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.
"The concept that light appears to travel faster than the speed of light to an outside observer is known as super-luminous motion....If you have a charged particle moving close to the speed of light at angle 1/gamma (where gamma is the Lorentz factor) with respect the the observer. the particle can appear to be moving faster than the speed of light in the reference frame of the observer. However, the particle isn't actually moving faster than the speed of light. The speed of light is an Absolute. This effect is also known as relativistic beaming and is common in many Active Galactic Nuclei galaxies." [1]Imagine Reason (talk) 01:37, 29 July 2009 (UTC)[reply]
Well Relativistic beaming is real - our article is pretty clear and although it only has one reference, it's a good one. However, neither our article, nor it's reference talks about things appearing to move faster than the speed of light. Weird. SteveBaker (talk) 02:29, 29 July 2009 (UTC)[reply]
That comment is super misleading. There is no reason to believe that the speed of light is not absolute, and every reason to believe it is. Sure it is always a possibility that our physics is wrong, but this question is asking a specific question about our current understanding of physics. It is not asking for wild ass speculation and ungrounded bullshitting. The question also has nothing to do with tachyons. APL (talk) 04:13, 29 July 2009 (UTC)[reply]
Indeed - there is a hypothetical space craft called "the starship enterprise" which travels at superluminal speeds too...and it's just about as real as tachyons. Just because we give something like that a name - doesn't bestow any additional legitimacy upon the hypothesis! SteveBaker (talk) 22:25, 29 July 2009 (UTC)[reply]
No, no particle can "appear" to travel faster than light. It's a cornerstone in relativity that all observers can agree on the laws of nature independent of how fast they'r travelling relative to each other. No observer should therefore observe a violation of the speed limit. Here's how I think it's meant to be interpreted:
Imagine that you'r shining a flashlight on a faraway wall. You move your flashlight a little and the point of light on the wall zips sideways. If the wall was further away, the point of light would move faster along the wall. Eventually, if the wall was far enough away, the point of light would move faster than the speed of light. However, no photons in the ray of light exceed the speed limit and it's impossible to transfer information at superluminal speed using the blob of light on the wall, as noone at the wall can affect its path or any other property. EverGreg (talk) 11:05, 29 July 2009 (UTC)[reply]
yes. I'm mentioning the light-ray because I'm guessing that's the effect in the relativistic beaming, though from what BenRG is saying, I'm not so sure anymore. :-) EverGreg (talk) 17:01, 29 July 2009 (UTC)[reply]
See also Faster-than-light#FTL phenomena. There are all sorts of cases where something can be made to exceed the speed of light relative to something else. The deal is, no information can travel at greater than the speed of light, so such actions are not useful. --Jayron3211:15, 29 July 2009 (UTC)[reply]
I think that quote is referring to the following fact: suppose you're at (0,0) and an object at (D,0) is moving with velocity v = (vx, vy), so after a time dt it's at (D + vx dt, vy dt). The light from (D,0) will reach you after a time of D/c and the light from (D + vx dt, vy dt) will reach you after a time of, to first order, dt + (D + vx dt) / c = D/c + (1 + vx/c) dt. The object's angular displacement over that time, meanwhile, is Δθ ≈ (vy/D) dt. If you (wrongly!) approximate the object's tangential velocity as distance times angular displacement divided by time then you get D [(vy/D) dt] / [(1 + vx/c) dt] = vy / (1 + vx/c), which is off by a factor of 1 / (1 + vx/c) and can exceed c. That's not surprising since the calculation is wrong (and would be wrong even in a Newtonian universe), but for some reason astronomers think it's interesting and call it "apparent transverse velocity" or some such. This doesn't agree with the paragraph's claim that the critical angle is 1/gamma, so it may be referring to a more sophisticated wrong calculation that gets a more sophisticated wrong answer. This "effect" is discussed briefly at Faster-than-light#Astronomical observations, which cites a paper that unfortunately doesn't seem to be available online. -- BenRG (talk) 16:08, 29 July 2009 (UTC)[reply]
Hypothetical math! ~~ Volume of water required for "the Great Flood" in Genesis?
Genesis 7:19 ~ 21 says that even the tallest mountains in the world were underwater. So, assuming that we need enough water to submerge Mt. Everest, just how much water do we need?
Mean radius of the Earth is 6371.0 km and elevation of Mount Everest is 8.848 Km.
Approximate volume of water required to submerge the Mount Everest is = volume of sphere of elevation - volume of mean radius = 4/3*(6371+8.848)^3 - 4/3*PI(6371)^3 = 4521140066 km3
From this value, subtract volume of all mountains and land above mean radius. I guess 5 % of it. That gives us 4,295,083,063 km3
There is approximately 1,360,000,000 km3 water on earth.
Apparently there is an entertaining book by someone called Bernard Ramm who tried to do all the flood maths and stuff on Polar bears getting back to the North Pole. James Barr reviews it in his book "Fundamentalism" but the review is short: "much good fun can be had reading Bernard Ramm". --BozMotalk08:48, 29 July 2009 (UTC)[reply]
We don't know how tall the moutnains were at that time, that's the problem. Mount Sinai, as noted by 76., may have been as tall as any mountain was anywhere in the world. there could have been violent movements of the earth as well during that time. (And, I thought I read somewhere where Mt. Everest was getting higher., as the one continental shelf was pushing against another.) Some Christians believe that Pangea existed before the Flood.Somebody or his brother (talk) 13:52, 29 July 2009 (UTC)[reply]
Come on folks, Mount Ararat, which is mentioned in the flood story as the first land to emerge, is way higher than Mount Sinai. (Ararat is over 5000 meters, Sinai less than 2300.) Looie496 (talk) 16:19, 29 July 2009 (UTC)[reply]
If we introduce the extreme beliefs of some Christians that the continents have moved around dramatically around in the time humans have been on Earth, and that the heights of mountains changed dramatically in that span, then the volume calculation might as well set pi equal to three, since that is the value given by Kings 7:23, where a round font was said to be ten cubits across and thirty cubits around. Edison (talk) 18:31, 29 July 2009 (UTC)[reply]
You've touched on a small hobby-horse (hobby-pony?) of mine, Edison. If the figures of ten and thirty are considered to be not precise, but rounded to the nearest whole number, they're not incompatible with the correct value of pi. 87.81.230.195 (talk) 03:01, 30 July 2009 (UTC)[reply]
Clearly God manipulated the geological record to test our faith in the Bible and decide who should be saved! (More faith=more gullible=less worthy of immortality.) --99.237.234.104 (talk) 02:37, 30 July 2009 (UTC)[reply]
Oblation
While re-reading Kim Stanley Robinson's Red Mars, I encountered the unfamiliar term "oblation:" The sun was...small and round even though it was near setting; there wasn't enough atmosphere for oblation to enlarge and flatten it. I know what he means, but in trying to read about the actual science behind it, I can only find a religious meaning with Google, including our own oblation article. Does this phenomenon have another name, and how do I read more? - Draeco (talk) 04:59, 29 July 2009 (UTC)[reply]
From the context I would guess that what he meant is that the atmospheric refraction was insufficient to make the Sun look oblate (meaning here - looking like an ellipse rather than a circle) close to the horizon because the atmosphere was too thin to perceptibly refract the sunlight. --Dr Dima (talk) 05:39, 29 July 2009 (UTC)[reply]
We have nice examples of the atmospheric refraction distorting the apparent shape of the sun disk near the horizon in the green flash article. At any rate, the proper name of the phenomenon is "atmospheric refraction" :) . By the way, I wonder if KSR was really right about Mars atmosphere being too thin to do that. It's not just density, it's the density gradient that counts. And, Mars atmosphere being colder than ours, the gradient may be not too low... --Dr Dima (talk) 05:49, 29 July 2009 (UTC)[reply]
this is an image of Martian sunset taken by Mars Pathfinder. The colors are real. The color variation is due both to the light scattering on the dust and to the atmospheric refraction. Note that the Sun disk looks distorted (elongated vertically). So yes, Martian atmosphere can distort the apparent shape of the Sun near the horizon. --Dr Dima (talk) 16:18, 29 July 2009 (UTC)[reply]
On the other hand, the first part of the circumstance ("enough atmosphere for oblation to enlarge... it") smacks of the moon illusion. Additionally, our article there notes that flattening occurs in the vertical, not the horizontal. As such, I expect the vertical elongation in Dr Dima's image is a lens artifact or a squashed image, not a true representation. — Lomn18:18, 29 July 2009 (UTC)[reply]
Note: the vertical distortion of the image may also be a function of the three exposures used to create the color image. Any motion of the sun between exposures would cause apparent vertical elongation when combined. — Lomn18:29, 29 July 2009 (UTC)[reply]
Yes, Lomn, you may certainly be right about the vertical elongation being the artifact of the several exposures used to acquire the color image. Indeed, according to jpl.nasa.gov, the imager on Mars Pathfinder used a set of filters on both of its optical channels. That means that it required several consecutive exposures to take real-color images, pausing between exposures to rotate the filter wheels. However, I do not think that the atmospheric refraction always causes a vertical flattening; not even on Earth. Indeed, there is a well known "Etruscan vase" atmospheric effect where the apparent Moon disk is dramatically distorted and elongated vertically. So, lest we -God forbid!- dare bring the Original Research into this Temple of Wiki, we should probably leave the verdict on the question of whether the Martian atmospheric refraction is strong enough as "inconclusive". --Dr Dima (talk) 19:49, 29 July 2009 (UTC)[reply]
Lomn, how could elongation of the image due to movement between colour exposures occur without causing coloured edges on the sun? Cuddlyable3 (talk) 20:13, 30 July 2009 (UTC)[reply]
Conservation of energy
Let's say we have a collision between two atoms, where energy cannot dissapear in the form of internal kinetic energy or whatnot(let's pretend that, in this particular case, a photon isn't released). What theoretical argument justifies kinetic energy being conserved(in other words, how do we know that the work done on one atom = the negative work done on the other)?
If no energy is dissipated, the collision of fully elastic, i.e. in a frame of reference moving with the barycenter, both will have the same speed after the collision (but different directions). "Negative work" does not make sense here - "work" and energy are undirected scalars. Hence the kinetic energy before and after the collision will also be the same. --Stephan Schulz (talk) 08:25, 29 July 2009 (UTC)[reply]
Stephan, the question did not specify that you had to work on the reference frame of the center of mass. Negative work makes perfect sense on a different reference frame. Dauto (talk) 12:18, 29 July 2009 (UTC)[reply]
Conservation of energy is shown to hold empirically. Any physical theory is based on a set of axioms, which have to be accepted as true (hopefully because they match experimental evidence), and the rest of the theory is derived from there. Energy conservation I think is usually taken to be an axiom, but there are equivalent ones. Conservation_of_energy#Noether.27s_theorem mentions that time translational invariance of physics implies conservation of energy. Rckrone (talk) 15:45, 29 July 2009 (UTC)[reply]
To say that the reason the total kinetic energy remains constant is because energy is conserved, followed by saying that energy is conserved because it's an elastic collision, is circular logic. My question is, why is energy conserved in such a situation? And I would like to hear an explanation other than Noether's theorem, because conservation of energy was well understood before her time. I doubt a derivation using Newton's laws would be hard, and I have a rough sketch of what it would look like in my head (the atoms slow down because of the electric force bewteen them, hence energy is stored as potential energy, which should the push the atoms away with the same work), but the details are lacking.
And I wouldn't consider conservation of energy to be an axiom (at least not in classical theory), but rather Newton's laws to be the 'axioms', because from them, conservation of momentum and the like are able to be explained.
Let me turn your question around (and maybe let you clarify what you're really asking): where do you propose happens if energy is not conserved via work/change-in-velocity during the collision? Either the energy goes "somewhere else" (not into kinetic energy in the particles--conserved, but in some other variable in the system) or it disappears entirely (not conserved at all in the whole closed system). DMacks (talk) 19:30, 29 July 2009 (UTC)[reply]
Are you sure? The interaction bewteen two bodies is mediated by the Coloumb force, and apparently (I remember reading this somewhere) because the Coloumb force can be represented as a gradient of a potential, energy is conserved.
Newton's laws alone only give you conservation of momentum. Coulomb's law together with Newton's laws does imply that energy is conserved when the only force is the electrostatic force. In other words, the electrostatic force as defined by Coulomb's law is a conservative force. (That article also goes into how you would go about proving whether a given force is conservative.) If you had a full description of all the fundamental forces, you could prove from that the conservation of energy generally. However, I don't think there's an accurate self-consistent theory like that right now, since quantum gravity is still a problem. Rckrone (talk) 03:40, 30 July 2009 (UTC)[reply]
The article says that a conservative force is one where the work done by it on an object does not depend on the path taken, only the change in position of the object...what I don't see is how this means that, in a hypothetical collision between two atoms, kinetic energy should be conserved.
You're right, you need a few more steps to show that things work out when both objects are accelerating. If you want to assume that only the electrostatic force is in play and that the objects can be approximated by point charges, then the Two-body problem article has what you need. Specifically, the displacement r between the particles follows the equation , and the total kinetic energy in the center of mass frame can be shown to be where μ is the reduced mass, so it behaves like the case of a single particle in a stationary electric field. Rckrone (talk) 17:28, 30 July 2009 (UTC)[reply]
Trees showing the undersides of their leaves before a summer storm
When I was a lil guy, I always heard that you could tell a summer storm was coming if the trees (especially silver maples and tuliptrees) showed the undersides of their leaves. I was thinking about this yesterday when driving home from a job:
at one point on the highway, I noted that many of the trees had upturned leaves
a few miles up the road, I went through part of a storm
past the storm, the leaves were turned up again, then after a few more miles they weren't
...so there's at least some anectdotal evidence from yesterday's commute :-).
I'm wondering though if this really does work, and if so, why? Is it something to do with an updraft? Buildup of electrical charge before a storm? --SB_Johnny | talk09:32, 29 July 2009 (UTC)[reply]
We have an article on the weather stick. The web page that article uses as a reference says that the branch is responding to relative humidity.[2] Other web pages claim that it’s barometric pressure.[3] So far, I haven’t found a really reliable source that would give a definitive answer. Red Act (talk) 12:29, 29 July 2009 (UTC)[reply]
this link (can only access Google cached version for some reason) goes to a discussion among some university professors who conjecture that it has to do with a shift in winds. this link (warning .pdf!) concurs, saying that the leaves grow according to prevailing winds, and the approach of a storm, being a non-prevailing wind, will turn them over. Some jerk on the Internet (talk) 12:45, 29 July 2009 (UTC)[reply]
The experiment reported by this web site referenced by the weather stick article does make it look like it’s the relative humidity that’s affecting the stick. However, the experiment doesn’t control for other possible changes, such as barometric pressure, so it’s not quite conclusive. Red Act (talk) 12:54, 29 July 2009 (UTC)[reply]
So I'm getting from this that the "folklore" is true (leaves turned up do indeed mean rain coming), but it's not sure how or why it happens? Is there a name for the effect? Might be nice to start an article on it if there is.
Erm... has anyone noticed that the answers given so far have nothing to do with trees? A weather stick is a dead branch, that is expected to expand/contract according to humidity. But a living tree is regulating the humidity in its branches, so that it is nearly independent from short-time fluctuations (like a storm). Did you notice that many light, loose things, e.g. tends, will preferentially show their underside before and in a storm? This is mainly an effect of wind. I would think that leaves, being very lightweight, react to the increased wind heralding a storm. Come on, everyone knows that a storm is coming when the wind starts to blow stronger and in gusts. I can't see anything special in the observation that wind turns leaves. Or did you really see the leaves standig still, in an upright position? Or were they "dancing in the wind"? --TheMaster17 (talk) 08:43, 31 July 2009 (UTC)[reply]
There’s more going on than just a branch expanding and contracting according to humidity. If that were the case, then a straight-ish branch isolated from the wind wouldn’t be expected to change its shape with variations in atmospheric conditions, due to symmetry. There’s also something more going on than just leaves blowing in the wind. I believe what’s going on is an example of hydronasty, which we unfortunately don’t have an article on, although we do have an article on nastic movement in general. My guess is that in some way the bottoms of the branches are more hydrophilic, and the tops of the branches are more hydrophobic, which causes the unequal swelling to bend the branches. I think the survival advantage of evolving hydronasty in this case is a matter of taking on a branch configuration that maximizes water making it down to the roots when it’s raining, and taking on a branch configuration that maximizes exposure of the leaves or needles to the sun when it’s not raining. Unfortunately, the first 50 Google hits on “hydronasty” don’t turn up a good web page about it, instead just turning up one-sentence definitions of the word, or listing it in a list of nastic movements. Red Act (talk) 10:09, 31 July 2009 (UTC)[reply]
It was clear to me that just contraction wouldn't bend the branch, but as branches are not symmetric (they work against gravity, which is really asymmetric), this is easily explained by the distribution of different types of fibres in the dead wood. But my point was: Is there really repositioning of leaves before a storm? Is there a reference available for this behaviour, which did account for wind and indeed did measure the position of the leaves? If it is hydronasty as suggested because of air humidity, how can the tree differentiate between an upcoming thunderstorm and a "normal" humid day? And I must say that I have never observed the phenomenon described in the OP's post, and I have been camping all my life, occasionally watching trees in thunderstorms. I have never read about this in any botany book (and I have studied biology at a university, with botany as one of my major subject). And what do you mean by "maximize the water making it to the roots"? All water comes to the ground (for examples as drops that travel over the leaves, finally dropping). Only a small amount of water sticks to the leaves as they have a hydrophobic surface of waxes, and as rain does seldom fall vertically in a storm, I cannot even see how a certain position would minimise the amount of droplets that remain on the leaves (which would probably anyway be blown of by the wind in a storm, which shakes the drops of the leaves). And as a remark, most trees don't depend on the water that falls just near their stem, they have a big system of roots, either collecting deep underground or in a wide area (or both). So in summary, I'm sceptical to the existence of the described movement, and even if it exists in certain plants that I'm unfamiliar with, I'm rejecting the explanations so far on scientific grounds. I think this question is really in a need of references. --TheMaster17 (talk) 13:26, 31 July 2009 (UTC)[reply]
It’s not surprising if you haven’t observed this behavior, since it doesn't occur with most species of trees, and since it’s not a motion that occurs fast enough that you’d notice it if you were to sit there and watch a tree for a couple minutes. As to the exact nature of how this behavior works, or what the survival advantages might be, or even if it’s even a survival advantage vs. just a side effect of other effects, I don’t claim to actually know the answers, which is why I identified my hypotheses with words like “my guess is” and “I think”. But some small branches of some kinds of trees do bend considerably within a short period of time due to atmospheric conditions even when isolated from the wind, as you can see in this video.[4] Or is what you are denying that this branch would exhibit this behavior if it was still attached to the tree it came from? Red Act (talk) 15:34, 31 July 2009 (UTC)[reply]
Yes, this is exactly what I am denying. The hydration state of healthy plant tissue is (nearly) independent from short time fluctuations in the environment, as I stated before. The plant has evolved countless tricks to regulate this, because it is so important for all kind of processes (the most important ones being photosynthesis and nutrient transport). And I have not watched trees "a couple of minutes", more like hours, before, during and after every imaginable wheather in middle europe. What I know from this is that trees move in the wind, but I have never seen a branch of a living tree changing its shape because of humidity. Let me state my question again: Why don't the leaves always change their position when humidity changes, but only before a storm? What could be different? My answer is: the wind. And: What kind of advantage would repositioning confer? I didn't get your point when you talked about "rain coming to the roots". I have done experiments with plants(not exactly trees) under different conditions (one of those was humidity), and I have not seen a change of shape, just a change in physiologic rates and processes. I'm perfectly sure that dead wood does bend when you change its hydration state, but what about a video of a living tree, under varying conditions? So far this is only guessing, not giving references. And I have looked for references, and couldn't find a single one in my university textbooks. --TheMaster17 (talk) 11:45, 1 August 2009 (UTC)[reply]
While not a paper in an academic journal, nor a scientific study, an article entitled "The Gardner's Weatherman" in the newsletter of the Muskegon County Master Gardner Association, published in cooperation with Michigan State University Extension, discusses the phenomenon:
All the previous plants [list of plants purported to predict weather changes] show a response to increasing
humidity in the atmosphere. As you will recall from
previous discussions, the relative humidity usually rises
before the onset of rainy weather. Since the internal
water pressure of a plant is regulated by the
evaporation rate balanced against the rate of water
uptake from the soil, any change in the evaporation
rate will also affect the internal water pressure. It is
then easy to see that when a plant cannot get rid of
excess water because of high humidity, the tissues will
swell and change their shape, closing flower petals,
and straightening stems. When the humidity falls after
a storm passes, the plant can get rid of the excess
water, and the flowers return to their normal condition.
Silver maple: the silver maple shows its undersides before a rain....
Trees: when the leaves of trees curl during a south wind, it will rain.
Here, the responses are not so easily apparent. The
curling of the tree leaves may be due to increased
tissue water pressure as above, but it may also be due
to a strengthening wind caused by the pressure
gradient of a deepening low pressure system
approaching the area. Silver maple leaves showing
their undersides is definitely due to a wind shift away
from the prevailing wind. The tree gets “used” to the
wind blowing from one direction, and when the wind
shifts ahead of a storm, the leaves will flip onto their
This seems to go into the right direction. I don't know why I didn't find this with my google search, but this at least also states, although not in a reliable text, that it is the wind. I wouldn't count this as real reference, because it seems to be a cite itself, coming from a folklore text. And also its understanding of the influence of humidity is flawed: Just because the rate of evaporation changes in high humidity, doesn't mean that the plant is "helplessly" siting around, waiting for its tissues to swell. Almost all "modern" plants can regulate not only their evaporation rate by regulating the size of their stomata, they also actively regulate the uptake of water and nutrients from their roots (btw: what a poor article for this important topic of botany). --TheMaster17 (talk) 11:57, 1 August 2009 (UTC)[reply]
Chlorhexidine
Chlorhexidine is widely used in medicine and dentistry as several % solution. What is chlorhexidine itself, is it solid or liquid? What is its appearance? Renaldas Kanarskas (talk) 10:50, 29 July 2009 (UTC)[reply]
Our article on Chlorhexidine has many external links to pages at other sites, such as in the infobox. According to this one: [5] from Chemspider, the melting point is 134 Celsius, which would make this a fairly low-melting solid in native state. --Jayron3211:08, 29 July 2009 (UTC)[reply]
Can't find solubility data either, but based on the structure, it looks like it's slightly soluble in water at neutral pH, and fully soluble at acidic pH. FWiW Just looked up the MSDS, it says chlorhexidine is insoluble in cold water (solubility is only 0.08% w/v). 98.234.126.251 (talk) 18:43, 1 August 2009 (UTC)[reply]
Hi all, I have two questions about charging up my cordless drill:
I have an 18V battery for my Black&Decker drill. The drill came with a plug (wall wort and 5-6 mm jack) which, if you you have the battery inserted in the drill and the plug connected to the drill, you can charge the battery. The question is: I may or may not have lost the plug. I have one that has an output of 5.0V and 2.6 A with the right size jack, but am I right in thinking that this can't be the plug, because the transformer would need to supply at least 18V to charge the battery?
Apart from this one plug (which has to go through the drill, making it annoying), why do all my power tool batteries need to be charged with some stupid expensive shoe like this or this? Why can't they just have a jack that lets them plug into the wall? Are they just trying to make me spend more money?
I am not an electronics expert but I would have expected a much more powerful charger, I think that charger would take a long time to charge a battery of even only a few AH. As for the charging stations, the intention is to have 2 batteries, one on charge with the other in the tool for constant usage. 81.144.241.243 (talk) 13:01, 29 July 2009 (UTC)[reply]
See if it's not on this page [7]. If not you'll probably have to do a 2 step process here [8] First enter the model number of your cordless drill in the "need a manual" window (unless you are more organized than most and actually still have that) That will tell you what they call the wall wart/battery charger/power adapter /etc. and if you are lucky also a part no. Enter either the part no. or the description in the search window on top of the page (underneath the DeWalt logo). If that doesn't get you anywhere call their customer service [9] (USA 1-888-678-7278). Good luck. 71.236.26.74 (talk) 14:03, 29 July 2009 (UTC)[reply]
There does not appear to be standardization of voltage and plugs. The wall wart you have with a 5 volt output would not be able to recharge your 18 volt battery. It is a good practice to get a white paint marker, and write on each adapter what device it works with, because eventually they are bound to get separated. The adapters often just have the name of a factory in China on them and not the brand or model of device they are supposed to power or charge. Edison (talk)
High performance batteries and their chargers have specific voltage/current characteristic and charging time. They are designed together as a system and the manufacturer has to accept liability of overheating, explosion, chemical leakage or damage. This means it is to your advantage to have the charger and battery that the supplier guarantees for use together. It is inconceivable that any honourable company could dream of making a profit from your purchase. Cuddlyable3 (talk) 16:13, 29 July 2009 (UTC)[reply]
A "shoe" to hold the drill can be attached to the wall, and it harder to lose than wall warts. Many tools also have removable batteries, so one can be charged while the other is in use. I've even seen a boxed set of power tools that were cheaper because they shared the one battery pack. The "shoe" style connectors may also be stronger in some way than the tiny plugs on wall warts (something to do with resistance in the wires? all I know about electricity is to keep my fingers off it). - KoolerStill (talk) 09:24, 30 July 2009 (UTC)[reply]
Calcium Chloride in Damprid?
Is the calcium chloride in Damprid really just regular ole table salt that I can buy in the grocery store? If so, wouldn't it be cheaper for me to buy a bag of salt instead spending a lot of money buying the refills? --Reticuli88 (talk) 13:18, 29 July 2009 (UTC)[reply]
Sodium Chloride is "just regular ole table salt", more or less, but no that's not Calcium Chloride (which is nastier). On damp removers the reusable ones are Silica based but have lower capacity. There may be cheaper places to buy Calcium Chloride--BozMotalk13:26, 29 July 2009 (UTC)[reply]
This has been puzzling me for long.Consider that you are lighting a gas stove or bunsen burner.When you light it,the gas gets ignited and undergoes combustion and hence it burns.The burning process takes place only outside the outlet.What is the mechanism that prevents the fire from spreading inside along the tube and into the gas cylinder and the final KABOOOOOM ???gdsrinivas 13:35, 29 July 2009 (UTC) —Preceding unsigned comment added by Gd iitm (talk • contribs)
probably because the gas pressure inside the pipe is higher than outside so the flames are blown outwards. also, there is no oxygen in the pipe to support combustion so the gas will extinguish any flame that manages to make it inside. Coolotter88 (talk) 13:38, 29 July 2009 (UTC)[reply]
In a bunsen burner,there is a hole at the bottom for mixing of air and gas.So it is a mixture of air and gas along the entire length of the bunsen burner.Now how do you explain it??gdsrinivas 13:43, 29 July 2009 (UTC) —Preceding unsigned comment added by Gd iitm (talk • contribs)
"Back burning" can occur in a bunsen burner. No flame shows and it smells bad. I think it can be provoked by throttling back the gas supply. It can be corrected by thumping the rubber supply pipe. Cuddlyable3 (talk) 13:48, 29 July 2009 (UTC)[reply]
There are two features here. Even in a tube of perfectly mixed methane and air, the speed at which a flame propagates into the mixture (the Flame speed) is limited (by memory about 5 cm a second I think) so if the flow speed exceeds this the flame will be being blown away not traveling down the tube. The flame only stays put on a bunsen burner because the double burner edge creates a recirculating eddy: try to light a straight tube of premixed air and you will fail. Gas stoves have similar design features. The second feature to stop this inadvertently happening at low nozzle speed is a Flame trap which is made of wound up nit-mesh: the flame cannot penetrate it because the heat loss to the metal fibres quenches the flame. However do not be fooled into thinking the gas emerges completely premixed; close inspection reveals a rich premixed inner flame (blue, the characteristic colour of Carbon Monoxide flames) and a CO rich diffusion flame outside it. Clever chap Bunsen. --BozMotalk13:57, 29 July 2009 (UTC)[reply]
Or an old one! Most Bunsens don't easily do back burning anyway, but they certainly did when run on coal gas, as I remember well, when I started work. Not that we have Bunsen burners in the lab any more (sigh) Ronhjones (Talk)19:14, 30 July 2009 (UTC)[reply]
Thats a nice question.But when I asked one of my friends he said it was one of the important concepts in fluid dynamics.Any info based on this???thanks117.193.144.206 (talk) 16:29, 29 July 2009 (UTC)[reply]
As an add on to the question why does the flame occur only exactly at the top of the bunsen burner opening???Why not it occur a few centimetres above the bunsen tube or a few centimetres inside the tube???117.193.144.206 (talk) 16:36, 29 July 2009 (UTC)[reply]
I am not very good at explaining things. Flames are just reaction fronts which eat into flammable gas mixtures. To ignite the gas coming rapidly out of a pipe end you need an ignition source where the gas comes out (or with very fast turbulent flow ignition further downstream). Otherwise the flame will blow itself out. For a burner this could be a pilot light by the pipe end but if you can induce an eddy by the pipe end (a recirculating piece of flow) then the gas which is already burning keeps the flame going by reintroducing a piece of flame into the flow. This is the purpose of the double skin on a Bunsen. Unfortunately the Wikipedia article on Bunsen burners is not very good apparently because there isn't a very good reliable source on Bunsen's. However I have written a few peer reviewed papers on gas combustion [10][11] and I do have some idea what I am talking about. --BozMotalk19:42, 29 July 2009 (UTC)[reply]
If you understand flow dynamics I should add that a stagnation point is sometimes sufficient but not as stable and that just having a thick tube wall works at some flow rates. However if you get a pair of pliers and squeeze the two walls of a Bunsen together (so that you just have a circular pipe end) the flame will blow itself out. --BozMotalk19:50, 29 July 2009 (UTC)[reply]
A really cool fact I heard which I think is relevant here, if you were in a pure methane atmosphere and had a burner connected to a bottle of oxygen, it would essentially behave the same way as the other way around here on earth. Vespine (talk) 05:03, 30 July 2009 (UTC)[reply]
Assuming the gas is leaving the 'tube' at room temperature, it has to be heated by the existing flame until it reaches 'flash point' or ignition temperature. For propane, that's 920-1020°F. While that's happening, the gas keeps moving. Twang (talk) 06:19, 30 July 2009 (UTC)[reply]
Yes, good way to look at it although technically ignition by gas inside a premixed cloud is not just by heat, but by a combination of heat and a load of free radicals from the ongoing combustion process (the radicals diffuse forward just as the heat does), which makes the temperature needed a little lower. --BozMotalk06:45, 30 July 2009 (UTC)[reply]
Hey guys this question hasnt yet been answered..thought you didnt notice this
"
Thats a nice question.But when I asked one of my friends he said it was one of the important concepts in fluid dynamics.Any info based on this???As an add on to the question why does the flame occur only exactly at the top of the bunsen burner opening???Why not it occur a few centimetres above the bunsen tube or a few centimetres inside the tube???" —Preceding unsigned comment added by 117.193.137.0 (talk) 07:03, 30 July 2009 (UTC)[reply]
I think that the flame don't occur in the tube cause the gas flow blows it out of the tube faster than the flame front travels back into the tube (as BozMo said earlier). As for it not occurring above the tube, that's because the flow pattern recirculates part of the burning gas-air mixture back to the burner opening, so it ignites the rest of the mixture just as it comes out of the tube. FWiW 98.234.126.251 (talk) 07:20, 30 July 2009 (UTC)[reply]
By adjusting the fuel flow and air-holes, one can usually get the flame to partially "detach" from the rim of a bunsen burner, or even entirely "lift off" of it. If you have supplies higher than what the burner is designed to handle (perhaps mis-adjusted regulator or flow valve, or using a pressurized-air or oxygen source on a burner designed for simple air-holes), you can easily cause the flame to "blow out". Googling "bunsen burner" along with any of the other quoted terms I used can get you some fluid-dynamics and other studies related to these phenomena (and conversely, the conditions required for a stable flame). DMacks (talk) 07:27, 30 July 2009 (UTC)[reply]
Sorry I should add a strong warning not to try using pressurized oxygen as a source unless you really know what you are doing, he means a pressurized air source: changing to an oxygen cylinder or other oxygen increases the flame speed considerably and you may get something nasty happening (including conceivably gas detonation). As for the rest, I thought it was all answered. It is all determined by flow. Flow does tend to recirculate but not steadily and not necessarily at the right speed. A stable flame requires a stable re-feeding of burning gas into unburnt gas. The rest is all said...--BozMotalk08:04, 30 July 2009 (UTC)[reply]
Concur on the safety issue. The ideas of flame detachment, burn-back, etc aren't limited to bunsen burners and others that use a simple inspirator/venturi-tube to get the oxidant. The same questions (and flame stability issues) apply to torches with compressed oxidant feeds (and are rated to handle them!). The oxidizer and fuel gases mix and then flow through a few inches of pipe before the tip where the flame is. DMacks (talk) 16:15, 30 July 2009 (UTC)[reply]
Volume to pressure ratio?
How can I know the volume of a gas, knowing the capacity of its container (50 L), the amount of moles (64,48) and the pressure (1,621,200 Pa), but not knowing the temperature? Thank you. --83.56.187.237 (talk) 19:58, 29 July 2009 (UTC)[reply]
You just defined the volume as 50 L. Temperature is the unknown, as you surmised, and can be calculated easily (assuming an ideal gas). — Lomn20:02, 29 July 2009 (UTC)[reply]
Thank you, what a blunder! Therefore, what should I substitute for in the following state equation in order to determine the temperature?
Well I'm not going to do your homework but you need to select the gas constant from the list that uses the same units as your problem. The closest one is in m3 Pa K−1 mol−1. Since you have your volume in L instead of cubic meters, you need to convert that 50L into cubic meters. Then you can use the R constant from the list at the article and it will work (because it's all in consistent units). TastyCakes (talk) 21:16, 29 July 2009 (UTC)[reply]
First I would recommend leaving the units in your equation. That makes everything much easier. It's not important that you choose R so that all the units cancel out right away. You can use unit conversion where necessary to get things into the form you need. So for example if you choose R = 8.314 472 m3 Pa K−1 mol-1, you'll be left with L on one side of the equation and m3 on the other, but we know that m3 = 1000 L. Any of the values for R on that page will work, but some will just require more unit conversions than others. Rckrone (talk) 21:44, 29 July 2009 (UTC)[reply]
Damps in coal mines
Reading Firedamp, I'm curious — using current technology, would it be possible/likely for coal mining companies to collect these gasses in mines and sell them for fuel? Nyttend (talk) 20:10, 29 July 2009 (UTC)[reply]
(EC)The concentration of methane in a coal mine might vary significantly over time and might be too low to run an internal combustion engine, but methane recovered from landfills also varies. Firedamp does not say what the methane concentration is as commonly found. It might be higher in rooms of abandoned mines than in working mines, so some mines might work better than others as possible sources. See Biogas. The solution with gas from landfills is to mix it with sufficient natural gas to properly run an engine such as a modified diesel to generate electricity, if the concentration is too low. The mix can be automatically adjusted as the concentration varies. Edison (talk) 20:40, 29 July 2009 (UTC)[reply]
Flufenamic acid
Our article on flufenamic acid, or fenamic acids in general, lists them as NSAIDs. However, I am not at all sure they inhibit COX. Do they? What flufenamic acid actually does is to block the Calcium-sensitive nonselective cationic current in neurons. What does that have to do with the anti-inflammatory action?! Any input is welcome. Thanks in advance, --Dr Dima (talk) 20:31, 29 July 2009 (UTC)[reply]
Thanks Looie. So it does affect both COX expression and COX activity (as well as cation currents, Ca ion balance, and who knows what else...). It figures. Thanks. --Dr Dima (talk) 23:37, 29 July 2009 (UTC)[reply]
It doesn't look like it. There was a paperback edition published in April of 1978 and a 'mass market' paperback in 1986 - but from what I can see of them in Google books and Amazon - they contain the same text as the 1977 version. Neither of them say anything about being revised - and there is only one author's copyright date. SteveBaker (talk) 21:31, 29 July 2009 (UTC)[reply]
is Eurasian plate (western part) moving north or it is moving south in altitude. Eurasian is a large plate. The east plate is China, Japan, Phillipines, surrounding by Yellow Sea. Part of east half of Eurasian plate is moving southeast. Africa is suppose to collide with Europe, closing all the oceans nearby.--69.228.145.50 (talk) 21:19, 29 July 2009 (UTC)[reply]
For number 2, it looks like good-old, garden-variety fescue. It doesn't look like crabgrass, which is more "stalky" than "leafy". Most other lawn grasses in the southern U.S. are low-creeping grasses which don't grow bushy like this; such as Centipede grass, Bermuda grass, St. Augustine grass. I'm not sure which fescue variety it is, but based on your description and location, unless you are watering the heck out of it, it's probably not tall fescue which goes dormant during the dry summer months, but I would not rule that out. A few good thunderstorms and my tall fescue springs back to life. --Jayron3204:45, 30 July 2009 (UTC)[reply]
You don't show the #1's fruit, but could it be Euonymus americanus aka "Hearts-a-bustin" aka "Strawberry bush" (not a real strawberry)? The give away would be the distinctive fruit, which look better in this google search, and the green stems. --Jayron3204:50, 30 July 2009 (UTC)[reply]
Thanks for taking a shot... The grass has a seed bearing stalk that is about knee to waist high with only two branches like a sling shot. The fruit is completely round with a very sour taste unless you get one that's just dropped or is about to drop. They are kind of like little pumpkins only red and with soft skin and innards (when ripe). The ribs are much more pronounced than a pumpkin's. --Taxa (talk) 06:41, 30 July 2009 (UTC)[reply]
Well, I guess I was wrong about the first one being hearts-a-bustin, but #2 still sounds like a fescue variety, of which there are hundreds. Fescue puts out small seeds on knee-high stalks with 2-3 branches lined with the seeds. I'm still going with fescue there. --Jayron3218:27, 30 July 2009 (UTC)[reply]
Not really, no. There are many nootropic drugs, of various legal status, but none of them will really make a difference if you haven't studied for the exams. --Dr Dima (talk) 23:47, 29 July 2009 (UTC)[reply]
Sure they can. Try caffeine, preferably as coffee, which will also prevent dehydration. —Preceding unsigned comment added by 84.187.91.197 (talk • contribs) 00:12, 30 July 2009
I'm not sure if the OP is expecting to become somehow become more knowledgeable after eating the drug, as in the case where he/she doesn't study. Rather, I think the question is whether there are any drugs which will make your brain more active and sharper for a limited period of time, much like a steroid does to the body. Such a drug would be highly useful in a competitive exam, where speed and accuracy are essentially more important than knowledge. So I'm interested in knowing some answers, too. Rkr1991(Wanna chat?)00:59, 30 July 2009 (UTC)[reply]
If such drugs existed, were legal, and could be sold without a prescription - you can be 100% sure that you'd know it because you'd be bombarded with adverts for them every time you turned on the TV. Instead, the best we get are exceedingly dubious "food supplements" that can claim just about anything without any proof whatsoever because they fall through a convenient loophole in the law. I agree that caffeine is really the only one with any kind of a legitimate track record. It doesn't make you more intelligent though - it just ensures that you're awake. But even then, you have to be quite careful because if you take too much of the stuff, you'll become super-nervous and jittery - and that's just as bad as being half asleep! IN terms of not-legal-without-a-prescription, I've heard that some people take beta blockers because (as our article says) "Beta blockers protect against social anxiety: Improvement of physical symptoms has been demonstrated with beta-blockers such as propranolol; however, these effects are limited to the social anxiety experienced in performance situations. (example: an inexperienced symphony soloist)" - which can leave a person with exam anxiety feeling calm and relaxed. Not more intelligent - but perhaps calm enough to be able to better use the intelligence you already have. But these things can be dangerous - and taking them without a doctor's advice would be pretty amazingly stupid. SteveBaker (talk) 03:57, 30 July 2009 (UTC)[reply]
During the past 5 years or so there has been a large upsurge in the number of "smart drugs" that are sold in schools. The studies I have seen on these drugs say they range from ineffective to ineffective and dangerous. Even caffeine has debated impact on grades. While it would help you stay up the night before to study and help you stay aware during the exam itself, it lacks the ability to give you the mental agility provided by a good nights sleep. Using caffeine to stay up will not help with any exam that takes abstract thought, though could help with other types of exams. Anythingapplied (talk) 04:11, 30 July 2009 (UTC)[reply]
:::Polyjuice and then Steve could sit the exam for you (assuming he is cleverer than you for which no warranty is available under the Wikipedia Disclaimer). --BozMotalk07:42, 30 July 2009 (UTC)[reply]
It might help a little if you've been crammin' all night long or if you've recently been sick with the swine flu (or if you're so high on crack that you can't think properly), but other than that, prob'ly not. It can also have some pretty bad side effects if you take it without a prescription. FWiW 98.234.126.251 (talk) 05:11, 31 July 2009 (UTC)[reply]
A few months back, I stumbled upon a wikipedia article that explained a phenomenon about when people learn new words (i.e. 'perfunctory') and over the course of the next few days, they see that word more often (i.e. in a book, a newspaper article, billboard on the highway.)
What is this effect or phenomenon called?
24.148.59.37 (talk) 02:32, 30 July 2009 (UTC)[reply]
It's not just with new words, either. I remember when I was a kid, when my dad got a new car, suddenly the streets seemed to be full of the same model. It might not even be a cognitive bias, it could just be that since the word is new, it is forefront in your consciousness and seeing it easily reminds you that you just learned it. Over time it falls back to the "just another word" status of everything else in your vocabulary, and seeing it does not trigger the "hey that's that new word" thought. Maelin (Talk | Contribs) 04:39, 30 July 2009 (UTC)[reply]
Attention is affected by the demand characteristics of the situation. Someone in a book (Sorry, don't recall the author) wrote that he had promised to get a helicopter for the arrival of someone at a charitable event. Thereafter, he seemed to see helicopters wherever he went: arriving, departing, or being transported on a truck. The "Ziegarnik Effect " which I only half remember, comes to mind. A waiter remembers an order in detail, but only until it is served at the table. If you are told that Mr. Colvin will be your new boss, then you seem to hear the name Colvin several times a day. It becomes salient in a way it was not previously. There may be a lexical priming effect, which makes any occurrence of a salient word very noticeable. Edison (talk) 02:01, 31 July 2009 (UTC)[reply]
Yeah, looks like an orb-weaver alright. With these guys, no matter what you do they'll still have your porch for themselves :) . Usually, they would spin a new web every day, you know. --Dr Dima (talk) 05:38, 30 July 2009 (UTC)[reply]
Mortality rate relating to refusing blood and/or medical procedure on religious grounds?
I imagine there would be such a statistic but I'm struggling to find it as it's a bit specific. How many people die as a result of refusing to be given blood in a medical emergency for religious reasons? Specifically when doctors believe there was a reasonable chance that blood would have saved them. But less specific any statistic regarding refusal of medical procedure would be helpful. This is not homework or medical advice. Vespine (talk) 04:51, 30 July 2009 (UTC)[reply]
A Wikipedia article cites from the May 22, 1994 issue of the Jehovah's Witness magazine Awake, p. 2: "In former times thousands of youths died for putting God first. They are still doing it, only today the drama is played out in hospitals and courtrooms, with blood transfusions the issue." The statistic you seek is unlikely to be given by a reliable medical source because of the legal, technical and ethical issues of the controversy. Cuddlyable3 (talk) 19:16, 30 July 2009 (UTC)[reply]
This article is helpful. "Although there are no officially published statistics, it is estimated that about 1,000 Jehovah Witnesses die each year through abstaining from blood transfusions". Axl¤[Talk]20:03, 30 July 2009 (UTC)[reply]
Did human muscles mutate to become weaker than those of apes and other animals?
I read recently that human muscles are intrinsically much weaker than those of a chimp, one of whom would have no problem in overpowering a human. The idea was that a mutation during the evolution of humans made such a mutation beneficial, which sounds very odd. But then I thought that perhaps the weaker musculature allows for finer motor control. Apes are great at swinging and leaping around trees, but could they do ballet moves, or juggle balls, or handwrite? And when the technology becomes sophisticated enough, could we opt to reinstitute the more powerful muscle variants, and breed humans who make Arnie look like a wimp. Myles325a (talk) 06:57, 30 July 2009 (UTC)[reply]
I think it is natural that we are much weaker than Apes or Chimps, because our survival is not dependent on our strength. This means we naturally get more and more weaker with time due to cross breeding, as weak people survive almost just as well as strong people, much like how that recent study which told women are getting more beautiful over time... With all the medicines available, I think I can safely say that we humans will get more and more weaker over time. Our parts evolve according to our needs, and hence we have hands which can write rather than swing trees with. I'm pretty sure some research is going on in the area to use technology to make us physically stronger, along with scientific research about genes, but I'll leave that bit for others... Rkr1991(Wanna chat?)07:08, 30 July 2009 (UTC)[reply]
OP Myles back. I don't know about "get more weaker and weaker", but our grammar appears to be getting worser and worser. Also, the last ape I saw swinging trees was King Kong. Myles325a (talk) 23:58, 30 July 2009 (UTC)[reply]
"[E]volutionary biologist Alan Walker, a professor at Penn State University" came up the the same hypothesis about fine muscle control[12], with the difference being more motor neurons in the spinal cord in humans. AlmostReadytoFly (talk) 08:55, 30 July 2009 (UTC)[reply]
A hypothesis that I doubt. Any inhibition would be to stop us hurting our joints I'd have thought. Which is part of the same overall business about why are we being weaker. Anyway he can go ahead and try testing it - that's always good and might turn up something. Dmcq (talk) 10:12, 30 July 2009 (UTC)[reply]
That Persistence hunting is really interesting! I like the theory that guided our running and hairless evolution.
Rkr1991,you have told that animal organs evolve according to their needs.It is not so.It is like this- some individuals of the same species develop some mutations which give them a upper hand in survival and competition among the individuals of the same species.They survive better than the other members and the their traits are passed down to their offsprings.Thus we observe evolution.Infact Lamarck also told "organs evolve according to their needs"(the giraffe neck stuff) but was clearly disproven by weismann's 21 time rat's tail cutting experiment.gdsrinivas 15:45, 30 July 2009 (UTC) —Preceding unsigned comment added by Gd iitm (talk • contribs)
OP Myles back. As a Jew, Weismann need not have not have cut off rat's tails. He need only have noted that 3000 years of circumcising Jewish boys has not led to males being born already cut. Myles325a (talk) 23:58, 30 July 2009 (UTC)[reply]
(At gdsrinivas) How is the cutting of a rat's tail beneficial for it, to be passed on ? And according to your argument, how exactly did humans develop hands which could write rather than those like the apes' or the chimps' ? Surely, a mutation of this sort wouldn't have helped better in their survival, at the time they were living in caves ? Please explain this. Rkr1991(Wanna chat?)07:44, 31 July 2009 (UTC)[reply]
Op myles back here. No, proto humans weren’t writing their memoirs in the caves, but they WERE cutting stone tools and shaping spears and so on. This does need manual dexterity. Cavewomen would have been very impressed with a caveman who had a sure hand and knew how to use it. Myles325a (talk) 06:53, 3 August 2009 (UTC)[reply]
Someone on IRC brought up the subject of the om-nom-nommable packing peanuts (fex the starch ones) last night. Now I wouldn't exactly go nomming these as sustenance, but if you were starving to death would these do anything for you? And are they made of pure starch, or is there some sort of additive/filler? One time I was incredibly hungry/bored and ate about six, I didn't get sick or anything, but is this even remotely a good idea? ZS08:03, 30 July 2009 (UTC)[reply]
I seem to recall a previous discussion here on this, but can't be bothered looking in the archives. Anyway, the result I recall was that they are likely to contain rodenticides, insecticides or repellants to prevent them being omnomnommed by bugs or rodents in transit. As a rule, don't eat stuff that isn't food. --203.202.43.54 (talk) 08:58, 30 July 2009 (UTC)[reply]
According to this manufacturer's site [13] the starch peanuts won't attract bugs or rodents because "the sugars and any food value" has been removed in processing. Since "any food value" is a rather vague term it makes that source a lot less reliable. Researchers found in this study [14] that bacteria don't grow quite as well in it. Most sources say starch packing peanuts dissolve in water. Except in Raleigh they didn't [15]. Your saliva contains Amylase which, if the experiment suggested here [16] works converts the starch in the peanuts to sugar. This patent for making them [17] mentions on page 4, line 23 that manufacturers may use additives in starch packing peanuts. This patent identifies such additives as dyes, processing aids and anti static products [18] Given that ordinary foodstuff also sometimes contains questionable ingredients you may be o.k. to nibble some packaging occasionally. You can't sue the manufacturer if this turns out to be overly optimistic, though. (Definitely don't eat any pink ones. Those are the ones with antistatic additives.) Gwen may be happy to learn that at least one source on the web [19] thought they were safe for ferrets if they didn't eat too many.:-) 71.236.26.74 (talk) 19:37, 30 July 2009 (UTC)[reply]
There are people who consider it their moral duty to eat these peanuts when they're done with them. See [20]. I have no idea how serious these people are. Dcoetzee04:08, 31 July 2009 (UTC)[reply]
See this youtube video. Is this truth or hoax? There are a few more vids on Youtube of people opening up lantern batteries, finding something completely different inside and claiming that the AA batteries claim is a hoax. But there are loads of different brands of lantern battery on the market, so could it be that batteries made by different companies have different contents? --84.70.227.184 (talk) 09:50, 30 July 2009 (UTC)[reply]
Snopes says it's a hoax, which is a good start. There's a pretty obvious cut in the video just before the contents are visible, suggesting the small batteries were added then. AndrewWTaylor (talk) 11:04, 30 July 2009 (UTC)[reply]
Usually there are four F cells inside. F cells are like D cells except an inch or so longer. Some brands just have four D cells plus some empty space. There are holders you can get that let you use your own D cells, which is cheaper. 70.90.174.101 (talk) 11:07, 30 July 2009 (UTC)[reply]
The battery in the hoax video above is a “Heavy Duty Powercell”, which is sold by Walgreen’s. In this video, you can see the exact same brand of 6V battery, opened up to show the 4 F cells inside. Note that the hoax video contains “cuts”, which makes it easy for the hoax producers to remove the real contents of the battery, and replace it with the 32 AA cells. In contrast, the real video shows the entire disassembly process, with no cuts. Also, in the hoax video, you can see that the top of the battery does not contain any metallic contacts that the top layer of AA batteries would make contact with, so those batteries can’t be a part of a real circuit. Red Act (talk) 18:41, 30 July 2009 (UTC)[reply]
The thing is that an individual 'cell' can only produce 1.5 volts. So to make a 6v or 12v battery - you need 4 or 8 cells wired in series. If you want higher capacity (more amp-hours), then it makes more sense to use bigger cells than to wire a bunch of little cells in parallel. Also, there is a problem with wiring 'dry cell' batteries in parallel: Because the manufacturing tolerences of these individual cells aren't precise, it's likely that some of the cells will start to run down before the others. When the voltage drops on one cell that's wired in parallel with another - there is a net voltage difference that will cause current to flow from the cell that still has power into the one that's failing. Since these are not rechargeable, that current has to go someplace - and what it does is to turn into heat. Net result is that if you tried to make a LARGE 6v battery from 32 AA's, you'd need four sets of 8 cells - with each group wired in parallel and the four groups hooked up in series to get up to 6 volts. Then as one cell started to run down, all seven of the other AA's would start to drive current into it and that one weaker cell would overheat very rapidly - and probably even explode. This is NOT a good thing! Hence, they don't do that. Using 4 F-cells works fine because all four can be wired in series to get up to 6volts without any need to wire them in parallel. SteveBaker (talk) 00:47, 31 July 2009 (UTC)[reply]
I agree with Steve. 1.5 volt cells in parallel is asking for trouble. Make your cells large enough for the current demand, then place enough in series for the voltage requirement. Then there will be no current out of each cell when the external circuit is open. Edison (talk) 01:52, 31 July 2009 (UTC)[reply]
Waking up on falling
So I've noticed that when I take a ferret out of its cage when it is sound asleep, and I carry it around or breath on its nose, it takes a good half minute or so before they're really awake - which is reasonable enough. But if I were to take the same ferret and toss it in the air and catch it, it seems to wake up instantly halfway up.
Which makes me wonder: would the same thing happen for a human who is suddenly falling? If it would, then perhaps the best alarm clock would be a bed hoisted by ropes, which fell at the set time! Is this the passing vagary of a demented mind, or a possibly cool project to try out sometime? --Gwern (contribs) 09:55 30 July2009 (GMT)
Finding that your house is on fire will also wake you up immediately. Or seeing your bed surrounded by gunmen. Or getting thrown into a pool. Lova Falk (talk) 10:56, 30 July 2009 (UTC)[reply]
Sure, but all three of those are a bit hard to arrange cheaply & easy, and one might get used to the gunmen. Falling could probably be arranged with some rope and tinkering, and I don't think one would easily get used to it. --Gwern (contribs) 11:02 30 July2009 (GMT)
It must be possible to get used to falling. Astronauts experience a constant sensation of falling, but they're able to sleep with no problem. APL (talk) 13:15, 30 July 2009 (UTC)[reply]
That's true, but they are "falling" even as they are falling (sorry) asleep, so it doesn't wake them up. A sudden fall I would think would be hard to get used to, since you have been stationary for some time before the bed drops you. —Akrabbimtalk16:43, 30 July 2009 (UTC)[reply]
That's a good point; they may not sleep well, but they do sleep. But I doubt you could get used just by a few seconds a day - otherwise rollercoaster fans would quickly be bored by any free fall! --Gwern (contribs) 16:55 30 July2009 (GMT)
Of course, it would probably vary by the person, and how routinely tired they are when waking up. I have accidentally trained myself to reflexively turn off a very obnoxious alarm clock without ever waking up. Now I use my cell-phone alarm across the room that forces me to get out of bed to turn it off. For me, falling would probably wake me up, but I would very easily fall back to sleep considering I would still be comfortably in bed after the fall. After falling asleep again a few times, I think it would get to the point where I would just not wake up, like with my first alarm.
That is just me, so it would probably work pretty well who don't have trouble getting out of bed but don't get woken up by just a loud noise. —Akrabbimtalk17:15, 30 July 2009 (UTC)[reply]
What would get both you and your ferrets going would probably be a Fight-or-flight response and the adrenaline that is released in the process. If one could really train one's body to ignore the fact it is falling it might be dangerous because you would fail to wake up sufficiently to figure out whether you were heading for fluffy pillows, a bramble bush or solid concrete. 71.236.26.74 (talk) 17:34, 30 July 2009 (UTC)[reply]
I have personal experience with falling while asleep. When I was a kid, I had the top bunk of a bunk bed. I fell out several times and I didn't actually wake up until after I hit the floor. Admittedly I wasn't in the air long, but I don't remember the sensation of falling, only the jolt and the pain from hitting the floor. I also recall a news story about someone who sleepwalked and fell from a building but never woke up even after hitting the ground. Until I can find it though, I am skeptical. Sifakatalk17:40, 30 July 2009 (UTC)[reply]
My alarm clock goes with me wherever I travel, it fits in a small bag and works in any guestroom. Please explain how a contraption of ropes and pulleys that generates a local earthquake is better than my alarm clock. Cuddlyable3 (talk) 18:39, 30 July 2009 (UTC)[reply]
What APL said, and I'd note that there are groups for whom regular alarm clocks don't work, period. For example, one such group I belong to would be the hard of hearing. We generally use vibrating alarm clocks; mine works reasonably well, but still takes me a while to wake up.
Also, half the justification for this project is that it's geeky and weird! (One would think Wikipedians would be sympathetic to that impulse.) --Gwern (contribs) 07:09 31 July2009 (GMT)
Sifaka, what are the chances of someone waking up after falling off the building? Unless it was a rather short building, this might make it quite likely that they didn't wake up. Nyttend (talk) 21:49, 30 July 2009 (UTC)[reply]
A couple of years ago I read an article about something like global stress meter technology. According to the article the meter consists of about a hundred devices scattered around the globe. The devices continuously log the people's mood variations of the surrounding area, and the results are combined to form a graph. The article had a picture of one of the graphs, showing a clear peak at September 2001. The magazine I read this from is rather reliable, although not specialized in scientific content. Now I ask you, is this real, and if it is, how on earth does it work? Kotiwalo (talk) 10:05, 30 July 2009 (UTC)[reply]
One way to measure “global stress” in the sense that you mean the term is with a series of surveys, such as the International Business Owner Surveys.[21] Another form of “global stress” really is measured with physical devices, namely the stress field of the Earth’s crust.[22] But there is no physical device for measuring the amount of emotional stress felt by a large group of people in the vicinity of the device. Red Act (talk) 13:19, 30 July 2009 (UTC)[reply]
I never heard of such a thing but I don't think it would be too difficult to build something like that. A microphone and a compuer to tell if peoples voices were losing the high frequencies for instance and just stick it in a shopping centre. Or I believe some people are now trying to detect people who are stressed at airports by using a camera and analysing their movements - that sort of thing probably could be used much more reliably for overall stress in a crowd. The other possibility I can think of is it is some sort of development of the Scientology scam with E-meters. Dmcq (talk) 14:17, 30 July 2009 (UTC)[reply]
Thanks for answers, everyone. No, they were (according to the article) small devices, about a hundred of which were produced, that could detect anxiety and tension and other varieties of mental activity on the local area. These devices were scattered over the world to provide the most accurate possible global mood. But it doesn't seem feasible to me either. The graph that was shown on the article could have been made without any input from such devices, everyone knows that global stress should leap when something disturbing happens. Unless someone recognizes this as something real, I am satisfied. Thank you for your answers. Kotiwalo (talk) 14:31, 30 July 2009 (UTC)[reply]
In case it isn’t obvious, the Global Consciousness Project is solidly within the realm of pseudoscience. The devices that project uses are just random number generators, and don’t actually measure people’s mood variations. Red Act (talk) 15:22, 30 July 2009 (UTC)[reply]
Stock markets give an index of mood. A global index-of-indicies (of which at least one exists although I dont remember the details) would give a global mood index. 78.144.197.8 (talk) 17:07, 30 July 2009 (UTC)[reply]
The stock market measures mood - but mixed up with a lot of other variables. I don't think you could call that reliable. This thing is a hoax...there is no way to do what they claim. Even asking people how they feel is unreliable. SteveBaker (talk) 00:39, 31 July 2009 (UTC)[reply]
With modern internet and social network websites providing plentiful information, I wonder why the designers chose to feed "random" input into this worldwide sensor grid? Actual data can be fed in and processed, if they seek a real result. The presupposition that a random number generator would be influenced by "mood" is totally preposterous - if any such mechanism were discovered, I think we would conclude that the random number generator was defective, and that it was actually a predictable, controllable system that was receiving input of some form. I'm curious what proposed mechanism exists to couple the random number electronics with "mood" - again, if such a mechanism exists, it should be nonrandom and repeatable. This project is very pseudoscientific. Nimur (talk) 15:50, 31 July 2009 (UTC)[reply]
The reason the designers aren’t using real data is because the designers have no interest at all in developing a global mood index. The whole point of the “experiment” is to try to prove that “psychic energy” or whatever can affect hardware random number generators.
I personally don’t have any problem in principle with people doing a science experiment to test whether some phenomenon exists, even if there is no known mechanism by which the phenomenon could occur according to currently accepted scientific theory. Indeed, that description would describe the circumstances under which the Geiger–Marsden experiment was performed. In that experiment, there was no good reason to test for large-angle deflections of the beam, based on the then-accepted plum pudding model of the atom. What makes the Global Consciousness Projectpseudoscientific bullshit is the methodology used, not the subject matter.
It would be possible for the Global Consciousness Project to do an actual, valid science experiment to test if global mood can affect random number generators, requiring essentially no more time or money than what those people have already invested. For example, they could hypothesize before the experiment that there will be a correlation between the moodyornot.com percentile on a given day, and the average values of the numbers created with those random number generators on that day. After making that hypothesis, they would then gather data for a predetermined large number of days, and then test for a correlation, using all the data they collected.
Unfortunately, the GCP people have chosen to avoid a reasonable scientific methodology like that, and instead retrospectively cherry-pick little bits of their data at carefully chosen times, based on their subjective ideas of what the global mood should be in specific instances that they’ve chosen, in such a way that it will make what they’re trying to prove look valid. The project suffers from a severe case of selection bias, making their “results” completely meaningless. Red Act (talk) 17:52, 31 July 2009 (UTC)[reply]
Perpetual motion from electrolysis of water under high pressure?
I have come to the conclusion that the electrolysis of water under high pressure must take more energy than for water under low pressure, since if water in a very deep lake (lets say five miles deep) was converted into hydrogen and oxygen at the same efficiency as normal pressure, this could fill a float with a cable (or drive a turbine) to generate electricity on its rise to the surface, the water could be recycled and further energy gained by using the hydrogen and oxygen in a fuel cell -though this would be less then the energy used in electrolysis, but combined with the "flotation generator" energy, would provide more than enough to repeat the cycle. Unless this really is a scheme for perpetual motion, which I doubt,what would actually happen? —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 10:21, 30 July 2009 (UTC)[reply]
Pressure doesn't really have anything to do with it. You could have a pressurised champer that only allowed in water at normal pressure. I think you will find that the answer is because of heat. What you are saying would eventually make the water cooler and cooler and more and more energy would be needed for electrolysis.--58.111.132.76 (talk) 12:23, 30 July 2009 (UTC)[reply]
What I would expect is that the standard electrochemical potential would increase as the water pressure increases since hydrogen and oxygen at pressure are at higher energy than when they are at low pressure. This would offset the extra energy obtainable from the gases being at depth.
However if it doesn't do this, the maybe it could form a perpetual motion machine. However the variation of electrochemical potential is well known (there are well known equations describing it as well), and I wouldn't expect any net energy gain.83.100.250.79 (talk) 13:22, 30 July 2009 (UTC)[reply]
See this. It is estimated that there is 5% reduction in power needed for electrolysis of water under high pressure. That is, of course, an estimate. Any actual implementation will likely be less efficient due to numerous other factors. -- kainaw™13:51, 30 July 2009 (UTC)[reply]
Although it's been published I'd tend to ignore that in relevence to the original question-- (actually it doesn't really seem to have anything to do with the original question..)
The process can be split into two steps:
H+ + e- >>> 1/2 H2 (absorbed on electrode)no real volume change - chemical potential independent of pressure
and
H2 (absorbed on electrode) >>> H2 (gas free under pressure)increase in volume therefore increase in energy(work) required as pressure increases
The same applies for the production of oxygen.
The usually accepted view is the the increased pressure will increase the energy required for elecrolysis - offsetting any extratable amount to make both equal. That's just one of the standard thermodynamic principles - ie that energy can't be made from nothing.
I can't think of a reason why this would change in this example - so I think it wouldn't be a perpetual motion machine. If it does turn out to be different then that would require a lot of explaining. The second equation above is the reason why mor energy is required for electrolysis at higher pressures. (edited once)83.100.250.79 (talk) 14:30, 30 July 2009 (UTC)[reply]
Casimir effect-flotation in a vacuum?
Could the low energy cavity between two fixed Casimir plates lead to both plates floating upwards even in a vacuum if made of a very light metal such as lithium? Would the low energy be equivalent to a lightweight gas balloon under normal atmospheric pressure, or for that matter the proposed "vacuum balloon" under normal pressure? Could such a small force be measured if it existed?Trevor Loughlin (talk) 10:29, 30 July 2009 (UTC)[reply]
Wouldn't the Casimir effect push the plates outward from each other, and not 'up' or 'down'? --Gwern (contribs) 10:38 30 July2009 (GMT)
Normally, but the plates would be fixed in place to prevent this. I just wondered if a "more then vacuum" would float like a balloon in a normal vacuum. Probably a silly question since it compares energy density to gas density, no doubt entirely different. —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 11:09, 30 July 2009 (UTC)[reply]
Well, if the plates are fixed, then nothing will happen. If you put yourself between two walls fastened together, and push outwards, the walls will go nowhere if they're really 'fixed'. The net force would be negative. And consider the symmetry: if we have the 2 parallel plates - || - that we need, which direction would they hypothetically go? There ought to be a unique direction, but that's rather asymmetrical.
A 'v' shape might work, but I think what would happen is the forces in the wider part would cancel the forces in the narrow part, although it'd take a physics guy to say exactly what happens there. If a 'v' shape could work that way, it seems suspiciously like perpetual motion... --Gwern (contribs) 11:30 30 July2009 (GMT)
In the TV series 24 episode 5, Jack Bauer "flushes" people out of their safe room, by creating a poisonous gas with the help of ammonium and something else he found in the kitchen. Does anybody know which substances he mixed and what was the name of the poisonous mixture (ammonium stearate???) Does anybody know what substances he mixed in order to create "ammonium distrate"? Lova Falk (talk) 10:49, 30 July 2009 (UTC)[reply]
Ammonium Stearate is a compound, I don't know what else "distrate" could be, but "distrate" is not a chemical term.
According to [http://www.pesticideinfo.org/Detail_Product.jsp?REG_NR=00183900086&DIST_NR=048733 this] "Distrate" appears to be a pesticide containing alkyl dimethylbenzyl ammonium chloride and alkyl dimethylethylbenzyl ammonium chloride. This is listed as acutely toxic, carcinogenic, a developmental toxin and an endocrine disruptor. Probably not something you'd find in the average kitchen. sometimes used as a disinfectant. Please do not try mixing things with things at home - remember, 24 is fictional! TonywaltonTalk14:37, 30 July 2009 (UTC)[reply]
Actually the listing you gave says it's effects are not known with certainty, except that it is poisonous to aquatic life.
(edited twice due to error) However mixing this with an alkai (eg sodium carbonate or sodium hydroxide) would not do anything under these conditions
Here's a list of things that contain the same compound(s) [23]
There's a risk assesment here [24] (long article!) - There doesn't seem to be any such reaction that could clear out a room - probably just "hollywood chemistry" aka 'bull' ...83.100.250.79 (talk) 15:01, 30 July 2009 (UTC)[reply]
The makers of TV shows often are very "creative" when the characters are making bombs or poisons. This is simply to protect the viewers. It is very possible that either the mixture doesn't work at all or is much less effective than portrayed. Sometimes the explosive materials are not revealed at all. Kotiwalo (talk) 15:15, 30 July 2009 (UTC)[reply]
No need to make it easy. One of my children read a chemistry textbook and then went off an mixed up something from chemicals round the house that produced a poisonous gas and I had to open the doors and windows to get rid of it. Good understanding of the chemistry but not much sense. Dmcq (talk) 20:12, 30 July 2009 (UTC)[reply]
Sorry about that. Luckily in this case what jack bauer did doesn't seem to work. It's actually surprising how difficult it is to mix up something toxic in the home - despite the wide variety of chemicals in the garage, and kitchen.. There's actually a way to make hydrazine in the home very easily. (not telling) - and bleach should probably be banned...83.100.250.79 (talk) 20:49, 30 July 2009 (UTC) I spent most of my years from 12 to 20 trying to do just the same... probably a common story.83.100.250.79 (talk) 20:50, 30 July 2009 (UTC)[reply]
If you want to drive people out of a room using common household chemicals, simply mix ammonia and clorine bleach. This releases clorine gas in dangerous quantities, and clorine gas is really irritating to eyes and lungs even in small quantities. DO NOT TRY THIS, even in small amounts, as an experiment, except in a well-equiped laboratory under an exhaust hood. Unfortunately, quite a few people do this "experiment" by accident every year, usually by using first ammonia and then bleach, or vice versa, while trying to remove stains from a toilet bowl. -Arch dude (talk) 23:49, 30 July 2009 (UTC)[reply]
It sounds like a bad analogy to complexity theory with handwavey, inaccurate terminology. There have been numerous attempts to describe the brain or the mind as a "chaotic" system in the past, but they range from "stretches of terminology" to "wild speculation and making stuff up." Nimur (talk) 15:09, 30 July 2009 (UTC)[reply]
The article describes research into how ideas, and hence intelligence, arises in the brain. The model and terms used are similar to the engineering of a regenerative radio receiver where forming an idea is analogous to tuning in to a particular transmission frequency out of many. The idea is that there are two energy states in the brain: 1) an incoherent or chaotic state where energy is dissipated at random comparably to thermal noise in a radio, and 2) a particular thought gains critical mass (or in the terms of the NS article triggers a sand avalanche). The latter event is proposed to correspond to a particular frequency and phase of resonance in neurological activity. The significance of one frequency and phase is that it is a unique focus for accumulating energy. Random energies at other frequencies and even at the same frequency but a different phase do not contribute to the resonance. They represent chaotic thoughts that become imperceptible as the significant resonance takes hold. These speculations suppose that there is a mechanism in the brain for collecting energy at a unique frequency and phase, with some correlation to intelligence, which the researchers report having detected. The significance of "an extra millisecond" could be that longer time taken to integrate a frequency achieves better elimination of noise. Compare that with a chess player taking extra time to decide a difficult move.
However while this frequency-selective model lends itself to pretty simulations on video the reported data is not convincing. Only 17 children were tested for EEG activity and IQ. Their IQ spread is not stated. 1 millisecond may correspond to a large or an insignificant phase change depending on the frequency concerned. I am doubtful when I read that 1 ms longer in one brain state increases IQ and 1 ms shorter in the other brain state increases it by a different amount. Cuddlyable3 (talk) 17:51, 30 July 2009 (UTC)[reply]
The abstract linked to says "The electroencephalogram (EEG) was recorded from 19 scalp locations from 378 subjects ranging in age from 5 years to 17.6 years." So the journalist or someone had made a mistake - it was 378 children, not 17. 78.146.235.174 (talk) 10:58, 31 July 2009 (UTC)[reply]
I was thinking that the "phase" was something like the phases of water (solid, liquid, gas) or phase of regular or chaotic rather than a phase in the electronic sense. I recall the AI technique of Simulated annealing. The phase shift could be when a lot of things are thrown together at random, some of which catch on as new ideas. The longer this random phase, the more random throwing together of things, the more of the problem-space is searched. Tell me if you disagree. 78.146.235.174 (talk) 10:47, 31 July 2009 (UTC)[reply]
In the context of brainwave frequency measured in Hz it looks like phase must mean phase angle, especially when the terminology is "phase shift" not "phase change". We read "..the brain often synchronises large groups of neurons to fire at the same frequency, a process called 'phase-locking'." Simulated annealing can regularise crystal structures but is not AFAIK an established technique for artificial intelligence. Cuddlyable3 (talk) 23:05, 31 July 2009 (UTC)[reply]
Simulated annealing is a numerical technique used to solve many "poorly conditioned" mathematical problems (including the physical crystallization simulation that gives it its name). Many artificial intelligence problems can be put into a form such that simulated annealing returns the numerically optimal solution. Nimur (talk) 21:15, 2 August 2009 (UTC)[reply]
Saddle joints
Hi everyone I'm having trouble understanding how a saddle joint works. I understand the diagrams I have seen showing a concave surface sitting in a convex surface; but I just can't see in my mind how this works in the carpometacarpal joint of the thumb. I've looked at the external links listed in the 'saddle joint' article and I even have a copy of Gray's anatomy right next to me but I just don't 'get' it. The article on saddle joints states that the saddle joints are capable of flexion and extension, abduction and adduction and circumduction. Perhaps I don't understand because I don't know what flexion/extension or abduction/adduction of the thumb looks like. One other thing about saddle joints that I don't get is that I can move my thumb up, down, left and right and can spin it round in a circle (which I believe is circumduction). These are all things that a ball and socket joint can also do. The article on saddle joints says that they have no axial rotation, which I believe a ball and socket joint does have. What would be different about our thumbs if they had axial rotation? Basically what I'm asking is what would be different about our thumbs if a ball and socket joint held them in place instead of a saddle joint? Hope this makes sense; as you can probably tell I'm rather confused about saddle joints. Thanks in advance to anyone who helps. RichYPE (talk) 18:47, 30 July 2009 (UTC)[reply]
If you had a ball and socket thumb you'd be able to twist your thumb (around it's length - like a door knob turns)
Compare this image http://www.heumann.org/body.of.knowledge/a8/rdts45.gif with that a universal joint - can you see how if one end turns the other end must also turn. - With a ball and socket joint the other end doesn't turn... (did that help - or just more confused ?!?
Also looking at the image again - note that the two surfaces are the same - imagine how they can move against one another, and how far they can move. The thumb joint will be less simple - but it is 'the same'83.100.250.79 (talk) 19:23, 30 July 2009 (UTC)[reply]
Practical problem - something light and compact to stand on
What could I use to stand on that will raise me about two feet in the air? The criteria are that it must be light enough and compact enough to be carried by hand on public transport for some time, and that there is not enough time to do major woodworking for example. It can lean against a wall like a ladder while I am standing on it, although a ladder itself would be too big. I only need to stand on it for about a minute. I would prefer something that's cheap enough to dispose of after I've used it. 78.144.197.8 (talk) 19:27, 30 July 2009 (UTC)[reply]
See if you can find s.th. like this [25] Try your local home improvement box or a store for supplies for the elderly, a kitchen store might also carry s.th. similar. 71.236.26.74 (talk) 19:48, 30 July 2009 (UTC)[reply]
That would be ideal if I had one already, but I'd rather not pay a lot just for one use for less than a minute. I've been thinking that perhaps I could strengthen a cardboard box somehow, which could be folded flat to carry. Other design possibilities would be three pieces of wood to form a thin "A" shape, or two sheets of something in an "X" shape with another sheet on top to stand on. I'm still looking. 78.144.197.8 (talk) 20:20, 30 July 2009 (UTC)[reply]
I was thinking the same. You probably need two cardboard boxes - one to be the shell, the second the reenforcement. Cut up the second so you have diagonal bits which will fit into the first, with each diagonal cut with a half-width cut half way down. That way they slot together to make an X shape, which will brace the shell box. This, including the shell box, can be collapsed and folded during transit (a roll of parcel tape will help reassembly, but shouldn't be necessary). If further support is required, more sheets of the donor box cut with slits at either (horizontal) edge, so they can be looped around and slotted into themselves, forming tube(ish) structures - put these tubes in between the arms of the X both to hold weight and to prevent it from folding sideways. -- Finlay McWalter • Talk20:26, 30 July 2009 (UTC)[reply]
Finlay is on the right track. Go to your local wines&spirits store, and get three empty booze boxes. They are heavyweight (usually "triple-wall") corrugated cardboard, and usually have the interlocking cardboard pieces called an "egg crate" inside, to keep the bottles from rubbing on each other during shipping.
Carefully chosen, you should be able to get two that stack on each other quite nicely. Use the third one as a step to get up on the stack of two. Good luck! --DaHorsesMouth (talk) 22:42, 30 July 2009 (UTC)[reply]
And now for the real question: what are you going to be doing for a minute that needs you to be two feet taller? (If you are going to be lifting something heavy or firing a weapon, for example, you might have to consider strength of materials and their stability. This is not just idle curiousity, but most of it is.) // BL \\ (talk) 01:12, 31 July 2009 (UTC)[reply]
Wow, all these baroque solutions. All you need is a folding two-step ladder, which you can buy at any decent home supply store. Looie496 (talk) 03:53, 31 July 2009 (UTC)[reply]
Go to a local convenience store, they'll probably have scads of milk crates out back. Ask the people who work there if you can have a couple, they most likely won't mind if you take them. Milk crates are strong as hell, light, and stackable. Plus you can carry your tools in them.
How long does this takr women to lose most of extra weight after when a baby is born. Average woen is still overweight over even 5 month after the baby is born. Like a english teacher at school, she got her baby in late January, and the teacher temporaily on intermission absence shows up every week in June, and her face is now as wide as a honeydew melon, and I made girls upset by criticizing the teacher by her weight. Until how long after the baby will average women lose extra weight. 9 month?--69.228.145.50 (talk) 21:19, 30 July 2009 (UTC)[reply]
I'm not sure where you live, but where I live, openly criticizing any woman for being overweight, especially when other women can hear you, is considered extremely rude and socially just unacceptable. And if it's after a pregnancy, then your comments are way out of bounds. (At least, where I live they are.) The speed of weight loss is highly variable and depends on hormone levels and whether she is breastfeeding, as well as the usual factors of exercise and diet. Trying to slam back to the previous weight could be harmful to both the mother and child. So, knock off making comments like that. Tempshill (talk) 21:37, 30 July 2009 (UTC)[reply]
A very wide face can sometimes be moon face, which can have a variety of causes, some of which are very serious. I suggest you apologize to your teacher and make some efforts at becoming a more compassionate human being. --Sean14:11, 31 July 2009 (UTC)[reply]
To add some balance to the critique of the op's conduct, I doubt he actually said it to her face. And in any case, we're talking about a school environment here, almost anything goes. The condescending devilry of the responses will probably not be appreciated. —Preceding unsigned comment added by 92.8.113.198 (talk) 01:11, 1 August 2009 (UTC)[reply]
According to the OP, other people found it offensive as well, so I doubt it's fair to say 'anything goes'. Indeed there's no evidence that anyone but the OP thought it was an acceptable thing to say. Just because the OP is perhaps unaware of norms in human communication doesn't mean we should accuse the OPs peers and every other school child of having the same issue. Indeed if I was one of the OPs peers I would be deeply offended by the insinuation Nil Einne (talk) 03:12, 1 August 2009 (UTC)[reply]
But more to the point none of us have any right to hell him how he conducts himself. When people ask questions they want answers not to be lectured on their manners. This isn't finishing school. —Preceding unsigned comment added by 92.19.119.89 (talk) 22:44, 2 August 2009 (UTC)[reply]
The article pregnancy quotes The National Health Service that recommends that overall weight gain during the 9 month period for women who start pregnancy with normal weight be 10 to 12 kilograms (22–26 lb). Some of this increase is fat that will be used to produce milk for breastfeeding. After childbirth, eating disturbances such as loss of appetite can be symptoms of postnatal depression. This may be simply "Baby Blues" but medical advice should certainly be sought from a doctor, not Wikipedia. Weight loss is highly variable among lactating women[1].Cuddlyable3 (talk) 12:56, 1 August 2009 (UTC)[reply]
homemade radiation treatment of food without cooking
Can a low-power dose of defrosting microwave radiation prolong the life of refrigerated (non-frozen) meats or milk without significantly affecting taste quality? If this is not so, is there any type of radiation treatment that would kill bacteria without cooking the food? Are there plasmid-attacking agents that would be harmful to bacterial DNA but not harm human cells once in the digestive tract? John Riemann Soong (talk) 22:01, 30 July 2009 (UTC)[reply]
As AlmostReady just said, you need ionizing radiation (X-ray or gamma) and not microwave radiation to sterilize food. And, moreover, you need extremely high doses of ionizing radiation. To be precise, you need doses high enough to damage every living cell, every bacterium or spore, in the food product to be preserved. And the radiation doses required to do so are astonishingly high, orders of magnitude higher than those sufficient to kill a human. Some bacteria - notably Deinococcus radiodurans and some others mentioned in D. radiodurans article - are especially good at surviving irradiation. --Dr Dima (talk) 22:27, 30 July 2009 (UTC)[reply]
Now, on the second part of your question, there are certainly ways to preserve food without actually cooking it. Preserving food with salt is very common. Fermentation is another way of preserving food, by actually using some (normally harmless) bacteria to produce chemicals that kill or inhibit growth of other microorganisms. We have an entire article devoted to Food preservation. There are also antimicrobial chemicals defined as food preservatives, which may be what you are looking for. --Dr Dima (talk) 22:44, 30 July 2009 (UTC)[reply]
Actually I'm looking at preserving milk and fresh meat ... yeah I use vinegar and pickling techniques but I'm just looking if there's anything to extend the life of refrigerated (non-frozen) stuff. John Riemann Soong (talk) 04:31, 31 July 2009 (UTC)[reply]
For preserves and juices they sometimes use high pressure, but "at least 10 MPa" [26] is probably way above what zoning regulation and code would let you have at home. 71.236.26.74 (talk) 23:54, 30 July 2009 (UTC)[reply]
And of course for UV to work, the thing you're trying to preserve has to be transparent to UV light (which isn't always the same thing as "transparent"!)...so for most things, you'll only kill the bacteria on the surface. SteveBaker (talk) 00:19, 31 July 2009 (UTC)[reply]
Actually, you can get a similar effect (though not as good as commercial methods), by microwaving milk just long enough to get it to ~70 C and then removing it quickly and placing it in a cold water bath to rapidly cool it back down. It's a trial and error thing though because if the milk boils (100 C) you will have ruined the taste/composition. The time required will depend on the volume of milk and the intensity of your microwave. Also, any pasteurization process will still have some effect on the taste, whether the difference if important to you is a matter of personal taste I suppose. Dragons flight (talk) 05:31, 31 July 2009 (UTC)[reply]
I really don't think we should be recommending using a microwave to pasteurize milk (or anything else for that matter). The heating is far too uneven. In order to get the entire container of milk to the desired temperature and keep it there for long enough to kill the bacteria, some parts of the milk will be getting up towards the temperature that it'll start to 'cook' and taste funny - while other parts are either not hot enough - or don't get hot enough for long enough. You need a much more controllable heat - and you need to keep the liquid stirring so that it doesn't develop hot spots or retain cooler areas in which bacteria can survive. If you don't kill all of the bacteria - then the ones that escaped will recolonize the parts of the milk that you sucessfully pasteurized. This happens rather quickly - and then you'll be back to square one. SteveBaker (talk) 13:27, 31 July 2009 (UTC)[reply]
Yeah, that can work too -- we use a similar setup in the lab when we want to heat something up without getting up to 100 C, and it can reach 80 C no problemo (but not any higher than that), so in this case that's a wonderful choice! 98.234.126.251 (talk) 08:21, 1 August 2009 (UTC)[reply]
Puffins are fatty aquatic birds. The fatty aquatic bird most often eaten is duck. Therefore, all others tend to be compared to how similar they are to duck. So, to someone who hasn't had puffin, you'd say "It is almost just like duck." -- kainaw™00:53, 31 July 2009 (UTC)[reply]
1. Assuming a constant internal temperature, how rapidly does a wall-mounted room air conditioner lose its ability to cool the room (or, at least, lose efficiency) as the outside temperature rises? By way of example, suppose the room is at 27 degrees C, the air conditioner is continuously attempting to cool the room to 25 C, and the outside temperature starts at 32 C and rises to 37 C. I'm not using the numbers to try to get someone to cough up a formula; I'm just using them to illustrate what I'm trying to get at.
2. When cooking a grilled cheese sandwich on a frying pan which is atop a gas stove, I imagine a smaller pan will transfer heat into the sandwich faster, assuming the pan surface is heated more or less evenly by the gas flame. If it's as I expect, does a pan with half the surface area heat the sandwich twice as quickly? Tempshill (talk) 02:30, 31 July 2009 (UTC)[reply]
You would need to measure the temperature of the condenser at the outside of the air conditioner. Its ability to transfer heat to the outside is a function of the differential temperature between the condenser and the ambient air; as the difference becomes smaller the rate of cooling decreases. There is a formula somewhere, but I lack the engineering background to dig it up. Someone else I am sure will.
Actually, it depends on how you cook the sandwich. Once the pan is "at temperature", it is mainly acting to transfer the energy directly from the flame to the food. Metal, being a good thermal conductor with a low specific heat will basically pass the energy quickly and efficiently from the flame to the sandwich. Placing a cold sandwich will sap some of the heat from the pan, and the amount of energy that is lost is a function of the mass of the pan. A heavier pan will lose less of its energy to the cold sandwich, so a heavier pan will cook a sandwich faster assuming that both pans are "preheated". If you are starting with a cold pan and a cold sandwich, then the lighter pan will heat up faster, and thus start cooking the sandwich faster. So it depends on your methodology. --Jayron3203:25, 31 July 2009 (UTC)[reply]
As a first approximation to question 1 - the rate of heat flow is proportional to the temperature difference (see Heat transfer), however as mentioned above ^^ this is the temperature difference between the outside air, and the temperature of the 'radiator' on the outside of the air conditioner (which is by default always hotter than the temperature inside the air conditioned room). However the temperature the radiator reaches will depend on the outside temperature. maybe someone else will be able to finish the answer.83.100.250.79 (talk) 06:24, 31 July 2009 (UTC)[reply]
For question 1 only : I understand the question but more information is required. I don't know if you know how air conditioning work but u can model it as a heat engine. So what is the power (watts) of the AC? What kind of coolant? Efficiency? For simplicity go read http://en.wikipedia.org/wiki/Carnot_cycle—Preceding unsigned comment added by Alvi123 (talk • contribs) 00:56, 3 August 2009 (UTC)[reply]
Retain Martian water using deuterium!!??
Woke up with this BRILLIANT{??} idea! Heard that Mars and other planets significantly lighter than Earth gradually lose their water as it evaporates into space. What about flooding Martian plains with "heavy water". This means the H in H2O are the deuterium or tritium isotypes, and heavier than ordinary water, while being chemically exactly the same. Would this tactic permit Mars to retain water better? All you would have to do is find a vast reservoir of this kind of water. Btw, if a person only drank heavy water, and ate foods that had been irrigated with this water, how much heavier would they be than persons who only drank normal water? Myles325a (talk) 02:52, 31 July 2009 (UTC)[reply]
Yes. All you would have to do is find an ocean of heavy water, which sounds simple until you consider that the natural abundance of deuterium is 0.015%, so there are no such vast reservoirs. – ClockworkSoul02:56, 31 July 2009 (UTC)[reply]
I don't know if heavy water evaporates more slowly and acts as vapor differently than regular water, but our heavy water article does say that mammals die when about half their body water has been replaced with heavy water. It goes into some detail about the death rate of other life forms. Everybody dies except for bacteria. Tempshill (talk) 03:04, 31 July 2009 (UTC)[reply]
Heavy water has a slightly higher boiling point. With care (and huge amounts of time and energy) one can use distillation to separate (or at least enrich) a mixed sample. But there are other, more efficient ways of doing it than direct fractional distillation. DMacks (talk) 05:32, 31 July 2009 (UTC)[reply]
Which leads to an answer to the first part of the question - no - heavy water is so similar to normal water that it would be lost (almost) just as fast.83.100.250.79 (talk) 06:17, 31 July 2009 (UTC)[reply]
Also, to answer your last question: this site cites Review of Physiological Chemistry, 16th ed. in stating the hydrogen composes 10% of the human body by weight. Since deuterium has 1.998 times the mass of hydrogen, if all hydrogen in the an ecosystem was replaced by deuterium, and our biochemistry was sufficiently altered so we don't, you know, die... our mass would be increased by a total of about 10%. – ClockworkSoul03:26, 31 July 2009 (UTC)[reply]
Do artificial sweeteners taste like sugar to non-human species?
Do artificial sweeteners only fool human taste buds, or do they taste like sugar to other species too? If the latter, do they taste like sugar to all animals? Do insects confuse artificial sweeteners with the real thing? —Preceding unsigned comment added by 98.114.146.177 (talk) 03:27, 31 July 2009 (UTC)[reply]
They don't even fool human taste buds. Just about anyone can tell the difference between real sugar and any artificial sweetener. Merely because both are sweet, doesn't mean that they taste identical. --Jayron3203:32, 31 July 2009 (UTC)[reply]
I think this is a legitimate question. Say for example, you make a big mound of artificial sweetener right next to an anthill. Will the ants collect it and take it back to the nest? Or will they say "screw that, that stuff isn't food"? Dcoetzee04:15, 31 July 2009 (UTC)[reply]
Oh, it is a perfectly legitimate question; I did not address whether or not animals would eat artificial sweetener or not; however the premise that it "fools" humans, except those that willfully allow themselves to be fooled, is incorrect. Artificial sweeteners are readily recognizable as not-sugar by anybody. Again, not that there's anything wrong with that, but it doesn't mean that they are indistinguishable from sugar by humans. --Jayron3204:22, 31 July 2009 (UTC)[reply]
I left a half-empty bag of popcorn out overnight, and because I leave the windows open, I now have a trail of ants marching across my floor. I removed the bag earlier, but they are still here (and I don't want to spray and kill them). So I have just poured a small mound of Sweet 'n' Low (saccharin) next to their trail. Surprisingly enough, about a dozen ants have actually stopped at the mound, but I don't know why. They don't all respond to it like thye would if it were a pile of real sugar, though. HYENASTE06:23, 31 July 2009 (UTC)[reply]
Insects - at least some of them - have pyranose receptors and furanose receptors; so anything that elicits response from either one will presumably taste to the insect as a corresponding type of sugar. --Dr Dima (talk) 06:39, 31 July 2009 (UTC)[reply]
What's this about fooling taste buds? Sweet reception works by combining different chemical effects. Try http://en.wikipedia.org/wiki/Sweetness#Historical_theories_of_sweetness."Simply put, they proposed that to be sweet, a compound must contain a hydrogen bond donor (AH) and a Lewis base (B) separated by about 0.3 nanometres. According to this theory, the AH-B unit of a sweetener binds with a corresponding AH-B unit on the biological sweetness receptor to produce the sensation of sweetness." + a third nonpolar London force binding site. If you look at table sugar, sucrose, sure enough, you get a hydrogen bond donor (the OH groups), a weak Lewis base region (the ether oxygens with their lone pairs) and some nonpolar regions. And then there are more elaborate theories based on the study of the sweet receptor with 5 more regions or something, but that's the basic idea.
The thing though, is that I also guess that the sweet receptors also send inhibitory signals to bitter receptors -- or the sugar molecules in themselves activate bitter-inhibiting receptors at the same time they are exciting sweet reception. This would be in order to suppress the sugar's OH groups binding to the receptors that give alcohols their bitter taste; some sweeteners inhibit less effectively or trigger receptions that normal table sugar wouldn't. (At sufficiently high concentrations the bitter receptors will be uninhibited again -- have you tried eating pure sugar, or lived near a sugar factory? At sufficiently high concentrations even sugar becomes bitter.) But the basic motif of the sweet receptor I would think be conserved. John Riemann Soong (talk) 07:08, 31 July 2009 (UTC)[reply]
What do hummingbirds think of artificial sweeteners, as a matter of interest? It's reasonably common for people to troll bird forums/newsgroups with suggestions that people put Nutrasweet and similar in their hummer feeders, deliberately feigning ignorance of the lack of nutritional value in the stuff... --Kurt Shaped Box (talk) 09:11, 31 July 2009 (UTC)[reply]
It's a common legend that hummingbirds will drink nutrasweet (or other zero-calorie sweeteners) to the point of starving themselves if it's more easily available than real sugar. I'm not sure that I've ever seen a good confirmation or debunking of this legend. (Usually would-be debunkers miss the point and repeatedly insist that nutrasweet isn't toxic!) I'd be interested to know the answer to this question, but I'm not eager to run the experiment myself. APL (talk) 14:17, 31 July 2009 (UTC)[reply]
how are scientists able to see something that is billions of light years away
On July 11, 2007, using the 10 metre Keck II telescope on Mauna Kea, Richard Ellis of the California Institute of Technology at Pasadena and his team found six star forming galaxies about 13.2 billion light years away
How is this possible. If it takes Light 13.2 billion light years to reach, which is an insane distance, how in the hell can we see these objects.
Ivtv (talk) 03:31, 31 July 2009 (UTC)[reply]
We're seeing the light that these objects emitted 13.2 billion years ago which is just now reaching us. That's why looking at far away objects is also useful for figuring out what the early stages of the universe were like. There's also the concern that the farther away something is, the lower the intensity of the light is that reaches us and the smaller the objects appear, which is why we need extremely sensitive detection devices (very large and powerful telescopes) to see these things. Rckrone (talk) 03:47, 31 July 2009 (UTC)[reply]
Because galaxies are huge. Imagine every second you have ever driven in the past say, 15 years, passing by in 1 second and maintaining that speed for 1000 years and still have gone only 1% of the size of a galaxy. The telescope is a million times the area of your pupils combined and accumulates the picture over hours. Sagittarian Milky Way (talk) 04:28, 31 July 2009 (UTC)[reply]
Did the Apollo lunar missions have a contingency plan for damaged space suit during EVA?
Did they have a plan for dealing with a torn/punctured/leaking space suit during EVA? Would something like duct tape be able to stop a small leak from a space suit? —Preceding unsigned comment added by 98.114.146.177 (talk) 03:54, 31 July 2009 (UTC)[reply]
Oh, the annoyance of snippet view in Google Book search. A glove was the most llikely spor for a puncture, because they handled core drills and other tools. The following suggests that for a glove puncture on more recent (Russian?) suits, a cuff in the arm could be inflated to prevent a fatal loss of oxygen in the suit and helmet, perhaps giving time to get inside: "Walking to Olympus: an EVA chronology - Page 71.by David S. F. Portree, Robert C. Treviño, United States National Aeronautics and Space Administration. History Office - 1997 -"The suit was sized for specific cosmonauts by pulling or releasing cables and pulleys in the arms and legs. • In the event of glove puncture, a forearm cuff..." Another snippet, from "Protecting the Space Shuttle from Meteoroids and Orbital Debris - Page 17 , NASA, 1997, refers to time a small puncture could be survived: "... a 30 minute supply of oxygen in case of a 4 mm puncture in the space suit" On an EVA at the ISS, an astronaut noted that a cut had gone through several layers of the glove, but had not penetrated the pressure layer, so he ended the EVA early. Edison (talk) 14:58, 31 July 2009 (UTC)[reply]
The Apollo/Skylab A7L space suit had a 13 layer Integrated Thermal Micrometeroid Garment that was worn over the Torso Limb Suit Assembly. If the outer garmet were breached and the inner presure suit punctured, I would think it would be very difficult if not impossible to gain sufficient access to the puncture to attempt a timely repair. -- Tcncv (talk) 20:25, 1 August 2009 (UTC)[reply]
Name of body groove?
Is there a name for the groove that male athletes have? It starts from both hips comes forward diagonally down toward the groin area. A groove between the upper thigh and the lower abdomen. It's kind of hard to describe without a photo. --68.102.170.184 (talk) 06:53, 31 July 2009 (UTC)[reply]
I think a bit more correctly, or pedantically if you will, the surface feature is the inguinal groove, which marks the path along which the inguinal ligament runs. - Nunh-huh09:28, 31 July 2009 (UTC)[reply]
Hi guys. Here's an article from telegraph.co.uk. I understand the first bit of that article about how "attractive genes" are selected for. But I don't get the following three sentences near the end:
A study in 2006 by scientists at the London School of Economics found that good-looking parents were far more likely to conceive daughters.
He suggested this was because of differing "evolutionary strategies" that each sex has adopted to survive, and which had been subtly programmed into their DNA.
Mr Kanazawa said: "Physical attractiveness is a highly heritable trait, which disproportionately increases the reproductive success of daughters much more than that of sons.
If attractiveness increases the reproductive success of daughters more than sons, surely all this means is that those daughters of attractive parents will have more children than their brothers. I don't see why a gene causing attractiveness would also cause one to have more daughters. Please help. TIA! Zain Ebrahim (talk) 07:52, 31 July 2009 (UTC)[reply]
Every child is an investment for the parents, with the pay-off being further offspring. For females, their reproductive success depends on attractiveness. For males, it depends on other factors (smarts, I would hope ;-). So if you are attractive, you can make sons that have an average number of offspring, or daughters, that have a larger number of offspring. The second strategy is better, and natural selection will hence favor that combination of traits (attractive+propensity for daughters) over the other 3 combinations. --Stephan Schulz (talk) 09:16, 31 July 2009 (UTC)[reply]
Not to mention, although we don't seem to have an article on it, organisms can change the average gender of their offspring (for example, reptile eggs can assume gender based on temperature; and there are more indirect genetic examples) or more directly by infanticide; they would want to do this because by Fisher's law the ESS for sex ratio is 1:1 - if there's a temporary deviation then there're arbitrage opportunities. (If there're only a few females, then female offspring are a win; if there's a shortage of males, obviously you might want to have male kids.) --Gwern (contribs) 10:34 31 July2009 (GMT)
I'm very bothered by the phrase "scientists at the London School of Economics"...what is a reputable scientist doing at an economics school? SteveBaker (talk) 13:13, 31 July 2009 (UTC)[reply]
Perhaps you might consider enrolling in the London School of Economics, you might get some really valuable insights from it (that is, if they'll let you in). ;-) 98.234.126.251 (talk) 05:44, 1 August 2009 (UTC)[reply]
Be sure to read this criticism of Kanazawa's ""Beautiful parents have more daughters..." paper. Based on my understanding, his paper is quite flawed and I haven't noticed a quality response to these criticisms, therefore I am skeptical. And this coming from someone who is planning on attending graduate school for evolutionary psychology, so it's not as though I am dismissive of the entire evopsyc subfield.--droptone (talk) 12:11, 5 August 2009 (UTC)[reply]
Water for both nuclear coolant and hot coffee?
Would it be possible for a nuclear power plant to do part of its cooling with potable water, remove that water before it went well above 100C, and use it to provide hot beverages or showers for staff? NeonMerlin08:23, 31 July 2009 (UTC)[reply]
well, maybe? :-) Withouth checking our reactor articles, I believe that they need heavy water in the reactor core, but that this water is used to heat ordinary water. This ordinary water drives a turbine and the "smoke" rising from nuclear powerplants are in fact the steam escaping. Nuclear powerplants then emit a lot of warm water to nearby rivers. So much that there's actually regulations in some countries to stop them from damaging the river from it. I would think that you could build a comfortable outdoor pool around this warm water, though I don't know what the typical temperature is. EverGreg (talk) 09:01, 31 July 2009 (UTC)[reply]
It seems a fair bit safer to let it heat way above 100 degrees, and use the hot pipes to heat up some water that has not been in touch with the reactor core. It is also cheaper to get clean potable water only for the coffees, not the whole operation, which is often done with ordinary river water.-KoolerStill (talk) 11:17, 31 July 2009 (UTC)[reply]
A more closely related concept is Combined heat and power, although it's more common to do this with small power stations built in residential areas. The water/steam coming out of the generator turbines is already used to preheat the water going into the reactor, it may be practicable to heat water for "domestic" use in this way. If you had a turbine trip, you might lose "domestic" water heating though. Taking water out of the steam generator part-way through wouldn't be allowed, because it would make the system needlessly complex and more prone to failure.
EverGreg, many or possibly most reactors don't use heavy water in the reactor. Candu does, but many other reactors use normal water, or carbon dioxide, or other fluids. Temperature limit is covered in the USA by the Clean Water Act, and as an aside, I've known people go swimming downstream of Beznau Nuclear Power Plant in Switzerland to enjoy the warm water. AlmostReadytoFly (talk) 11:20, 31 July 2009 (UTC)[reply]
Reuse of the waste heat from a power plant (for applications like heating) is cogeneration ("combined heat and power"). It's perfectly possible to heat whole districts of towns near powerplants (and this is done in Russia, for example), but the district has to be close to the plant for this to be efficient, and generally (even in Russia) people don't live that close to nuclear plants. You probably wouldn't want to drink the light-water secondary coolant, as it'll likely be contaminated with lubricants and maybe solvents left over from manufacturing (and if you're not heating the secondary coolant to boiling point, and staying at low-ish pressure, then you'd be drinking warm river water, which also isn't safe). There's no reason you couldn't pass the secondary coolant through a heat exchanger to heat regular treated potable water, although it's questionable if there are enough people in the plant to make it worth while (I can't see there's that much call for showering in a nuclear power plant, it's a fairly clean place). Now there is talk about small, sealed-unit, plug-and-play reactors being used in places like Alaska, so there may be more utility(sic) to CHP there than elsewhere (although the additional complexity of running and maintaining the district heating pipe system may again thwart real efficiencies). -- Finlay McWalter • Talk11:38, 31 July 2009 (UTC)[reply]
A course of drugs that can be taken before conception to reduce the risk of fetal abnormalities?
I'm not asking for medical advice, I'm asking for this is bullshit/not bullshit.
I live in China, the land of Chinese medicine... today I was talking to a former coworker and she informed me she was going to start trying for a baby at the end of the year. She further informed me that she would begin a 3 month course of pre-pregnancy drugs in October that ensures (or improves the chances) that your baby will be healthy.
I called bullshit on anything other than vitamins and a balanced diet, but she not only insisted it was legit, she insisted that it was "xi yao" (Western medicine -- as opposed to some random animal's foot, or some fungus from a back alley dumpster).
I am highly skeptical, but I defer to the collective wisdom of the reference desk.
Note that this woman is only 26 and has nothing wrong with her - we're not talking about fertility treatments for women who have proven difficulty conceiving.
Also note that China is notorious for prescribing anything for everything in order to inflate hospital bills...
That's a vitamin, though, which he accepted as a viable/non-bullshit way of improving the baby's health. (As should anyone!) -- Aeluwas (talk) 14:24, 31 July 2009 (UTC)[reply]
I'm sceptical too. I can't see how it would work. The man taking drugs before conception to improve the quality of sperm might make sense as a way to reduce the chance of chromosomal abnormalities, for example (I don't know of any such drugs, but I can't see why they couldn't exist). That wouldn't work for women though since the ova are all made before (or maybe shortly after) birth, so if they are faulty it is too late to do anything. Other than good nutrition and making sure you are in good health, I can't see how what you do before conception can have any effect on birth defects. --Tango (talk) 18:43, 31 July 2009 (UTC)[reply]
Total bullshit -- most drugs actually increase the risk of birth defects. As for folic acid, if she eats her veggies every single day, she'll have enough of that stuff to prevent complications. 98.234.126.251 (talk) 05:50, 1 August 2009 (UTC)[reply]
Is there any actual evidence she was not referring to vitamins? Did you actually ask her if she wasn't referring to vitamins? While from a medical context, it's probably not accurate to call vitamins drugs, such distinctions are not always made and in any case we don't even know if the words 'drugs' was used. And I'm guessing Mandarin Chinese was involved in this some where in the line so the potential for confusion is even greater. (Even worse perhaps if other dialects were involved.) For example, the compulsory fortification of bread with folic acid was widely described as mass medication here in NZ [27][28] and that's pure English. Vitamin supplementation, when supported by peer reviewed science and recommended by health experts are definitely a part of Western medicine. (When used in the alternative medicine field or without the support of peer reviewed science, as well as in things like Megavitamin therapy obviously that's a different matter.) Folic acid supplementation as has already been mentioned, is widely recommended for women planning to get pregnant, 98s comments not withstanding (you may be able to get sufficient levels without supplementation but clearly most people don't and I suspect knowing if you are or not is difficult without testing your blood level which is likely to be expensive, so just taking the supplements is probably simpler and less risky), and the benefits are AFAIK widely supported by peer reviewed science. There may be others, it's not something I'm that familiar with. In other words, unless it's clear that the lady involved to was not referring to vitamin supplementation, I don't see any evidence for any sort of contradiction here, just some confusion resulting perhaps from differing understanding of terminology. Nil Einne (talk) 07:49, 1 August 2009 (UTC)[reply]
OP here. Vitamins were brought up and dismissed by the claimant. My bilingual and equally skeptical wife was assisting in the discussion. There were no misunderstandings. This is China. You wouldn't believe the stuff they pass off as medicine here... 61.189.63.167 (talk) 11:13, 1 August 2009 (UTC)[reply]
In this case, this is worse than total bullshit, it's a deliberate scam on the part of some filthy bastard of a doctor who's trying to make some extra bucks off of that Chinese woman while putting her future baby's health at serious risk. As stated before, vitamin supplements (especially folic acid) are the only drugs she should be taking before and during pregnancy. Anything else will only hurt her chances of having a healthy baby. (I hope that the filthy bastard that I'm talking about ends up in prison where the other inmates will beat him up every single day.) 98.234.126.251 (talk) 19:45, 1 August 2009 (UTC)[reply]
While I was wrong about the vitamins part, I still don't see any reason to presume he/she's actually giving her some drugs. I'm guessing much of the stuff passed off as medicine in China includes vitamins or even sugar pills as well as of course herbal remedies and the like. Just because the doctor claims it's 'Western medicine' doesn't mean it is. Think of it this way, if the doctor has a choice between real drugs, which probably costs a bit, and something else which is far cheaper, which do you think they would choose? I'm not saying that what he/she's giving her is harmless or that the scam is acceptable, just that I see no reason to presume he/she's actually giving some drug Nil Einne (talk) 18:12, 2 August 2009 (UTC)[reply]
Many so-called "herbal remedies" can also be very harmful to pregnant women / unborn children. It don't have to be "Western medicine" to cause great harm this way. Plus, "herbal remedies" in general don't get FDA certification, so they can be downright poisonous even to people who are not pregnant. So in fact the "herbal remedies" scenario could be even worse. 98.234.126.251 (talk) 06:17, 3 August 2009 (UTC)[reply]
Well that's a different issue. Your earlier post seemed to suggest you believed she was being prescribed random drugs to me. Regardless though, you're right that they can be. You're also right they're not tested or regulated, although the FDA part is irrelevant, since nothing in China needs FDA certification. However, the vast majority do very little, which is one of the reason's why they're mostly bull. It's worth remembering that many of the herbal remedies are just stuff people eat every day (or at least on occasion, especially in somewhere like China), perhaps somewhat concentrated but often not really that different, other stuff is probably most inert (e.g. bone). That means they often do very little, which can be a good and a bad thing (bad if you want them to do something, good in that they don't do any harm). Personally I don't go hear that shit, but the point remains, taking random herbal remedies is a lot less likely to cause major harm then taking random prescription drugs (which have been tested and are known to have a significant effect). One thing to bear in mind is that's it's not always entirely clear who is fooling who. It's not necessarily the case that this doctor has made this shit up. They could just as well have gotten it from someone else. They may genuinely believe it's beneficial, or they may just not care. Obviously as the doctor who is prescribing it, they have a great responsibility to make sure what they are prescribing is likely to be beneficial and that this is supported by the available evidence which they are failing to do. But this doesn't mean they themselves are perpetuating a hoax on purpose. We just don't know who is doing what from the available evidence, nor do we even know what is being prescribed. P.S. Just to be clear, I'm not denying that herbal remedies can and do cause harm. They do and personally I believe they need far greater regulation, but that's neither here nor there. And just to repeat again, I'm not defending the doctor's actions, simply pointing out that as things stand, we don't really know what's going on here. Nil Einne (talk) 16:00, 5 August 2009 (UTC)[reply]
A doctor "genuinely believing it's beneficial"? I don't think so -- a real doctor would know better than to prescribe some untested drugs / herbal remedies / whatever to a woman who's planning to become pregnant! It definitely sounds like a scam to me. 98.234.126.251 (talk) 03:32, 6 August 2009 (UTC)[reply]
Identification of an NZ tree
I frequently visited the Wairarapa in my childhood days and would always see trees like this in little clumps by the side of the road, but was never sure exactly what kind of tree they were. For some reason I always got the impression that they weren't endemic to NZ. Is anyone able to help? AustralianMelodrama (talk) 11:46, 31 July 2009 (UTC)[reply]
What is that condition called when you are not at all hungry when you first wake up? As if you will puke even if you swallow water? Some of my friends wake up hungry and can't wait to eat while I feel like my stomach cannot deal with processing anything (maybe a few sips of coffee). It almost feels like heartburn but not really. I have been like this all my life. --Reticuli88 (talk) 14:34, 31 July 2009 (UTC)[reply]
Asking us to name your condition sounds like a request for diagnosis; and we cannot give medical advice (even if your condition is mild, you are still asking for a diagnosis). See our medical disclaimer. Nimur (talk) 15:35, 31 July 2009 (UTC)[reply]
I doubt it has a name. I think it's just something with the biological clock. Some people are hungrier when they get up, some aren't. You say that yourself when you say "some of your friends" are like this, implying some aren't. It's just like some people are "morning people" and some aren't; some function well, all bright and bushy tailed, int he morning, some don't.
As an aside, if you have a doctor but because of some autism spectrum disorder can't verbalize things well, write what you just wrote down and give it to them. (Something that should probably be inaour medical disclaimer as a suggestion. Because I have experience in that area, I wouldn't be surprised if there are at least a few people with that who come on here because they want to be able to tell the doctor "I think I have 'x', rather than verbalizing their symptoms and engaging in a discussion. Writing your symptoms down is the best way to go there, not asking random strangers to say something that might be wrong and might lead a doctor downt he wrong path.)209.244.30.221 (talk) 15:56, 31 July 2009 (UTC)[reply]
It's called morning sickness, heh heh (sorry). No, it's more commonly called "morning anorexia", and there are lots of possible causes, including nighttime overeating or alcoholism -- but some people are just that way all the time with no apparent health impacts. Looie496 (talk) 17:03, 31 July 2009 (UTC)[reply]
In weight loss programs some members, when told to start the day with a healthy breakfast, reply that they never eat breakfast. The trainer may point out they in fact they ate supper at 7 pm then breakfast at 11 pm while bingeing in front of the TV set: crunchy snacks, ice cream, cookies, extra helpings of supper leftovers. After 8 hours of inactivity during the night, that could explain the lack of appetite at breakfast. Edison (talk) 18:45, 31 July 2009 (UTC)[reply]
WP:OR: I know (from personal experience, don't ask) that severe sleep deprivation (as in cramming for exams all night long) can lead to a lack of appetite, nausea, and other symptoms similar to "morning sickness". I wonder if it's related to some kind of hormonal effect... 98.234.126.251 (talk) 06:46, 1 August 2009 (UTC)[reply]
Accoriding to our article on History of time in the United States, the federal government did not institute DST from 1945-1966, though it says that many states and localities did have their own versions. It does not, however, specifically mention Boston. There are some sources in our article, specifically book sources, which may give you more information and places to research. --Jayron3217:17, 31 July 2009 (UTC)[reply]
Old newspapers would be a good place to check on this. By going to a large reference library, or perhaps a smaller library if it's in or near Boston, it should be possible to find copies of the Boston Globe from 1964 (probably on microfilm or scanned into an online format). In the parts of the US and Canada that used DST at that time, it normally ran from the last Sunday in April to the last Sunday in October. So I would suggest looking at the newspapers for Saturday and Sunday, April 25 and 26, 1964, and October 24 and 25, 1964. If DST was in use, you would expect at least a short note on the front page reminding people to change their clocks; if not, there might be articles or letters-to-the-editor talking about how other places used DST and Boston did not. --Anonymous, 00:47 UTC, August 7, 2009.
Hmm, interesting question. My best guess would be the hydra, a microscopic coelentrate. It has probably less than 100, but counting is tricky, because there is evidence that in hydras the neuron phenotype is plastic -- that is, cells can switch between functioning as neurons and functioning in other ways. The lowest actual count I know is for the roundworm C. elegans, which in the hermaphrodite form has exactly 302 neurons. Looie496 (talk) 16:54, 31 July 2009 (UTC)[reply]
Exactly 302 neurons sounds very suspicious. I just checked the source cited for that line, Collective dynamics of 'small-world' networks. There is no mention whatsoever of "302 neurons" in the full article (not even for an individual specimen), let alone that this is valid for all C. elegans. It seems strange for that kind of consistency across all individuals of C. elegans - can anybody find a source which explores this in more detailed? In the mean-time, I tagged the statistic as unverified in our article. Nimur (talk) 19:51, 31 July 2009 (UTC)[reply]
One of the things that make C. elegans so useful in study of growth and development is that it has a specific number of cells (959 total cells, including 302 neurons[29], 111 muscle cells, 34 intestinal cells, and 213 epidermal cells [30]) each of which has a specific and well-characterized lineage. It's a degree of precision uncharacteristic of biology, but thoroughly cool, I think. – ClockworkSoul23:21, 31 July 2009 (UTC)[reply]
Awesome - thanks for clearing up the detail, and I'm glad to see that somebody added a good source to the C. Elegans article! Nimur (talk) 05:24, 1 August 2009 (UTC)[reply]
I recently had to make a presentation for Biology about Genetic Engineering and recombinant DNA. In it, I mentioned that vaccines can have either dead or inactive viruses, and the teacher corrected me by saying that they only have "dead" viruses. I recently looked it up on Wikipedia, and found that they can be of both types. Can somebody please explain this to me? —Preceding unsigned comment added by 190.95.97.35 (talk) 16:38, 31 July 2009 (UTC)[reply]
There are many different ways of making viral vaccines, and if you read our article on Vaccine, especially the "types" section, you will find there are all sorts of vaccine types, from completely dead to inactivated to fully living and functional. Indeed, the very first vaccine from Edward Jenner contained fully functioning cow pox viruses, which as a less deadly cousin of small pox, worked quite well as a vaccine (the name vaccine even comes from the latin for cow, vacca). Not that Jenner even knew what a virus was in the 1770's, but it still is true that there are a wide variety of ways a vaccine is made. If you teacher insists that there are not, they are mistaken. Don't look to this as an opportunity to "show them up"... Just be silently content with the knowledge that you are right. If you wish, you can direct your teacher to, say, any introductory High School Biology textbook written in the past 50 years, which will explain the way different methods of vaccination work. --Jayron3217:12, 31 July 2009 (UTC)[reply]
As a teacher myself, I believe very strongly that students should feel free to correct teachers when they are wrong. You shouldn't do it in a way that is offensive or that obstructs the flow of a lesson, but when your own understanding conflicts with that of a teacher, it helps everybody to make that clear. Not all teachers react well to being corrected, but the good ones do. Looie496 (talk) 18:09, 31 July 2009 (UTC)[reply]
The majority of viral vaccines are live attenuated versions. The Salk polio vaccine, some influenza vaccines, and Hepatitis B vaccine are notable exceptions.
I have a followup question: What do we mean by "dead" and "killed" and "live" in the context of a virus anyway? They are basically non-living things - so are we talking about preventing them from inserting themselves into our cells so they don't get replicated? What is the distinction between "inactivated" and "dead" anyway? What exactly are we doing to them that's different in the two cases? I understand that our immune system can be trained to recognise little bits of a virus - and that this is enough to result in the real virus being recognised too...so clearly chopping up into little bits is one kind of "dead". SteveBaker (talk) 18:09, 31 July 2009 (UTC)[reply]
"Dead/killed" in this context means that the material previously contained viable virions (complete virus particles), capable of infection and reproduction. This material has been treated, usually chemically, to render the virions non-viable, incapable of replication. There is no distinction between "dead" and "inactivated". Axl¤[Talk]18:49, 31 July 2009 (UTC)[reply]
Well, that's what I thought - in which case our OP and the teacher are both right (or is that both wrong?)...anyway, they agree. SteveBaker (talk) 19:35, 31 July 2009 (UTC)[reply]
However, in the context of vaccines, "inactive" could also mean "attenuated" rather than completely dead; the student's point was that there are multiple ways to make a vaccine, and the teacher seemed to (incorrectly) state that there was only one... --Jayron3219:48, 31 July 2009 (UTC)[reply]
According to a UK government site: "The Health Protection Agency estimates there were 110,000 new cases of swine flu in England last week. This is only slightly up from 100,000 the previous week." - people who recover from the disease generally recover in about three weeks - so there are probably around 300,000 cases on any given day. The population of the UK is around 60 million - so the proportion is around one in every 200 people. That's a very rough estimate though - the number of cases is an estimate and the duration of the disease varies quite wildly - so you have one estimate multiplied by another...and that's never good for data reliability. Part of the problem is that in some people, the symptoms are so mild that they may be missed completely - or mistaken for a simple cold or something. SteveBaker (talk) 00:45, 1 August 2009 (UTC)[reply]
Nobody knows, is the answer to your question. The swine flu is new and being tracked. Ordinary flu has been around for ages (although different strains of it) and nobody bothers to keep count, as it is not notifiable. In fact many people (or their doctors) diagnose "flu" without doing any tests to establish the strain, then may or may not prescribe Tamiflu. So a great number of flu cases are not recorded anywhere to be counted. There are figures on annual deaths from the flu, but these are usually not reported. Only an unusual strain that catches the public/media imagination gets reported. Now many more people are being tested, to eliminate swine flu, so there may be figures on how many are "passing" the tests, but I've not seen any reported. Many still are not being tested, so they'd not be accurate anyway. - KoolerStill (talk) 15:37, 1 August 2009 (UTC)[reply]
Indeed. I don't know about other countries, but the UK doesn't even try and identify strains. It doesn't even try and identify if the patient is actually ill... --Tango (talk) 15:44, 1 August 2009 (UTC)[reply]
As of a month ago in Australia, at least 40% of influenza A cases were swine flu, and that proportion was expected to rise to 60 to 70%, according to the story. From what I recall (though I can't find references to hand) more recent reports suggest that the majority of flu cases in Australia at the moment are swine flu. --Robert Merkel (talk) 07:33, 4 August 2009 (UTC)[reply]
great-grandfather
So you have a maternal grandfather, and a paternal grandfather (2). But how do you distinguish between your four great-grandfathers? —Preceding unsigned comment added by 86.162.105.200 (talk) 21:50, 31 July 2009 (UTC)[reply]
I would just say "My mother's maternal grandfather" vs. "My mother's paternal grandfather" vs. My father's maternal grandfather" etc. etc. --Jayron3222:26, 31 July 2009 (UTC)[reply]
You might also consider asking at the Language Desk. This is one shortcoming of English - we have non-descriptive terms for various relatives. Many other languages have specialized terms for different types of cousins, uncles, aunts, grandparents etc. It seems likely that they might follow suit with great grandparents. Nimur (talk) 05:56, 1 August 2009 (UTC)[reply]
What one views as a shortcoming the other views as a blessing. OR We often joke that our family tree is best represented in 3D. We have cousins that are also half-brothers/ sisters, great aunts that were also grandmothers etc. I assume with more special expressions we'd just resort to "relative" for everyone :-) 71.236.26.74 (talk) 07:18, 1 August 2009 (UTC)[reply]
I agree that it's more of a blessing than a shortcoming... we have relatively simple terms for describing kinship; I do not envy languages that divide things up further than we do! I have never had a need so far in life to distinguish between various great-grandparents on a regular basis. --98.217.14.211 (talk) 14:20, 1 August 2009 (UTC)[reply]
I agree, it took me long enough to get to grips with the rules for "Xth cousin Y times removed", if I had to distinguish between parallel cousins and cross cousins as well I doubt I would ever have got it! I don't want to have a take a module at university on the naming of cousins... --Tango (talk) 15:48, 1 August 2009 (UTC)[reply]
But those are rather distant relations. Part of the difference between English and some other languages, e.g. most? Chinese dialects is in the clear difference between far closer relatives. And while I'm not extremely familiar with the Chinese system, what I do know (mostly relating to Cantonese) suggests to me the system is not necessarily infinitely more complex or difficult to understand but often follows a clear pattern that isn't that hard to understand if you know it. E.g. the numbering of aunts and uncles (although I don't know if that's commonly done in ordinary speech). [31](warning: has sounds). And I would say there are clear examples where the English system is a clear shortcoming, it's not that you may ask someone or at least wonder whether they mean grandparents, cousins, uncles/aunties on their father or mother's side. Or in the case of cousin's it may be whether you are referring to first cousins or other counsins (although that is less of a problem since it's rare, at least in my experience for second cousins to come up). Indeed in some cases the English system can IMHO be more confusing (frankly I've never understood the cousin removed part). English even often lacks the norm of expressing a clear difference between older siblings and younger siblings which I believe is quite common in a number of other languages and can also sometimes be confusing, particularly at a younger age (some people may make the difference clear, particularly when they think it matters, but it's not uncommon to hear of a brother or sister without being clear of the age relationship when the age relationship may be considered of significance). (Of course some languages have other problems of their own, e.g. Malay has a term for older sister, older brother and younger sibling. The distinction between male and female basically is made by adding male or female and of course is often not done in ordinary discourse. I guess some may think of this as an advantage. ) The problem 71 is referring to relates more to the pedigree collapse caused by a close degree of consanguinity in relationships that was quite common in some societies, particularly royal ones, but was far less common in others. The degree of course varies a fair amount, for example first cousin couples are not uncommon in some cultures by highly taboo in others. And of course, the changing nature of relationships nowadays means that many of the traditional terms break down even in English, I suspect other languages with clearer distinctions may sometimes find it more difficult (or in some cases they may already have a term.) Nil Einne (talk) 18:06, 2 August 2009 (UTC)[reply]
That will work fine for the OP, who asked about great-grandfathers, by Sosas don't work for any ancestor, only levels of parentage. My sister and I have no Sosa number relation, for example. Matt Deres (talk) 16:05, 5 August 2009 (UTC)[reply]
At least in Swedish (and AFAIK also Danish and Norwegian), distinguishing between grandparents (and great-grandparents) is very simple. One word for "mum" is "mor", and the male equivalent is "far". The maternal grandparents then are "mormor" and "morfar", and the paternal ones "farmor" and "farfar". Then you can just go on to specify "mormors far" (the s is formally the genitive), "farfars mor" or even "farmors farfars morfars mor"... 85.228.22.219 (talk) 16:39, 5 August 2009 (UTC)[reply]
August 1
Swine flu
Is the swine flu wrongly named ??? I read in wiki article that the present strain of H1N1 virus is different from that present in pigs.Infact it says it first passed on from a man to the pig. Also what is so special about swine flu ,that it is hitting the news almost everyday???Is it not just like any other viral infection or a flu??pl clarify thanks.117.193.132.197 (talk) 07:22, 1 August 2009 (UTC)[reply]
The articles "Swine influenza" and "2009 flu pandemic" have the answers to your questions. "Swine influenza" is so named because the virus is endemic in pigs. It is thought that certain mutations ("reassortment") have caused a strain of swine influenza to become more readily transmissible among humans. Axl ¤ [Talk]09:26, 1 August 2009 (UTC)[reply]
It certainly is a poor choice of name, because it causes people to behave totally illogically. See 2009 swine flu outbreak actions concerning pigs...Every pig in Egypt was slaughtered in an effort to prevent a disease transmission mechanism that simply doesn't exist. Khanzir was locked away from curious public for the same reason. Sadly, we never seem to learn the lesson that naming things inappropriately causes panicky people to initiate useless and often costly responses to serious problems. SteveBaker (talk) 18:19, 2 August 2009 (UTC)[reply]
In the case of Egypt, they actually had ulterior motives to kill the pigs: since the only consumers of pork in Egypt are "infidels", they killed all the pigs to collectively punish the "infidels" (especially the Coptic Christian community) and force them against their will to comply with the shariah law regarding pork consumption. The so-called "swine flu" and the fear of contagion was only an excuse they needed to present to the so-called "international community" to justify these actions. 98.234.126.251 (talk) 05:23, 3 August 2009 (UTC)[reply]
My point exactly -- if it wasn't called "swine flu" then they wouldn't have that excuse to kill the pigs. If we called it "Mexican flu", though, then that would give them an excuse to arrest/isolate/deport (or even lynch) any Mexicans who happen to be in Egypt -- and they would've done that, especially since most Mexicans are Catholic. 98.234.126.251 (talk) 02:03, 4 August 2009 (UTC)[reply]
Uncertainty principle
I have just started to tackle on this subject.
The part of explanation which seems most easy to understand (for me) is Uncertainty principle#Derivations#Wave mechanics.
This question is from there.
It says:
If the wave extends over a region of size L and the wavelength is approximately λ, the number of cycles in the region is approximately L / λ. The inverse of the wavelength can be changed by about 1 / L without changing the number of cycles in the region by a full unit, and this is approximately the uncertainty in the inverse of the wavelength,
And I think the inverse of the wavelength can be changed more exactly by about , not by 1 / L, without changing the number of cycles in the region by a full unit.
If so,
and multiplying by h, and identifying , and identifying ,
.
Does that not mean if lamda is enough large, uncertaity becomes small?
Like sushi (talk) 11:22, 1 August 2009 (UTC)[reply]
No. Consider the case of as large as possible, i.e., . In order to change that situation by one whole cycle within length , i.e. to go from 0 cycles in length to 1 cycle in length , you have to go from all the way down to , which would result in . Red Act (talk) 19:32, 1 August 2009 (UTC)[reply]
It has become clear. No matter it is from what number of cycles to the next mumber of cycle, , because are n/L and n+1/L.
One more question. The above process includes changing the inverse of the wavelength without changing the number of cycles in the region by a full unit. If we are to measure only one particle, there seem to be no way of knowing the number of cycles in the region, on the other hand, if we are to measure a bunch of particles, capturing the shape of the wave seems possible, and therefore the wavelength and position.
Power line tennis raquets?Power line tennis raquets?
What are these things? What do they do? I see them occasionally on power lines. If it matters, this is in the US, Vermont more specifically. Dismas|(talk)13:05, 1 August 2009 (UTC)[reply]
I'm not 100% convinced they are tensioners, especially the second image - the device seems to be hanging on the wire, and not strongly attached in the way one would expect a tensioner.
(However if they are tensioners) then the article Overhead lines may be a better choice - they are common on electric railways - I've attached images of two on railway electrical lines - although a slightly different design - they should give a good idea of how they work and what they are doing :—Preceding unsigned comment added by 83.100.250.79 (talk) 17:20, 1 August 2009 (UTC)[reply]
I would speculate that the device in the original photos is likely a cable shortener and the cable is possibly a telephone cable rather than electric. This would allow the telephone company to intentionally insert some extra length into that segment of cable which could be used if the cable later needs to be rerouted, possibly due to anticipated relocation of the utility poles. This would avoid the need to splice in a new length of cable, which is no trivial task. -- Tcncv (talk) 21:11, 1 August 2009 (UTC)[reply]
I've seen some of these too, they usually have a few turns of cable wrapped around them and are strapped to the line. Tcncv sounds right to me, in the case of a downed power line they might need the extra length. Presumably, when the company is hanging (laying?) power lines, they use more cable than they expect to need (better than using less than is needed). And it's probably more economical to just roll up the extra cable and have it be usable later than just cut it off and be useless. ZS01:17, 2 August 2009 (UTC)[reply]
The two images that I posted are of the same device. They're just taken from two different angles. And yes, it is about 2-3 inches below the line that it's attached to. And we do have four new houses potentially going up on our road (as much as it bothers me to say it), so they may have put in extra cable for them. Dismas|(talk)02:08, 2 August 2009 (UTC)[reply]
The cable needs to be longer than its path anyway so it can be raised and lowered for maintenance purposes. But the fact that it is limited to a minimum radius bend suggests fibre optics to me. —Preceding unsigned comment added by 92.19.119.89 (talk) 21:58, 2 August 2009 (UTC)[reply]
Power lines are generally one conductor per wire, so it is straightforward to jumper in an extension to raise them for house moving. Phone cables may be multiple conductor (other than ancient rural party lines) so splicing would be very time consuming, and spooling several extra feet of cable might be sensible. Edison (talk) 00:50, 3 August 2009 (UTC)[reply]
In my (rural) neighborhood they appear in pairs, and there is a loop of cable that goes from one, to the other, then back along the primary line -- kind of like a pulley sytem. I've observed the local cable company working on them, so assumed they are television cable trunk lines -- they're noticeably heavier than the runs that to go the houses. They're used to store extra length of cable, as mentioned above, anywhere from 50 to a couple hundred feet.
Perhaps it IS a pulley system? where they expect to be shortly stringing additional wires? a pulley system that runs along an already installed wire, like a flying fox, would certainly make it easier to string the next new wire. Once they reach a pole, they'd have to transfer it to the next section. (This is not even OR, it's a WAG). - KoolerStill (talk) 11:07, 3 August 2009 (UTC)[reply]
image processing help.. required.
i have collected data of a gas turbine flame(at different equivalence ratio) using image processing toolbox of matlab .i understand that i have to use neural network toolbox to optimize the process.if any one could give me some ideaabout what could be optimized and how it could be done in neural network toolbox.
sam
220.225.98.251 (talk) —Preceding undated comment added 14:07, 1 August 2009 (UTC).[reply]
It's very important to use the word "optimize" carefully. Take a look at optimization - there's a lot of subsets there. MATLAB has very powerful tools for the mathematical operation of optimization, which means solving for the optimal numerical solution. If the built-in MATLAB tools are insufficient, the CVX tool ("CVX: Matlab Software for Disciplined Convex Programming") is a common add-on. If you are using the word "optimization" to mean that you want to "improve the efficiency" or speed up the process, then you need to explain your task a little better. I also recommend that you do not use the term "optimize" when referring to general improvements to efficiency, because (as you are working with MATLAB, a numerical computation environment), "optimization" has a very specific mathematical meaning here. Nimur (talk) 07:16, 2 August 2009 (UTC)[reply]
I live in Northern Nevada where summer here is 100F each day. In the morning and sometimes all day these things rest near my bug zapper. They're really sluggish to get them moving again and have to spend several minutes warming up before they can fly. I don't know if that helps determine things. Are you ready for IPv6? (talk) 15:51, 1 August 2009 (UTC)[reply]
I bought a pint bottle of orange juice yesterday morning, opened it up and drank about a quarter of it directly from the bottle, which surely got some saliva and germs into it. I screwed the cap back on with the idea of taking it to work and finishing it there, but forgot about it, so it's been sitting at home at room temperature (maybe in the 70's during the day, it's not terribly hot here) for the past 24 hours or so. Taking a sniff of it, it smells ok. Is it likely to be teeming with dangerous pathogens by now despite that? I guess this is really a general question of whether food spoils to the point of unsafe-ness even without starting to smell or taste bad. Thanks. 67.117.147.249 (talk) 18:25, 1 August 2009 (UTC)[reply]
We can't really give definitive advice as to safety - but orange juice is fairly acidic, and won't go off rapidly, (also if your own saliva was that full of pathogens you'd probably be dead already :) ), one day is ok, I'd put it back in the fridge, warm orange juice is not that tasty.
In a general case it depends on the food, some keep better than others, yoghurt is something I regularly eat past the sell by date since it's a foodstuff that by 'design' is supposed to keep.
Obviously I'm statisically insignificant, but I regularly drink orange juice, straight from the carton, and leave it in my bedroom (which tends to have closed doors and windows, so gets warm and humid) for three or four days before it gets finished. Interpret that information as you like. 90.195.179.49 (talk) 21:50, 1 August 2009 (UTC)[reply]
Warm orange juice, especially fresh-squeezed, will ferment pretty quickly. It isn't harmful to drink that way, but the loss of sugar and increase in acidity make it pretty unpleasant, to me at least. Looie496 (talk) 21:53, 1 August 2009 (UTC)[reply]
Well I've had freshly squeezed OJ from a warm airport terminal in Spain several times and I just can't help but sink the whole plastic cup in one it is so darn palatable :-). Orgasmic is a better word, but maybe it's just me. --Mark PEA (talk) 23:44, 1 August 2009 (UTC)[reply]
Crosswind landing
What's the HIGHEST crosswind velocity in which a Beech Queen Air can land? (Assume the worst case, that the wind is blowing at RIGHT ANGLES to the ONLY available runway. Also, if it matters, assume that the runway is wet but NOT icy, and that the pilot has more than 10 years' worth of experience, and also that she's a firm believer in using the sideslip method rather than the crabbing method for landing.) Thanks in advance! 98.234.126.251 (talk) 19:06, 1 August 2009 (UTC)[reply]
In the crosswind chart of the FAA’s Airplane Flying Handbook, page 8-16, a crosswind landing in a direct crosswind is in the “danger zone” at wind velocities above 15MPH.[32] But I think that might just be a sample crosswind chart, that doesn't really pertain to any specific aircraft. According to the same page, in airplanes certified after May 3, 1962, the FAA requires the demonstrated crosswind velocity of an airplane to be included on a placard in the airplane. Does the Beech Queen Air in question not have such a placard? Red Act (talk) 20:17, 1 August 2009 (UTC)[reply]
It should -- unfortunately, I'm not a professional pilot and have never been in the cockpit of a Queen Air (or, indeed, in the cockpit of any twin-engine airplane). I'm just a petroleum chemist who's also a part-time writer of detective fiction, and I need this info for a short story that I'm in the process of writing. I think I'll just go with 15 knots as the maximum crosswind velocity. Thanks, and clear skies to you! 98.234.126.251 (talk) 21:23, 1 August 2009 (UTC)[reply]
You should be aware that these figures are always pretty conservative. A skilled pilot in an emergency situation will mostly succeed at quite a bit above the rated figures -- it's scary as hell though. I was in a small plane once that landed with the nose pointed upwind at what seemed like 45 degrees, and it was a white-knuckle experience for me, although the pilot didn't seem fazed. (It also matters a lot whether the wind is constant or gusty.) Looie496 (talk) 21:41, 1 August 2009 (UTC)[reply]
So, a pilot with more than 10 years' worth of experience might be able to land a light twin (like the Queen Air) in a steady 20-knot crosswind? What do you think? 98.234.126.251 (talk) 21:48, 1 August 2009 (UTC)[reply]
For the sake of realism, also keep in mind that the tower might not allow a landing outside of the conservatively-estimated limits. Planes are regularly delayed or redirected to alternate landing sites due to bad weather. Nimur (talk) 22:25, 1 August 2009 (UTC)[reply]
True enough, but the field in question is a tiny airstrip in northern Canada and doesn't have a control tower. Also, the plane in question is critically low on fuel (about 1/2 hour's worth of fuel remaining) and cannot reach any alternate landing site. 98.234.126.251 (talk) 22:30, 1 August 2009 (UTC)[reply]
Well according to this the stall speed of a Queen 88 is 70 knots. According to the Canada Flight Supplement "Aircraft of United States manufature are designed to withstand groundlooping tendencies on landing in 90-degree cross-winds up to a velocity equal to 0.2 (20 per cent) of their stalling speed." and points out the owners manual will have the information. So for the 88 it's 0.2 x 70 = 14 kts. Not much wind needed to cause a problem. There is some more about it here. Also if your pilot is landing anywhere but (for example) Rankin Inlet or Churchill, Manitoba, then the runway might be gravel and the wetness component for a small aircraft will not be as bad as landing on a paved strip or for a larger aircraft. The airstrip won't have a tower but will probably have a Community Airport Radio Station or a Flight Service Station, who can give the winds and altimeter setting but can't deny or permit the landing. The pilot is in command and they make the choice. Enter CambridgeBayWeather,waits for audience applause,not a sausage03:03, 2 August 2009 (UTC)[reply]
Thank you very much, CambridgeBayWeather, this was very helpful of you. {**Loud applause**} This pretty much confirms the info I have so far. (BTW, I think I'll have my pilot land her plane at Coral Harbor (I know, that's technically not on the mainland), if it matters.) Thanks again, and clear skies to you! :-) 98.234.126.251 (talk) 05:34, 3 August 2009 (UTC)[reply]
The deafening silence is just everyone holding their breath watching the Queen coming in. They don't want to add to the gusts by breathing. -KoolerStill (talk) 16:02, 2 August 2009 (UTC)[reply]
Wow! That's suitable for publication in a mass-market suspense-thriller novel! Note that including the above theatric scene-building element in the novel may require licensing under GFDL... Nimur (talk) 16:38, 2 August 2009 (UTC)[reply]
Tin chloride for noble metal detection
SnCl2 is used to detect traces of noble metals in solutions. For example, it give us a purple color, if solution contains gold (AuCl3). Can anybody write the equations of reaction between tin chloride and gold chloride in solution and the reactions of tin chloride when it is used to detect platinum and palladium. Renaldas Kanarskas (talk) 19:09, 1 August 2009 (UTC)[reply]
I think that the overall equation of the reaction between SnCl2 and AuCl3 is as follows:
3SnCl2 + 2AuCl3 = 3SnCl4 +2Au
or in other words it's a straightforward redox reaction. As for the second part, I can't remember the exact equations off the top of my head, but I think that in those reactions SnCl2 also reduces the platinum / palladium ions to the metal while itself picking up 2 extra chlorines to form SnCl4. FWiW 98.234.126.251 (talk) 19:35, 1 August 2009 (UTC)[reply]
By the way, it could be Indian — this picture was taken by the same photographer at the same zoo. However, the two photos were taken over a year apart, so they're not necessarily the same bird. Nyttend (talk) 20:10, 1 August 2009 (UTC)[reply]
Hi, I took both the pictures under discussion. They were in fact taken on the same day because I've only been to Paignton Zoo once ever, in July 2003 (a look at the Image Description Page for both pictures confirms that). Sorry, but I didn't know at the time what species I was looking at and have no way of now finding out (short of posting the pictures to the zoo, which someone else is welcome to do). - Adrian Pingstone (talk) 20:55, 1 August 2009 (UTC)[reply]
My apology — I misread the upload dates as the dates when the photos were taken! Arpingstone, would it be reasonable to say that it's the same bird? It appears to me that the Indian species has a blue head and the Green species a green head (hardly a surprise :-), so if these are the same bird, the photo shown here is Indian. Nyttend (talk) 22:08, 1 August 2009 (UTC)[reply]
I'm sorry to be so unhelpful but I can't remember how many peacocks the zoo had (it was five years ago). Therefore it's not possible to say that the pictures show the same bird - Adrian Pingstone (talk) 22:26, 1 August 2009 (UTC)[reply]
Not surprised that you can't remember — how many little details do I remember from five years ago? Thanks for your help! To get back to the original question — can anyone identify the bird from behind? Nyttend (talk) 23:06, 1 August 2009 (UTC)[reply]
I sent a note to Paignton's inquiry email address, and just a few minutes ago received a reply: "That is an Indian Blue Peafowl." Thanks for the help! Nyttend (talk) 14:08, 3 August 2009 (UTC)[reply]
More specifically, it's the toroidallens that focuses the incoming light from the target area onto the photocell of an optical proximity fuze. The way it works is when the photocell "sees" the shadow from the target, the drop in current activates an electric circuit that sets off the fuze and makes the bomb explode. 98.234.126.251 (talk) 23:58, 1 August 2009 (UTC)[reply]
Have you got any source or evidence for that please, apart from just guessing after reading the proximity fuze article which I had also read? 78.147.244.14 (talk) 14:12, 2 August 2009 (UTC)[reply]
I've heard that the DNA of humans diverged from that of clowns much more recently than with other primates. Is that the case? If so, around what time did human and clown DNA begin to diverge, and is it possible that a human/clown hybrid could ever be produced?--99.251.239.89 (talk) 00:11, 2 August 2009 (UTC)[reply]
My brother was a clown in the Ringling Bros. and Barnum & Bailey Circus for a while when he was in his 20’s, and now he has an office job and is more than half way through getting an MBA. So my brother appears to be some sort of clown/human hybrid. So hybridization definitely is possible. Red Act (talk) 01:18, 2 August 2009 (UTC)[reply]
My brother has produced an offspring, actually, with a fully-human female. It’s too early to tell the extent to which the offspring will exhibit clown vs. human phenotypes. Red Act (talk) 15:19, 2 August 2009 (UTC)[reply]
Guys, we have no idea about the sincerity of the original poster, but it's best practice not to start making joke answers until the question has been correctly answered. (See the Content and Tone guidelines). To the original poster - if there is any confusion at all, let's clear it up. Clowns are comic performers, but they are genetically human; there is no genetic divergence. Nimur (talk) 16:28, 2 August 2009 (UTC)[reply]
Sorry for my lack of humor, but if we all start clowning around on the Reference Desk, things will rapidly devolve from "helpful resource" into "another internet forum full of idiots." Nimur (talk) 16:29, 2 August 2009 (UTC)[reply]
I figured there was next to no chance that this question wasn't a joke question. To the original poster – if this question wasn't intended as a joke, my apologies for not taking your question seriously. Red Act (talk) 17:09, 2 August 2009 (UTC)[reply]
Reliable sources should be provided for the claimed humanity of clowns. They do not, in general look or act like most humans. More clowns fit in a small car, for instance, than would be possible for normal humans. Edison (talk) 00:46, 3 August 2009 (UTC)[reply]
Good point. I would also like to know where mimes fit in. Are they clown-human hybrids or a separate species altogether? How many mimes can fit in a tiny car? – ClockworkSoul02:34, 3 August 2009 (UTC)[reply]
I dunno - the tangled sentence structures used in the simple-english article make it quite a bit harder to understand than the regular english version! SteveBaker (talk) 00:57, 3 August 2009 (UTC)[reply]
Calculating size of projected image
How do I calculate the size of image a projector can project, given the distance from the projector to the screen, and the focal length and f-stop of the projector's lens? I have a projector with F = 2.41 - 2.66 and f = 18.17 mm - 21.81 mm. Can I calculate the projected image size from these numbers or do I need more information? (the projector in question is the Acer P1266) Thanks in advance! — QuantumEleven12:32, 2 August 2009 (UTC)[reply]
The f-stop does not affect the image size, only its brightness. To calculate the image size you need to know the source (a DLP chip I believe) size S. Then image size S' = S x F/f. Your projector has a zoom lens that can optionally increase S' to 1.2 S'. Note: in some modes the whole DLP chip may not be active. Cuddlyable3 (talk) 13:06, 2 August 2009 (UTC)[reply]
Ah-ha - thank you! The data sheet does not give a source size, but it gives a throw ratio, which, according to this, is the ratio of screen width to distance. They give a throw ratio of 1.6 to 1.9 (via a zoom lens, I presume), but they quote a screen size of 62" (1.58 m) at 2 m distance, which gives a throw ratio of 1.27. What am I missing? — QuantumEleven21:58, 2 August 2009 (UTC)[reply]
Seeking a ray-diagram of a toroidal lens
Cannot find one of these on the internet anywhere. If you put a toroidal lens up to your eye and looked through it, would you get a wide-angle field of view like a crude fish-eye lens? The only picture I could find of a toroidal lens is here http://www.isuzuglass.com/g_p.html78.147.244.14 (talk) 14:23, 2 August 2009 (UTC)[reply]
Do you mean a full toroid (geometry), or just part of one (a section)
In the first case the effect is like that of a cylindrical lens off axis - but rotated about the centre line of the eyes view direction.
In the section case the lens will distort images so that the aspect ratio is not preserved since the curvatures are different. (plus other distortions ie a point source will have a non-circular image of confusion)
I think the page that the OP linked to is a translation, and so uses an unfamiliar term for what is better known as a truncated f-theta lens. The name means that the displacement of the scanned beam is the product of f (the focal length) and theta (the deflection angle of the beam). I found a picture of one here, from Melles Griot, and it has some nice ray diagrams. Apparently, the view through a non-truncated (i.e. round) F-theta lens is like that through a fish-eye lens but with less distortion. The "toroidal" lens that the OP mentioned, though, is designed for one-dimensional scanning so would have a uselessly small aperture in one direction. You would just see a bright line, I guess. --Heron (talk) 18:57, 2 August 2009 (UTC)[reply]
Just to add a little bit more - the page (possibly translated) mentions that the "toroidal lenses" are... "It is used in the equipment such as a laser printer, a fax or a copier that incorporates a printing mechanism of a scanning laser beam." - in my experience such lenses have curvature in one direction, and infinite or very large curvature in the other - if the laser beam has finite width the large curvature aspect (at right angles to the scan) might be used to get a smaller laser spot (this is a guess) - and would be a good match for the description "toroidal".
I was assuming that when "fish eye" was mentioned it meant "very wide angle" rather than the type of distortion .. my apologies about that..83.100.250.79 (talk) 19:17, 2 August 2009 (UTC)[reply]
Oh, wait. I've just read an earlier post by the OP and realised that he is not looking for an f-theta lens. He has read the proximity fuse article and wants to know what the "toroidal lens" mentioned there looked like. I think that the lens mentioned in that article is unrelated to the Isuzu "toroidal lens" that the OP found on the web. The proximity fuse lens was, possibly, actually doughnut-shaped. There's not much point in speculating on what you would see by looking through one of those, since they weren't designed to create an image. --Heron (talk) 19:04, 2 August 2009 (UTC)[reply]
Actually I think a toroidal lens (two radii of curvature, not a donot) of the type used in scanners/laser printers - would work to capture a plane of light (roughly) - though maybe a concave version would be better. I can't see a optical donut shaped lens having any use..83.100.250.79 (talk) 19:23, 2 August 2009 (UTC)[reply]
The plot thickens. I've just found evidence that the proximity fuse lens was actually a Perspex ring that formed part of the nose cone of the missile. It was curved around the axis of the missile (obviously) to give it a 360° view, but it was also curved at right angles to that to focus the light onto an internal photocell. Thus it was almost doughnut shaped, and not the sort of thing you would want to look through. --Heron (talk) 19:56, 2 August 2009 (UTC)[reply]
I found that too, but couldn't make 100% sense of it - to me it would seem sensible to have a conical mirror in the middle of the torus reflecting light from the edges (perpendicular to flight) down onto a photocell - possibly that's what it means when it says "and to have the focal axis at any point around the lens lie on a conical surface" - possibly this type of lens could be used to make a 360degree angle lens - I think the image would be projected onto a disc (ie a circle with a circular hole in the middle) - so with the conical mirror - it might be possible to make a 'fisheye' type wide angle lens - 83.100.250.79 (talk) 20:10, 2 August 2009 (UTC)[reply]
To the original questioner - it seems to me that technically a toroidal lens should be convex, however using the same principles a similar type of lens could be made that was concave - speaking from experience I know that some laser printer lens of this type (the scanning lens) are concave, so maybe it doesn't matter if the lens is concave or convex for it to be called a toroidal lens (as long as the general principle of different curvatures remains) - coupling this with the info. given above it looks like a toroidal lens might (in principle) have a fish-eye like effect - though only in the way the image is distorted (rather than having the 180 degree view that people like me associate with fish-eye lenses) I'm assuming that the term 'fish-eye' includes at least some widening of view angle, as well as a particular type of edge distortion.
Its the shape of the lens in an optical proximity fuze that I'm curious about. I imagine that it would focus the light from 360 degrees onto a small disk-shaped photocell. Perhaps it is shaped like an invercone on a light meter. 89.242.100.18 (talk) 22:48, 2 August 2009 (UTC)[reply]
I think quite possibly you're right - though I'm not sure that the invercone uses exactly the same principle - it appears to be opaque and use light scattering inside a almost torus shaped thing - I don't know exactly how an invercone works though.83.100.250.79 (talk) 00:16, 3 August 2009 (UTC)[reply]
Is it some textbook that you’re seeing the in? That does seem problematic. By the formula for integration by parts, those two integrals would be the same only if was the same before and after the process, which for an ideal gas, amounts to the temperature being the same before and after the process, which is not generally the case. Red Act (talk) 20:39, 2 August 2009 (UTC)[reply]
Lost in space during an EVA
What happens if during an EVA an astronaut floats off into space, beyond the reach of any mechanical arm? Is he or she doomed? It would be a horrible and drawn out way to go. Why do astronauts not seem to have safety lines connecting them to the airlock door so that they cannot spin off into space? 78.147.244.14 (talk) 15:16, 2 August 2009 (UTC)[reply]
I think they usually are tethered to the craft. You sometimes see them removing their tether and attaching it to a different bit as they move around. --Tango (talk) 15:54, 2 August 2009 (UTC)[reply]
Since the Challenger accident, NASA has done risk-reduction by tethering astronauts during all EVAs. They also eliminated the Manned Maneuvering Unit from EVAs. In the event of serious trouble, the Shuttle Orbiter can fly using the Reaction Control System thrusters for small jumps to pick up a stray object or astronaut. See the history section for the MMU, and the Space Shuttle Orbital Maneuvering System. The hardest part would be tracking the astronaut, whose RADAR cross section and thermal signature are both fairly small; visual contact is difficult because cameras and windows do not face in all directions - so once the astronaut is beyond a (very short) critical distance, the shuttle pilot will not know which direction to fly to recover him (even if that distance is within achievable range and is within safe orbit tolerances). Nimur (talk) 16:13, 2 August 2009 (UTC)[reply]
I don't think the voice radios have directional antennas suitable for location and range detection. (I don't think that functionality is usually needed, so they don't waste mass budget carrying up such equipment). By very nature of being omnidirectional, the voice radio antenanas (on the Orbiter) preclude tracking. It's possible that the shuttle carries a standard set of radio gear, though, and with a sufficiently smart engineer, a direction-finder can be rigged up; but I'm guessing that the Space Shuttle doesn't have that feature ready for use in a standard flight equipment setup.
This news article indicates that NASA is engineering a next-generation EVA radio - a digital, S-band packet system, which will be used for voice, data, and telemetry - but there's no indication of direction-finding capability. I'm looking for more technical briefs on the radios from official NASA sources. Nimur (talk) 19:29, 2 August 2009 (UTC)[reply]
Here is NASA's SBIR solicitation for digital EVA radios; if you have any ideas for how to build a low-power, directional antenna array, you can submit your business plan and research proposal... Nimur (talk) 19:31, 2 August 2009 (UTC)[reply]
I'd think some kind of flashing light Flashing astronaut locator from a bicycle shop would work as well as radio direction finding, unless the person has gone over the horizon. There's no pesky visual obstructions like hills up there. 67.117.147.249 (talk) 20:56, 2 August 2009 (UTC)[reply]
Of course - but it's a matter of range. How far away do you expect to be able to locate the lost astronaut? Also, as I mentioned above, the views are limited to where windows or cameras are mounted. Nimur (talk) 21:09, 2 August 2009 (UTC)[reply]
With a bicycle shop LED strobe, it should be possible to see the astronaut 10 miles away from the shuttle. It would take a long time to drift that far. As for which direction, the lost astronaut should be able to see the shuttle and say which direction he is from it, allowing the thrusters to be used to translate the shuttle to his location. Edison (talk) 00:41, 3 August 2009 (UTC)[reply]
The problem with things like flashlights is that they are very directional - the flashlight shines where you point it - but not much anywhere else. The same is true of the lights on the backs of bicycles. The hapless astronaut is highly likely to be spinning - so the odds of something bolted onto his suit being of any use is rather low. He might have it in his hand - but unless it is tethered to him, the odds are good that he won't.
The issue of the range of vision out of the spacecraft windows might not be such a big deal - the shuttle and space station both have robot arms that are covered with cameras that can be panned and zoomed - so it would be possible to slowly scan the region around the region he vanished from. The astronaut is likely to be in radio range for a LONG time - so whenever he can grab a view of the shuttle, he can say "I'm behind you at about 10-o-clock and above at about 3-o-clock and give everyone a good idea of which way to look.
I guess the biggest determining factor in the likelyhood of saving the astronaut is his speed. If he just missed a footing, the amount of velocity he'd pick up might be of the order of a few centimeters a second - every move the astronauts make on EVA is covered by at least a couple of cameras. It would take a LONG time for the eagle-eyed EVA watchers on earth to lose sight of him - and swivelling a camera in the direction he vanished out of sight in ought to allow them to get a decent fix on his speed and direction within at most a couple of minutes - by which time he's probably still somewhere in the vicinity of one of the shuttle's wingtips. The could aim the arm camera at him and read off the joint angles to get a very good fix on his direction. Once they have a good fix, it doesn't matter that they lose sight of him because his future trajectory is very predictable...and again, he'll be able to see the shuttle for much longer than they'll be able to see him - so he'll be able to say "you need to aim a bit to the left and a bit up". It would be dramatic - but far from certain death. SteveBaker (talk) 00:48, 3 August 2009 (UTC)[reply]
Astronauts are always tethered to the ISS (the last planned EVA from the Shuttle was during STS-125) during an EVA. But in the unlikely case somebody floats away untethered, a jetpack like device called SAFER is attached to the spacesuits. The astronaut deploys a hand controller from near the bottom of the backpack and can thrust himself towards the nearest structure. anonymous649402:07, 3 August 2009 (UTC)[reply]
I was under the impression that the 'SAFER' unit was only being used by the ISS personnel - due to the fact that the ISS could not be manouvered as the shuttle can in order to rescue someone in the event of a disaster. However, I presume the issue comes up when the shuttle is docked to the ISS too (undocking is presumably a time-consuming process)...and since that's pretty much all the shuttle will do from here on until it's scrapped - they may have switched over to using SAFER in all EVA activities. Also, while astronauts are generally supposed to be tethered at all times - there are times when they have to move the tether from one location to another when an accident could potentially occur. It's really unlikely though - the astronauts are well aware of the dangers and you can be pretty sure that their focus will be entirely on the job while they do those kinds of things. SteveBaker (talk) 14:04, 3 August 2009 (UTC)[reply]
If the limitations of joint mobility were not too great, a slowly spinning astronaut should be able to cancel all spin and orient himself in any chosen direction without the use of thrusters. The moves necessary are known to divers, gymnasts, and cats. A battery powered rotary tool might be used as a gyro to turn or to cancel spin. The station should be able to turn on external illuminants or strobes and be visible a l-o-n-g way off. A radar target would not add much mass to the EVA suit. NASA tested on the Shuttle a soccer ball sized robot which would be able to carry a rescue line to a drifting astronaut. A fisherman would be able to cast a strong lightweight line to a considerable distance in space; a "rescue line caster" should be able to target and fire a rescue line, perhaps with a large net at the end. In sci fi stories, spacemen might throw tools or valve off oxygen in the opposite direction to cancel motion and cause drift within range of a robotic arm. How would he acquire motion away from the ISS in the first place? Maybe he jumped off for some reason, and the tether broke or was not fastened. Maybe a pressurized pipe broke loose while he was in its way. Pipe whip can be an awesome propelling force if liquid shoots out an el at the broken end, until the attached end also breaks. Such an event could leave the drifting astronaut stunned and unable to help. Edison (talk) 19:05, 3 August 2009 (UTC)[reply]
Conservation of angular momentum assures us that the astronaut cannot use 'joint mobility' alone to stop the spin. Divers, gymnasts and cats can only do it because there is gravity and air resistance. In a weightless vacuum, he has to impart a spin in the opposite direction to something else...using an electric drill or something might work so long as it can be run continuously at very high RPM - when it slows down again as the battery expires, the astronaut would start to spin as the drill slows down - eventually ending up with PRECISELY the same amount of spin he had at the outset when the battery finally dies. You'd have to get the drill up to speed and then let go of it. Sadly, even that won't actually work because the electric drills and other power tools that astronauts are provided with have internal counter-rotating flywheels precisely so that they DON'T transfer angular momentum to the user. They also don't keep spinning indefinitely - they are programmed to do a specific number of rotations, delivering a closely specified amount of torque and then stop. So that's not likely to work as a means to stop yourself from spinning. You could cancel the spin by accurately tossing two masses in opposite directions...but the manual dexterity, timing and 'feel' for the amount of mass/speed required to do that seem daunting in a bulky space-suit...most likely, he'd end up making matters worse. SteveBaker (talk) 23:40, 3 August 2009 (UTC)[reply]
reduce CO2 by 89%: gross or net?
I read that world CO2 emissions need to be reduced by 89% to prevent unrecoverable disaster. Is this the figure for gross or net emissions? (Unless the rate of removal is expected to fall, the gross figure will of course be less intimidating.) NeonMerlin21:24, 2 August 2009 (UTC)[reply]
I got the figure from a university newspaper and don't have the original source or the details on what harm would and would not be averted. NeonMerlin22:09, 2 August 2009 (UTC)[reply]
It probably meant net emissions from human activity (i.e. something like CO2 emissions from fossil fuel burning plus deforestation plus cement production minus reforestation, etc.) Dragons flight (talk) 23:04, 2 August 2009 (UTC)[reply]
I don't understand your use of the terms "gross" and "net" in terms of CO2 emissions - these are economic terms relating to income taken before or after deductions. What 'deductions' are you thinking about here? I presume that the intended meaning in the article you read is that the annual tonnage of emissions must be 89% of what it is today...that meaning is pretty clear, although "unrecoverable disaster" is not and the number '89%' (why not '90%') seems suspiciously exact for such a fuzzy statement! But this isn't a percentage emission rate issue - the issue is of the total tonnage that's up there. It would take a much smaller cut performed today than the same cut taken in 20 years time.
The CO2 that we emit is likely to persist in the upper atmosphere for perhaps 10,000 years (Greenhouse_gas#Global_warming_potential). So the amount of CO2 we can safely add each year without ever reaching this mythical "point of no return" is 1/10,000th of the total CO2 amount required to hit the point of no return in any given year.
The problem is that we aren't sure where this point of no return is. There are things like the melting of the arctic ice which appear to have already passed the point of no return...as the ice melts, shiney white ice is replaced by dark green water - which absorbs more heat than the ice - which melts more ice. There is no return from that - but the consequences are not so very serious on the scale of potential disasters we expect. However, other systems like the Clathrate gun hypothesis have an unknown trigger point - but consequences that are probably "game over" kinds of event.
It's generally agreed that between 4 and 5 degC of temperature increase will put us past the point of no return - and that every 100ppm of CO2 we add will push the temperature up by around 1 degree. We've added 50ppm in the last 30 years - 25 ppm of which happened in the last 10 years. So if we merely held our emissions to the present level, we'd add 400ppm in 160 years - and that would probably push the global temperature up into the "point of no return". But if we made a 90% (or 89%!) cut in our emissions starting today, we'd still reach the point of no return in 1600 years - and remember that we have to emit at a rate that'll give us 10,000 years.
So the best guess estimate is that we have to cut emissions by about 98% to gain stability. Nobody believes that's possible - society and technology simply can't change that fast. Most authorities are working to give us 100 years of breathing space before we hit that 4 degree mark in the hope that technology (and our understanding) will improve over that time - and with a sizeable 'safety margin' because we know that we have a measure of uncertainty about some of the 'planet killer' effects like the Clathrate gun. But even a 2 or 3 degree rise is insanely bad - that's enough to annihilate an enormous number of major coastal cities, inundate valuable agricultural land, wipe out huge numbers of animal and plant species, etc, etc.
The sad fact is that there is no believable amount of change that will prevent all of the bad consequences...in a very real sense, we've left it too late. If the world had capped emissions at the 2000 levels at the first Kioto accord - we'd have twice as long to think about it. If people had listened 30 years ago and capped levels then - we'd have had many hundreds of years to deal with it. The best we can do at this late stage is to slow down the rate as fast as is reasonable, cross our fingers and hope that a technological miracle comes along before we hit too many of the irreversible barriers.
But with the three major contributors (US, China, India) still growing their outputs at a prodigious rate, with weak response from the US, polite words but almost zero actual action from China and a downright, blatant refusal to cooperate from India - we're in for a very rough ride. Politicians are used to reacting retrospectively to problems...when a couple of bridges collapse in the US, we rush out a program to check and reinforce our bridges...no amount of pleading about the height of the levees outside NewOrleans was effective - but after the city is flooded out, the politicians rush to spend money building them up. But the nature of the CO2 crisis is that if there is enough CO2 in the atmosphere to cause a disaster, then there is literally no action we can take to 'fix' it. It'll take 10,000 years for the planet to recover naturally no matter how much action the politicians take. We have to take action before anything really bad happens - not one day later!
You are oversimplifying. Carbon dioxide residence time is a complex issue because carbon dioxide emitted into the atmosphere will first mix into the oceans and biosphere on a short timescale (100 years), which reduces the remaining atmospheric burden ~70%. Further reductions occur as carbon dioxide in the ocean is converted to calcium carbonate minerals which has a geologically long time scale (100,000 years). (See: [35]) If one believes there is a magic number above which the atmosphere must not rise, then that initial dilution allows one to emit more carbon slowly than if you emit it all quickly. Also, one can maintain stable carbon dioxide concentrations in the 450-550 range while still having an appreciate emissions footprint even 300 years hence [36]. Eventually, those numbers need to trend towards zero, but we can envision emissions scenarios that give us hundreds of years to fully eliminate fossil fuels without truly running off the rails. Of course, even the optimistic scenarios depend on being able to cut ~50% this century (rather than growing by +200%, which seems to be the do nothing answer). Dragons flight (talk) 00:13, 3 August 2009 (UTC)[reply]
In Steve's defense, given the complexity of the subject - which science itself has not yet fully grasped - it would be difficult not to oversimplify at less than textbook length. 87.81.230.195 (talk) 04:31, 3 August 2009 (UTC)[reply]
May I also add that the first shots are being fired from the gun right now?[37] And there's also the permafrost gun, don't forget that one.[38][39][40] We just need tenths of a percent of the excess carbon stored in frozen soils to be released as methane and we don't have to worry about improving gas mileage, at least until the methane stabilizes to CO2 over the next few hundred years. We will have warm summers (and winters). And if the permafrost release triggers the ocean clathrate release, we might get the final answer quite soon, as in our great-grandchildren who don't happen to live in low-lying areas will know exactly how well we did. Franamax (talk) 09:05, 3 August 2009 (UTC)[reply]
If the gun is being fired, so far it is coming up blanks. Methane concentrations now are 30 ppb below the most conservative of the IPCC projections made circa 2000 (and 70 ppb below the most frightful ones). Existing climate simulations have been assuming that methane would increase significantly faster than has actually been observed. Yes, the possibility of methane feedback is a real concern, but with a half-life of only ~12 years and levels that remain inexplicably lower than expected, I think it would be premature to panic about this. Dragons flight (talk) 09:42, 3 August 2009 (UTC)[reply]
Firstly, the signs that some clathrate deposits might be melting are very recent - this may literally only have started during the last 9 months or so - and perhaps only in a small part of the oceans - and it might yet prove to be some other issue entirely. Secondly, while Methane has a fairly short half-life, it traps 70 times more heat than CO2 while it's there...so it has the scope to be a nasty problem that would happen quickly. The nature of the feedback would be to dump an enormous amount of methane into the upper atmosphere - which could produce a sudden and violent change in surface temperatures...far too fast for humans to adapt to. Admittedly, with a half-life of 12 years, the methane problem would abate within 25 to 50 years...but that's more than enough time to trigger all manner of other nasty problems. Also, when the methane disappears, it leaves behind both CO2 and water vapor - so when we say it's "gone" - that doesn't mean that the problem it left behind is over and done with. SteveBaker (talk) 13:49, 3 August 2009 (UTC)[reply]
Most of the clathrates are buried too deep to melt for at least a thousand years even under the most drastic global warming projections, and that's a scientific fact.98.234.126.251 (talk) 01:51, 4 August 2009 (UTC)[reply]
OK, so dinosaurs roamed the earth for about 200 million years. First question is - why didn't they evolve to achieve intelligence like humans did in a much shorter period of time? Then I've been thinking about what would happen if SETI find aliens, or we become spacefarers and meet like-minded curious aliens, or they make their presence known because they have been waiting for us to achieve space travel... these aliens would presumedly come from far older civilizations and be far more 'advanced' than we are, given the age of the universe. Well, if dinosaurs did nothing for 200 million years, why is there a common presumption that aliens would have done any better? Sandman30s (talk) 23:16, 2 August 2009 (UTC)[reply]
Evolution isn't a straight line. You don't "evolve enough" over time and get some kind of prize (in this case, intelligence). It doesn't go towards any particular ends, and high, high-levels of intelligence, like humans have, are expensive and for most species unnecessary for their survival. You could easily say, humans have been around for awhile now, why haven't we evolved to achieve wings or giant horns on their heads? It's also worth recalling that though humans at at the top of the food pyramid now, we were quite scrawny and desperate for a good deal of known human history. While its true that in the long run, having lots of brains allows a species to become quite powerful, in the short term being able to adequately reproduce and protect your young is all that is really necessary, and there are plenty more direct ways to do that than having a gigantic frontal cortex.
The presumption about aliens is that if an alien had the capacity to reach us, they probably have much more advanced technology than us, because we don't really have any real prospects of being able to get across the vast, VAST distances of space in any reasonable amount of time. If something has managed to get over to us, it is probably more advanced than we are. --98.217.14.211 (talk) 23:23, 2 August 2009 (UTC)[reply]
There is some empirical evidence that dinosaurs were getting smarter (or more precisely that the relationship between brain mass and body mass was moving in a direction that favors intelligence in modern analogs). In general fish are less intelligent than reptiles, which are less intelligent than mammals, which are less intelligent than primates, etc. The evolutionary developments that led to human intelligence probably progressed through 100s of million of years, and not just the few million years of homonids. With respect to alien civilizations, I would also point out that a lot of the achievements of humanity are associated with the cultural preservation of knowledge and not intelligence per se. As species we biologically evolved almost not at all in the last millenia, but at the same time we have gone from the dark ages to space flight through the accumulation of knowledge. Regardless of their biological potential, an intelligent society with a million years of recorded history will almost certainly have accumulated far more knowledge than we have achieved in our few thousand years. Dragons flight (talk) 23:33, 2 August 2009 (UTC)[reply]
The comparison between Dinosaurs and Humans is false. Dinosaurs were (are if you include Birds) a Superorder successively divisible into 4 Sub-orders, numerous Families, many Genera and very many Species (see Taxonomic rank), whereas "Humans" is defined narrowly as a single Species (Homo sapiens) and most broadly as a mere Genus (Homo). A "fairer" comparison would be between Dinosaurs and Primates, the Order to which Humans ultimately belong. As Dragons Flight broadly said, the Primate Order is thought to have arisen as long as 85 million years ago, so one could say that it took the Primates at least 83 million years to evolve "intelligence" (depending on your definition of it): equally valid might be a comparison between Dinosaurs and Eutheria, the Infraclass of non-marsupial mammals to which Primates belong, which is at least 125 million years old.
Since evolution is not directed, but in large part contingent on varying external pressures, it says little to observe that one lineage acquired some new characteristic or notable improvement in one (such as intelligence), more "slowly" or "quickly" than another. In line with .211's observations, high intelligence didn't evolve in Dinosaurs over a long span because it wouldn't have been immediately advantageous in the prevailing conditions. It did so in Primates and in particular Humans because their conditions happened to favour it - this may have involved some low-probability coincidences in the preceding evolution of a series of traits (e.g. binocular vision, opposable thumbs, arboriality as a preconditioner for bipedalism, unusually complex social relationships) which, when combined, happened to make the evolution of intelligence more easy. 87.81.230.195 (talk) 00:57, 3 August 2009 (UTC)[reply]
I haven't got a good explanation for it but I recently read that becoming warm blooded was a necessary step in developing the brain beyond a certain point. So high intelligence in lizards is unlikely, even if the dinosaurs were not wiped out. Vespine (talk) 01:08, 3 August 2009 (UTC)[reply]
I believe there is evidence that at least some dinosaurs were warm-blooded (See this for a great summary of the arguments). Look at it this way: We know that birds are warm-blooded - and we're pretty sure that they appear to have evolved from feathery dinosaurs. Is it so unlikely that dinosaurs FIRST became warm-blooded THEN became birds rather than vice-versa? I'd argue that you need to be warm blooded in order to be able to fly (at least at the body size of birds) - hence things had to happen in that order. Ergo - there were almost certainly warm blooded dinosaurs. Either way, you can't rule out intelligence by ruling out warm-bloodedness because the latter is unproven. Furthermore - dinosaurs were not reptiles - relating what they could or couldn't do to modern lizards is simply not a valid thing to do. It's even possible that they DID become intelligent - at least to some degree - after all, there would be little or no evidence remaining of any kind of civilisation after all this time. We've only gained recognisable signs of civilisation in the last 5,000 or so years - we'd be very unlikely to spot signs of intelligence over such a small window.
As for the presumption that aliens would be intelligent...I don't think we do make that assumption. The most common argument that aliens must exist is the Drake equation. It contains a term fi that expresses the probability of life becoming intelligent. Plugging different numbers into fi gets you different probabilities that there are aliens out there who might be able to communicate with us. Most people have estimated that term at 1% - a few pessimists put it at 0.1% - some optimists put it at 100%. However, the total number of alien civilisations that are likely to be out there depends on so many unknown parameters that it's all just guesswork.
Steve: while your points about the likelihood of (some) dinosaurs' warm-bloodedness (though cold/warm-bloodedness is a rather crude and outmoded dichotomy) and the possibility of any evidence for dinosaur high intelligence being missed are valid, it is simply not true to say that "dinosaurs were not reptiles." Our Dinosaurs article's taxobox, for example, gives their classification as -
I agree with your point that modern-day reptiles are not fully representative of all that the Reptilia ever were and potentially could be, but bear in mind that, as well as "lizards," the rather impressive Crocodilia are also reptiles not too distantly related to Dinosauria, and that the majority of palaeontologist now interpret Birds as being, not merely "evolved from feathery dinosaurs," but actually to be dinosaurs, within the suborder Theropoda, though there is some dissent (some to the effect that instead, some dinosaurs are actually descended from birds) and many disagreements over the fine details. As is fairly well known, some birds such as Crows and Parrots can exhibit significantly high intelligence, to the extent of making and/or using tools and appearing to, not merely mimic, but actually to comprehend (and controversially, to rudimentarily use) human speech. 87.81.230.195 (talk) 04:24, 3 August 2009 (UTC)[reply]
Yep - I agree with all of that - I was somewhat oversimplifying for the sake of brevity. Indeed, the terms "warm blooded" and "cold blooded" are not completely explaining what's going on...however, the remark I was contradicting used those terms and I felt it better to reply in kind. Whether we call dinosaurs 'reptiles' and whether birds are indeed dinosaurs (and therefore 'reptiles'!) is mostly a matter of naming. The big prehistoric beasts that we think of as "dinosaurs" are certainly more closely related to birds than they are to lizards. Hence, there is no particular reason to assume that their metabolism resembles lizards more than they do birds. Hence (as I remarked before), the fact that lizards are not particularly intelligent does not prevent dinosaurs from being intelligent...and I agree that the relatively high intelligence of some birds leaves open the possibility of fairly intelligent dinosaurs. If you go with the idea that dinosaurs (or at least the therapods) are descended from birds - then the case may even more strongly be made. 13:07, 3 August 2009 (UTC)
Except that most dinosaurs had very small brains relative to their bodies. Only some of the most bird-like ones ("raptors" and the like) are comparable to (certain) modern birds and mammals in this respect. Not to the smartest birds and mammals either, as far as I remember (vaguely).--91.148.159.4 (talk) 19:40, 3 August 2009 (UTC)[reply]
But like the OP, .4, you're somewhat 'cherry picking' by implicitly comparing "most dinosaurs" (downplaying an alleged minority that were more intelligent) with the small minority of the mammals that have "intelligence like humans" in the OP's original phrase. Also, one cannot simply equate brain size (or better brain/body size ratio) with intelligence across Classes: the architecture and possibly more subtle workings of reptile/dinosaur/bird brains are different to those of mammalian brains, and studies of extant reptiles/birds suggest that a reptile with a given brain/body ratio is more intelligent (insofar as one can measure it) than one would expect in a mammal with the same ratio.
I think Steve and I are arguing somewhat past each other, but I can't agree that we should leave popular misconceptions exemplified by "The big prehistoric beasts that we think of as "dinosaurs" . . ." unchallenged. Bigger bones are preferentially preserved and easier to find, and big animals are disproportionally impressive, leading to sample bias and naive-observer bias, but in reality the majority of (Triassic/Jurassic/Cretaceous) dinosaurs in terms of both species and absolute numbers were probably smaller than, say, humans, and many (e.g. this) were tiny, just like a lot of their extant examples/descendants (e.g. this). In an encyclopaedic context we should surely endeavour to promote the more accurate picture? 87.81.230.195 (talk) 21:03, 3 August 2009 (UTC)[reply]
Wing contact on landing
The question on crosswind landing above reminded me of a rough landing experience I had at SFO. It's been a while, but I believe the flight was a Boeing 767. We were arriving in windy conditions. At roughly 10 or 15 feet from touchdown, the plane tilted violently to the extent that the tip of one wing almost certainly was momentarily lower than the landing gear. The pilots recovered and we landing without further incident; however, if it had happened just a few moments later in the approach I easily could have envisioned the wing tip clipping the ground.
So, my question, how common are incidents like this? And, how bad would it have been if the wingtip really had made contact? It certainly made an impression on me at the time. Dragons flight (talk) 23:18, 2 August 2009 (UTC)[reply]
Well, if the wingtip touched the ground, the result would certainly be a major disaster - the plane would get a violent jerk in the direction of that wing and would probably cartwheel and break up. I have no idea how common it is for a wing to dip alarmingly low on approach - but I don't think there are many cases where it happened close enough to the ground to cause a crash. I don't know how you judge what happened - from the perspective of a passenger, even quite gentle manouvers seem rather violent...and you have no way to know how low that wingtip really dipped. Your estimate for the plane's altitude may also be 'off'. People tend to assume that the markings painted onto the runway are similar in width to road markings - but they are MUCH wider...that makes you think you're lower than you really are. If it's any comfort, aircraft have inherent stability when they get closer to the ground - there is a "ground effect" which increases the amount of lift under the wing the lower it gets to the ground. If one wing starts to dip low and the other raises up then the down-going wing will gain extra lift and the up-going wing will lose lift - that tends to level the plane out. The closer that low wing gets to the ground, the stronger this effect becomes. Even far from the ground, the fact that the wings on the plane have 'dihedral' gives it some degree of inherent roll stability...but ground effect is pretty powerful. SteveBaker (talk) 02:10, 3 August 2009 (UTC)[reply]
"Certainly" is too strong. See [41] - last year, an Airbus A320 hit the ground during a crosswind landing. The pilot managed to turn it into a touch-and-go landing, but the touch involved parts of the aircraft that should not really touch anything... --Stephan Schulz (talk) 02:48, 3 August 2009 (UTC)[reply]
Runways at SFO
Yes, it is possible I misjudged the height, but I don't think I would have done so by a large amount. SFO has an over water approach (image at right), and we had already reached the land/runway when this happened and were only moments away from landing. Dragons flight (talk) 03:24, 3 August 2009 (UTC)[reply]
I'd say too that it wouldn't necessarily be a disaster. Wings on large jets have a good degree of flex, so my first thought would be that the wing would "bounce". Especially so if it was a sideways roll as opposed to a "tilt-and-slew-down-and-to-the-side", which would tend to drive the wing into the ground. Now, as to Stephan's linked video clip, that's just plain crazy. I'd like to read the incident report on that one, as in, why did the pilot even make that approach? (And Df, I think there are FAA reports you can search to see if your own flight got listed as a near-miss type of incident). Franamax (talk) 08:08, 3 August 2009 (UTC)[reply]
That Hamburg incident in the video DID involve a wing strike, with slight damage to the winglet and leading edge. That means there would have to be an investigation. I've looked on the German aviation authority website and not been able to find a report. Perhaps at 16 months it is too soon. - KoolerStill (talk) 11:35, 3 August 2009 (UTC)[reply]
ID an integrated circuit (IC) manufacturer?
Hi, not really science, but I reckon the people best able to answer my question will be most likely to be watching this desk.
Can anyone here ID the logo of an IC manufacturer? Too hard to photograph, but the logo is a nice, distinctive italic capital T, with an additional stroke to make it also look like a capital F. An oblique 3/4 circle encloses the top of the logo The logo has a circle which cuts the upright of the T/F below the lower horizontal bar of the T/F. Incidentally the chip in question is an MC 34063.
--Polysylabic Pseudonym (talk) 23:36, 2 August 2009 (UTC)[reply]
These are the manufacturers of the MC34063, which is a switching voltage regulator. It sounds like you might be mis-interpreting the Texas Instruments logo as an "F" (it's really a map of Texas). Take a close look at this Texas Instruments SN7400 and see if it's the logo on your chip. Nimur (talk) 01:30, 3 August 2009 (UTC)[reply]
Definitely an italic capital T modified to make an F. No serifs. Is there a cheap knock-off manufacturer with initials TF? No hint of a texas map outline, no hint of an i -203.22.236.14 (talk) 02:00, 3 August 2009 (UTC)[reply]
There are literally a dozen companies that sell that part. "Fantastic Technologies"[42] are the only ones who have F & T as their initials...but I can't find pictures of any of their chips to see what they might stamp onto them. What kind of package is the chip in? That would help to narrow down the list of suppliers. SteveBaker (talk) 02:23, 3 August 2009 (UTC)[reply]
They resell, but do not manufacture, the MC34063. As you can see, they're vendors of an ON Semi version (and maybe a Motorola version - but I doubt that's a stocked part, since Motorola Semi is now Freescale, and they're not making this part). There really are only four manufacturers for this part. (One of the most important things to realize in hardware design is that "presence in the catalog" does not mean "part actually exists and you can order it"). Experience and a bit of "hunch" is necessary to sniff out a real part from a catalog-only part. Nimur (talk) 05:32, 3 August 2009 (UTC)[reply]
Great set of sites Nanonic! But can't find it there either. The logo looks a lot like the Fairchild logo, but with the top of the F extended to the left. --203.22.236.14 (talk) 04:10, 3 August 2009 (UTC)[reply]
acid strength versus pH versus acid ability (for strong acids)
Something that I don't quite get is the different behaviours of strong acids, since they all undergo complete dissociation. I have a salad of various conceptions. Why isn't there a lower bound on pH and pKa after complete dissociation?
I understand in some reactions, the acids form reactive intermediates after being protonated, and it is them and not the protons that carry out the reaction, especially in electrophilic substitution. I am not referring to this.
But take say, magic acid, and say I diluted magic acid to a pH of 1, and diluted a solution of hydrochloric acid to a pH of 1, and then added a hydrocarbon (or some other tough-to-protonate substance) -- would the magic acid behave similarly to the hydrochloric acid?
I do imagine that eventually among the strong acids the limiting factor becomes not the H+ concentration but the conjugate base which will "take away" the proton on substances that do not like to be protonated, even if the H+ concentration is very high -- because then the conjugate base concentration is very high too, and the conjugate base becomes a better proton acceptor than whatever is being protonated. Am I heading in the right direction here? John Riemann Soong (talk) 00:55, 3 August 2009 (UTC)[reply]
Actually, the better way to think of it is that strong acids are those whose pKa is higher than that of hydronium (H3O+). That means that, in all of the strong acid, hydronium has a higher "proton affinity" than does the acid, so the acid fully deprotonates. If you change the solvent to something that isn't water, for example pure acetic acid, then your list of "strong" acids would change to those that have a lower pKa than that of the "acetium" ion, and likewise for any given solvent. --Jayron3203:52, 3 August 2009 (UTC)[reply]
When you say "But take say, magic acid, and say I diluted.." do you mean in water, or in a totally inert solvent - the two situations are different - in water, as mentioned above the acid species is H3O+ .. so both act the same (since water is easily protonated by strong acids)
In an inert (non basic solvent) the pKa matters - so the magic acid and hydrochloric acid will have different aciditys - because H-Cl and H-magic still exist (they will have dissociated in water)
pH is the -log of the H+ concentration - so the more acid you add the lower the pH goes - there is a lower bound - determined by how concentrated an acid can be (I think about 20Molar is about the maximum)
Simialiar pKa is the -log of the dissociation constant - the more readily a compound dissociates the lower it goes - the dissociation constant is a ratio, and so can go from 0 to infinity (ie unbounded) In reality total dissociation is impossible, but the dissociation constant can get very very big.
"Complete dissociation" is an approximation - in practice it's 99.999% or more dissociation - so it can be treated as being total when measuring H+ concentrations.
You should at least read the first paragraph of pH and pKa linked above, or another source - to make sure you understand what pH and pKa are, and how they are measured (ie a logarthyms), and how they are different.
"I do imagine that eventually among the strong acids.." - no. You are describing deprotonation, ie the action of a base, not an acid. In general a strong acid makes a very stable base - eg HCl makes H+ and Cl-, Cl- is the base - it is not a good base - it is a very weak base, and is stable. The factor when comparing very strong acids (in pure form) is the stability of the conjugate base, and its lack of ability to accept a proton. Thus weaker conjugate bases are better.83.100.250.79 (talk) 11:24, 3 August 2009 (UTC)[reply]
If you're trying to protonate say an alkane, or benzene with different very strong acids both the pKa of the acid, and the pKa of the acid form of the alkane contribute to the extent of protonation.
eg if
Alkane + H+ >>> [AlkaneH]+ (equilibrium constant = A) .. how hard it is to protonate the alkane
and
Acid >>> conjugatebase- + H+ (equilibrium constant = B) .. how strong the acid is
Did you mean acids that are very strong because of the stability of the conjugate base - there are examples of this - a mixture of HF and PF5 is a very strong acid - not because HF is strong but because the anion PF6- is very very stable. ? Conversely there are very strong acids which the main reason for their strength can be considered to be in greater part the instability of the cation eg CH5+
I'm pretty sure that once the food has passed out of the stomach into the intestines (i.e. past the pyloric valve) that it is pretty much only going out the back door... --Jayron3204:29, 3 August 2009 (UTC)[reply]
According to our article on Vomiting, the retroperistalsis starts at about the middle of the small intestine. Pyloric valve is relaxed, so it does not prevent the small intestine content from joining the vomitus. I did not know that, I am not a doctor (not an MD, that is; my PhD does not help here, it's in physics :) ; but I really hope our article is right. --Dr Dima (talk) 06:08, 3 August 2009 (UTC)[reply]
I have heard elsewhere that the intestine contents do not back up into the human stomach. ReverenceReference to a reliable source is called for. By the way, a physicist should start his answer to such a question be saying "http://www.physics.csbsju.edu/stats/WAPP2_cow.html] Assume a spherical stomach..."
Crash location on the Moon of Ranger 4 (April 26, 1962)
The article Ranger 4 gives three different sets of lunar coordinates for the crash site: “15°31'S 130°42'W” (infobox); “15.5°S 229.3°E” (paragraph 4, lifted from this page); and “15°30'S 130°42'W” (paragraph 5). The longitude of all three is equivalent, but the latitude in the infobox differs by one minute from the other two. The article List of artificial objects on the Moon gives a different location for the crash of Ranger 4: “12.9°S 129.1°W”. Since this location was on the far side of the moon, how did NASA even know where it was in 1962? Were they just estimating based on its trajectory at the time it was last sighted? See this source from NASA which gives a different longitude (229.5°E rather than 229.3°E), attributed to a statement by William Pickering. I would speculate that lunar orbiting missions in later years were able to pinpoint the location better, but if you read Wikipedia you only see different coordinates given with no indication of their source. Also there are three different formats for lunar coordinates used in the same article, which is unprofessional. —Mathew5000 (talk) 03:33, 3 August 2009 (UTC)[reply]
Well “15.5°S 229.3°E” is a rather unconventional way to express a longitude. One would normally either give a number in the range 0..180 followed by E or W (east or west) - or give a number in the range 0..360 without either an E or a W. So 229.3E is really (360-229.3)=130.7W - but that's in degrees. So 15.5°S 229.3°E is the same thing as 15°30'S 130°42'W so the error between the three sets of numbers in our main article is actually just one arc-minute in latitude. Since that's in the least significant digit, we're probably looking at different roundoff errors between numbers obtained from different sources...so the Ranger 4 article is actually pretty reasonably self-consistent (although one could wish they'd used the same representation in all three places in order to avoid confusion). However, 12.9S 129.1W is nowhere near there. It is of serious concern that these articles are not indicating their sources - because checking sources is the way we are supposed to be able to correct (or at least explain) these kinds of discrepancies. That's a serious matter that you should certainly take up with the authors of the article on the talk: page. SteveBaker (talk) 12:54, 3 August 2009 (UTC)[reply]
Of course! Carrots are great for a cake or a tzimmes. Other veggies can do great in desserts just as well. Here is an article in Gourmet on vegetable desserts. If you google for vegetable desserts, you'll find many others, too. Bon appetit! --Dr Dima (talk) 06:37, 3 August 2009 (UTC)[reply]
Cinnamon (bark), sugar (made either from tubers or stems), maple sugar (from sap), and the various syrups, treacles, and toffees that are made from sugar. -- Finlay McWalter • Talk01:18, 4 August 2009 (UTC)[reply]
Most of these responses seem to be assuming that vegetable just means plant. That's true at a very basic level, but I doubt it's what the OP was interested in, which (I surmise) referred to vegetables in the sense of "you should eat five (or whatever it is) servings of vegetables per day". The only answers that are responsive to that question are the ones about carrots and yams (sweet potatoes). oh, and I missed the pumpkins --Trovatore (talk) 03:24, 4 August 2009 (UTC)[reply]
Oh, and in this sense, pumpkins are definitely a "vegetable" and not a "fruit". Botanically, a fruit is anything that has seeds (more or less; I'm not a botanist), but culinarily, a fruit mostly has to be sweet (though it might also be sour enough that the dominant impression is sour rather than sweet). --Trovatore (talk) 03:55, 4 August 2009 (UTC)[reply]
Potato pancakes make the list, so do amaranth cookies. For a light summer desert try butterhead lettuce with a dressing made from sour cream, lemon juice and sugar. (Serve cool but not chilled.) Sweet corn counts which adds a whole list of things from cornflake crubles to pies to corn muffins etc. If you have friends in South Africa they could send you some gooseberry jam and you could try one of the countless cookie and cake recipes with jam filling. Arrowroot is listed in Root vegetable but seems to be missing from List of culinary vegetables. One can make all sorts of desserts from that. 71.236.26.74 (talk) 06:28, 4 August 2009 (UTC)[reply]
Well, I think so. For example if you have previously had a Caesarian section and are considering a natural childbirth they do a procedure called "trial of scar" which I imagine might be an assessment of exactly the risk of a scar bursting open. --BozMotalk12:08, 3 August 2009 (UTC)[reply]
Trial of scar isn't really a diagnostic test. It just means going ahead with a vaginal delivery, but keeping an eye out for signs of the old scar rupturing, and doing a Caesarean if any occur. --Sean14:36, 3 August 2009 (UTC)[reply]
Bleeding inside a space suit seems to have saved an astronaut's life. "..a suit was punctured in space. That incident was apparently caused by using the glove as a hammer to drive a balky pin. A 1/8" steel bar migrated out of the palm restraint and punctured the glove. In that one case, the steel bar and the astronaut's blood sealed the puncture;.." [2]Cuddlyable3 (talk) 09:50, 3 August 2009 (UTC)[reply]
I would think that a tapered rubber plug going from say 1/16 inch to 1/2 inch would be useful. Push it into the hole until the leak is minimized. A 6 mm hole in a glove was said above to give the astronaut 1/2 hole to get back inside a pressurized place. Even direct pressure from a finger should slow the leak. A plastic bag with a sticky seal tied tightly around the glove should also be a life saving measure. A wire could clamp it around the metal glove fitting, or the metal attachment of a boot, for that matter. Edison (talk) 18:51, 3 August 2009 (UTC)[reply]
Diamorphine pills
Do UK physicians prescribe diamorphine in pill form? I remember a chap at school who had what he purported were diamorphine pills, but now I imagine all diamorphine is delivered by needle. 82.111.24.28 (talk) 13:43, 3 August 2009 (UTC)
EDIT: I should add, I have no medical need for this information, am not asking for advice etc etc[reply]
Since the human eyes is very sensitive, then what about if I'm in the blue light all the time, how come I still notice blue. When I'm in a green light all the time, the green light is still visible to me. What will happen if I'm in a room full of green light, would I still notice the green light. Would this be possible for a white object to look orangeish yellow, while pink object looking black? This never seems to happen in my lifetime. Since cherry color is at the front end of spectrum, violet is at the back end of spectrum, the fronter the spectrum, the color is easier to wash away?--69.229.108.245 (talk) 17:43, 3 August 2009 (UTC)[reply]
Your brain compensates, so if you look at something that you know should be white your brain will compensate for any colour in the ambient light so that it looks the "correct" colour. If you don't know what colour something is supposed to be you can easily get it wrong - try working out the colours of cars under sodium street lights. I don't think it makes any difference what end of the spectrum a colour is, the brain doesn't work in terms of wavelength, it works in terms of how much each of the three types of colour sensing cells in the retina (cone cells) is stimulated. --Tango (talk) 18:09, 3 August 2009 (UTC)[reply]
If your eyes are exposed to one color of light, afterwards things of that color will look very desaturated, and things of the complememtary color will have enhanced saturation. You say you "notice blue," but isn't it desaturated or less vivid compared to when you have not been exposed to light of the same color? Edison (talk) 18:46, 3 August 2009 (UTC)[reply]
Personal observation - back in the days when I used to spend long periods working at a monochrome computer monitor that displayed green letters on black, when looking out of the window for up to an hour or so afterwards I would see, for example, white cars as being pale magenta. Such chromatic adaptation effects (see under Color vision) can involve both a degree of photoreceptor fatigue (see under Complimentary colour) and unconscious mental adjustment (see under Color constancy).
This is why, for example, one has to use different kinds of film for indoor and outdoor photography - pictures taken with outdoor film indoors under incandescent (tungsten) lights look astonishingly orange, even though to our acclimatised eyes such lighting seems quite "normal." Conversely, try out the effects of a "daylight bulb" (available from most arts/crafts supply stores) indoors at night. 87.81.230.195 (talk) 21:16, 3 August 2009 (UTC)[reply]
This effect is very noticeable if you ski with goggles. Ski goggles are typically tinted orange or yellow, and after taking them off the snow appears blue or purple. Rckrone (talk) 04:19, 4 August 2009 (UTC)[reply]
Because they know what various responses to the standard inkblots mean. They wouldn't know how to interpret responses to random ink plots. One of the things they look at is whether you come up with original responses or the same kind of responses as other people come up with, that certainly couldn't be done with random inkblots generated for each person. --Tango (talk) 18:16, 3 August 2009 (UTC)[reply]
(ec)Because there are set interpretations for subject responses. If there weren't, all the test would show was whether the subject had the same set of mental disorders as their psychiatrist. (insert usual caveats about Rorchach being untrustworthy and thus showing nothing of the sort). -- Finlay McWalter • Talk18:18, 3 August 2009 (UTC)[reply]
Well, yeah, but in most situations the patient doesn’t have some motive for fooling the psychologist. That would be about as useful as surreptitiously taking insulin before a glucose tolerance test, in order to trick the doctor into thinking you don’t have diabetes. Red Act (talk) 18:59, 3 August 2009 (UTC)[reply]
Well, it's a little more complicated than that. They are now quite easy to stumble upon online (and on Wikipedia) and a lot of psychologists are starting to wonder if the test is going to lose its use altogether for that reason. There was an article on this recently in the New York Times: A Rorschach Cheat Sheet on Wikipedia?. As for the motive to fool a psychologist, I think to assume total rationality in the realm of psychological or even medical practice on behalf of the patient is probably not totally correct. We all get a bit hung up about being diagnosed, I imagine. --98.217.14.211 (talk) 22:45, 3 August 2009 (UTC)[reply]
There has been a major change in the nature of this issue because the standard set of blots recently came out of copyright protection. That's why they recently ended up here on Wikipedia causing such an upset with the Physchologists. Check out this long argument about the ethics of Wikipedia doing that: Talk:Rorschach_test/images. SteveBaker (talk) 23:56, 3 August 2009 (UTC)[reply]
A psychologist who was trained on projective tests in the 1940's tole me that he could achieve the same results by having the examinee give his reactions to random cartoons, magazine illustrations or cereal box illustrations. This seems way to the mumbo~jumbo edge of science. Edison (talk) 01:32, 4 August 2009 (UTC)[reply]
History of science: from pseudoscience to empirical science
Not really. It's not that various types of science come from things that would now be called pseudoscience, it is that the entire concept of science came from the entire concept that is now called psuedoscience. Some pseudoscientific things could turn out to be right, but it would just be a coincidence. --Tango (talk) 18:12, 3 August 2009 (UTC)[reply]
It seems quite possible that future historians of science might look back on the beginnings of what by then is an established branch of science, and see that in the past it was considered pseudoscience. Things which might be called obvious hoaxes if presented now might really be just engineering challenges. But from this point, it it appears to run afoul of presently accepted scientific laws, and if it cannot be replicated in the labs of a skeptic, if it is not a robust phenomenon, then it is presently properly called pseudoscience. There might really be ways to "reading minds." Some glimmerings of that have been achieved with cortical evoked potentials recorded by scalp electrodes (the P300 potential), and by functional MRI. Cold fusion might be found practical. Messages or visits from extraterrestrials might occur. Levitation (they can do it magnetically with frogs in a lab) and "invisibility cloaking" (early steps toward it have been written up) might be practical on the human scale in the distant future. Edison (talk) 18:43, 3 August 2009 (UTC)[reply]
I don't think that affects the point that things like alchemy were a precursor (whether scientific or not) of more useful studies. Who knows, "cold fusion" research might eventually inspire something useful even though it almost certainly won't be limitless clean energy. Dragons flight (talk) 20:15, 3 August 2009 (UTC)[reply]
There is scientific research into cold fusion. It's fringe science for the most part, but it is science. It is certainly possible that something will come of it and it could well mean (near) limitless clean easily accessible energy. --Tango (talk) 20:33, 3 August 2009 (UTC)[reply]
An historian of science would tell you that historically speaking, what is "science" and "not science" has changed rather dramatically, and our modern definitions of "science" that people cling to (e.g. methodological rules, etc.) are often quite, quite recent. ("Falsifiability" didn't come into vogue as a demarcation criterion until the 1950s.) And most philosophers and historians are not at all content with the idea that such criteria can be applied historically or presently. (See demarcation problem.)
So yes, sure, things that are now considered "pseudoscience" could, depending on the circumstances, become the germ of something that is considered to be "real" science.
On the other hand, there is no reason to assume ahead of time that they will, and the fact of a few examples of things that did become important (alchemy, for example) does not actually prove anything about the likelihood of current pseudosciences becoming accepted as sciences. It is no more encouraging than the fact that some scientists were initially ridiculed but were later revered—the fact of it does not help you distinguish between the ones who were rightly ridiculed and those who are not (and a great deal of the scientists ridiculed deserved to be). One of my favorite Carl Sagan quotes: "But the fact that some geniuses were laughed at does not imply that all who are laughed at are geniuses. They laughed at Columbus, they laughed at Fulton, they laughed at the Wright Brothers. But they also laughed at Bozo the Clown." --98.217.14.211 (talk) 22:36, 3 August 2009 (UTC)[reply]
I'm going to agree that alchemy and astrology are not true precursors. The true ancestor of all modern science is the ascendance of secular knowledge and its codification. A process that started with the renaissance and just meandered its way across Europe. This codification dealt with almost all aspects of life but was arguably most transformative in how it dealt with natural phenomenon. This codification has been extended to all measurable phenomenon with remarkable results. Gentleman scholars such as Boyle had a need to create chemistry as we know it not to progress alchemy but to have a more complete secular explanation of the world. They were scientists first and chemists second, chemistry was just another part to understand. Chemistry in particular only developed after the scientific method (or process) had been successfully applied to number of other fields such as astronomy, physics, biology, and anatomy. I think chemistry is the youngest of the hard sciences (or "hard" natural philosophies). This isn't to say that early natural philosophers didn't use some of the "raw data" and "hints" they collected from alchemists or astronomers but they contextualized the data very differently. They had completely different motivations and interpretations. The early scientists really had to start data collection from scratch since maintaining a good reliable community record (a defining aspect of science) was part of the new codification system. Alchemy didn't evolved into chemistry, the practice of science spread to the transformation of matter and became known as chemistry.--OMCV (talk) 01:49, 4 August 2009 (UTC)[reply]
I just want to note that no professional historian of science today would agree with you. All have long since accepted that the line between "real" chemistry and alchemy is not only blurry, but impossible to distinguish. There is no methodological, epistemological, or quantitative criterion that you can use that successfully puts the "alchemists" on one side and the "chemists" on the other. Trying to say, "oh, well science developed, and got applied to alchemy" is even more incorrect from a historical standpoint. (There is no point in trying to go into strict historical details here, but if you want recommended reading on the topic, I'd be happy to send it along.)
Once question one might ask oneself is, what are the stakes in trying to draw that line, anyway? Is it because we want to say that bad science is always bad science and will always be? (Which is sort of obviously absurd, and certainly not epistemologically justified.) Or is it because we want to avoid having to give any credence to bad or pseudoscience today? (We don't really have to, even if the historical argument is as such, as I've emphasized.) --98.217.14.211 (talk) 01:58, 4 August 2009 (UTC)[reply]
That sounds rather post-modern to claim that things are too blurry to distinguish. From what I can understand a value for secular knowledge did emerge at some point and after a time dominated many cultures understanding of natural phenomenon. It was a cultural phenomenon that I would describe in evolutionary language whether or not that language is in vogue for historians. No doubt the edges blur just as the edges of "species" blur. I think alchemy would have gone on forever without any significant "progress" without the very significant introduction of a "methodology". In my view cross pollination form the other hard sciences. Like I said, Boyle and the The Sceptical Chymist seems to be a reasonable, if imperfect, place to draw the line for chemistry. But I am interested in the mainstream historic perspective, is it more consistent to follow disciplines according to its subject matter than it is to follow underlying practices and philosophies?--OMCV (talk) 02:19, 4 August 2009 (UTC)[reply]
Chemistry is a tough example; but in astronomy or physics, there are a few critical moments - like the publication of Principia or the church trial of Galileo - where one can definitely draw down the line and say, "in one corner, Modern Scientific Method, and in the other corner, outdated knowledge devoid of empirical basis". Specific instances and specific dates are more difficult in chemistry, but the adoption of atomic theory in the 18th century is a pretty crucial turning point. Nimur (talk) 02:23, 4 August 2009 (UTC)[reply]
I think the importance of drawing lines is so that as scientists we can successfully transmit our culture and its values. Values which including honesty and forthrightness. "Falsifiability" isn't the best example to give about the malleability of scientific philosophy over time since the ideas contained in the concept already existed in science in a variety of forms. Popper just codified the "concept" under a word, as Popper's fame diminishes so will the importance of the term "falsifiable". Nimur I think you are right that chemistry is hard but I think thats part of what makes its history interesting.--OMCV (talk) 02:36, 4 August 2009 (UTC)[reply]
Occam's Razor is a much more time-honored principle than falsifiability - it fills the same mental niche of allowing us not to have to concern ourselves with things that are just too crazy. The razor accords more flexibility in interpretation than falsifiability does - but on the downside, it's not as rigorous. The bottom line is the same though: There are a literal infinity of unproven and/or unprovable hypotheses (Russell's teapot, etc) - if we had to seriously consider them, our minds would be crippled by it.
Does this apple fall from the tree because the earth imposes a gravitational force on it - or is there an invisible purple unicorn from the planet Zaa'arg pulling it off the branch? Do I reject the latter argument because of the impossibility of proving that invisible purple unicorns exist (unfalsifyability) - or do I reject them because they introduce concepts like invisibility and the existance of unicorns which are unnecessary to our explanation? It doesn't really matter. The only way to proceed without being blindsided by that impossible number of useless ideas is to rigorously prune them.
Falsifiability and Occam's razor are vital and powerful tools for reasoning about the universe - almost as essential as the scientific method itself.
Pseudoscientific concepts always fail the razor - and often fail falsifiability too. We can falsify things like telepathy if the practitioner will submit to careful pre-agreed scientific study methods - and abide by the conclusions. However, it doesn't work like that. The tiny proportion of pseudo-science practitioners who actually agree to submit to these tests (eg James Randi Educational Foundation's million dollar prize) inevitably, fail to win. Mostly they just make up some lame excuse like "Well, my powers don't work when scientists study them." - which moves them firmly into the "unfalsifiable" category. Those who refuse to undergo these tests (despite the offer of a million dollars!) are already in the "unfalsifiable" category. But we could have avoided doing the experiment or offering the money at all just by invoking the razor...if telepathy worked, there would have to be a whole order of communications media that no experiment has yet revealed - the tissues of the brain would have to function in ways entirely differently than cellular biology would have us believe - we'd have to wonder why evolution has not given all of us use of this faculty. Since there is not a single experiment that points towards such things being true - the hypothesis that the practitioner is a lying, cheating bastard is far less complicated conclusion than it is to assunme that almost all of physics and biology is incorrect. Occam's razor really helps out under those circumstances - even though we know that it's not always right. SteveBaker (talk) 04:04, 4 August 2009 (UTC)[reply]
car brakes question
If someone was to wear their brake pads all the way down to metal, would it be possible to melt the remaining portion of the brakes, or will the friction of using the brakes not get hot enough for that? This is a hypothetical question, I advise that those who have worn brake pads and or damaged rotors get them replaced. Googlemeister (talk) 20:51, 3 August 2009 (UTC)[reply]
If you're braking metal to metal you can get some quite nasty consequences. Metal conducts heat very nicely so heat gets transferred from the discs to the brake calipers - that will wreck them in short order. You can also boil the brake fluid and wreck your entire brake hydraulic system. Exxolon (talk) 21:35, 3 August 2009 (UTC)[reply]
Yeah - the brakes can only get so hot before the brake fluid boils. Since the gasses that result are easily compressible, you lose all braking force and the brakes will release...in short...no brakes! Assuming you don't crash as a result, there would then be plenty of opportunity for the brakes to cool off - but they'll never recover full pressure after that...and there is a good chance you'd blow a brake hose or something along the way. You'd also gouge the disks (or drums) and disk brakes would probably warp too. SteveBaker (talk) 23:07, 3 August 2009 (UTC)[reply]
Bond Energy
Hello. Under which conditions (STP or SATP) is the bond energy of a single carbon-to-carbon bond 347 kJ mol-1? Thanks in advance. --Mayfare (talk) 00:54, 4 August 2009 (UTC)[reply]
Peter Pan Syndrome - refusing to heed written laws or just societal norms?
Reading the article in our link on the above, I was curious. When People refer to this, are they talking about people who refuse any type of restrictions, especially legal ones? Or, are they talking mostly cultural ones, not wanting to take the responsibilities that adults generally do.
What brought this up was a monarch - Ludwig II of Bavaria whom I had heard elsewhere might been like this (I hesitate to use 'suffered" since it's not an actual diagnosis), because of the fantasy world in which he often seemed to live. Although, I imagine just "living in a fantasy world" isn't the only criteria, it certainly seems to be part of it. Or, does the term generally refer to someone a little more dangerous or odious than just someone "living in a fantasy world"?209.244.30.221 (talk) 01:08, 4 August 2009 (UTC)[reply]
In a social setting (i. e. not a medical one), I have only ever heard this term used to describe men who never seemed to be interested in taking on adult responsibility. (Please note that I am not suggesting that this only happens to males, but simply that "Peter Pan" is usually applied only to males.) I have never heard the use to mean anything illegal or odious, unless the idea of perpetual childhood is an odious one. Usually it is women making the complaint, and it is a complaint. // BL \\ (talk) 01:36, 4 August 2009 (UTC)[reply]
As our article says - this is a "pop-psych" term - it's not a proper medical term with a hard definition. So what do people mean when they use it? Well, it's just some vague concept that an adult behaves like a kid. Different people are bound to use the word in different ways. SteveBaker (talk) 03:30, 4 August 2009 (UTC)[reply]
^Dewey K, Heinig M, Nommsen L (1993). "Maternal weight-loss patterns during prolonged lactation". Am J Clin Nutr. 58 (2): 162–6. PMID8338042.
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