Wikipedia:Reference desk/Archives/Science/2012 December 10

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December 10

Does Quantum entanglement apply to the entire visible universe?

Are we in a state of Quantum entanglement with those distant proto-galaxies at the edge of Hubble's fuzzy vision? Did we have time to mingle into a single cosmic scale wave function before Inflation (cosmology) went off like a bang? Just how far out of the box is the reach of the undead cat? Hcobb (talk) 00:46, 10 December 2012 (UTC)

No. Nonclassical entanglement isn't a normal state of affairs; it's very easily destroyed by environmental interactions. That's one reason building quantum computers is so hard. -- BenRG (talk) 02:54, 10 December 2012 (UTC)

But isn't the entire universe ruled by a single wave function and decoherence simply an mirage caused by our inability to fill in all the blanks? Coherence is said to be lost once one of the particles interacts with some "random element" from the outside, but that simply means that whatever is being interacted with is itself part of a larger coherence? Hcobb (talk) 03:23, 10 December 2012 (UTC)

Well, operationally speaking, there isn't any nonclassical result like Bell's theorem that applies to different galaxies. Philosophically speaking, in the many-worlds/relative-state picture (which is what you're probably thinking of), measurements entangle the measuring device with the system being measured, and this entanglement at the scale of the whole universe is responsible for the fact that the world appears as it does. I'm not sure it's right to call this entanglement, though. It's just plain old classical correlation, which is another name for entanglement that doesn't violate Bell's theorem. -- BenRG (talk) 05:21, 10 December 2012 (UTC)

What's to keep a distant galaxy from sending single photons at us followed by their observations to play Bell's theorem across the breadth of the Universe? Also wouldn't we use Entanglement-assisted classical capacity to chat with interstellar probes simply because of power considerations? There is no range limit on the wave function. Hcobb (talk) 16:55, 10 December 2012 (UTC)

Yes, in principle you can send one half of some Bell pairs toward another galaxy, wait until they've traveled far enough that they can be treated as part of that galaxy instead of this one, and then there's a small amount of nonclassical entanglement between the galaxies. This is an artificial situation maintained by careful isolation of the entangled particles. You could use those Bell pairs for superdense coding, but the amount of nonclassical entanglement would decrease as the Bell pairs were consumed. It's very hard for me to believe that this could ever be the most power-efficient option. For starters, the Bell pairs would presumably need active containment for the entire trip. -- BenRG (talk) 17:25, 11 December 2012 (UTC)

A typical particle is entangled with many particles far outside our horizon Count Iblis (talk) 23:42, 11 December 2012 (UTC)

That's the kind of entanglement that I called "plain old classical correlation". A world without correlation wouldn't make any sense. For life to exist there has to be a correlation between genotype and phenotype and between phenotype and reproductive fitness and between objects in the world and images on your retina and on and on for absolutely every aspect of the world. This is obvious and has nothing to do with quantum mechanics as such. All they're saying is that the universe is extremely uniform and the uniformity resulted from a common origin, not coincidence. -- BenRG (talk) 05:26, 12 December 2012 (UTC)

Lack of carb in meat

According to Chicken (food), it contains zero carb. Just curious, where does the muscle glycogen go? --PlanetEditor (talk) 05:11, 10 December 2012 (UTC)

It breaks down into glucose, which is quickly consumed by the cells' mitochondria. 24.23.196.85 (talk) 05:16, 10 December 2012 (UTC)

But why the stored glycogen is broken down? And how can a dead cell's mitochondria be active? --PlanetEditor (talk) 11:31, 10 December 2012 (UTC)

There may be trace amounts of glycogen or glucose in the meat, but a very small amount. Labeling laws allows rounding (usually to the nearest whole number, sometimes to the nearest 5, depending), so small amounts get rounded down to zero. --Jayron32 13:01, 10 December 2012 (UTC)

The mitochondria consume the glucose before they die - cell death is not an instantaneous process. Roger (talk) 15:25, 10 December 2012 (UTC)

Curie temperature of welding steel

I understand that stray drops of molten steel from a welding operation will not be deflected by a magnet because the steel is above its Curie temperature 700 deg C. However the drop cools as it falls and will become magnetic. Does its magnetism recover instantly or does it increase gradually over a number of degrees aabout the Curie point? Will the falling drop aquire a cooler magnetic shell around a paramagnetic interior? Is there a formula for the cooling of a molten drop falling in air? SkylonS (talk) 09:32, 10 December 2012 (UTC)

See Curie's Law. The long and short of it: Below the Curie temperature, magnetization is inversely proportional to the temperature, whereas above it, the steel does not magnetize and its magnetic susceptibility is inversely proportional to the difference between the steel's actual temperature and its Curie temperature. The steel also exhibits critical behavior at its Curie temperature -- which means that it changes abruptly from paramagnetic to ferromagnetic as it cools down past its Curie point. 24.23.196.85 (talk) 00:57, 11 December 2012 (UTC)

The drops will also be affected by the current induced by moving past a magnet, the effect would be to repel the drops. Dmcq (talk) 19:03, 11 December 2012 (UTC)

When toilets flush

What determines whether a toilet's flush will be more... forceful? Stronger? Basically, what makes it so that some toilets barely trickle the water and waste out while others make you think that the whole of reality will be sucked down the pipes? Is it a difference in altitude over where the sewer/septic system is? Or a combination of other factors? Dismas|^(talk) 11:58, 10 December 2012 (UTC)

It may depend on local water pressure in pipes and on toilet's construction, as well as on the amount of water in toilet cistern. Brandmeister^talk 14:39, 10 December 2012 (UTC)

Yes, the amount of water discharged from the cistern, the rate at which it is discharged, the height of the cistern above the toilet, and the dynamics of the flow, are all significant, but the pressure in the pipes is a factor only in the time it takes to refill the cistern. Dbfirs 16:24, 10 December 2012 (UTC)

Toilet#Water usage may be helpful. Duoduoduo (talk) 15:09, 10 December 2012 (UTC)

Height above the sewer line is not a factor, except in the rare cases where the sewer backs up all the way to the toilet. The size of the discharge hole in the bottom is also important, and any clog will reduce that. The infamous low flow toilets, which may require several flushes instead of one, are one cause of poor flushing. StuRat (talk) 18:30, 10 December 2012 (UTC)

Why is solid carbon at room temperature much denser than minus 300 degree oxygen solid?

Carbon atoms are lighter and larger. 96.246.63.155 (talk) 13:42, 10 December 2012 (UTC)

What form of solid carbon do you mean ? Graphite, diamond, carbon nanotubes ? StuRat (talk) 18:27, 10 December 2012 (UTC)

Only answer I can come up with without actually doing the work of researching it: carbon forms four bonds, allowing for packed crystal lattices, while oxygen almost exclusively forms O₂ molecules, which do not pack well at all. i kan reed (talk) 21:59, 10 December 2012 (UTC)

But the OP asked about it at "minus 300 degree oygen solid", which does not make any sense temperature wise or in the english language, but presumably is meant to mean "at 300 K below room temperature, where oxygen is solid". Which it will be. Oxygen is not O₂ molecules when solid, it is a continuous crystal structure. The OP is trying to compare room temperature carbon (a solid) to near zero K oxygen, which is a crystaline solid. Darned if I know why. Perhaps he meant the diamond form but forgot to say so. The OP needs to clarify what he wants. Wickwack 120.145.0.81 (talk) 00:39, 11 December 2012 (UTC)

He probably means -300°C. Yes, absolute zero is at −273.15°C, but they were just rounding imprecisely. StuRat (talk) 00:51, 11 December 2012 (UTC)

(ec) That would be below absolute zero, so in the everyday sense, there is no such temperature. There is a sense in which such a temperature could exist (see negative temperature) but it's "hotter than infinite temperature", so it doesn't fit with solid O2.

I would guess instead that the intent is −300 degrees Fahrenheit, but then it's incorrect, as O2 does not solidify until you get down to −362 F, if I remember correctly what I just looked up. --Trovatore (talk) 00:57, 11 December 2012 (UTC)

Solid oxygen is a crystal lattice of O₂ molecules. "Molecular" and "lattice" are not mutually exclusive terms. It's simply bound O₂ molecules connected in a lattice by van der Waals forces.[1] Someguy1221 (talk) 00:50, 11 December 2012 (UTC)

Only at very high pressures, I think. Wickwack 60.228.248.5 (talk) 01:56, 11 December 2012 (UTC)

No, it is true down to vacuum. At very high pressures, you can get O₈ molecules in a van der Waals lattice, but you never get a covalent lattice as with carbon. Someguy1221 (talk) 02:01, 11 December 2012 (UTC)

One would think people would take the time to make sure their questions make sense, that way we could spend our time debating the best answer instead of debating the meaning of the question. Just saying it... Dauto (talk) 15:46, 11 December 2012 (UTC)

No, that's ok. We should recognise that not everybody has english as their first or even second language. What annoys me is that, like in this case, when the OP is asked to clarify what he wants, he doesn't post again - that tells me we've all wasted our time - the OP has not come back to read what's posted. Wickwack 120.145.197.96 (talk) 00:51, 12 December 2012 (UTC)

I don't think English as a second language was the problem. The English is OK. The problem is that the question doesn't make sense. Dauto (talk) 04:23, 12 December 2012 (UTC)

AIDS

I just got done watching a documentary about AIDS in Africa, and it got me thinking, do black people have some genetic predisposition towards getting HIV? Their continent has AIDS as an epidemic and while some people may blame lack of education, There are many other poor, uneducated areas of the world where HIV is not epidemic, although it is still high, such as South America, and the more rural areas of South East Asia.--Wrk678 (talk) 13:59, 10 December 2012 (UTC)

AIDS is only an epidemic in southern Africa. I don't know are they too poor to afford (enough) condoms? Then that's the reason. You can't really end humping now can you? Sagittarian Milky Way (talk) 14:20, 10 December 2012 (UTC)

HIV originated in Africa, as such this continent still takes the brunt of the epidemic. Brandmeister^talk 14:33, 10 December 2012 (UTC)

Didn't it spread worldwide really quickly the first time a world traveler got it though? I believe Congo is the source but that isn't the place the hardest hit. Maybe places like Botswana with the ridiculous amount of AIDS are poor even by third world standards. It's hard to get poorer than sub-Saharan Africa (South Africa and a few others like maybe the Ghana with the hydroelectricity excepted). Sagittarian Milky Way (talk) 15:17, 10 December 2012 (UTC)

Actually Botswana is one of the wealthiest countries in Africa on a per capita basis, however with a high Gini coefficient the wealth distribution is very skewed. South Africa has the highest Gini coefficient in the whole world. Roger (talk) 15:32, 10 December 2012 (UTC)

Come on, people, we keep a copy of the world's largest free encyclopedia right behind the Ref Desk. Use it!

• Epidemiology of HIV/AIDS#Sub-Saharan Africa
• HIV/AIDS in Africa

Getting back to the original poster's question, it is true that some populations have a greater innate resistance to HIV infection. Carriers of one copy of the CCR5-Δ32 mutant form of the CCR5 gene have some resistance to HIV infection; individuals with two copies of the CCR5-Δ32 mutation are strongly resistant to HIV. It is estimated that roughly 10% of northern Europeans carry at least one copy of CCR5-Δ32, and perhaps 1% have two copies. CCR5-Δ32 is essentially unheard-of anywhere else in the world. By itself, however, this improved resistance in a small fraction of the population has a negligible effect on HIV infection rates in Europe (or elsewhere) versus those in Africa; the social, political, and economic factors contributing to the high levels of HIV infection and AIDS in sub-Saharan Africa are far more important. TenOfAllTrades(talk) 15:46, 10 December 2012 (UTC)

Right, ignore anything I said, those articles are very good. Basically, it's complicated. Wow, that is one crappy place to live. Sagittarian Milky Way (talk) 15:53, 10 December 2012 (UTC)

No small part of the African AIDS epidemic has been due to religion. The Catholic Church has consistently made empirically false claims about the effectiveness of condoms, and generally opposed contraception at every step. Since contraception is by far cheaper than education or treatment, this has greatly hindered attempts to tackle the epidemic. See Catholic Church and AIDS.

Also, I challenge the OP's comparison between sub-Saharan Africa and South America or Southeast Asia. Look at the 2011 UN Human Development Index. Almost every country in South America has a decent quality of life; Chile and Argentina have a Western-level HDI. Southeast Asia is indeed poor, but almost all of it has a "medium" HDI, whereas almost all of sub-Saharan Africa is "low". There's just no comparison between the poverty and loss of social order in this part of Africa and that in any other part of the world. There's a reason that most charity TV ads you see are about Africa rather than Haiti, China, the Philippines, or Papua New Guinea--because it really is much worse. --140.180.249.194 (talk) 18:19, 10 December 2012 (UTC)

I have to agree with IP 140. You'd be surprised how many negroes Benedict has had buttsex with. (Whoops, no refs? Who cares! They are Catholics!) μηδείς (talk) 21:41, 10 December 2012 (UTC)

Was that supposed to be a sourced and helpful contribution, or are you just PMSing like you always do? --140.180.249.194 (talk) 22:09, 10 December 2012 (UTC)

Medeis, you would do well to read John Scalzi's brief commentary on The failure mode of clever.... TenOfAllTrades(talk) 03:00, 11 December 2012 (UTC)

Nice one Ten --Lgriot (talk) 08:25, 11 December 2012 (UTC)

John Scalzi is very wise... --Jayron32 13:02, 11 December 2012 (UTC)

The factors involving the HIV epidemics in Africa are complicated and, frankly, not yet fully understood even by experts. There are many things going on there, and any single-variable, pat answer is going to be inadequate. (I don't claim to be an expert on this, but I've been surprised as at how much question there still is on some of the basic questions, like to what degree needles versus sexual activity are responsible for the cases.) That being said, I don't think anybody who has studied the issue thinks that genetic predisposition has anything significant to do with the rate of exposure there. "Dire poverty" is obviously the context for the answer(s) but it's not the answer itself. --Mr.98 (talk) 02:38, 11 December 2012 (UTC)

Dilated eyes

Last time I had my dilated eye exam I drove home after dark and all bright lights had a starburst effect around them. What causes the starburst? (I thought maybe it had to do with the pupil not being a perfect circle but I don't know if that would explain it.) RJFJR (talk) 17:15, 10 December 2012 (UTC)

Star-bursts or halos? Have you had any laser work done? Do you have astigmatism – if so at which angles (for both peepers)?--Aspro (talk) 17:50, 10 December 2012 (UTC)

Was it in your eyes or in the windshield - moisture, soap residue, construction of the glass... 88.112.41.6 (talk) 18:19, 10 December 2012 (UTC)

'star-bursts' (rays around bright lights). I didn't think it was the windshield but I suppose it could have been the windshield and I noticed the effect much more due to the dilated. RJFJR (talk) 22:31, 10 December 2012 (UTC)

I too have noticed the star burst effect after dilated eye exams, bad enough to make using a PC difficult, but I'm sure it didn't happen when I was young. Perhaps it is due to imperfections in the cornea and/or lens, and isn't noticed normally because the aperture is small enough to avoid most of the imperfections. Wickwack 120.145.0.81 (talk) 00:48, 11 December 2012 (UTC)

This is unscientific, but I suspect it has more to do with the fact that your iris dilator muscle as well as your ciliary muscle both are affected by the norepinephrine in the drops they give you, and that makes it more difficult to focus, leading to that effect. However, that's mostly just an educated guess. I did find one medical text that referred to halos after certain eye surgeries apparently due to an optical phenomenon with larger pupils, which may be of some interest, but I don't have the technical background to know if that answers your question. ISBN 0865777594, page 358. Shadowjams (talk) 17:17, 11 December 2012 (UTC)

Let's be clear here that we're not able to give advice about anything medical, and besides, the eyes were just diagnosed. But a factors such as corneal neovascularization from contact lens use, or any other kind of opacity/haze anywhere in the anterior part of the eye, could lead to less perfectly clear areas near the edge of the cornea having an effect when the iris is kept fully open. Wnt (talk) 03:27, 12 December 2012 (UTC)

I can't see how it could be due to lack of focus - this is about a starburst effect, not bluring. In any case, my main eye defect is a complete loss of the ability to focus, combined with abnormally long eyeballs - the combined effect is that instead of my natural relaxed focus being to infinite distance like a normal person, combined with the ability to focus thru eyes muscle effort down to 200 mm or so, my eyes are permanently stuck on being focussed to 350 mm - which is just fine for using a PC or reading a book. I notice the starbursts on things in focus, not things out of focus. Wickwack 124.178.149.151 (talk) 07:26, 12 December 2012 (UTC)

Spherical aberration occurs due to light passing through the peripheral portion of the crystalline lens. [2] Location (talk) 06:12, 13 December 2012 (UTC)

So? What has this to do with eyes? Spherical aberation arises with manmade lenses because it is easy to accurately grind a spherical surface, and hard (meaning expensive) to grind an optically correct surface. This does not apply to the eye. In any case spherical aberation causes blurring, not starburst effect. Wickwack 121.221.33.51 (talk) 03:10, 15 December 2012 (UTC)

You don't know what you're talking about. The reference I supplied confirms that spherical aberration occurs in dilated eyes exactly as I explained above, and your understanding that it manifests only as blur is incorrect. Starburst, glare, and halos can occur on things otherwise "in focus" because most of the light (i.e. that which is passing through the crystalline lens closest to the optical axis) is indeed focused on the retina. Location (talk) 05:43, 15 December 2012 (UTC)

Spontaneous generation vs. abiogenesis

What is the difference between spontaneous generation and abiogenesis? I think spontaneous generation can be summed up by "maggots come from flesh", where as abiogenesis can be summed up by "first population of cells comes from a population of organic molecules in the primordial soup in the early earth. It seems to me that both are trying to suggest that life comes from non-life. 75.185.79.52 (talk) 19:27, 10 December 2012 (UTC)

Convenience links: Spontaneous generation, Abiogenesis. hydnjo (talk) 21:27, 10 December 2012 (UTC)

Yes, both of them are life coming from non-life, though the two ideas are very different they do have that fact in common. Dauto (talk) 20:34, 10 December 2012 (UTC)

The difference is that one says it happens all the time, and the other that it's an extremely rare event that only occurs once over billions of years and, perhaps, billions of planets, or even an infinite number of universes. Also, spontaneous generation is supposed to produce far more complex organisms, initially. StuRat (talk) 20:37, 10 December 2012 (UTC)

The (long-ago-dismissed) idea of spontaneous generation really applied to large organisms. If you left a bunch of cheese lying around the house, soon afterwards you have an infestation of mice...so mice are made from mouldy cheese(!)...that kind of thing. It was a stupid idea that was widely dismissed pretty much as soon as it had been suggested. We knew how mice reproduce(!) and cheese isn't involved.

Abiogenesis is a much more subtle idea - which is by far the most widely accepted scientific explanation for the beginning of life. It suggests that life arose as just one tiny step - from molecules that cannot not make copies of themselves to molecules that can - and once a single self-reproducing molecule had formed and copied itself, evolution would kick in and everything else would follow from that. But abiogenesis isn't about large scale organisms...it talks about things like individual RNA molecules. You wouldn't exactly say that an RNA molecule was "alive" but the steps from that to the most primitive bacterial cell are never especially large ones. Evolution drives those steps once a basic self-reproducing molecule had come into being more or less by chance. The threshold at which we'd consider something to be "alive" is a fuzzy one - not everyone agrees on a single definition. So the point at which "non-life" turns into "life" becomes a matter of semantics rather than science. I would define abiogenesis as that point where the primordial soup became susceptible to evolution. It's a cleaner definition than "non-life" to "life". SteveBaker (talk) 20:07, 11 December 2012 (UTC)

I agree with everything except your first statements. Spontaneous generation wasn't a "stupid idea" that "was widely dismissed pretty much as soon as it had been suggested." It persisted well into the 19th century and existed for centuries prior to that. It was eminently empirical — maggots and tiny flies do seem to come pretty much out of nowhere if you aren't controlling for enough variables. It seems "stupid" to us today because it is totally incompatible with our thinking on what life is and how it works, but it fits very much within the Romantic manner of thinking about life of the early 19th century, much less earlier periods. --Mr.98 (talk) 00:03, 12 December 2012 (UTC)

Transportation gunpowder ingredients world war I era

Research for historical novel. Need to know how munitions raw materials such as camphor, pyrite and saltpeter were packaged for bulk transportation in 1914. I've tried many web searches to find information from this period, with no success so far. 98.125.189.95 (talk) 19:40, 10 December 2012 (UTC)

By the time of WWI, gunpowder (often referred to as "black powder") was rather obsolete as an explosive. Modern high explosives, mostly TNT, were in use for the bursting charges of artillery shells, aircraft bombs and those huge mines that they set off in tunnels under the enemy trenches. Low explosives, such as cordite, were used as propellants, to fire shells and bullets out of guns and mortars. I believe that gunpowder was still in use for artillery fuzes. There is some information about British munition plants in Filling Factories in the United Kingdom which says that "The Filling Factory's raw materials, such as TNT, RDX, or propellants, such as cordite, were manufactured in National Explosives Factories (World War I) or Explosive ROFs (World War II) and transported, by railway trains, to the Filling Factories for filling into munitions, produced at other plants." Not much to go on, but it might give you some useful search terms. Alansplodge (talk) 22:04, 10 December 2012 (UTC)

I wonder whether you'd get some useful information by reading about some of the failures of such bulk storage. The resulting explosions were large and prominent events - so lots has been written about them - and I'd imagine that you'd find information about storage and transportation in those accounts. Check out List_of_the_largest_artificial_non-nuclear_explosions#World_War_I_era and start following the references. SteveBaker (talk) 20:35, 11 December 2012 (UTC)

Gays and noses

Women have more sensitive noses, they can smell more things then men. (so I heard).

If its true, does gays (men) have a similar ability? does they have a better noses then straight men?

Maybe some scientist already did experiments about it? Yes, this sounds like a really dumb question to investigate, but I'm sure I'm not the first one in the world who think about it :)

UPD: Sorry if my question sounds arrogant or insulting, its because bad wording (I'm not a native English speaker). Also, you can make fun from my bad English (if you think its funny) --Ewigekrieg (talk) 21:03, 10 December 2012 (UTC)

You might be the second. I also did no know that gays are all men or that there were none left. I guess you learn something new...165.212.189.187 (talk) 21:08, 10 December 2012 (UTC)

No offence. I didn't say gays are women or something. One of my friends is a gay and he is a definitely a man (and a good guy) --Ewigekrieg (talk) 21:16, 10 December 2012 (UTC)

The issue is that some gay people are women, gay refers to a person of either sex. You were also using the passed tense: "did gays have a similar ability" which implies that homosexuals have vanished. Obviously you didn't mean any of this and intended to refer to gay men in the present tense, but this is a reference desk on the internet so a degree of pedantry and perhaps snark is to be expected. --Daniel(talk) 21:25, 10 December 2012 (UTC)

Speaking of which, if you're going to correct others, you have to be squeakily correct yourself. The term is past tense, not "passed tense". Also, he made it clear he was asking about male gays; he wasn't saying that all gays are male. -- Jack of Oz ^[Talk] 11:49, 11 December 2012 (UTC)

There's a reference desk guideline that would seemingly frown on a snarky response to an obvious verb conjugation mistake in a non-native English speaker's question. Red Act (talk) 04:13, 11 December 2012 (UTC)

He added the "(men)" after, Jack. And The question came across extremely ignorant and snarky in its own right, regardless of improper verb conjugation. is there a ref desk guideline for that, Red?165.212.189.187 (talk) 13:49, 11 December 2012 (UTC)

Whether 'gay' includes men and women or just men is a matter of contention (I am not sure by whom) which leads to the rather ponderous LGBTVXYZ terminology. I occasionally typeset essays discussing the matter. I can't remember a word anyone said. μηδείς (talk) 02:18, 12 December 2012 (UTC)

Gay men do have a greater olfactory sensitivity to some pheromones than do straight men[3], and the activation of neural circuitry in response to pheromones is different than in straight men; see Neuroscience and sexual orientation#Response to pheromones. But I'm having a harder time finding information about olfactory sensitivity in gay men in general. Red Act (talk) 21:45, 10 December 2012 (UTC)

As a bisexual I can tell you that I have seemed to have a much higher sensitivity to the sexual smells of both men and women, in comparison even to heterosexuals for the smell of the opposite sex. That's OR, of course; not that there's anything wrong with that. μηδείς (talk) 00:22, 13 December 2012 (UTC)

"Gays" do not form a well-defined biological group. But I smell great. μηδείς (talk) 21:38, 10 December 2012 (UTC)

You seem to smell like anyone else on the internet Medeis. OsmanRF34 (talk) 22:17, 10 December 2012 (UTC)

And next time you tickle my chocha with your nariz, I'll admit that fact, Os. μηδείς (talk) 22:33, 10 December 2012 (UTC)

The olfactory has given way to the information age. Bus stop (talk) 11:59, 11 December 2012 (UTC)

Some of us can read Portuguese. Dauto (talk) 15:39, 11 December 2012 (UTC)

And most everybody else can read inuendoese.165.212.189.187 (talk) 19:45, 11 December 2012 (UTC)

In you end, oh! --Jayron32 00:57, 12 December 2012 (UTC)

It could be that a nosegay is needed. Bus stop (talk) 13:49, 12 December 2012 (UTC)

If this meme gets legs any longer it'll be on the next episode of The Simpsons. μηδείς (talk) 00:18, 13 December 2012 (UTC)

It's innuendo, not inuendoese. Now what's wrong with being an Inuit already? - ¡Ouch! (^{hurt me} / _{more pain}) 09:54, 13 December 2012 (UTC)

Maybe the OP is confused by the term Nosegay. ←Baseball Bugs ^{What's up, Doc?} carrots→ 12:41, 13 December 2012 (UTC)

"Gays" ("gay people" being the more polite term) are defined as a group by identifying as gay, in much the same way as, say, women or French people or Christians are. Biology and sexual orientation discusses some of what is known about the connections between biology and sexual orientation, and there is evidence of correlations between aspects of physiology and sexuality, so what the OP is suggesting doesn't seem impossible. Our article olfaction says "In women, the sense of olfaction is strongest around the time of ovulation, significantly stronger than during other phases of the menstrual cycle and also stronger than the sense in males". It doesn't say anything about sexuality. 130.88.99.231 (talk) 15:46, 13 December 2012 (UTC)

Leaving the Solar System

Let's say I build a spaceship to travel to the stars. To accelerate the ship to the highest possible velocity, I aim it at multiple planets and make use of gravity assist. Assuming I don't really care in which direction my ship leaves the Solar System, what is the maximum velocity I can achieve? Can I also use the sun as a slingshot? Hemoroid Agastordoff (talk) 21:47, 10 December 2012 (UTC)

I think the question leaves way too many open variables to even hazard a guess. What is power source, your fuel supply, starting position(earth surface, leo, the moon), the frame of reference from which you are comparing your velocity? With "near future" sci-fi like p-b11 fusion ion drives, starting in L3, using the SUN, and unlimited resources to design your rocket, you'd get multiple orders of magnitude more momentum than a fairly typical liquid-solid multi-stage rocket launched from cape Canaveral. To make it out of the solar system, you'd need a (sun's frame of reference) velocity of 10 km/s. We've only ever launched two rockets with the intent of passing the edge of the solar system: Voyager probes 1 & 2. Voyager 1's current relative velocity to the Sun is 17,043 m/s. Voyager 2's is closer to 40 km/s. Sort of answer your question? i kan reed (talk) 22:09, 10 December 2012 (UTC)

Voyager 2 is 15, 16 km/s or something. Pioneer 10 and 11 have messages to aliens (sounds intentional to me) and New Horizons is also leaving. Sagittarian Milky Way (talk) 22:32, 10 December 2012 (UTC)

I think the total speed you could reach is limited only by the drag experienced by encountering particles in the solar system (if this limit didn't exist, you'd eventually run into the speed of light limit). You could use the Sun, too, but the solar wind would decrease your speed as you approached (and then increase your speed as you leave, but to a lesser degree, since you are going faster then, thus exposed to it for less time, and also because your velocity relative to the solar wind is less, then). StuRat (talk) 22:18, 10 December 2012 (UTC)

You should get it all taken back though, and would require a bunch of time too (multiple inner planet assists, or maybe going all the way out to Jupiter just to get close to the Sun). Well you do go faster for awhile, don't know if it's quicker to just start outwards in the first place. Unless you have a reallly long timeframe and are talking about altering the probe's galactic orbit. Sagittarian Milky Way (talk) 22:32, 10 December 2012 (UTC)

See gravity assist, unpowered assists only add (non-transient) speed because of the planet's motion. Sagittarian Milky Way (talk) 02:45, 11 December 2012 (UTC)

Our article says, with each pass, the initial velocity V (relative to the sun) can be increased to V + twice the planet's velocity (relative to the Sun). However, if we're talking about speeds relative to the galaxy, then V (relative to the galaxy) can be increased to V plus twice the Sun's velocity (relative to the galaxy). StuRat (talk) 02:53, 11 December 2012 (UTC)

The sun cannot be used as an assist because it is the dominating body. However, its gravity can prove useful to approach a planet which can be used.

Once you get past the escape velocity of the solar system, you are not coming back, so then, you would not make many other passes. There can be slight exceptions if Mercury pushes you above the limit, and you happen to pass Jupiter on the way out, but that approach comes with its own limits. One, it's not possible to get back to planets "behind" you (Mercury in that example) once ypou're well beyond the planetary (Jupiter's) escape velocity, because you won't be close enough for long enough time to make the turn. At least not turns like the "simplified" one shown in the Gravity assist article.

Basically, gravity assist is a great method if you're limited to chemical propellants and/or low thrust ratings, because the kick you get is virtually "free", compared to the cost of more delta v. Once you have a continuous-beam plasma thruster with a cheap power source, you can just "floor it" without caring too much about assists.

Things would change again if you had a binary Black Hole to work with; these do crazy things to mass, light, and spacetime itself. You could go from near-zero to 42% c in one pass (or so I've read). - ¡Ouch! (^{hurt me} / _{more pain}) 11:38, 11 December 2012 (UTC)

Ouch: don't take everything you read about physics from Stanislaw Lem at face value. That use of a black hole is a literary device to make the story more interesting. – b_jonas 19:00, 11 December 2012 (UTC)

I've read it in a magazine, not in Fiasco, nor The Forever War or Neutron Star. It was non-fiction and scientific in tone, and although I can't give the ref (it was in the 2nd millennium), it did mention the 42% c.

On top of that, I'd doubt that one Black Hole can do the trick. Unless it's moving fast or rotating near the theoretical limit. The Penrose process could be useful, tho. It should rival annihilation in terms of delta v, with a rotating Hole that's known to exist. - ¡Ouch! (^{hurt me} / _{more pain}) 09:56, 13 December 2012 (UTC)