Wikipedia:Reference desk/Archives/Science/2010 November 18

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November 18

Inconstant red

I've noticed that certain rare reds, such as a certain flower that grows along the banks of the Lehigh, seem to be red beyond comprehension, so as to seem to flicker or shimmer continually. It is not so for plain #FF0000 or any other red shade on a computer. Has this effect been observed and named? Wnt (talk) 09:31, 18 November 2010 (UTC)

I guess you are describing iridescence, which is a form of structural color. 88.112.56.9 (talk) 10:57, 18 November 2010 (UTC)

You might also be noticing a red that is outside the gamut of the RGB color space. Selective yellow is another color that is not representable by RGB. —Bkell (talk) 11:36, 18 November 2010 (UTC)

I thought about iridescence, but the shimmering seems to be a function of the color, not the angle; and I do think it is outside the RGB gamut. Wnt (talk) 01:51, 19 November 2010 (UTC)

Kicking a ball

There are four fundamental forces in nature. Which of them acts on a ball when I kick it forward? To me, the force exerted by me upon the ball does not seem to match the description of any of these forces. --13XIII (talk) 11:15, 18 November 2010 (UTC)

If you'd got to the second paragraph of the fundamental interaction article you linked you would have read: "The four known fundamental interactions, all of which are non-contact forces...". Kicking a ball is clearly a contact force. Having said which, to quote again "Strictly speaking, contact forces are only a useful simplification for introductory physics classes and other applications of classical mechanics. Everyday objects on Earth do not actually touch each other; rather contact forces are the result of the interactions of the electrons at or near the surfaces of the objects.". --jjron (talk) 12:26, 18 November 2010 (UTC)

Well, we can rule out the strong and weak nuclear forces straight away, as there are no nuclear reactions taking place - although the strong force "acts" on the ball in the sense that it explains why there is a ball in the first place, rather than a rapidly expanding cloud of quarks and electrons. The ball experiences a gravitational force, but that is essentially the same before, during and after the kick. So that just leaves the electromagnetic force ... Gandalf61 (talk) 12:37, 18 November 2010 (UTC)

So basically, the ball is kicked because my atoms electronically repel the ball's atoms?--13XIII (talk) 14:46, 18 November 2010 (UTC)

That's correct. Red Act (talk) 15:12, 18 November 2010 (UTC)

You'd generally say the atoms electrically repel the ball, not electronically, even though it's the electrons doing the repelling. Sad, but true. --Sean 15:47, 18 November 2010 (UTC)

It is chemical energy, as per the sliding filament model that makes your muscles contract. Chemical energy is mediated by the electromagnetic force. The electromagnetic force also holds your ligaments et c together and transfers the force from your foot to the ball, rather than your foot piercing the ball. CS Miller (talk) 19:20, 18 November 2010 (UTC)

Since there aren't any chemical interactions between your shoe and the ball, the transfer of inertia is mediated by the Pauli exclusion principle between electrons in molecular orbitals causing elastic collisions. That is more of a quantum electrodynamical effect than an electromagnetic effect, but the force from your foot certainly originates in the electromagnetic chemical energy in your muscles. Ginger Conspiracy (talk) 20:20, 18 November 2010 (UTC)

Chances of getting cancer and age

If you compare the age groups 5-6 years and 59-60 years, which one has a higher incidence of cancer? The former group goes through more cell divisions, could that increase the risk of getting some DNA copied in the wrong way? However, could the later be affected by other factors, like some tendency of old cell to produce faulty DNA copies?Mr.K. (talk) 11:51, 18 November 2010 (UTC)

Adults have a higher cancer incidence by far. I don't have the data for the specific age ranges you are asking about, but according to the American Cancer Society: in the USA the incidence from birth to age 39 is 1 in 70 for males and 1 in 48 for females; the incidence from 40 - 59 is 1 in 12 for males and 1 in 11 for females; the incidence from 60 - 69 is 1 in 6 for men and 1 in 10 for women. As for why this might be the case, the older you are, the more total cell divisions your body has gone through (and hence the more chances for a somatic mutation), and the longer you have been exposed to carcinogens in the environment. This increased occurrence of cancer in older age groups is consistent with the "two-hit" hypothesis of carcinogenesis. --- Medical geneticist (talk) 12:10, 18 November 2010 (UTC)

The age groups were just an example. The older you are = the higher your chance of getting cancer is clear to me. What is not clear is the older you are = the higher your chance of cancer onset. Cancer takes several years to manifest itself, so if a 20 year old is having lots of cell division (more than a 30 years old), his chances of cancer onset could be higher, but this cancer would only manifest itself when he turns 30 (increasing the statistics of this age group). Right? Quest09 (talk) 12:57, 18 November 2010 (UTC)

I think you are over-thinking the situation. There isn't a difference between "your chance of getting cancer" and "your chance of cancer onset". It's the same thing: incidence of cancer. Sure, it's true that some cancers are found serendipitously (the person is asymptomatic and cancer is discovered by accident), other cancers are found at an early stage through screening programs before they manifest significant symptoms, others aren't discovered until widely metastatic. Is this what you mean by "cancer onset?" Certainly the biology of tumors is different, and some childhood cancers are particularly aggressive and progress rapidly while some adult cancers are indolent and progress slowly. But the opposite can also be true. There is no way for us to know when the first cancerous cell arose in any given person's body, so cancer incidence numbers simply measure the age at which a cancer was diagnosed. --- Medical geneticist (talk) 14:00, 18 November 2010 (UTC)

Accumulation of bad copies overwhelming copeing mechanisms that are supposed to kill them? Bad copies of cells that is. Like making a hundred photocopies of a document, each successive one copied from the previous copy? Plasmic Physics (talk) 12:46, 20 November 2010 (UTC)

information technology

How and where can information technology be used? What are the qualities of a good media programme? What are the materials used for information technology e.g generator,contr —Preceding unsigned comment added by Perooy (talk • contribs) 12:57, 18 November 2010 (UTC)

While I don't wish to cast aspersions, this reads very like a series of homework questions. Wikipedia will not do your homework. Instead, you may want to look at Information technology and its associated articles at Category:Information technology which may be of use. If you are having problems with a specific concept, feel free to come back here (or to the Computing reference desk) and ask specific questions. --Kateshortforbob _talk 13:04, 18 November 2010 (UTC)

American winter climate compared with Scotland

Which parts of the US have a winter climate that is about as cold as that of Scotland? Thanks 92.24.187.23 (talk) 13:32, 18 November 2010 (UTC)

Scotland's weather is maritime, which means the temperature (and the rainfall) is heavily influenced by the sea, and (as with the rest of Britain and Ireland) by the gulf stream. The nearest comparison to Glasgow would be the Pacific Northwest, maybe Portland or Seattle (in that it rains a lot, but doesn't really get that cold and doesn't snow massive amounts). Parts of Georgia or Virginia might be roughly temperature comparable (in the winter), but it's different weather and overall a different climate. -- Finlay McWalter ☻ Talk 13:42, 18 November 2010 (UTC)

It seems like Dutch Harbor, Alaska corresponds fairly well to Aberdeen, at least for this time of year. Googlemeister (talk) 15:19, 18 November 2010 (UTC)

Aberdeen is on the east coast, which is colder and dryer than the west. I've seen large patches of snow in June in the Cairngorm mountains. Alansplodge (talk) 15:25, 18 November 2010 (UTC)

Aberdeen, Scotland and Portland, OR is a pretty good comparison. Having lived in both cities the winters were quite similar in terms of temp, number of times falling over of the ice, some but not much snow in the city etc. Sean.hoyland - talk 15:49, 18 November 2010 (UTC)

Thanks. Never mind the precipitation, what states away from the coast would be about as cold as Scotland in the winter? 92.15.5.101 (talk) 17:43, 18 November 2010 (UTC)

You can't ignore the precipitation; it's the presence of water that moderates the temperature. Away from the coasts a continental climate holds, where it's very hot in summer and very cold in winter. For example, right now Glasgow and Omaha are about the same temperature, but compare the climate of the two (Glasgow, Omaha). The average low for Feb in Glasgow is 0C, for Omaha its -10C; they're about the same in November. The only places in North America that are roughly the same temperature as Scotland over the entirety of the winter are the coastal pacific northwest, from Seattle into Alaska. Any given inland place will be roughly the same as Scotland only for a few weeks or so. -- Finlay McWalter ☻ Talk 18:47, 18 November 2010 (UTC)

I'm just wondering where a hypothetical curvy line across the US would be where the mid-winter (early January?) temperature is similar to what you get in Scotland. In the early or late winter it would be warmer. 92.15.13.70 (talk) 20:28, 18 November 2010 (UTC)

Very roughly, you could draw a line connecting Norfolk, Virginia, Memphis Tennessee and Tulsa, Oklahoma and get average daily highs and lows within a couple of degrees C of Aberdeen, but because of the continental vs maritime climate difference between the USA and the UK, the record highs and lows will be a greater span for the US cities. Googlemeister (talk) 21:23, 18 November 2010 (UTC)

Frozen LCD TV

Can LCD TV's be stored in cold tempatures? Can LCD TV's freeze (at what temp.) and will freezing damage the TV? —Preceding unsigned comment added by DB61955 (talk • contribs) 16:05, 18 November 2010 (UTC)

I'm not sure there is a one-size-fits-all answer. Googling for LCD storage temperature suggests some LCD panels may survive freezing. However, a TV will contain other components, such as electrolytic capacitors, whose liquids may not take well to being frozen. For a specific make and model of a TV, consult its user manual for storage and operating temperatures. When bringing electronic devices in from the cold, be sure to allow them plenty of time before switching them on, to allow for condensed moisture to evaporate - here, too, the user's manual is your friend. 88.112.56.9 (talk) 18:02, 18 November 2010 (UTC)

One way that electronic devices fail when stored at very low (or very high) temperatures, or when the ambient temp is cycled up and down a lot, is the breakage of connections, either the microscopic connections inside semiconductor chips, or solder joints where devices are attached to the circuit board.Different materials have different thermal expansion coefficients. Edison (talk) 20:09, 18 November 2010 (UTC)

To illustrate the difficulty of getting an answer to your question, a poster here has been waiting since October 2009 with a question about the operating AND storage temperature limits of a Samsung LCD TV, with no reply yet. Cuddlyable3 (talk) 01:38, 19 November 2010 (UTC)

Maybe the problem is people are waiting for answers after posting in random irrelevant (not associated with manufacturer) blogs nearly one year after that blog entry was posted? A simple search for 'samsung lcd temperature' comes up with [1] which says they recommend 10°C as a minimum operating temperature. (Specifically "When it is used at low temperature of 10°C or lower, response time and brightness are affected in such a way that the proper display may not be obtained.")

If you want more detailed specs, from experience the manual of most products commonly have such storage and operating conditions in their manuals. The blog entry was about the Samsung LN52A580 in particular. Since the blog and TV appears to be directed to the US, a look on their US (but not UK or Malaysian) site finds [2] which has the manuals for the LN52A580P6F. Sure enough from the user manual we find:

Environmental Considerations

Operating Temperature 50°F to 104°F (10°C to 40°C)

Storage Temperature -4°F to 113°F (-20°C to 45°C)

Of course simply asking the manufacturer of the TV your interested in is also likely to be a better bet then a random blog post in a random blog.

Each manufacturer may choose to rate their products differently. For example I earlier looked at some random Sony LCD TV (KDL-40HX701). The manual I got appears to be one of those limited/user friendly ones and it only has 24 pages. I couldn't find a more detailed one for that model on Sony's site but didn't look very hard. Anyway as you may expect it did lack detailed storage and operating conditions but it did at least say "Avoid operating the TV at temperatures below 41°F (5°C)".

In other words it isn't hard. You just have to look or ask in the right place. (In other words help yourself and use a little common sense.)

From these statements, I'll take a punt that as the temperature goes down, the performance changes I guess because the liquid in the LCD changes. Above freezing but presuming no condensation or other such problems I would guess your TV isn't going to blow up but it may not perform as you would expect. But for that reason, manufacturers generally recommend 5-10°C. Actual performance at such low temperatures is likely to vary depending on several factors and is not something you'd expect there to be any real guarantee for cheap consumer TVs.

In terms of storage, from what I've seen most electronics can be stored below freezing. I would guess if they can't this would require greater care to be taken during transport and storage so is something usually avoided. So it's not really surprising that LCD TVs can (at least the Samsung one mentioned above).

In terms of at precisely what temperature the LCD will begin to be irreversible damaged, I suspect that will vary. Finding an answer is probably going to be difficult since manufacturers may not bother to test such details instead just setting minimum temperatures they are sure will be tolerated.

Nil Einne (talk) 18:26, 19 November 2010 (UTC)

trans former

what is trans former? —Preceding unsigned comment added by Pritamcool199 (talk • contribs) 16:41, 18 November 2010 (UTC) (Question reformatted. Richard Avery (talk) 16:56, 18 November 2010 (UTC))

Do you mean Transformer or Transformers or something listed at Transformer (disambiguation)? --Jayron32 16:59, 18 November 2010 (UTC)

Transpired solar collector for sale

I have not been able to find any transpired solar collector for sale.I have sent many emails and have had not one reply.Would you be able to tell me where I could purchase 200 sq ft to see if it will work in my sisuation ? Thanks you, George Jackson 208.127.199.228 (talk) 17:19, 18 November 2010 (UTC)

What do you mean by transpired? Ginger Conspiracy (talk) 19:57, 18 November 2010 (UTC)

A "transpired" solar collector is an unglazed collector that draws a thin layer of air through a perforated absorber; see Solar thermal energy#Heating, cooling, and ventilation. Red Act (talk) 20:23, 18 November 2010 (UTC)

Have you tried just phoning the companies that make transpired solar collectors? They all appear to have phone numbers listed on their web sites, and that way you don't need to worry about things like an overzealous spam filter or something causing e-mail messages to get lost. Red Act (talk) 03:37, 19 November 2010 (UTC)

Type of ruler used to show size of objects

Hi There, What is the name of the type of ruler/measuring device that you see in science pictures where there are squares of alternating color, 1 inch or centimeter or whatever, to make the scale easy to see? Thanks! —Preceding unsigned comment added by 148.66.156.170 (talk) 18:29, 18 November 2010 (UTC)

There doesn't appear to be a standard name for a ruler with a feature like that. There is no mention of such a type of ruler at Ruler#Types, and rulers I can find on the web with that feature are variously described as "[featuring] alternately colored bars"[3], "divided into ... segments by color"[4] or "marked in blocks ... in alternating ... segments"[5]. Red Act (talk) 19:24, 18 November 2010 (UTC)

Maybe a Linear scale? DMacks (talk) 22:04, 18 November 2010 (UTC)

Or a colorful Scale ruler? WikiDao ☯ (talk) 22:16, 18 November 2010 (UTC)

Despite its name a scale ruler is used in making drawings to scale, not for giving the scale in a photograph. I would call the ruler a scale bar, which is what most people (1.6 million hits on google) use for the thing described in linear scale. Mikenorton (talk) 22:32, 18 November 2010 (UTC)

How realistic are the species, descriptions, evolutions, geologics, and so on given at www.metazoica.com?

Per above. Especially, I want to know about the possibility of the listed mammal species/genera/whatever. --Eu-151 (talk) 18:33, 18 November 2010 (UTC)

As per the introduction at the top of this page, "the reference desk does not answer requests for opinions or predictions about future events". Any discussion of Speculative evolution#Future Evolution would require purely speculative predictions about future events. Red Act (talk) 19:40, 18 November 2010 (UTC)

Actually this is a question about a present website rather than a future event. I think it's quite clear that the website involves a rather arbitrary imagination rather than any observed trend. Also, even if an evolutionary trend is observed, it can't be relied upon in a post-human world. For example, under ordinary circumstances new species often diversify from a small, generalist ancestor that is good at dispersing itself; but in a post-human society many exotic animals like lions and pythons and housecats and chickens will be dispersed all over the world to start with. The site seems to postulate both wide radiations e.g. from an elephant shrew and diversifications of highly specialized species like the edentates. It is an open question in biology to what degree wide radiations of species depend on catastrophism, especially where the diversification of mammals prior to the K-T event are concerned, but well known stories like the cichlids in more recent times depend on significant geologic change. It would probably take a rather specific scenario to allow both sorts of events to occur at the same time. Wnt (talk) 02:16, 19 November 2010 (UTC)

thanks, especially pay attention to one Species name in the genus "Procyon" (raccoons)!. But Why or how should carnivorous deer and antelope evolve (see Deinognathids), and is it a external link worthy of inclusion in Speculative Evolution? —Preceding unsigned comment added by Eu-151 (talk • contribs) 11:45, 19 November 2010 (UTC)

nicotine

Why do nicotine patches induce vivid dreams?. My dad was trying to quit smoking many years ago and we bought him patches, and he forgot to take it off when going to bed one night. He said he had the scariest most vivid dreams of his life. I've searched online and found similar accounts from many people, but no scientific reason for it. 92.158.144.48 (talk) 19:35, 18 November 2010 (UTC)

Any substantial metabolic perturbation during dreaming--including indigestion--can produce disturbing dreams, in my experience. Ginger Conspiracy (talk) 19:54, 18 November 2010 (UTC)

You didn't find [6] in your searches? It was the second result for me for 'nicotine dreaming'. Some of the related cites also look relevant. Nil Einne (talk) 19:54, 18 November 2010 (UTC)

What happens if you touch anti-matter?

Will your hand be hurt? AdbMonkey (talk) 20:22, 18 November 2010 (UTC)

How much antimatter? A single positron annihilating with an electron in your body would produce about 1 MeV of energy in the form of photons, which is only about 1.6 x 10^-13 joules, which is negligible. But if you tried to hold an entire gram of antimatter in your hand, you would not survive the experience, to say the least. Red Act (talk) 20:42, 18 November 2010 (UTC)

If you touched one gram of it, the blast would be about equivalent to a 40 kilotons explosion. (The bomb dropped on Hiroshima was 15 kilotons.)

However, modern science doesn't have the capability to create anywhere NEAR that much antimatter. APL (talk) 20:53, 18 November 2010 (UTC)

PET scans generate antimatter inside your skull, so it's not magical annihilation dust. It all depends on how much there is, as Red Act mentioned. --Sean 20:50, 18 November 2010 (UTC)

Pet scans do certainly use positrons, but not anywhere near enough to be called "dust". APL (talk) 20:57, 18 November 2010 (UTC)

So how did the scientists in Switzerland contain it? And how will they study it without it evaporating? Or exploding. AdbMonkey (talk) 21:20, 18 November 2010 (UTC)

Difficult to say without knowing what scientists you are referring to. But the article on antimatter Red Act linked to above has general info in the #Preservation section. Nil Einne (talk) 21:41, 18 November 2010 (UTC)

If you're referring to "the ALPHA collaboration announced that they had so trapped 38 antihydrogen atoms for about a sixth of a second.[24] This was the first time that neutral antimatter had been trapped" it may be helpful if after reading the article Red Act linked to in particular the the parts before my quote, you ask while explaining what still confuses you about how they trapped the antihydrogen. The Nature article the collaboration published that our article uses as a ref may be the best source if you can understand it and have access. But as I expect it's too technical, reading some of the writeups in more general sources may help like [7] [8] [9]. Nil Einne (talk) 21:47, 18 November 2010 (UTC)

Or are you talking about the antimatter from the book and movie Angels and Demons? CERN has a rather well written FAQ about that. -- BenRG (talk) 22:00, 18 November 2010 (UTC)

The short, non-technical explanation is "they used magnets in a vacuum." Magnets are a nice way of containing charged particles without having them touch anything. The same kind of technique is used for trying to contain fusion reactions as well. --Mr.98 (talk) 01:56, 19 November 2010 (UTC)

Magnets without metal?

Is it possible to generate magnetic fields without metal? Googlemeister (talk) 21:13, 18 November 2010 (UTC)

See Plastic magnet. Mikenorton (talk) 21:27, 18 November 2010 (UTC)

Very cool. Googlemeister (talk) 21:51, 18 November 2010 (UTC)

Wind a Solenoid using a Carbon fiber conductor and energize it by an Electric eel. Cuddlyable3 (talk) 01:18, 19 November 2010 (UTC)

If you also use a paperclip you earn the right to be called MacGyver. Rimush (talk) 10:23, 19 November 2010 (UTC)

I would suggest a rubber band since non-metallic paperclips are tough to find. Googlemeister (talk) 15:00, 19 November 2010 (UTC)

I found them easily enough. DuncanHill (talk) 01:45, 21 November 2010 (UTC)

1 in 80 million death

There's an AP Release which reads:

The FDA has estimated that the risk of fatal cancer from the maximum allowable dose would be 1 in 80 million per backscatter screening. And doses from a single scan are considerably lower than the maximum, Kassiday said.

The source for this reads:

General-use systems operating in accordance with this standard produce a maximum reference effective dose of 0.25 μSv (25 μrem) per screening. Therefore, an individual may be screened up to 1,000 times each year without exceeding the annual 0.25 mSv (25 mrem) limit. The associated incremental risk of death is 1 in 80,000,000 per screening.

Is this supposed to be interpreted as for every 80 million screenings, 1 lucky soul will receive a dose of radiation resulting in fatal cancer?Smallman12q (talk) 21:35, 18 November 2010 (UTC)

No. Rather, as noted both in the summary and in the details, a screening at maximum allowable radiation dosage results in such a risk. The summary notes that the scanners do not operate at that maximum (though offhand I see no details as to what dosage they dole out), and so the risk should be further lessened. I'll note as a matter of personal opinion that I'd be more concerned with the possibility that the dosage could be inadvertently increased to catastrophic levels via software than the risk of long-term low-dose accumulation. — Lomn 21:59, 18 November 2010 (UTC)

Just as an aside, the amount of radiation you are exposed to from natural sources while on the airplane is significantly higher than the maximum dose per scan. --Mr.98 (talk) 01:40, 19 November 2010 (UTC)

It would be more correct to say that "1 additional person will develop cancer and die for every 80 million screened", than "1 lucky soul will receive a dose of radiation resulting in fatal cancer". It would be impossible to look at any given cancer case and say that it was the result of getting an x-ray at the airport. However, we can look at a large number of cancer deaths, and see that populations that receive more radiation get cancer at higher incidence than those who receive lower doses. We can even come up with some sort of "marginal deaths per mrem", which appears to be the case here. It's obvious that no one has studied the effects of getting just one extra 25 mrem dose; it would be impossible to draw any Statistically significant conclusions from such a study, even if you could control other exposures to ionizing radiation that accurately over a person's lifetime. It will be interesting to see if (assuming this backscattering thing catches on) research starts coming in 30 years from now looking at cancer rates among frequent fliers who have had lots of these scans, vs. people who hadn't. I suspect that even then, it will be hard to draw significant conclusions; as Mr. 98 pointed out, the act of flying itself contributes a non-zero extra dose of ionizing radiation. Buddy431 (talk) 02:10, 19 November 2010 (UTC)

The TSA and Backscatter X-ray articles are useful in sketching out some of the controversies, for example in skin vs. whole-body exposure. Regrettably the articles on rem and Sievert are woefully incomplete, and some of the most confusing that I've seen on Wikipedia. I will say though that I am suspicious of the idea that the absorbed energy of radiation in joules is the only factor in determining cancer risk, especially when you contrast cosmic rays striking an airplane with a machine deliberately designed to produce (I assume) a larger number of much lower energy gamma ray particles. But I don't know the specifics about this.

Another specific to nail down is how many people are to be subjected to this treatment. I've seen a number of very unreliable looking estimates of how many passengers fly yearly; one claimed over 1 billion. That figure should be nailed down, since it establishes just how many people we propose to sacrifice to the Minotaur yearly; a rough guess of 120 around the world would apply from this data. It would also be nice to have more data about terror attacks; this seems approximately equal to the number killed by terrorists. This is, to my mind, in keeping with an equipartition theorem-based First Law of Natural Disasters, which is that a catastrophic event and its government response are equally dangerous.

It seems like discussion of terahertz scanners seems to have quietly dropped out of sight, and I suspect there's a reason... Wnt (talk) 02:55, 19 November 2010 (UTC)

Looking at the number of terrorist related deaths involving airplanes is useful, but what's really more important is how many terrorist related deaths will these things stop? That's even harder to figure out, especially now when this technology is being introduced. Presumably this technology would have caught the underwear bomber, but he didn't cause any deaths anyway, so we couldn't credit these machines with saving lives in that case. If the List of aircraft hijackings is to be believed, since 2000, there have been only three hijacking incidents that resulted in fatalities, the well known September 11 attacks (almost 3000 deaths)(which fine, was four seperate hijackings) and the lesser known incidents in November 2000 and March 2001 in which 1 (the hijacker) and 3 (one of the hijackers, a passenger, and a stewerdess) were killed. The airport bomb in the 2005 Songkhla bombings (2 killed) presumably could have prevented something like this, although it sounds like any sort of baggage screening could have prevented it (the bomb wasn't on a person, I don't think, but rather in a bag). The 2004_Russian_aircraft_bombings could have probably been stopped by screening; they killed 89. That's all of the fatalities that I could find related to people intentionally trying to cause deaths on commercial aircraft since 2000 (looking at things like List of aircraft hijackings, List of terrorist incidents, and List of accidents and incidents involving commercial aircraft). The 9/11 attacks skew things considerably, but if you put your finger over them, these backscattering x-ray scanners seem awfully expensive for the number of fatalities that they're going to reduce (in financial terms, as well as possible health effects, as well as the goodwill of the public in having TSA guys see them naked). Buddy431 (talk) 03:45, 19 November 2010 (UTC)

Well all the above assumes that these scanners will simply be implemented alongside all existing technologies and procedures, but my guess is that they will replace some current technologies and procedures. The benefit might not be "deaths prevented" but instead it might simply make screening easier, less labor intensive, less technical or prone to error, etc. Vespine (talk) 05:46, 19 November 2010 (UTC)

Yes, but Buddy431 consider that the scanners make excellent Security theater. Indeed, the very fact that they are controversial makes them very well suited as security theater, since such controversy raises the consciousness of them, and thus improves their profile in our minds. --Jayron32 08:09, 19 November 2010 (UTC)

Here's an interview with Bruce Schneier in which he says the new TSA measures "won't catch anybody" compared to the old measures. Schneier has stated that the only two important differences between 2001 and now are (a) maybe the reinforced cockpit doors, and (b) definitely that the passengers have now learned to attack anyone who is a threat. The success of the underwear bomber incident was because in order to get through the old security measures he had to resort to an ignition contraption involving a syringe and 90 minutes in the bathroom; and because the passengers attacked as soon as it was apparent something was awry. (b) also stopped the shoe bomber. Comet Tuttle (talk) 17:57, 19 November 2010 (UTC)

Here's a humorous take on the matter from XKCD. Buddy431 (talk) 17:32, 19 November 2010 (UTC)

How evolution explains the division into autonomic nervous system and somatic nervous system

I know why we are unable to control such things as heart rate for example, but how evolution explains the division of nervous system into somatic and autonomic one (and thus determining what we can control and what not)? Thanx.

Wikipedia has articles about the Autonomic nervous system and the Somatic nervous system. Primitive living things have only autonomic responses. Evolution of consciousness is accompanied by introduction of conscious control of parts of the body. The tradeoff is that conscious control increases the precision and adaptability of the controlled function, at the cost of making it slower. Modern humans have evolved towards an unprecedented level of conscious control and therefore see most animals as relatively quick and stupid. Cuddlyable3 (talk) 01:11, 19 November 2010 (UTC)

At the same time conscious thought is energy intensive - the human brain consumes about 20% of the body's energy already (far higher than in less intelligent animals). The body does not want to waste energy 'thinking' about functions that can be performed automatically, thus evolution would favour continuing to perform functions that can be performed automatically to remain that way, and thus the retention of the autonomic nervous system. --jjron (talk) 13:14, 19 November 2010 (UTC)

In environments that are relatively stable (stable "unchanging" food sources, predation pattern, temperature, rainfall), autonomic responses are all one needs since there are no immediate significant advantages to select for generalists that perform well in quickly changing or unstable environments. A specialist could survive and prosper by being less complicated and having doing the same task better. It's the same idea as with tools, for instance if all you will be doing is either drinking soup or skewering solid foods, you really only need a spoon or a fork (specialists) and something like a spork (generalist) would be less ideal since it does neither task very well. The evolution of more non-autonomic controlled "generalized" creatures such as humans are shown in geological records to have evolved in fluctuating or variable environments where creatures need to quickly adapt and be able to do a bit of everything (although perhaps less well). In the case of heart rate control in the heart's environment (the body), the change of pulse is either (1) detrimental to the survival of the heart and the body or (2) simply does not require complex interpretation of numerous body parameters, which is maybe why it is not selected for somatic response. -- Sjschen (talk) 19:45, 19 November 2010 (UTC)

Some vital functions have both autonomic and somatic means of control, including those regulated by the medulla oblongata. ~AH1^(TCU) 03:39, 21 November 2010 (UTC)

animals natural disasters

How come animals seem to sense natural disasters before they even happen and Humans don't sense natural disasters naturally. —Preceding unsigned comment added by 83.71.80.54 (talk) 23:45, 18 November 2010 (UTC)

Our article on earthquake prediction has a bit about this here. Matt Deres (talk) 00:10, 19 November 2010 (UTC)

They typically don't, actually. It's mostly human power of suggestion. (After the earthquake people say "Hmm! No wonder kitty was acting funny!" never mind that cats tend to have mood swings every couple of days anyway.)

Here's an article that discusses the question as regards to earth quakes.

On the other hand, storms can often be predicted by sudden changes in air pressure, (up or down), even some humans can do that unaided. (Arthritis patients mostly.) APL (talk) 00:15, 19 November 2010 (UTC)

Are earthquakes preceded by low frequency sounds that somehow would not show up as a seismograph signal? Because many people act as if oblivious to very loud low frequency sound. Wnt (talk) 03:00, 19 November 2010 (UTC)

There's probably some of that, but it is far more likely that such an explanation is still more after-the-fact justification for what APL mentions; pets cannot predict earthquakes, but we believe they did, so we come up with justifications to explain how they did it. I am not aware of any actual controlled experiments which show that our pets can predict earthquakes, just a lot of unverified beliefs that they can. I am, of course, willing to be shown wrong, but I haven't seen anything yet. --Jayron32 05:00, 19 November 2010 (UTC)

I'm pretty sure, based on my own personal observations that gulls know when there's a big storm coming. Probably the same way that I can feel/smell it in the air as the skies begin to darken. They mass on the surface of the sea (or fly out seawards in their tens), emitting short, low-pitched, repetitive barking calls - quite different from the standard gull vocalizations that you normally hear. --Kurt Shaped Box (talk) 05:17, 19 November 2010 (UTC)

I'm not sure I would necessarily agree with a statement as strong as "They typically don't, actually. It's mostly human power of suggestion". It's reasonable to expect evolution to have found many different ways for animals to avoid death from natural disasters. It's probably unreasonable to assume that we know anything much about them yet especially when it comes to something very complex like earthquake precursors. At least it's clear is that we're still pretty terrible at earthquake prediction. As for other things, one species of ant in my part of the world is exceptionally good at predicting heavy rain hours before it starts. Thousands of workers, multiple queens and males, thousands of eggs and larvae all carefully arranged into staging groups metres off the ground on vertical surfaces. Very impressive. Anyway, perhaps the IP will find this paper interesting "Earthquake prediction by animals: evolution and sensory perception". Sean.hoyland - talk 07:18, 19 November 2010 (UTC)

I don't think Earthquakes are frequent enough that natural selection would have have worked and shaped behaviour in that manner. Also in the wild, most natural disasters don't kill you except flooding and fire. Earthquakes, for example, only kills you if you have a roof over your head. --85.119.25.27 (talk) 08:48, 19 November 2010 (UTC)

The paper I linked to tries to address those questions. Also, tens of thousands of land animal species have a roof over their heads. Sean.hoyland - talk 09:04, 19 November 2010 (UTC)

Hmm, so for example rats and rabbits could have evolved an escape behaviour (so that not to be burried alive), as well as birds nesting on the coast (to avoid a tsunami). Interesting.

But, like humans, dogs and cats wouldn't have evolved it, because of their lifestyle in the open, an earthquake in the wild would not kill them unless they are very very unluky and a tree fals onto their head. --Lgriot (talk) 13:23, 19 November 2010 (UTC)

Regarding weather, big storms are typically preceded by a drop in atmospheric pressure -- in the days before weather satellites, a barometer was the best tool for predicting storms. Some people with rheumatism can feel a drop in air pressure in their joints. Since birds have hollow bones, there is a decent chance that they can feel a drop in air pressure literally in their bones. Looie496 (talk) 18:12, 19 November 2010 (UTC)

Would it not be possible from evolution that the animals in there enviroment and habitat somehow learned of warning signs like for instance animals know to move up to higher ground if a tsunami triggered by an earthquake is approaching. --213.94.232.102 (talk) 21:26, 19 November 2010 (UTC)

On a related note (some of the items relate to natural disasters like fire), see this CRACKED.com article about "super powers" that some animals have. (Warning: Cracked.com will waste years of your life, only proceed if your boss doesn't value your job outputs anyway.) Zunaid 08:14, 20 November 2010 (UTC)

_{You're warning on wikipedia that another website will waste years of your life?! I'm only hoping by that, that this isn't a waste!}

Some animals have the ability to detect magnetic fields, which may experience some local variations preceding an earthquake. ~AH1^(TCU) 03:37, 21 November 2010 (UTC)