 16:22, 2 December 2010 (UTC)
- Not sure if the articles on marine mammals mention this or not, but marine mammals generally don't drink (to the point where frequent drinking is recognized as a symptom of illnesses including kidney damage.) They get their water from eating - fish, cephalopods, other mammals, rather than from drinking salt water directly. They still likely take in some amount of seawater just by being there. 173.11.110.109 (talk) 00:55, 3 December 2010 (UTC)
- Our article on Sea Otters makes mention of the creatures large kidneys for the purpose of removing excess salt. Googlemeister (talk) 16:22, 2 December 2010 (UTC)
- The problem with drinking seawater is not that it will damage our kidneys. Your kidneys won't be able to excrete it and the concentration of sodium chloride in your blood will increase to a dangerous level. Sea mammals, on the other side, have kidneys adapted to their environment. See: "In making the change from terrestrial to aquatic living, cetaceans needed a way to accommodate for the higher salinity of their environment. Unlike human kidneys, which are just two singular renules (or balls), dolphins have two kidneys with multiple renules. These renules all function as separate kidneys which help filter out the higher amount of salt content they must deal with in their daily environment." From [9].Mr.K. (talk) 16:12, 2 December 2010 (UTC)
NASA astrobiology news
What astrobiology news from NASA await us tomorrow? --Mortense (talk) 19:02, 1 December 2010 (UTC)
- We shall see tomorrow. Before that the reference desk is unlikely to provide you with solid information. For Internet denizens' speculation, you might enjoy a Slashdot discussion on the subject. 88.112.56.9 (talk) 19:06, 1 December 2010 (UTC)
- Slashdot'ters are notoriously ignorant about astronomy subjects. --Mortense (talk) 19:16, 1 December 2010 (UTC)
- How about the official-sounding MEDIA ADVISORY : M10-167 that was posted on NASA's homepage, announcing "NASA will hold a news conference at 2 p.m. EST on Thursday, Dec. 2, to discuss an astrobiology finding that will impact the search for evidence of extraterrestrial life." As has been pointed out, we will know tomorrow after they hold their conference. Nimur (talk) 19:21, 1 December 2010 (UTC)
- Oddly, I'm pretty sure I do in fact know the answer, since my girlfriend accompanied Felisa Wolfe-Simon on her most recent trip to Mono Lake. Without giving anything much away, you can get an idea about the topic area by looking up Dr. Wolfe-Simon's prior work. Dragons flight (talk) 19:21, 1 December 2010 (UTC)
- Feel free to give at least a little away. Where would these arsenic based life forms most likely be found outside earth? Beach drifter (talk) 20:12, 1 December 2010 (UTC)
- I don't think that they'll have located anywhere in particular that it's more likely to find life. Nobody at present is really sure just how likely abiogenisis is and there's a school of thought that maintains that it's extremely unlikely. If they really have found a new organism that they can place right at the root of the phylogenetic tree it'll mean that life may have started twice, independently, here on Earth. That would make one of the inputs to the Drake equation slightly less of a guess. Blakk and ekka 22:15, 1 December 2010 (UTC)
- It could be anything on a scale from interesting extremophile to second Abiogenesis. I saw Paul Davies talking about this a couple of times earlier this year and, if it's as promising as he seemed to think it was, it'll be very interesting indeed. 86.26.8.192 (talk) 21:58, 1 December 2010 (UTC)(edit Blakk and ekka 22:01, 1 December 2010 (UTC))
- Feel free to give at least a little away. Where would these arsenic based life forms most likely be found outside earth? Beach drifter (talk) 20:12, 1 December 2010 (UTC)
- Oddly, I'm pretty sure I do in fact know the answer, since my girlfriend accompanied Felisa Wolfe-Simon on her most recent trip to Mono Lake. Without giving anything much away, you can get an idea about the topic area by looking up Dr. Wolfe-Simon's prior work. Dragons flight (talk) 19:21, 1 December 2010 (UTC)
- The news shall be: We have found such-and-such a chemical at such-and-such a location up in the outer space area above us in the sky. Comet Tuttle (talk) 21:54, 1 December 2010 (UTC)
Funny. I was asked to look at that astrobiology news and if we should aim for certain organometalics for the MOMA instrument on Exomars. The arsenic life forms (producing C-As bonds) I find them in the ocean, for example lobsters, the acumulate arsenobetaine in large quantities. The other group is mold they get ride of arsenic by converting it to trimethyarsin and then they let it go with the wind. So even here arsenic is a notable part of biochemistry.--Stone (talk) 22:14, 1 December 2010 (UTC)
- Today some speculations came up that a arsenic based DNA was found. This would be one of the big stories every biologist would like to be involved.--Stone (talk) 16:54, 2 December 2010 (UTC)
Heres the News release. It is indeed a bacteria that can incorperate arsenic instead of phosphorus in itself. Unfortunately, it does not indicate a second abiogenisis; the bacteria in question, GFAJ-1, has merely evolved to tolerate and use arsenic (that's still pretty damn cool, though). Buddy431 (talk) 20:02, 2 December 2010 (UTC)
Synapse structure
What structurally maintains the proper synaptic cleft of the presynaptic and postsynaptic neurons of a synapse? If I simply lay two threads floating head to head in a liquid, unless there's something holding them in place, they're pretty much guaranteed to drift apart as soon as I move the system. 20.137.18.50 (talk) 19:13, 1 December 2010 (UTC)
- There are cell adhesion molecules such as neuroligin that bind pre-synaptic and post-synaptic membranes; see Synaptogenesis#Signalling. Also, the entire synaptic cleft is encapsulated by glial cells; see Synaptogenesis#Central Nervous System Synapse Formation. Red Act (talk) 20:24, 1 December 2010 (UTC)
- (ec)The article you linked gives a little info. "Both the presynaptic and postsynaptic sites contain extensive arrays of molecular machinery that link the two membranes together". The article specifically about chemical synapses (the usual kind discussed in schools, with chemical neurotransmitters, etc.) does not have any more info about this detail--would be great if someone could find it. The article about electrical synapses talks about the connexon channels and the diagrams suggest an interaction between the E1 and E2 domains of the connexin proteins. That last article has a section detailing what's currently known about how they link together. DMacks (talk) 20:28, 1 December 2010 (UTC)
- Thanks Red Act! Could you add some notes to the synapse article about it? It's definitely important to the structure itself, not just the biological formation of them. DMacks (talk) 20:29, 1 December 2010 (UTC)
- The chemical synapse article would be the place to add the information -- the synapse article is basically a disambig page, because the two types of synapses are so different structurally and functionally. Unfortunately this is an aspect of neuroscience I know very little about. Looie496 (talk) 21:00, 1 December 2010 (UTC)
- There is a diagrammatic representation here on page 127. The chapter also goes into more detail.--Aspro (talk) 21:14, 1 December 2010 (UTC)
- The chemical synapse article would be the place to add the information -- the synapse article is basically a disambig page, because the two types of synapses are so different structurally and functionally. Unfortunately this is an aspect of neuroscience I know very little about. Looie496 (talk) 21:00, 1 December 2010 (UTC)
- Thanks Red Act! Could you add some notes to the synapse article about it? It's definitely important to the structure itself, not just the biological formation of them. DMacks (talk) 20:29, 1 December 2010 (UTC)
Christmas lights
My outdoor lights I have just hung says clearly not to connect more than three strands together or it will exceed their rating. Of course I have eight connected end to end on one side of the house and four on the other. Surely I am not the only one to go well over the limit stated on the box? Is it most likely the light stands would fail first or the outlet? Each plug on the strands has a fuse on it so would these go out first? Anyone have any solutions for wiring these lights without running extension cords from all over the place? Thanks. Beach drifter (talk) 20:07, 1 December 2010 (UTC)
- If the lights are connected in parallel, then the expected failure mode is for a fuse or circuit breaker to blow. The secondary failure mode is for something somewhere to get very hot, so be careful. Looie496 (talk) 20:55, 1 December 2010 (UTC)
- (ec)We would need more info, specifically the wire size, and the power consumed (watts) from each strand. Worst case scenario is a fire by overheating the wires that make up the strands. Hopefully the fuse would blow first, but it's not guaranteed. Can you link to the product if you don't know the specs? You can buy LED lights - they use a LOT less power. Ariel. (talk) 20:57, 1 December 2010 (UTC)
- The product is rated at 61.2 watts/.51 amps, connected end to end for a maximum of 210 watts/1.75 amps. Beach drifter (talk) 21:01, 1 December 2010 (UTC)
If each plug is fused is the a UK 3 pin plug 240v. If so you'll likely have a 2 amp fuse and that is because the lights have 2 amp wire (why waist money on a heavier gauge just for little dinky lights). No, not a good idea.Hope you are also using a isolation transformer or an earth leakage trip to guard against finding electrocuted reindeer in the garden.--Aspro (talk) 21:29, 1 December 2010 (UTC)- Good point about the deer, we get them in the yard more frequently in the winter. Beach drifter (talk) 21:36, 1 December 2010 (UTC)
- I don't really understand what you mean. 61.2 watts each, maximum of 4 does not equal 210 watts. Or do you mean each one is 210 watts? (So x 4 = 840 watts.) Also, what size are the wires? Ariel. (talk) 22:40, 1 December 2010 (UTC)
- The product is rated at 61.2 watts/.51 amps, connected end to end for a maximum of 210 watts/1.75 amps. Beach drifter (talk) 21:01, 1 December 2010 (UTC)
- (ec)We would need more info, specifically the wire size, and the power consumed (watts) from each strand. Worst case scenario is a fire by overheating the wires that make up the strands. Hopefully the fuse would blow first, but it's not guaranteed. Can you link to the product if you don't know the specs? You can buy LED lights - they use a LOT less power. Ariel. (talk) 20:57, 1 December 2010 (UTC)
- There are several different ways to answer this.
- Good engineering practice -- which is sought for, and generally achieved, in the design of electric power systems and appliances -- is to design things so that they are inherently safe, not to depend on the user to keep them safe. As you suggest, you're certainly not the first person to have imagined that you can "probably get away with" stringing together eight strands of lights when the directions say there's a max of three.
- With that said, though, Christmas lights were once a distinct exception to the above. A strand of incandescent lights consumes a significant amount of power. If they're strung in series (which is the common arrangement if you're, say, encircling your house), the total current drawn by all strands must pass through the plug and wires of the strand that's closest to the outlet. If you connect together arbitrarily many strands, sooner or later you can almost certainly get to the point where you've exceeded the current-carrying capacity of the wires of the first strand, but not exceeded the rating of the fuse or circuit breaker protecting the outlet you've got the whole mess plugged into.
- With that said, though, the "Christmas light loophole" has, as near as I can tell, been closed. There are little fuses in the plugs, now, and these presumably protect the plugs and wiring from having too many series-connected strands tacked on downstream.
- With that said, though, it's arguably good engineering practice to adopt a "belt and suspenders" approach, to try to be safe on your own, letting the protective devices like fuses and circuit breakers serve as a backup, rather than depending on them. So if the instructions say "no more than three", and if you really want to Follow The Rules, it would certainly be a Good Idea to connect no more than three. (But with that said, though, the no-more-than-three recommendation is sure to include a safety factor, whether or not it's enforced by a fuse. [But what's the safety factor? And is it a good idea to make use of it?])
- With all of that said, though, the real question is, for multiple strands of Christmas lights constructed with wire of a certain gauge, all connected in series, plugged in to an outlet protected by a fuse or circuit breaker with a certain rating, how likely are you to actually start a fire? Let's say the wire is 18 gauge, and the circuit is protected at 20 amps. That 20 amp circuit is wired (if to code) using 12 gauge wire, which has twice the diameter and therefore four times the current-carrying capacity of 18 gauge. In other words, you can run 20 amps through 12 gauge wire all day long without it getting anything like too hot. By that token, you shouldn't run more than 5 amps through the 18 gauge wire. If you string together enough light strands to draw (say) 19 amps, you wouldn't blow the 20 amp circuit, but the 18 gauge wire would certainly get warm, if not hot. The question, then, is, would a nearly 4x overload cause the wire to heat up so much that the insulation would melt off or catch fire? And the answer is... I don't know. But these are definitely the kinds of numbers we're talking about, in that I can't imagine a string of Christmas lights wired with anything smaller than 18 gauge wire, and the outlet you plug it/them into is never (in the U.S., anyway) going to be fused at more than 20 amps. —Steve Summit (talk) 03:07, 2 December 2010 (UTC)
Dinosaur Combs and Wattles
Given than birds are descendants of dinosaurs, have there been anything found in the fossil record that tell us whether dinosaurs also had structures such as combs or wattles like their chicken or turkey descendants? Jeanpetr (talk) 20:50, 1 December 2010 (UTC)
- Fossils only form under some very rare and special conditions. For flesh to fossilize it takes even rarer and more special conditions. While there have been billions of fossils found I believe there are only a tiny fraction have anything that can be recognized as flesh. However there are at least some scientists who believe dinosaurs may have had soft skin folds similar to combs and wattles. Vespine (talk) 21:50, 1 December 2010 (UTC)
Is this for reals?
http://www.youtube.com/watch?v=6QasA6NQXXQ&feature=related
Hoax? —Preceding unsigned comment added by 114.173.217.17 (talk) 21:04, 1 December 2010 (UTC)
- No Hoax. Our Snakebite article even mentions this: A snake's detached head can immediately act by reflex and potentially bite. The induced bite can be just as severe as that of a live snake. Dead snakes are also incapable of regulating the venom they inject, so a bite from a dead snake can often contain large amounts of venom. I've heard that rattlesnakes are particularly notorious for this, there's several news stories to back this up. Vespine (talk) 02:50, 2 December 2010 (UTC)
- About how long would it take for that reflex capability to dissipate? ←Baseball Bugs What's up, Doc? carrots→ 16:27, 2 December 2010 (UTC)
Circuits with LEDs
I'd like to play around with LEDs, and I'd like to understand a bit what I'm doing. In school, and at home, I did loads of circuits with little incandescent bulbs, and I know the basics of circuits with batteries, resistors, incandescent bulbs. I can calculate the voltages/currents/resistance of components in idealised parallel and series circuits. But we never did anything with diodes, apart from look at a graph of how voltage varied with current to get an idea of them being oneway (and make a circuitboard in Design and Technology without any explanation of the theory or how it worked, which wound me up). I have an idea that, apart from needed to hook them up with positive and negative the right way round, you have to be careful about the voltage across them, so you need to add a resistor of a particular value to get the right voltage.
Could someone recommend some easily-available write-up of relevant theory, ideally from a practical angle, to ease me into this area? If I get the voltage on an LED too high, will it blow up, fail early, or just not work? 86.161.108.241 (talk) 22:56, 1 December 2010 (UTC)
- I have failed LEDs in all of the above methods. Connecting a LED directly to a 9v battery is a quick and easy way to blow them up. There are loads of tutorials online, just google LED totorial; here's a couple. Just because it's a chance to blow my own trumpet, here's my LED project I spent about 18 months on. Vespine (talk) 23:33, 1 December 2010 (UTC)
- If LEDs are so sensitive to votages then why are they used in Opto-isolators? Hcobb (talk) 23:48, 1 December 2010 (UTC)
- - because it is preferable to blow up a cheap LED than the expensive chips that it isolates from inappropriate voltages. Dbfirs 07:56, 2 December 2010 (UTC)
- Thanks Vespine: it's hard to identify a good tutorial when you're new to something. I'd thought I'd need to carry out really careful iterative calculations with logs, based on what I was seeing in our articles, but that looks fairly easy. And your project fills me with confidence in your ability to judge the tutorial! Wow, that's cool. Looks like I'm buying components and solder tomorrow! 86.161.108.241 (talk) 23:54, 1 December 2010 (UTC)
- (ec) I can direct you to some of the theory, though it might be a little short on the "practical angle" aspect. The electrical properties of semiconductors can be explained using band theory (note that semiconductors are crystals). (It may or may not be useful to read up a little on Maxwell-Boltzmann statistics, on how and why it breaks down when applied to fermions, and, subsequently, on Fermi statistics.) Once you understand semiconductors, you can move on to diodes, and then to LEDs. --superioridad (discusión) 00:00, 2 December 2010 (UTC)
- My tip is just dive straight in, you'll learn heaps by just trying things out, you can get LEDs by the hundreds literally for a few dollars off ebay. Find a DC power pack and learn how to make a simple power supply using a 7805, or a variable one if you are adventurous (LM317). I'd also recommend a breadboard, it makes things a lot easier. The components you need are peanuts from places like futurlec.com , I don't usually shill but that place is really cheap and I've bought lots of stuff from them without any problems. Even if you visit a local shop it shouldn't be too expensive to get started. Vespine (talk) 00:10, 2 December 2010 (UTC)
- Also might be worth mentioning, don't be tempted to start learning on the high power LEDs like CREE or Luxoen, they're a considerably different kettle of fish. Just start with a bunch of the cheapest LEDs you can find. Vespine (talk) 00:13, 2 December 2010 (UTC)
- My tip is just dive straight in, you'll learn heaps by just trying things out, you can get LEDs by the hundreds literally for a few dollars off ebay. Find a DC power pack and learn how to make a simple power supply using a 7805, or a variable one if you are adventurous (LM317). I'd also recommend a breadboard, it makes things a lot easier. The components you need are peanuts from places like futurlec.com , I don't usually shill but that place is really cheap and I've bought lots of stuff from them without any problems. Even if you visit a local shop it shouldn't be too expensive to get started. Vespine (talk) 00:10, 2 December 2010 (UTC)
- (edit conflict) We have a practical article: LED circuit. Basically: if you overdrive an LED, you'll cook it (when I did this, it just glowed quite brightly and rapidly dimmed into nothingness). You can overdrive it in either direction: backwards, it's a little sturdier, but also useless.
- The math: P=IV, of which IV0 is light (V0 is approximately the minimum voltage to get light) and the rest heat, so is the heat your LED has to dissipate. When V increases beyond V0, both of those factors increase rapidly (I increases exponentially in standard diode models). So the heating rate of your diode is very sensitive to voltage; there's a tiny range of voltages between "doesn't light" and "cooks". Hitting that target is really hard with just a voltage source (battery), so don't be tempted to say "Hey, these are 3V LED, says so on the box, so let me just put three in series on a 9V battery.". The basic trick is to add a resistor in series; then the voltage across the LED can't get high, because then the current would be large, but then the voltage drop across the resistor would exceed that of the source. See the graphical analysis: even if you move the bottom-right point (which represents the battery voltage) around, the intersection doesn't move much.
- The article depicts this and shows how to calculate the appropriate resistance (always round up, of course, with real resistors). You can safely stack LEDs (even of different colors) in series with one resistor: you'll just be constrained by the lowest current rating, of course. It's not usually recommended to connect LEDs in parallel: it works, but tends to generate uneven lighting and shorter lifetimes. --Tardis (talk) 00:14, 2 December 2010 (UTC)
December 2
Scientific Child Rearing
Humans have been raising children since basically the dawn of time, so presumably we do an okay job of it on average. On the other hand, if you talk to ten different people, you are likely to get ten different opinions about how to deal with kids. Some people believe in being very strict, physical (e.g. spanking), or distant. Others will try to coddle their children and protect them from everything. Some parents assign lots of chores to their kids, and other parents do all the cleaning and work themselves. Some parents want to know everything about their kids lives and others leave them alone.
I could go on, but you get the idea. My question is this: Is there any objective evidence that certain parenting styles are more effective than others at ensuring that children grow up to be happy and successful adults? For example, do the kids of strict parents earn more over their lifetime? Do the kids of gentler parents have fewer (or more) psychological problems in adulthood?
I'm looking for references to scientific studies and other factual conclusions, rather than just personal opinion. Dragons flight (talk) 00:24, 2 December 2010 (UTC)
- I think the problem is that I doubt you could even satisfactorily define happy and successful. Vespine (talk) 02:18, 2 December 2010 (UTC)
- There are lots and lots and lots of studies of this sort. I don't know what the larger synthetic conclusions are, but surely there are some by this point, even if they are contested (and they certainly will be). --Mr.98 (talk) 02:50, 2 December 2010 (UTC)
- Actually, that's pretty good, it gave me the idea to put meta analysis and meta analytic into the search field after "parenting style" and that comes up with some pretty interesting sounding results. don't have the time to go through any now, but i've bookmarked it. Vespine (talk) 02:59, 2 December 2010 (UTC)
- A couple thoughts:
- 1) Different kids likely require different parenting styles. For example, some would benefit from permissive parents who let them do as they please, while other kids would get into serious trouble with such parents. Identifying which type of kids you have an adjusting your parenting style (sometimes for each sibling), may therefore be necessary.
- 2) Parents tend to think they did a good job if their kids turn out like them. So, parents who value education will think they did a good job if they end up with educated children, while parents who value athletics will think they did a good job if they end up with athletic kids. StuRat (talk) 21:50, 2 December 2010 (UTC)
The Marshmallow Trick
By many accounts, marshmallows, inserted anally, act as a laxative. What causes this effect? -mattbuck (Talk) 00:53, 2 December 2010 (UTC)
- That's not how I learned to make smores. :-) StuRat (talk) 00:10, 3 December 2010 (UTC)
- There are herbal laxatives (to be taken orally), such as "Easy Mover", that contain marshmallow (Althaea officinalis) extract. I don't know whether the marshmallow extract is the active ingredient, nor how it works, though our laxative article provides plenty of plant-based examples. Searching Pubmed did not provide any helpful leads, and I could not easily find reliable sources for the use of marshmallow rectally. -- Scray (talk) 01:36, 2 December 2010 (UTC)
- But the modern marshmallow confection no longer actually uses the marshmallow plant (althaea officinalis) as an ingredient. Red Act (talk) 01:49, 2 December 2010 (UTC)
- Indeed, I was adding that as an edit when I encountered an edit conflict ;-) -- Scray (talk) 01:56, 2 December 2010 (UTC)
- Anyone else got an idea? -mattbuck (Talk) 03:25, 4 December 2010 (UTC)
- I think it's the sugar. A corn syrup enema would probably work, too. StuRat (talk) 19:31, 4 December 2010 (UTC)
Chemistry Laboratory technique
I'm looking for the name of a chemistry laboratory technique in which you "scratch" at the walls of a beaker to form a polymer. —Preceding unsigned comment added by David255 (talk • contribs) 00:57, 2 December 2010 (UTC)
- Assuming you're forming a crystalline solid, and not a covalent polymer, I've always called the technique "scratching"! You basically form new nucleation sites on the inside surface of the beaker. Trituration (beating it into a solid) is similar in thermodynamic terms, but you usually work with much less liquid than for scratching. Physchim62 (talk) 01:58, 2 December 2010 (UTC)
- Trituration is the term. Thanks! —Preceding unsigned comment added by David255 (talk • contribs) 02:33, 2 December 2010 (UTC)
Question from ANI
I don't know why ANI is trying to figure it out:[10], but someone there would like to know if Birds are Dinosaurs? 108.121.139.247 (talk) 01:30, 2 December 2010 (UTC)
- That's me. See below. ←Baseball Bugs What's up, Doc? carrots→ 01:47, 2 December 2010 (UTC)
Birds = Dinosaurs?
OK, I would like to hear some expert opinions on this. According to one of the articles, birds are "an extant clade of dinosaurs". I understand birds are considered to be descended from dinosaurs, but is that the same thing as saying "birds are dinosaurs"? I don't think so, and have said as much at List of common misconceptions, but I'm no expert in this area. Thanks for any help you can provide. ←Baseball Bugs What's up, Doc? carrots→ 01:47, 2 December 2010 (UTC)
- See here Origin of birds and Origin of birds#Features linking birds and dinosaurs. Heiro 01:51, 2 December 2010 (UTC)
- Our Dinosaur article says: Consequently, in modern classification systems, birds are considered a type of dinosaur — the only group of which that survives until the present day. I rather randomly examined the October 3 edit from the history and verified the sentence (as ungrammatical as it looks) has been in the article at least since then, so it isn't a recent addition to confound the discussion mentioned at AN/I. Comet Tuttle (talk) 01:52, 2 December 2010 (UTC)
- The Dinosaur intro goes on to talk about dinosaurs in the present tense, because of birds; but then later says: From the point of view of cladistics, birds are dinosaurs, but in ordinary speech the word "dinosaur" does not include birds. Additionally, referring to dinosaurs that are not birds as "non-avian dinosaurs" is cumbersome. For clarity, this article will use "dinosaur" as a synonym for "non-avian dinosaur". The term "non-avian dinosaur" will be used for emphasis as needed. Comet Tuttle (talk) 01:55, 2 December 2010 (UTC)
- The origin of birds article begins by saying "The origin of birds is a contentious and central topic within evolutionary biology." It goes on to say that "most" scientists, etc., etc., which in my opinion is sufficient to keep the flat-out contention that "birds are dinosaurs" out of the misconceptions article. ←Baseball Bugs What's up, Doc? carrots→ 01:58, 2 December 2010 (UTC)
- (edit conflict) If one defines "dinosaurs" as members of superorder dinosauria (in class reptilia) and "birds" as members of class aves, then "birds" are not "dinosaurs". Note that this is a taxonomic argument (i.e. based on how we have historically assigned words), which is different from a cladistic argument. A clade includes all of an organism's descendents, even if they aren't in the same taxanomic groups. The evidence is quite good that birds are in the dinosaur clade, even though they aren't in the superorder dinosauria. Personally, I would agree that "birds are not dinosaurs", even though "birds are descended from dinosaurs". In other words, I think the linguistic / taxanomic arguments are more relevant in this case. Dragons flight (talk) 02:01, 2 December 2010 (UTC)
- Similarly, humans are not fish, bacteria, or rodents, even though humans are almost certainly descended from all of these. Dragons flight (talk) 02:15, 2 December 2010 (UTC)
- I hate to nit-pick, but that's not exactly correct. Humans, fish, bacteria, and rodents all share a VERY distant common ancestor that was neither human, fish, bacteria, or rodent but had descendents that evolved into those four very different groups of organisms. Evolution is confusing enough to people without muddying the waters like that... --- Medical geneticist (talk) 14:35, 2 December 2010 (UTC)
- I hate to nit-pick your nit-pick, but didn't our ancestry spend quite a bit of time as fish, most famously as Tiktaalik or other sarcopterygii? --Sean 19:38, 2 December 2010 (UTC)
- I hate to nit-pick, but that's not exactly correct. Humans, fish, bacteria, and rodents all share a VERY distant common ancestor that was neither human, fish, bacteria, or rodent but had descendents that evolved into those four very different groups of organisms. Evolution is confusing enough to people without muddying the waters like that... --- Medical geneticist (talk) 14:35, 2 December 2010 (UTC)
- Precisely. Here's the issue: The misconceptions list states to contrary to popular misconception (e.g. in The Flintstones, B.C., Alley Oop, etc.) humans and dinosaurs did not co-exist. The editor called TheThomas added the statement that birds are dinosaurs, which contradicts the alleged misconception. The question is how to resolve it. Seems to me the real "misconception" is that humans interacted with "classic" dinosaur species depicted in those cartoons, e.g. brontosaurus, t-rex, etc. ←Baseball Bugs What's up, Doc? carrots→ 02:22, 2 December 2010 (UTC)
- If you're just worried about the practical problem, how about saying "In fact, most dinosaurs died around 65 million years ago after the Chicxulub event, whereas the earliest Homo genus (humans) evolved between 2.3 and 2.4 million years ago. A few dinosaurs survived the Chicxulub event, and we call their descendents birds." Physchim62 (talk) 02:35, 2 December 2010 (UTC)
- It isn't really correct to say that a taxonomic argument is different from a cladistics argument. Different biological taxonomy systems exist; see Biological classification. Linnaean taxonomy has been around for close to 300 years, and is easily still the most widely used system, but the more modern cladistics is also a branch of taxonomy; see Phylogenetic taxonomy. According to Linnaean taxonomy, birds are not dinosaurs, since aves and reptilia are different classes. According to cladistics, birds are dinosaurs, because aves is a subclade of dinosauria (see the "Scientific classification" panel of Avialae). Neither one is "correct" or "incorrect"; they're just different systems, each with their own advantages and disadvantages; see Cladistics#Summary of advantages of phylogenetic nomenclature and Cladistics#Summary of criticisms of phylogenetic nomenclature. Red Act (talk) 03:46, 2 December 2010 (UTC)
- Red Act has the most important thing to remember here: These are all human-created classification systems. Hypothetically, we could trace the ancestry of all life back to the first self-replicating molecule, and then move forward from there, creating a branching tree of life which includes every individual living thing to ever live; including me, my neighbors cat, and one of the little bacteria in my colon. How we classify those trillions and trillions of individual living things, how we group them, is ultimately done for our own convenience, and isn't indicative of anything more than that. We're pretty sure that, if you take that robin in my front yard, and go backwards through its parents and back and back and back, you eventually get to a dinosaur of some kind. Whether that means that the birds are dinosaurs or they are descendend from dinosaurs is a minor, and mostly moot issue. We use whatever definition is most convenient or useful. --Jayron32 04:05, 2 December 2010 (UTC)
- (edit conflict with Dragons flight) I will second this. This question is not a science question, but rather a question of linguistics. There are two different (main) ways to classify organisms. Under one of them, birds are a part of the group that also includes dinosaurs. Under another, they do not. A Cladist would say, without any irony, that there is no such thing as a "reptile". There are Sauropsids, which include almost all of what are considered reptiles under the Linnaean system (including dinosaurs, but excluding a few, mostly extinct, "mammal like reptiles"), and also include birds. Up a level, there are Amniotes, including all creatures considered to be reptiles, as well as mammals and birds. Questions like this really highlight a flaw in the traditional Linnaean taxonomy: it's easy enough to define when creatures have evolved sufficiently to form a new group, but at what point does a creature cease to be a member of a group? Why don't we consider birds to be reptiles? Is it the feathers, the wings? Birds still have many of the traits we assign to reptiles: an Amniotic egg, and scales. To be fair, even mammals are still an awful lot like reptiles. We've lost our scales, and we regulate our own body temperature, but we've still got the important amniotic egg, as well as the older backbone and 4 legs. Buddy431 (talk) 04:28, 2 December 2010 (UTC)
- Of course, at that level of precision, it's no longer a "tree" of life, strictly speaking. It's a directed acyclic graph. Now that I think about it, the usual (if not as precise as it might first appear) definition of species, in terms of being able to interbreed in such a way that the descendants breed true, may be specifically designed to allow the use of trees rather than DAGs whenever you look at the species level or coarser. --Trovatore (talk) 04:12, 2 December 2010 (UTC)
- Red Act has the most important thing to remember here: These are all human-created classification systems. Hypothetically, we could trace the ancestry of all life back to the first self-replicating molecule, and then move forward from there, creating a branching tree of life which includes every individual living thing to ever live; including me, my neighbors cat, and one of the little bacteria in my colon. How we classify those trillions and trillions of individual living things, how we group them, is ultimately done for our own convenience, and isn't indicative of anything more than that. We're pretty sure that, if you take that robin in my front yard, and go backwards through its parents and back and back and back, you eventually get to a dinosaur of some kind. Whether that means that the birds are dinosaurs or they are descendend from dinosaurs is a minor, and mostly moot issue. We use whatever definition is most convenient or useful. --Jayron32 04:05, 2 December 2010 (UTC)
- Similarly, humans are not fish, bacteria, or rodents, even though humans are almost certainly descended from all of these. Dragons flight (talk) 02:15, 2 December 2010 (UTC)
- I would tend to quibble that "cladistics" is mostly an organizing principle and not really a taxonomy, since cladistics is about specifying relationships and is only rarely used to specify new names for things beyond "the clade of X". You could even accept cladistics as a starting point and define multiple different types of taxonomies on top of the relationship tree it generates. All quibbles aside though, I understand your point. That said, I don't think even strident cladists would want to embrace a system where all descendants of X were given the same name as X. It isn't conducive to either common or scientific communication to have a nomeclature system that allows for humans to also be called rats, fish, and bacteria. For the same reason, I would tend to think that saying "birds are dinosaurs" actually makes communication more opaque rather than less, and should be disfavored. That's my opinion anyway. Dragons flight (talk) 04:18, 2 December 2010 (UTC)
- Birds are more closely related to dinosaurs then anything else alive today, including crocodiles; the "next" most closely related species. A rough analogy might be that birds and dinosaurs are to crocodiles like what humans and chimps are to mice. There are very few major morphological differences between dinosaurs and birds, funnily enough a long tail is one of them, which is also a difference between humans and chimps. Vespine (talk) 04:51, 2 December 2010 (UTC)
- What humans do you know that have long tails? Cuz I've never met one... Do you have a long tail? Weird. --Jayron32 04:59, 2 December 2010 (UTC)
- You know, all those chimps with tails. *face palm*... i was thinking monkeys when i wrote that.... I work in I.T., forgive me... lol. Vespine (talk) 05:21, 2 December 2010 (UTC)
- What humans do you know that have long tails? Cuz I've never met one... Do you have a long tail? Weird. --Jayron32 04:59, 2 December 2010 (UTC)
- Birds are more closely related to dinosaurs then anything else alive today, including crocodiles; the "next" most closely related species. A rough analogy might be that birds and dinosaurs are to crocodiles like what humans and chimps are to mice. There are very few major morphological differences between dinosaurs and birds, funnily enough a long tail is one of them, which is also a difference between humans and chimps. Vespine (talk) 04:51, 2 December 2010 (UTC)
- I would tend to quibble that "cladistics" is mostly an organizing principle and not really a taxonomy, since cladistics is about specifying relationships and is only rarely used to specify new names for things beyond "the clade of X". You could even accept cladistics as a starting point and define multiple different types of taxonomies on top of the relationship tree it generates. All quibbles aside though, I understand your point. That said, I don't think even strident cladists would want to embrace a system where all descendants of X were given the same name as X. It isn't conducive to either common or scientific communication to have a nomeclature system that allows for humans to also be called rats, fish, and bacteria. For the same reason, I would tend to think that saying "birds are dinosaurs" actually makes communication more opaque rather than less, and should be disfavored. That's my opinion anyway. Dragons flight (talk) 04:18, 2 December 2010 (UTC)
clade n.[11] A group of animals or other organisms derived from a common ancestor species. The clade Dinosauria includes all dinosaurs as well as birds, which are descended from the dinosaurs. I think the linguistic argument that has arisen would be avoided if the definition were rephrased: clade n. A grouping of animals... Cuddlyable3 (talk) 10:34, 2 December 2010 (UTC) updated
- Birds are dinosaurs in the same way that humans are monkeys. Wnt (talk) 11:41, 2 December 2010 (UTC)
- No, birds are dinosaurs in the same sense that humans are primates. Matt Deres (talk) 14:52, 2 December 2010 (UTC)
- The issue seems to center on how broadly the term "dinosaur" is used or perceived. It looks like we've got a misconception within a misconception. The average citizen has been told over and over that "dinosaurs went extinct 65 million years ago." That statement appears to be an oversimplification of the situation. When people think of "dinosaurs", and of the fantasy of early hominids interacting with them, they think of T-rex and Brontosaurus and like that; not birds. ←Baseball Bugs What's up, Doc? carrots→ 15:04, 2 December 2010 (UTC)
- The word "dinosaur" was coined to describe ancient very large animals discovered as fossils. Birds are not "terrible lizards" - they are birds. The later use of the word "dinosaur" by scientists does not alter the fact that the word is in practice used, by most people most of the time, in a sense very close to that originally intended. Ghmyrtle (talk) 15:14, 2 December 2010 (UTC)
- Good point. So perhaps the root issue of the misconception-within-the-misconception is a dichotomy between what the public thinks of as dinosaurs vs. what the scientists think of as dinosaurs. That opens another can of worms. ←Baseball Bugs What's up, Doc? carrots→ 15:20, 2 December 2010 (UTC)
- And to further muddy the waters, according to Mammal our own mammalian ancestors were indeed around during the dinosaur age. ←Baseball Bugs What's up, Doc? carrots→ 15:23, 2 December 2010 (UTC)
- Perhaps, but homo sapiens weren't. Birds were actually around during the late cretaceous as well (though theories exist they evolved twice etc.), so if birds aren't dinosaurs then all the dinosaurs did go extinct at KT. Chipmunkdavis (talk) 16:34, 2 December 2010 (UTC)
- And to further muddy the waters, according to Mammal our own mammalian ancestors were indeed around during the dinosaur age. ←Baseball Bugs What's up, Doc? carrots→ 15:23, 2 December 2010 (UTC)
- Trying to factor in what the average citizen thinks is a little pointless. The average citizen thinks that pterosaurs were dinosaurs. The average citizen thinks that ichthyosaurs were dinosaurs. The average citizen thinks a lot of things that are outdated, inaccurate, unbalanced, or just plain crazy. Matt Deres (talk) 17:23, 2 December 2010 (UTC)
- But ... Until recently* the word "dinosaur" had no scientific definition! It was a word entirely for average citizens. Until recently, some sources would include pterosaurs and/or ichthyosaurs and others wouldn't and neither view was more "correct" than the other. Sure, most sources agreed that anything from Saurischia or Ornithischia could be called a dinosaur, but other stuff from that time period would also be included in many definitions. It didn't help that Saurischia and Ornithischia were not thought (at the time) to be closely related, so the whole thing was considered to be too arbitrary and contrived for formal use.
- Even definitions that discounted pterosaurs or ichthyosaurs often wouldn't do so in a satisfying way, resorting to even more arbitrary qualifiers like "ground based" or "non-flying".
- Later when it was realized that Saurishcia and Ornithischia were closely related they were able to come up with an actual scientific definition of "dinosaur" that included most of the animals everyone "knew" were dinosaurs.
- So, don't criticize too harshly people still using the informal, layman's definition of the term. The layman's version came long before the scientific version.
- * The 90s still count as "recently", right?
- APL (talk) 17:58, 2 December 2010 (UTC)
- I hope so. :( Keep in mind this has to do with "common misconceptions". Obviously, paleontologists are going to know the details of the current theories. The general public is not necessarily so well informed. The goal here is to try to come up with a better way to deal with the "misconception" that humans and dinosaurs interacted. A major part of that is defining just what a "dinosaur" actually is. ←Baseball Bugs What's up, Doc? carrots→ 18:02, 2 December 2010 (UTC)
- Good point. So perhaps the root issue of the misconception-within-the-misconception is a dichotomy between what the public thinks of as dinosaurs vs. what the scientists think of as dinosaurs. That opens another can of worms. ←Baseball Bugs What's up, Doc? carrots→ 15:20, 2 December 2010 (UTC)
- The word "dinosaur" was coined to describe ancient very large animals discovered as fossils. Birds are not "terrible lizards" - they are birds. The later use of the word "dinosaur" by scientists does not alter the fact that the word is in practice used, by most people most of the time, in a sense very close to that originally intended. Ghmyrtle (talk) 15:14, 2 December 2010 (UTC)
- The issue seems to center on how broadly the term "dinosaur" is used or perceived. It looks like we've got a misconception within a misconception. The average citizen has been told over and over that "dinosaurs went extinct 65 million years ago." That statement appears to be an oversimplification of the situation. When people think of "dinosaurs", and of the fantasy of early hominids interacting with them, they think of T-rex and Brontosaurus and like that; not birds. ←Baseball Bugs What's up, Doc? carrots→ 15:04, 2 December 2010 (UTC)
- This is not a unique situation and we already have words to describe it. If we are talking about the monophyly of dinosaurs, then birds are dinosaurs. If we are talking about the paraphyly of dinosaurs, then birds are not dinosaurs. In official taxonomies, we are usually use the paraphyly, but in casual conversation we sometimes are talking about a monophyly. The same is true of whales and dolphins. The monophyly of even-toed ungulates includes hoofed mammals and whales and dolphins, whereas the paraphyly of even-toed ungulates only includes the hoofed mammals. Going even farther back, you could do the same humans and their fish ansestors. --—Arctic Gnome (talk • contribs) 23:54, 3 December 2010 (UTC)
Draft
It's much warmer inside my house than outside. So, I expected that opening the windows would cause the air inside to blow out, because the warm air inside should be at a higher pressure. But instead, I get a draft coming from the outside. What gives? 74.15.138.27 (talk) 05:57, 2 December 2010 (UTC)
- If you heat air in a fixed volume the pressure goes up, but that doesn't mean that warmer air is inherently at a higher pressure. The difference in pressure inside and out isn't going to be related to the temperature difference. Instead it's going to depend on what the weather is doing outside (for example if the wind is blowing toward your window). 24.98.193.82 (talk) 06:04, 2 December 2010 (UTC)
- To expand on 24.98's answer a bit; since your house is not perfectly airtight, it is likely at the same pressure as the outside, though at a different temperature. If you want to cool your house efficiently by opening the windows, your best bet is to open two windows on opposite sides of the room; this will allow for the air to move through your house; such that the cooler air can enter and the warmer air can escape. Placing an electric fan in the window will speed the process. --Jayron32 06:08, 2 December 2010 (UTC)
- If you don't want a through-house draft, then opening a window at the top and bottom of the room is fairly effective at setting up internal-external convection currents. This is how sash windows work, see the bottom of that article. CS Miller (talk) 06:51, 2 December 2010 (UTC)
- The reason you get a draft is the Chimney effect. The warm air inside the house is lighter than the cold air. So if you open a window at the bottom, you let cold air enter the house, and the warm air rises and exits through openings at the top (attics are usually ventilated). Ariel. (talk) 08:10, 2 December 2010 (UTC)
- The draught flowing into the OP's house must be counteracted by an equal draught flowing out otherwise the house would explode. The two air flows may simply be through the lower and upper parts repectively of the window opening. Cuddlyable3 (talk) 10:06, 2 December 2010 (UTC)
- The reason you get a draft is the Chimney effect. The warm air inside the house is lighter than the cold air. So if you open a window at the bottom, you let cold air enter the house, and the warm air rises and exits through openings at the top (attics are usually ventilated). Ariel. (talk) 08:10, 2 December 2010 (UTC)
- If you don't want a through-house draft, then opening a window at the top and bottom of the room is fairly effective at setting up internal-external convection currents. This is how sash windows work, see the bottom of that article. CS Miller (talk) 06:51, 2 December 2010 (UTC)
- To expand on 24.98's answer a bit; since your house is not perfectly airtight, it is likely at the same pressure as the outside, though at a different temperature. If you want to cool your house efficiently by opening the windows, your best bet is to open two windows on opposite sides of the room; this will allow for the air to move through your house; such that the cooler air can enter and the warmer air can escape. Placing an electric fan in the window will speed the process. --Jayron32 06:08, 2 December 2010 (UTC)
Thanks. 74.15.138.27 (talk) 15:45, 2 December 2010 (UTC)
Evolution of the wavefunction
If you knew the current wavefunctions in a system, is it possible to determine the future wavefunctions? The time evolution of the wavefunction is deterministic in an isolated system BUT that does not account for wavefunction collapse - Is wavefunction collapse deterministic or stochastic, and does that mean that it is possible or not to determine the future wavefunctions with certainty? 220.253.217.130 (talk) 10:52, 2 December 2010 (UTC)
Many scientists would claim that there is no such thing as wavefunction collapse, since any "measurement" (i.e. interaction) can itself be described by deterministic wave function evolution. See many worlds interpretation . Obviousely, any measurement of an isolated system is an interaction with the outside world and thus, the system is no longer isolated. 157.193.175.207 (talk) 12:25, 2 December 2010 (UTC)
- The outcome of a measurement is not deterministic, and this is pretty much true across the various QM interpretations except for hidden variable theories. When you make a measurement, the probability of which value the wavefunction will collapse to is determined by the value of the wavefunction, but the outcome is still stochastic. In terms of quantum decoherence, you become entangled in the state of what you're observing (which happens in a deterministic way) so that your wavefunction is a combination of all the different possible outcomes of the measurement. However, only one of those "you"s is the "you" that you experience, and you can't tell which one that's going to be, so in that sense it's still not deterministic. In other words, how the possible worlds will branch out is determined, but not which branch you'll seem to take. Rckrone (talk) 14:41, 2 December 2010 (UTC)
Can you safely drink rusty water?
Na, I'm not planning on doing it. This comes from a discussion I was having with someone yesterday about Irn Bru. He asserted that Irn Bru was originally just water that had sat in a vat with an iron girder in the bottom for a few weeks, sugared, carbonated and bottled (which is, I believe is a commonly held, albeit incorrect belief). Drinking rusty water (basically a suspension of iron(III) oxide, right?) as a regular beverage would make you rather sick, wouldn't it? --Kurt Shaped Box (talk) 12:12, 2 December 2010 (UTC)
- Why would it make you sick? Iron poisoning is possible I guess, but iron oxide does not absorb very well in the body. Ariel. (talk) 12:16, 2 December 2010 (UTC)
- Well water is known for being relatively highly mineralized, often with an "iron" taste, but I don't know that it's much of an issue. The issue with any water source is the possible presence of dangerous bacteria. ←Baseball Bugs What's up, Doc? carrots→ 15:17, 2 December 2010 (UTC)
- Rust itself is pretty harmless, I believe, but may be associated with other contaminants that are not. There are many possible issues other than bacteria: arsenic, lead, PCBs, etc, etc. Looie496 (talk) 18:17, 2 December 2010 (UTC)
- I doubt your friend's assertion, though, as iron has a rather unpleasant taste and smell. I believe that's what you taste in blood or marrow, and most people don't like the taste of those much. StuRat (talk) 05:19, 4 December 2010 (UTC)
Objective scientific evidence for PMS?
What verified scientific evidence is there that pre-menstrual tension actually exists objectively? I ask because firstly, I get all the symptoms listed here http://www.womenshealth.gov/faq/premenstrual-syndrome.cfm#c except the second one, but I'm a man. Secondly, isnt expression of irritability because the behavioural standards expected of women in office etc situations are more indulgent that those expected of other men - men get just as irritated but have to bottle it up? Thanks 92.24.186.163 (talk) 17:39, 2 December 2010 (UTC)
- You feel intense bloating, pain, cramping, and resultant irritation on a regularly monthly pattern, as a man? You really ought to see your doctor about that, if so. --Mr.98 (talk) 00:24, 3 December 2010 (UTC)
- Yes, although not just monthly. I don't think the physical pain or cramping is considered part of pre-mentrual tension. 92.29.114.35 (talk) 11:45, 3 December 2010 (UTC)
- Do you have a female significant other whose cycle your symptoms coincide with? Possibly you're feeling sympathy pains - although in the more general sense, not the specific case (pregnancy) covered by the article. It need not be a SO in the usual sense either - my wife claims (WP:OR, not WP:RS) that her twin brother used to feel some symptoms each month just before she got her period. 124.169.215.32 (talk) 01:23, 3 December 2010 (UTC)
- And where on earth did the OP get the idea that "the behavioural standards expected of women in office etc situations are more lax that those expected of men"? Surely the opposite is true. All sorts of extra demands are made of women, and not just in offices. Men have much greater leeway to behave aggressively, callously, selfishly, precipitately, and irresponsibly; they are not expected to display very much tact or sympathy; they are never expected to make themselves "available" in an altruistic, motherly fashion. The average male personality would, in a female body, invariably lead to a diagnosis of "bitchy", "crazy", or "stupid". But perhaps this is off-topic. LANTZYTALK 01:40, 3 December 2010 (UTC)
- I've countless times witnessed women being treated favourably and indulgently by men, compared with the standards they expect of other men. The most macho men are the worst at this. Its part of the tradition of male chivalry to women I suppose. For example Silvio_Berlusconi#Prostitution_scandal_and_divorce. 92.29.114.35 (talk) 10:58, 3 December 2010 (UTC)
- And where on earth did the OP get the idea that "the behavioural standards expected of women in office etc situations are more lax that those expected of men"? Surely the opposite is true. All sorts of extra demands are made of women, and not just in offices. Men have much greater leeway to behave aggressively, callously, selfishly, precipitately, and irresponsibly; they are not expected to display very much tact or sympathy; they are never expected to make themselves "available" in an altruistic, motherly fashion. The average male personality would, in a female body, invariably lead to a diagnosis of "bitchy", "crazy", or "stupid". But perhaps this is off-topic. LANTZYTALK 01:40, 3 December 2010 (UTC)
Nobody read PMS#Alternative_views then? 92.29.114.35 (talk) 11:00, 3 December 2010 (UTC)
Intelligent prey
Pigs are far more intelligent than dogs and cats, but to eat them is acceptable, whereas dog and cat meat is contraband in many places. What is the most intelligent animal that is regularly eaten, either by humans or by other animals? By "regularly" I mean that being eaten, or almost being eaten, is a part of its daily routine. LANTZYTALK 19:49, 2 December 2010 (UTC)
- Pigs are not an acceptable source of meat in many places: see Kosher and Islamic dietary laws. On the flip side of the coin, dogs, and to a lesser extent cats, are an acceptable source of meat in some areas: see Dog meat and Cat meat. What you consider an acceptable and unacceptable diet is not universally held. Buddy431 (talk) 19:58, 2 December 2010 (UTC)
- That's true, but I don't think Jews and Muslims object to pig-eating on ethical grounds. They regard pigs as unclean, not as sentient pink friends. LANTZYTALK 20:11, 2 December 2010 (UTC)
- Probably whale. Looie496 (talk) 20:01, 2 December 2010 (UTC)
- Agreed. StuRat (talk) 03:57, 3 December 2010 (UTC)
- Monkey is eaten in many parts of the world. See this oddly-titled National Geographic article, New Monkey Species Discovered, Then Eaten. (Notably, this article has an addendum that addresses the cultural and ethical issues about meat, bushmeat, and defining which animals are "acceptable" to eat). I will point out that there is no authoritative "ranking" of intelligence amongst the animal world - classifying a food-animal as "intelligent" or not depends entirely on various definitions of intelligence. Nimur (talk) 20:02, 2 December 2010 (UTC)
- An intelligent prey? A pig that wants to be eaten --Aspro (talk) 20:07, 2 December 2010 (UTC)
- Of the most commonly-eaten animals (cattle, lambs, pigs, etc.), pigs are surely the most intelligent. In the less-commonly-but-not-too-uncommonly-eaten category, I'd say octopus. WikiDao ☯ (talk) 20:13, 2 December 2010 (UTC)
- That National Geographic blog post from 2010 is eerily similar to this Onion article from 2005. -- BenRG (talk) 23:01, 2 December 2010 (UTC)
- It has nothing to do with intelligence, but rather with friendliness to humans. No animals are intelligent enough for intelligence to make any difference, but the emotional relationship to humans does matter. Ariel. (talk) 21:15, 2 December 2010 (UTC)
- Make any difference to whom? I know people who definitely wouldn't eat animals they thought were as intelligence as pigs or even cuttlefish. --Mr.98 (talk) 00:33, 3 December 2010 (UTC)
- Those people are not doing that based on intelligence of the animal, but rather things like ability to feel pain, or that they don't think it's right to eat animals at all. Ariel. (talk) 02:01, 3 December 2010 (UTC)
- There's many other cultural factors besides intelligence. Muslims don't eat non-marine carnivores. I believe other people avoid carnivores based on the idea that they accumulate toxins because they are higher on the food chain. Also, dogs, cats, and horses have a companion status much more than other animals, which my explain why most cultures don't regularly consume them. Similarity to us is another big factor culturally. Intelligent non mammals dont get the same status for the purpose of eating them and experimenting on them as mammals, even if they are more intelligent than many mammals. Apes, monkies, and other simians also get a higher level of that respect in most cultures simply based on their perceived similarity to us. Roberto75780 (talk) 00:57, 3 December 2010 (UTC)
- Yes, I imagine we consider factors other than intelligence when deciding which animals to eat. Succulence, for instance. If cognitive powers were the only relevant factor, I suppose Ariel Sharon and Terri Schiavo would be regarded as foodstuffs. Anyway, I was more interested in looking at it from the animal's perspective. I'm not so interested in our obligation towards intelligent lifeforms, I'm interested in the usefulness of intelligence to its possessor. I'm curious whether intelligence always coincides with the ability not to get eaten, in which case predators would always be more intelligent than prey. That's why I'm less interested in the animals humans eat than in the animals animals eat. Humans can eat anything, and probably will. But if there were a highly intelligent species being preyed upon (with great regularity) by a less intelligent species, that would be very interesting. Are there any instances of that in nature? LANTZYTALK 01:21, 3 December 2010 (UTC)
- Hmmm... such as humans being consumed by viruses, bacteria, and other microbes? ←Baseball Bugs What's up, Doc? carrots→ 01:36, 3 December 2010 (UTC)
- That's true, but somehow it doesn't really rattle my faith in intelligence. Perhaps it should. You're right, parasites regularly prey upon much more intelligent organisms. It's just that this kind of predation isn't quite as striking as if, say, orangutans were to be eaten by butterflies. LANTZYTALK 01:47, 3 December 2010 (UTC)
- Sharks eat dolphins (or try to). Intelligence is not a way to rank who eats who. Ariel. (talk) 02:01, 3 December 2010 (UTC)
- If you had a disabled ape and an undending supply of butterflies that had developed a taste for primate flesh, that orang might indeed be in trouble. Every living thing gets eaten eventually, or "recycled" if you will. No matter how smart pigs are, in general they haven't gotten smart enough to figure out how to unlock the pens they're kept in. The proscription against eating things like hogs and bottom-feeding marine creatures has to do at least in part with the idea that they are "unclean" because they are scavengers, and there is some reasonable basis for that argument, at least in older times when nothing was known about biochemistry other than what could be observed with the naked eye. ←Baseball Bugs What's up, Doc? carrots→ 02:14, 3 December 2010 (UTC)
- It's an interesting notion, a discrepancy on average in intelligence between predator and prey. Our Predation article does not say directly, but has some interesting "food for thought" along those lines.
- On the separate point of animal consumption by humans: domesticated animals tend to be selected and bred for docility, which can resemble unintelligence. WikiDao ☯ (talk) 03:59, 3 December 2010 (UTC)
- A bird spider's diet includes birds and mice, both of which I assume to be more intelligent. StuRat (talk) 03:57, 3 December 2010 (UTC)
- There's a related question I had about the intelligence of prey, which I think I've now figured out. It always seemed odd to me that large herds of prey animals (say antelope) will run from a small pack of predators instead of turning and attacking them together. They could easily defeat the predators, if they worked together, so why don't they ? My conclusion was that prey animals rely on predators to weed out the weak and thus allow only the strongest genes to get passed on. Thus, any herd which learned how to defend itself from predators would find it's genetic health deteriorate and might eventually disappear, leaving behind the other herds that didn't defend themselves. StuRat (talk) 04:03, 3 December 2010 (UTC)
- I think we're throwing around words like "intelligence" rather loosely. These animals aren't doing calculus or reading Sun Tzu here. When we're comparing the intelligence of pigs to antelopes to chihuahuas, its on an entirely different scale than human intelligence. One must take care not to anthropomorphize non-human animals to the point of assigning human motivation to them or attempting to justify behavior on human standards. The reason antelopes don't turn and attack predators is likely because they lack the faculties to strategize in that manner. Animal group behavior can be complex and still the animals can lack individual intelligence; witness ant colonies for example. "Turn and run from threat" is a hardwired response for even some of the least intelligent animals out there; "organize an effective counteroffensive" is somewhat more nuanced strategy usually requiring attendence of a military college of some sort. --Jayron32 07:27, 3 December 2010 (UTC)
- Many such herd animals already know how to fight with each other, it's just a matter of turning that instinct against the predators. The same head down, straight on attack that works against another antelope would also work against the predators, if the entire herd did it. There's also the problem, though, that the first animal to defend the herd like that would be taking an increased risk, which would mainly benefit others, so his genes would be less likely to be passed on than the coward's. StuRat (talk) 05:07, 4 December 2010 (UTC)
- AFAIK, some corvid species actually do launch coordinated counterattacks against their predators, working together to distract, harass, drive away and/or kill (if the opportunity arises). Stuff like creating a noisy distraction in front, whilst other birds outflank and attack from the rear. --Kurt Shaped Box (talk) 07:43, 3 December 2010 (UTC)
- Yes, see animal mobbing behavior. While many birds perform this behaviour, crows are the standard example and it's probably no coincidence that they're also widely regarded as being extremely intelligent. Matt Deres (talk) 14:40, 3 December 2010 (UTC)
- What about parrots? Some species (the African Grey Parrot or the large Macaws and Cockatoos for example) are thought to have a level of intelligence comparable to the non-human great apes - yet they often fall prey to various raptors. --Kurt Shaped Box (talk) 07:18, 3 December 2010 (UTC)
- A Grey Parrot might have the intelligence of a child age 3-5, but honestly, that level of intelligence is not a decisive advantage in preventing you from getting eaten. If the parrot had the intelligence of an adult human and could figure out how to use tools extensively that would be a huge help, but even some humans get eaten by wild animals from time to time. Googlemeister (talk) 14:47, 3 December 2010 (UTC)
- If the parrot had the intelligence of a human, it would recruit a bunch of other parrots from the flock, find out where the predator lived was and 'do' it whilst it was sleeping. --Kurt Shaped Box (talk) 18:02, 3 December 2010 (UTC)
- I thought people avoided eating dogs, cats, foxes, crows and other carnovores because the meat did not taste very nice. Although dogs are eaten in Thailand (?). 92.29.114.35 (talk) 11:10, 3 December 2010 (UTC)
- I always thought that it was more that case that animals which turn vegetable matter into meat directly are more efficient to farm than an animal (say, a dog) which converts meat into meat. If you wanted to farm dogs for meat for instance, you'd need to farm something else (cows, for example) to provide meat to feed the dogs. I think it works out that you'd need a larger number of cows to feed the dogs to feed the people than the number of cows needed to feed the people directly... --Kurt Shaped Box (talk) 11:38, 3 December 2010 (UTC)
- Yes, you would need far more cows to feed dogs to feed people, maybe 10X as much, due to the inefficiency of our digestive systems. An exception to that problem is if the predators can find their own food. For example, if cats are finding rodents on their own, then eating them doesn't require you to raise rodents for them. Another exception might be if you supply them with food that people would find unacceptable, like roadkill. However, there's another problem in that toxins tend to accumulate in predators, with apex predator's being the worst. That's one reason why there's more mercury in some fish than others. StuRat (talk) 05:14, 4 December 2010 (UTC)
- I recall reading that crow meat tastes horrible. And despite foxes being regularly hunted, there's never been any reports of them being eaten, as other hunted animals such as deer hares or rabbits are. People eat various animals in the far est for 'medicinal' reasons rather than enjoying the taste. 92.29.114.35 (talk) 11:56, 3 December 2010 (UTC)
- I think that's a general feature of scavengers, they taste like the decomposing food they eat. They don't mind the toxins they absorb, but we do. StuRat (talk) 19:29, 4 December 2010 (UTC)
Split down the middle
Often people have survived the loss of a large portion of their brain, and there is also a procedure whereby the corpus callosum is severed, separating the two hemispheres. So what if a person's brain were completely split, all the way down to the spine, but left otherwise intact? Would the brain become, in effect, two brains? (Obviously, assuming a form of neurosurgery far beyond what we have today.) Without any means of interface, how could the hemispheres not diverge and become two distinct individuals sharing a skull? To continue the mad science, suppose we carry on down the spine, splitting the organism into two pieces, Mr. Right and Mr. Left. (Never mind the heartless Mr. Right - we'd have a cloned implant on ice.) Is it theoretically possible, given the general symmetry of chordates, to split one lengthwise into two living, functioning halves? Or is our symmetry specious and superficial? LANTZYTALK 20:07, 2 December 2010 (UTC)
- I'm not sure where you're going with wanting to split even the spinal column, but you can do just fine (as an "individual" person) with only half a brain (with of course some impairment – though some people have been born with only one hemisphere, and they do much better than the surgical patients). And of course you may also find our Split-brain article of interest. WikiDao ☯ (talk) 20:35, 2 December 2010 (UTC)
Such a person would be completely, or almost completely, paralyzed. The great majority of the motor outputs from the brain control the opposite side of the body, and the crossings (decussations) occur inside the brain, in the midbrain and brainstem. Looie496 (talk) 20:37, 2 December 2010 (UTC)
- Our article Hemispherectomy touches on Looie496's statement. Comet Tuttle (talk) 21:01, 2 December 2010 (UTC)
- It is stunning that you can remove half the brain with little ill effect. :o --Sean 18:43, 3 December 2010 (UTC)
So, as one would expect, bisecting the lower brain is quite a different matter than splitting the cerebrum. It looks like it will have to remain just a beautiful dream... Of course, theoretically, the decussations could be untangled and rewired. What if we try something a little less ambitious, and just cut down through the brain to where the decussations begin? LANTZYTALK 21:04, 2 December 2010 (UTC)
- decussation n. A crossing or intersection of lines etc. so as to form an X-shape. Cuddlyable3 (talk) 22:50, 2 December 2010 (UTC)
Forces in space
My friend told me that if you push against something in space, you will move away much more than you would on Earth. If this is true, is it something to do with Newton's Third Law? Or Momentum? I'd like this information to use it in something I'm working on. Thanks a lot! --Editor510 drop us a line, mate 21:44, 2 December 2010 (UTC)
- I think I've sussed it, but I'm looking for confirmation, here. Is it that in space, you and another object would be exactly the same weight, thus making the Third Law kick in on a much larger scale than it does in gravity equivalent to 1 Earth?--Editor510 drop us a line, mate 21:55, 2 December 2010 (UTC)
- No, it's not weight (not directly). The difference is whether you can brace against the earth, and transfer the reaction force there. If you can brace, you can move something without moving yourself (relative to the earth). In space, the third law still applies, but you have nowhere to put the momentum, so it must be you that goes flying. --Tardis (talk) 21:59, 2 December 2010 (UTC)
- Oh, I get it. So you absorb all the momentum the Earth would usually absorb? That makes sense! Thank you!--Editor510 drop us a line, mate 22:02, 2 December 2010 (UTC)
Resolved
- Editor510 you still need to get the terms right. You and another object usually have different masses which never change. On Earth the masses are experienced as weights. In outer space there is no weight. If you and the object are both standing on a perfectly slippery ice rink, then Newton's 3rd Law operates similarly to being in space. If you push the object, both you and the object start moving apart. Cuddlyable3 (talk) 22:42, 2 December 2010 (UTC)
- Exactly, and for example: Ever see a hockey fight? They tend to grab the jersey of their opponent with one hand and punch with the other. If they did not do so, half (roughly) of the energy of the punch would be used up in pushing the punch-er backwards. Same kind of thing would happen in space. ArakunemTalk 16:51, 3 December 2010 (UTC)
- Editor510 you still need to get the terms right. You and another object usually have different masses which never change. On Earth the masses are experienced as weights. In outer space there is no weight. If you and the object are both standing on a perfectly slippery ice rink, then Newton's 3rd Law operates similarly to being in space. If you push the object, both you and the object start moving apart. Cuddlyable3 (talk) 22:42, 2 December 2010 (UTC)
- No, it's not weight (not directly). The difference is whether you can brace against the earth, and transfer the reaction force there. If you can brace, you can move something without moving yourself (relative to the earth). In space, the third law still applies, but you have nowhere to put the momentum, so it must be you that goes flying. --Tardis (talk) 21:59, 2 December 2010 (UTC)
December 3
Drinking from a lake
Whenever I watch survival shows on Discovery Channel, the hosts always say the water from lakes and creeks needs to be boiled before I drink it. So why don't animals drinking from the same water source get sick? Hemoroid Agastordoff (talk) 00:10, 3 December 2010 (UTC)
- Animal immune systems will develop a resistance to the microbes they commonly encounter in their local water. In mammals, that resistance can also be partially passed to young animals by breastfeeding, which helps protect the young. In many cases, the human immune system would also develop a tolerance after prolonged exposure, but the first few times you tried the local water there is a chance you could get very sick. Water-borne pests are still a significant cause of death in some parts of the world. Altogether it is generally safer for humans to boil water they find outdoors. Dragons flight (talk) 00:17, 3 December 2010 (UTC)
- Some of those "pests" can be severe/lethal. For example, Naegleria fowleri, Entamoeba histolytica, Hepatitis A, and Hepatitis E (20% mortality in pregnant women). Here's a recent real-world example. -- Scray (talk) 01:36, 3 December 2010 (UTC)
- In developed countries, the chances of getting sick from drinking from a lake or creek are actually pretty low, unless it contains raw human sewage. Paranoia about this has reached such a level nowadays that backpackers often feel compelled to treat water from even the most pristine mountain streams, which I think is ridiculous. Looie496 (talk) 06:19, 3 December 2010 (UTC)
- Well, the chance of giardiasis is pretty low, but it's nasty enough (even though rarely lethal) that it's understandable people don't want to take a chance. I understand the treatment is about as nasty as the disease itself, so that's a double-whammy. If you get a ceramic filter and pump it through, it changes the taste very little. --Trovatore (talk) 06:51, 3 December 2010 (UTC)
- Add to the list Pfiesteria, which while rare, can be particularly nasty. --Jayron32 07:02, 3 December 2010 (UTC)
- Um, no, I would not add Pfiesteria to the list of human pathogens in fresh water, since it is not a human pathogen based on current understanding. If you have a current, reliable source to the contrary, please share. -- Scray (talk) 12:20, 3 December 2010 (UTC)
- Not saying that people should go out and do this, but when I was in northern Minnesota a few years back, I drank water straight out of the lakes for a week with no ill effects of any kind. Googlemeister (talk) 14:31, 3 December 2010 (UTC)
- I've seen wildly varying advice on this, and I agree that it would be highly desirable to have a better answer for this - preferably not "yes" or "no" but a realistic estimate of the actual risks for water from various sources. Wnt (talk) 17:29, 3 December 2010 (UTC)
- I (and others) have provided links to very real diseases, and many of those articles specifically cite untreated fresh water as a source of those infections. Those articles also indicate the risk varies by season, geographic region, regional flooding, proximity of livestock, and other factors. No single "rate" would be a good estimate of a specific situation. -- Scray (talk) 03:58, 4 December 2010 (UTC)
- I've seen wildly varying advice on this, and I agree that it would be highly desirable to have a better answer for this - preferably not "yes" or "no" but a realistic estimate of the actual risks for water from various sources. Wnt (talk) 17:29, 3 December 2010 (UTC)
- Not saying that people should go out and do this, but when I was in northern Minnesota a few years back, I drank water straight out of the lakes for a week with no ill effects of any kind. Googlemeister (talk) 14:31, 3 December 2010 (UTC)
- Um, no, I would not add Pfiesteria to the list of human pathogens in fresh water, since it is not a human pathogen based on current understanding. If you have a current, reliable source to the contrary, please share. -- Scray (talk) 12:20, 3 December 2010 (UTC)
- Add to the list Pfiesteria, which while rare, can be particularly nasty. --Jayron32 07:02, 3 December 2010 (UTC)
- Well, the chance of giardiasis is pretty low, but it's nasty enough (even though rarely lethal) that it's understandable people don't want to take a chance. I understand the treatment is about as nasty as the disease itself, so that's a double-whammy. If you get a ceramic filter and pump it through, it changes the taste very little. --Trovatore (talk) 06:51, 3 December 2010 (UTC)
- In developed countries, the chances of getting sick from drinking from a lake or creek are actually pretty low, unless it contains raw human sewage. Paranoia about this has reached such a level nowadays that backpackers often feel compelled to treat water from even the most pristine mountain streams, which I think is ridiculous. Looie496 (talk) 06:19, 3 December 2010 (UTC)
- Some of those "pests" can be severe/lethal. For example, Naegleria fowleri, Entamoeba histolytica, Hepatitis A, and Hepatitis E (20% mortality in pregnant women). Here's a recent real-world example. -- Scray (talk) 01:36, 3 December 2010 (UTC)
- Also, animals in the wild have a much higher mortality rate than those in captivity precisely because of these kinds of risks. --Sean 18:45, 3 December 2010 (UTC)
- Crocodiles, cougars, wolfs, bears and lions are more of a risk for animals in the wild, the hard winters might also add to the risk. Most Americans will avoid the not-chlorinated fresh water because they are not used to the taste. I drank water in Baltimore and I would avoid to swim in a pool chlorinated with that amount of chlorine, but the US colleagues said they do tast the chlorine.--19:01, 3 December 2010 (UTC)
Better than ice bottles
I heard from a friend that using antifreeze bottles rather than ice bottles can greatly increase the cooling effect in a picnic cooler. The basic idea is that by keeping the water liquid down to -18 °C, you will keep its heat capacity high, because water has about double the heat capacity of ice. This effectively doubles the power of the bottles(until it they reach 0 °C anyway).
My question is, does water with antifreeze in it have the same or similar heat capacity as plain water? How much antifreeze does it take to keep water liquid down to about -18 °C anyway? I think automotive antifreeze is good enough to -40 °C, so it can be diluted if antifreeze doesnt have as much heat capacity as water.
Oh by the way, for those who really like to get technical, I know the densities are all different so lets just assume we are dealing with volumetric heat capacity. I'm gonna use a four 2L Coke bottles in a big cooler and weight savings are insignificant. Roberto75780 (talk) 00:50, 3 December 2010 (UTC)
- I don't this makes sense. The heat of fusion of water means that when ice melts it absorbs heat equivalent to what you'd need to raise its temperature by over 70°C. If you start with chilled liquid you lose that benefit. --Anonymous, 01:03 UTC, December 3, 2010.
- Yes, I thought of that, too. If your freezer goes down to -18°C or -40°C, then you could freeze that and possibly get some benefit relative to water, but most freezers won't. I don't recommend putting antifreeze anywhere near food, though, since it may leak and is poisonous. Salt-water would be a safer alternative, is less expensive, and also lowers the freezing point of water down to -18°C or below. And yes, salt-water is poisonous in large quantities, but you couldn't possibly choke down enough food drenched in salt-water to harm you. StuRat (talk) 03:33, 3 December 2010 (UTC)
- Why would you have a benefit? The specific heat of propylene glycol is 2.507 j/gK vs. 4.18 j/gK for water. I couldn't find the heat of fusion of propylene glycol but I can't imagine it's more than water. Water is a very far outlier as far as heat capacity goes, I don't know of any material that beats it. According to Specific heat#Table of specific heat capacities water is tops on volume, and close to the top by mass. Ariel. (talk) 05:16, 3 December 2010 (UTC)
- Because most of the benefit of ice is in the heat it takes to melt it, you get a fairly quick increase in temp up to the melting point, then it languishes there for a long time, then once it melts you get another fairly quick raise in temp to the ambient temperature. Thus, the benefit of either antifreeze or saltwater is that, if you can get it cold enough to freeze, it should hover at that lower temp while melting, and thus provide more cooling during that period. StuRat (talk) 04:55, 4 December 2010 (UTC)
- There were (and may still be) these freezer bricks called "Blue Ice" which I think contained antifreeze such that although they did freeze in your freezer, they froze colder, or something. (I've still got several of 'em, but most of the ones I used to have developed leaks, which made for a real mess.) We don't have an article, but our Blue ice disambiguation page does contain a redlink for "Blue Ice (ice pack), an artificial ice pack filled with propylene glycol manufactured by Rubbermaid". —Steve Summit (talk) 02:26, 3 December 2010 (UTC)
- The don't freeze colder. As best they just remain flexible allowing you to mold them to fit around the item. Ariel. (talk) 05:16, 3 December 2010 (UTC)
Not at all! the heat of fusion (heat absorbed during melting) itself for water is equal to the heat absorbed in a 79 °C temperature change! Hoever, if you put just enough antifreeze so that the ice would still freeze, but at a lower temperature (typical freezer is like -18C) you could benifet a little. keep in mind though, that the antifreeze ingredient takes up significant portion of the solution and it has a lower heat capacity and heat of fusion than water. so you wont bennifet much at all. what you should do, is just add a little salt. its cheaper, not poisonous, and it doesnt take up much space (infact, adding salt doesnt significantly affect the volume of the water, believe it or not). even with the salt though, the difference is hardly worth the hassle. see if you can just add more ice! use square bottles instead of round ones. —Preceding unsigned comment added by 209.148.241.197 (talk) 08:51, 3 December 2010 (UTC)
- You're the second person who said this - how would they benefit? Just because the water is frozen doesn't mean the specific heats goes away - you can still chill it to -18c, you're just chilling ice instead of water. Ariel. (talk) 09:07, 3 December 2010 (UTC)
- The heat capacity of liquid water is 4.18 J/g/K, whereas that for water ice is 2.05 J/g/K. That is, it takes about twice as much heat to raise the temperature of liquid water 1°C than it does to raise the temperature by 1°C of the same amount of water as ice. That's for pure water, though. Additives would change this, though. -- 174.31.199.95 (talk) 17:03, 3 December 2010 (UTC)
UPS watt, volt-amp question
I got a UPS today (one of many I've had through the years). It is "700 watts" but only "425 volt-amps". A watt is a volt-amp. The voltage is about 120, so why don't these figures match? Is it because the UPS output is a square wave? Bubba73 You talkin' to me? 05:24, 3 December 2010 (UTC)
- The article Volt-ampere explains the difference between volt-amps and watts. They are only equal in DC circuitry. --Jayron32 05:52, 3 December 2010 (UTC)
- I think they're the same for resistive AC loads, too, aren't they? See also power factor. —Steve Summit (talk) 05:56, 3 December 2010 (UTC)
- True, because the load is constant even if the source is AC. Strictly speaking, though watts and volt-amps are identical through dimensional analysis, they measure slighly different things. The relationship between watts and volt-amps is roughly analagous to the relationship between work and energy. While they are both measured in Joules, they are not identical concepts. --Jayron32 06:01, 3 December 2010 (UTC)
- All I meant was that the values could be equal. As you say, they certainly measure different things. —Steve Summit (talk) 06:10, 3 December 2010 (UTC)
- In AC circuits the volt-amps can be larger than the watts if there is not unity power factor (resistive load), but I don't understand the 700 watt and 425 voltamp rating. Is 700 watts the output rating or the input (from the mains to the UPS)? Edison (talk) 19:17, 3 December 2010 (UTC)
- All I meant was that the values could be equal. As you say, they certainly measure different things. —Steve Summit (talk) 06:10, 3 December 2010 (UTC)
- True, because the load is constant even if the source is AC. Strictly speaking, though watts and volt-amps are identical through dimensional analysis, they measure slighly different things. The relationship between watts and volt-amps is roughly analagous to the relationship between work and energy. While they are both measured in Joules, they are not identical concepts. --Jayron32 06:01, 3 December 2010 (UTC)
- I think they're the same for resistive AC loads, too, aren't they? See also power factor. —Steve Summit (talk) 05:56, 3 December 2010 (UTC)
- Whoops - I got it bavckwards, 700va, 425 watts. Bubba73 You talkin' to me? 04:37, 4 December 2010 (UTC)
Getting a guinea pig to drink from a bottle
Is it possible to accustom a 4-month-old guinea pig to drink from a bottle, or will they only drink from it if trained to do so from a young age? Thank you to anyone who can help. Leptictidium (mt) 07:45, 3 December 2010 (UTC)
- its deffinately possible. add salt to the water and they will drink more. check the water level to make sure hes drinking enough before leaving that as his only source of water. and make sure its steady enough so you are not measuring a whole lot of water lost to dripping! 209.148.241.197 (talk) 08:55, 3 December 2010 (UTC)
- Salt???? That would do it harm and would not quench its thirst. It would be like humans drinking seawater. If there is no other water available and it finds a drop of water at the bottle, then its going to lick that. I would find out if its customary to use water bottles with them. 92.29.114.35 (talk) 11:27, 3 December 2010 (UTC)
- That would all depend on the amount of salt. After all, some salt is essential for life, but they probably already get that amount from their food. Humans tend to get salt from both food and drinks, but usually most from food. StuRat (talk) 04:43, 4 December 2010 (UTC)
- Guinea pigs naturally eat food and water without any added salt. Most humans, at the very least in the West, are consuming far too much salt. (There seems to be zero teaching about health in the US of A). 92.24.177.111 (talk) 12:12, 4 December 2010 (UTC)
- Yes, people eat too much salt, but that's a direct result of it being deficient in a natural diet, which has led to us craving it wherever we can find it. Similarly, guinea pigs likely crave salt, which is probably why it's the 6th ingredient in this food product for them: [12] (pick "MORE INFORMATION" for the ingredients list). StuRat (talk) 16:31, 4 December 2010 (UTC)
- People have evolved to enjoy eating things that were in short supply in the diets in the distant past. That does not mean that its healthy to consume whatever it is abundantly. Poor guinea pigs. 92.15.23.156 (talk) 18:59, 4 December 2010 (UTC)
- No, and neither does it mean that we should try to put them on a totally salt-free diet, which would no doubt kill them. StuRat (talk) 19:25, 4 December 2010 (UTC)
- Generally most animals will find their way to a water source when they're thirsty. Water bottles are usually recommended over bowls, as they are more hygienic (provided it's kept clean) and the guinea pig won't be able to soak it's enclosure by taking an impromptu bath. A bottle with a stainless steel ball bearing ("sipper bottle") is not supposed to leak, but they often do, a little. This means that there's usually a drop of water hanging from the end of the tube, which will give the guinea pig a hint. Setting the guinea pig in front of the bottle or vice versa so that it can see there is water there may also be useful. If you have other guinea pigs, it may learn from observing them. Adding salt to the water is not a good idea, and also will not help your guinea pig "discover" the bottle for the first time; however you could smear a little of some food the pig finds tasty on the tip of the bottle to encourage it to drink. If you're concerned that your guinea pig is not taking an adequate amount of water, you should contact your vet for advice. Typical water intake is 10ml per 100g body weight per day. ([13]). --Kateshortforbob talk 12:11, 3 December 2010 (UTC)
- Honestly, call the local pet store, they can probably give you better feedback on this than we can over the phone, for free. 90% of the advice you'll get on this topic here will be related to anecdotes of half-remembered childhood pets. ;-) --Mr.98 (talk) 13:14, 3 December 2010 (UTC)
- To teach baby chickens to drink you dunk their beaks in water. Maybe you could do a similar thing where you gently press your critter's snout against the water ball so it gets the idea. --Sean 21:55, 3 December 2010 (UTC)
Purifying Iron
When Iron is extracted from ore, it goes through a process where while highly heated it is exposed to the air and the Carbon impurities react with O2 to form CO2. Why doesn't the iron also react with the oxygen? Chipmunkdavis (talk) 09:33, 3 December 2010 (UTC)
- Two reasons, which are related. Carbon reacts stronger with O2 than iron does, so the carbon will burn off first. The second reason is that it's too hot. It's hot enough that it thermolyses the iron oxide back into iron and oxygen - but CO2 is bound too strongly for that temperature to thermolyse it back to carbon (and also the CO2 escapes as a gas). Ariel. (talk) 10:46, 3 December 2010 (UTC)
- If it is so hot to thermolyze the iron(III) oxide, why not just heat the iron(III) oxide without the carbon? Is the carbon the stuff making the heat? --Chemicalinterest (talk) 14:08, 3 December 2010 (UTC)
- Iron filings or steel wool burn nicely in atmosphere when heated red hot. Don't they refine ore (containing iron oxide) by heating it in an atmosphere without much free oxygen, like a "reducing atmosphere," whatever that is? Perhaps the burning charcoal produces superhot air with products of combustion and little excess oxygen. Early US iron works in the 1700's and early 1800's had big stone furnaces with charcoal in the bottom, and ore above, and the ore was not exposed to excess air, to keep it hot and to avoid basically burning or oxidizing the superheated iron. "Blooms" or lumps of refined iron were then left mixed with slag. William Kelly and Bessemer later came up with the process of heating molten iron and pumping in oxygen to burn off the excess carbon and make steel. Edison (talk) 19:14, 3 December 2010 (UTC)
- (ec) While I don't have any entropy/enthalpy data at hand for the reaction 4 Fe + 3 O2 ⇌ 2 Fe2O3, I do seriously doubt that Fe2O3 notably decays into its elements at temperatures around 1700°C. What could happen instead is the following reaction: Fe2O3 ⇌ 2 FeO + O2 (many transition metal oxides in higher oxidation states give off O2 at higher temperatures, fx CrO3 which becomes Cr2O3). According to our article, FeO (which is only stable at higher temperatures anyways) has a (measurable) boiling point of 3414°C, so it can't possibly start decaying into its elemnts at temperatures of 1700°C, or else there'd be nothing more left at 3414°C.
- The carbon does indeed make the heat which is necessary to get the actual iron reduction reaction going. It first burns exothermically to CO2 and then reacts with more coal to form CO, which is the actual reducing agent (see Blast_furnace#Chemistry). The product of the reaction still has some C in it, so I guess they're adding some excess C in the beginning to get all the iron(III) oxide reduced and after that they remove some of the excess C in further refinement processes. --178.26.171.11 (talk) 19:21, 3 December 2010 (UTC)
- If it is so hot to thermolyze the iron(III) oxide, why not just heat the iron(III) oxide without the carbon? Is the carbon the stuff making the heat? --Chemicalinterest (talk) 14:08, 3 December 2010 (UTC)
Cat's nipples
How many nipples has a female/male cat? 178.42.62.13 (talk) 11:17, 3 December 2010 (UTC)
- Male cats, like female cats, have 6 nipples. Cuddlyable3 (talk) 12:19, 3 December 2010 (UTC)
- Citation needed. Here's one with seven clearly visible, and presumably an eighth hidden by fur: [14]. (Note that a Google Image search for cat nipples may not be work safe.) That agrees with the number in the table at Mammary gland#Other mammals, though that table doesn't appear to have a source listed. TenOfAllTrades(talk) 13:33, 3 December 2010 (UTC)
- Apparently the answer is 8. I googled "feline nipples", and this interesting page came up:[15] ←Baseball Bugs What's up, Doc? carrots→ 21:22, 3 December 2010 (UTC)
- Citation needed. Here's one with seven clearly visible, and presumably an eighth hidden by fur: [14]. (Note that a Google Image search for cat nipples may not be work safe.) That agrees with the number in the table at Mammary gland#Other mammals, though that table doesn't appear to have a source listed. TenOfAllTrades(talk) 13:33, 3 December 2010 (UTC)
human hunting
Say if humans never invented weapons or any current civilazation like today and stay like in the stone age what would we have used as weapons to kill prey and if not what would of we used to look for food would we have been scavengers, use plants as food or would we be using insects or fish as food.--213.94.232.217 (talk) 13:59, 3 December 2010 (UTC)
- Tool use is pretty definitive for the idea of "human". The remnant stone age societies today use the same weapons that our stone age ancestors did - stone arrows, spears, axes, etc. Hunter gatherer societies do eat plants and insects and meat - but so do developed ones. We just (mostly) farm ours, instead of gather them, and some species are better adapted for farming than others, so we have a smaller variety. 75.41.110.200 (talk) 14:28, 3 December 2010 (UTC)
- As the person above intimated, our connection to tool use is profound - we've used tools since before we were human. Our nearest ancestors, the chimps, use tools as well, though not nearly as sophisticatedly as we do. That being said, the diet of chimps is probably pretty close to what our pre-tool ancestors ate (.e. an omnivorous diet consisting of pretty much anything that they could safely get their hands on). Matt Deres (talk) 14:55, 3 December 2010 (UTC)
No i mean say if humans never invented tools or weapons how would we get our food then. --213.94.232.31 (talk) 14:51, 3 December 2010 (UTC)
- In that case you would have to eat raw fruit and vegetables, and leaves and grubs and insects, like many other primates. But the making of tools is one of the defining characteristics of being human, so it's a somewhat meaningless question.--Shantavira|feed me 15:00, 3 December 2010 (UTC)
- Somebody mentioned recently that the human gut has evolved alongside cookery (making fire part of our phenotype, I suppose). Without tools we'd have different anatomy, and different brains, and be something like large chimps, only without the inclination to wave sticks around. I'm bemused by the questions "if humans never invented weapons ... what would we have used as weapons?" and to that part I can only answer "teeth". The reference to scavengers reminds me of neanderthals, whose large jaws are supposed to be for cracking bones to get at the marrow. Maybe your question is "what type of diet did our nearest non-tool-using primate ancestor have?". Human_evolution#Divergence_of_the_human_lineage_from_other_Great_Apes seems to say that ancestor was Paranthropus, and that article gives the answer "a diet of grubs and plants". Though, actually, it seems likely that everything that looks at all like a great ape will from time to time pick up a stick and make some use of it, so perhaps we need to go way back to an ancestor somewhat like a lemur; and even lemurs can be trained to use tools, though they haven't been seen using tools in the wild. Lemurs eat fruit, leaves, flowers, bark, sap, spiders, caterpillars, grasshoppers, the odd bird and lizard and by the sound of it pretty much anything else as well. 213.122.16.186 (talk) 15:20, 3 December 2010 (UTC)
- [citation needed] on your assertion that the robust jaw of Neanderthals was "supposed to be for cracking bones to get at the marrow". Besides the fact that bones are extremely hard and difficult to bite into (few animals do it, considering the nutrient value), Neanderthals also had stone butchering equipment which could much more easily accomplish that task. The size of their jaws may have been influenced by their diet, but they were more robust than modern humans in most respects; cracking bones for marrow didn't give them their supraorbital torus, for example. Our article also notes that they were apex predators, like us. Matt Deres (talk) 17:50, 3 December 2010 (UTC)
- Ah... maybe I'm getting confused with Homo erectus [16]. Recently I read, but I can't remember where (which probably means in reality it was about ten years ago) a theory which said, in essence, that one bunch of hominids had taken the evolutionary path of being able to think hard and run fast, while the other bunch invested much more heavily in being able to chew. 81.131.9.41 (talk) 19:27, 3 December 2010 (UTC)
- (I have no idea what that site is, but google books says the text comes from the Gale Encyclopedia of Science. And I know it doesn't say anything about jaw evolution, in fact it mentions "sophisticated tools," but it does say they scavenged.) 81.131.9.41 (talk) 19:38, 3 December 2010 (UTC)
- 213's comment "Without tools we'd have different anatomy, and different brains" is correct. Take a look at Human_evolution#Use_of_tools: it suggests a sort of evolutionary virtuous circle where tool use allowed a more energy-rich diet, which in turn allowed selection for larger, more energy-consuming neocortexes which consequently promoted greater tool-use and so on. There's an extensive chicken/egg type debate about to what extent brain structure is dictated by behaviour and vice-versa as well (check out the Noosphere article), so even a hypothetical question regarding 'non-tool using humans' is difficult to meaningfully answer. Take a look at the first half-hour of 2001: A Space Odyssey for an entertaining take on some of the ideas. Blakk and ekka 18:20, 3 December 2010 (UTC)
- [citation needed] on your assertion that the robust jaw of Neanderthals was "supposed to be for cracking bones to get at the marrow". Besides the fact that bones are extremely hard and difficult to bite into (few animals do it, considering the nutrient value), Neanderthals also had stone butchering equipment which could much more easily accomplish that task. The size of their jaws may have been influenced by their diet, but they were more robust than modern humans in most respects; cracking bones for marrow didn't give them their supraorbital torus, for example. Our article also notes that they were apex predators, like us. Matt Deres (talk) 17:50, 3 December 2010 (UTC)
- If we had never invented tools, we probably would have gone extinct. It's our ability to control our environment that makes us unique among animals, and improves our survival chances. ←Baseball Bugs What's up, Doc? carrots→ 21:19, 3 December 2010 (UTC)
Bismuth(III) iodide dilemma
Why does bismuth(III) iodide say that it is a greenish-black solid in infobox, gray-black solid in article, and pale yellow solid in picture? Is it different forms like alpha and beta forms? Thanks, --Chemicalinterest (talk) 14:06, 3 December 2010 (UTC)
- Sigma-Aldrich doesn't list a color in their MSDS for bismuth(III) iodide, but here are a couple of others offering up gray, dark grey, or red(?)(!). My rubber bible (76th ed.) says 'black hexagonal crystal'. A cursory search doesn't reveal any suggestion that bismuth iodide can form two different solid phases under normal conditions, but I can't rule it out.
- My strong suspicion is that this is a dark-gray-to-black (faintly colored under appropriate lighting) crystalline material, and that our article contains errors. It looks like all of the bismuth(III) halide salts (with the exception of the fluoride) were photographed by the same individual as part of a large batch of similar images; one wonders if he made – or was the victim of – an inadvertent labelling error. TenOfAllTrades(talk) 15:01, 3 December 2010 (UTC)
Parrots cracking bones to get the marrow...
(Matt Deres' answer to the 'human hunting' question above got me thinking) If you give a bone (say, a chicken leg) to a parrot - video example, it will eat the meat and then may decide to crack the bone open to eat the marrow inside.
Do they actually do this in the wild? Parrots are not generally predatory, so I'd assume that any bones they'd find to gnaw on in the wild would have to come from scavenged carcasses. --Kurt Shaped Box (talk) 19:06, 3 December 2010 (UTC)
- I seem to recall that some birds, and parrots specifically, have trouble getting all the minerals they need in their normal diet, so will resort to doing odd things like eating clay. Getting the iron out of bone marrow might also be normal for them. StuRat (talk) 04:35, 4 December 2010 (UTC)
- Might not the cracking of the bone be a normal behaviour to be expected of seed eating birds. If you give anything to a parrot one of the first investigatory procedures is to give it a good going over with its beak. It is conceivable that the parrot assumes the bone is just another seed which needs to be cracked open and the contents consumed. Richard Avery (talk) 08:36, 4 December 2010 (UTC)
- According to our article on parrots, they eat clay because it "both releases minerals and absorbs toxic compounds from the gut". It also mentions that some parrots are predators, noting in particular the hunting habits of keas, the Antipodes Island Parakeet, and Golden-winged Parakeets. I did a quick Google search for the original question and found a quote from a book called Veterinary Nursing by D. R. Lane, B. Cooper (I can't even get a proper preview): "Most of the large parrots are omnivorous in the wild, eating a mixture of fruit, vegetables and seeds, plus insects and carrion..." and the rest is cut off. Hopefully, someone can get a proper reference for us. Matt Deres (talk) 19:46, 4 December 2010 (UTC)
is it a coincidence that there are 12 months and 12 hours?
is it a coincidence that there are twelve months in the year and twelve hours in the day (a.m. or p.m.) or is it one of nature's beautiful symmetries? 82.234.207.120 (talk) 20:53, 3 December 2010 (UTC)
- One wikipedia reference is 12-hour clock, which mentions the antiquity of the system. Precisely why 12 and not 10 is unclear, but I can imagine some reasons for it. There might be more detailed info elsewhere. There should be something in Calendar about 12 months in the year, but that was not a uniform standard. Lunar calendars typically have 12 lunar months (or "moons") within a given year rather than using the 30-31 system, and they catch up by adding a 13th month every few years. ←Baseball Bugs What's up, Doc? carrots→ 21:07, 3 December 2010 (UTC)
- Months as we know them now are based (loosely/approximately) on "lunar cycles per year"...that's Nature's doing. But there have not always been 12 anyway. The division of a day into hours is completely a human invention (and aren't there actually 24 of them?). The most plausible story I usually hear is that it allows many different subdivisions without getting wacky fractions (10 only allows 10/5/2/1 whereas 12 allows 12/6/4/3/2/1). DMacks (talk) 21:19, 3 December 2010 (UTC)
- Phrased another way, 12 is related to a factorial (4!) while 10 is not. This is true in any number-notation system, so even if ancient clock-makers did not use a base-10 numeral system, they still would have understood a special significance for the value "12". "10" only seems like a special number when we use a decimal number-system; it has no real natural significance (other than equaling the most common number of fingers on humans). You might be interested in Sexagesimal (base-60) numerals that were used by ancient Babylonians and Sumerians - there are 24 (4!) hours in a day for a similar reason; 60 minutes in an hour; 360-degrees in a circle, and so on. Nimur (talk) 21:28, 3 December 2010 (UTC)
- Note that decimal time and months were implemented during the French Revolution, but did not catch on broadly and even in France were eventually eliminated. In any case, as all have stated, the divisions are arbitrary (with the exception of the number of rotations of the Earth in a year, which is a constant—if you don't get the number of days in a year right, your seasons won't match up on a calendar from year to year), but different systems allow you to do different types of calculations more easily. --Mr.98 (talk) 04:01, 4 December 2010 (UTC)
- The fixed periods in nature, visible from Earth, are the day, periods between tides, lunar month (not what we call a month), year, and perhaps seasons (4 divisions of a year between solstices and equinoxes). Others, like a sunspot cycle of 11.2 years or Halley's Comet cycle of 76 years, could also be included, but are less important to our everyday lives. StuRat (talk) 04:33, 4 December 2010 (UTC)
- The easy divisibility of 12 into various fractions is also probably why there were 12 inches in a foot. Just one more example of the superiority of the old English system. :) ←Baseball Bugs What's up, Doc? carrots→ 04:59, 4 December 2010 (UTC)
- You might want to check out the Dozenal Society. See also Duodecimal#Advocacy_and_.22dozenalism.22. There are a lot of good reasons to go base twelve. Too bad our ansectors ended up with 10 fingers and developed our utterly impractical base 10 system (how often do you find yourself happy that it's easy to divide by 5? I'd take the factor of 3 any day. The extra factor of 2 is nice as well). Buddy431 (talk) 05:51, 4 December 2010 (UTC)
- Edit: If your British, you might prefer to align yourself with the DSGB. Of course, not everyone is happy with these upstarts. Buddy431 (talk) 05:52, 4 December 2010 (UTC)
- I can't find a reference right now, but base-12 counting systems are also based on counting on the fingers. Not counting your thumb; you have 12 knuckles on each hand. Using your thumb as a "place holder" on each knuckle enables easy counting in base-12. I read somewhere that the connection to the 24 hour day and all of our other base-12 derived time units derive from counting in base-12 in this manner. Two sketchy sources which confirm this are here and here, see the second response.. --Jayron32 06:22, 4 December 2010 (UTC)
- I'm amazed that no one has mentioned the Zodiac yet. While I'm speculating here, and I don't know if the historical truth can be determined, but consider that someone using a lunar month, the most obvious division, is going to see the sun or a full moon turn up in about 12 different places in the sky in a year. This leads naturally to the idea of identifying what time of year it is based on which of 12 astrological signs the sun and/or moon are located in. Such a basic astrology is indeed useful in predicting one's success when planting crops!
- Now it is also possible to divide a day according to the rising sign, though admittedly this yields 12 units rather than 24, and the time of day at which a constellation rises varies during the year. Still, I'm suspicious of some sort of link. Wnt (talk) 11:42, 4 December 2010 (UTC)
- I can't find a reference right now, but base-12 counting systems are also based on counting on the fingers. Not counting your thumb; you have 12 knuckles on each hand. Using your thumb as a "place holder" on each knuckle enables easy counting in base-12. I read somewhere that the connection to the 24 hour day and all of our other base-12 derived time units derive from counting in base-12 in this manner. Two sketchy sources which confirm this are here and here, see the second response.. --Jayron32 06:22, 4 December 2010 (UTC)
- Edit: If your British, you might prefer to align yourself with the DSGB. Of course, not everyone is happy with these upstarts. Buddy431 (talk) 05:52, 4 December 2010 (UTC)
- You might want to check out the Dozenal Society. See also Duodecimal#Advocacy_and_.22dozenalism.22. There are a lot of good reasons to go base twelve. Too bad our ansectors ended up with 10 fingers and developed our utterly impractical base 10 system (how often do you find yourself happy that it's easy to divide by 5? I'd take the factor of 3 any day. The extra factor of 2 is nice as well). Buddy431 (talk) 05:51, 4 December 2010 (UTC)
- The easy divisibility of 12 into various fractions is also probably why there were 12 inches in a foot. Just one more example of the superiority of the old English system. :) ←Baseball Bugs What's up, Doc? carrots→ 04:59, 4 December 2010 (UTC)
Sail and oar power
Why exactly were oars abandoned for sail power? Was it to make room for more cannons? It seems that something more like a Galleass would be the best combination, being able to head straight into the wind without tacking. --T H F S W (T · C · E) 21:05, 3 December 2010 (UTC)
- Galley might provide some answers. Galleys in fact had sails. Oarsmen provided better maneuverability. ←Baseball Bugs What's up, Doc? carrots→ 21:16, 3 December 2010 (UTC)
- Exactly. So why were they given up? --T H F S W (T · C · E) 21:23, 3 December 2010 (UTC)
- Well, you can reduce the crew size if you are not going to be rowing a lot. That means you can go further before you need to take on more provisions. Googlemeister (talk) 21:30, 3 December 2010 (UTC)
- According to the "Decline" section of that article, they basically went obsolete as new technologies came along. ←Baseball Bugs What's up, Doc? carrots→ 21:33, 3 December 2010 (UTC)
- This is the second essentially tautological answer you've given in as many days on here, Bugs! "Why was a technology phased out? Because new technologies made it obsolete." Reeeeally, now? --Mr.98 (talk) 04:06, 4 December 2010 (UTC)
- Also oar power requires a flat design that makes ships very vulnerable to storms. Looie496 (talk) 22:27, 3 December 2010 (UTC)
- I think that's the same reason as Bugs gave (the newer ships could cope with rough seas). The OP was talking about something like a galleass, though. That's not the same as a galley, and it's not flat, so why isn't it the best of both worlds? I can't see the drawback of having oars as an option (even if they're not very efficient because they're positioned high up). The galleass article says Henry VIII built a lot of them, and then a couple of decades later had all their oars removed and turned them into pure sailing ships, but it doesn't say why. 81.131.6.177 (talk) 22:37, 3 December 2010 (UTC)
- All those oarsmen had to eat, drink and sleep the whole time the galley or galeass was in commission, so the crews were expensive, particularly if they were serving willingly. A galley or galeass consequently was a short-ranged vessel that had to stay close to a convenient port or risk starvation, and had little room left for more than a couple of guns. They were also quite lightly built in order to keep oar propulsion within the realm of possibility. I suspect that Henry's ships were slugs under oar power. After naval guns were refined a little bit (around Henry's time) a moderately well-armed sailing ship could sink a galley from a distance with little trouble as long as the wind was favorable; oar power was only an advantage in close quarters or an unfavorable wind. Acroterion (talk) 00:04, 4 December 2010 (UTC)
- It occurred to me that the manpower requirements made galleys not cost-effective compared with newer technologies, but the article is kind of vague on that issue. ←Baseball Bugs What's up, Doc? carrots→ 01:19, 4 December 2010 (UTC)
- I see that the Girona (ship) made it all the way from Spain to Ireland, the long way round, and had 1300 people on board when she sank (plenty more than the 370 I estimate it would take to man the oars), but I think that voyage was largely accidental, so fair enough. Also the ships illustrated in the Galleass article have (it looks like) 18 and 22 guns, which is more than a couple, but hey, good points anyway. (Perhaps they're very small guns.) 81.131.39.230 (talk) 01:29, 4 December 2010 (UTC)
- All those oarsmen had to eat, drink and sleep the whole time the galley or galeass was in commission, so the crews were expensive, particularly if they were serving willingly. A galley or galeass consequently was a short-ranged vessel that had to stay close to a convenient port or risk starvation, and had little room left for more than a couple of guns. They were also quite lightly built in order to keep oar propulsion within the realm of possibility. I suspect that Henry's ships were slugs under oar power. After naval guns were refined a little bit (around Henry's time) a moderately well-armed sailing ship could sink a galley from a distance with little trouble as long as the wind was favorable; oar power was only an advantage in close quarters or an unfavorable wind. Acroterion (talk) 00:04, 4 December 2010 (UTC)
- I think that's the same reason as Bugs gave (the newer ships could cope with rough seas). The OP was talking about something like a galleass, though. That's not the same as a galley, and it's not flat, so why isn't it the best of both worlds? I can't see the drawback of having oars as an option (even if they're not very efficient because they're positioned high up). The galleass article says Henry VIII built a lot of them, and then a couple of decades later had all their oars removed and turned them into pure sailing ships, but it doesn't say why. 81.131.6.177 (talk) 22:37, 3 December 2010 (UTC)
- According to the "Decline" section of that article, they basically went obsolete as new technologies came along. ←Baseball Bugs What's up, Doc? carrots→ 21:33, 3 December 2010 (UTC)
- Well, you can reduce the crew size if you are not going to be rowing a lot. That means you can go further before you need to take on more provisions. Googlemeister (talk) 21:30, 3 December 2010 (UTC)
- Exactly. So why were they given up? --T H F S W (T · C · E) 21:23, 3 December 2010 (UTC)
Patrick O'Brian discussed the issues of sail vs. oar extensively in the Aubrey–Maturin series, and while that was a work of fiction, it was based on years of O'Brian's readings of logbooks and everything naval he could find. It was not uncommon for small ships, say sixth-rates to have sweeps - long oars to help move the ship in an emergency or for convenience, even in Napoleonic times. Anything bigger than, say 200 tons, though, was impossible to move by oar power. Galleys draw little water and displace at most couple of hundred tons. A 400-700 ton fifth-rate was not moveable by means other than wind or towing. A galeass was probably right on the edge of being too big to move by oar and not built heavily enough to carry heavy guns; as the article notes, they evolved into fifth and sixth-rates: frigates. In the 17th century a nine-pounder (maybe weighing a ton) was a big gun, by the 18th century ships were carrying 24-pounders, and by the 19th a third-rate ship of the line carried 32-pounders (6000+ lb each) and was built to stand in a line of battle and beat the hell out of a counterpart a couple of hundred yards away, and to receive the same. Galleys couldn't possibly do that, nor could they raid an enemy's commerce more than a hundred miles from their home port, or stay at sea blockading an enemy port for months on end. In any case, galleys and galeasses spent most of their time sailing, only using oars when becalmed or when it gained a tactical advantage. They were sprinters and bantamweights; sailing ships were both distance runners and heavyweights, to mix sports analogies. Acroterion (talk) 02:55, 4 December 2010 (UTC)
- So in other words, if a ship displaces too much water, it is immovable by oars (which would be the reason galleys would have flat bottoms)? And about the argument about the extra crew: as already pointed out, a large ship would have well over 300 men aboard, so there would be plenty to row. One more question: can a galley be made more stable by adding a very large keel? --T H F S W (T · C · E) 22:10, 4 December 2010 (UTC)
- The more a ship displaces, the more power needed to move it. "Plenty to row" is not necessarily so: if we assume that a man can produce 1/4 horsepower for a short period of time (which is probably generous), for less than an hour, you have at most a 75 horsepower engine to move several hundred tons for a short time. You can sail a fairly large ship indefinitely with thirty men, leaving plenty left over for guns and boarding actions. Oars aren't an efficient means of propulsion, and need room inside the ship that could be devoted to armament and cargo. If you want to fight, you'll need four to eight men per gun, who won't be available to row. 20 guns will need 80-160 men to serve them (although if you only wish to fight one side at a time you can have the crews run to the other side), plus powder boys and gunner's mates to fill cartridge and carry shot. Keels weren't very common on large ships, as they already drew a substantial quantity of water and didn't need something that could be scraped off - or worse sticking out from the bottom. While a keel will add some stability, it's more useful for countering leeway (the tendency for a sailing ship to slide sideways in a wind from the side), and is hard to construct durably in a large wooden ship. Ballast was used to lend stability, which again adds mass; I don't see any advantage to much ballast or a keel in a rowed vessel. The big advantage a galley had that a sailing ship didn't was an ability to accelerate rapidly and to maneuver, turning in its own length, which heavy ballast or a big fin would diminish. Think of racing shells - long, slender and and displacing virtually nothing. Galleys would use swarming tactics against sailing ships, and would decline a one-on-one action unless there was no wind, which is a fairly rare circumstance near the shore. Acroterion (talk) 02:38, 5 December 2010 (UTC)
if all small arms and heavier munitions disappeared, would the world be a safer place?
if all small arms everywhere in the world instantly disappeared (and for whatever reason could not be reproduced), along with all munitions heavier than small arms, would the world be a safer place, or less safe for some reason I'm not imagining clearly? 82.234.207.120 (talk) 23:09, 3 December 2010 (UTC)
- It's quite often argued that higher weapons technology makes wars shorter. In this particular case, we'd return to fighting wars with bows and arrows and swords. Larger armies would be needed, which would fight more chaotically and take longer to kill the enemy, causing more starvation and disease for civilians near the battles. Also being clubbed to death is not really any safer than being shot. 81.131.6.177 (talk) 23:24, 3 December 2010 (UTC)
- This is really more of a humanities question, unless you are wondering by what process this instant disappearance could occur. That said, maybe some arguments in this article (and related ones) might interest you: Political arguments of gun politics in the United States. The US has a long history of just this sort of debate, and there are a number of arguments on both sides of the aisle that could offer some insight. TomorrowTime (talk) 23:34, 3 December 2010 (UTC)
- This is also a speculative question, so we can't really answer it definitively. But you might find the sociological research published by various think-tanks like the Brookings Institute, the Hoover Institute or the RAND Corporation worth reading. Arguably, some of these institutes espouse a right-wing "neoconservative" philosophy that advocates more low intensity warfare as a means to ensure less high-intensity warfare overall. You can search their published archives to find their official policy advisories related to, for example, arms control, firearm legislation, and so forth. While I don't necessarily agree with many of the published opinions of these organizations, they have a knack for recruiting some of the greatest political and military minds in the world, and their publications are often extremely well-researched. Food for thought, if not a prescriptive panacea for global policy. Nimur (talk) 23:37, 3 December 2010 (UTC)
- I think a look outside the USA is important on this one. Australia has always had much lower gun ownership than the USA. After the Port Arthur Massacre in 1996 the laws about gun ownership became considerably tougher. The vast majority of Australians don't own guns. And by most measures it is a safer place than the USA. I know there will be many other factors at play, but it's an interesting starting point for discussion. HiLo48 (talk) 23:42, 3 December 2010 (UTC)
- Right - there's a sort of spectrum of "danger" ranging from chronic criminal activity all the way to military armed conflict. Depending on your school of thought, this distinction between crime and war is either a continuum of magnitude, or two unrelated issues. Nimur (talk) 23:51, 3 December 2010 (UTC)
- Look at how certain African countries have suffered with the machete as the principal terror. 75.41.110.200 (talk) 00:14, 4 December 2010 (UTC)
- I'd love to look, but where? HiLo48 (talk) 00:16, 4 December 2010 (UTC)
- Another example is the UK, where per capita murders are a tiny fraction of those in the US. The answer to the OPs question is, yes of course it would. 92.15.20.70 (talk) 00:18, 4 December 2010 (UTC)
- How do murders in the UK compare before and after gun control came in? But of course the answer to that question wouldn't conclude the argument ... and neither would any other example, because we can endlessly claim special circumstances and confounding factors (which may or may not be really present). 81.131.6.177 (talk) 00:43, 4 December 2010 (UTC)
- The per capita murder rate in the UK is nearly a quarter of the rate in the US - List of countries by intentional homicide rate. For gun killings its bound to be even more dramatic than that. "After gun control came in" - guns are very rare in the UK. I've only seen one twice in my life - both shotguns used in the countryside. 92.24.177.111 (talk) 12:23, 4 December 2010 (UTC)
- How do murders in the UK compare before and after gun control came in? But of course the answer to that question wouldn't conclude the argument ... and neither would any other example, because we can endlessly claim special circumstances and confounding factors (which may or may not be really present). 81.131.6.177 (talk) 00:43, 4 December 2010 (UTC)
- Prohibition doesn't work. If someone wants to kill, they'll find a way. The issue isn't guns, the issue is why do people use them? Fix that, and the guns problem fixes itself. ←Baseball Bugs What's up, Doc? carrots→ 00:53, 4 December 2010 (UTC)
- Someone who wants to kill from short term anger will usually calm down over time. The lack of a suitable tool for easy killing during that period will prevent killing from happening. Time is a wonderful healer. If a gun is readily available that healing won't happen. HiLo48 (talk) 01:10, 4 December 2010 (UTC)
- No question it's too easy for a hothead with a gun to use that gun. But gun ownership, within certain limitations, is written into the U.S. Constitution, and that's not likely to change anytime soon. What the OP is wanting is something like when the Organians worked it so the Federation and the Klingons were rendered incapable of using their weapons and were compelled to sign a truce. Divine intervention, effectively. Real life doesn't work that way, and as long as someone has something that someone else wants, wars and violence will continue. ←Baseball Bugs What's up, Doc? carrots→ 01:17, 4 December 2010 (UTC)
- Since we're in the science section, I'd have to ask whether the ban on "small arms" extends to the gyrojet, crossbows, flame-throwers, RPGs... because a world where none of these mechanisms work has very different physics indeed. I suppose if you ruled people were indestructible then they wouldn't get hurt, but then enemy soldiers could just walk up to them, chain them up, and toss them down very deep holes to spend a dull eternity. Wnt (talk) 01:33, 4 December 2010 (UTC)
- I feel the need to trot out the familiar old argument (it needs a bit of exercise now and again) that laws against gun ownership, by definition, prevent law abiding people from having guns, while murderers, by definition, are not law abiding. (This doesn't actually contradict what you just said; without gun laws, generally well-meaning hotheads sometimes shoot people, and with them, innocents are unarmed while gangsters still have guns.) 81.131.39.230 (talk) 01:40, 4 December 2010 (UTC)
- ....in the USA. And that's the point. In countries without a gun culture, there are just simply fewer guns. It's still harder for criminals to get them. The big worry in my Australian city right now is not guns. It's the claim by the righteous media that there is a growing number of youths with knives. (Anyone remember Romeo and Juliet?) Knives, of course, aren't normally deadly unless you're very close to the victim. Guns are deadly from a long way away. The best response I've heard to Americans quoting their constitutional right to bear arms is that it should be restricted to the types of arms available when that right was created. HiLo48 (talk) 02:10, 4 December 2010 (UTC)
- In my past life in the London insurance market I used to see the claims for the American National Rifle Association's accident policies and can say that the world would definitely be safer without guns, especially in people's homes. "I forgot it was loaded", "the trigger got caught on a coat hook", "my son / daughter /wife / neighbour / cat / dog was playing with it" and so on. It's a bloodbath out there! Alansplodge (talk) 02:41, 4 December 2010 (UTC)
- re: "it's a bloodbath out there!" Just out of curiousity, have you ever gotten a claim where nothing happened at all? If not, you might want to read about selection bias before armageddon! 82.98.48.252 (talk) 15:25, 4 December 2010 (UTC)
- I wonder how the rifle claims compare quantitatively with claims connected with automobiles. If anything, it's the car that should be banned. ←Baseball Bugs What's up, Doc? carrots→ 16:54, 4 December 2010 (UTC)
- re: "it's a bloodbath out there!" Just out of curiousity, have you ever gotten a claim where nothing happened at all? If not, you might want to read about selection bias before armageddon! 82.98.48.252 (talk) 15:25, 4 December 2010 (UTC)
- If people were reduced to hand-to-hand combat, that would favor the nations with the largest populations, such as China and India, which would probably split Asia between them. Perhaps if all the Europeans worked together, they could stop the Chinese from advancing into Europe. StuRat (talk) 04:20, 4 December 2010 (UTC)
- That's where bombs come into the picture. ←Baseball Bugs What's up, Doc? carrots→ 04:54, 4 December 2010 (UTC)
- Wouldn't bombs be counted under 'munitions heavier than small arms'? On the other hand it's not clear to me that some kinds of chemical weapons and particularly biological weapons would count as 'munitions heavier than small arms' Nil Einne (talk) 07:59, 4 December 2010 (UTC)
- Let's not forget fire. In a country with gun control, one can always chain the doors to the ex's tenement and throw in a few Molotov cocktails; it has the added advantage that the police would have many suspects to consider. Likewise a war can be fought with fire balloons, "bat bombs" [incendiaries, that is], and the ever-handy flame thrower. Wnt (talk) 11:51, 4 December 2010 (UTC)
- You could buy a gallon or two of gasoline and use it to burn down a building. Violence always finds a way. ←Baseball Bugs What's up, Doc? carrots→ 16:55, 4 December 2010 (UTC)
- Let's not forget fire. In a country with gun control, one can always chain the doors to the ex's tenement and throw in a few Molotov cocktails; it has the added advantage that the police would have many suspects to consider. Likewise a war can be fought with fire balloons, "bat bombs" [incendiaries, that is], and the ever-handy flame thrower. Wnt (talk) 11:51, 4 December 2010 (UTC)
- Wouldn't bombs be counted under 'munitions heavier than small arms'? On the other hand it's not clear to me that some kinds of chemical weapons and particularly biological weapons would count as 'munitions heavier than small arms' Nil Einne (talk) 07:59, 4 December 2010 (UTC)
- That's where bombs come into the picture. ←Baseball Bugs What's up, Doc? carrots→ 04:54, 4 December 2010 (UTC)
Do you mean small arms in private homes or small arms for the military? --Stone (talk) 17:28, 4 December 2010 (UTC)
December 4
Camera error
Recently, after having not been used due to a low battery for a couple of months, my Canon PowerShot SD790 IS camera started to malfunction. After I charged the battery, upon attempting to use the camera, the pictures would sometimes come out like the first picture in the gallery below.
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Picture with error.
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Picture of same area, but without the error.
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Picture six days later with severe error.
The error at that point was intermittent, as a few seconds later I was able to take a picture of the exact same area without a malfunction (the second picture). However, over the next few days, the malfunction kept getting worse, until six days later the third picture resulted from an attempt to take a picture of my television on a wooden table in a well-lit room. What could this camera malfunction be, and what are some ways that it could possibly be fixed?
PS: Note that this is not exactly an urgent or necessary inquiry, as I received a replacement camera as a birthday gift a couple days ago. A mere pointer to what the error is called and what causes it would be a suitable answer for me.
Thanks in advance, Ks0stm (T•C•G) 05:30, 4 December 2010 (UTC)
- Maybe the (rechargable?) battery needs replacing. Side question - why is there a traditional red British phone box at the University of Oklahoma? Thanks 92.24.177.111 (talk) 12:33, 4 December 2010 (UTC)
- As to the phone box, apparently it's just a phone box. What, did you think there wouldn't be an article on it? :-) 88.112.56.9 (talk) 14:20, 4 December 2010 (UTC)
- Very good. I've taken the liberty of adding the middle photo above to that article's gallery, since it's mentioned in the text but not attributed. If the OP could take a nice close-up of the phone box, that would be even better. :) ←Baseball Bugs What's up, Doc? carrots→ 16:43, 4 December 2010 (UTC)
- The first pic looks like the green component isn't being recorded. In the last pic, the same thing is true, but also the darkness seems to indicate that the other components are now recorded at reduced levels (it looks like only one line of red and one of blue is recorded for every 8 or so lines of data, so you have 1/8th the normal level of those colors). Does your camera have a gray-scale setting ? If so, you might still be able to get a usable pic in a bright setting. As for the cause, I don't know, perhaps some electrical contacts are broken and now have only an intermittent connection ? Is it out of warranty ? StuRat (talk) 16:06, 4 December 2010 (UTC)
- For a real mystery, where did the tree at the left, top of the 1st pic go, in the 2nd pic ? StuRat (talk) 16:21, 4 December 2010 (UTC)
- The answer is that the middle picture was taken from maybe 20 or 30 feet farther to the right. Open two sessions and note the shift of background objects, such as the phone booth, and also that the small leafless tree in the foreground of the middle shot is the small then-leafed tree in the left picture. ←Baseball Bugs What's up, Doc? carrots→ 16:26, 4 December 2010 (UTC)
- I don't think it is then-leaved, I think it is still unleaved in the picture on the left but then in front of the needled pine tree behind it. WikiDao ☯ (talk) 16:34, 4 December 2010 (UTC)
- You're right. I was confusing it with the tree that's right behind it in the line of sight. In any case, the middle picture was taken from a position farther to the right than the left picture was. Or to make it less confusing, the left picture was taken from farther left than was the middle picture. Another telltale sign is the driveway, clearly visible in the left picture, just a smidgen of it visible in the middle picture. ←Baseball Bugs What's up, Doc? carrots→ 16:36, 4 December 2010 (UTC)
- I don't think it is then-leaved, I think it is still unleaved in the picture on the left but then in front of the needled pine tree behind it. WikiDao ☯ (talk) 16:34, 4 December 2010 (UTC)
- The answer is that the middle picture was taken from maybe 20 or 30 feet farther to the right. Open two sessions and note the shift of background objects, such as the phone booth, and also that the small leafless tree in the foreground of the middle shot is the small then-leafed tree in the left picture. ←Baseball Bugs What's up, Doc? carrots→ 16:26, 4 December 2010 (UTC)
- If you look at those photos full-size, and especially if you zoom in, there's definitely a problem in the first photo, which looks as if it were taken through a screen door. Getting a new camera was probably more cost-effective than getting it repaired, though it might be worth it to take the camera and the evidence to a camera shop and see if they have any theories. ←Baseball Bugs What's up, Doc? carrots→ 16:49, 4 December 2010 (UTC)
- Comment. The modern consumer digital-camera flow path consists of dozens, or even hundreds, of image-processing stages that convert the image from the physical world to JPEG format. Without elaborate blueprints of the innards of the ASICs and software processes, we can only speculate what might be going wrong. I suspect there is at least a mechanical shutter problem, or possibly a sensor problem, based on the varied exposure patterns in the corrupted images. These have the hallmark of a CCD sensor's multi-field readout, with the later fields over-exposed (because the shutter never closed and new incident light kept coming in). PowerShot SD790 (like most Canon cameras) uses a bayer-masked CCD; if mechanical shutter broke the exposure, the demosaicing algorithm could be misconfigured. Similar field readout errors could be caused by insufficient power to the sensor, too. If the image readout doesn't match the expected exposure level, subsequent inputs to image-processing stages would be poorly configured based on the disparity between intended and actual image characteristics, and would explain the color-clobbering and other weird glitches. But, we can't know: there could be significant additional software- and hardware- image processing, filtering, and so on. Any software or hardware error in these steps could corrupt the image. Low battery may cause brownout; that could account for the shutter failure or electronics/software errors. Nimur (talk) 22:18, 4 December 2010 (UTC)
What kind of simutaneity make sense?
Currently there are three kinds of Simutaneity theories. The most popular one is that simutaneous events may lost their simutaneity if observed by observers in different inertial system when their relative speed is v>0. A famous case described it like followings, two lightnings hit two ends of a moving box at the same time, then, to the person at the center of that box, two events are not simutaneous. Logically speaking, this can happen; but, if we have a lot of observers in the moving system, not just one at the center of that box, then what will happen? Do you know a better case to explain this popular theory?Jh17710 (talk) 06:28, 4 December 2010 (UTC)
- The second theory is the classic idea. It states, simutaneous events will keep their simutaneity to observers in any inertial system. The calssic case is, if two baseballs are hit at the same time to virtical and 45 degree angle but reach ground at the same time, then to observers in other inertial system, actual paths of two basealls may show different angles but two baseballs will always reach ground at the same time. When we have a lot of observers in any given inertial system, then, this theory will maintain physical laws in between inertial systems. We like physical laws be maintained in inertial systems, right?Jh17710 (talk) 06:28, 4 December 2010 (UTC)
- The third theory is a visual version based on the second theory. Two simutaneous events will keep their simutaneity to observers keeping same distance from both event locations, starting the actual event time up to the recorded event time. The attached condition will explain the first case naturally, the observer moves to a location closer to the front event point before the observer record the event time so that the observed event times are different. The third theory also claims that two simutaneous events can be recorded different event times even in the same system if distances to two event locations are different.Jh17710 (talk) 06:28, 4 December 2010 (UTC)
- Above analysis is to show that the simutaneity is distroyed by different distance, not by different speed.Jh17710 (talk) 06:28, 4 December 2010 (UTC)
- The third theory is a visual version based on the second theory. Two simutaneous events will keep their simutaneity to observers keeping same distance from both event locations, starting the actual event time up to the recorded event time. The attached condition will explain the first case naturally, the observer moves to a location closer to the front event point before the observer record the event time so that the observed event times are different. The third theory also claims that two simutaneous events can be recorded different event times even in the same system if distances to two event locations are different.Jh17710 (talk) 06:28, 4 December 2010 (UTC)
- No, only the first case is experimentally verfied; simultaneity is only preserved for observers in the same reference frames. If we have observer A and observer B, event C and event D. If A and B are moving at different speeds, and C and D are at some distance from each other, if C and D are simultaneous in A's view, they will likely not be in B's system. This is due to the relativity of simultaneity, which is a direct consequence of the experimentally verified theory of special relativity. Your other two examples don't make any sense given what currently accepted theories explain about how the world works. --Jayron32 07:08, 4 December 2010 (UTC)
- Thanks for your time. Could you show me which experiment verified it? In your case of two observers A and B, could you provide more detail regarding what kind of tools they use to measure the event times of C and D? How they record each of the event times? By camcorders, by eyes and clocks, or what kind of device? If by eyes and clocks, our vision rely on lights to carry the picture of events C and D to our eyes so that we know what happen at what time, am I correct? If C and D are rest in A's frame, assume that all clocks at the location of C, D, and A are all synchronized, then, for observer Oc at event location of C, Pc, and Od at event location of D, Pd, will record different event time if the location of A, Pa, is different from the locations of C and D, am I correct?Jh17710 (talk) 15:35, 4 December 2010 (UTC)
- Now go back to your claim {..if C and D are simultaneous in A's view, they will likely not be in B's system.}, but this time let we study it with distance in mind. If observer A is located at point Pa, we also assume that observers Oc and Od recorded same event time, Tc=Td, then C and D are simutaneous in A's view when distance PaPc=PaPd. If Tc=Td, but PaPc>PaPd, then A will record event C happens later than event D. For B, if B moves on the plan perpendiculer to the line segment PcPd at the middle point of it, then, B will always record that C and D are simutaneous no matter how B moves. Don't you think so?Jh17710 (talk) 15:35, 4 December 2010 (UTC)
- Without going into the math in scrupulous detail; yes there are situations where two observers moving at different velocities can both record two events as simultaneous; however this is merely a geometry problem and not a physics one. It is possible to construct paths through spacetime whereby A and B are moving in different reference frames and both measure C and D as simultaneous. Imagine a similar, related problem from the world of geometry. If I place two points on a piece of paper, they are required to be colinear. A third point can be placed that is sometime colinear with the other two; but does not have to be. Imagine Event C and Event D as the two points. If I place observer A on the paper on the line made by Event C and Event D, they will agree that they line up. If I place observer B on the paper also somewhere on the same line, they will also agree that they line up. However, if I place observer B on the paper somewhere NOT on the line, they will observe the two points (relative to B's position) to not be colinear. They can extrapolate a line whereby C and D are colinear, but they will also recognize that they are NOT on this line. It's the exact same situation in special relativity. Imagine these lines happening in 4D spacetime rather than on a piece of paper; we call these lines worldlines, but they obey the same basic rules of geometry that all lines do. We just have 4D spacetime as our paper. Your postulates regarding perpendicular movement and the observation of similtaneity of events is an unsurprising consequence of basic geometry, and has no bearing on the reality of special relativity; in fact it confirms it rather than refutes it. Your other two examples are still wrong. --Jayron32 15:51, 4 December 2010 (UTC)
- I know it will reach spacetime, sooner or later. The definition of the distance between an event and the origin point of the spacetime is man made. That definition is for the purpose of matching the equation of SR, t'=t/γ, period. You cannot prove SR by SR related theory. We have a lot of different way to define the distance of an event and the origin point of spacetime, if space and time can be put together to make a useful 4 dimensional structure. Whether our universe is Euclidean or not, is still a question. Within all kinds of force fields, it is hard to find a series of events moving at constant velocity, but that fact does not disprove an Euclidean universe.Jh17710 (talk) 16:40, 4 December 2010 (UTC)
- Oh, and to answer your first question, the article Status of special relativity discusses these experiments in some detail. --Jayron32 15:58, 4 December 2010 (UTC)
- There are some, but, could you briefly describe the one you think is the best, and the reason? Thanks.Jh17710 (talk) 16:40, 4 December 2010 (UTC)
- Without going into the math in scrupulous detail; yes there are situations where two observers moving at different velocities can both record two events as simultaneous; however this is merely a geometry problem and not a physics one. It is possible to construct paths through spacetime whereby A and B are moving in different reference frames and both measure C and D as simultaneous. Imagine a similar, related problem from the world of geometry. If I place two points on a piece of paper, they are required to be colinear. A third point can be placed that is sometime colinear with the other two; but does not have to be. Imagine Event C and Event D as the two points. If I place observer A on the paper on the line made by Event C and Event D, they will agree that they line up. If I place observer B on the paper also somewhere on the same line, they will also agree that they line up. However, if I place observer B on the paper somewhere NOT on the line, they will observe the two points (relative to B's position) to not be colinear. They can extrapolate a line whereby C and D are colinear, but they will also recognize that they are NOT on this line. It's the exact same situation in special relativity. Imagine these lines happening in 4D spacetime rather than on a piece of paper; we call these lines worldlines, but they obey the same basic rules of geometry that all lines do. We just have 4D spacetime as our paper. Your postulates regarding perpendicular movement and the observation of similtaneity of events is an unsurprising consequence of basic geometry, and has no bearing on the reality of special relativity; in fact it confirms it rather than refutes it. Your other two examples are still wrong. --Jayron32 15:51, 4 December 2010 (UTC)
- Now go back to your claim {..if C and D are simultaneous in A's view, they will likely not be in B's system.}, but this time let we study it with distance in mind. If observer A is located at point Pa, we also assume that observers Oc and Od recorded same event time, Tc=Td, then C and D are simutaneous in A's view when distance PaPc=PaPd. If Tc=Td, but PaPc>PaPd, then A will record event C happens later than event D. For B, if B moves on the plan perpendiculer to the line segment PcPd at the middle point of it, then, B will always record that C and D are simutaneous no matter how B moves. Don't you think so?Jh17710 (talk) 15:35, 4 December 2010 (UTC)
- Thanks for your time. Could you show me which experiment verified it? In your case of two observers A and B, could you provide more detail regarding what kind of tools they use to measure the event times of C and D? How they record each of the event times? By camcorders, by eyes and clocks, or what kind of device? If by eyes and clocks, our vision rely on lights to carry the picture of events C and D to our eyes so that we know what happen at what time, am I correct? If C and D are rest in A's frame, assume that all clocks at the location of C, D, and A are all synchronized, then, for observer Oc at event location of C, Pc, and Od at event location of D, Pd, will record different event time if the location of A, Pa, is different from the locations of C and D, am I correct?Jh17710 (talk) 15:35, 4 December 2010 (UTC)
- Specifically the other two examples seem to rely upon some kind of universal time which transcends the reference frame ("same time", "recorded event time"), when the relativity of simultaneity is, in fact, an indication of (and consequence of) the lack of any universal time. --Mr.98 (talk) 15:07, 4 December 2010 (UTC)
- You are absolutely correct about what SR claims, no universal time. However, that is just a claim, a hypothesis, isn't it? Theoretically, we have some way to calculate the absolute TIME PERIOD by counting the wave peaks from a known frequency souce of light or EM wave emitter at fixed distance. The formula is very simple, total wave peaks, N, times the wave length, L, then divides by the speed of light, c; time period between event C and D is Tcd=NL/c. That means, we can prove that time period is the same for rest and moving observers, theoretically. In his book published 9-1-2010, ZhiZhong Cai let a football game be broadcasting by AM waves at frequency of F and the twin brother B go 0.8c speed away from earth. In the leaving path, B will receive 20% of information so that the TV will show very slow motion of the front 20% portion of the broadcast and the remainder 80%, as well as the 100% section of the returning path, will show fast motion on TV so that when B meets A, B has watched the exactly same broadcast as A has watched, but in two kinds of motion-speeds. That is another way to explain Twin Paradox.Jh17710 (talk) 16:17, 4 December 2010 (UTC)
- But we don't know how to match everybody's clock to show same TIME yet. The main difficulty is the starting time of our counting can be at any location of the wave, how far away from the wave peak is a kind of out of control. Once we figure out how to count the wave peaks exactly from a wave peak, then, we can start to figure out the unversal time, not just time period.Jh17710 (talk) 16:17, 4 December 2010 (UTC)
- You are absolutely correct about what SR claims, no universal time. However, that is just a claim, a hypothesis, isn't it? Theoretically, we have some way to calculate the absolute TIME PERIOD by counting the wave peaks from a known frequency souce of light or EM wave emitter at fixed distance. The formula is very simple, total wave peaks, N, times the wave length, L, then divides by the speed of light, c; time period between event C and D is Tcd=NL/c. That means, we can prove that time period is the same for rest and moving observers, theoretically. In his book published 9-1-2010, ZhiZhong Cai let a football game be broadcasting by AM waves at frequency of F and the twin brother B go 0.8c speed away from earth. In the leaving path, B will receive 20% of information so that the TV will show very slow motion of the front 20% portion of the broadcast and the remainder 80%, as well as the 100% section of the returning path, will show fast motion on TV so that when B meets A, B has watched the exactly same broadcast as A has watched, but in two kinds of motion-speeds. That is another way to explain Twin Paradox.Jh17710 (talk) 16:17, 4 December 2010 (UTC)
(undent). No, the point is that, as an entire theory, Special Relativity is both mathematically consistent and experimentally consistent. That's why we can call it a "theory". You are confusing "theory" with "hypothesis", a common mistake. See Scientific theory. Things like the Michelson–Morley experiment confirmed it by proving that there is no "luminiferous ether" and thus there is no medium in which light travels. The fact that the speed of light is invarient regardless of what your own speed is is all that you actually need to prove. The rest of the theory results from the mathematics necessary to maintain an invarient light speed at all frames of reference. --Jayron32 16:57, 4 December 2010 (UTC)
- As for whether you could have universal time with SR; you can try, but it has no meaning. A lot of very smart people (e.g. Poincaré, Lorentz, etc.) attempted to integrate different conceptions of "local time" with "universal time." Einstein was in fact most radical in that he said (in a Machian line of thought) that you can just throw out the propositions which are not required or cannot be measured. We have no reason to suspect there is a "universal time". It is entirely unclear what that would mean physically or even philosophically. All we can measure is local time. Postulating universal time adds an extraneous and unsupported thing to a really quite simple theory that accords extraordinarily well with all experimental evidence so far, and does not get us anything for doing it. There is no philosophical or physical reason that designating one reference frame as "privileged" or "universal" makes any sense. You can do it just for kicks, if you want, but you don't learn anything from doing it. --Mr.98 (talk) 19:21, 4 December 2010 (UTC)
- I like to think of these questions as having to do with the "God's-eye view", i.e. if one could somehow be outside the universe looking in. When Einstein talks about "observers" he's often talking hypothetically, as if extremely fast events could somehow be observed by a normal human. ←Baseball Bugs What's up, Doc? carrots→ 16:52, 4 December 2010 (UTC)
time dilation
at what speed,as a fraction of c,does a moving clock tick at half the rate of an identical clock at rest? —Preceding unsigned comment added by 120.141.101.249 (talk) 12:47, 4 December 2010 (UTC)
- See Time_dilation#Time_dilation_due_to_relative_velocity. --Jayron32 14:40, 4 December 2010 (UTC)
- At about 86.6% of the speed of light, but the "moving clock" runs at normal rate in its own reference frame, of course. It only appears to be moving "slowly" when observed from an inertial frame moving at a different speed. The effect is symmetrical because no one frame can be considered at absolute rest. Dbfirs 15:45, 4 December 2010 (UTC)
- If you look at the section 4 of Einstein's paper published 6-30-1905, he let the moving clock go circling and each time the moving clock meets the rest clock, he calimed that two clocks will read differently. I will say like in front of witness whoever read two clocks at that same time. How do you explain that the difference just {appears to be moving "slowly"} in front of that witness? Do you mean we should not let two clocks meet?Jh17710 (talk) 17:08, 4 December 2010 (UTC)
- Your confusing accelerated motion with non-accelerated motion. Moving in a circle is an acceleration. If two clocks are moving at a constant speed relative to one another, than the observer holding each clock thinks the other clock is moving too slow. In order to get to the two clocks to exist in the same time and place, one or both of the observers will have to accelerate or decelerate to meet the other clock. The exact path each observer takes in terms changing speeds will determine whose clock is ahead of whose. For example, if the two observers came together to observe their clocks in such a way that each performed the exact same set of maneouvers and velocity changes in exact mirror image; then the two clocks would read the same time again. If, however, one observer maintained the same speed, and the other observer changed their speed to "catch up" to the first, then their clocks would be different, specifically the observer who accelerated would have a clock which was ahead of the other person's clock. Moving in a circle is an acceleration, which is why the orbiting clock is ahead of the stationary clock. --Jayron32 17:16, 4 December 2010 (UTC)
- I just said what I understand from Einstein's paper about what Einstein thought at that time. Moving in a circle is an acceleration, but, I think Einstein knew it in year 1905, don't you think so? Or do you mean Einstein was confusing accelerated motion with non-accelerated motion? Not me, for sure. Now, let us use your explanation, but this time we let two clocks run circling at the same speed but different direction on two same size circles on one plane, meet at closest points, like 0.1 meter away from each other. In this situation, which clock will slow down? At the closest point, their relative speed is about 2v, so that the speed of their clocks should not be the same, but the situation is symmetric, which clock should run slower?Jh17710 (talk) 17:38, 4 December 2010 (UTC)
- I think the two will each observe the other's clock to be varying in speed as it goes round the circle, but you need the mathematics of General relativity (a subject that I haven't much knowledge of) for this scenario. Dbfirs 23:43, 4 December 2010 (UTC)
- I just said what I understand from Einstein's paper about what Einstein thought at that time. Moving in a circle is an acceleration, but, I think Einstein knew it in year 1905, don't you think so? Or do you mean Einstein was confusing accelerated motion with non-accelerated motion? Not me, for sure. Now, let us use your explanation, but this time we let two clocks run circling at the same speed but different direction on two same size circles on one plane, meet at closest points, like 0.1 meter away from each other. In this situation, which clock will slow down? At the closest point, their relative speed is about 2v, so that the speed of their clocks should not be the same, but the situation is symmetric, which clock should run slower?Jh17710 (talk) 17:38, 4 December 2010 (UTC)
- Your confusing accelerated motion with non-accelerated motion. Moving in a circle is an acceleration. If two clocks are moving at a constant speed relative to one another, than the observer holding each clock thinks the other clock is moving too slow. In order to get to the two clocks to exist in the same time and place, one or both of the observers will have to accelerate or decelerate to meet the other clock. The exact path each observer takes in terms changing speeds will determine whose clock is ahead of whose. For example, if the two observers came together to observe their clocks in such a way that each performed the exact same set of maneouvers and velocity changes in exact mirror image; then the two clocks would read the same time again. If, however, one observer maintained the same speed, and the other observer changed their speed to "catch up" to the first, then their clocks would be different, specifically the observer who accelerated would have a clock which was ahead of the other person's clock. Moving in a circle is an acceleration, which is why the orbiting clock is ahead of the stationary clock. --Jayron32 17:16, 4 December 2010 (UTC)
- If you look at the section 4 of Einstein's paper published 6-30-1905, he let the moving clock go circling and each time the moving clock meets the rest clock, he calimed that two clocks will read differently. I will say like in front of witness whoever read two clocks at that same time. How do you explain that the difference just {appears to be moving "slowly"} in front of that witness? Do you mean we should not let two clocks meet?Jh17710 (talk) 17:08, 4 December 2010 (UTC)
- To explain in a bit more detail; an observer moving with the clock you call the "moving" clock in your example will believe that the clock you call the "rest" clock is itself moving slower. That is, every observer believes himself to be at rest, and clocks not moving at his speed to be ticking slower. That is because there is no universal rest frame. --Jayron32 15:54, 4 December 2010 (UTC)
- Whether there is universal rest frame or not, that is still a question. We are unable to locate it mainly because of lack of technology for now. One of possible ways is we can try to find a solution to watch the wave front of an expanding ball of light created by a single emission of a point source of light. The hypothesis of the speed, or we should say velocity, of light is independent to the speed, or velocity, of the source of light, provides us the best tool to understand the absolute rest universe that the speed of light, or the velocity of light, is relative to.Jh17710 (talk) 17:22, 4 December 2010 (UTC)
- No, the speed of light is constant with respect to each local observer. There is no absolute rest frame anywhere in the universe. We will never find one, however advanced our technology. We can measure only speeds relative to other objects. There is no fixed point in the universe. I'm not sure that I really understand this, but Einstein seemed to have a good grasp of the idea. Dbfirs 23:34, 4 December 2010 (UTC)
- Whether there is universal rest frame or not, that is still a question. We are unable to locate it mainly because of lack of technology for now. One of possible ways is we can try to find a solution to watch the wave front of an expanding ball of light created by a single emission of a point source of light. The hypothesis of the speed, or we should say velocity, of light is independent to the speed, or velocity, of the source of light, provides us the best tool to understand the absolute rest universe that the speed of light, or the velocity of light, is relative to.Jh17710 (talk) 17:22, 4 December 2010 (UTC)
- Is this a homework question? Looie496 (talk) 17:55, 4 December 2010 (UTC)
- Originally I thought so. But from the history Wikipedia:Reference desk/Archives/Science/2010 November 19#Time Dilation? Time speeding? and the others who understand it better then me I think the answer is no, it's closer to OR (to put it mildly) Nil Einne (talk) 18:17, 4 December 2010 (UTC)
on p block elements
why p block elements consists metals,non-metals —Preceding unsigned comment added by 117.197.60.188 (talk) 15:57, 4 December 2010 (UTC)
- It has to do with effective nuclear charge; whether an element is a metal or a nonmetal is dependant upon how much "pull" the valence electron level "feels" from the nucleus. Larger atoms have more electron shielding, due in large part to the presence of the core "d" and "f" electrons, than smaller atoms. This additional shielding explains why nitrogen and phosphorus are nonmetals, while bismuth is a metal, though they are both in the same group. The electrons in the outer shell of nitrogen experience greater attractive pull from the nucleus; so it has more non-metal character (higher first ionization energy, greater electronegativity) than that of Bismuth, whose valence electrons are "shielded" by all of those extra electrons, making Bismuth more metalic in character. --Jayron32 16:04, 4 December 2010 (UTC)
Time travel question
Hello science volunteers. This is a great service you have here. I hope you can help me.
I have read Earth's Rotation and Earth's Orbit and Time Travel. I understand that theoretically, if a person travelled in time only, they would not end up on the same place on earth at a different time but would end up out in space in a different time - because the earth's movement in its orbit plus the sun's movement around the milky way and the milky way's movement through space would all move the earth away from their starting spot.
So for someone travelling a couple of hundred years through time, I understand they'd end up way out in space.
What I'd like to understnad is what might happen for a person who travelled just one second or even a fraction of a second. To the point where they ended up say at about the height of a tall building. Or buried a short way underground. How can I calculate this?
1. I read in the articles that the speed of the earth's rotation at the equator is 465 m/s. How do I calculate this speed for a different latitude?
2. I'm having trouble visualizing - if a person moved a short fraction in time, would the earth's curvature put them underground or up in the air? Or neither? Is the curvature a factor at all?
3. The article says the earth moves in its orbit at 300,000 m/s. So If a person travelled in time a thousandth of a second, they should end up 300 m away from the starting point. But how do I figure out whether this would be up in the air or underground? I imagine they'd have to start out at either dawn or sunset, but I can't figure out which would give which.
Garsk (talk) 16:12, 4 December 2010 (UTC)
- It's a very tricky question. There are two major problems, and we'll ignore the first for the sake of answering your question. (the first being that time travel simply doesn't work, excepting the sort of time travel we all do, moving forward through time). The second problem, if we assume someone can "travel" backwards through time, the space problem isn't even as simple as you make it out to be. Because of the implications of the relativity theories (special relativity and general relativity) there is no privileged "frame of reference". That is, your question assumes one can remain "stationary" when one jumps through time. The problem is, there is no absolute stationary. That's what "relativity" means; all measurements are relative to each other, and no set of conditions can be defined as "at rest" execpt arbitrarily. That is, we call where we are now "at rest"; however thats for the convenience of the math and not representative of any reality. I suppose, if one wanted to make some assumptions here, you could calculate your trajectory, and based on inertia, calculate where you would have been relative to your old position had you stayed at the same time, and then find out where that was at the new time. The problem is defining your trajectory. The earth spins, it moves around the sun, our galaxy rotates, the local group of galaxies is moving, its a messy issue to work out. Of course, this is all moot since time travel in the Back to the Future sense is impossible. --Jayron32 16:47, 4 December 2010 (UTC)
- You always say that, but Time travel doesn't say that. I don't mean that it would involve DeLoreans and blazing tire tracks, or be feasible for humans or in any way useful, but issuing a decree that time travel is limited to forwards travel at one minute per minute seems premature. 81.131.27.188 (talk) 17:22, 4 December 2010 (UTC)
- There is no known evidence that backwards time travel has ever occurred, nor does it make logical sense that it could occur. The answers to the paradoxes that could result are "explained" by looney theories about the universe magically splitting in two. It makes for interesting fiction, certainly. Like a math teacher of mine once said, "If you start out with incorrect assumptions, you're liable to get interesting results." ←Baseball Bugs What's up, Doc? carrots→ 17:31, 4 December 2010 (UTC)
- Heh. Well, it's all about the Many-worlds interpretation, innit. Some people find it repellent, others find it attractive. (Some of those are awful cranks, but that's not the fault of the idea.) If we're being scientific, we all ought to rein those feelings in. It's not a fringe theory, anyway. 81.131.27.188 (talk) 17:55, 4 December 2010 (UTC)
- Bugs, are you really qualified to pass judgment on quantum mechanics and general relativity? I'm not, and I suspect I have far more knowledge of its details and implications than you do. The truly wise know when to hold their tongue. --Mr.98 (talk) 19:00, 4 December 2010 (UTC)
- If there is any evidence that actual backwards time travel has ever occurred, please place it here on the desk. :) ←Baseball Bugs What's up, Doc? carrots→ 19:35, 4 December 2010 (UTC)
- That's a non sequitur. I'm not sure you realize that, though, which is why you are not exactly qualified to provide an adequate answer to any part of this question. --Mr.98 (talk) 19:46, 4 December 2010 (UTC)
- No it's not. You can invent hypotheses all day long, but unless you can find evidence that support those hypotheses, they remain in the realm of fantasy. ←Baseball Bugs What's up, Doc? carrots→ 19:49, 4 December 2010 (UTC)
- That's a non sequitur. I'm not sure you realize that, though, which is why you are not exactly qualified to provide an adequate answer to any part of this question. --Mr.98 (talk) 19:46, 4 December 2010 (UTC)
- If there is any evidence that actual backwards time travel has ever occurred, please place it here on the desk. :) ←Baseball Bugs What's up, Doc? carrots→ 19:35, 4 December 2010 (UTC)
- There is no known evidence that backwards time travel has ever occurred, nor does it make logical sense that it could occur. The answers to the paradoxes that could result are "explained" by looney theories about the universe magically splitting in two. It makes for interesting fiction, certainly. Like a math teacher of mine once said, "If you start out with incorrect assumptions, you're liable to get interesting results." ←Baseball Bugs What's up, Doc? carrots→ 17:31, 4 December 2010 (UTC)
- You always say that, but Time travel doesn't say that. I don't mean that it would involve DeLoreans and blazing tire tracks, or be feasible for humans or in any way useful, but issuing a decree that time travel is limited to forwards travel at one minute per minute seems premature. 81.131.27.188 (talk) 17:22, 4 December 2010 (UTC)
- EC Sure, no problem. Time Traveler Caught on Film :) A Quest For Knowledge (talk) 19:48, 4 December 2010 (UTC)
- And actually, I'm just going by what Stephen Hawking said some years back, about time being a vector, a one-way arrow. But I'm sure you have far more knowledge of the details and implications than he does. :) ←Baseball Bugs What's up, Doc? carrots→ 19:39, 4 December 2010 (UTC)
- Personally, no, but Hawking is not the only guy in physics, nor universally agreed with by professional physicists, and I know that much. I certainly know when I am out of my depth, which you apparently do not. --Mr.98 (talk) 19:47, 4 December 2010 (UTC)
- Kurt Gödel wasn't exactly a crank: closed timelike curve. See also Novikov self-consistency principle, on avoiding the grandfather paradox. It's no crazier than the rest of general relativity, really. TenOfAllTrades(talk) 19:17, 4 December 2010 (UTC)
- Time travel in the sense of the OP, or as in Back to the Future, involve the time traveler having a discontinuous world line. There is no evidence that suggests that time travel in that sense might be possible. The kinds of time travel discussed in Time travel that are known to actually physically exist (time dilation) or haven't yet been ruled out as conflicting with our current understanding of physics (closed timelike curves) involve continuous world lines. Red Act (talk) 20:33, 4 December 2010 (UTC)
Thank you for the background. I'm sorry I didn't understand all of it, but I get the idea you can't answer my question because you say time travel is impossible anyway. Could you pretend that it is for the sake of the calculations I have asked about? How would I calculate where I was a thousandths of a second ago or where I will be a thousandths of a second in the future, with respect just to the earth's motion around the sun and its own rotation? Is that more answerable? And thanks again to everyone who tried. Garsk (talk) 19:33, 4 December 2010 (UTC)
- Forward time travel is not only possible, we're all doing it right now. For the calculations, though, you first have to define a frame of reference. For example, if you knew where the "center" of the universe is, you could travel in the direction of the line defined by its point and the point where you are, in which case you would be best off to be on the lee side of the earth from it. But you can use that same principle for any frame of reference, for example you could travel along the line connecting the center of the sun with the center of Polaris. Again, make sure you're going "up" rather than "down" at that moment, or you might find yourself in an early grave. ←Baseball Bugs What's up, Doc? carrots→ 19:43, 4 December 2010 (UTC)
- General relativity doesn't give any simple answer. In order to know "where" you end up, you also have to know "how" you traveled in time. Since we don't know of any concrete way to travel in time, there is no way to say anything about where you could end up. Dragons flight (talk) 20:03, 4 December 2010 (UTC)
I guess the problem is I really don't understand why my question can't be answered on an imaginary basis. Probably I don't get it because I don't understand the "real-world" physics of time travel at all. Apologies for that, because I do appreciate you are all trying to help.
However, the Time Travel article says that this idea has been used by science fiction writers. I know fiction isn't the real world but for this question I don't really care; I just want to be able to imagine what was supposedly going on in such stories.
Can it be answered, with respect to the earth's motion around the sun, where the point in space is that a person on a particular spot on the surface of the earth now would reach in one-thousandth of a second, relative to that spot on the earth now? Baseball Bugs is getting close to what I am trying to ask - I want to know if this spot would be up or down and which part of the earth is the lee side or trailing edge and which part the leading edge.
Garsk (talk) 20:52, 4 December 2010 (UTC)
- It cannot be answered because there is no unique way of identifying "here" now with "here" some time later. Take an example of real travel. Say, at 9am you sit down in your seat ("here") in a lecture hall of the University of A. Two hours later, lecture finished, you're still in your seat in the lecture hall of the University of A. On the other hand, imagine you take a train, at 9am you're sitting in your seat (here) in the train at the station of A. Two hours later the train arrives at B. Now, "here" is your seat in the train at the station of B. What "here" at 11am means actually depends on which reference system you choose. If you define "here" with respect to a reference system that is fixed with respect to your seat and the train, then you are "here" both at 9am and at 11am. If you define "here" with respect to a reference system that is fixed with respect to the surface of the earth, then "here" is the station of A at both 9am and 11am. You are not "here" any more, you have travelled "there". There is no such thing as "travelling just in time", this depends on which reference system you choose.
- Having gotten that out of the way, we can just choose one. Say we choose one which is fixed with respect to the centre of the sun and which is not rotating. Then, yes, you can answer the question of where you will be a millisecond from now if you stay fixed with respect to that reference system which we have defined just now. The answer depends on what time of day you choose to stay fixed. At 6am you'll hop 30 metres underground (the earth's orbital velocity is 30,000 m/s, not 300,000), at 6pm you'll hop 30 metres in the air (whether straight up or down or at an angle depends on your latitude and the time of year). Does that satisfy you?
- With respect to fiction, there is of course nothing that can be said. If a writer chooses to allow time travel they are also free to specify the details of how it's supposed to work because just changing that one detail actually throws out all of our theories of physics which do not allow time travel. H.G.Wells lets his time machine follow all the movements of the earth so that it stays fixed with respect to the surface of our fair planet. Others may follow an interpretation like the one that you suggest. --Wrongfilter (talk) 21:26, 4 December 2010 (UTC)
- I just also want to point out that only taking into account relative motion vise a vise the Earth or even the Sun omits the relative motion that you get from the rotation of the Milky Way (which is on the order of 220 km/s or something like that). Just to illustrate part of the problem here. --Mr.98 (talk) 22:27, 4 December 2010 (UTC)
- You should also take into account the motion of Dark flow if you believe that it exists. Science fiction time travel usually just assumes that the device includes some form of stabilisation with respect to local space and objects, though some stories assume a fixed distance from the centre of the earth and so time travellers end up buried etc. In fact no reference frame exists in an absolute sense, so there is no fixed point in the universe from which to measure displacement. See also Metric expansion of space. Dbfirs 23:27, 4 December 2010 (UTC)
- I just also want to point out that only taking into account relative motion vise a vise the Earth or even the Sun omits the relative motion that you get from the rotation of the Milky Way (which is on the order of 220 km/s or something like that). Just to illustrate part of the problem here. --Mr.98 (talk) 22:27, 4 December 2010 (UTC)
Calculations
OP, you just want something like this for eg. your first question ("How do I calculate this speed for a different latitude?"):
from the Angular velocity article... right?
Now say R is the radius of the Earth (use the approximation of 6371km), and r is the radius of rotation (ie. distance perpendicularly to the axis of rotation) at a given latitude (say 39°):
so that, with your value of 465m/s tangential velocity at the equator:
or:
Does that make sense? This is what you are asking for, isn't it? WikiDao ☯ (talk) 22:02, 4 December 2010 (UTC)
Thank you all. Very much. Thats is what I was looking for. Thanks for persevering with me to get there. Plus all the extras.
(WikiDao I had to laugh - knowing nothing about math I thought it would be just numbers. I guess it is just too complicated for a nonmathematician! Thanks for taking the trouble to write and calculate it all out.)
Cheers all. Garsk (talk) 00:24, 5 December 2010 (UTC)
- NP :) Btw: re. 2) the change due to the rotation of the Earth would be "toward the horizon" ie. along the ground (for short times), and re. 3) yes, whether the person goes "up" or "down" or "sideways" in this scenario would depend on the time of day (dawn→down, dusk→up, noon→east, midnight→west if I understand what you are imagining correctly, though there are all kinds of conservation-of-momentum issues and so on, not to mention all the other "time travel" issues mentioned in the comments above...). WikiDao ☯ (talk) 02:04, 5 December 2010 (UTC)
Cars/trucks with fixed axles
Did early cars or trucks have a fixed rear axle, so both wheels had to turn the same speed ? This would obviously cause skittering in turns, where the wheels need to turn at different speeds, so would have been far from ideal. If they did have those, what's the last vehicle to feature such a fixed axle ? StuRat (talk) 19:39, 4 December 2010 (UTC)
- The differential was widespread even before the automobile - it was used in carts, horse-carriages, and chariots since ancient times. Regarding the "last vehicle" to use a fixed-axle, well - these still exist today, in the form of low-cost carts, tuktuks, wheelbarrows, and so on. Nimur (talk) 20:05, 4 December 2010 (UTC)
- Thanks. I understand that trains still use solid axles, so how do they deal with turning ? (Obviously they don't make sharp turns, but it's still got to be an issue even for gradual turns). StuRat (talk) 22:33, 4 December 2010 (UTC)
- A brief explanation is given in our article: Rail adhesion. The part of the wheel in contact with the rail is not quite flat, and this slight tapering of the tread ensures that "when the train encounters a bend, the wheelset displaces laterally slightly, so that the outer wheel speeds up (linearly) and the inner wheel slows down, causing the train to turn the corner". Perhaps a rail expert can give a fuller explanation? Dbfirs 23:14, 4 December 2010 (UTC)
- The trick is that the bit of the left wheel that's touching the rail isn't at the same distance from the axle as the bit of the right wheel that's touching the rail. One of them has to travel further because it's on the outer rail of the curve, but it does travel further because it's also further from the axle. --Anonymous, 04:44 UTC, December 5, 2010.
problems with WWVB NIST time radio broadcast
Are there any problems with WWVB NIST time radio broadcast or atmospheric conditions interrupting the signal?
My father and I both live on the east coast of the US, 14 miles apart. For years both of us have had a clock updated by WWVB. For several days both of them have been way off. Usually putting them in a west window overnight makes them reset, but this has not happened. I changed the batteries and they still have not reset themselves from the WWVB signal. Is there some sort of broadcast problem or interference? Or did both clocks happen to go bad about the same time? Bubba73 You talkin' to me? 20:40, 4 December 2010 (UTC)
- The official WWVB monitoring station reports good signal quality on the east-coast for the last few days, and there has not been a scheduled broadcast outage since October 2010. More official info from NIST: WWVB Radio Controlled Clocks, including estimated reception quality vs. time of day (this changes as the ionosphere's E-region forms and dissipates based on day/night sunlight incidence, affecting the skywave pattern). Nimur (talk) 21:38, 4 December 2010 (UTC)
- Thanks, I didn't know about that information. Both clocks were off by several hours and an odd number of minutes (so it isn't a time zone issue). Bubba73 You talkin' to me? 22:07, 4 December 2010 (UTC)
Step-by-step method for writing the electron configuration of an arbitrary atom
Can someone please give me a step-by-step method of how to write the electron configuration of any atom; one way according that doesn't follow the Aufbau principle and another that does. I know that the specific method I have to use takes into account the position of Lanthanum and Actinium. Also, please keep in mind that I'm in the 11th grade so the notation should not take into account any Aufbau exceptions of consequences of relativistic motion of the electrons. --Melab±1 ☎ 22:34, 4 December 2010 (UTC)
December 5
Do other animals have blood types?
Well, do they? The Masked Booby (talk) 00:29, 5 December 2010 (UTC)
- Yes, they do. You might want to read Blood type (non-human)- Nunh-huh 00:36, 5 December 2010 (UTC)
- That article doesn't mention ABO blood types in other primates - see [17] for a quick overview. Wnt (talk) 03:25, 5 December 2010 (UTC)
Questions about Light: 1. Why 186k miles/sec? 2. What would a "photic boom" look like? 3. (see for yourself)
1. How come light "chooses" to go 186,000 miles/second? Why not 185k or 187k? What causes it to go no slower or faster than that seemingly arbitrary speed?
2. If we ever break the speed of light on a starship, whereas breaking the speed of sound on a plane caused a sonic boom, and we know what that sounds like, what would a photic boom look like?
3. In what language did God say "Let there be light?"
--Let Us Update Wikipedia: Dusty Articles 00:59, 5 December 2010 (UTC)
- 1. In the more sensible units used by most of the world the speed of light is 299,792,458 metres per second, i.e. very close to 300,000,000m/s, a lovely round figure. Maybe God was aiming for the latter figure and got it slightly wrong. Or maybe humans have the metre or the second slightly wrong. HiLo48 (talk) 01:30, 5 December 2010 (UTC)
- 2. For the time being, see Cherenkov radiation. --Wrongfilter (talk) 01:41, 5 December 2010 (UTC)
- 3. ...and who was he actually talking to? --Wrongfilter (talk) 01:42, 5 December 2010 (UTC)
- The speed of light in a vacuum is determined by two physical constants, see Vacuum permeability#Significance in electromagnetism. And aparantly God did it this way so that it takes 500 seconds for light to go from the Sun to the Earth. Bubba73 You talkin' to me? 01:56, 5 December 2010 (UTC)
- 3: I've seen t-shirts printed with:
- And God said...
- ...and there was Light.
- (see Maxwell's equations;) WikiDao ☯ (talk) 02:16, 5 December 2010 (UTC)
- I remember that. But a physics professor told me that you only need two of them for light (I forgot which two). Bubba73 You talkin' to me? 03:07, 5 December 2010 (UTC)
- One of them Should be: . I think it would be the
secondlast two that you need for light. Bubba73 You talkin' to me? 03:10, 5 December 2010 (UTC)
- One of them Should be: . I think it would be the
- Here's the t-shirt design I've seen at the MIT museum (turns out it was designed in 1977 by an MIT Rabbi, no less!:). So, right, it looks like he's actually using the "Formulation in terms of free charge and current". WikiDao ☯ (talk) 03:29, 5 December 2010 (UTC)
- Our article says:
But I will leave it for someone else to explain whether you need all four equations for there "to be light", or only the last two, and why... WikiDao ☯ (talk) 03:43, 5 December 2010 (UTC)"Maxwell's equations are a set of four partial differential equations that, together with the Lorentz force law, form the foundation of classical electrodynamics, classical optics, and electric circuits. These in turn underlie the present radio-, television-, phone-, and information-technologies."
For 3, the Book of Genesis was written in Biblical Hebrew. Whether God actually spoke that language in the beginning is a question for religious philosophers. Buddy431 (talk) 03:56, 5 December 2010 (UTC)
How DID I lose 3 pounds while I sleep?
I weighed 187 before bed, and 184 just some minutes ago. I don't understand. How would I lose weight while I sleep? Does carbon dioxide weigh heavier than oxygen as I breathe out? I didn't know I sweat out a lot at night. If I shed 3 lbs of skin, don't you think I would've noticed that on my bedsheets?
How did this happen then? --70.179.178.5 (talk) 01:09, 5 December 2010 (UTC)
- Most likely the scales aren't too precise, and have a margin of error of a few lbs either way. Or perhaps someone recalibrated them overnight, or they're not quite on a flat surface and so the weight wasn't distributed evenly. Are they digital or analogue? As for carbon dioxide, that's pretty irrelevant as, since it's the same density as air, it wouldn't register on the scales anyway. -mattbuck (Talk) 01:20, 5 December 2010 (UTC)
- Are they digital or analogue? Digital. --70.179.178.5 (talk) 03:12, 5 December 2010 (UTC)
- It's not at all unusual to lose 2-3 pounds during sleep through obligate water loss (about 700 cc of water lost in expiration, and the rest through transpiration (un-obvious sweating) through the skin. And more if you pee before weighing. - Nunh-huh 01:24, 5 December 2010 (UTC)
- The oxygen you breathe in oxidizes sugars and fats in your body, turning them to carbon dioxide, which you breathe out. CO2 is heavier than O2. --T H F S W (T · C · E) 02:32, 5 December 2010 (UTC)
Boiling water
When one boils water there's a range of temperatures at which the water remains boiling and boils more violently when you turn up the heat. I've been having a dispute with my wife. My understanding is that the water temperature doesn't change but remains constant and the water roiling more is how the heat that can't go above the boiling point of the altitude you are cooking at, is dissipated. Anywyay, back to the fight. When she's cooking and is boiling something, she always keeps it the flame at full blast, and I always say she's wasting gas and running up our bill and the eggs/potatoes/whatever is not cooking any faster. She says I'm an idiot. Come what may, I am going to show my wife the responses to this post, so I hope someone can provide a scientific answer that settles this once and for all.--162.83.167.217 (talk) 02:43, 5 December 2010 (UTC)
- You're right, but my advice is to keep it a secret. HiLo48 (talk) 03:18, 5 December 2010 (UTC)
- A bigger flame will certainly heat water up to the boiling point faster, potentially saving gas. You're right that once the water's at a full boil, the temperature is constant no matter what the flame size (provided, of course, that the flame is big enough to maintain a full boil). But you boil eggs for what, a couple minutes? That amount of gas is going to be minuscule compared to what you're burning in your freezer all winter long (assuming you have a gas furnace). Buddy431 (talk) 03:50, 5 December 2010 (UTC)
- You're both wrong, and you should stop fighting about it. Your wife is wrong in thinking that a higher flame will cook an egg faster, and you're wrong in thinking that her habit of using a high flame when a low one will do is going to make any appreciable difference to your pocketbook. - Nunh-huh 03:22, 5 December 2010 (UTC) To misquote the sixties: Make love, not potato salad. - Nunh-huh 03:41, 5 December 2010 (UTC)
- You are partially correct, in that once the temperature of water reaches its boiling point, any additional applied heat turns water into steam faster, without raising the temperature of the water significantly. However, in the end your wife is more correct. Water that's boiling like crazy will consist of a larger fractional volume of steam bubbles than water that's boiling gently, and steam at 100° C and 1 Atm can transfer more heat to the food than liquid water at 100° C, because the steam can release its latent heat of vaporization. See the "Steam vs. Hot-Water Burns" section of this test answer page. The page pertains to causing burns on skin, but presumably cooking human skin is rather similar thermodynamically to cooking food. Red Act (talk) 04:21, 5 December 2010 (UTC)
traction between the wheel and the tire
This one has always puzzled me. A concern in automotive engineering is often the loss of traction between the road and the contact patches of the tires on the driven wheels. What I have never heard of is concern over loss of traction between the metal wheel and the tire itself (never heard of a wheel spinning while the tire stays still). The coefficient of friction between rubber and road is much higher than rubber and the metal of a wheel and the area of the contact patch seems to be at least as large if not larger than the area of contact between the wheel and tire. The pressure on a contact patch includes about 1/4 of the vehicle weight while the air pressure forcing the tire to the wheel is about 30psi. (I suppose minus the external pressure forcing the tire away from the wheel.) So what am I missing here? (I do know that some specialized off road vehicles use bolt on bead locks to hold tires onto wheels, but this might be for different reasons, although they do probably run lower tire pressure.) --Leivick (talk) 03:09, 5 December 2010 (UTC)
- As an off-roader, I can tell you for certain that we run lower tire pressures. The lower tire pressure puts a larger patch on the ground. It also makes the ride a bit smoother but that's just icing on the cake. The bead lock is to keep the tire on the wheel, it's not to keep the tire from spinning on the wheel. Dismas|(talk) 03:18, 5 December 2010 (UTC)
Dream time vs. real time
How does perceived time in dreams correspond to real time? Often, I wake up 1 hour before class, go back to sleep, and wake up thinking that I've been dreaming for hours, when in fact only half an hour passed. One time, I heard a knock on my door in my dream that corresponded to an actual knock on my door in real life. I thought I woke up 4 minutes later, but the person who knocked said I woke up only 30 seconds later. So in my dreams, time seems to be significantly slowed. --140.180.3.134 (talk) 03:45, 5 December 2010 (UTC)
Hi. When Zn(OH)2 is dissolved in an excess quantity of NaOH, what product(s) are formed? Zinc hydroxide has a high solubility/un-decomposes in strongly base (and acid) solutions, so that two different metal cations form around one oxide anion element. Does Na4ZnO3 exist, or is Na2ZnO2 always the only zincate compound synthesized? Thanks. ~AH1(TCU) 03:47, 5 December 2010 (UTC)