Wikipedia:Reference desk/Archives/Science/2010 April 27

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April 27

Methanol poisoning

This might sound really dumb, but I thought ethanol was the only alcohol used in, well, alcoholic beverages. Since when is methanol used, or is not actually used at all and this incident rose from an accidental addition of methanol, instead of ethanol? Regards, --—Cyclonenim | Chat  00:30, 27 April 2010 (UTC)

The case you refer to appears to have involved the sale of adulterated Waragi. Methanol is not used, for exactly the reason that it tends to lead to illness and death. --Tagishsimon (talk) 00:37, 27 April 2010 (UTC)

Some people may substitute methanol for ethanol to increase alcohol content. Methanol causes blindness in lower doses (about 10 mL are needed), and death in higher doses. Ethanol is not as toxic. Most alcohols naturally contain a little methanol. --Cheminterest (talk) 20:58, 27 April 2010 (UTC)

Snowflake symmetry

Why do snowflakes form exactly the same on all sides? With billions of molecules between the edges, how does water freezing on one side affect the other side? Thanks in advance, --The High Fin Sperm Whale 01:55, 27 April 2010 (UTC)

Note that all crystals tend to be symmetrical, not just snowflakes. However, many do end up "deformed", too. StuRat (talk) 01:58, 27 April 2010 (UTC)

The edges in a snowflake do not affect one another. Rather the same thing is happening on both sides, so you get the same result on both sides. The shape is determined by things like humidity, wind, temperature, altitude, etc. And all of that is more or less equal on both sides. Ariel. (talk) 02:00, 27 April 2010 (UTC)

Then why don't you get a sphere instead of a crystal? --The High Fin Sperm Whale 02:05, 27 April 2010 (UTC)

You do, sometimes, but water is intrinsically a crystal, so if solidifies slowly enough it will naturally form a six-sided crystal. The exact shape of the crystal depends on temperature, humidity, etc. As the flake falls downwards through the weather, growing, sometimes conditions favor different shaped crystals, so you might wind up with a flake that is simple near the center, but complicated near its outer edge. but the entire flake is always in the same weather conditions, so usually, (but not always) all six sides will have formed the same way. APL (talk) 16:10, 27 April 2010 (UTC)

They are not perfectly symmetrical. There are usually lots of asymmetries (which our pattern-matching human brains tend to ignore because we perceive the similarities as greater). The physics of snowflake formation (and symmetry) is complicated and not fully understood. It is clearly some kind of fractal process, though, which produce lots of (approximately) self-similar objects in nature. --Mr.98 (talk) 02:42, 27 April 2010 (UTC)

You can see pictures of snowflakes at Snowflakes and Snow Crystals. -- Wavelength (talk) 02:49, 27 April 2010 (UTC)

According to our snowflake article, "The sixfold symmetry arises from the hexagonal crystal structure of ordinary ice, the branch formation is produced by unstable growth, with deposition occurring preferentially near the tips of branches." You start with a tiny hexagon, and new water molecules, in order to fit in, have to continue fitting in to the crystal, maintaining the hexagon shape. But this doesn't explain why one end of a snowflake is similar to the opposite end of that snowflake, but different from other snowflakes.

Scientific American has an more complete explanation: the snowflake grows slowly, and at the same speed in all directions. The ambient temperature controls how the crystal forms and changes frequently, but (because the snowflake is very small) is always almost precisely the same over all parts of the snowflake.

Snowflake#geometry covers what effects the various temperatures have. Presumably, snowflakes grown in a lab at a constant temperature would all look boring. The shape of a natural snowflake reflects the history of its formation. If two snowflakes stay near each other throughout their formation, they should have a family resemblance. Very cool! Thanks for making me look this up. Paul (Stansifer) 04:59, 27 April 2010 (UTC)

Here is another SciAm explanation (which also points out that it is not entirely symmetrical)... my understanding (from a talk I saw not too long ago) is that physicists hotly debate this particular question, that it is not totally understood yet in a way that everyone can agree upon. --Mr.98 (talk) 13:33, 27 April 2010 (UTC)

FWIW here's a bigger hexagonal mystery. Cuddlyable3 (talk) 13:04, 27 April 2010 (UTC)

Mechanics of motion sensors

According to Hollywood Sign, the famous sign is surrounded by motion sensors that call the police when triggered. Assuming that this is true (the source doesn't say that), how would such a sensor be able to avoid false alarms from large animals (the source warns readers that if they ignore security and try to reach the sign, they're at risk of being mauled by mountain lions) and yet always catch humans? Nyttend (talk) 03:22, 27 April 2010 (UTC)

Motion sensors only detect motion. They can't distinguish between motion by a person and a large animal. Dolphin (t) 04:36, 27 April 2010 (UTC)

I suppose you could design an infra-red motion sensing system to look for a "mostly vertical heat sources", which are presumably human, since we walk on two legs. However, people could crawl on all fours to fool it. StuRat (talk) 05:45, 27 April 2010 (UTC)

If I were building it, I would attach the motion sensor to a video camera. Then I could look ahead of time before calling the police. Also, you can make barriers that work pretty well against animals, but that humans can defeat. Ariel. (talk) 06:01, 27 April 2010 (UTC)

The article Hollywood sign mentions a 1994 installation of a $100,000 security system featuring video surveillance and motion detection. Cuddlyable3 (talk) 12:41, 27 April 2010 (UTC)

Those that have read Dune (novel) will remember the Thumper which had the same cadence, as the Fremen of Arrakis and so was used to distract the worms. Well, back here on Earth, Remote Intrusion Detection Seismic Sensors can be designed to detect the human cadence (between 1 Hz and 3 Hz), and not the higher cadence of four-legged animals. Find a reasonable flat bit of path where the intruder can walk at a regular step ( flat sections are sometimes created to draw intruders to where you want them) and bury a device along there. You can purchase them with radio senders to report back. WP appears to have missed this application out on Seismometer and yet they are becoming quite widely used. Needless to say, the way to pass by undetected is to employ the same technique that the Fremen taught Paul. Here is an external link with more info: [1]--Aspro (talk) 09:04, 27 April 2010 (UTC)

I fixed your link to the Dune novel and not just a hill of sand. Cuddlyable3 (talk) 12:45, 27 April 2010 (UTC)

Thanks. Aspro (talk) 13:25, 27 April 2010 (UTC)

microbes outside earth

Does the search for life on Mars and other space regions include microbes, especially bacteria which live in any extreme conditions? Or is the search meant for humans? - anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 04:15, 27 April 2010 (UTC)

They are definitely looking for microbes. There's little hope of finding humans on Mars, so they don't even look for that. StuRat (talk) 05:20, 27 April 2010 (UTC)

They may have found such microbes. The research is still very scanty due to the extremely small samples, and the very sparce evidence in those samples, but there possibility has not been eliminated in as many as three meteorites found on Earth which originated from Mars. See Mars_meteorite#Possible_evidence_of_life. --Jayron32 05:39, 27 April 2010 (UTC)

SETI activities seek life forms with human-like or better intelligence but generally assume they will not be found living on the planets or moons of this solar system. Lack of evidence has not hindered people imagining fictional Martians some of whom are not very nice.Cuddlyable3 (talk) 12:29, 27 April 2010 (UTC)

Eeek! Martians!

There have been perhaps four serious efforts to test directly for life on Mars - The Viking landers, the analysis of Mars rocks that came to the Earth as meteorites - and the recent Phoenix lander and careful analysis of the Martian atmosphere by the Mars Express Orbiter. Both landers scooped soil and analysed it in test cells specifically designed to look for key signs of life. The results are a little odd.

• The Viking lander did it's tests - and the results of one test were positive! (Check out Viking biological experiments.) According to the criteria the craft was designed to test - it "found life on Mars". However, subsequent thinking on the subject has cast doubt on the findings - there are other ways in which the results could have come about - so nowadays, we have to say that the Viking landers didn't "find life"...necessarily. In other words, the experiments were not designed carefully enough.

• Then we had the Mars meteorites: Allan Hills 84001 in particular was first reported to show fossil lifeforms, to have trapped gasses that could only have come from living things, etc. It was announced that life had been found - they even got Bill Clinton on TV to announce it! But, again, more detailed analysis showed that both "fossils" and the gas evidence could come about in other ways...so again, ambiguous results.

• The Phoenix lander results are no better - at one point in the mission, it was reported that the White House had been alerted by NASA to make an important announcement on major discoveries concerning the "potential for life"...which sounded pretty exciting - right up to the point of the announcement when they basically said that they hadn't found anything very exciting.

• Then we have the anomalous nature of methane in the Atmosphere of Mars. This is a gas that would break down in the atmosphere and disappear. Yet it's still there (See: Atmosphere_of_mars#Methane) - and what's more, it comes and goes. There are no good theories as to why this might be - unless there were lifeforms there generating the stuff.

The problem is evidently that while we do really have some things that make it seem a lot like there is (or perhaps was) life on Mars - there is always another plausible explanation. Since we need to try to remain skeptical, we have to say that life has NOT been definitely discovered on Mars...but neither has it been disproved...yet.

However, it's very clear that 'macroscopic' lifeforms (things that might be visible to the naked eye -- or the many Rover & Lander cameras) are not present. If there is still life there - it's tiny stuff like bacteria.

SteveBaker (talk) 04:47, 28 April 2010 (UTC)

An apostrophe carelessly wielded can yield such nonsense as "The Viking lander did it is tests". Cuddlyable3 (talk) 20:18, 28 April 2010 (UTC)

You can let this bother you, or you can adapt, as I have done: Since Mr Baker tends to write relatively long and detailed responses, simply treat an early improper use of it's as a leading hint for the identity of the author, without having to scroll to the bottom of the post ... nearly as reliable as the signature itself. DaHorsesMouth (talk) 00:29, 29 April 2010 (UTC)

You may be interested in this recent discovery of possible organic matter present on Mars. —Preceding unsigned comment added by AstroHurricane001 (talk • contribs) 23:11, 28 April 2010 (UTC)

Sea blue - Sky blue

Why, at times, is sea-blue darker than the sky-blue when it is just a reflection of sky blue by the sea water? - anandh, chennai. —Preceding unsigned comment added by 125.21.50.214 (talk) 04:28, 27 April 2010 (UTC)

Water is not blue because of reflecting the sky, that's wrong. Water actually is blue, by itself, but so slightly that you need a lot of it to see the color. The deeper the water, the deeper blue it will look. Adding salt, as in ocean water, makes it more of a greenish-blue. StuRat (talk) 05:18, 27 April 2010 (UTC)

Thanks. colour of water is an interesting topic. 125.21.50.214 (talk) 05:51, 27 April 2010 (UTC)

THe colour of the sea here in England is usually grey most of the time, blue on sunny summer days, and rarely green. 78.151.102.119 (talk) 09:14, 27 April 2010 (UTC)

I've seen it purple, but that was in Cornwall not England. DuncanHill (talk) 22:45, 28 April 2010 (UTC)

Since we know the colour of the sea isn't a reflection of the sky, but intrinsic to the water, I can only conclude that the bright blue or dull grey sky must affect the intrinsic colour of the sea by some unknown means. 81.131.28.200 (talk) 11:24, 27 April 2010 (UTC)

Well, everything is darker outside on gloomy cloudy days compared to bright sunny days. Is that what you're talking about? Zain Ebrahim (talk) 11:55, 27 April 2010 (UTC)

In a mirror or on the surface of a still lake viewed at a low angle the reflected sky is as bright as the sky. However some of the light falling on a sea surface is refracted into the water so only a part is reflected towards the viewer who perceives a dark and diffused (because of waves) image of the sky. Colour of water is relevant only to seeing a light source deep in the water. Cuddlyable3 (talk) 12:20, 27 April 2010 (UTC)

The ocean color is partially derived from the skies. On a cloudy day, the ocean appears more gray, and on a sunny day, it appears more blue. It also can be green from underwater plankton which colors it. Water also has a very slight color. The molecules of water absorb certain wavelengths of radiation except blue. Needless to say, there are several reasons. --Cheminterest (talk) 21:03, 27 April 2010 (UTC)

"...the color of the sea isn't a reflection of the sky"

"...it is just a reflection of sky blue by the sea water"

This is a

complicated question.

SteveBaker (talk) 04:00, 28 April 2010 (UTC)

Human-Animal perceptions

If human perception varies from that of animal perception, say for example, in case of 'eye sight,' what exactly is the property (like shape, colour etc.,) of the entity (any object). Should we say that the object is rectangular,spherical etc., according to the human view? - anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 04:33, 27 April 2010 (UTC)

I don't think we particularly care about animal perception, in general. Only animal researchers, trainers, etc., would care, as it affects their jobs. So, if a dog sees a globe, he probably thinks "uninteresting object" and doesn't attempt to classify it further, but so what ? StuRat (talk) 05:27, 27 April 2010 (UTC)

This is an extremely complicated, almost impossible question. The notion of property is a learned, acquired one. You learn what "round" or "straight" or "wavy" means when you see or touch it; you do not know if every human sees it the same way, but every (or almost every) human learn to associate those properties with the same categories. Now, when people study the anatomy and physiology of the eyes, lateral geniculate nucleus, and visual cortex of humans and Old World primates (Catarrhini), it turns out that the structure and function is fairly similar (size and exact shape notwithstanding) across individuals and even across species. This allows one to argue that humans, chimps, and macaques really see those things the same way. Now, cats or rats have eyes and brains that are less similar to ours; birds, reptiles, and fish are further yet; and insects with their compound eyes and ommatidia-lamina-medulla-lobula early visual processing pathway are nothing like the humans at all. Yet bees can be taught to distinguish shapes, and even properties of shapes, such even as the abstract notions of "sameness" and "difference". Do they see the same way as we do? No. --Dr Dima (talk) 07:52, 27 April 2010 (UTC)

An even more puzzling to our hopelessly anthropocentric perception is the question of what qualia (if any) does a rodent have when it "sees" objects with its whiskers (vibrissae); or a pit-viper has when it "sees" objects with its heat sensing organs, or a bat when it "sees" objects with its ears. --Dr Dima (talk) 08:04, 27 April 2010 (UTC)

Well, if you look at the center of a flower you may see a half dome where a bee might "see" a star shape http://en.wikipedia.org/wiki/Bee_learning_and_communication#The_Neurobiology_of_Color_Vision However, that would assume that the bee interpreted the visual information it gets the same way a human with a "bee eye camera" would. IMHO that is highly unlikely. I've linked this story before, but it shows that even an untrained human brain has trouble interpreting shapes. http://nfb.org/legacy/bm/bm02/bm0211/bm021105.htm 99.11.160.111 (talk) 08:57, 27 April 2010 (UTC)

Yes we should OBVIOUSLY say that an object is rectangular, spherical etc., according to our human view. Cuddlyable3 (talk) 12:09, 27 April 2010 (UTC)

"Rectangular" and "spherical" are objective criteria. Even if an optical illusion prevents you from intuiting the shape's true nature, or even if you're blind, you can use tools to measure the shape and determine whether or not it matches the definition of those criteria. APL (talk) 16:03, 27 April 2010 (UTC)

What you describe is not perception; it is measurement and inference. Properties of objects may be, well, objective, but perception is subjective. That is, if you agree with Kant's “Ding an sich” idea. Many philosophers don't, and conclude that fundamentally there is no escape from subjectivity; see e.g. this introduction. Wikipedia, too, has an article on Objectivity (philosophy). --Dr Dima (talk) 18:14, 27 April 2010 (UTC)

Is "Properties of objects may be, well, objective.." that so? We can't be sure even after measurements and inferences. Are measurements and inferences not human perceptions after all? Can science be subjective? If "the object is round," according to humans or anything else, what is the object scientifically? —Preceding unsigned comment added by 125.21.50.214 (talk) 09:51, 29 April 2010 (UTC)

Ambidextrous people

how better are ambidextrous people in terms of intelligence, compassion etc.,than a left-hander or a right-hander, while the ambidexterity is obtained either by natural or acquired ways? - anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 04:50, 27 April 2010 (UTC)

I would suspect you'd find them midway between "right-brain" and "left-brain" individuals, so be able to integrate logic and emotions. StuRat (talk) 05:29, 27 April 2010 (UTC)

While Lateralization of brain function is a real thing (certain tasks predominate in certain areas of the brain) the whole "artsy people are right-brained and scientific people are left-brained" is mostly pseudoscientific bull crap. There's no hard evidence that things like personality or aptitude is connected in this way to "brainedness". --Jayron32 05:36, 27 April 2010 (UTC)

Nope, I'm just as daft as everyone else :-)) 99.11.160.111 (talk) 08:58, 27 April 2010 (UTC)

The Wikipedia article Ambidexterity is mostly about performance in sports. Cuddlyable3 (talk) 12:05, 27 April 2010 (UTC)

Cecil Adams very briefly mentions a study that showed that ambidextrous cats weren't as clever as cats with a definite preference.[2] but without reading the paper he mentions it's tough to say how much Cecil was paraphrasing. APL (talk) 16:01, 27 April 2010 (UTC)

While there is no correlation between being left- or right-handed and much intelligence-related, there is a correlation between being ambidextrous and various problems. [3] I've certainly heard it proposed that left-handed children underperformed historically partly due to being forced to use their right hand, leading to learnt ambidexterity which makes language and reading harder to acquire. 86.178.225.111 (talk) 20:39, 1 May 2010 (UTC)

What is this box?

Resolved

There is a large blue metal box in the office in which I work. The footprint is about 8'x3' and it stands about 6' tall. There is a white box on the outside (maybe 2"x6"x10") with two pressure gauges attached. This white box also has a temperature gauge that goes from 50 to 100 degrees F. There is also an electrical junction box on the outside with a big handle type on/off switch. Next to that is a card which is dated from 1999 which lists when various PMs were done. Notes for those PMs include mentions of replacing or checking tension of belts and greasing motors. In black permanent marker, someone has written on the side of the blue box, "CYMER". I have no idea if the writing is in any way related to the box. The only identifying marking is a logo which I've taken a picture of. I ran the image through TinEye and it didn't come up with anything.

The office in which I work used to be a lab of some sort but it was converted to an office years before I got my current job. None of my co-workers know what this box is and we're all kind of curious what it is and/or what it did. I work in the semiconductor industry if that helps. Anyone know what I've described? I'm putting this question on this desk since the room used to be a lab and this box might have been used for something in that lab. Dismas|^(talk) 08:32, 27 April 2010 (UTC)

I don't know what the box is, but you should also take a picture of the whole box from a number of angles. Did you try opening it? Does it make noise ever? Ariel. (talk) 09:37, 27 April 2010 (UTC)

Cymer, Inc.'s website [4] describes the company as a supplier of excimer light sources for photolitography. Pictures of their equipment suggest it fits the general dimensional description you gave, although none of the pictures on their website shows a blue housing. This U.S. patent [5] may provide some clues to the presence of a temperature gauge and a motor. --173.49.9.93 (talk) 09:42, 27 April 2010 (UTC)

It's been powered off ever since I've been in here (about 7 months). So, no, it's never made any noise that I know of. Considering the "L" logo, I don't think it's a Cymer product. There is nothing to open. The outside is just blue sheet metal. I don't see any access panels. One of the blue panels has had a couple screws removed but considering the 8' length and the fact that I don't have any business poking around in the box, I don't feel comfortable trying to pop the panel off if it will indeed come off. My work has nothing to do with it, so it would be rather embarrassing if I couldn't get it back together again. Dismas|^(talk) 10:03, 27 April 2010 (UTC)

Inside you might find a pre-193nm laser with cooling apparatus as it might be cheaper to leave useless technology in place when there is a radical change in node size as it evolves. Currently the plan is to shift to EUV for manufacture below the 17nm node when the power of EVU is able to match that of current 193nm lasers. Your box probably contains a light source for manufacture of older and larger node sizes of very long ago. I would consider it a showpiece in that case like the MARK I computer at Aiken Lab and care for it like a baby and show it off to friends. Plain vanilla with chocolate chips (talk) 11:23, 27 April 2010 (UTC)

Think we need more info. What is the range of the pressure gauges. It sound like it could be a compressor but compressors often run hotter than 100 deg F. Stand on some steps and see if there are any vents or disconnected pipe work on top. Are the pipes iron, stainless steel or copper? If pipe were at one time attached, there may still be the signs of pipe brackets on the ceiling and walls. Are there any vents, what shape? Any more signs on roof of box. Any inspection or access panels up there?. How are they fixed and are lead seals attached (or bits of twisted wire where they once where). Can you follow the cable from the switch box back to the main switchboard for that floor. It maybe that the electrician labelled what piece of equipment was on that circuit. The company you work for will have a department responsible for looking after the building(s) itself. They will have records of all plant and equipment that is permanently installed. I have found a good approach for eliciting a response from such departments in a reasonable time is too say to them: “Is this large equipment cabinet still used or important? Because we are just about to drill a large hole through it!” A manager or executive officer ( or maintenance guy) should know the name and how to contact this department. Maybe their listed in the internal telephone directory under “Site Management or Estates Management or Work Engineering Department, etc. Do however, steer clear, of involving the PHB. Lastly, I would consider that unknown cabinet could well be a safety issue, for one is just trusting someone else did their job properly and ensured that there are no hazardous materials left in side.--Aspro (talk) 11:10, 27 April 2010 (UTC)

The "L" graphic may or may not be the manufacturer's logo. It seems to communicate something about liquid and temperature. Just a guess. --173.49.9.93 (talk) 12:20, 27 April 2010 (UTC)

Wow, what a bit of history! I work for what became of the company that made that. The "L" graphic is actually a really really old Liebert Corp. logo. If you do a google images search you can see what the latest incarnation was (before they stopped using the logo altogether about 2 years ago.) What you are looking at is probably some sort of industrial chiller, installed to provide cooling for the Cymer device that someone else described. --Jmeden2000 (talk) 14:46, 27 April 2010 (UTC)

Could be -well done! The logo symbol does remind me a bit of a Dewar flask with a thermometer stuck in it (the pressure gauges for first and second stage compression maybe). Anything like that (including a compressor) is going to need loads of cooling though. I'm not going to speculate more without more info – it like clutching at straws. After all, it might just be something very obvious; like the new Doctor has almost fixed the Chameleon circuit and the logo is just part of its disguise – but its still suck at blue! --Aspro (talk) 14:57, 27 April 2010 (UTC)

It was colloquially referred to as the "Liebert Drip" since the company was largely in business to make temperature and humidity control products. The 'thermometer inside the water drop' logo (of various forms) was used until the company was bought by Emerson Network Power and internalized. The device in question, if as the OP states it is indoors and has no visible signs of ventilation, is almost certainly a chiller designed to take a water or refrigerant loop from a condenser type device outside the building, and make cool or chilled water for the supported device. These are very common to find in hospitals, cooling MRI machines, but have a multitude of other applications as well. I bet that the front of the device has three covers with horizontal seams. The covers are probably secured with a 3/8" allen key head and if you twist the two on the top cover it will hinge upward. I am *not* advocating taking it apart, this advice is for qualified personnel only! Ah well, enough babbling, back to work. --Jmeden2000 (talk) 17:17, 27 April 2010 (UTC)

Thanks all! I'll take "chiller" as the simple answer. I got on a chair and looked at the top. It's simply a welded wire cage behind which are several air filters. The panels on the front do indeed have horizontal seams. When I checked the top, I found an allen head T-handled wrench which doesn't have the size written on it but looks to be 3/8". Thanks again!! Dismas|^(talk) 08:19, 28 April 2010 (UTC)

Light-straight line; but how many?

It seems to be a ridiculous doubt. Light travels in a straight line. How do we measure/count the total number of 'straight lines' in a particular 'lighted' region? - anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 10:20, 27 April 2010 (UTC)

Just because something travels in a straight line, does not mean that it is a line. Lux and candela are used to measure light intensity, if that's what you're after, though I don't know much about them. Vimescarrot (talk) 10:55, 27 April 2010 (UTC)

{ec)If I understand our question, the answer is, we do not tend to count such things. An illuminated area is being bombarded by photons. The path of each photon can be considered to be a straight line. If you consider the very smallest point of an area being illuminated, there will be countless straight lines connecting that point to the source of illumination - such as the sun. Trace all of those lines, and you get a solid cone made up of countless lines, with the illuminated point at one end, and, for instance, the sun at the the other end. --Tagishsimon (talk) 10:58, 27 April 2010 (UTC)

The path of each photon is a wave. For example, in the double-slit experiment, the photons each travel through both slits. — DanielLC 14:52, 27 April 2010 (UTC)

The path of each photon is not a wave, it is a straight line. The wave is a time-dependent variation in electric and magnetic field intensities, not a movement in space. --Heron (talk) 17:37, 27 April 2010 (UTC)

I don't think there's any way to argue that photons move in a straight line. Often in special and general relativity people talk about "photons" that are really classical particles moving in straight lines at the speed c. In quantum field theory, though, "a photon" is just a certain amount of energy in the electromagnetic field. Only the total particle number is meaningful. Talking about individual photons is the same as talking about individual liters of water in a river. Do they move in a straight line? It's a meaningless question. -- BenRG (talk) 20:19, 27 April 2010 (UTC)

Is the question "is space infinitely divisible"? 81.131.28.200 (talk) 11:40, 27 April 2010 (UTC)

A true line is an abstract thing with zero cross-sectional area. You could not make holes small enough in two walls some distance apart for a light beam passing through both holes to be reduced to a "line". Questions about how many infinitesimal quantities can add up to a finite quantity, such as how infinitesimal spots lit by lines of light can illuminate an area, are answered mathematically in integral calculus. Before calculus these subjects seemed paradoxical. Cuddlyable3 (talk) 11:47, 27 April 2010 (UTC)

1) Light only travels straight in the absence of gravity. The stronger the gravitational field, the more the path of the light will be bent. (There is an alternate way of looking at it that has the light straight and space-time curved, if you prefer that model.)

2) Light has a dual wave/particle nature. The particle models does have photons of finite size, so there would be a specific, very large, but not infinite, number of photons flying in any given room. StuRat (talk) 13:38, 27 April 2010 (UTC)

Area can theoretically be divided to smallest part up to 2.61223 × 10⁻⁷⁰ m2 (see Plank units). Don't know whether photon in straight line will need more or less than this. - manya (talk) 04:29, 28 April 2010 (UTC)

Objectively, what is the need for an area to be divided (may be infinitely) when the resulting subdivisions are of same properties? It(area) IS divided, fine, it(dividing by straight-line-travelling) is the property of light, fine, but Why?..... Oops, the question now becomes, light travels in a straight line, Why? --- Help me out. - anandh, chennai. —Preceding unsigned comment added by 125.21.50.214 (talk) 10:08, 29 April 2010 (UTC)

penury

Is the a mental disease characterized by penury? Plain vanilla with chocolate chips (talk) 10:53, 27 April 2010 (UTC)

No. Mental disease may lead to penury, but is not characterised by it. --Tagishsimon (talk) 11:00, 27 April 2010 (UTC)

penury noun: a state of extreme poverty or destitution. Cuddlyable3 (talk) 11:34, 27 April 2010 (UTC)

It's a pretty inevitable result of schizophrenia in the US. alteripse (talk) 12:06, 27 April 2010 (UTC)

Only if their family won't/can't take care of them. Dauto (talk) 14:30, 27 April 2010 (UTC)

Or if they don't have medical insurance. 76.103.104.108 (talk) 01:52, 28 April 2010 (UTC)

Only if their only option seems to get treatment, and not to be taught to try to fit in socially even with their illness. ~AH1^(TCU) 23:08, 28 April 2010 (UTC)

Spiders

What is the biggest spider found wild in the UK? Is it rare? If so, what would be the largest commonly encountered spider? I'm talking in terms of legspan here, although it would be nice to know the largest in terms of mass also. Thanks —Preceding unsigned comment added by Alaphent (talk • contribs) 14:58, 27 April 2010

Seems you can take your pick between the Raft spider and the Great raft spider as only an expert can tell them apart. --Aspro (talk) 15:45, 27 April 2010 (UTC)

Asystole and CSI: Miami

Calleigh from CSI: Miami was recently rendered unconscious by respiratory distress incident following smoke inhalation. The episode goes on to portray her in ventricular fibrillation with no (perceivable) pulse, followed by asystole. Eric complains they aren't shocking her, which makes sense, because asystole is a non-shockable rhythm, and then the ER physician slams her in the heart area with a syringe, possibly atropine. She then proceeds to jump up with her eyes open. Completely unrealistic, right? People don't just wake up from asystole. And she still has the endotracheal tube in, yet she's not gagging. DRosenbach ^{(Talk | Contribs)} 17:10, 27 April 2010 (UTC)

I generally don't use CSI:Miami as a reliable source for medical information. I assume that every utterance of every word, whether medical, forensic, or anything else, to be complete and utter bullshit made up entirely for advancing the plot of the show, without any hope that any such statements have any connection to actual real medical or scientific truths, except by dumb luck or pure raw coincidence. The same should be said of every single fictional TV show, from House to Lost to Thomas the Tank Engine. They all have an equal level of reliability with regards to medical or scientific information. --Jayron32 18:17, 27 April 2010 (UTC)

No Jayron, Thomas the Tank Engine has origins in the E2 Class designed by Lawson Billinton in 1913 and is a reliable source on matters of Rail transport. Cuddlyable3 (talk) 19:27, 27 April 2010 (UTC)

No, no...It's not like I can't seem to sneak medical advice out of the astute ref desk patrons and seek out CSI to fill that gap :) Rather, I just find it absolutely amazing that so many errors are made when, clearly, many other sorts of routes of medical happenstance could be utilized by the editor team to advance their dramatic agenda. I mean, I laughed when the CSI: NY coroner announced that a bullet had gone through the right occipital bone, when it's clear that the occipital bone is unpaired, and that mistake could have been eliminated without much disturbance to the plot. So when they make Calleigh's dramatic arousal from unconsciousness reliant on silly medicine when they could have made it reliant on actual medicine...I sense a tinge of arrogance on the part of the editorial team to care so little about reality in a show that focuses on reality. It's not the same as Archie Bunker having said, "Let's stop doing CPR because he's dead!" -- but that's what someone told Flack in CSI:NY last year. Can't they just get with the program? DRosenbach ^{(Talk | Contribs)} 18:32, 27 April 2010 (UTC)

It sounds like the doctor watched Pulp Fiction in a med-school course, 'cause it worked for Uma Thurman too. Concidentally, The Economist magazine has an article this week on the "CSI effect", defined as "the phenomenon in which jurors hold unrealistic expectations of forensic evidence and investigation techniques". That's a little more worrisome side effect. Franamax (talk) 19:02, 27 April 2010 (UTC)

Do you mean the CSI effect? WHAAOE. --Jayron32 19:08, 27 April 2010 (UTC)

Actually more than one. Cuddlyable3 (talk) 19:31, 27 April 2010 (UTC)

I dunno about that last one, it was written by someone with an obvious conflict of interest... Also a quick check with an MD confirms that intracardiac injection is never used nowadays; in the past it was likely epinephrine; and the Pulp Fiction scene at least bears no relation at all to medical reality. (Is it medical advice to say that you shouldn't stab your friends in the chest with a honkin' big needle?) Franamax (talk) 20:54, 27 April 2010 (UTC)

The "penny in the fuse" part of the episode was particularly idiotic, along with the notion that the batty neighbor lady could calculate that the penny was needed to prevent the fuse blowing when the plumber was electrocuted through clean water she sprayed on the floor. How did she calculate that more than 15 amperes would be carried through the water, across the floor, through the plumber to the pipe he was touching? I would estimate far less. And sticking an elongated penny into the FRONT of a fuse was not ever a common (but recognized unsafe) practice in the days of fuse boxes. (I will not elaborate on the "to be avoided" practice regarding pennies and fuses, nor should anyone else). What are the writers smoking when they come up with these plot elements? Edison (talk) 04:51, 28 April 2010 (UTC)

In most such cases they're probably performing under the constraint of "We don't need it good, we need it tomorrow!" 87.81.230.195 (talk) 14:57, 28 April 2010 (UTC)

Good thing that novelists like myself usually get about a year to work on the book. :-) 76.103.104.108 (talk) 05:58, 29 April 2010 (UTC)

Dropping a potato out of a plane

Yes, it's another of those "Never!" bets again. My friend is an amateur pilot, and through a rather convoluted path we got to the (enthralling) topic of dropping potatoes out of planes. She worried it might kill someone; I said this was unlikely (recalling the coins-off-the-Eiffel-Tower scenario). We promptly set off trying to determine (roughly) what would happen.

Our potato is (for argument's sake) a sphere of diameter 5cm and density of 1.6g/cm³ (it weighs ~105g) and we're dropping it from sufficient height that it will achieve terminal velocity but not so much that it might change during the process (freeze, splinter, gain mass from clouds or whatever). From this, we got a terminal velocity of around 8 m/s. So far, so good.

We now knew everything we needed to about the potato, but transferring this into a living/death thing proved tricky. I'd love to have your thoughts on how to model it - the simpler the better, I suspect the answer is unlikely to only just cause death or just not, so exactitudes don't really matter - we just need an answer! :) Thanks, - Jarry1250 ^{[Humorous? Discuss.]} 18:38, 27 April 2010 (UTC)

What does a potato weigh? About 1/4th to 1/2 of a pound? That's roughly 0.12-0.25 kilograms or so. Will an object, somewhat squishy, moving at 8 m/s and weigh 0.24 kees kill someone? Probably not. It has E = 1/2 mv² = 1/2 * 0.25 * 64 = 8 kilojoules of energy. I can't imagine an object imparting 8 kilojoules of energy actually killing someone, unless it hits just right. It would probably leave a nasty bruise, and that's about it. --Jayron32 18:59, 27 April 2010 (UTC)

Quite. Our imaginary "potato" weighed 0.11kg so slightly less than yours anyway. However, it says at HowStuffWorks (not the most reliable source, I know) that 100 foot-pounds in enough. Wolfram tells me 100 foot-pounds is about 136J (?). Which doesn't seem like much. Which worries me. Where am I going wrong? - Jarry1250 ^{[Humorous? Discuss.]} 19:10, 27 April 2010 (UTC)

Sorry. I mistyped. It should be 8 joules of energy. A joule is a mks unit, and I mistook it for a cgs unit. In that case, a dropped potato of only 0.11 kg should impart about 3.5 joules of energy. This is rougly 2.7% of the energy needed to kill you. In other words, it would need to be a large sack of potatoes to have enough energy to kill you reliably. --Jayron32 19:20, 27 April 2010 (UTC)

Of course. It all makes sense now :) Thanks. - Jarry1250 ^{[Humorous? Discuss.]} 19:30, 27 April 2010 (UTC)

(ec) Got some other figures for you, from Cycle, a national UK cycling charity. It seems that bike helmets need to meet a standard of protecting a head from about 65 joules upon impact with a rounded anvil. I know it's outside the potato/plane box, but I would suppose that realistically, a potato dropped from a great height would be travelling almost straight downwards due to air resistance and so the head would be the most likely impact zone. Cutting it short: it looks like a single spud is an order of magnitude too low to fracture someone's skull. The article states, for comparison, that an estimation of the energy of a fall onto flat tarmac from stationary is about 75 joules. Brammers (talk) 19:37, 27 April 2010 (UTC)

As a pilot myself, I would like to point out that the Federal Aviation Regulations explicitly forbid dropping any object from an aircraft in a manner that creates a hazard to persons or property. The FAA is pretty strict on this one, so it's far better not to drop it at all, as you cannot be 100% sure that there is nobody/nothing in the potential path of the potato. Falconus^{p t c} 19:18, 27 April 2010 (UTC)

Haha, don't worry, we weren't going to try it (although, as my friend rather humorously pointed out, I really ought not to be the one worrying). And we'd be under the CAA anyway, but meh, they probably have the same rules (I'm not a pilot myself). And of course the above omits the small chance it did perchance do serious damage, so not point relying on it. But I'm happy now. - Jarry1250 ^{[Humorous? Discuss.]} 19:30, 27 April 2010 (UTC)

Well they are not suppose to dump stuff out of the aircraft, but sh*t does happen. We hear things like this every now and then. See Blue_ice_(aircraft). --Kvasir (talk) 19:54, 27 April 2010 (UTC)

Impact on the head, pshaw, what sort of imagination is that? How about if it knocks the gun out of a soldier's hand as he's about to ambush an enemy, who hears the noise, turns around, and shoots him? Or it splatters over someone's windshield, blocking the view while they're on a twisty road, and they drift into the oncoming traffic? Or it lands next to a vicious dog or a poisonous snake, which looks around and fatally bites the nearest human? Or it drops into a tornado and is accelerated to 10 times its previous speed and then hits someone on the head? Or it knocks the camera out of someone's hand and breaks it, preventing them from taking the photo which would have been confirmed their testimony which might otherwise have been considered dubious, thus allowing a murderer to plead guilty to a lesser charge and be sentenced to only 15 years in prison, after which he commits another murder? (Insert butterflies here.) What about that, hmmmm??? --Anonymous, 20:55 UTC, April 27, 2010.

I was going to mention those, but decided on "the small chance it did perchance do serious damage" in the end, very much in the spirit of WP:BEANS. Heh. - Jarry1250 ^{[Humorous? Discuss.]} 21:00, 27 April 2010 (UTC)

Mr./Ms. Anonymous, whoever you are, you should be a writer of detective fiction. BTW, why don't you sign your posts so that literary agents would know who you are?  ;-) 76.103.104.108 (talk) 01:57, 28 April 2010 (UTC)

8 ms^-1 for the terminal velocity? That's not all that fast. Gravity is 9.8 ms^-2 - so your potato will get pretty close to that speed in about 2 seconds. You don't have to be all that high up to get that kind of speed - a third floor window would probably be enough. Now all you need is a "human analog" (to use a handy Mythbuster's phrase). I suggest a large watermelon. So find a nice high window - overlooking an enclosed area - stick a handful of representative melons out there and haul a few bags of potatoes up three or four floors. It may take quite a few drops to get a potato on target - but it'll get you an answer in an hour of trying. You can add some other interesting destructible objects too. Tell us what happens! SteveBaker (talk) 03:15, 28 April 2010 (UTC)

Don't forget to invite friends and have a cookout with the potatoes and watermelon. Ariel. (talk) 05:09, 28 April 2010 (UTC)

Railguns on ships

I took the info from this Cracked article, railgun, speed of sound, and a random ship: Spanish aircraft carrier Principe de Asturias.

While discussing the enormous destructive potential of railguns as mentioned in the Cracked article with a buddy, he asked if the sheer force of firing a slug at mach 7 wouldn't roll the ship. Railgun says that the slugs are 3.2kg, and seven times the speed of sound is 5,376 mph. A ship like the Principe de Austurias weighs roughly 16,000 tons, which would be 16,000,000kg, right? Accelerating a mass 5,000,000 times greater than this 3.2 kg slug would accelerate it 5,000,000 times less...meaning...it would accelerate 0.0010752 mph in the opposite direction that the railgun fires.

...Is all of this right? I'm asking on Science not Maths because I imagine most good scientists would be able to think their way through these calculations fairly easily, and I'm also after other factors that I might not have thought of. Vimescarrot (talk) 19:58, 27 April 2010 (UTC)

Note: The gun is not being fired at the ship, it's bolted to the deck and firing from the ship. Ran this scenario past a friend and he didn't realise, so I thought I'd best mention it. Vimescarrot (talk) 20:09, 27 April 2010 (UTC)

Hey, when I model the experiment in my mind, I come up with the complication that you can't simply take the whole weight of the vessel and use it as a denominator to find the ship's acceleration. The question is not 'will the ship move sideways in the water', but 'will the ship roll' (i.e. will the top of the ship move relative to the bottom in the vertical axis'). In this case, you can only use a fraction of the vessel's weight as the denominator. I think the calculation must be complicated but I would suggest that the majority of the ship's weight is low down, to prevent it from capsizing. The weight around the centre of gravity will be accelerated less, but the surface of the ship will be accelerated more because it is lighter and is some distance from the fulcrum. Nonetheless, it's still probably only a fraction of an mph, because you also need displace all that water in order to move the... what's it called... stern? --Seans Potato Business 20:24, 27 April 2010 (UTC)

Err, forget roll for a moment. How are you going to stop the gun's recoil from splinting the vessels structural joints?--Aspro (talk) 20:48, 27 April 2010 (UTC)

Time to break for a photo of the Iowa

An Iowa class battleship fires a projectile of around 1000 kg at about 820 m/s, which (if my dodgy math is right) is a muzzle energy of 336 MJ per projectile, and thus the same amount of recoil energy that has to be dissipated by the vessel. The numbers Vimescarrot quotes amount to 9 MJ for the railgun. And the Iowa has 9 such guns which it seems it can safely discharge simultaneously; that's 3TJ of recoil. -- Finlay McWalter • Talk 21:07, 27 April 2010 (UTC)

Use springs to prevent it from splintering.--Cheminterest (talk) 21:10, 27 April 2010 (UTC)

The 'force' being applied to the projectile is via the use of different principles of physics. So first one need to establish the nature of 'recoil' as it applies to a mass being accelerated in this fashion – yes? --Aspro (talk) 21:20, 27 April 2010 (UTC)

No. A force is applied between two objects, pushing them violently apart. Simplistically, it's an elastic collision, with half the energy used to imply each object with momentum, by Newton's third law. It doesn't matter whether the force comes from an exploding gas or a powerful magnetic field. In practice the process isn't perfect, so the collision is really elastic (stuff gets hot) and with cleverness you can spread the recoil energy around, but it doesn't go away because you're using magnets not cordite. -- Finlay McWalter • Talk 21:38, 27 April 2010 (UTC)

Another concern is resonance. I'd assume they will shoot more than one of those projectiles during a battle, so then the Q is how long they wait between each. If we assume that the rail gun is above the CG for the ship, then the ship should roll somewhat, then roll back the other way, and back again, less with each roll and counter-roll due to frictional effects.

If the time period between firing slugs is the same as a full roll-and counter-roll, then you would get an increase in magnitude with each new shot, due to resonance. I doubt if it would add up to anywhere near enough to roll the ship, but it might be enough to adversely affect accuracy. Of course, all these issues also apply to conventional shells, so I'm sure they already have strategies in place for dealing with the problem. StuRat (talk) 22:30, 27 April 2010 (UTC)

This chapter says that there is a recoil brake (which seems to be a gas cylinder damping arrangement - see fig 5B21) which it likens to a dashpot, which both spreads the recoil impulse delivered to the ship out over time (to lessen the otherwise shattering shock) and to dampen the oscillation. I'd imagine it'll also reduce the noise inside the ship. If they didn't have this, and instead had the gun firmly bolted straight to the main structural members of the ship, I guess it would feel like being inside a giant gong. -- Finlay McWalter • Talk 22:45, 27 April 2010 (UTC)

The scary bit is where they're going to get all the power to run this thing. Railgun#Railguns as weapons talks about a 64MJ muzzle-energy weapon. This General Atomics press release compares the size of the capacitor array to drive a smaller gun, and from that it looks like the whole arrangement (capacitor discharge and railgun operation) is less than 50% efficient (the railgun article also talks about the guns getting very hot due to this inefficiency). So that 64MJ gun will need something like 128MJ in the capacitors to run it, and railgun talks about a fire rate of 10 per minute, which is once every six seconds. To store 128MJ in six seconds they'd need a power supply of 21 MW. The twin Rolls-Royce Marine Trent powerplants they're planning on putting into the (possibly one-day railgun capable) Zumwalt class destroyer put out 78MW, so they'd be using a quarter of the ship's entire power to run one gun (and that assumes they can actually run the generators with the gas turbines at full, and have enough bus capacity to shift that power around). Still, with other power-hungry things like free electron lasers and Electromagnetic Aircraft Launch System (122 MJ) it looks like the US navy is going very capacitor-heavy. -- Finlay McWalter • Talk 23:19, 27 April 2010 (UTC)

So put the railgun on a ship that has a nuclear reactor for power supply. Destroyers are probably too small, but a cruiser could probably have one. Googlemeister (talk) 13:28, 28 April 2010 (UTC)

Sure, you could do that. But a Zumwald already costs getting on for 6 billion dollars, without railguns, nuclear reactors, or death rays. A cruiser like Ticonderoga is about four times the displacement of Zumwald; at that rate the US Navy would be able afford to field only a handful of ships. Railgun has to compete against TLAM for the shore-bombardment role, and while shot-for-shot TLAM is pricey the incremental cost of adding TLAM to existing vessels is pretty moderate and it's flexible enough to fit to Ticonderogas, Iowa, Arleigh Burkes, and submarines. -- Finlay McWalter • Talk 15:21, 28 April 2010 (UTC)

The destructive force of a railgun is given by its energy, which is proportional to the square of velocity. The roll-the-ship effect, however, is given by momentum, which is only linearly proportional to velocity. A 3 kg slug moving at 7 times the speed of sound just doesn't have enough momentum to matter to a thousand-ton ship. You wouldn't feel more than a small shudder. It's curious how poor people's intuition is about things like this -- in movies you often see somebody hit by a bullet who is knocked backward or even stopped in midair. Ridiculous! It happens, I think, because most people's intuition doesn't properly differentiate between kinetic energy and momentum. Looie496 (talk) 05:21, 28 April 2010 (UTC)

I think that pretty much covers everything I was after. Cheers Vimescarrot (talk) 13:03, 28 April 2010 (UTC)

The US Navy has a habit of spending billions on ships who's roles could be filled much more cheaply. For example the new Littoral combat ships fulfill a role that could probably be done better by a tug boat with a Bofors 40 mm. Any big ship could easily handly the recoil from a railgun. They already have fully automatic 5-inch guns that produce about the same recoil yet constatnly--92.251.243.109 (talk) 21:58, 28 April 2010 (UTC)

% of water when raining

How fast would it have to be raining in order for a person to drown from just walking around unprotected? I thought about figuring out what % of the air is replaced by water when it is raining at 1"/hour and then scaling it to a point that a human can not survive, but have not been about to figure out the first. Googlemeister (talk) 21:18, 27 April 2010 (UTC)

It's going to be hard to calculate properly (accurately) because the terminal velocity of rain depends on how much rain there is. According to this, 9m/s seems to be a good number to work with. The equation you want is: 1inch/hour / 9m/s = .000000784 = %.0000784, which is the fraction of the air that contains water. You'd need 1,275,590.55 inches per hour to have the air be solid water (if you convert the units, 9 m/s = 1,275,590.55 inches/hour), but a person may drown in less than that. Ariel. (talk) 22:15, 27 April 2010 (UTC)

it depends on how they face when they breath, too. The rain water in the air isn't randomly distributed, it's in discrete droplets falling downwards. Someone bent over in the rain doesn't inhale much water, but someone staring at the sky might inhale a good deal more. APL (talk) 22:29, 27 April 2010 (UTC)

Is this assuming that it's raining everywhere on Earth at the same time? As the clouds taper to an end, and there is no rain, wouldn't the rainfall adjacent to this circumference run off into the area where it wasn't raining...I mean, does your 1.3M inches an hour take this into account? DRosenbach ^{(Talk | Contribs)} 03:29, 28 April 2010 (UTC)

The 1.3M inch/hour figure is an estimate of how much water would be falling per area if what was falling was solid water coming down at 9m/s. (Of course in that case terminal velocity in air would not really come into play. The velocity would instead be limited by how fast the water on the ground was moving out of the way). Run off isn't an issue until after the water has hit the ground. Otherwise we're just talking about the conditions for flooding, no? Rckrone (talk) 06:05, 28 April 2010 (UTC)

It has to be close to 100% water in the air; if you bend down you will not get the water if it is less. --98.221.179.18 (talk) 19:24, 28 April 2010 (UTC)

If rain is falling down, air must be coming up. Cuddlyable3 (talk) 19:53, 28 April 2010 (UTC)

The relevant experiment is to walk under a waterfall and see how dense it can be before you can't deal with it. If you have any experience with waterfalls you'll probably see that the force of the water will knock you flat long before it gets dense enough to drown you. Looie496 (talk) 20:57, 28 April 2010 (UTC)

extreme human evolution

Assumming that the human race will live to see Pangaea Ultima in 250 million years, what speculations do you have as to how humans will evolve given that amount of time?—Preceding unsigned comment added by CHEMX (talk • contribs) 22:55, 27 April 2010

Since humans have so far been around for maybe 3 million years, and perhaps do not have the stability of cockroaches and trilobites, I would assume that there will be no humans recognizable to us even if the planet has survived that long. alteripse (talk) 23:17, 27 April 2010 (UTC)

Evolution seeks to increase the number of offspring for a given environment, and since humans are doing a fine job of creating offspring, unless the environment changes humans are unlikely to change at all. Except maybe evolution to make birth control impossible. Predicting how the environment will change in 250 million years might be hard. Also, given our intelligence, we are unlikely to allow evolution to do anything at all, but rather we will take control of our DNA on our own. Ariel. (talk) 23:21, 27 April 2010 (UTC)

Respectfully thats just silly. The time scale is nearly 2 orders of magnitude greater than a human history that has already seen changes to the point of speciation. The human birth rate and the rate of the change of the environment means that the only thing we can be sure of is that your prediction, of no real change, is the LEAST likely of all alternatives. alteripse (talk) 23:34, 27 April 2010 (UTC)

Well, the human birth rate suggests we'll see an increase in genetic diversity but for evolution you need a difference in reproductive success (often due to people with certain genes dying before reproducing). Given modern technology and welfare states, your genes don't have much impact on your reproductive success. The amount of evolution we've seen over the last few million years is irrelevant since it is almost all pre-industrialisation and the existence of modern industry cannot be ignored. Evolution due to being a better fit to our environment won't happen much since we tend to alter our environment to suit us rather than the other way around. Evolution due to sexual selection is still possible, I suppose (which some authors have suggested will result in the human race splitting in two [6]). --Tango (talk) 23:46, 27 April 2010 (UTC)

The reference desk isn't for speculation and there is no way to do anything more than guess. Evolution has a large random element. I can make some general comments, though. If humans do change significantly, there won't necessarily be a single human race because we could have undergone speciation, but that seems unlikely due to the ease of travel these days meaning populations won't get isolated (although isolation doesn't have to be geographic). The most rapid evolution tends to happen during times with lots of people dying (especially ones leading to population bottlenecks) and modern technology combined with the near-global spread of humanity means that doesn't happen much any more, so we shouldn't expect much change in the human race. A Google search finds lots of other people's opinions if you don't like mine. --Tango (talk) 23:33, 27 April 2010 (UTC)

There are a lot of speculative, futurology predictions about human genetics. Lee Silver's Remaking Eden has a particularly interesting one regarding the possible long-term effects of "reprogenetics" technology on the human genome. But yeah, 250 million years is a long time. A lot of stuff can happen in that amount of time that would affect things. Even if you imagined that nothing major would happen (which is impossible, really), it's not clear how you'd even extrapolate current trends in a meaningful way. --Mr.98 (talk) 23:48, 27 April 2010 (UTC)

The difficulty here is that humans are able to actively resist the effects of evolution. When someone has a mutation that causes them to be unable to procreate - in steps science and provides a variety of interventions that allow that gene to be passed on. This reduces the tendency for bad genes to be eliminated from the population. We'll get better at this - we'll be able to treat genetic diseases. This could cut out beneficial genes as well as bad ones. Furthermore, we're changing the environment vastly more quickly than evolution can track those changes. Given a few tens of thousands of years of online dating and cellphone texting - we might evolve to take advantage of that...but nobody believes that this technology will still be here, unchanged in 10 years - let alone 100 or 1,000 or the 10,000 it might take for a noticable genetic change. We're also living longer and having children later...that increases the generation length...longer generation length, less genetic change, less evolution. Then there is the possibility of 'designer genetics' - maybe we'll be able to choose the genes of our children? If that happened, evolution could be at the whim of fashion. We might start doing things like copying our brains into computers and becoming immortal, digital beings. No more evolution with an infinite generation time.

With all of those possibilities (and more besides, I'm sure) - the laws of evolution may simply cease to apply to humans. So where we end up in even 1,000 years is totally, fundamentally unpredictable. Most scientists are loath to make technological predictions beyond 25 years - and our lives are increasingly technological beings.

I believe that we are on the brink of a post-genetic era - evolution for us is becoming entirely memetic. Memes (ideas) evolve, mingle, reproduce, survive or die out. They can do it on short genetic timescales and reproduction is cheap in an intercommunication-rich digital world. I could easily imagine a future where ideas are all that's left - humans (and human bodies in particular) become an unnecessary (and difficult) part of the future. We could be out-evolved by our own memetic offspring.

SteveBaker (talk) 02:53, 28 April 2010 (UTC)

Just as an example as to how bad we are at predicting even basic technological advances, consider that the first three books of the Foundation series lacked anything resembling an actual computer. And this is from an author, Isaac Asimov, who was an actual honest-to-god chemistry professor and professional scientist. The first book was written in the early 1940's, before computers even existed, and the series came to be in the early 1950s; at that time computers were basically large devices used to calculate ballistics trajectories and stuff like that. The idea that computers would be as pervasive as they are today didn't even enter into people's mind, even in science fiction. If someone as well versed in the science and technology as Asimov couldn't have predicted something as core to modern life as computers, writing only 60 years ago, how can we meaningfulling make predictions any reasonable time into the future. 60 years from now, will will likely find our lives pervaded by some technology which hasn't even been invented yet and which no one is really even thinking about. --Jayron32 03:40, 28 April 2010 (UTC)

Well, by the early 1950s Asimov was writing about some extremely advanced computers in the form of robots with positronic brains. The thing that pretty much everybody missed until around 1990 was what would happen with the internet. Looie496 (talk) 05:11, 28 April 2010 (UTC)

The difficulty here is that humans are able to actively resist the effects of evolution. - Steve, I'm disappointed that you make such a claim. That's plain wrong. What we do is changing the parameters of the selection - we do nothing about the evolution itself. In fact, we currently select some genetic defects out of the gene pool (without really understanding all implications) by parent screening and pre-natal screening. --Stephan Schulz (talk) 12:41, 28 April 2010 (UTC)

Evolution has effects - we can (and do) resist them. I don't see anything difficult or controversial about that claim. A genetic change that is strongly disadvantageous in our present world would "naturally" have drastically reduced the probability of that individual reproducing successfully. 'Bad' genes may well be retained in the gene pool through artificial reproductive help, or through treatment of the genetic diseases. This is us actively resisting evolution - ensuring survival, not just of the fittest, but also of the profoundly unfit. As a consequence, we may wind up with increasing numbers of people who are accumulating disadvantageous genes who can only continue to survive and breed with advanced medical help. Under those circumstances, we're not evolving to better fit our environment - but developing technology to prevent us from better fitting into our environment by changing the environment to meet whatever genetic weirdness is thrown up by random mutation and recombination. Every time we 'cure' a genetic disease - or help a couple to have children who otherwise could not because of some genetic problem - we're fighting the tide of evolution. Don't get me wrong - I'm not saying we shouldn't do that - but we should be more clearly aware of the magnitude of the effect we're having on our own species by doing that. SteveBaker (talk) 23:46, 28 April 2010 (UTC)

No, that's not true - or at least it's a weird definition. Evolution = change of the gene pool over time. We do not actively resist that change, we only influence how it is expressed. In-vitro, for example, reduces the value of the trait to be able to conceive naturally. But it increases the value of the trait to be able to fit into society in a way to make society pony up the resources for in-vitro (i.e. in the US the ability to make enough money to pay for it). The definition of "fitness" in evolution is the ability to dump genetic material into the next generation. It does not imply being faster, smarter, or prettier, although all of these may help in some environments. In fact, being a penniless student living off donations for a sperm bank probably makes you "fitter" than most other life styles in our environment. --Stephan Schulz (talk) 06:15, 29 April 2010 (UTC)

What if humanity is able to finally escape the planet entirely? If it even survives the next 3 million years, it's likely that humanity will leave it's ancestral home. If there are colonies on multiple planets/moons/asteroids, even in our own solar system, there will likely be isolated populations and speciation will occur simply due to the general cost of interplanetary travel. It doesn't help that mutation will be even more likely once you leave the protective cocoon of Earth's magnetosphere. -- JSBillings 13:00, 28 April 2010 (UTC)

Well I don't see us colonizing very far from Earth for a very very long time unless relativity is proven wrong. 25 light years is the point of no return. Would you volunteer to go with a few hundred others to live on a unknown and unexplored, and likely extremely dangerous planet, with no chance of ever seeing the ones you love ever again?---92.251.243.109 (talk) 21:45, 28 April 2010 (UTC)

Would you volunteer to sail a small ship into the complete unknown? Would you sail to an uncharted and dangerous continent to live there forever and never come back? Would you set out into the wilderness determined not to stop until you reached the other shore, not knowing how far you'd have to travel and what kinds of dangers you might have to face? Would you volunteer to take an untested contraption of wood and wire into the air, knowing that it might crash and kill you? Would you volunteer to fly alone in a single-engined plane across the North Atlantic, knowing that if anything goes wrong, you're as good as dead? Would you try to find a tiny island in the middle of the vast Pacific even though the odds are a gazillion to one against you? Would you volunteer to ride a rocket filled with explosive fuel into the vacuum of outer space, not knowing if you'll ever come back again? This is a rhetorical question, 92 IP. If you're the explorer type, you'd volunteer for all those things and more without any questions; if you're not, then you'd stay home. It takes all kinds, y'know. 76.103.104.108 (talk) 05:13, 29 April 2010 (UTC)

"The difficulty here is that humans are able to actively resist the effects of evolution"—well, kind of, but not entirely. And in any case, over 250 million years, making that assumption seems wrong. Humans have really only been able to do this well for a few hundred years, maybe a few thousand if you are very generous in your definitions. The idea that we will be extending this capability into the millions seems unjustified to me. (The idea that the species—in any form—will last into the millions seems unjustified to me, as well!) --Mr.98 (talk) 13:51, 28 April 2010 (UTC)

The assumption that the human race will survive millions of years was an explicit part of the question, so it doesn't need to be justified (that is what "assumption" means). --Tango (talk) 14:04, 28 April 2010 (UTC)

I know, that's why I put it in parentheses, because it is a little peripheral. --Mr.98 (talk) 14:32, 28 April 2010 (UTC)

If an advantageous mutation comes along, it has a chance of staying. That's the idea behind natural selection. Imagine Reason (talk) 13:13, 28 April 2010 (UTC)

That's a tautological definition of natural selection; whether a mutation is "advantageous" or not depends on the selective pressures of the environment. --Mr.98 (talk) 13:51, 28 April 2010 (UTC)

Considering the fact that humans are not perfect in any normal sense of the word, this should not be a problem. Imagine Reason (talk) 14:00, 29 April 2010 (UTC)

Members of the Scientology "Sea Org" who signed a billion-year employment contract with the organization will have only 750 million years left to catch up on their confessionals. Cuddlyable3 (talk) 19:51, 28 April 2010 (UTC)