The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
A question that is about 15 years overdue: What'll it take for beanies to actually fly the wearer?
In my childhood, I remembered reading a lot of Calvin & Hobbes humor comics. Calvin waited 6 weeks for a Beanie to arrive in his mail, after ordering it through a magazine catalog (IIRC.)
While he waited, he dreamed of flying all through the sky with the beanie, while holding it by the handles.
Then one day, it arrived. He put it together and got it to run. However, the motor wasn't giving it enough of a spin to lift him off the ground. Calvin got enraged, smashed it up, and vented to his tiger pal Hobbes about it.
I had wondered what it would take to make a beanie that actually flies the wearer, but back in the mid '90s, there was no Wikipedia (and its Reference Desk), no Answerbag, no AOL Answers, nor any other Q&A sites I was aware of back in the days of crawling through the "Information Superhighway" on 14.4k modems.
(On what online venue could I have asked this question back in '95-'96 anyway?)
For one, bigger blades; I am not sure the standard propeller blades on a beanie could generate enough Lift to actually pick you up off the ground. You'd also need a motor to drive the blades. Furthermore, helocopter blades will tend to twist you out of alignment; so you'd need a counteracting set of blades; either a second set which rotated in the opposite direction, like the this one or a second blade at right angles to the main ones, like the this one. --Jayron3202:25, 31 December 2010 (UTC)[reply]
But a smaller one. My guess based on some googling is that you need approximately 8 foot blades to lift a human. There are some website that give formulas to calculate the lift of a helicopter. You can't increase the lift forever - once you hit the speed of sound you can't do any better. At lower altitudes you can use smaller blades because the air is thicker, so you need to take into account how high you plan to go. Ariel. (talk) 09:18, 31 December 2010 (UTC)[reply]
I never knew that was actually possible in the laws of physics. Of course, it's got support and a seat for the rider. Looking at the actual C&H strips, you can see it's just a hat with a propeller.
My local news just showed a video of a suspected DUI traffic stop in which the driver failed in his attempt to walk a straight line — however, after stumbling and giving up, he proceeded to turn a cartwheel. How is it that alcohol can prevent someone from walking straight but not from maintaining the balance and agility necessary to avoid falling over like I do when I try to turn a cartwheel while sober? Nyttend (talk) 04:09, 31 December 2010 (UTC)[reply]
The issue is that DUI tests are standardized; they need to be to be admissable as evidence in a court of law. Officers perform the same set of standardized tests, and videotape the evidence. Turning cartwheels isn't a part of the standardized set of DUI tests in any state I know of. So the fact that one could do so doesn't make any difference in establishing reasonable suspicion to arrest someone for DUI. If litigated in court, I suppose that the defendent could perhaps use such cartwheel as evidence that he was sober enough to drive; but that wouldn't mean that the officer at the scene would be wrong for arresting the person for DUI if they failed the standardized tests. They may argue to get their license back based on that evidence, but that has no bearing on how the arresting officer should act at the scene. The officer should always do it "by the book": administer the standard tests, and if the standard tests are failed, place them under arrest. Let the courts deal with anything that comes later. --Jayron3204:24, 31 December 2010 (UTC)[reply]
I wasn't trying to question the claim that he was drunk; the rest of his behavior made it obvious that he was very much under the influence. My question asked how he could perform a cartwheel despite being unable to do much simpler things. Nyttend (talk) 05:04, 31 December 2010 (UTC)[reply]
Balance depends heavily on feedback-driven control, which is particularly impaired by alcohol. A cartwheel is a complex motor sequence, but it doesn't depend very heavily on feedback. Looie496 (talk) 04:59, 31 December 2010 (UTC)[reply]
Can you explain what you mean by "feedback"? I've read the "Biology" section of our feedback article; its final paragraph somewhat resembles what I think you mean, but it seems somewhat irrelevant, so I suspect that you mean something different. Nyttend (talk) 05:08, 31 December 2010 (UTC)[reply]
In order to balance, your body needs to get information about where it is now and use that information to maintain that position. So your brain analyzes a whole shitload of information; some from your inner ear, some from the tension on your muscles, some from your vision, to determine where you are in relation to, say, the ground, and then based on that information, it makes minute adjustments to your muscles to keep you standing straight and balanced. Alcohol short-circuits that feedback, so while you may be fully in control of your muscles while drunk, your brain is receiving bad information about your "location" in the world, so it cannot easily autocorrect if you are falling. That's why drunks fall over; not because they don't have muscular control, but rather because their automatic balancing system is receiving fuzzy information. --Jayron3205:15, 31 December 2010 (UTC)[reply]
... and safe driving relies on this "feedback", so the walk test is better than the cartwheel test. Even drunk drivers can make a car cartwheel! Dbfirs10:16, 31 December 2010 (UTC)[reply]
... and turning a cartwheel cannot be performed by anyone able to drive, so it has no value as a test, since a DUI test should be positive for all (or most) drunk drivers and negative for all (or most) non-drunk drivers. However, why put people to walk? In Europe, as far as a I know, they always use a breathalyzer. If you want, you can request an additional, more precise blood testing. Quest09 (talk) 20:51, 31 December 2010 (UTC)[reply]
Not to say any of the above comments are wrong, but to answer the question a bit more directly, the "biology" part of the feedback article doesn't really cover its role in motor control -- the "control theory" section is more relevant. Basically feedback control of a movement means noting errors in the execution and adjusting the movement to reduce them; feedforward control means generating the correct muscle activity before any useful feedback comes in. In a cartwheel, by the time you have noticed that you screwed up, it is too late to do anything about it. (The feedback is however useful for learning -- if you get something wrong, you can try to change it on the next attempt.) Looie496 (talk) 23:47, 31 December 2010 (UTC)[reply]
How can the universe be infinite?
The article Universe says that "The universe is very large and possibly infinite in volume.". However, this seems at odds with logical thinking.
The universe is expanding at a very high speed, but not at an infinite speed. Let's call this speed x
The universe has been expanding for a very long period of time, but not an infinite period of time. Let's call this time t.
Therefore, the current size of the universe should be a direct function of t and x. If neither x nor t are infinite, how can the size of the universe be infinite at any given moment? Thanks. Leptictidium (mt) 07:43, 31 December 2010 (UTC)[reply]
I'm not a cosmologist, but my general understanding is that if the universe is infinite in extent now, then it always has been. It's often claimed that the big bang means that the universe sprang from a single point, but that is not in fact a necessary part of the theory. If you run the equations backwards you get to a moment when the universe was infinitely dense, but it did not necessarily have zero volume. --Trovatore (talk) 07:55, 31 December 2010 (UTC)[reply]
If the infant universe had infinite volume and infinite density, then it must have had infinite mass (since density is a function of mass and volume). However, our present universe does not have infinite density, so where did all the mass go? Leptictidium (mt) 08:17, 31 December 2010 (UTC)[reply]
If it has infinite volume now, and density finite but bounded away from zero (that is, there is some nonzero density such that every part of the universe is at least that dense), then it also has infinite mass now. So why did it have to go anywhere?
For one thing, the big bang wasn't necessarily the whole universe, it could have just been a portion, and there may have been many other big bangs, far away. We wouldn't know about these other big bangs unless one of them expands into ours. StuRat (talk) 08:45, 31 December 2010 (UTC)[reply]
I recently completed a second year cosmology paper, and what I was told is that the universe is not infinite, neither does it have an edge. The best definition of the edge of the universe you can get is halfway between the centre of the universe and itself. In other words, if you had a ridiculously long pole, growing longer at the same rate as which the universe is expanding, you should be able to tap yourself on the shoulder. --Plasmic Physics (talk) 09:10, 31 December 2010 (UTC)[reply]
Well, you can write down models where space is finite in total area without "ending" anywhere. The surface of the Earth is also like that. There's no central point on the surface of the Earth, and any point on the surface could be described as "halfway between the antipodal point and itself", though it's probably better not to describe it that way. There's no evidence favoring those models over other models, but they are at least consistent with the available evidence. -- BenRG (talk) 10:32, 31 December 2010 (UTC)[reply]
What cosmologists mean by the "total size of the universe" and the "expansion of the universe" doesn't exactly match the everyday meaning of the words, in part because in general relativity the distinction between space and time is a bit fuzzy. Shown to the right is the Milne universe, which is basically a simplified (numerically inaccurate) version of standard cosmology that's easier to visualize in a 2D diagram. This model is spatially infinite at all times, in the sense meant by cosmologists. See the previous Ref Desk threads Light from just after the Big Bang and Infinite amount of mass in the universe? where I mention the Milne model, and Speed in space which has a more accurate picture. And also see Ned Wright's cosmology tutorial. -- BenRG (talk) 10:32, 31 December 2010 (UTC)[reply]
@Leptictidium: You asked why we have finite density now if we had infinite density in the past. It is important to realise that this question is actually the wrong way round (no blame - I make that kind of mistake too often myself). We do not know that the density was infinite in the past; what we do know is that now it is finite. The "correct" question would then be why we had infinite density in the past when we have finite density now, and we can answer that one. We also know that the universe is expanding (i.e. mean density is decreasing) and we have a theory for that expansion. Using that theory and our knowledge about the present state of the universe as initial condition, we can determine how the mean density of the universe evolved in the past. Doing that we find that the density increased (going backwards in time) without bound. The point where the density formally diverges (becomes infinite) is called the "Big Bang". The Big Bang is just that: an extrapolation backwards in time. However, we also know that our theory breaks down at some point when the mean density becomes larger than what we can handle with our knowledge of quantum theory and general relativity. Hence, the big bang is a simple extrapolation beyond our secure knowledge of physics. Unfortunately, the big bang is, especially in popular science books and documentaries, often represented as a secure fact and it is way overstressed. The initial question, whether the universe is finite or infinite, is not answered yet. We do have some constraints on the minimum possible size (if it is finite), nothing more. There is a nice book about this topic (the topology of the universe) by Jean-Pierre Luminet, which is available in English, I think. --Wrongfilter (talk) 11:45, 31 December 2010 (UTC)[reply]
The way I see it, if the universe were expanding at the speed of light in all directions, and we are correct that it is impossible to exceed the speed of light, then for all intents and purposes, the universe would be infinite since you can never get to any edge. Googlemeister (talk) 15:07, 31 December 2010 (UTC)[reply]
The universe is not expanding at the speed of light. The rate of increase of distances (which is not a velocity!) is proportional to the distance (suitably defined) and is not limited by the speed of light. --Wrongfilter (talk) 15:35, 31 December 2010 (UTC)[reply]
The connection with the visible universe is not correct. The rate of increase of the distance between two objects (they are not "travelling" - where would they travel to?) is equal to 300000 km/s (the speed of light) when they are at a distance of 4.28 Gpc (for H0=70 km/s/Mpc), that corresponds to a redshift of 1.45 (per Ned Wright's cosmology calculator), nowhere near the horizon. The speed of light has nothing to do with the metric expansion of space. --Wrongfilter (talk) 18:03, 1 January 2011 (UTC)[reply]
Expanding on Wrongfilter's reply: in the Milne universe, shown above, there's no upper limit to the cosmological recession speeds, even though the special relativistic speeds of the very same objects are all less than c. The cosmological recession speed in this case is equivalent to rapidity (times c, since rapidity is usually given as a unitless number). A rapidity of 1 (or c) has no special significance. It's like an angle of 1 radian. -- BenRG (talk) 01:31, 2 January 2011 (UTC)[reply]
If I evaporated a solution of antimony trichloride in a solution of concentrated hydrochloric acid, would the antimony trichloride precipitate as a solid? --Chemicalinterest (talk) 12:47, 31 December 2010 (UTC)[reply]
Most of the chlorides if produced by this way would give the oxide and hydrochloric acid. I have to have a look for the example of antimony trichloride, but I doubt that the compound is stable in water at all.--Stone (talk) 13:34, 31 December 2010 (UTC)[reply]
The group 15 elements form a huge range of oxohalides as well. SbOCl is the simplest example in this system, but there are many others. Also, SbCl3 is described as deliquescent, so you are not going to be able to form a solid by evaporation at ambient temperature and pressure. Raising the temperature or lowering the pressure will drive off HCl before it drives off water, and so promote hydrolysis of the chloride to the oxochloride. In short, no. Physchim62(talk)16:05, 31 December 2010 (UTC)[reply]
Sorry! I have to correct myself. Butter of Antimony [1] is the very old name of the compound. Best produced by dissolving antimonsulfid in conc. hydrochloric acid. When always an excess of hydrochloric acid is present the liquid can be evaporated. You get a white substance of waxy consistence ( therefore called Butter of Antimony). If the solution of Antimony trichloride in water is diluted in water a complicated mixture of oxides is formed which at the end will be antimony oxide.--Stone (talk) 17:16, 31 December 2010 (UTC)[reply]
Best length of radio aerial
I have a small mains-powered transistor radio, which had an aerial wire sticking out of the end. The aerial wire has now broken off and I will need to re-attach it, or bin it. The wire was 970mm long. I mostly use it to listen to a radio channel on about 94Mhz, FM. Where I am, reception is not very good. What would be the best length for the new wire aerial? If 970mm was the best length, would there be any advantage in having the wire a multiple of this length, such as twice, thrice, four times, etc? A particular problem I have is that another more intense signal is right next on the dial to what I want to listen to. I still get some reception without the wire attached, but it is not as good. Please do not suggest buying a DAB radio as the signal is not good enough here, regretably. Thanks 92.24.176.169 (talk) 19:45, 31 December 2010 (UTC)[reply]
Under ideal conditions the best length, a quarter wavelength with some adjustment for end effects, would be about 760 mm. It sounds like your biggest problem is the stronger station, and a longer wire would just make the strong station stronger. If the weak station and the strong station are in different directions, try putting some kind of metal screen in the direction of the strong station. Jc3s5h (talk) 20:00, 31 December 2010 (UTC)[reply]
Odd multiples will match the impedance of the input stage better, an even multiple will have a high impedance. However boosting the input will overload the radio more and increaase the problem due to the interfering station. If you have the space a dipole antenna connected via a balun to the antenna input will get you more control. Match the polarization and rotate to minimise the interfering station. Graeme Bartlett (talk) 22:08, 31 December 2010 (UTC)[reply]
The aerial has only one connection, I would not know where to connect the other half of a dipole. From what I remember of other radios, dipole antennas for VHF are not very big. If the interfereing channel is ignored, would for example a 3/4 wavelength monopole be better than a 1/4 wavelengtn monopole? 92.24.185.151 (talk) 23:23, 31 December 2010 (UTC)[reply]
Please explain why a 1/4 wavelength aeriel will be better than an aerial three times as long as this, I'm sceptical. The longer aeriel will collect three times the signal energy. (And three times the signal energy is nothing compared to the higher signal intensity of someone living nearer the transmitter, so the radio should be easily able to cope with it). The Wikipedia antenna article also says: "The random wire antenna is simply a very long (at least one quarter wavelength) wire with one end connected to the radio and the other in free space, arranged in any way most convenient for the space available. Folding will reduce effectiveness and make theoretical analysis extremely difficult. (The added length helps more than the folding typically hurts.)". That says nothing about a quarter walevlength being best, and the links I've read also say nothing about a quarter wavelength being best, although warning against using a half-wavelength or multiples of that. 92.15.14.57 (talk) 14:46, 1 January 2011 (UTC)[reply]
The thing about a random wire antenna is for cases where a 1/4 wavelength is impossible to string - it's just too long. So instead a wire is placed randomly. If you actually can run the wire to the correct length then do that. Ariel. (talk) 23:50, 1 January 2011 (UTC)[reply]
I'm getting a little weary of your sarcasm and argumetativeness. Volunteers have answered your questions with detailed and accurate answers. Please show some politeness to them, even if you don't like the answers. If you would rather follow your own advice, that is ok with us too. SpinningSpark14:21, 2 January 2011 (UTC)[reply]
I'm also wondering where the impoliteness is? Would you like to give excerpts of the text that you consider sarcastic, argumentative, or impolite? 92.15.31.128 (talk) 12:17, 3 January 2011 (UTC)[reply]
Where's the sarcasm? Where's the argumentativeness? Perhaps you mistake my asking why a 1/4 wavelength aerial would be better than the larger 3/4 wavelength, to which I've had zero answers. Maybe you also mistake my pleasant surprise at discovering fractal aerials, as they may offer a compact solution that's better than a length of wire because it gets a more intense signal, can cover a wide range of wavelenths, and does not need any extra aerial circuitry. If Maplins sold one like the ones they have in mobile phones, I'd buy one and try it out. 92.28.255.126 (talk) 19:49, 2 January 2011 (UTC)[reply]
A ideal 1/4 wave antenna need to be straight, in line with the polarisation of the wave, have a infinite conducting plane perpendicular to its base, a purely resistive load of 36.5 ohm and no other conducting or dielectric material in its vicinity.
Since this is not likely to be the case 1/4, 1/2, 3/4 wavelength and so on are irrelevant. 1/4 of a wavelength can give you an idea of a suitable length, much shorter will not be as efficient and the inductance of a much longer antenna will normally prevent it from being much better. Other than that it is trial and error to find a good length and placement. It can of curse be calculated but the complexity of a typical home environment, will require an advanced computer model.--Gr8xoz (talk) 11:40, 3 January 2011 (UTC)[reply]
I did not say that it is worse, I did say it is not much better. You could think of it as a elastic rubber band floating on the water surface, wave energy picked up at the far end will mostly be re-emitted in to the water before it reaches you. The inductance is similar to the elasticity of the rubber. This is not an exact analogy but it shows the principle. A longer antenna has a more complex sensitivity pattern and can be more directional but since it is hard to predict the direction of sensitivity that is not an advantage. --Gr8xoz (talk) 12:55, 3 January 2011 (UTC)[reply]
In any superheterodyne receiver you have a trade off between sensitivity and selectivity. The laws of physics prevents you from having the best of both. Asking why a 1/4 wavelength antenna would be better than the larger 3/4 wavelength antenna when the receiver gets influenced differently by each of them is like asking which is better Bush or Obama? Both have their own properties and a specific scenario in which each of them will be the best choice. There is no one-size fits all solution to your question. For your small mains-powered consumer transistor radio a 1/4 wavelength antenna would be the best choice to maintain the designed quality factor of the receiving LC circuit and to keep the sensitivity and selectivity within the range that the designer intended. That is why the designer/manufacturer of the radio used a 1/4 wavelength antenna with some extra length to compensate for the lack of a ground plane and the parasitic capacitance introduced by the operator. --Sage.electcon (talk) 07:17, 5 January 2011 (UTC)[reply]
January 1
When beer is left in an open container for a long time
Carbonation is bad for your teeth, in that it forms carbonic acid, which can etch the surface and allow cavities to form. So, in a sense, flat beer is healthier. StuRat (talk) 06:22, 1 January 2011 (UTC)[reply]
(ec) I don't think it loses much alcohol in moderate time, because there isn't that much to start with. (Whiskey, on the other hand, becomes substantially weaker in a few hours, I think.)
(ec)Not sure what you mean by "better for you". You may be better off with a Soft_drink if you don't like beer, especially if you're driving. What happens to beer depends how long it's left. After a few hours the carbonation will go, as Beeblebrox says. The beer will also warm up to room temperature. Some beers taste better very cold, and are traditionally drunk in this state (US and Australian beers in particular) while others, such as UK "bitter" are more often drunk at room temperature. So some beer will taste nasty, other beer won't. After a few days in an open vessel the sugars in beer will start to grow mould and the sugars will turn to vinegar. How long do you mean by a "long time"? TonywaltonTalk00:40, 1 January 2011 (UTC)[reply]
Agree that before much alcohol has evaporated the quality will be affected. By the way, English bitter should be drunk at cellar temperature, i.e. about 9degC. It isn't heavily carbonated like canned beer. Itsmejudith (talk) 17:07, 1 January 2011 (UTC)[reply]
Maybe Tin(IV) sulfate then? I can't see anything happening to the sulfate itself, and copper compounds are all usually brightly colored. --Jayron3215:30, 1 January 2011 (UTC)[reply]
Which may actually be pretty acidic; copper(ii) is a pretty decent lewis acid, and in solution readily forms copper hydroxide complexes, leaving hydronium behind. --Jayron3218:27, 1 January 2011 (UTC)[reply]
I have just completed some tests on a mixture of the almost colorless solution and the white precipitate. Excess HCl dissolves it to form a light yellow-green solution; dilute hydrogen peroxide has no effect on it; and dilute ammonia solution makes the precipitate somewhat more yellow and precipitates more from the solution part. Hope this helps in some way. --Chemicalinterest (talk) 23:04, 1 January 2011 (UTC)[reply]
The addition of the HCl likely formed Copper(II) chloride; excess cloride ion forms a yellowish-green solution. That would likely indicate that your precipitate was some sort of copper-containing species. --Jayron3220:54, 2 January 2011 (UTC)[reply]
Complex/Quadrature Sampling
While reading some web pages on Software Defined Radio, I saw a method to get a high sampling rate by using two ADCs of lesser speed. Contrary to intuition, the two ADCs were operated not 180° out of phase but in quadrature. What is the actual name of this technique, and is there a wikipedia page on it? I'm currently reading an external link from the SDR article, but it seems to talk about QAM modulation techniques rather than sampling techniques. —Preceding unsigned comment added by 59.93.16.208 (talk) 06:12, 1 January 2011 (UTC)[reply]
Depending on the exact arrangement, it might be a phase detector combined with an interpolation algorithm; it might be simply a quadrature sampler; it might be an interferometer (if the Q/I components are compared to a reference signal). There are a wide class of methods that use 90-degree (quadrature) modulation to analyze signals; the exact circuit might help us narrow down the method. Our quadrature article links to some of the numerous uses and applications of 90-degree phase shift for signal analysis; because of the unique properties of fourier analysis, phasing a signal by 90-degrees (in other words, "multiplication of the signal by i) allows additional information to be inserted or extracted from a waveform, because the quadrature signal is orthogonal to the original signal. So many related techniques rely on this quadrature orthogonality property, it's difficult to name a specific one without looking at the exact circuit. Nimur (talk) 08:17, 1 January 2011 (UTC)[reply]
I was reading the GNU Radio site. This is what they have written about the hardware. They have also given an image in which the input from two ADCs are multiplied with Sin and Cos.
The USRP has 4 high-speed analog to digital converters (ADCs), each at 12 bits per sample, 64MSamples/sec. So in principle, we have 4 input and 4 output channels if we use real sampling. However, we can have more flexibility (and bandwidth) if we use complex (IQ) sampling. Then we have to pair them up, so we get 2 complex inputs and 2 complex outputs.
The range of signal frequencies that can be sampled without alias error is said to be limited at half the sampling frequency, called the Nyquist frequency. Alias error here refers to false readings of signal frequencies above the limit. The sketches below demonstrate that phase errors still occur at the Nyquist limit. In the upper sketch the solid samples are at the Nyquist rate and appear to allow an unambiguous reconstruction of the sinewave signal. However with an unfortunate sampling phase relative to the signal, we get the open samples which are all zero. Simply shifting the signal phase by 90 degrees has made it "invisible" to the sampler. In contrast, the lower sketch shows the 0-90-360 degree sampling described by the OP. Here there is no phase ambiguity. Both I and Q (quadrature) components of the signal can be reconstructed. What has been obtained is not an increase in bandwidth but a removal of (amplitudeXphase) ambiguity.
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I have read somewhere that if a fragment of a red giant remains during the explosion, the star collaspes into a black hole. Is this true? Also what causes the super giant to become a black hole and not a Neutron star? What's the deciding factor between these? --Tyw7 (☎ Contact me! • Contributions) Changing the world one edit at a time!08:10, 1 January 2011 (UTC)[reply]
Also, I think you are confused between red giants, which do not explode and is something that happens to smaller/mid-range stars and supernovae, which do explode and is something that happens to larger stars. There is always a remnant after such explosions. SpinningSpark10:20, 1 January 2011 (UTC)[reply]
"Deep snowdrifts have trapped thousands of people in their homes on the Danish island of Bornholm [...] There is so much snow that islanders have started dumping it in the sea - a practice normally forbidden for environmental reasons."
Does anyone have any ideas what these "environmental reasons" could be? Do you think it's just in case the snow is contaminated by oil or something, say from the roads? 86.185.77.168 (talk) 23:00, 1 January 2011 (UTC)[reply]
It's not unusual for transition metal oxides to be a different colour from other compounds. The long-range ionic structure can give rise to new sets of energy levels, and so different electronic transitions (which are the basis of colour). So copper(II) oxide is not blue, for example. Physchim62(talk)01:55, 2 January 2011 (UTC)[reply]
I produced it by reacting manganese(II) sulfate with ammonia and it came out as a very light brown solid that darkened to a yellow-brown solid upon standing. --98.221.179.18 (talk) 02:09, 2 January 2011 (UTC)[reply]
Our I-joist article is silent on your question, although it states that as of 2005, approximately 50% of all wood light framed floors were framed using I-joists. So I'm guessing they are complaint with building codes. In some countries. Which country are you concerned with (as if I could not guess). Our article also says "The biggest notable difference compared to dimensional lumber is that the I-joist is designed to carry heavy loads over long distances while using less lumber than a dimensional solid wood joist of a size necessary to do the same task". That seems to suggest they are stronger, not weaker, than solid wood. You might want to point us at any source which supports your prejudices. --Tagishsimon(talk)01:46, 2 January 2011 (UTC)[reply]
the article lies and should be changed. by definition any engineered wood is weaker than solid. i joists are basically osb which is not very strong at all. in fact i would like to know where i can report these false advertising claims as they are being told by the manufacturers. im in the usa — Preceding unsigned comment added by Tommy35750 (talk • contribs) 02:02, 2 January 2011 (UTC)[reply]
If you could provide a reference or two to confirm your assertion, that would help. Certainly, I cannot agree with the statement "by definition any engineered wood is weaker than solid". By whose definition? And wither plywood, for instance? --Tagishsimon(talk)02:06, 2 January 2011 (UTC)[reply]
Actually I believe that for equivalent weight/size engineered wood is stronger, not weaker. But usually what they do is reduce the weight and size, and keep the strength the same. Ariel. (talk) 02:11, 2 January 2011 (UTC)[reply]
Using products in ways not specified for the product is not a good test of the product. From the Oriented strand board article, we learn that "it does have a specific axis of strength". Which implies that it is weak in other axes. So punching through board, when it is designed to be used in compression or tension about a certain axis, is a test of nothing at all. Your 2 inch solid wood is, undoubtedly, stronger in some ways than 2 inch OSB. But if that strength is never to be put to use in its application, then it is wasted. OSB's advantage is that it uses the cheapest wood inputs to provide strength where it is required, and not to provide strength where it is not required. As such, it is less expensive and weights less. And it has other advantages over your solid wood, noted in the I-joist article. --Tagishsimon(talk)02:27, 2 January 2011 (UTC)[reply]
Weight for weight, an I-joist will be more efficient at load bearing than a solid joist, for the same reasons as an I-beam is more efficient than a solid steel beam. However, it will have a lower safety factor than a solid joist, so any rules of thumb that are used with solid joists will not necessarily apply to an I-joist. In particular, its tolerance to having holes or channels cut through it will be less than for a solid joist. Quality control during manufacturing and installation is also important. To determine whether I-joists meet your local building codes, you would need to consult a structural engineer who is familiar with those codes - that is not something on which Wikipedia editors can advise you. Gandalf61 (talk) 08:52, 2 January 2011 (UTC)[reply]
Some I-beams, sold in Europe, have a light metal web, rather than engineered wood. The manufacturers' and major vendors' websites usually carry data about strength. If building in the UK you would need calculations by a structural engineer, and they would take the manufacturer's data and feed it into a computer algorithm. If I-beams were unsuitable for building they would not be licensed in so many countries. Itsmejudith (talk) 11:38, 2 January 2011 (UTC)[reply]
there are a lot of new houses going up near where i live and almost all of them are being built with I-joists. they've got a basement and two floors on top of said i-joists. i've been into plenty of these houses when fully built and they all seem at least as structurally stable as my 50yo house build with 2x12 joists. purely anecdotal evidence, but if they're building with them they must comply with code ZigSaw02:46, 4 January 2011 (UTC)[reply]
Yes, although the source will have to vary for example, a GASER (Gamma Amplification by Stimulated Emission of Radiation) is of nuclear origin. A SASER is the sound analogue of a LASER. --Plasmic Physics (talk) 11:55, 2 January 2011 (UTC)[reply]
The existence of many types of 'LASERs' do not answer the question whether every wave length can be made into a LASER. Quite in contrary, the difficulties to produce a sound LASER points to the contrary direction. Quest09 (talk) 16:21, 2 January 2011 (UTC)[reply]
Sou can make a tunable laser that covers a range of frequencies rather than having to find a separate single-mode laser for each frequency. Be careful...sound isn't light. "Every wavelength: sound, IR, radio" is a fundamental misunderstanding of many concepts of physics (for example, the frequency of a household microwave oven is in the mid/upper frequency range of human hearing, but is a completely unrelated phenomenon. DMacks (talk) 18:30, 2 January 2011 (UTC)[reply]
What exactly are you asking for? A wavelength is a measure of distance between two troughs or crests. Waves include, both accoustic and EMR. A LASER for all waves would be a single LASER for EMR tunable to any frequency, and a single SASER for sound. A LASER for all wavelengths would be a single LASER per wavelength range, which is what I thought was what you meant. --Plasmic Physics (talk) 00:15, 3 January 2011 (UTC)[reply]
Note that any given photon can be made to show ANY wavelength desired. You just need to get the right viewpoint (i.e. red/blue shift) so any laser beam can be measured at any wavelength, but you'll need a running start. (This is what makes photons special. It's possible to get any photon down to as close to zero energy as you like, but neutrinos and others will always have a rest mass left over and so can be gotten down as close as you like to zero speed, if not mass.) Hcobb (talk) 02:07, 3 January 2011 (UTC)[reply]
Secure flying without sexual harassment
Instead of body scanning or of frisking innocent passengers, couldn't we just put the passenger into a cabin, let air flow through it, and analyze the resulting air? If we found traces of suspicious substances, then we could selectively frisk him. It looks less intrusive than the present practice. Quest09 (talk) 11:52, 2 January 2011 (UTC)[reply]
That won't work with surgically implanted bombs inside bones. For all we know, Al Qa'ida could have recruited medical experts and performed surgery on volunteer suicide bombers in improvised hospitals in South Waziristan (note that Al Zawahiri is an experienced surgeon). There could be many hundreds of such suicide bombers who live normal lifes for a decade and then, one day, they all board different planes at around the same times and trigger the explosion using mobile phones. Count Iblis (talk) 13:13, 2 January 2011 (UTC)[reply]
Honestly, I hope you said that ironically, and that no one thinks this is a real threat. Anyway, the present practice of frisking or scanning won't catch them all, however a metal-detector will do the trick, without invading privacy. 83.40.250.126 (talk) 13:28, 2 January 2011 (UTC)[reply]
Well, I hope that the intelligence services have learned from the liquid explosives threat and start to think about how they would commit terror attacks if they were operating under similar constraints as Al Qa'ida and take measures to close such loopholes, instead of reacting to actual plots. There are many more security experts in the World than there are Al Qa'ida members, so this should be a successful strategy. Count Iblis (talk) 13:41, 2 January 2011 (UTC)[reply]
Might be that there are more security experts than terrorists, but the latter have at least some advantages: secrecy and the shear number of targets. Quest09 (talk) 15:00, 2 January 2011 (UTC)[reply]
The security people I know basically do nothing other than try to "think like a terrorist". They are fun people to hang out with, but a little disturbing. --Mr.98 (talk) 19:51, 2 January 2011 (UTC)[reply]
The current paranoia is entirely whipped up by the security community, who get their kicks (and their considerable salaries) from demonstrating that they have control over normal human beings. They are just as bad as the terrorists – in fact they do more harm to Western countries than Al-Qaeda could ever manage. They shuld be hunted down and put out of any position to do damage, IMHO. Physchim62(talk)14:18, 2 January 2011 (UTC)[reply]
Arguably, the economic harm caused by the delays at airports and the distress caused by invasive searches is greater than the gain from the very small number of saved lives. It is very rare for the security procedures at airports to actually stop terrorist attacks. Tango (talk) 16:02, 2 January 2011 (UTC)[reply]
I think you're overgeneralizing a bit. There are some security think tanks and consultancies that are obviously just in it for the hype and the dollar. They get lots of nice headlines and debunking New Yorker articles and Bruce Schneier's wrath and all of that appropriate stuff. But there are also a huge number of people both inside and outside of the government who are really trying to come up with reasonable, well-studied, well-analyzed solutions for the real-world security and political scenario we live in (where losing a few thousand lives once a decade is considered to be too high a cost, even if in economic terms it doesn't amount to much). It's not an easy problem with an easy solution, and saying "it's all security theater" is easy to do when it's not your job and nobody's life depends on what you do or don't do. I used to dismiss it all as overblown before I actually met some of these people and talked to them about some of their concerns. Some are definitely more paranoid than others, but most of them are just trying to take the job seriously within the constraints that actually exist. --Mr.98 (talk) 19:51, 2 January 2011 (UTC)[reply]
The "military industrial complex" is not merely perpetuating a security-theater. Might I draw your attention to the FFRDCs? These are neither "think tanks" nor "defense contractors" - they are federally funded research and development centers. It is the job of an FFRDC to provide the government with an un-biased assessment of the technology and policy claims that are made by a "think tank" or "defense contractor." These are federally funded non-governmental organizations that are specifically designed so that their funding is not tied to their policy or technology claims; so they can provide unbiased assessments of issues related to (typically) national security. For a brief time, I worked at one of these agencies, as a staff engineer technical analyst, evaluating "Airborne Survivability." Part of our job was to think about all the ways to destroy a commercial or military aircraft; and then we had to evaluate technical proposals by various major defense contractors that claimed to "reduce the risk." Some claims were exaggerated; sometimes costs were overstated; sometimes everything was right on the money and just needed a subject-matter expert to assess the technical details. Finally, our reports would be written up in a way that a non-technical person (like a congressman or a senator) could understand it. It was a very stressful work environment; "paranoia" is one way to describe it. (Down the hall were people who worked in strategic nuclear deterrence, so by comparison, our group was actually pretty relaxed; even "mass destruction" has a spectrum). Obviously, some policy and technology proposals related to national security are bogus, money-making schemes, or media-generated hype/paranoia; but the Government is neither stupid nor gullible. (Give some credit to the United States Federal Government - they are more stable than any other organization of that size that has ever existed). When a technology or policy proposal is actually bogus, it is eventually outed by a lobbyist group, a government agency, or an FFRDC. At that time, it is up to an elected official to make a policy decision to continue or discontinue funding; if you believe your elected officials are intentionally continuing to fund security theater, your best actions would be to be specific about particular projects that are being funded; then talk to your senator or congressman (there is a link at the top of both pages to help you find your Government representatives). If you are concerned about current airport security policy, you could, for example, pressure your congressman to demand higher priority for new technology- and policy- studies related to airborne security. Nimur (talk) 02:02, 3 January 2011 (UTC)[reply]
There have been such devices designed. They essentially "smell" for explosives. I'm not sure if they are actually in use in any airports, but it wouldn't surprise me if they were. They only work for explosives, though, they won't detect concealed weapons. --Tango (talk) 16:02, 2 January 2011 (UTC)[reply]
I'm skeptical that explosives can always be smelled, too. If proper controls were used when packing it, there should be no residue on the outside, and a properly sealed glass vial shouldn't leak any odor, either. StuRat (talk) 17:17, 2 January 2011 (UTC)[reply]
It's not so much "odor" as it is "tiny microscopic particles." I don't know how many parts per million these machines can detect, or the difficulty it would be to defeat them, but the general idea is, if you've been around explosives, it'll probably be on your clothes in some way; if you have a large amount of explosives on you (enough to do real damage), it'll probably be extremely hard to package them in a way that you will be confident that there will be enough leakage to defeat the machine; the amount of packaging necessary is probably enough to add bulk to whatever you are taking, which would probably draw scrutiny in and of itself. A lot of this kind of security is really just about trying to introduce enough uncertainty into the equation that a very serious group would be dissuaded that it was worth their time. Al Qaeda, for example, is actually a very risk-averse organization — they put their resources into plans they think will actually result in "successful" results, and not be P.R. coups for the "bad guys". --Mr.98 (talk) 19:47, 2 January 2011 (UTC)[reply]
The way to eliminate the sexual harassment aspect of airport security is to use the same system as the Israeli's use, where people trained in human behavior interview each passenger. Those that seem nervous are then given a far more intensive search than the rest. Yes, it is possible to beat such a system, but it's more difficult to beat than the security measures in place in the US right now. Why don't we do this ? It's expensive. StuRat (talk) 18:10, 2 January 2011 (UTC)[reply]
Security measures aren't inherently slow, it's all a question of them having enough equipment and guards to do it in a timely manner. If they had enough, then the interviews would only slow people down by the length of the interview, say 5 minutes. But, of course, having enough guards and equipment makes it quite expensive, so they usually don't, and we get incredibly long lines, as a result. StuRat (talk) 20:47, 2 January 2011 (UTC)[reply]
A couple of my Mom's students who were afraid of flying were pulled out of line for "a more intensive search" a few years ago for exactly this reason. (I think they were in France, not Israel.) I suspect it did not help their fear of flying one bit. APL (talk) 18:53, 2 January 2011 (UTC)[reply]
Puffer machines are at use at a number of major airports. They work a lot like you describe. You step into a little booth and they blow air on you, then they suck the air back up and analyze it. Then the machine goes "Ding!" and you go through and pick up your carry-on and shoes from the x-ray conveyor belt. This usually happens after the metal detector.
An somewhat small airport near me has these, but not enough for all the lines. So you can choose whether you get in the two lines with a puffer, or the two lines without a puffer. I asked a guard if it wasn't pointless to have machines on only two of the lines. He said "Well, we'll catch half of them."
(I haven't been back in the last couple months to see if they've upgraded to body-scanners, or if they've gotten enough for all the lines.) APL (talk) 18:53, 2 January 2011 (UTC)[reply]
The guy hiding a bomb gets to choose whether to enter the puffer? /facepalm --~~
I suppose some people think like that. It might also be that the chances of catching a terrorist are equally high through both systems. It doesn't matter much, since the chances of a terrorist trying to blow a plane is also almost 0%.
That "catch half of them" statement reminds me of the film "Terminal" where a naive Tom Hanks goes to get his invalid visa stamped everyday because with only two different stamps (denied and accepted), he thinks his chance of success is 50/50. Googlemeister (talk) 15:39, 3 January 2011 (UTC)[reply]
Snow as fertiliser ?
Hello, and happy new year. I'm re-reading the Little House in the Prairie books at the moment and I came across a curious occurrence in Chapter 22 of Farmer Boy. I only have the French issue of the book so I can't give an exact quote, but basically what happens is that it's the end of fall, it snows for the first time and in the morning they find six inches or so of snow outside but the soil isn't frozen yet. Almanzo's father is very pleased, he says that snow is "the poor man's fertilizer" and it contains something that will help plants grow if you plough it into the earth. (Poor Royal has to get out in the cold with the horses and plough all the fields for his troubles.) So, is that only country lore or is there a grain of truth in that ? They're located in New York State near the Canadian border (Malone) and the story is set in 1867 so there wouldn't be many industries around sending stuff in the air, would there ? Thank you, have a nice day. 85.169.173.68 (talk) 12:28, 2 January 2011 (UTC)[reply]
I can think of an alternate reason why crops may grow better in years with heavy snowfall. A thick blanket of snow is a good insulator (think of igloos), ensuring that the ground doesn't cool off much below the pre-snowfall temperature. If there are things in the ground which can't stand freezing, then snow may prevent that. Certain seeds, bulbs, and roots, lying near the surface, may be vulnerable to frost, as may worms needed to aerate the soil. So, ground covered in snow may have a better supply of those things, and also water, in the spring, giving the crops a head start that year. StuRat (talk) 17:04, 2 January 2011 (UTC)[reply]
That is true ([2]), but not the answer to the question posed. The poster specifically asked about the value of snow that is ploughed into unfrozen soil; something that wouldn't be done if there were already plants or seeds present. The original response is correct; precipitation carries with it sulfur compounds and – especially – fixed, bioavailable nitrogen that has been 'washed out' of the air: as much as 12 pounds of nitrogen per acre ([3]). The reason to plough it in instead of waiting for it to melt in the spring is that a rapid thaw may cause much of the mineral benefit to be lost to runoff. TenOfAllTrades(talk) 17:30, 2 January 2011 (UTC)[reply]
It's a reason why farmers may have thought that snow made good fertilizer, in that the crops grew better in springs that followed snowy winters. StuRat (talk) 05:54, 4 January 2011 (UTC)[reply]
The maximum claimed amount of nitrogen in snow (per the cited newspaper article) would be way less than a tenth of the minimum recommended nitrogen application rate. The hypothetical "poor man" would be better advised to save his effort or tractor fuel, (or extra feed for the draft animals) and not make a special plowing to plow under the "valuable" minerals in snow, amounting to 1/3 pound per acre of nitrogen. He would also avoid injury to his neighboring farmers since they won't fall down laughing at him. The snow will melt and soak into the soil, carrying into it the supposed nitrogen and sulfur. It would not run off in a filed which was not equipped with underground tile drains. The "poor farmer" would still have to fertilize the filed to get a worthwhile yield. 24.13.81.21 (talk) 22:35, 2 January 2011 (UTC)[reply]
Is the feed cost of draft animals significantly higher if they are plowing rather then just standing around? I mean unlike a tractor, a horse or ox needs fuel whether you are using it or not. Googlemeister (talk) 15:32, 3 January 2011 (UTC)[reply]
I wonder how much of an effect it would have to mix soil with snow that then melts, so that it is full of voids and contains surplus water. Also, 1867 was fairly far into the Industrial Revolution, and before any sort of controls on pollution, and New York would be downwind - I suppose that it is plausible that some unusual substances (even iron?) might be caught this way.
I know that farmers sometimes are sometimes proved famously wrong (there's some recent one about methods of rice production in southeast Asia where the International Rice Research Institute reportedly showed them a better way to farm) - still, on average I would think the farmer is more likely to be right than anyone else. Wnt (talk) 17:55, 3 January 2011 (UTC)[reply]
I need a strong argument about throwing away incandescent lights to replace them with CFLs right away.
Someone I know thinks it's wasteful to throw away incandescent bulbs before they're used up, even though I know that it's more wasteful to keep using more energy when the CFLs (or even LED light bulbs) will start saving right away.
Therefore, how do I counter the argument? I once saw that incandescent bulbs were 25¢ each ($1/4-pack) at Wal-Mart, but assume they're 50¢ each.
Assuming 10¢/kWh, how long would a CFL take to save 50¢, thus justify tossing a single incandescent bulb? (How long would an LED take?)
And using those numbers, with my electric rate (8.75¢/kWh), I'd save .65¢/hour per CFL used versus an incandescent. At that rate, it takes less than 80 hours of use to come out ahead with 50¢ CFLs. — Lomn14:25, 2 January 2011 (UTC)[reply]
The 25¢ or 50¢ cost of an incandescent bulb is actually irrelevant to the decision of whether to simply discard an incandescent bulb that has already been bought, because the cost of an already-bought bulb is a sunk cost, which should not affect financial decisions. What is important is the prospective cost of buying the CFL bulb. A CFL bulb costs much more than an incandescent bulb, like around $1.97 per bulb at Walmart.[4] The bulb I linked to uses 26W to replace a 100W incandescent bulb, which at Lomn's 8.75¢/kWh rate saves electricity at the rate of 0.6475¢ per hour of use. So the $1.97 CFL bulb will pay for itself after 304 hours of use. So to emphasize the nature of the incandescent bulb's sunk cost, even if you had an unlimited supply of free incandescent bulbs available to you, it would still be cheaper to just throw away all those wasteful incandescent bulbs, as long as you're planning on keeping your light on for at least 304 hours. Red Act (talk) 16:19, 2 January 2011 (UTC)[reply]
I don't think that is quite right. You are correct that the cost of the incandescent bulb is irrelevant, since it has already been spent. What you need to do is predict how much longer the incandescent bulb would last. You then take that time divided by the lifetime of a CFL bulb and multiply it by the cost of a CFL bulb. That gives you the cost of switching early. You then work out the energy saving during the time the incandescent bulb would have lasted. If the saving is larger than the cost, it's worth switching. An incandescent bulb has a lifespan of about 1000 hours. Let's assume it's half way through its life, so has 500 hours left. A CFL bulb has a lifespan of about 10,000 hours. Therefore, the cost of replacing the bulb early is $1.97*500/10000=9.85c. The saving is 0.6475c*500=$3.24. The net gain is therefore $3.14, which is positive, so you should switch early. (Assuming the numbers other people have quoted are correct.) --Tango (talk) 17:34, 2 January 2011 (UTC)[reply]
A few thoughts:
1) Somebody told me that the wattage figures for CFLs are greatly understated, because they omit the electricity used in the ballast. Can anyone confirm this ? If so, what's the true wattage of CFLs ?
2) There seem to be some sizes of CFL which cost about 10x more, such as those over 100 watt equivalent. So, this will alter the calculations, if you need to replace high wattage incandescents.
3) Certain incandescents just can't be replaced by CFLs. CFLs have problems with cold temps (as in a garage or dog house, where the heat from the incandescent is actually used to keep it warm in winter), dimmer switches, and certain fixtures that require a "bulb" shape. So, instead of tossing out the incandescents, perhaps the ones which are replaced with CFLs can be saved to replace those, as they burn out.
4) Some incandescents have so little usage, that replacing them may not make sense. You may have one in a utility room or attic that you never enter, for example.
5) The energy "wasted" by incandescents turns into heat. That heat can actually be a good thing in winter, if it provides heat where you need it (presumably you are in the room with the lights on), and thus can turn the thermostat down and cool off the rest of the house. In summer, however, that's a bad thing. So, replacing incandescents with CFLs in fall and winter doesn't make as much sense as in spring and summer. StuRat (talk) 16:56, 2 January 2011 (UTC)[reply]
Regarding StuRat's point #1, apparently this relates to a CFL's power factor. However, I'm seeing contradictory claims about the implications of this issue. Some say this power factor issue results in a CFL drawing more power than its rating [5]; others say this is bunk [6]. From my cursory and inexpert look at power factor, it seems like the rated wattage correctly reflects how much energy is used and that lower power factors merely make power delivery a bit trickier. I'm sure an expert or a link to an explanation on a clearly reputable website could clear this up. --Allen (talk) 18:30, 2 January 2011 (UTC)[reply]
I'm not an expert, but it seems to me that the "bunk" website contains some truth and some error - especially the claim that electric motors cancel out CFLs. As far as I know, both are inductive load, and thus have voltage leading current. It is true that the excess current is returned to the system, but the doubling of power loss in the distribution at a power factor of 0.7 means that a small amount of extra power needs to be supplied unless the factor is corrected. Switch-mode power supplies also cause problems in the distribution system. A larger disadvantage of CFLs (in my view) is the fact that the claimed lumen output is only about half as bright as the "equivalent" incandescent to my eyes, so I need twice as many to give the same "comfortable light". (Perhaps my eyes are just suffering from age!) There is also the problem that the light output falls rapidly with age. The future is with LEDs, but I don't find the light from these very comfortable either. I prefer a wide frequency range in the light output, but I am gradually replacing incandescent with CLF, and LED which is even more efficient. I also envy Americans for their cheap electricity! Dbfirs21:19, 2 January 2011 (UTC)[reply]
Thanks. A google search for "CFL inductive capacitive" reveals various claims that the CFL load is "inductive", "capacitive", "inductive/capacitive" or neither inductive nor capacitive so much as harmonically distorted. I'm not sure who's right, but it seems to me that Dennis Towne's basic argument doesn't rely on his claim about cancellation. --Allen (talk) 22:45, 2 January 2011 (UTC)[reply]
I think the capacitor was used to correct the power factor closer to unity on early (inductive) CFLs (I cannot imagine any CFL circuitry that could possibly be capacitative in phase shift), but I agree that modern CFLs use much more complex circuitry more like that of switch-mode power supplies, so the distortion is much more complex than just a phase shift. I also agree that the total savings (including both consumer costs and supplier costs) are at least half, even taking into account all of the disadvantages, so the general argument is valid. Dbfirs09:23, 3 January 2011 (UTC)[reply]
There seems to be a case for keeping an incandescent bulb in service rather than throwing it away and advancing the purchase date of a CFL. The CFL cost is likely to be higher than some have stated, unless a government agency is subsidizing them, or a merchant is using them as a loss leader on sale. Some consumers have told me they plan to stockpile 100 watt incandescent bulbs before their sale is outlawed in the USA at the end on 2011. The have a very, very long shelf light, and many people prefer the quality of their illumination and the lessened flicker. CFL recycling presently has a cost of 75 tents to a dollar each, which has to be paid to the recycling company by the merchant or agency accepting the CFL dud. This is often ignored in claims of the savings from switching to CFLs. It is an indirect cost, since few merchants try to make people pay the recycling cost. If they did, most consumers would just hide the dud CFLs in their trash bags. Some prices quoted are for "no name" brand CFLs, of doubtful reliability. A 100 watt equivalent GE CFL drawing 26 actual watts sells for $2.41 each, in a 6 pack from Amazon, while a GE 100 watt soft white incandescent bulb is 50 cents each in a 4 pack. Some prices quoted must include loss leader sales or governmental subsidies. An incandescent bulb can just be thrown away as trash with a massively lower cost for disposal in a landfill. The wattage figures published for CFLs are accurate, The volt amps will be larger than the watts due to the low power factor of the ballast, while an incandescent bulb has a power factor close to 1. Your electric meter records kilowatt hours, not kilovoltamp hours, so you are not charged for the extra apparent power used. A commercial client might have the power factor monitored and have to pay a penalty for a poor power factor, such as if he has large motors in use and does not have adequate power factor correction capacitors in use. A low power factor due to inductive loads (usually due to motors such as air conditioning) causes extra expense to the utility, since they have to have oversized conductors and transformers. Their recourse is to install capacitor banks at substations or on power lines. This has an indirect cost to the consumer in higher electric bills eventually when the utility files for higher rates due to higher operating expenses. 24.13.81.21 (talk) 22:23, 2 January 2011 (UTC)[reply]
I've read that some blind people can see using their tonge. A camera sends electrical signals to nerves in the tongue and the blind person, over time, starts to see pictures. So, the brain is able to process information from one sense as if it arrived via another sense. Also, in case of hearing, visual information can strongly influence what we hear, as the McGurk effect clearly demonstrates, see also this video to check it out for yourself. It thus seems plausible to me that a lipreading deaf person could actually hear what he/she is lipreading, but I have never read about this. Count Iblis (talk) 13:28, 2 January 2011 (UTC)[reply]
That video is really wierd. If I look at the left image with my left eye and the right image with my right eye, I can hear both words simultaneously. I recently read of an experiment where images were digitally processed and then "projected" on to the subjects stomach via transducers on the skin. This was very low resolution, but apparently the subjects could form the image in their brain after a little practice just as if it had come from their eye rather than their stomach. Sorry, I don't have a link to hand. SpinningSpark15:05, 2 January 2011 (UTC)[reply]
Just a few days ago there was an Oliver Sacks column in the New York Times which discusses this a bit, with a specific example of a lip reader who experiences the reading as "hearing": Lip-reading, seeing mouth movements, was immediately transformed for this patient into “hearing” the sounds of speech in her mind. Her brain was converting one mode of sensation into another. In general I suspect that Oliver Sacks books are the kind of thing you'll find interesting, if you find this kind of question interesting... he's full of very interesting and odd examples of how strange our brains can be. --Mr.98 (talk) 19:37, 2 January 2011 (UTC)[reply]
Possibly linked, I find that when I watch a foreign film with subtitles, I remember it as though I was hearing the characters speak the words in English, and have, however hard I try, almost no recolection of them actually talking in foreign at all, though I remember the tones of voice, the speed and accents and so on, alongside the english translations of the words. 79.74.213.144 (talk) 21:07, 3 January 2011 (UTC)[reply]
According to this site, "The lines that you see in this and several other photos are vapor trails of sounding rockets. Sounding rockets or smoke flares may be launched just before a device explodes so that their vapor trails may be used to record the passage of the otherwise invisible shock wave." -- 119.31.126.66 (talk) 15:57, 2 January 2011 (UTC)[reply]
During the original Trinity test of the first atomic bomb, a few high speed photographs of the early explosion captured both the explosion and fireball itself, as well as cable supporting a balloon some distance behind the test. In this series of images, the cable is visible as a slightly slanted line running up the right side of each frame. It was noted that as the shock wave from the blast passed, the highly-compressed air refracted light from the cable away from the viewer and created an illusory break in the cable. You can see this effect in the second and third images, where it is marked with an arrow. Note that the apparent break isn't a real effect on the cable; you can see that between frames that it has moved upwards. From what I gather, capturing the shock wave in this way was entirely serendipitous ([7]), and deliberate smoke trails weren't introduced for this purpose in U.S. nuclear tests until several years later. (Here's a later example which includes enlargements of the breaks or 'hooks' in the smoke trails. TenOfAllTrades(talk) 16:32, 2 January 2011 (UTC)[reply]
Note that you can see from this picture what is probably the "correct" viewing angle for those particular rockets. They set out a "grid" on which you can see the propagation of the shock wave. By the time of these photos, the shock wave as almost certainly already passed (it goes through in a few milliseconds, whereas the "mushroom" really starts to form after about a second). --Mr.98 (talk) 16:18, 3 January 2011 (UTC)[reply]
That is an excellent question. I've just looked at the paper proposing the Weakless Universe (linked to in our article) and it doesn't seem to address anti-matter at all. The symmetry violation of the weak interaction is only one proposed explanation for baryon asymmetry, so it's doesn't completely invalidate the idea, but I'm surprised they didn't mention it. As for strange quarks, apparently they would almost all be bound into Lambda-0 particles which could form "hyper-tritium" but would do so only rarely, so the strange quarks are not expected to interact much with anything else and would be a form dark matter. --Tango (talk) 19:56, 2 January 2011 (UTC)[reply]
As far as I know, the CP violation in the CKM matrix is far too small to explain the matter-antimatter imbalance. That requires unknown physics which (the authors could argue) could just as well be found in the weakless universe. -- BenRG (talk) 01:54, 3 January 2011 (UTC)[reply]
I don't know if it was ever used deliberately, but it is certainly possible for a projectile to ricochet off water, similar to rock skipping. Shooting at water is dangerous however, and ricochets off water can be extremely unpredictable. Not that I haven't fired a gun into a puddle many times, but it is actually a really dumb thing to do. Beeblebrox (talk) 22:07, 2 January 2011 (UTC)[reply]
No (in answer to the direct question). All of the examples given above and below require a low angle of attack, which would not provide an opportunity for the projectile to return to origin directly. One might be able to imagine a counter-current whirlpool and path with a series of skips, but it seems completely implausible. -- Scray (talk) 23:18, 2 January 2011 (UTC)[reply]
The film about the bouncing bomb,The Dam Busters (film), has Barnes Wallis, the inventor stating that Nelson used the technique, pitching his cannonballs short to make them bounce up at the enemy ship near the waterline. I have seen similar claims in other, not particularly reliable, sources but no Wikipedia article seems to cover it. SpinningSpark23:42, 2 January 2011 (UTC)[reply]
Ricocheting is just like reflecting - it always bounces at the same angle it hit at. Since the surface of water is always horizontal, the only way it could bounce straight back at the shooter would be if you shot straight down (and it wouldn't bounce then anyway, it would just sink). --Tango (talk) 23:55, 2 January 2011 (UTC)[reply]
The surface of the water is only entirely horizontal if it is dead calm. Waves add an element of uncertainty to any attempt to ricochet off water. I forgot about the dam buster bomb idea of the British in WWII though. I think this is something that has been tried, but results were probably mixed at best. It would be ill-advised if there was any significant wave action, especially considering the possibility of a ricochet striking an allied ship. I say we call up the Mythbusters and have them check it out. Beeblebrox (talk) 00:01, 3 January 2011 (UTC)[reply]
First-hand accounts I've read of the Battle of Trafalgar (in The Mammoth Book Of How It Happened Trafalgar edited by JE Lewis) indicate that they only fired the cannon when they got really close to the enemy ships. So I expect the range of a cannonball would not be enough to ricochet off the water at a shallow enough angle. As the ships were likely to be rolling in the waves, and as there was a delay between lighting the fuze and the cannon firing, then many cannonballs were probably inadvertently fired into the sea. But I cannot think that having a cannon ricocheting would be of any practical use, since even if it worked it would simply reduce the range of the cannon and not have any advantage over a direct hit. Perhaps in the past people would like to make a pleasing analogy with bowling in cricket. I'm not sure if they ever deliberatedly aimed their cannon under the waterline of enemy ships to make them sink, perhaps because they hoped to capture them as 'prizes' where their value would be paid to the captain and crew. I think much of the cannon shots were aimed at the rigging of the ships, in the hope of bringing the masts or sails down and immobilise them. See also Naval artillery in the Age of Sail and cannon. 92.15.31.128 (talk) 12:31, 3 January 2011 (UTC)[reply]
Going back to Barnes Wallis, this site debunks the idea in the film that Nelson invented the idea, but Wallis did write that "ricochet gunfire was known as early as the 16th century and was used in naval gunnery in the 17th and 18th centuries to extend the effective range". SpinningSpark17:56, 3 January 2011 (UTC)[reply]
Although I'm not up to digging out specific quotes (because I'm somewhat ill at the moment), I recall from reading C. S. Forester's (well-researched) Hornblower novels and other Napoleonic naval warfare fiction and factual books that this low-angle ricochet technique was employed when appropriate - usually I believe at more extreme ranges when a higher angled shot would be liable to drop short or pass over the target, and when no other friendly ships were potentially in the line of fire. The main wave-induced uncertainty would be whether the shot would bounce at all (if it happened to hit the face of a wave it might not), and if so at how high an angle; the degree of lateral deflection would I think be quite small. Many British navel gunners were highly skilled and able to allow for ship movement and fuse delay, and it would often have made sense to try to inflict damage at long range when the enemy gunners lacked the expertise to retaliate in kind. 87.81.230.195 (talk) 20:35, 3 January 2011 (UTC)[reply]
Given how inaccurate the aiming must have been, and the rolling of the ship, then the difference in aim between a ricochet shot and one simply aimed horizontally at the enemy must have been too small to differentiate, so the horizontal shots may have ricocheted by luck, particularly when waves between the two ships would rise or fall unpredictably. Anyone who has been on an ocean like the Atlantic rather than just in the sheltered North Sea will appreciate how big the waves are and how much the ships would be rolling around and going up and down too, making deliberate attempts at ricocheting almost impossible. 92.29.114.99 (talk) 23:39, 3 January 2011 (UTC)[reply]
It depends on the effects. For adults it's more likely to be temporary, but it depends on exactly what happened. BTW If you are experiencing a medical issue, then you'll need to go to a doctor, we can't diagnose you. We can mainly help with curiosity or hypothetical cases. Ariel. (talk) 02:26, 3 January 2011 (UTC)[reply]
January 3
Quantum Electrodynamics
I suspect I worked out the special relativity version of the Schrödinger equation. I want to check it, but I want another stab at it if I was wrong.
Is it some variation of ?
I'm pretty sure it's on the Schrödinger equation equation page, but I can't look myself for obvious reasons. If I just flipped a sign or something, go ahead and tell me the answer. But if it's completely wrong, don't.
While I'm at it, I have another question. I was trying to work out how the whole nothing -> particle + antiparticle thing works. Is nothing made up of particle-antiparticle pairs? That would require that, for example, the binding energy of positronium is about one MeV. I'm pretty sure it's supposed to be a quarter of a Rydberg energy or something like that. Does the weak force make another ground state when they're really close to each other or something? — DanielLC02:03, 3 January 2011 (UTC)[reply]
I don't think the Dirac sea thing helps. My problem is that there's three dimensions for each particle, so if you added a particle antiparticle pair, you'd add six dimensions. I'm pretty sure the laws just give how to change the amplitude of a given point in configuration space. You can't have it change the number of dimensions. Not unless you use the Copenhagen interpretation, and there has to be a better answer than that. — DanielLC22:14, 3 January 2011 (UTC)[reply]
If you drop the U, what you've come up with has a fair amount of similarity to a one-dimensional version of the Klein–Gordon equation, but there are a couple of important differences. I think you might as well just look at the article, since I think the Klein–Gordon equation isn't really all that important of a stepping-stone toward QED anyway, mainly because it describes a spin-0 particle, so it's not worth knocking yourself out over. Red Act (talk) 19:10, 3 January 2011 (UTC)[reply]
Ordinarily, of course, one hears relatively little from the window of a moving car, since the background sound of rushing wind is so loud. But is it possible to design some sort of microphone pods that completely avoid turbulence, or cancel or filter all white noise, so that if they were connected to speakers inside the (well-soundproofed) car you could hear everything around the car while moving at highway speed as if you were parked? Wnt (talk) 06:50, 3 January 2011 (UTC)[reply]
I don't think that approach would work well, here, as such systems require a way to distinguish between the noise to be canceled and the sound to let through. When listening to music from the radio, is straight-forward, the sounds coming out of the radio are the ones to keep and the rest need to be canceled. However, in this case, the noise from wind turbulence around the car probably sounds identical to that from wind blowing through the trees. Reducing the background noise, by streamlining the car, would assist you, as would putting a (streamlined) microphone outside the car and driving as slowly as possible. StuRat (talk) 16:02, 3 January 2011 (UTC)[reply]
Well it could do if the target is well separated from the vehicle. Adding noise in antiphase to cancel it requires pickup mics close to the noise source (ie the engine, tyres, body) and the target to be away from the car. Noise cancelling mics work by rejecting noise from the rear and sides. This is going to work best if the mic is on a boom pointing away from the car, or at least pointing out the window. Not terribly practical for an everyday vehicle, what's your intended application? some kind of espionage? SpinningSpark16:57, 3 January 2011 (UTC)[reply]
Nay, just curiosity during a long drive - though I was thinking that if an answer existed it might be based on some existing spy tech perhaps for airplanes. I understand that the Doppler shift would be noticeable, but that is just part of the curiosity. The noise cancelling approach is interesting, but I think that any air turbulence directly at the microphone would be unique and could not be cancelled against any other microphone. Though the engine and tire noise could be dealt with so, I was supposing that a well insulated stalk on a microphone could do the same. The real question to my mind is whether a moving object can be designed aerodynamically so that there is a region of perfect laminar flow over part of it, which can be insulated acoustically from the rest, and whether a microphone membrane can be placed there so as not to interfere with the airflow but which can pick up the sound. Wnt (talk) 17:45, 3 January 2011 (UTC)[reply]
Streamlining can be far better than it is now, but it requires compromises like less ground clearance and passenger room. Also, the radiators we use now that rely on air smashing headlong into them have to go. Instead, a larger radiator along the inside of the hood might make sense. Windshield wipers and door handles also need to go (or at least should be covered up when not in use). Instead of being open at the bottom, the car must have a panel underneath. Then there's the gaps between body panels. A single shell that's lowered onto the frame (and driver) would fix that. StuRat (talk) 17:58, 3 January 2011 (UTC)[reply]
The usual idea for microphones in wind is not to encourage laminar flow, but rather to break it up to something less energetic. This is the reason for the fur covering seen on microphones used by outside broadcast crews. See here also. SpinningSpark18:40, 3 January 2011 (UTC)[reply]
It's essentially impossible. If you know the spectral characteristics of the signal you want to receive, you can amplify in a way that focuses on that spectral range, but because white noise covers the entire spectrum and is completely unpredictable, you will still pick up the part of it that overlaps with your signal. If you don't know the spectral characteristics of the target, it is completely hopeless. (As StuRat said, the noise-canceling principle can't be applied in this situation.) Looie496 (talk) 19:50, 3 January 2011 (UTC)[reply]
I don't think the OP really means white noise, I am reading that as merely a substitute for all the various sources of noise found in a vehicle. SpinningSpark20:37, 3 January 2011 (UTC)[reply]
I think what you are wondering is if you can make the car "slip" through the external sounds, so they would flow around the car and you wouldn't hear them. This would only happen if the local section of air was traveling faster than the speed of sound - and that would be quite noticeable due to the sonic boom. A concorde is quieter to its own passengers because it outraces its own noise. Ariel. (talk) 20:42, 3 January 2011 (UTC)[reply]
I am skeptical of the statement that the Concord was quieter because it was outpacing its sound. Sound from aircraft engines is easily conducted through the aircraft itself. Googlemeister (talk) 21:01, 3 January 2011 (UTC)[reply]
Some sound is, but most isn't. A jet engine is extremely loud (over 140db) - if a lot of sound was conducted you'd need ear protection on flights. Also a lot of noise is turbulence from the wings and other surfaces, and that noise is generated slightly removed from the wings. Ariel. (talk) 21:34, 3 January 2011 (UTC)[reply]
Edit: I tried to find a ref for it. The best I info I found was a forum post that said that the back of plane was much louder than the front ('And the very back of the cabin was dubbed "rocket class".'[9]), but otherwise the sound level was mostly normal/typical. Apparently they also worked hard when designing it to minimize sound, so it's hard to separate that from speed of sound quietness. Ariel. (talk) 21:47, 3 January 2011 (UTC)[reply]
where did all the mass go?
If the infant universe had infinite volume and infinite density, then it must have had infinite mass (since density is a function of mass and volume). However, our present universe does not have infinite density, so where did all the mass go?thank you. —Preceding unsigned comment added by 117.201.161.237 (talk) 11:05, 3 January 2011 (UTC)[reply]
Where? And to answer your question, it did not have infinite volume. It was a singularity, so it was just a point with infinite density. When it rapidly expanded, it didn't have infinite density anymore. --T H F S W (T·C·E)18:28, 3 January 2011 (UTC)[reply]
Here [[10]]. As I understand it infinite density is a backward extrapolation of the expansion of the universe we have observed. If this is true our observable universe started as a infinitesimal point, but we do not know how big the whole universe are and if it is infinite it is possible that the volume was infinite even when the density was infinite. The obvious answer to the question is that the mass is outside the observable universe and that every volume has expanded an infinite number of times so the density can be finite. --Gr8xoz (talk) 21:48, 3 January 2011 (UTC)[reply]
Theory of everything
Haven't electromagnetism and both nuclear forces already been unified? Why is it still so hard to unify gravity with a single force instead of three forces? --75.60.13.19 (talk) 15:03, 3 January 2011 (UTC)[reply]
Because gravity isn't even well explained by itself, never mind how it fits into a possible Theory of Everything. One of the key problems with gravity is that it is ignored by the standard model, which holds that forces are propagated by Force carriers; that is particles which transport the "force" between the things so affected by the force. EM is mediated by photons, the strong nuclear force by gluons, and the weak nuclear force by the W and Z bosons. There has not yet been any confirmed existance of a graviton, or even a consistant theory which predicts its existance, beyond the "the other forces have one, so gravity must too". General relativity gets around this problem by making gravity a pseudoforce, much like Centrifugal force; that is gravity represents objects moving in straight lines at constant speeds (and thus, unaffected by forces), but doing so in a curved 4D spacetime, a concept known as Geodesics. The problem is that, so far, both General Relativity and the Standard Model are really good, working theories, but they resist incorporation with each other. --Jayron3215:30, 3 January 2011 (UTC)[reply]
Coloured light
I know that if I look at, for example, a picture of a yellow object on my monitor, what I'm really looking at is nothing yellow, but instead little red and green lights packed so closely together that my eyes can't tell the difference and think they're seeing yellow. But if I'm looking at an actual physical object that really is yellow, am I correct that the light coming into my eyes really is yellow?
This caused me to imagine a situation where this blending of different-coloured lights didn't exist. We could only see pure hues of the entire spectrum, at different brightnesses. An easy way to simulate this is by loading a picture in your favourite graphics editor and setting the saturation in the entire image to 100%. I tried this on a couple of photographs, and it didn't look that much unrealistic. JIP | Talk19:25, 3 January 2011 (UTC)[reply]
Our eyes and brain interpret colors by the amount of stimulation received by the three types of cone cells in our eyes. Light that is true yellow, that is say about 580 nm wavelength, will tend to equally stimulate the "red" and "green" photoreceptors roughly equally. However, so won't light which is 50% red and 50% green; the result is that we cannot actually tell the difference between "spectral yellow" and "non-spectral yellow". See also Color vision and Spectral color for more. --Jayron3219:39, 3 January 2011 (UTC)[reply]
Sorry, "So won't" is part of my New England dialect. The "positive negative" is a regionalism present in that area. It means the same thing as "So will". --Jayron3220:40, 3 January 2011 (UTC)[reply]
Is that just a New England thing? I had no idea. From here in Connecticut, when I saw JIP's objection I thought "What's the big deal? It means the same either way." APL (talk) 23:07, 3 January 2011 (UTC)[reply]
It certainly doesn't mean the same here in England. "So won't" is not idiomatic here in any meaning, but it never occurred to me that it might mean "so will". --ColinFine (talk) 00:08, 4 January 2011 (UTC)[reply]
Having the same (apparent) color, but made up of different combinations of frequencies is called Metamerism. If you want to see the pure color in your photo, use a magnifying glass. Just changing the saturation won't do that because the ratio between the colors stays the same. Ariel. (talk) 20:39, 3 January 2011 (UTC)[reply]
Many objects that you believe are "really yellow" are just reflecting similar amounts of red and green light, plus frequencies in between, but very little blue light. I don't think I can distinguish between "true yellow" and normal reflective "yellow" (except in the extreme cases such as sodium lamps where the frequency range is very narrow), though looking at "pure red" and "pure green" objects by the reflected light should enable an estimate of the range of frequencies being reflected. I remember doing an experiment nearly fifty years ago, in which I held a pure red filter to one eye and a pure green to the other, and could see yellow perfectly normally, proving that it is in the brain that the signals are combined.Dbfirs22:04, 3 January 2011 (UTC)[reply]
But I thought Binocular rivalry proved that each eye is separate! Maybe it only applies to shape and not color? (It mentioned something called "binocular colour rivalry", although without details.) Or maybe only if the images are very different? Ariel. (talk) 22:45, 3 January 2011 (UTC)[reply]
Some anaglyph images are "true color" in the sense that all the R information comes in one eye and the G and B data comes in the other eye. It never feels quite right, but it's close. APL (talk) 23:10, 3 January 2011 (UTC)[reply]
I think the brain always tries to combine the images, but can be forced to concentrate on just one set of signals, either at will, or involuntarily if there is a big discrepancy. The variation in density of cones and pigment suggests that we all see colour differently, but we adjust our perception to match that of others, so there is an enormous amount of pre-processing goes on in the visual cortex before the conscious mind "sees". Dbfirs09:08, 4 January 2011 (UTC)[reply]
Another practical example involves the so-called "white light" emitted by fluorescent lamps, which is actually made up of various bands of color. Many things don't really show the proper coloration that they would under genuine sunlight, or a good natural-frequency incandescent bulb for that matter, because they aren't reflecting or absorbing real yellow light. Wnt (talk) 14:51, 4 January 2011 (UTC)[reply]
Chimney drought or draft
The article on Chimney drought or draft (Chimney#Chimney_draught_or_draft) confused me a little. It says that "the combustion flue gases inside the chimneys or stacks are much hotter than the ambient outside air and therefore less dense than the ambient air. That causes the bottom of the vertical column of hot flue gas to have a lower pressure than the pressure at the bottom of a corresponding column of outside air."
In a closed system, hotter air would be at a higher pressure, assuming the same sized container and the same quantity of gas. The deal is, the chimney is open at both the bottom and the top, so it isn't a closed container. As the hot air rises out of the chimney, this creates a lower pressure at the bottom of the column of air in the chimney, essentially because as the warm air leaves via the top, it removes air faster than it can be replaces by cold air at the bottom. What you have in this case is that the quantity of air is actually lower, proportionally, than the temperature of the air is higher. Mathematically, considering the ideal gas law PV=nRT, the "n" term is droping faster than the "T" term is rising, resulting in a lower overall "P" term. --Jayron3220:31, 3 January 2011 (UTC)[reply]
The missing link in your description is that you havn't explained why hot air is less dense than cold air. Hot air has faster-moving air molecules which ricochet off each other and their container and spread out more giving lower density for their volume. 92.15.22.77 (talk) 20:46, 4 January 2011 (UTC)[reply]
Is there an equation that would tell how much thrust (downward) a chimney generates if the volume of air intake, and its temperature and pressure is known? Googlemeister (talk) 20:55, 3 January 2011 (UTC)[reply]
I'm sure their is; its a question of fluid dynamics, however I have a background in chemistry, and not chemical engineering. A chemical engineer would likely be able to work out such a problem, and/or have an equation at hand. --Jayron3220:59, 3 January 2011 (UTC)[reply]
Where might I find out the dates of various phases of the moon for the period June-February 1593? No lunar calendar I have been able to find online goes back anywhere near that far.
The time between full moons is 29.530589 days. You could probably back-calculate from a known full moon to find the dates of the full moons in that time period. --Jayron3221:24, 3 January 2011 (UTC)[reply]
I use a program called "stellarium" which shows you how the sky looks at any particular time and place and allows you to fast forward or rewind time. I've never tried to go back centuries though, not sure if it will accurately go back that far. I'm at work so can't check. It's free and easy to install if you want to give it a shot. Vespine (talk) 21:35, 3 January 2011 (UTC)[reply]
I just came to write that. But that was 1582 which is before the 1593 date requested. But if you do go back farther be careful of that. Ariel. (talk) 21:50, 3 January 2011 (UTC)[reply]
That's only correct for a few countries. Most Catholic contries changed within a few years after 1582, but most Protestant countries waited until the 18th century (1752 for Britain and its colonies, for example). See details here. --Anonymous, 07:04 UTC, January 4 (Gregorian), 2011.
List of 16th century lunar eclipses says that in 1593, partial lunar eclipses occurred on May 15, June 13, Nov 8, and Dec 8. Since lunar eclipses can only occur when the moon is full, this should do a pretty good job of pinning it down, assuming the dates are correct. Looie496 (talk) 22:49, 3 January 2011 (UTC)[reply]
The site you want is Fred Espenak's eclipse pages at NASA, and specifically the Catalog of the Phases of the Moon going back over 4,000 years (and almost 2,000 years into the future), and under that, specifically this page for the years 1501-1600. Note that he uses the Gregorian calendar beginning with the end of 1582, and assumes that all years start on January 1; if that's wrong for the location you're interested in, you need to correct the dates accordingly. Also note that times are given in UT; for dates of phases of the moon at some location other than the Prime Meridian, you need to correct to local solar time according to the longitude of the place at a rate of 15°/hour. For example, if it says "Jan 17 01:27", the date is January 16 for any location west of longitude 1h27m x 15°/hour = 21°45' W; if it says "Jan 17 23:27", the date is January 18 for any location east of longitude 0h33m (time until midnight) x 15°/hour = 8°15' ). --Anonymous, 07:17 UTC, January 4, 2011.
(The reason for "15°/hour" rather than using time zones, of course, is that they didn't have time zones in the 16th century.) --Anon, 10:58 UTC, January 4, 2011.
Aspirin
hey all. Over the holidays I was over at my grandparents' house and my grandfather has high blood pressure. He explained to me that he takes aspirin to reduce his risk of heart attack. I'm only in pre-med, but I'm curious: how does this work? I've heard that if you think you're having a heart attack you should chew an aspirin but I assumed it was a blood thinner. Wouldn't regularly taking a blood thinner be dangerous, though? Thanks. 24.92.70.160 (talk) 22:28, 3 January 2011 (UTC)[reply]
See the "Prevention of heart attacks and strokes" section of our aspirin article and also our Mechanism of action of aspirin article. You're right that it can act as a blood thinner, but that may be the lesser of two evils (the other being having a heart attack) and may even be a direct benefit (reducing clotting or other flow inhibition that can lead to heart attack). DMacks (talk) 22:29, 3 January 2011 (UTC)[reply]
Asperin does thin the blood, yes. There are dangers to taking blood thinners, but it is a standard treatment for some heart problems. A aspirin a day is a very common prescription. If that isn't enough, Warfarin is taken for heart problems to thin the blood. --Tango (talk) 00:05, 4 January 2011 (UTC)[reply]
I haven't heard about chewing an aspirin if you think you are having a heart attack. In the movies they take nitroglycerin at the onset of a heart attack. At Nitroglycerin it states Nitroglycerin is also used medically as a vasodilator to treat heart conditions, such as angina and chronic heart failure. It is one of the oldest and most useful drugs for treating heart disease by shortening or even preventing attacks of angina pectoris. Nitroglycerin comes in forms of tablets, sprays or patches.Dolphin(t)07:22, 4 January 2011 (UTC)[reply]
Pet peeve - aspirin does not "thin" the blood; your blood does not somehow become more dilute with the ingestion of acetylsalicylic acid. Aspirin serves to reduce platelet aggregation; that is, it reduces the "clumping" action of platelets. While the meaning is generally understood, you'll note that our article carefully avoids the use of this phrase. Matt Deres (talk) 14:26, 4 January 2011 (UTC)[reply]
Light speed
I'm assuming that time and speed are inversely proportional. On that, I can predict the reason light speed can never be met is that you can't add more acceleration because you can't have a "0" time. Is this correct? Albacore (talk) 22:50, 3 January 2011 (UTC)[reply]
That doesn't make sense to me. I read your proposal as implying speed of light is infinite. That's obviously not true, it has a definite and measurable speed, so there is certainly time there for any given distance travelled. The light-speed problem is that you simply cannot reduce that time below a certain level. DMacks (talk) 23:00, 3 January 2011 (UTC)[reply]
(ec) No. Massive objects can not reach light speed, because as they accelerate arbitrarily close to light speed, it takes an increasingly larger amount of energy for each incremental unit of acceleration. This means that it would require an infinite amount of input energy to reach a finite velocity. It has nothing to do with "subtracting time", although the mathematical formulation of the Lorentz transform can be used to model the effect known as time dilation. Nimur (talk) 23:01, 3 January 2011 (UTC)[reply]
Yeah you're talking about time dilation, and I'm not a physicist but I think this is one way you can look at it. Another factor to consider is Length contraction. I remember reading some mind bending stuff about how the universe is actually stationary in time from the reference of a photon, or any photon. So from a photon's perspective it's actually everywhere at once, or it's actually only one photon everywhere at once, or something like that, don't quote me I've probably got it wrong, but it was pretty far out. Vespine (talk) 23:34, 3 January 2011 (UTC)[reply]
Time dilation at light speed is infinite, which basically means time doesn't make sense for a photon. You could say that, from a photon's point of view, a photon is a line through spacetime rather than a point. If exists simultaneously at every point along its worldline, since without a concept of time everything is simultaneous. Mathematically, though, we just say the proper time for a photon is undefined and leave it at that. --Tango (talk) 00:10, 4 January 2011 (UTC)[reply]
Actually, what physicists say is that photon's do not have a point of view; that it is literally impossible to consider light itself as a reference frame, and thus it is nonsensical to even consider what the posibilities are. You generate far to many real paradoxes when you try to do so, it becomes kinda impossible to even think about it in those terms. --Jayron3203:49, 4 January 2011 (UTC)[reply]
I'm reading the appendix, entitles Physics and Perception, of David Bohm's "The Special Theory of Relativity". Bohm uses the term relatively invariant a lot, but I'm not sure what he means by it. I'll give you an excerpt of the opening paragraph:
"Throughout this book we have seen that in Einstein's theory of relativity, the notions of space, time, mass, etc., are no longer regarded as representing absolutes, existing in themselves as permanent substances or entities. Rather, the whole of physics is conceived as dealing with the discovery of what is relatively invariant in the ever-changing movements that are to be observed in the world, as well as in the changes of points of view, frames of reference, perspectives, etc. that can be adopted in such observations. [...] [Einstein] was led to make the revolutionary step [...] of ceasing to regard the properties of space, time, mass, etc., as absolutes, instead treating these as invariant features of the relationships of observed sets of objects and events to frames of reference. In different frames of reference the space coordinates, time, mass, energy, etc. to be associated to specified objects and events will be different. Yet there are various sets of transformations (e.g., rotations, space displacements, Lorentz transformations) relating the many aspects of the world, as observed in any one frame to those as observed in another. And in these transformations, certain functions (such as the interval [does he mean space-time interval?] and the rest mass) represent invariant properties, the same for all frames of reference, within the set in question."
Invariant literally means not changing. Most measurements in relativity are relative i.e. they change depending on how you look at them, but the invariant ones don't change no matter how you look at them. Ariel. (talk) 01:46, 4 January 2011 (UTC)[reply]
What Bohm is talking about is the revolution in physics which changed what "invariant" properties were. There was a time when concepts like "distance" and "time" and "mass" were considered invariant, while concepts like "speed" and "density" were considered infinitely variable. Einstein flips everything on its head, showing us that distance and time are relative; but even in Einstein's physics, there are certain things, like "rest mass" and "speed of light" are invariant. Bohm's point is that there are still invariants in physics, its just that what we consider "invarieant" has changed as a result of special relativity and general relativity. --Jayron3203:47, 4 January 2011 (UTC)[reply]
There's lots of food which is dehydrated and then able to rehydrated later. It normally doesn't take anything more than water to do so. The idea that you could dehydrate and the rehydrate a food as complex as a pizza, and get the results obtained in the movie, is pretty much as realistic as the Replicator in Star Trek. That is, it is complete bullshit invented for the movie. Actual food dehydration and rehydration is covered in the overview article Drying (food) and links that follow from there. --Jayron3203:43, 4 January 2011 (UTC)[reply]
The reason is that there are one-way chemical processes which happen during dehydration, and they can't be reversed later on. A raisin soaked in water does not become a grape, for example. Depending on the food, the rehydrated version may be recognizable, perhaps even edible, but rarely is it exactly the same as the original. StuRat (talk) 04:45, 4 January 2011 (UTC)[reply]
I wouldn't worry too much about Black & Decker getting it right in time. If they don't, you can always hop on your hoverboard and pick up a fresh pizza yourself. HiLo48 (talk) 07:42, 4 January 2011 (UTC)[reply]
Phosphenes!!!
I have always enjoyed watching phosphenes. Except my eyes have never been able to focus on them properly. Why?
Also how can I induce them? One time I was lying down to enjoy some mondo-radical phosphene bodaciousness, dude and I was getting some pretty chill phosphenity going on and then SOMEONE decided to turn on the lights and then I turned them off and I couldn't see crap in the sea of eigengrau. What gives, bro?
You can't focus on them because they aren't actually objects. They are basically stimulations of your retina due to pressure fluctuations in the Vitreous humour of the eye. It happens behind the lens of your eye; the lens is the thing which does the focusing, so you're never going to be able to focus on it. The article you link gives some causes of them. --Jayron3203:55, 4 January 2011 (UTC)[reply]
There is white wave technology, which is possibly used on the B-2. It sends out an exactly opposite wave to the radar hitting it, cancelling it out. I'm not sure if we have an article one it. --T H F S W (T·C·E)05:47, 4 January 2011 (UTC)[reply]
Wolfram alpha gives 1e14, [11]. It gives no references so I do not know how mush it should be trusted. Other sources gives figures between 1e13 and 1e14, [12], [13], [14] non seem to be really reliable. --Gr8xoz (talk) 10:34, 4 January 2011 (UTC)[reply]
This is obviously a pretty difficult question to answer, but considering that the 1013 claim is referenced to a review that is more than 30 years old, I'd be inclined to say that that article is wrong. The question has been asked here before e.g. here and here and the consensus both times was that it was somewhere between 1013 versus 1014This press release by the Nobel Prize Committee (I hope they know what they're talking about) says that there are approximately 109 cells per gram of tissue, so for someone skinny like me, that would work out as ~7x1013 which is nicely in the range (fat cells are really large and you supposedly don't grow new ones as you get fatter, so this rule won't hold if you are overweight). This based on a project at MIT says there are ~6x1013 Looking at other less reliable websites from a google of "number of cells in a human body" it looks as if the general consensus is that 1013 is definitely too low, and the lower limit is 5x1013. SmartSE (talk) 10:20, 4 January 2011 (UTC)[reply]
So, why do we say that without an atmosphere, all objects would fall at exactly the same speed towards the Earth regardless of their weight? (i.e., why do we only take into account the "Earth mass" and not "the two masses"?). Newton's law seems to imply that a hammer, being more massive than a feather, will increase ever so slightly the "product of the two masses" and so fall a tiny bit faster.
The force of attraction on the hammer is proportional to the mass of the hammer, but the acceleration of the hammer when allowed to fall in a vacuum is inversely proportional to its mass (Newton's 2nd Law) so the mass of the hammer cancels and the result is that a hammer, and a feather, and anything else in a vacuum at the Earth's surface, will accelerate at the same rate, namely about 9.8 m.s-2. If the hammer is not falling in a vacuum there will be resistance caused by movement relative to the air and this resistance will slow the rate of acceleration. However, the air resistance will be a much smaller proportion of the weight of the hammer than the air resistance on a feather so the hammer will accelerate in air more rapidly than the feather. Dolphin(t)07:28, 4 January 2011 (UTC)[reply]
You are not wrong, basically while the earth moves the hammer toward it, the hammer causes the earth to move toward the hammer. But the difference is so small, i.e. the earth moves so little, it's unmeasurable, so it's ignored. Also if you do actually drop a feather and a hammer at the same time, they will both cause the earth to move, so they will both hit at the same time. What I mean is that the hammer does not fall faster because it's heavier, rather the hammer causes the earth to move, which makes the distance slightly shorter. Ariel. (talk) 07:29, 4 January 2011 (UTC)[reply]
You are wrong in using the phrase "ever so slightly". We do take into account the two masses. The force of gravity on the hammer is thousands of times the force of gravity on the feather, but then, so is its mass (in the same proportion), so the acceleration is the same. (as explained by Dolphin. I'm still thinking about Ariel's moving earth - what happens if the "earth" is just twice the mass of the "hammer"? Dbfirs08:28, 4 January 2011 (UTC)[reply]
Db, when you say that "ever so slightly" is wrong, you are missing Ariel's point.
Let's do this algebraically. Say the earth has mass M, the hammer mass H, and the feather mass F. Then the hammer feels a force GMH/r², and by Newton's Second Law it accelerates at (GMH/r²)/H, which is GM/r². Similarly the feather accelerates at (GMF/r²)/F, which is again GM/r². They both accelerate at the same rate (if there is no air friction).
But the Earth also feels a force of GMH/r² for the hammer and GMF/r² for the feather. Therefore it will accelerate toward the hammer at (GMH/r²)/M, which is GH/r², and toward the feather at (GMF/r²)/M, which is GF/r². Since M is hugely greater than H or F, these numbers are ever so tiny in comparison with the hammer or the feather's acceleration of GM/r². But they are not quite zero. As Ariel says, the hammer (dropped on its own) will hit the Earth ever so slightly sooner than the feather (dropped on its own), because the Earth will come up to meet it ever so slightly faster. For all practical purposes this can be ignored, so we usually do ignore it. By the way, r is also changing ever so slightly while the object is falling; this too can be ignored for practical purposes, and it doesn't affect the conclusion in any case. --Anonymous, 11:12 UTC, January 4, 2010.
Oh, good. I was worried there for a moment that all objects everywhere might be attracted together at the rate of a falling hammer, which would have got uncomfortable quickly. 81.131.22.240 (talk) 11:20, 4 January 2011 (UTC)[reply]
Yes, there is a tiny, almost insignificant difference. Not because the hammer accelerates faster (it doesn't), but because the Earth accelerates faster. — Sam 63.138.152.135 (talk) 14:34, 4 January 2011 (UTC)[reply]
The Earth falls as quickly toward a pound of hammer as a pound of feathers. And vice versa. A pound of feathers is bigger, and could experience more tidal force in free fall, but overall a spherical object of any size, whether made up of hammer or feathers, acts like all its mass is concentrated in its center in a uniform gravitational field. Now of course the Earth's gravitational field is not uniform, and I think this leads to a slight difference on this basis. For example, a pound of feathers of the spotted astrasphinx consumes a volume a light year in diameter; when such a ball just grazes the Earth's upper atmosphere, a small region of it undergoes a noticeable gravitational attraction - I think this will contribute more force than is experienced by a pound of hammer half a light year from the Earth, though I'm not sure. Wnt (talk) 14:41, 4 January 2011 (UTC)[reply]
Fearsome though the astrasphinx is, the OP isn't asking about a pound of feathers, but about two objects of different mass ("a hammer, being more massive than a feather...") 213.122.31.229 (talk) 16:07, 4 January 2011 (UTC)[reply]
The usual conditions for the thought experiment on this are to have the hammer and feather dropped simultaneously side by side in vacuum. Under those circumstances both hammer and feather will hit at the same time, even after taking account of the immeasurably small movement of the earth due to the combined mass of hammer and feather. SpinningSpark14:55, 4 January 2011 (UTC)[reply]
The thought experiment implicitly takes place in the reference frame that keeps Earth stationary. In any other non-privileged (equally valid) reference frame, Earth and the hammer accelerate towards each other at 9.8... m/s2. But for the purposes of practicality, we consider that specially constructed reference frame that is centered at Earth. In this frame, all objects accelerate toward Earth; and because dependence of the gravitational force on the other object's mass cancels out the "F = ma" in the object's acceleration, (in other words, the gravitational mass and the inertial mass of the test-particle (hammer or feather) are always exactly identical). Acceleration is equal to F/m, which is proportional to mgravitational/minertial, which is exactly one; therefore gravitational acceleration is a constant for all test particles (hammers, feathers, the Sun, and so on), when viewed from the stationary, inertial reference frame of Earth. This exact equality between inertial mass and gravitational mass is one of the interesting observations that led to Einstein's understanding of gravitation in nonprivileged reference frames. Nimur (talk) 15:08, 4 January 2011 (UTC)[reply]
The question isn't about chain-type links, it's about links in a linkage. So far as I know, springs are modeled as forces rather than links. In any case, they wouldn't be a ridid link, as that's sort of the opposite of a spring. Andrew Jameson (talk) 16:57, 4 January 2011 (UTC)[reply]
there are three kinds of links ..rigid.fluid and flexible link(belt,rope).it seems springs can also transfer motion in one direction only.. can it be a flexible link —Preceding unsigned comment added by 59.93.130.68 (talk) 17:27, 4 January 2011 (UTC)[reply]
Science provides us with continually improving explanations of how stuff works. It allows the human race to better adapt to its environment, which is one of humanity's strongest traits. HiLo48 (talk) 17:43, 4 January 2011 (UTC)[reply]
Agreed. It prevents us from moving backwards, into believing incorrect things, as happened when much of the science of the Greeks and Romans was lost in the Middle Ages, due to rise of organized religion and suppression of science. StuRat (talk) 18:20, 4 January 2011 (UTC)[reply]
Breathing underwater
Why can't our lungs extract oxygen from water like gills can? If the lungs were filled with water, naturally the body would die from lack of oxygen, but would they be able to extract any oxygen into the blood at all? How close are the structures to something that could function as gills -- given several million years in a water-filled Earth, could we evolve the ability to breathe underwater with just a few dozen mutations? — Sam 67.186.134.236 (talk) 13:13, 4 January 2011 (UTC)[reply]
I looked at Artificial_gills_(human), which links to this: Why don't people have gills?. The mutation to breathing water would require us to either develop very large gills, or else to need less oxygen somehow. This doesn't really answer the main thrust of your question, the matter of whether lungs would function as gills if we had the lower oxygen requirements of a fish. 213.122.31.229 (talk) 13:51, 4 January 2011 (UTC)[reply]
Bit more information at Drowning, where it says that fresh water in the lungs is absorbed into the blood by osmosis and leads to bursting of the red blood cells. So if we're going to become fish, looks like the best option is to be salt water fish. 213.122.31.229 (talk) 14:21, 4 January 2011 (UTC)[reply]
What about Amniotic fluid? I've always wondered how it is that a fully-formed fetus can 'breathe' liquid one minute, be born, then breathe air as an infant the very next minute. -- Ϫ16:01, 4 January 2011 (UTC)[reply]
The fetus does not oxygenate blood via amniotic fluid. Oxygen is transferred from the mother's blood to the fetus via the placenta. One thing that makes this possible is that fetal hemoglobin holds on to oxygen more strongly than adult hemoglobin and can therefore extract the oxygen that diffuses into the mother's bloodstream. The rather instantaneous change from being dependent on the maternal circulation to requiring lungs for oxygenation is indeed spectacular, and it involves closure of the ductus arteriosus shortly after birth. During fetal development, breathing of amniotic fluid plays an important role in lung maturation; see pulmonary hypoplasia for a discussion of how lack of amniotic fluid can cause problems during development. The infant rapidly inflates the lungs with the first breath, and the remaining amniotic fluid is either reabsorbed or coughed out. --- Medical geneticist (talk) 17:16, 4 January 2011 (UTC)[reply]
Some concepts:
1) There's more oxygen in air than in water. Thus, lungs can be less efficient than gills at extracting oxygen.
2) One difference is that gills often have a continuous flow direction, while we reverse the flow direction of air as we breathe in and out. This leads to mixing of good air and bad, and thus reduces efficiency. StuRat (talk) 18:17, 4 January 2011 (UTC)[reply]
There have been reports of thousands of birds falling dead from the sky simultaneous with thousands of fish dying in Arkansas. The state wildlife commission has given glib and unconvincing explanations such as "some disease killed the fish" and "the birds were scared to death by fireworks" while some necropsies find "massive physical trauma" in the birds. When people have attempted to kill or drive away nuisance collections of birds by shotgun blasts or noise from loudspeakers, the birds just shrug it off. Other explanations are the thousands of birds "were killed by hailstones" (which somehow did not pile up on the ground as did the dead birds) or "they were struck by lightning" (which somehow simultaneously covered a 1 mile diameter). Mightn't it justify its own article, beside the brief mention in the article for the Red-winged Blackbird and for Beebe, Arkansas, since other species also died, and a similar dieoff occurred shortly afterward 300 miles away in Louisiana? From 1968 to 1975 the Smithsonian hosted the Center for Short-Lived Phenomena. Did their records include similar mass trauma killing of thousands of birds over a 1 mile area? Is there a listing of historic mass bird dieoffs? I expect domestic turkeys to run around in a panic and die when there is a disturbance, since they are not bred to have any common sense, but wild birds generally have not seemed so prone to fly around in a panic and die when there is noise, by crashing into each other, trees, houses, or the ground as some have suggested.. They have had millions of years of natural selection operating in a world where there is lightning. Edison (talk) 17:30, 4 January 2011 (UTC)[reply]
You seem to have citations from a couple of independent sources. A new article would seem valid, but do steer away from conspiracy theories. New Year celebrations and holidays can delay good responses from authorities. Just present what those media reports have told us actually happened. And be prepared to update it as further news comes to hand. HiLo48 (talk) 17:41, 4 January 2011 (UTC)[reply]
The mass dieoff in Arkansas may have motivated the media to publicize a later smaller dieoff in Louisiana. The species included other than redwing blackbirds, although they seem to be most numerous in the two cases this month. An article collecting unrelated dieoffs might be WP:SYNTHESIS or WP:ORIGINALRESEARCH, but not if CNN and other news media link the incidents in one article. Conspiracy theories? Christian Science Monitor specifically discussed these dieoffs in relation to such theories on January 3. Edison (talk) 18:01, 4 January 2011 (UTC)[reply]
The hailstone theory sounds reasonable, and the stones would then melt in short order, if temperatures were high enough. If this was in an isolated area, then people would likely discover the birds only after the stones were gone, especially if it happened when everyone was asleep. Volcanic gases could also kill off a flock of birds, but this would be obvious. As for fish, in addition to disease, there can be water quality problems, such as incorrect pH or a lack of oxygen, which can cause massive fish kills. StuRat (talk) 18:07, 4 January 2011 (UTC)[reply]
FWIW, there was a news report on this on the UK's BBC Radio 4 within the last 90 minutes - I think on the 17:30-18:00 PM programme - in which the senior veterinary official for Arkansas (can't remember his exact title) was interviewed. His general thesis was that fireworks had startled the roosting redwing blackbirds, which being unable to see at night then blundered into buildings and structures, injuring themselves. Other witnesses reported hearing loud bangs "like cannon fire" after dark and then seeing the birds flying into obstructions. 87.81.230.195 (talk) 18:59, 4 January 2011 (UTC)[reply]
Fireworks is rather unconvincing since the tens of thousands of other fireworks that are shot off each January 1 and July 4 don't kill thousands of birds. Googlemeister (talk) 19:34, 4 January 2011 (UTC)[reply]
OR, but it's worth noting that at this season of the year, red-winged blackbirds tend to flock in huge numbers. My guess is that a flock of them got caught in a strong updraft inside a thunderstorm, which could easily have carried them to an altitude of 20,000 feet or higher, where they would have died of suffocation and cold, and the bodies would have been scattered over a pretty broad area. If this is what happened, then I think there should be signs of it that are visible at autopsy. Looie496 (talk) 20:31, 4 January 2011 (UTC)[reply]
This isn't the first news item I've seen about a flock of birds falling down dead - here's one about 76 dead starlings in Somerset: [16]. Here's one about several hundred mysteriously inebriated parrots: [17]. It's all very Fortean. This one [18] is about 200 dead seagulls in Perth, and mentions a previous incident of 5000 dead birds which was established to be lead poisoning. This story in Pravda [19] from four years ago says that "Doctor Scientist Oleg Kiselyov" (presumably not thisOleg Kiselyov) estimates 2 million birds fall dead from the sky every month, and for some reason he blames them all on bird flu. 213.122.29.106 (talk) 20:38, 4 January 2011 (UTC)[reply]
The problem is, multiple bird species were affected. There's the red-winged blackbirds, but also starlings and grackles. I agree with the IP above me that this seems very Fortean indeed, but I would see what the autopsies say to get a clue on what on earth happened. Crimsonraptor | (Contact me)Dumpster dive if you must20:53, 4 January 2011 (UTC)[reply]
Because it takes a lot of energy to accelerate the incoming particles to that speed. When they collide, all of that energy is released and becomes various other stuff, and the scientific point of the LHC is to study what the "various other stuff" is. Somewhat simplified, the point is not just to "smash things together", but to concentrate a lot of energy in a small space and see what it does. That's where speed / kinetic energy comes in -- small particles at high speed is the only practical way to deliver a lot of energy to a sufficiently small volume in a somewhat controlled way. –Henning Makholm (talk) 19:30, 4 January 2011 (UTC)[reply]
benzene
why does benzene cause cancer but xylene dosent after all it dimethylbenzene
