Wikipedia:Reference desk/Archives/Science/2012 November 6

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November 6

Dichromacy and Trichromacy colorblind

I was aware some people are colorblind. I was wondering if there is any difference between dichromacy and trichromacy is any difference. If people are having trouble seeing green are they also unable seeing red. is there any difference between red and green colorblindness. I have never heard about anybody having trouble seeing yellow although Color blindness mentions blue-yellow colorblind they basically having difficulty seeing violet hues, but I never heard anybody who is disrupted on yellow hues. I am guessing most people I was aware of is Anomalous trichromacy, but I was wondering how Anomalous trichromacy works on blue-yellow sensors? Are they totally unable to see blue-yellow sensors on Anomalous trichromacy or they just see those as shades of brown. I have met one people on the bus is totally deficient on red, green, and blue they can see grayscale and shades of brown and pink, what type of colorblind is that?--69.226.43.174 (talk) 00:38, 6 November 2012 (UTC)

I think you misunderstand the meaning of the word colorblindness. It means an inability to distinguish colors that most people can tell apart, not an inability to see colors that most people can see. Looie496 (talk) 00:56, 6 November 2012 (UTC)

This page purports to show you how your favorite webpage looks to several common kinds of colorblindness. —Tamfang (talk) 01:03, 6 November 2012 (UTC)

I got the better understanding now about how colorblind works now. I bookmarked the Colorblind Webpage Filter (All I got to do is to type it on Google), and first I went through my favorite websites to play around with the colors. Anomalous colorblind is the less serious type and it is less noticeable unless under certain lighting conditions where certain cones may be skewed and interrupted. Dichromacy means people can only see two or three general colors, and their perceptions are reduced to whatever sensors are remained in their cones.--69.226.43.174 (talk) 04:45, 6 November 2012 (UTC)

Reason why we don't fall through the floor

I was having a discussion with someone on why matter doesn't simply pass through other matter (given the fact that normal matter is mostly empty space). I was under the impression that it was due to the electromagnetic force. He said that's a common misconception and it is due to the pauli exclusionary principle. Is he correct? ScienceApe (talk) 00:45, 6 November 2012 (UTC)

I have looked at Pauli exclusion principle and I am confident it isn't reasonable to apply this principle to explain why matter doesn't simply pass through other matter. Dolphin (t) 00:49, 6 November 2012 (UTC)

(This is incorrect—see below.) -- BenRG (talk) 23:13, 6 November 2012 (UTC)

It's because those atoms are bonded together as a solid (if the atoms or molecules aren't bonded together, then you have a fluid). Think of a hammock. It's mostly empty space, but nonetheless stops you from falling on the ground, because the threads are all tied together. StuRat (talk) 01:50, 6 November 2012 (UTC)

You are correct, he is wrong. The exclusionary principal describes why other electrons can't fill already occupied orbitals, hence limiting atomic bonding to specific valences. Sheesh, the things people come up with! μηδείς (talk) 02:18, 6 November 2012 (UTC)

(This is incorrect—see below.) -- BenRG (talk) 23:13, 6 November 2012 (UTC)

The Pauly exclusion principle: "Anyone with taste will exclude themself from any movie staring Pauly Shore." StuRat (talk) 03:26, 6 November 2012 (UTC)

The last exclusionary principal I encountered was my high school headmaster who kicked me out of the class for ... well, I'd better not say. -- Jack of Oz ^[Talk] 05:23, 6 November 2012 (UTC)

Wouldn't you think the "headmaster" would be tolerant of such things ? StuRat (talk) 05:47, 6 November 2012 (UTC)

Only if Jack was disciplined for being a cunning linguist. --Jayron32 05:51, 6 November 2012 (UTC)

I think they invented tolerance one Monday in 1983, well after I went to school. -- Jack of Oz ^[Talk] 06:20, 6 November 2012 (UTC)

The other person in the discussion is referring to electron degeneracy pressure, which only manifests itself in extreme examples such as the core of a collapsing star. The electron degeneracy pressure between your feet and the floor is negligible. Someguy1221 (talk) 03:22, 6 November 2012 (UTC)

(This is incorrect—see below.) -- BenRG (talk) 23:13, 6 November 2012 (UTC)

This is what he said, "The electrostatic force behaves completely differently from the contact forces we're used to. The floor pushes back exactly as much as you push on it; contrariwise, the electrostatic force's push depends entirely on the distance. You can derive Hooke's Law from the basic kinematics of QM - the compressing of the states by Pauli exclusion causes a corresponding increase in momentum as per the uncertainty principle. I'm sorry to break it to you but you've been taught a wrong fact for a long time." ScienceApe (talk) 03:32, 6 November 2012 (UTC)

From our article: A material subjected to ever increasing pressure will become ever more compressed, and for electrons within it, the uncertainty in position measurements, Δx, becomes ever smaller. Thus, as dictated by the uncertainty principle, the uncertainty in the momenta of the electrons, Δp, becomes larger.. In short, your friend doesn't know what he's talking about. The pressure exists as he suspects, but its value is insignificant outside of extremely dense matter. Someguy1221 (talk) 03:42, 6 November 2012 (UTC)

Also note that "The floor pushes back exactly as much as you push on it" is true for any explanation of a static situation. --Stephan Schulz (talk) 06:56, 6 November 2012 (UTC)

---

Solids and liquids are incompressible because of electron degeneracy pressure, and you don't fall through a solid floor (as opposed to a liquid floor) because of the intermolecular bonds. This has been asked before on the ref desk. -- BenRG (talk) 07:03, 6 November 2012 (UTC)

Yea Newton. The third law applies here: The weight of an object pressing upon another is countered by an equal and opposite force exerted by the electrostatic interaction between electric fields of atoms. Plasmic Physics (talk) 21:12, 6 November 2012 (UTC)

No, as I said above, it's electron degeneracy pressure that presses upwards on your feet, though it is horizontal electrostatic tension that prevents the floor from breaking apart under your weight. Newton's third law applies everywhere, but doesn't explain why you don't fall through the floor. You would fall through a floor made of jello, though the third law applies there too. -- BenRG (talk) 23:13, 6 November 2012 (UTC)

I just don't buy it, Ben. At normal densities, long-distance molecular interactions can be explained just fine without invoking degeneracy pressure. I don't see a need for it in this situation. Someguy1221 (talk) 00:58, 7 November 2012 (UTC)

Exactly. Where does compressability of solids fit into the degeneracy idea? Plasmic Physics (talk) 01:48, 7 November 2012 (UTC)

I would be surprised if it was correct, it would turn my understanding of atomic-force microscopy upside-down. Plasmic Physics (talk) 01:51, 7 November 2012 (UTC)

There is a bit of confusion above. The Pauli exclusion principle gives rise to exchange interactions. For fermions, such as electrons, this quantum mechanical effect manifests as an intrinsic repulsion towards overlapping orbitals. This exchange interaction is absolutely critical in determining the bond length in all forms of chemical bonding. As such, the Pauli exclusion principle plays a key role in determining the distance between atoms in all forms of solids, and by extension influences many properties, such as rigidity. Without the exchange interaction, solids wouldn't be solid at all. At the same time, the electrostatic attraction between the positively charged nuclei and negatively charged electrons is also essential to chemical bonding and determining the properties of solids. Without the electrostatic forces there would also be no solids at all. You won't get an accurate model of solids unless you consider both electrostatic interactions and exchange interactions. See, for example, the Lennard-Jones potential model which gives an example of how repulsive exchange interactions and attractive Van der Waals forces (electrostatic), combine to create a local minimum in the separation potential. Its that local minimum that creates a natural bond length. When you push on a solid, the atoms in your hand displace the atoms in the solid. That push translates into the solid by stretching some of the bonds and compressing others, and ultimately it is that displacement from the ideal bonding length that causes the solid to exert a collective force that pushes back against you. This is much the same as if you could imagine the solid having been made of many tiny little springs. Since the chemical bonding would not occur without considering both principles, I would say that both electrostatic forces and the Pauli exclusion principle are necessary to understanding why we are able to stand on the floor. Dragons flight (talk) 03:18, 7 November 2012 (UTC)

People talking alone

What's wrong with these people? I know that they are not necessarily mentally ill, some just take drugs, also legal drugs like coffee. But, what has happened in their brain, what is the brain mechanism of "mental talk, but not aloud"? Comploose (talk) 00:59, 6 November 2012 (UTC)

Please see Intrapersonal communication. Specifically: "Simon Jones and Charles Fernyhough cite research suggesting that our ability to talk to ourselves is very similar to regular speech. This theory originates with the developmental psychologist Lev Vygotsky, who observed that children will often narrate their actions out loud before eventually replacing the habit with the adult equivalent: sub-vocal articulation. During sub-vocal articulation, no sound is made but the mouth still moves. Eventually, adults may learn to inhibit their mouth movements, although they still experience the words as "inner speech"."A8875 (talk) 01:40, 6 November 2012 (UTC)

It can also be helpful in some cases, like repeating something out loud to remember it. I believe this trick works because more of the brain is involved in speaking and hearing the words than just thinking them. There's also the issue of people who aren't able to read or count silently. This could, indeed, in some cases compensate for a deficiency in their brain, by using different neural paths to bypass the non-functional portion. StuRat (talk) 01:44, 6 November 2012 (UTC)

what is the brain mechanism of "mental talk, but not aloud" - How else does one think, except as mental talk, but not aloud? All my thoughts that are not pictures are words, sentences, paragraphs, even dialogues. How else do you reach conclusions, consider options, assess situations, except as words not spoken aloud? Have I missed something? There are people who process things externally. I worked with one who drove most of us into any room in the building where she could not be heard. Is that what you mean? Bielle (talk) 02:03, 6 November 2012 (UTC)

I wanted to contrast people who are "mental talk, in silence" to others who are "mental talk, aloud". Something is different in the second case: too much coffee, stress, some drugs sometimes makes some people be in the second group, even if they are normal under other aspects. I was not asking about any contrast in terms of "mental talk" / "no mental talk". Comploose (talk) 02:19, 6 November 2012 (UTC)

My mom always used to say "People who talk to themselves are either crazy or have money in the bank." To which she would always add "And I'm flat broke." Of course, it isn't any sign of being mentally defective in any way to occasionally talk to yourself aloud. People who aren't under the influence of drugs or stress or who are otherwise perfectly normal, mentally (for any given standard of "normal"), do sometimes speak to themselves out loud. Of course, people carry on all sorts self-talking, whether it is internal monologue, keeping a diary or journal of some sort. One journal articles I found on actual talking out loud to oneself is [1].--Jayron32 03:35, 6 November 2012 (UTC)

Unfortunately, when I engage in an internal monologue, I always end up heckling myself. StuRat (talk) 03:23, 6 November 2012 (UTC)

At least that won't make you go blind. Be grateful for the respite.  :) -- Jack of Oz ^[Talk] 05:18, 6 November 2012 (UTC)

Isn't heckling yourself by definition internal dialogue? -- Q Chris (talk) 13:47, 6 November 2012 (UTC)

Maybe we should all get in touch with our inner StuRat and have a good old chinwag. I'll get round to it when I've finished my current vitally important project (transplanting Mt Everest to the Antarctic a teaspoon at a time). -- Jack of Oz ^[Talk] 21:26, 6 November 2012 (UTC)

"I used to be poor and crazy, but now I'm rich and eccentric." Someguy1221 (talk) 03:19, 6 November 2012 (UTC)

It's entirely natural to talk out loud, whether there is someone there to listen or not. "How can I know what I think until I hear myself say it?" The discipline of speech is good for ordering internal thoughts. --TammyMoet (talk) 10:13, 6 November 2012 (UTC)

what's wrong is that nobody's given them an old dead cell phone. if they held the phone (or even a toy phone, or anything of similar form factor, really) up to the side of their face, they could talk to themselves all they want and nobody would notice. Gzuckier (talk) 02:06, 9 November 2012 (UTC)

Nature of sound

If a car crashes in the forest and nobody is there to hear it, does it still make a sound? Bonkers The Clown (talk) 07:53, 6 November 2012 (UTC)

Yes. HiLo48 (talk) 08:03, 6 November 2012 (UTC)

And what makes you say so? Can you elaborate as to why "yes" and not "no"? Bonkers The Clown (talk) 08:05, 6 November 2012 (UTC)

The Laws of physics. HiLo48 (talk) 08:14, 6 November 2012 (UTC)

Well the driver would presumably hear something. But this is essentially the same question as If a tree falls in a forest, where this is discussed. (I changed the title of your question to something more meaningful.)--Shantavira|^{feed me} 08:27, 6 November 2012 (UTC)

This depends on your definition of "sound". The way physicists define it, as a pressure wave, does not require an observer. Indeed, we would need to change much of physics to allow for a collision, in air, which does not produce pressure waves. Now, if a philosopher wants to define sound as only existing when it is heard, that's fine, but has nothing to do with science. StuRat (talk) 19:55, 6 November 2012 (UTC)

What if it is a superpositional Schrodinger soundwave? Plasmic Physics (talk) 20:59, 6 November 2012 (UTC)

In that case, only dogs can hear it. And Schrödinger. ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:20, 6 November 2012 (UTC)

And potentially dead cats. StuRat (talk) 03:21, 7 November 2012 (UTC)

I mean, if the crash was initiated by a quantum trigger, would it still make a definitive sound if there is no observer? Assuming unrealistically perfect conditions. Plasmic Physics (talk) 01:42, 7 November 2012 (UTC)

protons

Is the proton a fundamentally stable particle? Or does it have a finite lifetime as predicted by some extensions to the standard model? What explains the anomalous spin of protons? :) Bonkers The Clown (talk) 08:39, 6 November 2012 (UTC)

If you're aware that physicists can't decide whether the proton is fundamentally stable, why would you bother asking a bunch of random people on the internet? Someguy1221 (talk) 09:47, 6 November 2012 (UTC)

Additionally, our article on the Proton spin crisis mentions that this is an unsolved problem, which I'm sure you were already aware of. Someguy1221 (talk) 09:51, 6 November 2012 (UTC)

A lower limit for the half-life of the proton is 2.1 × 10²⁹ a, but proton decay has never been observed. Double sharp (talk) 14:05, 6 November 2012 (UTC)

The proton is almost certainly unstable, the only question is how large the half life is. Hawking has argued that the proton would at least have to decay via making a transition to a virtual black hole which then evaporates via the Hawking process.

Also note that the deuteron is known to be unstable in the standard model with a half life of about 10^(218) years. Count Iblis (talk) 16:18, 6 November 2012 (UTC)

Proton decay does or should have the relevant ideas covered. DMacks (talk) 16:29, 6 November 2012 (UTC)

Worried to death?

I was thinking about a phrase my mother used to use "I was worried to death!" and wondered if, in fact, it was possible to shorten your life - or at least adversely affect it - by worrying! Is there any good scientific research on the deleterious effects of worry on human beings? I don't mean the mental illness anxiety, by the way. Just plain, old fashioned worry. --TammyMoet (talk) 10:15, 6 November 2012 (UTC)

Worrying causes negative thoughts and negative thoughts translate into depression. And you'll die sooner or later if you worry daily. Don't worry. Be happy. :) Bonkers The Clown (talk) 13:38, 6 November 2012 (UTC)

Citation needed. AlexTiefling (talk) 13:41, 6 November 2012 (UTC)

If you mean worry v.tr. 3 a (To seize with the teeth and shake or tug at repeatedly) then you certainly could be worried to death rather quickly! -- Q Chris (talk) 13:44, 6 November 2012 (UTC)

Topical question, apparently empirically answered this week in a rather tragic death. well, okay, it was 'heartbreak', but that has to be a near-cousin of worry, non? --Tagishsimon (talk) 14:59, 6 November 2012 (UTC)

That looks like hearsay to me. AlexTiefling (talk) 15:05, 6 November 2012 (UTC)

Here's a news article, with links to a scientific article [2]. It explains how grieving can greatly increase incidence of heart attack. I don't know if "grieving" is similar enough to "worry" for your purposes, but there it is... SemanticMantis (talk) 17:18, 6 November 2012 (UTC)

Not grieving? Keeping it all inside? ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:18, 6 November 2012 (UTC)

Stress certainly has negative effect on health, and thus can reduce your lifetime. Not sure if that's what you mean by worry. - Akamad (talk) 17:41, 6 November 2012 (UTC)

To clarify, what I meant by "worry" is something like sitting envisioning a future event that might or might not actually happen and all its ensuing ramifications. You know, the sort of unproductive thought processes you indulge in at 3 am... --TammyMoet (talk) 20:47, 6 November 2012 (UTC)

As with "Future Events Appearing Real". ←Baseball Bugs ^{What's up, Doc?} carrots→ 23:18, 6 November 2012 (UTC)

Or "False Evidence Appearing Real". Yeah that kind of thing. --TammyMoet (talk) 10:21, 7 November 2012 (UTC)

The proverb has it "worry is interest paid on a debt that may never come due". On the other hand, there is another hand. The flip side is that sometimes worry concentrates the mind to the point that you find an actual and effective contingency plan to deal with the potential problem.

So I'm unwilling to say that worry is a uniformly bad strategy — it's saved my butt more than once. It does have very real costs, though, and they have to be balanced against the potential benefits. How you do that is your worry. --Trovatore (talk) 10:26, 7 November 2012 (UTC)

how to be more powerful (literally, not philosophically)

EDIT: First of all this question had been misinterpreted. This is not a philosophical question but purely practical. I hope you are able to follow my reasoning, and what the question is.

Let us begin with the observation that with a coffee mug or any other object in front of you (try it!) you can cause the coffee mug to move simply by selecting a new location for it, picking it up, and moving it.

The proximate cause of the move or displacement was your own thought. Since, for example if you moved it with your right hand, if after that thought you found your right hand encumbered by something you forgot about, you would have just moved it with your left hend. It is really your thought that caused the change.

So, a thought is a very powerful thing.

But, on the other hand, there are thoughts that do not cause a change in the world. They come and go, like an old man's erection. They affect nothing.

I would like to know how to make my thoughts more powerful. To begin with, by increasing their effectiveness on my own body, and then on my team, organization, country, world. What do you suggest is an appropriate way to increase the leverage of my thought, so that I can not only move a coffee mug, but reshape my life, country, or world? Please be detailed.--91.120.48.242 (talk) 13:19, 6 November 2012 (UTC)

Begin by making good use of your time. Spend less of it asking unproductive questions on RefDesk.

In all seriousness - economic privilege will make more difference to the 'power of your thoughts' than anything else. If you're white, male, American, upper- or middle-class, able-bodied, neurotypical, not subject to mental ill-health, heterosexual, and not too outspoken about your religious views, you'll go far. As to what you can do, yourself - there are many things, but the degree to which they're effective correlates to the extent that you match the privileged profile described. (Obviously this is socially determined; if you're Japanese rather than American, then being ethnically Japanese rather than white is the appropriate factor, etc.) AlexTiefling (talk) 13:34, 6 November 2012 (UTC)

I really did not mean on this level, I meant on an everyday level, hence the example of a coffee mug. I mean things like translating from "having a product idea" to actually shipping it, much like translating from "I want to move this cup over" to it actually being moved over. Can you address it in more practical terms? --91.120.48.242 (talk) 14:10, 6 November 2012 (UTC)

If you mean literally then a Powered exoskeleton would do it for you. -- Q Chris (talk) 14:25, 6 November 2012 (UTC)

That must be one massive mug. Plasmic Physics (talk) 20:53, 6 November 2012 (UTC)

You talked about your ability to "reshape my life, country, or world" - that sounds like going beyond the immediately physical effect of your thoughts. 'Reshaping the world' doesn't sound like 'an everyday level' to me. If you do mean things like translating product ideas to manufactured products, then my earlier comments still stand. AlexTiefling (talk) 15:04, 6 November 2012 (UTC)

Try reading How to Win Friends and Influence People by Dale Carnegie. StuRat (talk) 19:50, 6 November 2012 (UTC)

or Power for Success by Frank Haddock. Also speaking the truth can garner other's support. and being able to find hidden truths is very powerful as it is difficult to deny/ignore GeeBIGS (talk) 01:19, 7 November 2012 (UTC)

If you just want to be "powerful" in the sense of "changing the world", try burning down a world-famous landmark. That worked pretty well for Herostratus, who sought fame by burning down the Temple of Artemis (and succeeded). If you want to be powerful in a "good" way, try political campaigning, running for office, founding a charity organization, or joining the Syrian rebels. All of these things have a good chance of making a non-negligible impact on the world. --140.180.252.244 (talk) 02:06, 7 November 2012 (UTC)

If we look at just watts of energy that are created or responsible for, I'm pretty sure the founder of Ikea was far, far more powerful by founding ikea than by donning an exoskeleton and doing work himself instead of getting ohters to do it. In monetary terms, there is no real way to get as much value out of an exoskeleton as by mobilizing loads of people in the form of a company either. So on a long-scale in physical terms (watts of work performed) or economic terms (value produced) you can beat an exoskeleton. I would be interested in how to start that process. The links given above about "Power for success" or the other link are an interesting idea, but really you are telling me, "Put on your to-do list: buy and read Power for success." I believe there are more effective sentences you can tell me, as I probably won't buy and read that book. What can I do today that will measurable impact my ability to follow through on my ideas? --91.120.48.242 (talk) 15:19, 7 November 2012 (UTC)

I actually thought in this vaguely general direction, back in my psych major days... it occurred to me as you say, that our basic thought is not "lift your right arm, advance it towards the cup, lower it and grasp the cup" etc., it's "move the cup", and as you say, if your right hand is blocked, you move your left, etc. If both are blocked, and you ae sufficiently motivated, as by somebody holding a gun to your head and demanding that you move the cup, you will move it with your feet, or your teeth, or nudge it with your nose, or whatever. So it seemed to me that the basic thing is goal-orientedness of thought. And i now enlarge on that to answer your question somewhat vaguely is the way to empower your thoughts in that sense is, therefore, to keep your eyes on the ultimate goal you have in mind, and not to get too tied down to a specific pathway or procedure, etc. Rather than just running up against a block and grinding away at it, find a way around or over it. Gzuckier (talk) 02:18, 9 November 2012 (UTC)

Air quality in Prometheus

During landing (minute 23 and about three quarters) on the foreign planet, the readings of the gases comprising the atmosphere are given as 79% nitrogen, 21% oxygen and trace argon -- something very similar to earth's atmosphere. But a scientist on board then says that CO₂ readings are three times what they would be on earth -- about 3% -- and she explains that one would die after only a few minutes of exposure to such an atmosphere without a protective suit (and, I'm assuming, a breathing device). Why would triple the amount of CO₂ necessitate a protective suit? DRosenbach ^{(Talk | Contribs)} 14:35, 6 November 2012 (UTC)

Not surprisingly our article Carbon dioxide#Toxicity mentions some of the effects of an increase carbon dioxide:

In concentrations up to 1% (10,000 ppm) will make some people feel drowsy.[78] Concentrations of 7% to 10% may cause suffocation, manifesting as dizziness, headache, visual and hearing dysfunction, and unconsciousness within a few minutes to an hour.

It also links to Hypercapnia, which is our article on the condition of excessive carbon dioxide in the blood. 3% seems to be in the range of starting to get close to dangerous but perhaps not quite there yet and I'm not sure that dying within a few minutes is likely. I'm not even sure it's likely at 7% although I would't want to risk it particularly if anyone who could try to save me is going to be exposed to the same conditions. Perhaps the producers were thinking of carbon monoxide?

BTW our article also mentions something which you can check in Atmosphere of Earth. Either your memory of the movie is wrong, or there's something seriously wrong with it. 3% carbon dioxide is not triple the concentration of earth (which isn't 1%, that's well over 1 order of magnitude wrong).

Nil Einne (talk) 14:47, 6 November 2012 (UTC)

You're right -- all she said was "[it's only like earth] if you're breathing through an exhaust pipe. CO₂ is 3%. Two minutes without a suit and you're dead." DRosenbach ^{(Talk | Contribs)} 14:50, 6 November 2012 (UTC)

The exhaust pipe bit makes me think it even more likely the producers were confusing carbon monoxide and carbon dioxide. Nil Einne (talk) 14:52, 6 November 2012 (UTC)

This source also mentions [3] that the planet in question was most likely supposed to be carbon monoxide as it's been suggested before that the planet is polluted with carbon monoxide. (I'm not entirely sure why that would be the case, if the planet has similar atmospheric conditions and temperature to earth, you would expect any carbon monoxide would be oxidised to carbon monoxide so there needs to be a constant high source or some reason why this is not happening, see Carbon monoxide#Atmospheric presence. You could get something like Venus where photodissociation produces carbon monoxide but I'm not entirely sure how likely that is if you otherwise have similar conditions to earth. At the very least the high levels of UV may be an additional concern.) Nil Einne (talk) 15:02, 6 November 2012 (UTC)

Using the figures in Hypercapnia, 10kPa will cause acute symptoms shortly leading to death--that's about a 10% concentration. Chronic respiratory acidosis will set in at about half that concentration. The 3% number is probably global warmist propaganda to make CO2 sound more dangerous than it is. CO2 and CO are odorless. Given how bad that movie stank, I suspect they meant to say it had a 3% concentration of flatus. μηδείς (talk) 15:02, 6 November 2012 (UTC)

Don't assume malice when stupidity will suffice.-- OBSIDIAN†SOUL 16:45, 6 November 2012 (UTC)

All of the above explains why you would need breathing apparatus; but not why a full-body suit would be needed. One reason would be solar radiation or protons, but as space exposure notes, that's a long term concern, not a 3-minute-death issue. Another would be very low pressure - if the ambient pressure was very low (cf Armstrong limit) an explorer would develop ebullism (as Kittinger did on his hand during his record dive), even if she was breathing air at 1 bar. But the planet exhibits a dense cloud layer miles above the surface, suggesting the surface pressure is pretty high. So that leaves the possibility that the atmosphere contains something so unpleasant that even a few minutes of it touching exposed skin would be fatal. Skin is pretty good at keeping out the environment, so that would necessitate the atmosphere was significantly acidic, caustic, or otherwise significantly toxic - something much worse than exhaust gas. Under relatively normal pressure and the specified air contents, they'd just need a respirator - which is exactly what the human characters wear in Avatar. I fear the suits are there for the theatrical "let's suit up" effect they provide. -- Finlay McWalterჷTalk 16:58, 6 November 2012 (UTC)

And breathing specifically is the express purpose of the suits - Holloway asks David why he's wearing a suit when "you don't breathe" (0:25:38) - not pressure, toxicity, or biosecurity. -- Finlay McWalterჷTalk 17:05, 6 November 2012 (UTC)

Actually, about %5 carbon dioxide is needed to cause chronic acidosis, so short exposures of 3% to healthy people should be harmless. The purpose of the suits was to show the contrast between the inside and outside environments, to give the alien something to break through--to allow the use of the suits as props. μηδείς (talk) 18:05, 6 November 2012 (UTC)

Note that over about 6bar, 80% nitrogen will give nitrogen narcosis, and over about 9bar, 20% oxygen will cause oxygen poisoning. It is the partial pressure that is important - the pressure mutltiplied by the concentration. CS Miller (talk) 20:54, 7 November 2012 (UTC)

• Hmmm. It's possible to overcome acidosis by infusion of sodium carbonate [4], the kidney tubule can regulate ammonia production [5], and damage to the inner ear can reduce the increase in ventilation [6]. I would not rule out the possibility of protecting people from moderate CO2 levels by some sort of medication - I'm not even convinced that gradual adaptation to this environment is not possible, unless and until I find data to prove it. Wnt (talk) 16:31, 8 November 2012 (UTC)

Lemme get this straight. A film which identifies "35 light years" as "a half billion miles", and you expect them to understand physiological effects of CO2 at above an average third grader's comprehension level? Gzuckier (talk) 02:51, 9 November 2012 (UTC)

Gzuckier has the right of it I think. Scripts don't have to make sense scientifically to make money. — Preceding unsigned comment added by 67.188.225.212 (talk) 08:00, 9 November 2012 (UTC)

Alcoholism - Biological process

Hi all, First, please note that this is not a request for medical advice, but a question about specific biological process inside the body. Please do not give any specific medical advice. I have read places that alcoholism/recovering from alcoholism can cause the following 2 effects:

1: Extremely bad body odor 2: External bruises around the liver, external scarring.

I was wondering how it is that the body/the alcohol ingested can cause these problems - and what is the chemical/biological reason for this on a fairly simple level. There doesn't seem to be anything lited in the article on Alcoholism. Please do not give advice on how to treat these as it consitutes medical advice and I don't want my post deleted. 80.254.147.164 (talk) 15:08, 6 November 2012 (UTC)

1. Alcoholism causes a deterioration in self-care, drunks don't shower as regularly as non-drunks in a given population.
2. Alcohol impairs blood clotting - bruising anywhere on the body may be exacerbated. Roger (talk) 18:14, 6 November 2012 (UTC)

1) Alcoholics may also sweat alcohol, which smells unpleasant to most, and also readily evaporates, taking regular body odor with it. StuRat (talk) 19:45, 6 November 2012 (UTC)

• On odor I found what might be a useful reference [7] - I'll leave it to you to track it down.

• Hmmm, on the bruises I found [8] which indicates purpura fulminans as a possibility; also [9] if only you could chase down the other part of it. But I don't think I have it; I suspect the blood clotting answer above is the correct one. Wnt (talk) 23:30, 7 November 2012 (UTC)

2) Alcohol can act as a blood thinner, which can cause blood to leak out of blood vessels and cause bruising. StuRat (talk) 23:34, 7 November 2012 (UTC)

Death determination in Sherlock Holmes

Maybe we're all just a little too informed these days because of shows like CSI, but shouldn't Watson have been confused by the hanged man's lack of rope marks on the neck that usually occur during a hanging. It seems awfully sloppy for him to have overlooked such a thing, especially since both he and Holmes are so astute in so many other scientific findings? I mean, sure, it would disrupt the entire plot, but it seems to undermine it just a tad too much -- they could have had him executed in another fashion to preserve his apparent death and subsequent resurrection. DRosenbach ^{(Talk | Contribs)} 14:54, 6 November 2012 (UTC)

It was somewhat sloppy, but Watson was only there to pronounce death, not perform an autopsy or otherwise determine cause of death. IIRC, he checked for pulse and maybe made a mirror test, but that was it. The guy who cut Blackwood down should have been the one to mention the oddity, I would think. Matt Deres (talk) 15:35, 6 November 2012 (UTC)

The entire premise of Sherlock Holmes is faulty, that every clue leads you down a single path. For example, "no sign of a break-in" = inside job. Instead, every clue only alters the probabilities, and you never can absolutely conclude anything, only that certain chains of events are more likely than others. StuRat (talk) 19:42, 6 November 2012 (UTC)

How can the premise of investigaion be faulty? Holmes and Watson are merely before their time, applying CSI style crime investigation to the late 19th century. Sure, licking the broken fragments of a fractured stone tomb cover and examining the premises of potential criminal activity without a warrant is not something that would be done today...but I still think it ought to be considered realistic fiction. DRosenbach ^{(Talk | Contribs)} 22:02, 7 November 2012 (UTC)

The premise is that there are only a small number of possibilities and that every clue eliminates some of them. This is "absolute logic", but is not really what applies in the case of criminal cases. It's more "fuzzy logic", where each clue only pushes you a bit more or less in one direction. Even seemingly objective results, like fingerprints, are really still subject to opinions, falsification, etc. And they really stretch it in the case of Holmes' deductions. For example, he once concluded that a man with a tan in England during winter had just returned from India. Well, that's one way to get a tan, but there are many other ways. StuRat (talk) 23:37, 7 November 2012 (UTC)

Cloning in animals Vs. plants

A gene of interest has been isolated via restriction enzyme digest and amplified using polymerase chain reaction (PCR). We want to clone this gene of interest by inserting it into a plasmid vector, making a recombinant DNA molecule. What differences in the cloning method would we want if we wanted to express the gene of interest into a plant? — Preceding unsigned comment added by 150.203.114.11 (talk) 15:02, 6 November 2012 (UTC)

I'm sorry, but this (to me) a very general and vague question. Can you clarify? In case it helps, one simple difference between cloning in animals and plants is that many plants naturally clone themselves, see vegetative reproduction. In animals, natural asexual reproduction is highly restricted, mostly to little things like hydras. How is this relevant to gene insertion? SemanticMantis (talk) 17:10, 6 November 2012 (UTC)

Maybe some context will help. That question is the last in a sequence. Here it is:

A gene of interest has been isolated via restriction enzyme digest and amplified using polymerase chain reaction (PCR). We want to clone this gene of interest by inserting it into a plasmid vector, making a recombinant DNA molecule.

What features of a plasmid are necessary for this molecular cloning to work?

How do we get the gene of interest into the plasmid vector?

The gene of interest is inserted into the plasmid. Describe two methods by which the plasmid can be transformed into E.Coli.

How do we know which transformed E.Coli cells are the desired clones?

Describe any differences in the cloning method if we wanted to express this gene of interest into a plant.

--150.203.114.11 (talk) 17:16, 6 November 2012 (UTC)

Ok, that looks like homework. If you want more help, you'll have to explain how you've started, what sources you've looked at, and where you are stuck. We generally have a rule against doing people's homework for them, see the disclaimer at top. SemanticMantis (talk) 17:20, 6 November 2012 (UTC)

It's not homework; it's pracice questions for the examin. And besides, this is biology; there is no such thing as "being stuck" like there is with maths or physics; you either know the answer a priori or you don't; it's not something you can deduce or work out.--150.203.114.11 (talk) 17:31, 6 November 2012 (UTC)

Thank you for being honest. Practice examination questions are clearly a form of homework. If we work out the answerr for you, that helps us get smarter, but doesn't help you. Your claim about being stuck is nonsense. Floda 121.221.77.87 (talk) 00:26, 7 November 2012 (UTC)

To help you work it out: "A gene of interest has been isolated via restriction enzyme digest and amplified using polymerase chain reaction (PCR). We want to clone this gene of interest by inserting it into a plasmid vector, making a recombinant DNA molecule. What differences in the cloning method would we want if we wanted to express the gene of interest into a plant?" I should add that I've never actually done this to a plant and I'm rather out of date in my recollections off-hand, so I'll leave it to you to mull over your homework and hopefully provide the latest updates to Bacterial_transformation#Plants, Plant_virus#Well_understood_plant_viruses, gene gun, etc. as you make your observations. Wnt (talk) 23:14, 7 November 2012 (UTC)

American Bison Furs

With the Ameican Bison once numbering 30 to 60 million, and hundreds of thousands to millions of hides being shipped back to the east coast every year in the second half of the 1800's, what happened to all the furs, rugs, robes, etc...? A majority would be lost, worn out, thrown away, but with untold millions of hides processed into some sort of product shouldn't they still be a realitively common item in the United States? Or do treated hides just not last long enough? Beach drifter (talk) 15:44, 6 November 2012 (UTC)

Would not much of the hides be turned into leather? I'd guess 100+ year old shoes, suitcases, etc, are relatively common, but equally that the source - bison, or cow, for instance - less obvious. --Tagishsimon (talk) 16:00, 6 November 2012 (UTC)

I don't think furs last all that long, at least if you use them. If stored in a refrigerator for a century they last, sure, but not many people did that. StuRat (talk) 19:36, 6 November 2012 (UTC)

What is a major disadvantage of PCR compared with in-vitro replication?

What is a major disadvantage of PCR compared with in-vitro replication?--150.203.114.11 (talk) 16:50, 6 November 2012 (UTC)

What did your teacher say was a major disadvantage, or what was written in your textbook? That's where you will find the answer to your question. --Jayron32 18:40, 6 November 2012 (UTC)

Isn't PCR a form of in-vitro replication? DRosenbach ^{(Talk | Contribs)} 22:04, 7 November 2012 (UTC)

Science fiction question regarding physics

I'm hoping to get a realistic physics viewpoint on a fictional event. Say there is a person who is, for one reason or another, trapped between two different timelines. Their body rapidly phases between the two, leaving a vacuum during the infinitesimally short time they are not present. Would such a vacuum be extremely cold? For directly, would the person be cold to the touch? Thanks in advance for anyone who answers. --Ghostexorcist (talk) 17:56, 6 November 2012 (UTC)

The process you are describing would cause the conservation of matter and energy to be violated in each timeline. This is such a wild deviation from normal thermodynamics, I don't think we can easily speculate. But how rapid is the oscillation? Will Brownian motion convey air molecules into the vacated space prior to the person returning? Because if so, that space might be expected to get very hot, rather than cold - with consequent danger to the oscillating person, not just bystanders. AlexTiefling (talk) 18:01, 6 November 2012 (UTC)

Well, just as physics was modified to allow for the conservation of total mass and energy, versus each separately, let's imagine that it's again modified to allow for conservation of the total mass and energy in all possible timelines. In this case, assuming the person does not materialize in a vacuum, the air where they appear needs to go somewhere. The most elegant solution is to send that air the other way, so no vacuum is created. If, instead, you suddenly blow the air out of the way, then that will create a minor explosion where the person arrives, and a sudden implosion where they left. Both would result in an increase in temperature. The place they left would have a net reduction in air pressure and the place where they arrived would have an increase. In an enclosed space, this could pop your ears. If you are the person being transported, this might pop your ears in any case. So, sending the air back the other way is the best solution (although this could introduce bacteria, pregnant mosquitoes, and such into the other environment). StuRat (talk) 19:29, 6 November 2012 (UTC)

This popping is the option used in The Stars My Destination, by the way. Wnt (talk) 15:58, 7 November 2012 (UTC)

This is just basically nonsense. Any one contradiction logically implies all other contradictions. You might as well ask if 2=3, then does 5=6? The answer can be yes (if 2=3, then 2+3=3+3, or no, because 2x2=3x2, i.e. 4=6, not 5. Or does it? It is utter bullshit, so make up whatever ad hoc nonsense (like air switching) you want. μηδείς (talk) 19:50, 6 November 2012 (UTC)

Medeis put it a bit impolitic, but she's essentially correct. It was stated much better by Arthur C. Clarke, who had Clarke's three laws, the third of which is very germane to the question. What Clarke said was "Any sufficiently advanced technology is indistinguishable from magic." Which is to say that, when writing speculative fiction of any sort (either fantasy or sci-fi), it isn't really necessary to be entirely correct with regards to the laws of physics, indeed it is better to not even try at all, since any half-assed kludge attempting to explain FTL communication or teleportation or any of a number of other common sci-fi tropes will necessarily invite criticism (justly so) as being completely incompatible with the known laws of physics. So Clarke's solution was to just not try: let the magic be magical. Also relevent: when writing about the present, we don't spend any time explaining TV or the internet or any of a number of other technologies that would have seemed quite "magical" to anyone living, say, 300 years ago. We all know TV works, and many of us know why it works, and even if we don't it is common enough to be accepted without an exhaustive discussion of how the laws of physics allow it to work. In the same way, there's no need to make room in your science fiction writing to allow for lengthy explanations of how physics allows for some bit of sci-fi technology: the characters in the story will accept it, so there's no real need to explain it to the readers, and again, any attempt to explain it to the readers will only come off as clumsy and essentially wrong. --Jayron32 20:06, 6 November 2012 (UTC)

I disagree. I like my sci-fi to at least be within the realm of possibility. Take the Stephen King book The Stand. It started out about something possible, an out-of control disease spread from a germ warfare lab, then became an absurd tale about the devil. At that point I lost interest. Also note that real sci-fi occasionally gets it right, with Clarke predicting communication satellites and even The Jetsons predicting the microwave oven. StuRat (talk) 20:19, 6 November 2012 (UTC)

De gustibus non est disputandum. Clarke has sold a book or two in his day, and may have something relevent to say on writing successful science fiction. --Jayron32 20:22, 6 November 2012 (UTC)

Not to mention that The Stand really isn't science fiction, at least not the type of "spaceships and robots" science fiction that both the OP and Clarke are discussing here. Applying his law requires sufficiently advanced technology, and absolutely nothing in The Stand is really advanced technology. It is essentially set in the 1970s. Finally, not liking Stephen King is fine: many people don't like him. But not liking The Stand merely because you didn't expect anything supernatural in it seems incongruous. The supernatural is kinda his thing. I mean, even assuming you read The Stand the year it came out, there were previous books about A telekinetic teenager, a town of Vampires, and a telepathic child and a haunted hotel. It took him until Cujo before he wrote a book entirely devoid of the supernatural, and even after that, the vast majority of his books feature it prominently. --Jayron32 21:12, 6 November 2012 (UTC)

I have to agree with Jayron re The Stand. King almost always writes fantasy dramas. The Stand succeeds briliantly as a Drama. (I am not a huge fan of King's, but his good books are good.) The Tommyknockers is pure science fiction, and it's crap. 11/22/63 is almost pure science fiction, and succeeds brilliantly. King has a thing for ghosts or devils opening doors. he does it in The Shining and The Stand, which are both successful dramas. He needs to be judge within universe and onthe basis of a drama writer.

If you want hard sci-fi read the early Larry Niven. For example, his teleportation boothes are subject to the conservation of momentum and require oceanic buffers to prevent zoom-splatification. As far as I am concerned, a good human conflict is the essence of drama. If you want good sci-fi then look for good drama. Miven could do this and Heinlein was the best. No one ever gave a whit about the Dean's bull ...shit. μηδείς (talk) 21:48, 6 November 2012 (UTC)

I liked Heinlein's supernatural stuff as much as his hard SF. I mean the early supernatural stuff, like Gulf and The Unpleasant Profession of Jonathan Hoag. Stranger is OK but it's on the border of where he abandoned tight plotting for having his characters explain things to each other. --Trovatore (talk) 21:57, 6 November 2012 (UTC)

Other good examples: Lost Legacy, Waldo, Magic, Inc. --Trovatore (talk) 23:24, 6 November 2012 (UTC)

One of the things to remember about good science fiction writing is that it is good writing first and good science fiction second. What makes some of the best science fiction is the sort of universality of themes and novel approaches to them, which isn't something that is strictly confined to science fiction, but is what makes all quality literature worth reading. In good science fiction, the "science fiction" elements blend in or melt away in ways that make them part of the background of a really good story. Which isn't to say that such elements are unimportant, but there's a certain MacGuffin-like quality to science fiction: If you strip away the sci-fi bits and still have a good story and compelling characters, and if the sci-fi itself doesn't distract from it, you have a great book. I mean, what is The Moon is a Harsh Mistress if it isn't a work of revolution fiction or a critique of colonialism. How is the theme of A Space Odyssey all that different from the Genesis narrative of Adam and Eve in the Garden of Eden? Isn't the Monolith merely the Tree of Knowledge? Isn't the Foundation Trilogy basically a fanciful version of Gibbon's Decline and Fall... mixed with a healthy dose of Ludwig Boltzmann? Ben Bova's works are a socialist critique of modern capitalist excesses. It goes on and on: well respected sci-fi can always be reduced to core themes that are universal to the human condition. There's rarely been a well respected and well read work of science fiction which is just a series of fanciful inventions that goes nowhere interesting. They can be adventure stories, social critiques, religious allegory, whatever, but science fiction is merely a setting and not a theme unto itself, at least not when it is done by those that critically and commercially are regarded as doing it best. --Jayron32 22:17, 6 November 2012 (UTC)

RE: 'In good science fiction, the "science fiction" elements blend in or melt away in ways that make them part of the background of a really good story'. I disagree. I want the sci-fi elements up front. One thing I disliked about the original Outer Limits was how they often felt the need to put some type of "human interest" story up front, like whether two of the characters will rekindle an old romance. If I wanted to see that, I'd watch a soap opera or read a Danielle Steel book. StuRat (talk) 22:59, 6 November 2012 (UTC)

Again, De gustibus non est disputandum. --Jayron32 04:12, 7 November 2012 (UTC)

Indeed. So don't tell people it's better not to try. There are oddities like Star Trek Star Fleet Technical Manual that actually sell, (besides, to the purist sales don't matter in matters of art). I think the most memorable sci-fi must honor both science and art - I find stories such as 20,000 Leagues Under The Sea and Blowups Happen to be some of the greatest of the genre, indeed, well worth appreciating even a century after the real technology has actually been developed. Wnt (talk) 15:45, 7 November 2012 (UTC)

Also note that while Clarke used magic technology in one of his monoliths, I think it was actually one of the weakest parts of 2001:A Space Odyssey (the ape-man gradually learning how to tie a crude knot, with the afterthought that "his DNA was being changed") By comparison TMA-1 was a simple land mine, activated by solar power and sending the signal that ultimately blows up Jupiter. Accurate technical details like the gravitational slingshot, or the space elevator from The Fountains of Paradise, were far more important for the success of his stories in my opinion. Wnt (talk) 16:03, 7 November 2012 (UTC)

The problem with The Stand isn't that it's a horror fantasy story, or that it contains mystical, magical elements that drive the characters and events of the second half of the book. It's that there's a 'bait and switch'—in that the first part of the book comes across as straight science fiction, almost hard science fiction. Back when it was published in 1978, the experienced genre fiction reader would have been exposed to books like Stewart's Earth Abides (1949), Shute's On the Beach (1957), and of course Crichton's The Andromeda Strain (1969). The Stand starts off in that familiar vein, working with a horrifying but plausible scenario. A reader has to get an awfully long way in to The Stand before realizing that King has abandoned his interesting apocalyptic (and post-apocalyptic) story for some hokey bullshit about demons in Sin City. It feels like King started out writing a character-driven science fiction epic, and then either ran out of ideas or got afraid that his 'regular' audience would miss the supernatural stuff, and so decided to lay some of it on with a trowel. I generally like it when an author does something creative and genre-busting, but in the case of The Stand, King produced an awkward Frankennovel rather than a seamless blending of sci-fi thriller with fantasy horror. TenOfAllTrades(talk) 04:03, 7 November 2012 (UTC)

I have to generally agree with that analysis, but the bait-and-switch is only a problem in so far as it affects the dramatic impact of the story. If you are rabidly anti-supernatural, obviously you will be annoyed by the turn, perhaps enough to make you stop reading. But the plot itself remains strong enough to carry the book to a happy conclusion. If you want great apocalyptic without the supernatural, see Larry Niven's Footfall and Lucifer's Hammer, Heinlein's Friday, and Greg Bear's Forge of God. μηδείς (talk) 16:19, 7 November 2012 (UTC)

The science of time travel only appears briefly in the beginning of my proposed story. It's what the main character does in the past that matters. I just wanted opinions on the plausibility within the realm of sci-fi. Regarding the question of the Brownian motion, that is well beyond my knowledge of physics. I only have a layman's understanding of various aspects that I've learned from popular science books. The suggestion that his oscillation would create miniature explosions and implosions is interesting. Sending air in different temporal directions reminds me of a video that some physics students made a few years ago in which they tried to explain the science behind Hiro Nakamura's ability to travel through time. They stated that he would have to take air with him or he would suffocate during the time travel process. --Ghostexorcist (talk) 17:28, 7 November 2012 (UTC)

--Ghostexorcist (talk) 17:28, 7 November 2012 (UTC)

Go with it making a vacuum and causing a small thunderclap from where he's left, as well as an increase in body heat, dizziness, belching, nausea, farting, and minor symptoms of the bends at the new location. There's no guarantee that the air pressure at the target location would be equal to the place left from in any case. μηδείς (talk) 17:37, 7 November 2012 (UTC)

Yea, it might make sense to transport them in a space suit, so they can then gradually equalize the pressure before removing the helmet. This is the level of detail I'd very much like to see in sci-fi. StuRat (talk) 19:39, 7 November 2012 (UTC)

But the space suit is only going to help if he telewhatevers into a vacuum. Thet being an obvious risk, he'd be a fool not to wear one. Yet he will still have to deal with the bends if he teleports into an atmosphere, regardless of space suit. μηδείς (talk) 23:06, 7 November 2012 (UTC)

Why is that ? Are you assuming the air already present will merge with his body ? That would be nasty, yes. StuRat (talk) 23:14, 7 November 2012 (UTC)

I noticed no one has covered what I think would be a pretty significant effect of his "rapid phasing". If he is phasing at a frequency anywhere between 20Hz and 20kHz then there will be a constant buzz, hum or ringing at that frequency. He and everyone around him would hear it as he was phasing. 209.131.76.183 (talk) 16:18, 8 November 2012 (UTC)

Star Trek Star Fleet Technical Manual - the book which made me invent the phrase DRTFM (D is Don't). They went on about "primary yield = 10^18 J (equivalent to 1000 torpedoes), secondary yield = 10^9 J (equivalent to 500 torpedoes)".

Which was more than her engines could take imo. Shoot me now, Mr Scott. - ¡Ouch! (^{hurt me} / _{more pain}) 17:32, 10 November 2012 (UTC)

Mixing Oort clouds

I came across this diagram showing that in approximately 25,000 years Alpha Centauri will make its closest approach to the Sun - approximately 3 light years. The diagram indicates that the Oort cloud is about 1.5 light years in radius (somewhat more than the Oort cloud article says). Assuming that Alpha Centauri also has an Oort cloud similar in size to the solar system's Oort cloud, it seems possible the two clouds might overlap to some extent. Is there likely to be any mixing of material between the two systems? Astronaut (talk) 18:53, 6 November 2012 (UTC)

Possibly, but the extreme low density of both means that gravitational interactions will be minimal, much less any actual collisions. However, the orbital periods of Oort cloud objects around the Sun are so slow, that even the slightest deflection could have noticeable impact after a few such rotations (which is many thousands of yeas). StuRat (talk) 19:17, 6 November 2012 (UTC)

The orbit of Proxima Centauri is not known or even confirmed, so guesses about an Oort cloud around the Alpha Centauri trinary are beyond speculative. μηδείς (talk) 19:45, 6 November 2012 (UTC)

By "not even confirmed" do you mean it's not known whether Proxima has positive or negative energy with respect to Alpha A/B, or what? —Tamfang (talk) 20:03, 6 November 2012 (UTC)

Sources I have read, including our own article, which was the most recent, say that it is not yet confirmed whether Proxima Centauri is gravitationally bound to Alpha Centauri A and B. I unreservedly, and wholeheartedly, recommend The Sparrow. μηδείς (talk) 21:35, 6 November 2012 (UTC)

How do you define over-overlapping, is it a synonym for superoverlapping or repeat overlapping, what is the difference between overlapping and over-overlapping? Plasmic Physics (talk) 20:47, 6 November 2012 (UTC)

None of these. It was a simple typo; and one I have just corrected. Astronaut (talk) 12:47, 7 November 2012 (UTC)

In that case, certainly - the amount of mixing is related to the time spent in overlap, the longer it remains in such a state, the more mixing should occur. That's all relative though, two factors (weak gravity, diffuse cloud density) impede the amount of mixing. Plasmic Physics (talk) 23:30, 7 November 2012 (UTC)

IQ/social group

Are there any serious studies regarding IQ by social group. Like IQ of Christians/Jews/Muslim, IQ of women/men. I know that such things would make many people ruffle their feathers, but it could be perfectly scientific. Comploose (talk) 19:06, 6 November 2012 (UTC)

Those aren't "social groups". And, you're right that it would be far too controversial. Scientists don't enjoy having their motives and research questioned, and much less do they death threats. StuRat (talk) 19:13, 6 November 2012 (UTC)

• See [10][11]. I found this in two minutes on Google. (Dragon's flight mentioned Religiosity and intelligence, with much more data) Please do not post that a question is unanswerable without making a fair effort to answer it! Wnt (talk) 16:08, 7 November 2012 (UTC)

What are they then? Comploose (talk) 19:20, 6 November 2012 (UTC)

Religion and gender. Not sure if there's a good collective term for them. Under anti-discrimination laws they are sometimes called "protected groups" (along with race, national origin, and maybe sexual orientation). StuRat (talk) 19:33, 6 November 2012 (UTC)

Please refer to race and intelligence.A8875 (talk) 19:18, 6 November 2012 (UTC)

Well, most of such studies of race are pretty dubious. It's easier to define gender than race.

First of all, you're not talking about gender; you're talking about sex. But anyway, it isn't necessary to have a precise definition of race to do a statistical study on what variables correlate with it. If you can get all observers to agree most of the time on what category someone belongs to, that's enough to see whether other things are correlated. The weakest part of such studies is probably trying to figure out what exactly you're measuring, not whom to count. --Trovatore (talk) 19:46, 6 November 2012 (UTC)

Maybe. Maybe not. A small, but not insignificant number of people are intersex or transgender (of various types). And that's not even getting into whether to categorize the various kinds of homosexuals and bisexuals in there somehow. Any time you try to categorize people in pretty much any way, you're going to find it stickier going than you could have imagined at the outset. Matt Deres (talk) 19:51, 6 November 2012 (UTC)

But once again, it really doesn't matter. The existence of intersex folks makes it problematic to claim that sex is a completely well-defined category, but it poses almost no problems for studying what correlates with sex, because the percentage of intersex persons is very small indeed. --Trovatore (talk) 19:53, 6 November 2012 (UTC)

Read The Bell Curve, if you dare. μηδείς (talk) 19:52, 6 November 2012 (UTC)

In addition to race and intelligence (already mentioned), we also have sex and intelligence and religiosity and intelligence. Dragons flight (talk) 20:06, 6 November 2012 (UTC)

it's 2012. scientists are publishing correlations between single nucleotide polymorphisms and phenotypes, and tracing the pathways linking them; talking about linking something as vaguely defined (whose actual existence as a discrete thing is debatable) as IQ, to something as crudely defined as race (based mainly on the degree to which one's outer integument processes tryptophan into melanin) is basically phrenology. IQ is just a test result in search of an underlying quantifiable, and race, sex, etc. are just visual classifications based on widely accepted sociological norms. (doubt it? how do you classify for this question of IQ, people who have XY chromosomes and female physiology, or those with XX chromosomes and male physiology? Whatever you answer, you've implicitly dropped the "sex" concept, and are now talking about physiology or chromosomes.) Gzuckier (talk) 02:43, 9 November 2012 (UTC)

I know I'm repeating myself, but it doesn't matter how you classify them. Or rather, it matters only if the effect size is very small. For at least 99.9% of your test subjects, the assignment as to sex is going to be completely unambiguous, so the ambiguous cases just add a little noise. --Trovatore (talk) 04:39, 9 November 2012 (UTC)

yeah, but you don't know if your effect due to 'sex' is genetic, or just sociological. it's the ones who are split on those two factors hat provide contrast in the statistical sense and enable you to differentiate between the two factors, causally. if you only stick with the cases where the two correlate you won't be able to answer what is presumably the form of the question most people are interested in: are the differences in IQ between your various groupings genetic/inherited, or just something society beats into their heads and/or biases the tests to show? Gzuckier (talk) 18:49, 9 November 2012 (UTC)

Interpretation of a study, particularly assigning causality, is always fraught. But that's an entirely separate issue. Determining whether there is a correlation (the actual thing that statistics can help you with) is not made particularly more difficult by the absence of a precise definition of biological sex. --Trovatore (talk) 19:00, 9 November 2012 (UTC)

Fun chat about cats and dogs. But let's not forget the question is about human IQ. Wnt (talk) 23:34, 7 November 2012 (UTC)

Coming soon: Cat/dog preference and intelligence. Evanh2008 (talk|contribs) 21:07, 6 November 2012 (UTC) Cats can live with their cerebra removed, dogs die. QED. Arrfff! μηδείς (talk) 21:31, 6 November 2012 (UTC) these guys disagree [12] Gzuckier (talk) 02:59, 9 November 2012 (UTC) It's clear that cats are smarter than dogs. A dog will do whatever you want him to do. How many intelligent people do you know who'll do that? --Trovatore (talk) 21:47, 6 November 2012 (UTC) Dogs will do whatever you want them to do, if and only if you convince them that there is a reward in it for them. As will cats. The difference is, dogs are genetically predisposed to identify the possibility of a reward being provided by a "packmate" who is a stable fixture of the environment, whereas cats are genetically predisposed to identify the possibility of rewards suddenly popping up quasirandomly where they need to be pounced upon quickly, or else they get away and you can just forget about them. Gzuckier (talk) 18:55, 9 November 2012 (UTC) It depends on whether you consider members of a political party to be "intelligent". ←Baseball Bugs What's up, Doc? carrots→ 23:12, 6 November 2012 (UTC) Ha! I always knew rebelliousness was a sign of intelligence. Thanks for that insight, Trovatore. -- Jack of Oz [Talk] 23:46, 6 November 2012 (UTC) Cats aren't rebellious. (Neither are dogs, unless they've been mistreated, in which case they're usually just crazy.) The former are just too stupid in most cases to know what is wanted of them. Note that dogs are aware there' "master's" eye direction, while cats are oblivious. Might as well brag about your pet tape worm's independent streak. μηδείς (talk) 01:39, 7 November 2012 (UTC) Mark Twain disagrees with you: “ But it ain't really insubordination, when you come to look at it right and fair -- it's a word that don't apply to a cat. A cat ain't ever anybody's slave or serf or servant, and can't be -- it ain't in him to be. And so, he don't have to obey anybody.... He's your friend, if you like, but that's the limit -- equal terms, too, be you king or be you cobbler; you can't play any I'm-better-than-you on a cat -- no, sir! Yes, he's your friend, if you like, but you got to treat him like a gentleman, there ain't any other terms. ” Couldn't have put it better myself. (Of course, I'm always listing the things I can put better than Mark Twain, but this isn't one of them.) --Trovatore (talk) 03:56, 7 November 2012 (UTC) It's hard to figure why someone would think dogs are "smarter" because they're subservient whereas cats are "dumber" because they do what they want. ←Baseball Bugs What's up, Doc? carrots→ 07:45, 7 November 2012 (UTC) I was able to train my cat to beg for her dinner. Dogs are often initially trained by giving them snacks to perform, too, but later they will do the tricks without a food reward. Cats, on the other hand, refuse to do tricks without the reward. So who's smarter ? StuRat (talk) 09:14, 7 November 2012 (UTC) Don't get me wrong. I love dogs too. The love and loyalty of a dog is a thing to behold. But the ugly truth known, I don't respect them as much as cats. --Trovatore (talk) 09:18, 7 November 2012 (UTC) I have an aunt who lives in Atlantic City. She loves me unconditionally and always gives me gifts. Down the street there's a slot machine. It gives me money too, but only if I pay it first, and only if it wants too. It's obviously much more intelligent than my aunt, more independent, and more worthy of my respect. μηδείς (talk) 17:33, 7 November 2012 (UTC) Medeis, I gather that you have never been friends with a cat. I think that's a pity. I would counsel you to be open to offers of such friendship the next time one comes your way. --Trovatore (talk) 22:29, 7 November 2012 (UTC) I have had pet cats and dogs. The best raised cats I have known were by a girlfriend who treated them as surrogat children. There were quite responsive to her stimulae, and attempted to breastfeed from her by pumping her chest with their feet well into old age. But they still didn't have anywhere near the intelligence, spontaneity, sociability, or intelligence of the average dog. There are stupid dogs, and even stupider dog owners. But the smartest cats don't come anywhere near an average dog in intelligence. I love all animals except incorrigible pests, so the only thing I really hold against cats is that they smell like cat piss. μηδείς (talk) 23:02, 7 November 2012 (UTC) Not in a healthy, neutered cat they don't. If they are urinating on themselves, something is seriously wrong. An intact adult male is liable to urinate anywhere, though. And a bladder infection can cause a cat to urinate in unusual places, too (they seem to associate the pain during urination with the location, causing them to urinate in a new spot each time). I've found dogs to smell far worse, between vomiting up roadkill they eat and urinating/defecating wherever, when you don't walk them quite soon enough. They also seem to have worse body odor, unless you bathe them regularly. And, all things being equal, a dog which weighs 10 times as much ought to generate 10 times as much stink. For example, a cat fart is probably too little to notice, but this is not true of a St. Bernard. StuRat (talk) 23:18, 7 November 2012 (UTC) Not enough free medical advice here for you, Wnt? :) μηδείς (talk) 02:09, 8 November 2012 (UTC)

Tipler Cylinder

The maths behind the Tipler cylinder seems to be very hard to find both on wikipedia and elsewhere. What exactly would happen to an object, say a rocket of some sort, that approaches it? The article says it can travel backwards in time, does this mean it exceeds the speed of light in some form? Wouldn't the rocket be affected by G-force and/or pressure and gravity?

I found out about the Tipler cylinder through a horizon documentary and it said it provided a possible way to travel back in time as oppose to a black hole, in which you cannot escape the event horizon. Does this mean that if a Tipler cylinder existed it would not have any form of event horizon? And that at any point the rocket could leave it's orbit? Does this mean light can escape it too? — Preceding unsigned comment added by 109.153.170.218 (talk) 21:59, 6 November 2012 (UTC)

Also some sources say it has to be infinitely long whereas others say it just has to be sufficiently long for the rocket to ever avoid the ends of the cylinder. Which are correct? — Preceding unsigned comment added by 109.153.170.218 (talk) 22:05, 6 November 2012 (UTC)

The spacetime contains closed timelike curves. The "timelike" part of this essentially means "slower than light"; you don't exceed the local speed of light but nevertheless end up back where you started, in space and time.

I see no reason to think that you couldn't arrange to make acceleration (gee forces) and tidal forces as small as you like on one of these closed timelike curves, but I'm just guessing.

Tipler says in the paper that there are closed timelike curves going through every pair of spacetime points, which means there are no event horizons: you can literally get anywhere in this spacetime from anywhere else.

Tipler argues in the paper that the cylinder doesn't need to be infinite, just very long, but he's just guessing. His arguments are (1) in Newtonian gravity the infinite cylinder solution is a good approximation to finite cylinders; (2) when the length goes to zero you get the Kerr black hole solution, which everyone believes in. However, the Kerr solution has an event horizon, so it's possible there's always an event horizon in the finite case large enough to prevent time travel. It's not clear why that would be true but it may well be true; Hawking conjectured that it is.

(For reference, here's the original paper and the metric in question is

$ds^{2}=H(dr^{2}+dz^{2})+Ld\phi ^{2}+2Md\phi dt-Fdt^{2}$

where a is the angular velocity of the cylinder, R is its radius, aR > 1/2 (in units where G = c = 1) and

$H=e^{-(aR)^{2}}(r/R)^{-2(aR)^{2}}\quad L={\frac {Rr\sin(3\beta +\gamma )}{2\sin 2\beta \cos \beta }}$

$M={\frac {r\sin(\beta +\gamma )}{\sin 2\beta }}\quad F={\frac {r\sin(\beta -\gamma )}{R\sin \beta }}$

$\gamma ={\sqrt {4(aR)^{2}-1}}\log(r/R)\quad \beta =\tan ^{-1}{\sqrt {4(aR)^{2}-1}}$

. This is a bizarre metric and doesn't look physically plausible to me. The coefficient L, in front of dφ², is sometimes negative, and since φ is cyclic (it's an angle), there are obvious CTCs in the form of loops around the cylinder at distances where L is negative. Presumably you can navigate to any spacetime location by spiraling around the cylinder at that distance as many times as needed.) -- BenRG (talk) 02:47, 7 November 2012 (UTC)

Thank you! That's exactly what I was looking for! You have been so helpful you don't even know! — Preceding unsigned comment added by 109.153.170.218 (talk) 18:02, 7 November 2012 (UTC)

Apparently the problem with the finite length cylinder is that, due to its extreme mass, it would be expected to collapse down to a disc in short order.[13] Wnt (talk) 18:34, 7 November 2012 (UTC)

Does a full moon cause higher tides, and if so, how much higher?

This was part of the story of Hurricane Sandy. Many tellers of the story included the "fact" that the full moon would make the flood water levels higher. Does it? How much? HiLo48 (talk) 22:53, 6 November 2012 (UTC)

Spring tide has the details. It's a well-known and well-studied phenomenon. AlexTiefling (talk) 22:58, 6 November 2012 (UTC)

As for "how much", I think it's generally in the 20% ballpark (with a corresponding reduction for neap tides), though I'm sure it varies by locale. You can look up tide gauge data for the US from NOAA; here's the Atlantic City, NJ gauge for the coming month. Tide range on the 15th is about 6.5 feet, contrasted with 3.5 feet on the 8th (still for the larger tide; the smaller tide that day is only 2.5 feet). — Lomn 23:26, 6 November 2012 (UTC)

(ec)Oh, and clarifying: the moon making the flood levels higher is, for all practical purposes, strictly a matter of the spring tide. The storm surge is over and above the normal tide level to yield the total flood height, but a hurricane producing an 8 foot surge at full moon will still produce an 8 foot surge at a half moon, too. Sandy was particularly bad in that landfall near NYC coincided with high tide and spring tide, though it fortunately didn't coincide with the higher high tide (see this plot from Sandy Hook, NJ right up to failure). — Lomn 23:33, 6 November 2012 (UTC)

It may be well known and well studied, but from my perspective, it's rarely well explained and often misunderstood. The only quantitative measure I can see in the Spring tide article is "causing tidal differences of inches at most". I have the impression that there's a popular misconception that because the full moon is brighter, the moon somehow causes much bigger tidal differences. The discussion at Talk:Hurricane Sandy#Should the Full Moon be mentioned? gives me just that impression. HiLo48 (talk) 23:30, 6 November 2012 (UTC)

Well, note that "inchest at most" is specifically referencing perigean spring tide particularly, and is "inches" with regards to an average spring tide. Spring tide vs average tide can be quite substantial. Another popular misconception (or just a factoid that's easy to miss) is that the full moon and the new moon produce identical extreme tidal effects. — Lomn 23:35, 6 November 2012 (UTC)

Well, I still don't see a clear answer to "How much?" Anybody? HiLo48 (talk) 04:17, 7 November 2012 (UTC)

I thought I was reasonably clear above. What else are you looking for? — Lomn 04:52, 7 November 2012 (UTC)

How much higher? There was a lot of qualification and negatives in your explanation. Is there a simple answer? Did you look at Talk:Hurricane Sandy#Should the Full Moon be mentioned? HiLo48 (talk) 07:05, 7 November 2012 (UTC)

The size of the tides varies greatly from one location to another. But one statistic that can be given precisely is in the "Forces" section of the article: the solar tidal force is 46% of the lunar. The spring tide occurs when these two occur at the same time. (The thing that can confuse the student is that although the color of the moon obviously doesn't matter, it indicates its position relative to the Earth and Sun and therefore whether the two tides occur at the same time)

I should add that I don't actually know that the highest tide must occur precisely at the full/new moon - I can picture a scenario where the solar tide raises the level of a long body of water and gives the lunar tide more water to work with when it hits a little later, but I don't know if that is physically relevant anywhere in the real world. Wnt (talk) 15:36, 7 November 2012 (UTC)

The spherical cow simple answer is "about 20%". For Atlantic City, NJ (selected for proximity to Sandy's landfall, and not being disabled like Sandy Hook), spring high tide is about 1 foot above mean high tide over a mean tidal range of about 5 feet. Atlantic City's neap high tide is similarly about 1 foot below mean high tide, and spring/neap low tides vary similarly versus mean low tide. Thus, I conclude that the cows in New Jersey are approximately spherical. — Lomn 23:41, 7 November 2012 (UTC)