Wikipedia:Reference desk/Archives/Science/2011 November 9

Welcome to the Wikipedia Science Reference Desk Archives
The page you are currently viewing is an archive page. While you can leave answers for any questions shown below, please ask new questions on one of the current reference desk pages.

November 9

Why can't you watch 3D movies on a regular television?

What makes the illusion of 3d impossible on a normal screen? Quest09 (talk) 01:32, 9 November 2011 (UTC)

You can watch 3D movies on a normal screen if you have the right tools. Going old school, you can get some of those red/blue glasses and watch a movie done in red/blue 3D. No problem. Though it never caught on, there was a flicker glasses add-on for any VCR or DVD player that used NTSC (the PAL version simply wasn't very usable). Every other frame of the NTSC signal would black-out one side of the glasses. So, the television shows the left-eye image then the right-eye image, back and forth. The glasses flicker left-right-left in sync with the signal going to the television. Again, this is on a regular television. Some televisions on sale right now use that type of 3D signal. It has problems. The image is dimmer since only half the picture is shown to each eye (solution, auto-increase brightness in 3D display mode). There is noticeable flicker in bright white horizontal lines. Fancier sets have a "flicker fixer" mod that bleeds some of the bright horizontal lines to the surrounding image to limit the flicker. -- kainaw™ 01:43, 9 November 2011 (UTC)

See also 3D film and Stereoscopy. There are many different techniques and some of them work on a normal TV. PrimeHunter (talk) 01:51, 9 November 2011 (UTC)

If you watch motion such as a pendulum swinging back and forth on a B&W TV, and have a dark filter such as a sunglass lens over one eye, there will be a powerful illusion of motion in 3D, caused by the delay of perception of the darker image. See Pulfrich effect. It is amazing! It has been used on lots of TV shows to create a 3D effect. Edison (talk) 06:04, 9 November 2011 (UTC)

The problem with glasses-less 3D is that you need to have a very narrow viewing angle over which the effect will "work". You can send a normal TV signal which can encode a 3D image which will look to be in 3D, but only for someone sitting directly in front of the screen, and only if they are at the correct distance; people viewing from another angle or distance will see garbage. You do this by presupposing the viewing angle and distance and then encode the 3D image specifically for that angle and distance, viola: natural 3D on a 2D TV screen. This is called Autostereoscopy, and our article covers a few known methods of making it work. However, because of the impracticality of this, it only works in limited cases; this is basically how the Nintendo 3DS works; because of the small screen and the fact that everyone uses it roughly the same way (you hold it in your hands, at comfortable arm length, and centered in front of your field of vision). This means that just about everyone will be viewing the device within the tolerances that autostereoscopy needs. With a standard livingroom TV set, however, there's just too many variables to make a working 3DS-style three-dimensional TV screen. --Jayron32 06:19, 9 November 2011 (UTC)

Basically you need a mechanism to deliver a different image to each eye. Obviously the TV can do red/blue 3d where you show the two images in different colors and then put colored filters over your eyes. But other techniques will require special equipment. Your average TV is not designed to display two completely separate full-color images at the same time. APL (talk) 07:24, 9 November 2011 (UTC)

A typical 3D-TV isn't designed to display two completely separate full-color images at the same time either... Theoretically, any TV with any refresh rate can "handle" 3D. But you do still need to alternate what's displayed on a screen between what's supposed to go to the left and right eye, and then have something to block the image from the other eye. If you want autostereoscopy or polarized though, you can't achieve with a typical TV. --Wirbelwindヴィルヴェルヴィント (talk) 19:15, 9 November 2011 (UTC)

Cylindrical tube elastic deformation?

Suppose a cylindrical tube with a wall thickness of t, external diameter d, with a length of L exposed to a force of F at the middle (L/2) is made of a metal X. How does one calculate how much the material will move by the elastic deformation? I looked at the elastic module article, but didn't get it ;) Electron9 (talk) 03:26, 9 November 2011 (UTC)

This looks like a hard problem to solve analytically. The shape of the contact area between the tube and the external force matter a lot. (Consider force F applied by the blades of a bolt cutter, vs. the same force applied by a vise.) To the lowest order and in the limit of thick walls (t~d/2), the compression deformation would be on the order of (F/lE) where l is the length of the contact patch and E is Young's modulus of the material of the pipe. For more precise results, you may need to find a good book on solid mechanics.--Itinerant1 (talk) 03:54, 9 November 2011 (UTC)

No good book available at the current location. The picture above is just for illustration of pipe, the cutter is just clutter. The pipe in question would be attached in the ends and the load is a human hand grabbing the middle (worst case). I'm curious to know if it would bend enough to feel unstable. Hopefully it won't be permanently deformed (another calculation). Electron9 (talk) 04:16, 9 November 2011 (UTC)

OK, then that's a very different problem, it is called "beam deflection", there are multiple online calculators that can do calculations for you, but right now I can't find the one that matches your needs precisely (most will do calculations for a beam that is attached at one end, or for a solid beam on two supports). Google "hollow tube beam deflection calculator". --Itinerant1 (talk) 04:53, 9 November 2011 (UTC)

Using Euler–Bernoulli beam equation you will find that the deflection is equal to (F*(L/2)^3)/(3*E*I) given that E is the young modulus of the metal and I the Second moment of area. You can assume that I=Pi*d^3*t/16 if d>>t. Notice that it doesn't matter how long the entire cylinder is (here L), the only thing that matters is the distance between the point where the cylinder is attached and the point where the man is grabbing it (here L/2 but you could replace it by a new unknown called x for example).--Franssoua (talk) 15:09, 9 November 2011 (UTC)

Red Arrows Accident 8 Nov 2011

What was the probable cause of the unfortunate accident for the Red Arrows team with an ejector seat at RAF Scampton recently? It seems that the pilot ejected on the ground but the aircraft did not suffer an emergency such as an engine explosion, when the pilot would have deliberately ejected. So it looks like accidental ejection with the canopy in place, which killed the pilot.Pensioner.bsc (talk) 04:01, 9 November 2011 (UTC)

I'm inclined to agree with the sentiments expressed in this BBC News article, by Gp Capt Simon Blake, from RAF Scampton: "It would be inappropriate to speculate on the cause of the incident until that inquiry is complete. The investigation will determine the facts." Nimur (talk) 04:16, 9 November 2011 (UTC)

I don't see anything wrong with intelligent speculation, so long as we are not attempting to blame anyone. There are plenty of jet pilots, aircraft technicians and ejector seat designers around who could shed some light, no reason to take refuge in official jargon "it would be inappropriate to speculate" etc. Pensioner.bsc (talk) 03:20, 10 November 2011 (UTC)

Isn't the ejector seat designed to punch through the canopy? 67.169.177.176 (talk) 05:26, 9 November 2011 (UTC)

I don't believe so, the canopy usually jettisons using explosive bolts before the seat ejects.. (EDIT)In fact, Ejection_seat#Egress_systems seems to confirm this. Vespine (talk) 05:30, 9 November 2011 (UTC)

There are also punch-through type seats, as Ejection_seat#Egress_systems mentions. I find some mentions on the web that the plane type involved in the accident indeed has a punch-though seat. 88.112.59.31 (talk) 07:31, 10 November 2011 (UTC)

But then how was it possible for the pilot to sustain fatal injuries from contact with the canopy, or indeed to make such contact in the first place? 67.169.177.176 (talk) 00:18, 11 November 2011 (UTC)

Last year a number of RAF Hawks were grounded due to faults found in one plane's ejector seat.[1][2] --Colapeninsula (talk) 11:30, 9 November 2011 (UTC)

2005 YU₅₅

How much time did the asteroid 2005 YU₅₅ spend at a distance from Earth that is less than the distance to the moon? (I'm crudely guessing about six or seven hours.) Michael Hardy (talk) 04:23, 9 November 2011 (UTC)

Well, our article 2005 YU55 has a nice animation. Using some screenshots, I've ascertained the asteroid crossed the moon's orbit at close to Nov 8.8 and 9.2, (I'm assuming that number is the date) which makes 0.4 of a day or about 9.5 hours, that's pretty rough but I'd be confident within +/- one hour. Vespine (talk) 04:47, 9 November 2011 (UTC)

How come NASA has radar images but no optical images? There should be scads of telescopes larger than the minimum 6 inch objective said to be needed to see the thing. Why can't large telescopes such a Hubble or ground based telescopes move fast enough to image the asteroid? Radar traditionally just provided a dot showing the range and bearing to a target, not the somewhat fuzzy images of the 6 frame movie of the asteroid. It's passage was a disappointment in terms of the imagery, so far. Edison (talk) 05:58, 9 November 2011 (UTC)

I'm not sure how many scientists would have been willing to give up their spot on the waitlist (which can be months or years long) for such telescopes to look at something as relatively common as an asteroid. 72.2.54.34 (talk) 16:44, 9 November 2011 (UTC)

Well, so far no one actually knows the answer. My crude guess was based on glancing at that same illustration, plus the fact that I read "somewhere" (if you'll pardon such language) that it was moving at about 29,000 miles per hour relative to the earth. It looked from the picture as if the chord of the circle was bounded by about a 60-degree arc, so the distance it traveled inside the moons orbit would have been, very roughly, about the same as the distance from the earth to the moon. If the moon is a quarter of a million miles from earth, that makes about a quarter of a million miles at 29,000 miles per hour, so that's more than eight hours. Looking at my original question above, I must have been thinking about something somewhat differently to get "about six or seven hours". Astronomers are supposed to be really nitpicking about precise calculations, so I'd have thought maybe someone here would know a precise answer. Michael Hardy (talk) 17:25, 9 November 2011 (UTC)

Sorry slightly off topic, but in relation to why we have no photos: there's a BIG difference between "seeing" something and imaging it. Anyone pointing a telescope at it would have seen only a little point of light, similar to a star. Using formulas from this page I calculated to actually resolve the asteroid you'd need 0.025 arc second resolution, and Hubble's resolution is 0.1 arc seconds. So even if you used Hubble to take a picture, it would have still been just a dot. Vespine (talk) 21:39, 9 November 2011 (UTC)

An animation of the dot's movement or a long-exposure of the asteroid as a line and the background stars stationary is surely available somewhere. ~AH1 ^(discuss!) 00:11, 10 November 2011 (UTC)

It is. My friend took one, for example. It's also not very interesting because that dot moving across the starry background looks just like a dot, with no detail whatsoever.

To answer the original question, you can easily look up the distance to any astronomical body in the solar system using NASA's HORIZONS: http://ssd.jpl.nasa.gov/horizons.cgi. By comparing the ephemeris of the Moon with that of the asteroid, I found that the asteroid was closer than the Moon for about 9 hours and 53 minutes. If you really insist, you can narrow the search further and get to sub-second accuracy. --140.180.16.167 (talk) 03:14, 10 November 2011 (UTC)

Issues with dog's eye

Veterinary Question removed. Sorry. APL (talk) 07:17, 9 November 2011 (UTC)

While the reference desk does not give veterinary advice, Wikipedia does have an article on nictitating membrane. -- 110.49.227.228 (talk) 10:44, 9 November 2011 (UTC)

Aspirin question

I was watching a pharmacology lecture on youtube and the lecturer said that a normal dose of aspirin (325 or 500mg) is not effective in reducing heart attacks but low dose aspirin is. This makes no sense. Is there a reason for this? — Preceding unsigned comment added by 76.87.49.144 (talk) 08:33, 9 November 2011 (UTC)

Although I cannot answer your main question, and I agree it seems a bit paradoxical, the taking of more aspirin than is necessary to prevent a heart attack will likely increase the chances of a haemorrhagic incident, like a bleeding stroke or gastric lining erosion. Perhaps this was the nub of his remark, where he is talking about effectiveness being the balance between positive and negative outcomes. Richard Avery (talk) 14:39, 9 November 2011 (UTC)

For most drugs, as dose increases efficacy increases up until a certain point after which it plateaus. In other words, doses larger than the recommended dose do not have a greater effect. However, there are some drugs in which a dose larger than the recommended dose has a lesser effect. In these situations, think of it as trying to maintain a balance - either too much drug or too little drug throws the balance off. 148.177.1.216 (talk) 16:43, 9 November 2011 (UTC)

Some drugs also present a dose dependent effect termed Hormesis which might be relevant here. I don't know if Aspirin is known to have such dose dependent effects, but that might be the case. Dauto (talk) 19:57, 9 November 2011 (UTC)

Note that all NSAIDs, including aspirin, have the effect of increasing the risk of cardiovascular disease, as finally came out after safety concerns came up involving Celebrex. But low doses of aspirin are ineffective as a NSAID, but are effective against platelets sticking together. Aspirin is a very very simple chemical compound that messes with a lot of different biochemical activities at differing dosages. (The unifying principle is that thromboxane and prostaglandin are produced by related but different reactions of long unsaturated carbon chains with molecular oxygen by different enzymes) Wnt (talk) 04:58, 11 November 2011 (UTC)

time series

what are the new time series analysis methods? — Preceding unsigned comment added by Nilluras (talk • contribs) 10:03, 9 November 2011 (UTC)

Our article on time series lists various methods of analysing and modelling time series. I think you will have to explain what you mean by "new" if you want anything more specific. Gandalf61 (talk) 10:35, 9 November 2011 (UTC)

suggestion

please dear wikipedia reference desk adminstrator : we have several discussions per day here , but without educational instruments and computer ability techniques ,which can help the mathematical and scientific explanations , are there any more facilities for those proposal, specially graphic ?--Akbarmohammadzade (talk) 10:32, 9 November 2011 (UTC)

Note that there is no administrator dedicated to the reference desk, just very well informed users. I'm not sure what it is that you're trying to ask for, so I can't give you an answer. Plasmic Physics (talk) 10:56, 9 November 2011 (UTC)

I think he's asking if it's possible to add tools for graphical demonstrations or other interactive features to the science reference desk.

I've seen a number of animations as well as plain illustrations on Wikipedia pages, but I don't think Wikipedia/Wikimedia software provides any facilities to author these, and I'm not sure what the Wikipedia policy is if you want to go beyond that and include flash animations or other interactive features from a Wikipedia page. If you're proposing changes that go beyond the reference desk, this would probably be better discussed on Wikipedia:Help desk or Wikipedia:Village pump. Since the reference desk is quite a small and unimportant part of the site, I don't think it's going to get any graphical tools that aren't part of Wikipedia in general. --Colapeninsula (talk) 11:40, 9 November 2011 (UTC)

You can try the Village pump for proposals at Wikipedia.org. ~AH1 ^(discuss!) 00:07, 10 November 2011 (UTC)

Weak acids: shift in equilibrium?

Suppose you have a 1M solution containing both 2 weak acids (HA, HB) ( 1mole of HA and 1 mole of HB in the same 1L solution)

(1) HA + B- <=> A- + HB

If you add more water in that solution, would there be a equilibrium shift in the above reaction? If you think about it in a simple way, there wouldn't be any shift in the equilibrium since K=[A-][HB]/[HA][B-] and all variables decrease in concentration proportionately. But when you think about it, (1) is a mixture of two ionization equilibriums, and both of these equilibriums have a definite shift when you add more water.

Similarly, what would happen with this equilibrium? (BOH is a weak base)

(2) HA + BOH <=> A- + B+ + H2O

Can anyone help me out please?Johnnyboi7 (talk) 11:33, 9 November 2011 (UTC)

Adding water to either equilibrium should not cause a shift to anything. In the first case, you dilute all ions equally, and since the relative stoichiometry for each component is equal, diluting each component has the same effect on the overall equilibrium. This is irrespective of the relative strengths of either weak acid. In the second case, you can think of it in roughly the same terms as the first equation; the fact that water itself appears in the equation as a product doesn't make any difference, since water (as a condensed phase liquid) does not have a concentration-dependent activity, changing the amount of water does not change the equilibrium. Though the situation is different if BOH is a solid than if it is an aqueous-phase molecule. --Jayron32 18:32, 9 November 2011 (UTC)

Adding more water definitely causes higher ionisation. (Le Chatelier's principle.) It doesn't change K, if that's what you mean. If a weak acid is concentrated, most of the acid will be protonated. Add more water, and more of the acid will dissociate (but overall acidity will fall). elle _{vécut heureuse} ^{à jamais} (be free) 12:52, 10 November 2011 (UTC)

Sodium Acetate Trihydrate

I have Sodium Acetate, and I'm trying to create Sodium Acetate Trihydrate. If I mix the Sodium Acetate with water, then boil the excess water off, crystallizing the compound; would that have created Sodium Acetate Trihydrate? Also, a side question, how much does Sodium Acetate Trihydrate sell for on average? — Preceding unsigned comment added by Hockeyplayi (talk • contribs) 14:19, 9 November 2011 (UTC)

If you have crystaline sodium acetate in a jar in your posession right now, what you have is likely already sodium acetate trihydrate. Sodium acetate is hygroscopic and will obtain Water of crystallization from moisture in the air. You may "dry" the crystals by heating the hydrate in a dish over an open flame, or in an oven, or an autoclave, and obtain the unhyrdated crystals; neither is really worth anything on the open market for you. No one is going to pay you retail for an opened jar of sodium acetate; it's pretty cheap just to buy it from Fisher Scientific. --Jayron32 19:44, 9 November 2011 (UTC)

Touching pain

When you hit your head against something, something bangs against your arm, or you drop something on your foot, it hurts. But then people usually rub the area, and the pain subsides a little. Why is that? ScienceApe (talk) 15:00, 9 November 2011 (UTC)

There are several possible reasons. Increased blood flow and stimulation of other nerves from rubbing might mitigate the pain, but I think the main reason is that "all pain is in the mind", so it is the perception of the pain that diminishes. This might be partly because of a distraction effect, or might be a psychological empathy effect. Dbfirs 16:34, 9 November 2011 (UTC)

I found this claim: "Researchers have discovered that gentle stroking activates 'pleasure' nerves beneath the skin, which then reduce the sensation of pain from other nerves."[3] No idea how likely this is to be true. --Colapeninsula (talk) 17:43, 9 November 2011 (UTC)

I had certainly heard that it stimulated localised release of opiates, which would naturally give pain relief. Perhaps this is what the Telegraph is refering to (endorphins or similar)? I don't know enough about the topic to properly evaluate it. 86.163.1.168 (talk) 18:23, 9 November 2011 (UTC)

Oh, I should add that this is the same mechanism proposed for the real pain-relief offered by acupuncture (the only real effect of acupuncture that stand up to testing, as far as I know). 86.163.1.168 (talk) 18:37, 9 November 2011 (UTC)

I believe the most plausible explanation is the one Melzack and Wall proposed -- it is outlined at Pain#Gate control theory. Basically it says that rubbing the area activates a different set of tactile receptors that produce a suppressive effect on the pain receptors. Looie496 (talk) 22:27, 9 November 2011 (UTC)

I'm not sure this would work for the funnybone. ~AH1 ^(discuss!) 00:04, 10 November 2011 (UTC)

Basically because rubbing induces pleasurable stimuli that cancels out the earlier signals sent by receptors from the injured area. Pain is basically a situation report (usually gathered by nociceptors) that tells the CNS how the body is faring. Rubbing after painful stimuli sends a new report telling the CNS that it is now feeling pleasurable stimuli rather than (or in addition to) pain and the brain adjusts accordingly.

It doesn't actually remove the cause of the pain, however, it merely conflicts with it. The sharp pang of pain you first feel is because some signals travel through A delta fibers. Because of their larger diameters, they reach the CNS first. This is followed by the duller but more insistent pain signals carried by the thinner Group C nerve fibers. If the pain is temporary, you won't feel that sharp pang of pain again. By messing with it and having other signals reach the CNS at the same time or earlier, you drown out their messages. It is probably more complicated than that as there is also evidence that the CNS's "map" of the body is involved in experiments that include people dipping their hands in cold and hot water at the same time as well as with "phantom pain" experienced by amputees.-- Obsidi♠n Soul 04:04, 10 November 2011 (UTC)

There's also an element of the placebo effect at play here. Hit your head etc and it will hurt immediately and then the pain will quickly diminish. However an immediate response is to rub or touch it (partly this is a response looking for blood, especially if the site of the injury is not immediately visible). When we do so the pain subsides quite quickly, as it would have regardless, but we still associate the pain reduction with the distraction activity of touching or rubbing, when it was really just the passage of time. For many this is also a learned behaviour which someone (usually our mother) teaches us when we are young. How many other people for example have seen a child conditioned by their mother to believe in the "kiss it better" concept? The kid gets a little bump, starts crying, runs to mum, mum sees it's nothing serious so says "I'll kiss it better", kisses the injured part, kid stops crying. The 'kissing it better' isn't doing anything, but the little kid thinks it is. --jjron (talk) 06:51, 10 November 2011 (UTC)

Monkey Identification

Please can someone identify the species of monkey in this video?

http://video.ca.msn.com/watch/video/adorable-baby-monkey-bath/1gl2llc9z

(A 30 second commercial will probably play before the monkey appears.)

The second question is how big it is likely to grow and how suitable it would be as a pet once it was past the "adorable" stage. Thanks, Wanderer57 (talk) 16:09, 9 November 2011 (UTC)

babymonkeycam -> Tufted capuchin -> "It uses its teeth to strip off the nut's fibrous husk"..uh oh..."The tufted capuchin rubs urine on its hands and feet in order to attract mates and reduce stress."...hmmm. Sean.hoyland - talk 16:52, 9 November 2011 (UTC)

Thank you. The urine habit kind of knocks the edge off the adorableness. Wanderer57 (talk) 17:38, 9 November 2011 (UTC)

This National Geographic article from 2003 may be of interest: The Perils of Keeping Monkeys as Pets. And also The Problem With Pet Monkeys. More 'pro' monkey, Why We Believe Monkeys are Not Pets. Not directly relevant, but the Wikipedia article, Travis (chimpanzee) may serve as a cautionary tale!. 220.101.30 talk^\edits(aka 220.101)-18:47, 9 November 2011 (UTC)

Detectors on U.S. roads

1. Why are most RTD bus stops on a concrete portion of road, when the rest of the road may or may not be asphalt? Is there a sensor beneath the concrete to help keep track of buses?
2. Are the strange detectors being used on major interstate highways used to keep track of semi-trailers/trucks? Examples I've seen include a strangely shaped radar gun-like object placed high above the highway, pointing at one lane. I believe these appear before weigh stations. Another object I've seen are flat rectangular plates suspended over each lane, which seem to be placed directly above metal plates (or concrete again) in the road. I have always assumed these measure the length of the vehicle driving beneath them, and perhaps for keeping track of trucks that did not stop at a weigh station.
3. Exactly what are these detectors emitting, and since they are most likely detecting vehicles, why hasn't there been any complaints from drivers about potential health effects, if any? (People make such a hullabaloo about backscatter x-ray imaging systems, yet no one I know even knows what these highway objects are.) Thanks! – Kerαunoςcopia^◁_galaxies 18:24, 9 November 2011 (UTC)

I suspect for #2 and #3 you are referring to this: Weigh_station#Electronic_weigh_station_bypass. It sounds like it's just plain old radio waves, nothing to be concerned about health wise. It's not an X-ray. --Mr.98 (talk) 19:44, 9 November 2011 (UTC)

Many states have developed traffic volume and speed sensing networks using roadway loops and radar systems mounted by the side of the road [4], called ATR systems. There are no X-rays involved, just low-power radar. The sensors you see at weigh stations are PrePass sensors [5] that relay truck data to the stations. Acroterion (talk) 21:44, 9 November 2011 (UTC)

My guesses about the RTD stops would be that concrete helps to visually mark the stop, and that asphalt is prone to creep over time at locations where there are repeated start-stop actions by heavy vehicles. Acroterion (talk) 21:46, 9 November 2011 (UTC)

Destroyable biometrics

Do there exist biometric authentication methods that the user can permanently disable/destroy? For example: your iris cannot be scanned if you tear your eyes out. I'm looking for less brutal and less detectable methods, though. --145.94.77.43 (talk) 18:39, 9 November 2011 (UTC)

I suppose contact lenses would alter your iris enough to make it unrecognizable, but that's not permanent. I know for sure that the ridges on our fingers can be altered permanently, leaving different fingerprints. — Preceding unsigned comment added by 80.39.16.11 (talk) 19:27, 9 November 2011 (UTC)

Part of the point of biometrics is that it's not easy to disable or destroy, features like finger prints and irises are chosen specifically because they are unique and usually don't change much. Vespine (talk) 21:26, 9 November 2011 (UTC)

Facial plastic surgery would affect facial photograph biometrics (such as are commonly used on passports). According to Fingerprint#Absence of fingerprints some drugs can remove fingerprints, as well as insect stings temporarily (by causing swelling, etc). There are various stories about people stripping fingerprints off with acid, sandpaper, fire, etc, but that might be thought rather drastic. Speaker recognition systems are easy to defeat by putting on a different accent or contracting a wide range of medical conditions in the lungs, throat, etc, which is why these methods are used for purposes where people have an incentive to prove their identity (e.g. telephone banking) but are less good for identifying criminals; surgery to the larynx (e.g. voice feminization surgery) can permanently affect the voice. --Colapeninsula (talk) 10:25, 10 November 2011 (UTC)

Can happiness be measured?

More precisely, can serotonin be measured? Can you take a drop of blood to know what level of serotonin a person has in his brain? Otherwise, how can we know for sure that depressive people or bipolars have a low or disbalanced serotonin level? — Preceding unsigned comment added by 80.39.16.11 (talk) 19:24, 9 November 2011 (UTC)

You may be interested in looking into the work of Martin Seligman who has been a leading researcher in this field for some time. --Jayron32 19:37, 9 November 2011 (UTC)

Thanks, interesting link regarding happiness. But I still wonder if we can measure serotonin in the same way we measure the temperature. — Preceding unsigned comment added by 88.14.195.138 (talk) 20:53, 9 November 2011 (UTC)

Seratonin exists in the blood, but I doubt that would correlate much with measurable changes in mood. Seratonin is not only used in the brain during periods of "happiness", indeed most (90%) of the seratonin in your body is used in regulating motions of your intestines. That's where blood-borne seratonin will come from (read the "In the digestive tract" section of the seratonin article). So, it exists in the blood, where in theory, it's concentration could be measured, but I am not sure that such a measurement would correlate with what you are interested in measuring. --Jayron32 21:17, 9 November 2011 (UTC)

But, someone came to the conclusion that depressed people need more serotonin, or to process it differently, therefore the SSRIs. How can you come to this conclusion at all? Somehow, you'll need a way of measuring it to establish the links serotonin - happiness, or serotonin imbalance - bipolar. How did it come to that? 88.14.195.138 (talk) 21:52, 9 November 2011 (UTC)

See Happy Planet Index.

—Wavelength (talk) 22:31, 9 November 2011 (UTC)

Let me try to answer several points here:

• There is no way to measure brain serotonin levels without putting a probe into the brain. They can be measured postmortem, though, if not too much time has elapsed. One finding is that the brains of people who committed suicide tend to have lower serotonin levels than the brains of people who died in other ways.
• It is wrong to equate serotonin with happiness. It may to some degree be equated with satisfaction, defined as lack of motivation to engage in active behavior.
• The idea that serotonin is involved in mood comes from studies of the effects of serotonin-altering drugs, not the other way around.

Looie496 (talk) 22:40, 9 November 2011 (UTC)

If happiness can be measured in this way, then this presupposes that the electrochemical states of the brain determine the happiness of the person, which may actually be qualitative and subjective, as to compare a quantifiable concept to an unquantifiable one. Dopamine is another important neurochemical, and the two interact. The topics that first come to mind are happiness economics, eudaimonism and sleep disturbance. ~AH1 ^(discuss!) 00:00, 10 November 2011 (UTC)

I don't see why we wouldn't be able to reduce happiness to a electrochemical state. It doesn't mean that different things make different subjects happy. 88.14.195.138 (talk) 00:46, 10 November 2011 (UTC)

Typically humans define happiness as subjective, ie. what the subject themselves feel. The subject may be in an overall happy mood, though upset when thinking about a certain thing, ie. the happiness, if quantifiable, would fluctuate over time. Would the electrochemical state fluctuate just as quickly, Iff the person was capable of changing his or her moods, which is typically not true during a "depressive episode"? Or maybe the electrochemical state is the happiness, but is the person, according to the person-self, aware of this happiness or currently thinking about it? That alone might change the electrochemical state, since the neuron firing pattern would likely also change. We know that bipolar is associated with fluctuating mood in terms of happiness, meaning that the levels of seratonin, dopamine and melatonin may fluctuate in ways different from the average person. Would the happiness then be predetermined, averaged over the lifespan or certain time period, or instantaneously measured? ~AH1 ^(discuss!) 01:12, 10 November 2011 (UTC)

By the way, SSRIs have mostly been found not to be good treatments for bipolar disorder; see bipolar disorder#Medication. They are the mainstay of treatment for unipolar disorder (i.e., pure depression), but for bipolar disorder they are less effective than other drugs and present a danger of inducing a state of mania. Looie496 (talk) 14:32, 10 November 2011 (UTC)

Even if happiness cannot be measured, it may be possible to rank different happiness states. 66.108.223.179 (talk) 23:22, 11 November 2011 (UTC)

Difference between deductive reasoning and scientific theories?

In general, do deductive reasoning (and mathematical theorems) need to be falsifiable? because they don't seem to be in their nature... also, some argue that the existence of god is proved by deduction, if the answer to the first question is no, does it mean that the existance of god doesn't need to be falsifiable?

And even more generally, does science (or do scientists) say that the scientific method is the only way to get information about the world, or does it accept other "parallel" (so-called) methods?(to prevent atheist attacks, I don't believe in God)--Irrational number (talk) 19:46, 9 November 2011 (UTC)

Where to begin?

1. Deductive reasoning is falsifiable. (A counter example falsifies a poorly reasoned deduction)
2. God existence cannot be proven by deduction.
3. The belief in God's existence is a matter of faith so it doesn't need to be falsifiable.
4. I don't think anybody believes that the scientific method is the only valid way to extract information from the world but whatever information is obtained that way may become almost incontrovertible. (Anybody claiming that the earth doesn't revolve around the sun nowadays would likely be considered lunatic).

--Dauto (talk) 20:15, 9 November 2011 (UTC)

Those are your personal beliefs, and not necessarily shared by other people. Many religious people don't agree with 2: see proof of god#Arguments_for_the_existence_of_God, particularly the cosmological argument, teleological argument, and transcendental argument. 3 is rejected by atheists, some agnostics, and many theists. The concept that God's existence is a matter of faith is quite modern, and only became necessary when scientific discoveries began falsifying religious dogma. Before that, God's existence was considered a demonstrable and indisputable fact of life, not as a matter of personal opinion. 4 is also not universally true; see scientism. Scientism is a pejorative term, so I suspect many people subscribe to that belief without labeling themselves as such. Carl Sagan probably thought that science is much superior to superstition, random guessing, or faith. Humanists promote reason and are opposed to superstition or religious dogma. --140.180.16.167 (talk) 20:42, 9 November 2011 (UTC)

Need one's beliefs be shared by all people to be offered as answers on here? The logical arguments for God are recognized by most serious philosophers as pretty weak. Most atheists don't try to make logical arguments against the existence of God and would happily accept Dauto's assertion that belief in God is entirely a matter of faith. (Whether it "needs to be falsifiable" depends on whether you accept that as a basis for belief or not, which is a separate question). I don't see how your assertion that some people are unhappy with a purely scientific outlook on the world affects what Dauto has written. (I think it's a poor argument for the reasons I give below, but I don't think it's strictly false.) --Mr.98 (talk) 20:55, 9 November 2011 (UTC)

I think you're missing 140's point on 4. It seems clear 140 is saying some people do believe the scientific method is the only valid way to extract info from the world, as discussed somewhat in scientism (although 140 also mentioned the term may be pejorative so not actually used by those who believe science is the only valid way to extract info from the world). The fact that some people are unhappy with a purely scientific outlook is more of an aside then the main point 140 was making. Nil Einne (talk) 21:04, 9 November 2011 (UTC)

I think your point #4 is a bit misleading. It's not a good method because the information may become incontrovertible (much less because people who believe to the contrary "would likely be considered lunatic," which is a very socially dependent way of deciding whether something is true). It's a good method because, compared to other methods, it tends to produce useful and reliable knowledge, and tends to, eventually, ferret out poor understanding and nonsense over time. It appears to do that a lot better than other methods of acquiring knowledge (our understanding of, say, physics has increased exponentially over the past few centuries; our understanding of philosophy, literature, or theology, not so much). There's also the "it must be somewhat true because it makes amazing technologies" justification, which is philosophically a little shallow, but hard to argue with intuitively. --Mr.98 (talk) 20:43, 9 November 2011 (UTC)

Deductive reasoning is neither falsifiable nor not falsifiable. Deductive reasoning is a thought process. Statements and conclusions obtained via deductive reasoning may be testable and therefore falsifiable. But sometimes they are not (for example, string theory in its present state is neither). Statements that have been repeatedly tested and withstood all tests become "scientific knowledge".

Most scientists would say that the scientific method is the only known way of obtaining testable and falsifiable information. In principle, no one would discount a theory that "works" even if archangel Gabriel appeared to some scientist and gave him that theory on golden plates. But there were no known cases of that happening.

The belief in God in general is not falsifiable because it is not testable - saying "there is a God" does not come with any concrete predictions. Maybe there is a God who created the Earth in its present shape, fossils and all, in six days, and now he's hiding from us - who knows? There is no way to test that. The belief in a specific god, like the god Zeus who lives on top of mount Olympus, may be falsifiable.

We have one well-known theory called "the Bible" that was supposedly created without relying on the scientific method, it contains a large number of somewhat testable statements, most of them imprecisely formulated, and many of them demonstrably false when interpreted literally. For example, statements that all people descended from Adam and Eve, or that the whole world was flooded to the tops of the highest mountains in the third millennium BCE, are contradicted by modern knowledge of the world. Within the confines of the scientific method, a theory with this many mispredictions would be considered falsified as a whole. Modern "liberal" Christians redefine their theory to exclude anything remotely testable, concede that much of the Biblical content is mythical or inaccurate to some degree, and that makes that theory (and the existence of modern Christian God) non-falsifiable. --Itinerant1 (talk) 21:46, 9 November 2011 (UTC)

Note that the Bible is contradicted by more than just science or the scientific method. There are many internal contradictions between its authors (and editors), which make a literal interpretation logically impossible. The Old Testament contains a detailed and specific version of Israeli history, which historians and archeologists have found to be inaccurate. The New Testament describes the life of Jesus and some aspects of the Roman Empire, which future historians could potentially investigate, although few independent sources about Jesus have been discovered. The "historical method" is not the same as the scientific method, although it's certainly much closer to science than to religious ways of seeking truth. --140.180.16.167 (talk) 23:35, 9 November 2011 (UTC)

When I said that there are ways to extract information from the world other than the scentific method I had other things in mind besides religion. For instance, if I hear a Bob Marley song in the radio I might think "That's a cool beat". With that I have extracted some information from the world - namely the fact that Bob Marley's beat is cool - without the use of the scientific method. (Desclaimer: I have PhD and I am an Atheist). Another point is that yes, true, there are many attempts for proofs of the existence of God by they are all seriously logically flood. Dauto (talk) 23:17, 9 November 2011 (UTC)

But the fact that you consider Bob Marley's beat cool does not rise to the level of a scientific theory. If you were to make a conjecture that "all humans consider that beat cool", then proceed to test it by asking other people what they think, and then make corrections to that conjecture by discovering, for example, that some people are deaf and therefore they don't care for that song, you would be applying scientific method do derive new knowledge. If you were to see a complete model in a dream that predicts whether someone would like that song, that would be a non-scientific way, but it that model would be unlikely to be correct.

I agree that direct measurements of properties of the world do not constitute the scientific method by themselves, but the scientific method is necessary to systematize them and to form testable, valid predictions.--Itinerant1 (talk) 00:04, 10 November 2011 (UTC)

I'm no expert on this topic. Now, scientists generally agree that the concept of God in and of-itself is unfalsifiable – Karl Popper was a major early proponent of falsifiability as an important step in science. God then becomes a matter of personal experience, not testable using methods based on non-anecdotal evidence (the leap between these premises may be a large one). See also Christian atheism and Liberal Christian for some of the ideas mentioned above associated with Christianity in particular. ~AH1 ^(discuss!) 23:54, 9 November 2011 (UTC)

One thing that's worth mentioning is that the scientific approach to knowledge is generally speaking not deductive. It has some deductive aspects to it, but only after acquiring data — which is reasoning by induction. (When Sherlock Holmes says he used "deduction," he was, in fact, using the wrong word. Holmes was an inductionist of the first order, not a deductionist.) The reason is pretty clear if you understand what the terms mean. Deduction means figuring out the specific from the general; induction means figuring out the general from the specific. So classic deduction is of the "Socrates is a man; all men are mortal; Thus Socrates is mortal" sort of thing. Cool, but do you really know that all men are mortal? That Socrates is a man? Where'd you get that information from? The scientific outlook is distinguished by the fact that it doesn't take this sort of thing for granted and is actively seeking out new (usually tiny) bits of data and then trying to figure out the big picture from them, not the other way around. Now this might seem like a rather pedantic point (and maybe it is, anyway), but this was a key break in the ascendence of "natural philosophy" (science) over "philosophy" (of the classical sort, including theology). Hobbes and Boyle had a huge throw-down over this very point in the late 17th century, as chronicled in Leviathan and the Air-Pump. Anyway, I bring this up just to point out that you've lumped deduction and scientific method into the same category, and they're not quite the same thing, and the distinctions matter if you are trying to think precisely and carefully over what it means to use a "scientific" as opposed to a strictly philosophical (or mathematical) approach to the world, much less a theological one. --Mr.98 (talk) 23:58, 9 November 2011 (UTC)

Of the four basic steps of scientific method (Scientific method#Introduction to scientific method, Hypothetico-deductive model), step 2 is inductive, step 3 is deductive. --Itinerant1 (talk) 00:38, 10 November 2011 (UTC)

I thought that a reductionist methodology of science would favour a mechanistic though deductive worldview, considering that it applies to individual cases rather than holistic approach, which I thought favoured inductive reasoning. Also, the Simple English Wikipedia's premise of deductive logic in that it cannot be both raining and not raining is not true, see for example virga. ~AH1 ^(discuss!) 00:41, 10 November 2011 (UTC)

If I understand correctly what you mean, I think that, in many cases, the mechanistic approach hits the brick wall very early in process. For example, genomics involves a lot of inductive reasoning, because it would be enormously complicated to build up a model that explains how genes work and what they do by starting in organic chemistry and deducting your way towards more complex structures. In turn, organic chemistry has inductive elements, because you can't deduce properties of organic compounds analytically from the first principles for any compound that has more than a few simplest atoms, even though the underlying science (quantum mechanics) is well understood - equations turn too unwieldy. And even with modern computers, you can't go beyond a few dozen electrons with any accuracy. --Itinerant1 (talk) 02:00, 10 November 2011 (UTC)

Just want to throw this in, without getting off on a sidetrack - despite what modern liberal or conservative Christians may say or not say, it is worth remembering that ancient Christian writers held that a Christian worldview is not incompatible with reason and science: Origen derided what we now call the literal-minded "fundamentalist" view of the creation stories in Genesis, saying in his work De Principis (In the Beginning), 4.1.6, "I cannot imagine that anyone will doubt that these details point symbolically to spiritual meanings, by using an historical narrative which did not literally happen." And Augustine in his work On the Literal Meaning of Genesis, Book I, chaps. 18-19, castigates ignorant Christians for talking nonsense about the physical universe, and he is open to the findings of "further progress in the search of truth," i.e., science, which is not to be feared because, he says, the meanings of Genesis are spiritual/allegorical, not necessarily to be taken literally. Unfortunately, very few modern Christians of any variety have ever read these works. Textorus (talk) 02:35, 10 November 2011 (UTC)

Oxidisation of Polyethlene

I have read articles mentioning an "oxidised layer". To me this says that PE "Rusts". Is this true? & if so what is the process. Thanking you in anticipation. 82.36.181.113 (talk) 22:54, 9 November 2011 (UTC)

Rust is a form of oxidation but it's not really correct to call all oxidation rust, except perhaps figuratively. We have a section Polymer_degradation#Oxidation that describes precisely the process you've read about. Vespine (talk) 00:48, 10 November 2011 (UTC)

Fantastic, that was the section I was looking. Cheers Vespine. 82.36.181.113 (talk) 05:36, 10 November 2011 (UTC)

"Rust" is the result of a certain form of oxidation which leads to fundamental changes in the physical layout of the metallic surface in question (see corrosion). This is due to the fact that during the process of oxidization material (usually ions) get moved, which breaks up the crystalline structure of the metal. There are other forms oxidization, even among metals, which do not "attack" the surface in this manner. For example, if you oxidize aluminium this results in an even harder surface consisting of a thin layer of aluminiumoxide, which prevents further oxidization. So basically rust is the product of the oxidization of certain metals (like Iron), but oxidization can also result in very different products. Phebus333 (talk) 16:06, 12 November 2011 (UTC)