Wikipedia:Reference desk/Archives/Science/2010 January 26

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January 26

Cloning question

Have we yet devised a theoretical method by which the memories and personality from the original might be restored/awakened in a clone? I know that there was some idea a while back of actual memories being encoded in genetic material but I don't know if that's been discredited now. —Preceding unsigned comment added by 95.148.105.150 (talk) 00:20, 26 January 2010 (UTC)

It sounds pretty fishy to me. Considering we don't really have a great understanding of the neurological basis of memory anyway, but the formation of memories is clearly somatic and not genetic, the idea that you could code memories in genes seems rather... unlikely. We'd need a far better understanding of how memory itself worked in the brain to begin with, much less a light-years superior understanding of the human genome. --Mr.98 (talk) 00:37, 26 January 2010 (UTC)

Aside from any other consideration - there is nowhere near enough 'space' in a DNA molecule to store that much memory. At best - each 'letter' of the DNA is one of C,T,G,A - two bits of information per base-pair. Human DNA has about 3x10⁹ 'letters' so it can store at best 6,000,000,000 bits - less than 1Gbyte. That's just pathetic! You can easily store more than that on a regular CD-ROM. My PC has five times that much main memory! And bear in mind that this DNA also has to contain enough information to construct our clone's entire body, to run it's biochemistry, to repair and regrow bits of the body that fail, etc. There is simply not enough space to store the memories of even a few days let alone a lifetime. So - a clone is no different than an identical twin - it would be born just like any other baby - grow, learn, experience the world and end up a very different person. Memories in the brain are retained over the long term as physical connections between neurons which change over time. The clone would have to have an exact duplicate of all of those neural connections - but that can't be because a clone has to be grown from a baby - and the baby clone's brain doesn't have enough space - enough cells to store an adult brains' worth of memories. So this is a complete and utter bust. There is no way to do this. SteveBaker (talk) 02:14, 26 January 2010 (UTC)

Though when you consider that ~30 billion memory-associated neurons in the cortices and hippocampus have 6,000,000,000 bits each, the capacity is not quite so pathetic. Each cell is terminally differentiated, so it doesn't actually need to contain enough information to construct our clone's entire body, just enough to code for the transcriptome of that particular neuron. How much genome variation (coding capacity) there is between neurons is currently unknown, but there are some suggestions that they could be quite significant and play a role in brain development and maintenance. The idea of genetic memory is a bust, of course, but not necessarily because of limited coding space. Rockpocket 06:32, 26 January 2010 (UTC)

Oh, sure, memory could be stored using DNA (although there is no evidence to suggest it is and plenty to suggest otherwise), but that wouldn't help a clone. When you clone someone you only get to use one set of DNA, not one for each cell. --Tango (talk) 10:30, 26 January 2010 (UTC)

Yep - and that's why Rockpocket's answer is not relevant to this question. If our memories were routinely stored in DNA, consider how long it would take to retrieve one. Somehow, the brain would have to locate the right cell that contained the DNA where the answer was stored - then somehow duplicate the right section of that DNA and use that to provide the answer. How would the indexing mechanism work? How would we find the right molecule? No - the brain is a computing machine and the connectivity of the neural net is what stores information AND allows it to be retrieved so quickly. SteveBaker (talk) 13:54, 26 January 2010 (UTC)

You would need to use some kind of nano-tech duplication technology (which no-one has invented yet) and actually copy the body, including the brain. If you use a normal cloning technique it is, as Steve says, just like having an identical twin. --Tango (talk) 02:19, 26 January 2010 (UTC)

This is another form of Lamarckism, and has long been discredited save for some fringe scientists who keep trying to bring it back. It is futile. 66.65.139.33 (talk) 02:20, 26 January 2010 (UTC)

Such memory transfer is of course a popular device in Science Fiction, where it may be used to raise philosophical questions about the nature and continuity of identity and selfhood in addition to being a useful plot device. A recent example of the many novels, etc, exploiting the idea is John Scalzi's Old Man's War. 87.81.230.195 (talk) 02:31, 26 January 2010 (UTC)

If by 'restored' you mean, copy the mind of the original into the clone? As Mr.98 says, our understanding of the brains memory (or even its 'programming') is not good enough. It seems an unlikely possibility. But, then so was flying etc. I would think ESP is more likely than Genetic memory. Not deriding your question, but the general concept (with a different mechanism) is also nicely addressed in the novel "To Your Scattered Bodies Go" by Philip Jose Farmer. Note I wrote this(slowly) while others were posting so it doesn't take into account all the erudite responses before me. --220.101.28.25 (talk) 02:44, 26 January 2010 (UTC)

Lamarckism as referred to by IP 66.65.139.33 above, DNA & Genetics--220.101.28.25 (talk) 05:43, 26 January 2010 (UTC)

Pretty much nobody nowadays believes that memories are stored using DNA -- the almost universal belief is that they are stored by modifying the synaptic matrix, that is, the connections between brain cells. So, replicating the full set of memories would mean replicating the synaptic matrix, which would involve nanoengineering far beyond our current capabilities. It isn't even just a matter of making the synapses match: the numbers and positions of brain cells are themselves dependent on experience, so a clone and an original won't even have matching sets of brain cells. Looie496 (talk) 16:39, 26 January 2010 (UTC)

What our question-asker is probably thinking of is the theory of Memory RNA. The Wikipedia article isn't very good, but it hits the important fact that the theory is "now discredited". APL (talk) 16:46, 26 January 2010 (UTC)

Appreciate the answers. Thanks. So it's completely beyond the realms of possibility that if/when humans are cloned, that the clones might grow up and experience unexpected 'echoes' of the memories or character traits of the original? --95.148.104.185 (talk) 00:42, 27 January 2010 (UTC)

That's correct. The clone would essentially be an identical twin. Identical twins can sometimes be quite similar to each other in thought and behavior, though some of this is undoubtedly due to simmilar upbringing. So I suppose that a clone might have certain underlying personality traits that are the same as the original. Anything developed after birth, though, could not show up in the clone. Inheritable genetic material is not changed by the environment, except in extreme cases like exposure to ionizing radiation. The clone could not recognize an old friend of her parent or find her way around her parent's childhood hometown. Buddy431 (talk) 02:17, 27 January 2010 (UTC)

moonrise

Is there a pattern/schedule of the moon setting and rising like the sun? One night at around 7:00 PM, I happened to see the moon in a short distance from the horizon. On another night at around 7:00 pm, it was already at the "noon" position. --121.54.2.188 (talk) 00:55, 26 January 2010 (UTC)

Basically, it rises ~49 minutes 50m28s later each time, because it is in orbit around the earth and the earth has to turn a bit farther than one day's worth to catch up. --Tardis (talk) 01:09, 26 January 2010 (UTC)

Cool, so the moon doesn't only change faces but schedules as well. --121.54.2.188 (talk) 01:19, 26 January 2010 (UTC)

Not sure what you mean by "change faces". It only ever shows the same face to Earth, but not all parts of it are illuminated all the time. Re the "schedule", did you ever notice that a full moon always rises shortly after sunset? That's when its Earth face is getting maximum illumination from the Sun; but non-full moons rise at other times, when the Earth face is at some angle to the Sun. -- Jack of Oz ... speak! ... 02:54, 26 January 2010 (UTC)

My bad, I meant phases, not faces.--121.54.2.188 (talk) 05:51, 26 January 2010 (UTC)

If you are trying to understand what Jack is saying and struggling to work out why it works, try drawing a diagram, it can be very helpful. --Tango (talk) 03:18, 26 January 2010 (UTC)

The article Lunar phase contains several (potentially) helpful diagrams. -- 174.21.135.237 (talk) 03:59, 26 January 2010 (UTC)

(I improved my approximation; I had been in a hurry.) --Tardis (talk) 19:58, 26 January 2010 (UTC)

A short answer is, when the moon is full it rises when the sun sets. Each day after that the moon rises later and later, and wanes, until it rises when the sun rises--the new moon. After that it appears as a crescent in the morning, setting soon after sunrise. Every day it rises later and later, and the waxes larger, until when full it once again rises when the sun sets. The article linked above will explain all this in more detail. Pfly (talk) 09:43, 26 January 2010 (UTC)

Small correction. A waxing crescent moon rises soon after the sun rises and sets soon after the sun sets. It is in the sky for most of the day, but not easily visible in daylight; it is most visible around dusk. A waning crescent moon rises shortly before sunrise and sets shortly before sunset. It is also in the sky for most of the day, but most easily visible around dawn. Gandalf61 (talk) 13:43, 26 January 2010 (UTC)

The position of the ecliptic changes depending on the time of night and the time of year, and the moon changes its devriation (distance) from the ecliptic as well. ~AH1^(TCU) 20:19, 27 January 2010 (UTC)

Red bull exhaust pipe and rust

http://thereifixedit.com/2009/11/26/red-bull-gives-you-ignition/

One of the commentators said that at least the pipe won't rust since the red bull can is made of aluminum. But would it only hasten the deterioration of the exhaust pipe by acting like a Sacrificial anode or something.

By the way I think Steve would enjoy (or get horrified by) the "fixes" given in the site.--121.54.2.188 (talk) 06:01, 26 January 2010 (UTC)

Looks like it's well away from the outlet manifold so heat (melting/softening) shouldn't be an issue. Looks like a good job actually, for temporary use. If the 'aluminum' acts as the anode it will corrode, not the steel pipe. If the pipe is mild steel the Sacrificial anode article under examples says "protection of voids in the glass lining of mild steel water heater tanks via use of magnesium or aluminum alloy anodes". Not 100% sure of this. Depends on exactly which dissimilar metals are involved 220.101.28.25 (talk) 11:08, 26 January 2010 (UTC)

Yeah, that's right. Aluminum has a much higher reduction potential than steel. So what will happen is the Aluminum will corode, and the iron will stop rusting. I have lost several good aluminum pots and pans when I made the mistake of keeping them in the same drawer as steel ones; when the steel ones started to rust, even a little bit, it caused the Aluminum pans to develop a nasty black film (aluminum oxide) which rubbed off on everything, and resisted washing off. I eventually ditched the pots, and learned to keep those materials in seperate locations. --Jayron32 13:32, 26 January 2010 (UTC)

I've seen worse "fixes". My concern with this "fix" is that the connection between the can and the pipe doesn't look gas-tight - so in all likelyhood it's leaking nasty carbon monoxide into places where it can get sucked into the cabin. The vibration that's transmitted between the bucking/shaking engine and the fixed-to-the-frame tailpipe will find the weakest point. In a very short amount of time, the can will be bent enough it won't be a tight fit and then the occupants of the car will start losing brain cells to CO poisoning (although evidence suggests that this had already happened when they were considering the fix!) Also, there is scope for the can to melt - although it's hard to predict that without knowing a lot more about the vehicle. Exhaust pipes are made from heavy gauge steel - not thin aluminium. Car manufacturers would certainly use thin aluminium if they possibly could. The fact that they don't speaks volumes about the suitability for the job! This is the kind of botch that I'd certainly consider as a "get me to the nearest garage on a dark and stormy night" fix...but no more than that.

It's the 'invisible' fixes that are most worrying. When I bought my 1963 Mini, the previous owner had started to restore it - and had not understood that the pitch of the threads on the 'whitworth' bolts that British cars used back then is not the same as the thread pitch on US cars. Hence, when he replaced a nut or a bolt, he would - with 100% reliability - strip the threads. Of the 16 lug nuts holding the wheels onto the car, 8 were stripped in this way. One wheel had three out of four stripped - not one wheel had four good lug nuts! All of the bolts on all of the shock absorbers were stripped. His efforts to add seatbelts to a car that was manufactured without them (and without hard attachment points to which to add them) were...um...creative and exciting. SteveBaker (talk) 13:48, 26 January 2010 (UTC)

Does this mean I can stop any iron thing from rusting - handtools for example - by attaching some aluminium cooking foil to them? Or wrapping them in aluminium foil? 92.24.54.79 (talk) 22:13, 26 January 2010 (UTC)

Certainly not! If it did then every car would come with a small zinc plate attached to the bodywork someplace and cars simply wouldn't rust. Since that doesn't happen - we may deduce that there has to be a catch. On the other hand, this kind of thing is done routinely in steel ships - see Sacrificial anode. What that article says is "For this mode of corrosion protection to function there must be simultaneously present an electron pathway between the anode and the metal to be protected (e.g., a wire or direct contact) and an ion pathway between the anode and the metal to be protected (e.g., water or moist soil) to form a closed circuit; thus simply bolting a piece of active metal such as zinc to a less active metal, such as mild steel, in air will not furnish any protection." - so it works for ships that are bobbing around in salty water - but not for cars that are exposed to highly non-conductive air. SteveBaker (talk) 06:19, 27 January 2010 (UTC)

Cars are exposed to rain water, humid air and any amount of electrolyte solutions of acid pollution and road salt. Zinc in the form of a layer of galvanising or primer protects steel from corrosion. Cuddlyable3 (talk) 13:40, 28 January 2010 (UTC)

is this a valid question here?

Is this desk the proper place to ask a physics question? Is there perhaps a better place where physics discussions take place, such as the argument pages there are concerning mathematics? --Neptunerover (talk) 08:46, 26 January 2010 (UTC)

General Physics goes here, but Mathematical Physics (which looks just like Maths) goes on the Maths Desk, I would say. Dbfirs 09:58, 26 January 2010 (UTC)

Okay then, my next question concerns the form of the question I want to ask, since I want to make sure I am not asking what would be an inappropriate question, no matter on which desk I ask it. I'm wishing to make a short statement that I consider valid, after which I'm hoping to be offered suggestions concerning my perceived validity of the statement, since I'm wondering if perhaps there might be things I am not taking into consideration. --Neptunerover (talk) 10:31, 26 January 2010 (UTC)

The intention of the Wikipedia Reference Desks is to respond to factual questions that can be answered by reference to Wikipedia articles, reliable sources outside of Wikipedia, or, occassionally, through the previous experience of individual editors. The reference desks are not intended to be a chatroom, a soapbox for promoting individual opinions, or a forum for debating controversial topics - see Wikipedia:Reference desk/Guidelines. Whether your question will meet these criteria or not depends upon the contents and context of your "short statement". Gandalf61 (talk) 11:16, 26 January 2010 (UTC)

Please don't keep us in suspense Neptunerover. Ask if it's suitable 220.101.28.25 (talk) 11:24, 26 January 2010 (UTC)

If you want to know if your understanding of existing physics is correct, then ask away. If you want to ask if your own theory that you have come up with might be correct, then you'll need to go somewhere else. --Tango (talk) 12:57, 26 January 2010 (UTC)

Is this desk the proper place to ask a physics question? - Yes. Physics is science and this is the science reference desk and our job here is to answer questions.

Is there perhaps a better place where physics discussions take place, - Yes there are better places to hold discussions. Discussions (as in: general chit-chat) are not encouraged here - we're here to provide answers to specific questions. Sometimes we do get derailed into discussions but that's not really supposed to happen. So there is undoubtedly a better place (outside of Wikipedia) to hold discussions (as opposed to questions).

SteveBaker (talk) 13:27, 26 January 2010 (UTC)

I wouldn't say that I'm looking for a discussion, but rather just input. It's not like I generally have very many people of intellect around me who I can bounce things off of, not that anyone here would know that. So I'll make my statement and answer anything if I am asked anything, but I'll do what I can to avoid expressing anything else. --Neptunerover (talk) 16:17, 26 January 2010 (UTC)

The direction of the force of gravity is reversible depending upon how one looks at it. While this may seem to go against everything we've ever been taught, the direction of the force of gravity is not necessarily 'down', but just as well it can be considered as a force going 'up'. Not to say that gravity would make things go up, but what is meant is that because of gravity's upward force, things go down. No matter how counter intuitive the idea may seem, this idea of gravity being based upon a constant upward acceleration is well supported by General Relativity. Is the Earth pulling us against it, or is it pushing up against us? In either case, the math is exactly the same. I think pushing upward explains the force better than a weird suction downward, considering that if the Earth is pushing against me, it makes sense that I should be held firmly against it. However, if the earth is pulling me toward it, how is that accomplished without a rope or tether of some type? Occam's Razor says that if you can explain something simply, stick with that. (Important note: How 'pushing outward' might be accomplished in 3 dimensions is not part of the subject of the preceding statement, and should not be considered when judging its validity, please.) --Neptunerover (talk) 16:17, 26 January 2010 (UTC)

For Earth to be pushing against everyone on its surface at once, it would have to been expanding outwards at a rate of 9.8 m/s, wouldn't it? Which it demonstrably isn't. And I seem to recall this conclusion being reached last time you tried to discuss this. Vimescarrot (talk) 17:33, 26 January 2010 (UTC)

In addition to the above, "pushing" fails to explain orbits. Also, let's be clear about what Occam's razor really is. It's a recommendation (and nothing more) to prefer (not "always select") the explanation with the fewest unsupportable assumptions. Leaving aside the initial caveats, "ignore the problems of three dimensions" is a pretty major unsupportable assumption. — Lomn 19:10, 26 January 2010 (UTC)

Gravity is a natural phenomenon by which objects with mass attract one another. The OP talks about Earth's gravity but it can be demonstrated that all objects have gravitational attractions to each other. Classical mechanics gives Newton's law of universal gravitation. The invisible force of attraction between two objects is a pull in the direction of the other object and therefore when one changes one's reference frame from one object to the other, the pull direction reverses. It is however the same attraction. If the OP is making the point that gravity both pulls the Earth towards Neptunerover and pulls Neptunerover towards Earth then that is correct. It is consistent with what is taught and there is no good reason to invoke General relativity, a need for a rope or to suppose another explanation would better suit Occam's Razor. Kepler's laws of planetary motion require Newton's laws to work in 3 dimensions, which they evidently do. Cuddlyable3 (talk) 19:13, 26 January 2010 (UTC)

Hmm... reconsidering this, it looks more like you're just redefining all forces to "go" in the opposite direction. I think you'll find this a far less intuitive approach when carried to its logical extremes, even if you find it sensible in the case of gravity. Pushing boxes south to make them move north? Friction in the direction of motion as a braking effect? Nope, I don't think it'll fly. — Lomn 19:16, 26 January 2010 (UTC)

Well, in the case you mention, pushing the box south cause the box itself to push north, no matter how unsuccessfully its pushing proves to be. The box may not move north, but that is the direction of its force based on its inertia or friction or whatever. --Neptunerover (talk) 06:59, 27 January 2010 (UTC)

GR tells us that gravity and acceleration are equivalent locally. That means a small object can't tell the difference between the two situations without observing distant objects. If you do observe distant objects, the difference becomes immediately apparently - acceleration is only equivalent to a uniform gravitational field, and the Earth's isn't. Objects on different parts of the Earth are accelerated in different directions (all toward the centre of the planet), that means the Earth would have to be accelerating in different directions, which isn't possible without it being ripped apart. --Tango (talk) 19:38, 26 January 2010 (UTC)

Consider a sphere with a painted stripe around the middle (like one of the striped balls here). The width of the stripe is constant, but the boundaries of the stripe curve outward, locally, at every point. If that's hard to visualize, note that the standard of straightness is a great circle and the boundaries of the stripe are not great circles. A great circle tangent to the boundary at one point would pass through the colored region and be tangent to the other boundary at the antipodal point. If you think of different cross-sections of the stripe as different times, the great circle (a geodesic) oscillates back and forth from one side of the stripe to the other, like a ball dropped through a hole in the Earth in that old thought-experiment. This is very closely analogous to what happens in general relativity. Every point on the surface of the Earth is accelerating outward, but the overall size doesn't change because of the spacetime geometry. If Earth was uniformly dense and spacetime was Euclidean then Earth's internal geometry would be exactly the geometry of the painted stripe (with two more dimensions added). It's different only because the density isn't uniform and spacetime geometry isn't quite the same as Euclidean geometry. -- BenRG (talk) 23:27, 26 January 2010 (UTC)

Well, yes, you could say the Earth is expanding in some really weird coordinate system and, technically speaking, the weird coordinate system is just as valid as the more familiar ones, but I don't think that really helps the OP. When we say "expand", without qualification, we mean expanding with respect to conventional coordinates. --Tango (talk) 23:35, 26 January 2010 (UTC)

Question (please ignore if required) Does the overwhelming amount of astronomical data evidencing the expansion of the universe itself tell us how to qualify its coordinates? --Neptunerover (talk) 04:39, 27 January 2010 (UTC)

I think Ben and Tango are talking about equivalent coordinate systems, which they are just different ways of saying the same thing, and neither one is more correct than the other. You might also be interested in Shape of the Universe, although it sounds like you might have had some exposure to this type of thing already. Buddy431 (talk) 04:55, 27 January 2010 (UTC)

Thank you. Yes, I've looked at that previously, although I will admit I'm a skimmer, so I'll go over it more thoroughly now, since it doesn't seem overly complex with density of details beyond my instant interest. My curiosity is that perhaps an artificial coordinate system is being imposed on the astronomical data in order to get a 'big bang' out of the evidence. --Neptunerover (talk) 05:09, 27 January 2010 (UTC)

"Cosmology still lacks a definitive theoretical model for inflation..."

— Alejandro Jenkins and Gilad Perez, Looking for Life in the Multiverse, Scientific American, January 2010 --Neptunerover (talk) 05:19, 27 January 2010 (UTC)

Re: artificial coordinate system: No, no coordinate system is being imposed to find evidence of the big bang. Due to the nature of expansion, there is no one direction you can point and say "the big bang happened that way". Rather, the cosmic microwave background radiation, our best direct evidence for the big bang, is observable in all directions. The big bang happened everywhere, and no coordinate system is required (or meaningful). As for the quote about inflation, it's likely that the authors are referring to the lack of why/how inflation occurred, not doubts that it did occur. — Lomn 14:03, 27 January 2010 (UTC)

Thank you. --Neptunerover (talk) 15:19, 27 January 2010 (UTC)

I think the Cosmic Background Radiation is evidence of a two dimensional universe, which could explain, or at least evidence, my weird ideas about gravity (evidence that they are weird ideas). --Neptunerover (talk) 15:37, 27 January 2010 (UTC)

On your second note, yes, the context of that quote is not in any way doubting the fact of there being inflation. I believe it is a why/how reference to the big bang model (along with various other models) not being definitive due to various deficiencies as the theory currently stands. --Neptunerover (talk) 15:29, 27 January 2010 (UTC)

Re: "deficiencies": while there is no doubt that mechanical gaps in the how/why exist, the CMB is one of the best-measured phenomena in all of science. Big bang cosmology is extremely well-attested. — Lomn 15:58, 27 January 2010 (UTC)

I think being able to measure something very well doesn't necessarily explain just what is being measured. I'm not sure anyone can more than guess (theorize) at what the CMB is from, or what it might represent. --Neptunerover (talk) 15:35, 29 January 2010 (UTC)

The origin of the CMB is understood. There's overwhelming evidence now that big bang cosmology holds back to the decoupling era (when the CMB was emitted) and much farther. Things become unclear when you get back to the inflationary epoch, but that's much, much earlier than decoupling. -- BenRG (talk) 03:26, 30 January 2010 (UTC)

I figured out a big problem I had here, in that I was equating inflation with expansion. Expansion is evidenced by the redshift, while inflation would be related to a big bang scenario only. --Neptunerover (talk) 15:03, 30 January 2010 (UTC)

Refrigeration not supported at low ambient temperature

Resolved

I've read the article on refrigerators which seems to confirm my understanding of how household fridges work. I've also searched the archive but couldn't find an answer to my query. I have a Smeg fridge (http://www.smegtech.com/site/smeg/pdf_libretti/914773907-GB.pdf) which is currently in an unheated garage. I wanted to use it for extra capacity around Xmas but, although it clearly had power (the interior light worked) there was no sign of the compressor(?) starting up. On checking the manual, I found that it is only designed to work if the ambient temperature is at least 16c. At the time it was probably about 2c. Firstly, why is that? I'd have thought that it would assist the fridge in dissipating heat if the ambient temperature is cold. Would the refrigeration cycle not work properly or could some harm come to the device? Is it likely that the device has a cut-off so that it won't 'start-up' if the temperature is too cold? --Frumpo (talk) 11:02, 26 January 2010 (UTC)

That's a normal problem. The refrigerator requires outside warm air to evaporate the liquid that's flowing through it (when it evaporates, it cools), which will return to the refrigerator, be compressed by the pump, and absorb more heat (it's a cyclical thing). If the outside air temperature gets too low, it won't efficiently evaporate the gas, which effectively halts the cycle. See Vapor-compression refrigeration. If your refrigerator cuts out at 16c outside air temperature (which will quickly become inside air temperature), you will want to be very careful about what you eat from it - there are many foods that should not be stored at such a high temperature. Falconus^{p t c} 12:44, 26 January 2010 (UTC)

If you garage is consistently around 2C over the xmas period, then you don't need a fridge - just put stuff in the garage as it is. If the garage spends a significant amount of time at temperatures between about 5C and 16C, then you have a problem - it's too warm to do without a fridge and too cold for the fridge to work. A lot of people keep extra fridges or chest freezers in their garages without problems, though, so I guess there are ones out there that can handle the low temperatures. Maybe you just need to get a different fridge. --Tango (talk) 12:55, 26 January 2010 (UTC)

Thanks for the information but I'm still rather confused. I thought the evaporation and cooling happened as a result of the decrease in pressure beyond the expansion valve. The article on vapor-compression refrigeration says that additional evaporation occurs when warm air inside the fridge is passed over the evaporator but why do we need warm air outside the fridge. Introducing heat from outside seems contrary to what we're trying to achieve.--Frumpo (talk) 10:12, 27 January 2010 (UTC)

Because we need the liquid to turn to gas in order to be compressed. If the outside temperature is too low, this will not happen efficiently and therefore the compressor may be trying to compress a gas/liquid mixture, which it is not designed for. As has been suggested, just turn the fridge off and put your food in to keep it cool. --Phil Holmes (talk) 12:05, 27 January 2010 (UTC)

OK, I understand now. The fridge is just being stored in the garage - I don't normally need to use it but couldn't figure out why there was a minimum operating temperature. Now I know. Thanks all.

←undent
(I was researching this before your last post so, here it is.)
I was speculating that perhaps this particular fridge was specifically designed to work in a country where the ambient temp. is at the higher end of 'normal' (always(?) above 16° C). And therefore not able to operate in more temperate climates. Had a look at the manual on p.4/sec. 3.1, as you said, climate class "N (Normal) from + 16° C to + 32° C" so there are models for different climates, but not down to +2°. Same page says "Never ..... install it outdoors",p.4 and p.5 "The appliance is specifically constructed for domestic use". It is not outdoors, but the manufacturers appear to have assumed that you would have it 'indoors' in a kitchen (not garage), where presumably < +16°C is unlikely. However even in warm Australia, we get below that and 'garage fridges' seem to work.

Checking the refrigerant used (R600a), according to this p.2: "The properties of R 600a differ from other refrigerants commonly used in household applications,". See Also: Refrigerant
Normal boiling point in °C
R600a @ -11.6°C ...isobutane
R134a @ -26.5°C ...1,1,1,2-Tetraflouro-ethane
R12... @ -29.8°C ...Dichloro-difluoro-methane
So it seems to boil at a significantly higher temp. than the other gases. I can see how this could raise the minimum temperature at which it can work effectively. If your fridge used R12, then its minimum should go 18°C lower This might explain why other fridges apparently have no trouble working in similar conditions. Note I am not an expert in this area. See Also Heat pump and Refrigeration for more detailed explanations of fridge operating principles.
220.101.28.25 (talk) 15:25, 27 January 2010 (UTC)

Thanks very much. I started looking at refrigerant boiling points but it's hard to know what pressures are involved in the various parts of the fridge and what the corresponding boiling points would be. However, as you say, my fridge seems to be filled with a refrigerant that's liquid at temperatures when other refrigerants would be vapour and, as noted above, that's no good for the compressor.--Frumpo (talk) 18:01, 27 January 2010 (UTC)

Welcome!. You seem to be a 'victim' of the desire to reduce the use of CFCs and similar chemicals to help save the ozone layer. Speaking of 'garage fridges' the one I'm most familiar with is an old one about 40 years old, which is undoubtedly filled with nasty CFC and works merrily in hot (40°C+) conditions, and would almost certainly get down to 16°C in winter in Sydney (but not 2°C). Be interesting to compare the specified operating range of such an 'old school' fridge to yours. Only other thing I could suggest is to look into what gas is used in places that are cold even in summer. PS. How long did you leave the fridge on when you tested it? Possible you simply didn't wait long enough? ;-)? We have Computer Engineers, Neuro-scientists, doctors, Rocket Scientists and even a seagull specialist(!) answering queries here, you'd think we would have a refridgeration technician! 220.101.28.25 (talk) 00:43, 28 January 2010 (UTC)

Hall effect EEG?

Supposing a conventional EEG was taken using head electrodes. Would a powerful magnetic field around the subjects head, oscillating in a three dimensional raster pattern, alter the "focus" of all the electrodes in such a way as to vastly increase the spacial resolution down to the level of individual brain cells?Trevor Loughlin (talk) 13:58, 26 January 2010 (UTC)

No. --BozMo talk 14:13, 26 January 2010 (UTC)

From the title I guess the OP is thinking of using Hall effect sensors as the head electrodes. Hall effect sensors cannot generate magnetic fields so the 3-D magnetic raster scan (interesting notion) would be generated by an array of electromagnets. Focussing the magnetic field would be a difficult design problem and the only use for the Hall sensors would be to measure how well it was achieved. Cuddlyable3 (talk) 14:58, 26 January 2010 (UTC)

The article on Transcranial magnetic stimulation might be helpful here. It can't be used for the proposed purpose, but it might give you an idea of what would happen if you created such strong magnetic fields. Looie496 (talk) 16:52, 26 January 2010 (UTC)

I was thinking of normal electrodes, not Hall Effect sensors.The Hall Effect would take place in the brain material itself due to the altering magnetic field (I hope) slightly changing the brain areas all the EEG electrodes pick up electrical signals from, increasing resolution.Trevor Loughlin (talk) 06:26, 27 January 2010 (UTC)

Psychological reason for former students talking about how strict/tough teachers were

I was under the impression, and the article on memory seems to agree, that we remember mostly the good things. Obviously, people remember some negatives. Still, on a few alumni Facebook pages for American Junior High Schools, I notice former students, now in their 30s and 40s, talking more than usual (maybe 30-35% of posts) about teachers' discipline and how strict they were in 6-9th grade. My question is, why? Why are they choosing to discuss this when reminiscing?

I'm theorizing maybe it's how bad the students were; maybe not all the posters, but perhaps they're remembering some really rough kids but can't recall specifics on that - but they can recall teachers and how they handled it. While the ones I'm reading are from a city of 100,000 - not exactly a crime-riddled urban area - I'm sure the neighborhood plays a part.

It just seems strange that so much time is focused on negative thing, instead of different assignments, social activities, and so on; which are mentioned, but not as much. It especially seems strange because of the notion that "what's too painful to remember, we simpy choose to forget." (Okay, the line is fromt he song "The Way We Were," but you know what I mean.)209.244.187.155 (talk) 14:40, 26 January 2010 (UTC)

I don't know that there's a psychological reason for it, but I can give you a social one - happy stories are boring. Nobody wants to hear "Oh man my teacher was soo much better than yours" for very long, but everybody wants to swap/compare horror stories. Every tell a story about getting injured? A group of friends can go back and forth telling different, painful stories for an hour. Same thing - it's rude and annoying to try and compete for "best" but if you're competing for "worst" the only person who loses is you. School-age people also do it with sleep - "I only slept five hours last night." "Yeah well I got 3.5!" "Lame, I pulled an all-nighter." Someone saying "Damn, I slept 9 hours last night I feel great" is no fun. ~ Amory (u • t • c) 14:47, 26 January 2010 (UTC)

Presumably because their teachers were strict. And at that critical age, the conduct of adult figures in your life can have a profound influence on your psyche for a very long time. So I guess it's just 'digging in the dirt' as Peter Gabriel puts it. Vranak (talk)

Perhaps they have children in school now and they are witnessing the dumbing-down of the school system. I see it at a college level. I have students who invariably made straight A's. They almost all took advanced courses. They scored very high on the SAT. Then, when I show them long division (to explain what modulo means), they say that they've never seen it. That is just one example. It also shows in the fact that the exams for the class have not changed in the last 10 years, but the scores on the exam go down every year. They used to be above 90% for most students. Last semester, the average was around 65%. It is clear from my perspective that there is a dumbing-down in the school system. I don't blame the students. They are not genetically dumber. I could blame less-than-strict teachers, but I don't. I blame the parents who feel it necessary to give A's to students without requiring them to earn the grade. -- kainaw™ 14:57, 26 January 2010 (UTC)

To be fair, long division is a skill that's fading fast. I'm trying to recall the last time I had to do it - and I'm pretty sure it was over a decade ago - and I'm someone who does a LOT of math and arithmetic. It's worth teaching it for lots of reasons - but expecting everyone to know it well is asking a lot for what is essentially an unneeded skill. We don't teach kids to use slide-rules either. SteveBaker (talk) 15:11, 26 January 2010 (UTC)

It's very hard to compare student ability in 2010 to student ability in 1965. A child nowadays is a computer expert - in 1965, if they'd heard of computers, you'd be lucky! Sure, they waste some of that technical expertise on video games (Sorry Steve), various online garbage, but they also know how to type, how to use a word processor, how to query the internet for information. Their skills toward those goals are greatly enriched over those of a student in 1965, who consequently had more mental acuity to focus on "pure" subjects. So, while there aren't all that many 9th grade hackers (despite what you see in the mass media), there is an enormous repository of cultural and institutional knowledge about computers which doesn't get graded. Technological expertise is only one example of a huge class of useful skills which are never graded. When you cite lower total scores on tests, without accounting for the redirection of intellectual activity to other, un-tested subjects, you're failing to account for this sort of skill-set displacement. In other words, our kids aren't stupider, they're just focused elsewhere.

I sincerely hope that this does not mean focus is lost on core subjects I consider critical - basic math and literacy, for example. But to some extent, this defocusing is not a total loss. I grew up wasting a ton of my time on video games - and I learned a ton about graphics acceleration, programming design, and computer architecture by proxy. I was never tested on those concepts in a math class, or even in a programming class. Yet, now, when I encounter older programmers, traditionally trained in more conventional ways, who could probably best me in a long-division competition, they're often unable to discuss the merits of PCI-X vs. PCIe - or even comprehend this entire way of thinking about program design. But, that skill is very relevant in today's computer engineering job market - a lot more so than many concepts that I was formally tested on during schooling. I imagine the same argument can be made for a variety of other extra-educational knowledge that is acquired.

So, while it may be accurate to say that the scores lower on the same tests as they are given year by year, this line of reasoning suffers from a fundamental flaw. If the test does not change from year to year, it implicitly assumes that the same material is relevant from year to year - that performance of the same skills of the previous generation is a merit. In some sense, that encourages stagnation and repetition - if our kids do the same thing we do, but only incrementally better, then what progress has been made? As much as it's a tear against a dumber or less-motivated populace, it's equally an indictment of an education system that does not know how to adaptively adjust its testing to normalize for relevance and currency.

This is a very hard problem - we aren't going to just throw formal education out the window (well, we could, and many prominent philosophers such as Ivan Illich suggested that we should). But there has got to be a happy medium - an education system which adjusts to current needs, accepts that society isn't going to collapse just because long division, aether theory, and FORTRAN 77 are dying arts, and trains kids for what they need to know today. Nimur (talk) 15:33, 26 January 2010 (UTC)

Tossing out long division is acceptable, but having students perform worse every year at college level is not acceptable. Instead of improving education, we do things like "recenter" the SAT to make the less-educated students feel better. There is no genetic reason for modern students to perform worse on the SAT. They should perform better than those students in the 50's and 60's who didn't have computers and the Internet to fill them with valuable information. The fact that they don't implies that something is broken. Some blame the less strict teachers who just shove the students from one class to the next. I already stated that I blame the parents. -- kainaw™ 15:55, 26 January 2010 (UTC)

I also want to point out that this question is about why 30-40 year olds state that their teachers were stricter. It is not about how smart students are. My answer to the question leads to the debate about how smart current students are, but that is not the topic here. Further, this is not a forum for debate. So, please feel free to disagree with me and tell the person next to you what an idiot I am, but don't make my answer a means of hijacking the thread to debate modern vs past students. -- kainaw™ 16:04, 26 January 2010 (UTC)

Sorry, I am probably guilty of WP:SOAPBOX, in at least a few recent posts. I will try to curtail this tendency. Nimur (talk) 08:15, 27 January 2010 (UTC)

The point I think some people are trying to make is that "recentering" the SAT is not, in itself, a bad thing at all. A hypothetical SAT from a century ago would have little meaning to us now (Latin conjugation, what the hell?), so it shouldn't be surprising at all that it would constantly be in need of shifting. Modern primary school math places a heavy emphasis on learning how to approximate answers and very little on obtaining the results. To people of my age that seems like a dumb thing to do, but it's simply an acknowledgement that precise mathematics is not used by most people and that calculators can perform any function flawlessly. Approximating that 21/5 is "about 4" is much more useful to most people than doing the long division. If SATs don't keep step with what's being taught, the grades will shift downward. Matt Deres (talk) 17:44, 26 January 2010 (UTC)

The most basic principle of storytelling is that every good story involves a conflict and a resolution. Without a conflict there is no story. Nice teachers don't tend to generate strong conflicts, so they don't tend to generate good stories. Looie496 (talk) 16:47, 26 January 2010 (UTC)

Thakns for the answers; I hadn't looked at it from the storytelling/one-upping angle, but yes, that's very likely. Also, considering that a couple of them talked about sneaking out to smoke then, while I don't like to pass judgment on how they acted, maybe some of it is reliving the thrill of trying to away with stuff, too; even if they did get caught at times. I imagine that for some, there is a point to reminiscing about the thrill of trying to get away with stuff, whereas that thrill isn't there anymore now; as adults, they have the freedom, and any stuff they would have to "get away with" would lead ti the threat of jail or large fines if caught; they've matured enough to realize that's not worth the risk.209.244.187.155 (talk) 19:05, 26 January 2010 (UTC)

Improving Loudspeakers

                            LS1              LS2
             |¯¯¯|  |\        /|            |\
frequency____| ? |__| \___|¯|/ |   Room     | \|¯|__
   sweep   | |   |  | /   |_|\ |            | /|_| |  |\
           | |___|  |/        \|            |/     |__|-\
           |                                          |  \___test
           |__________________________________________|+ /   output
                                                      | /
                                                      |/

I have a stereo audio system and want to improve the sound in my listening room. I think it is possible to compensate for the non-linear frequency responses of my loudspeakers and room acoustics by adding a filter at the preamplifier stages of both channels. I have a graphic equalizer but I hope to get a better result than from adjusting it by ear. If I could measure the exact correction needed then I could optimise the equalizer settings or possibly build a better filter. I propose to measure the audio performance as shown in the diagram where:

"?" is the equalizer or filter to be designed

LS1 is one loudspeaker that is driven with a swept frequency test signal

LS2 is an identical loudspeaker operating as a microphone.

I assume that the loudspeakers' frequency responses are the same whether they are driven at low level or used as a microphone. I intend to adjust the stage "?" to minimise the test output at all frequencies. That should compensate for the room acoustics. But can you suggest how to handle the following snag with my plan: the optimised stage "?" will introduce twice as much compensation as is needed for the non-linearity of a loudspeaker. How do I design a compensator for one loudspeaker? Cuddlyable3 (talk) 14:46, 26 January 2010 (UTC)

Back in the early 1980's Philips used to make "Motional feedback speakers" that did more or less exactly this - so what you're trying to do is certainly possible...and with 1980's technology too! However, you'll need to allow for the time delay in the audio getting from LS1 to LS2 - sound travels V-E-R-Y--S-L-O-W-L-Y compared to electricity! You're definitely going to need either some phase compensation or a programmable delay between the input on the left and the comparator on the right. You might also look at Powered_speakers#Servo-driven_speakers - where you use an accelerometer to directly measure the motion of the speaker cone in order that you may compensate for it's frequency response - although (obviously) that doesn't take account of the room acoustics. SteveBaker (talk) 15:06, 26 January 2010 (UTC)

Nitpick, Steve - sound travels slowly compared to the electromagnetic signal in the other wire. Nimur (talk) 15:10, 26 January 2010 (UTC)

What does it mean when SteveBaker writes "for it is frequency response" ?

We do (of course!) have an article about Motional Feedback speakers - but it's not exactly helpful! SteveBaker (talk) 15:45, 26 January 2010 (UTC)

Motional feedback is interesting, expensive, has only been applied to low-frequency (woofer) speakers and it is not what I propose. The block "?" will provide forward correction and not introduce feedback. I shall disregard phase, sound delay LS1 to LS2 and longer delays in the room acoustics by making the test comparator compare powers of the two signals and the frequency sweep will be slow. The ear is relatively insensitive to constant phase error so phase changes that "?" introduce will probably not be noticed. In any case a phase linearising stage can be added to "?" if that is found necessary.
Where is the snag is with the following procedure? 1) Adjust "?" until test output is constant (or zero with gain adjustment) for all frequencies. 2) Build two compensator circuits that each implement half the distortion of "?" and attach them to the two channels. 3) Now I have a system where speaker non-linear frequency responses are fully compensated but room acoustics are half compensated. 4) Run the measurement again (one of the compensators is in the "microphone" channel). Only the remaining uncompensated room acoustics need to be corrected and that can be done by adding the second "?" in full to both channels.That sounds unclear but at least Nimur I understand what SteveBaker means by electricity.Cuddlyable3 (talk) 17:02, 26 January 2010 (UTC)

Tyre pressure

If you inflate a car's tyres to a certain pressure and then add weight to the car, does the pressure in the tyres increase, or does the pressure remain the same because the tyre has retained the same volume, albeit that it has deformed slightly? I imagine that if the tyre were to be equally compressed on all surfaces (say by taking it underwater) then the internal pressure would increase, but I am not clear if compression on one part of the surface would be compensated by the expansion on other parts of the surface leading to static volume and pressure. Any help appreciated. AChangeOfPressure (talk) 15:02, 26 January 2010 (UTC)

Pressure depends on the force and area ,force is mass * acceleration so if the Mass is increased the pressure increases .If by compression you mean applying force then the pressure increases--NotedGrant Talk 16:08, 26 January 2010 (UTC)

Not sure if I was sufficiently clear in my original question, so let me clarify. Imagine an example where I inflate the four tyres of a car to a pressure of 30 PSI, then I add a significant amount of weight to the car (in terms of passengers, luggage etc) equally distributed across the four tyes and then take a new reading of the internal pressure of the tyres with a pressure gauge. Will they have increased above 30 PSI? Thanks AChangeOfPressure (talk) —Preceding undated comment added 16:19, 26 January 2010 (UTC).

There are two effects happening at the same time. Increased load will deform the tyres; if this reduces their volume then pressure in the tires will increase. But at the same time the size of the contact patch is increased, so the load is supported over a greater area. So if you add a load that is 10% of the weight of the car, the tire pressure will not necessarily increase by 10% - it may only increase by 5%, while the area of each contact patch also increases by 5% (yes, I know there is a simplification there). I don't know the relative sizes of the two effects in practice - it probably depends on all sorts of factors such as the size and design of the tyres. Gandalf61 (talk) 17:07, 26 January 2010 (UTC)

For the vast majority of tires, the load is carried almost exclusively by the increased contact patch area. It takes a great deal of deformation to increase the pressure even slightly (a quick mental calculation says that flattening the typical tire so that the rim is in contact with the ground will increase the pressure by 10%). --Carnildo (talk) 00:50, 27 January 2010 (UTC)

As weight is added to the car the tyre pressure increases. As weight is added to the car the tyre deforms so that the internal volume of the tyre decreases. The reduced volume causes an increased pressure. The area of the contact patch also increases in size. Dolphin51 (talk) 06:42, 27 January 2010 (UTC)

Yes, that sounds correct, but I think that the percentage difference in the air pressure inside the tyre will be minimal because tyres are designed to make the change in volume with extra weight as small as possible. A change in temperature makes a much bigger difference to the tyre pressure. The pressure of the tyre on the road surface is a separate argument (only slightly linked to the air pressure in the tyre because of deformation). This is only a wild guess, but, within the design limits of the tyre, doubling the weight supported probably increases the tyre pressure by 1 or 2%, but almost doubles the contact pressure with the road. Can anyone find any test data? Dbfirs 07:21, 27 January 2010 (UTC)

Human Underwater Speed Record

What is the world record for speed acheived by a human underwater? I mean unassisted though I suppose they could be in some sort of human powered sumarine, wetsuit with fins, etc. TheFutureAwaits (talk) 16:44, 26 January 2010 (UTC)

That might depend upon a lot of things, such as water salinity and turbulence, etc. --Neptunerover (talk) 13:24, 27 January 2010 (UTC)

The closest thing I've seen is the 50m freestyle, where the world record is presently 2.4 m/s. I'd guess that this provides a reasonable balance of advantage from push-off with disadvantage from mandatory surfacing. It'll be hard to find anything else that's certified, but this guy's human-powered sub claims about 3.6 m/s. You might also consider the entries in our article on human-powered watercraft. — Lomn 19:32, 27 January 2010 (UTC)

Evolution

What proof is there for evolution? How do I know it isn't just an atheist hoax? --J4\/4 <talk> 16:54, 26 January 2010 (UTC)

First, read the article on evolution. It will detail some of the arguments that have been made. This is the subject of a huge amount of scientific and popular literature and it would be impossible for us to provide all the information here. If you have a specific question regarding evolution, please re-phrase your question. --- Medical geneticist (talk) 16:59, 26 January 2010 (UTC)

Do I look like I would hoax you? File:Ape shaking head.gif

Cuddlyable3 (talk) 17:27, 26 January 2010 (UTC)

Also, I think it's been done. Vimescarrot (talk) 18:01, 26 January 2010 (UTC)

The largest organized Christian denomination in the world has stated there is no conflict between any part of the scientific theory of evolution and christian faith. Many Christians of many other demoninations also see no conflict, nor do many members of other faiths. Many scientists are also devoutly religious, and have no problem with the fact that evolution is happening, and also having a devout faith. The conflict is a false one, perpetuated by people who need there to be a conflict for their own selfish reasons. --Jayron32 21:33, 26 January 2010 (UTC)

One thing I would like to add is that your primary premise is very flawed. Not all people who believe in evolution are atheists, not by a long shot, even Darwin wasn't strictly an "atheist", he didn't believe in a personal God. In fact, Catholics who don't believe in evolution are a minority, even in the US 58% of Catholics answered a poll that they believe evolution to be the best explanation of the origin of human life on earth. An even larger percentage of Jews, Hindus and Buddhists believe in evolution and even as much as 45% of Muslims in the US. We even have an article about it: Theistic evolution. Vespine (talk) 22:14, 26 January 2010 (UTC)

I assume you must be talking about the OP. I have never, here or anywhere, made the claim that there is any connection between the theory of evolution and athiesm. Quite the contrary, if you read my comments, I make the exact opposite arguement. Could you clarify the antecedant of your pronoun, por favor? --Jayron32 22:28, 26 January 2010 (UTC)

There is no strict "proof" in science, only theories and evidence. The evidence for evolution, however, is overwhelming. The Origin of Species lays down the basic case so convincingly that it has nearly immediately been widely accepted - despite the fact that at the time no hereditary mechanism supporting evolution was known, we had few fossils, and no genetic evidence. Indeed, Darwin comes as close to a proof as science can come - geometric increase of populations, finite carrying capacity of habitats, and variability of heritable traits more or less implies evolution mathematically. The suggestion that it is a atheist hoax is entirely unsupported. Many of the past and current researchers supporting evolution are religious people. Many large Churches have accepted evolution. And any conspiracy would need to be so gigantic as to be impossible to keep secret. --Stephan Schulz (talk) 22:23, 26 January 2010 (UTC)

Proof is everywhere. The evolution of bacteria in hospitals in response to our best efforts to nuke them with antibiotics. Rats that are resistant to rat poison. Rabbits that survive mixamatosis. Lactose (in)tolerance in humans. My current favorite is the Recurrent laryngeal nerve in giraffes. Rows and rows of fossils in just about any decent natural history museum. However, here is a good one:

There is a species of moth in the UK that are normally white - this is because they live on trees with very light colored trunks and it helps them be camoflaged from hungry birds, very rarely, a mutant dark colored moth (of the same species) would show up. When the industrial revolution hit the UK, and everything was run from coal, there was a vast amount of dirty soot in the air and the places where these moths came to rest became blackened. Within a very small number of years, butterfly collectors noticed that the rare dark variety were becoming much more common and the 'normal' light colored ones were becoming harder and harder to find. The moths had evolved an adaptation to all of that sooty pollution. Moreover - when the "Clean Air Act" was passed in the UK and the clouds of filthy carbon-laden emissions more or less ceased, the process reversed itself and the dark colored moths started to vanish with the light colored ones again becoming the most common. Again, the moths had evolved.

I could sit here and type in convincing examples all day - but I'll restrict myself to just one - and recommend that you read almost anything by Richard Dawkins who is truly excellent at providing convincing examples that the "intelligent design" loonies can't possibly counter (which is why they hate him with such a passion - and why our OP will probably never read a book by him).

SteveBaker (talk) 22:40, 26 January 2010 (UTC)

SteveBaker is referring to Peppered moth evolution, which is a long article that goes into a great deal of detail to creationist alternative explanations, and the political controversy. Comet Tuttle (talk) 23:45, 26 January 2010 (UTC)

The biggest rationally formulated complaint of the intelligent-design/creationists about the Peppered Moth story is that it only represents "microevolution". Where is the fish turning into a rabbit? Where is the long-eared furry fish? But evolutionists don't claim that a fish turned into a rabbit. Fishes turned into slightly different fishes which turned into slightly more different fishes - and so on, "microevolution" by microevolution until one day, you look at the millionth generation of microevolutionary change and...guess what? It's a rabbit! So those who seek a macroevolutionary proof won't find one. Even evolutionists don't claim that - evolution cannot work in big steps, it requires a vast expanse of time for any kind of large change. When pressed on this point, the less rabid creationists will say that there is not one case in documented biology of one species changing into another by an intermediate step. That's also true - but it's another misconception. (I'm going to use the word 'species' loosely to mean "different group of animals") If biologists find two animals that are significantly different, they give them different names. Even if it's just a teeny-tiny microevolutionary step from one to the other...they have different names so it's easier to talk about them. If we find another animal that's a clear intermediary and is different from both its ancestral and descendent species in any measurable way - it gets a different name. Hence you'll never find a clearly intermediate in a biology textbook simply because of the way biologists name things. So this lack of an intermediary isn't a failure of evolutionary theory - it's just a consequence of the way biologists carry out their craft. So the example of the peppered moth is indeed a tiny step - but a tiny step is all we need to establish the theory of evolution as fact.

There are just three things we need to demonstrate:

1. That mutations sometimes happen. We see this all the time in the more dramatic 'freaks of nature' - but also that not all humans are identical. "Tallness runs in my family" is occasionally confounded by a short offspring.
2. That 'survival of the fittest' actually works - which we see so clearly in the peppered moth story. When the trees are light colored, light colored moths thrive and black colored moths are hard to find. When the trees change color - the moths that have the best camoflage survive.
3. That lifeforms inherit significant characteristics from their parents. We all see in daily life, my kid has my eyes and my wife's nose. Photos of me when I was 10 years old are hard to tell apart from photos of my kid at the same age. The offspring of two black labradors is a black labrador.

If all three things are true - then it's very hard to see how evolution couldn't happen. (1) A random mutation makes a change (a black moth in a population of white moths for example). (2) If the change is an improvement (because we have dark trees these days) - then more of the mutants will survive and (3) their offspring will inherit their gene for dark coloration. That's it. That's all it takes to get from a bacterium to a human given a few hundred million generations. SteveBaker (talk) 02:40, 27 January 2010 (UTC)

If you look at the sort of people who have done work on how evolution actually works—e.g. Ernst Mayr, E.O. Wilson, Stephen J. Gould, Charles Darwin, and so on—rather than the real evolution evangelicals (e.g. Richard Dawkins), what you see is a body of people who have spent an immense amount of time looking at very small pieces of the world (birds, ants, snails, barnacles), compiling lots and lots and lots of mind-numbing data that seems to indicate, in quite a detailed way, exactly how evolution appears to have worked. They disagree with one another on many points—they are not in strict collusion. But it seems like an awful lot of effort to go through for just a hoax. These are people who have devoted their lives to very tedious and basically obscure details that shed light on a bigger whole. This is not, generally speaking, how hoaxsters operate. Whatever they are doing, it is not a hoax. They could certainly be wrong, or could interpret evidence incorrectly, and so on. But their sincerity in the effort is fairly evident in the work itself. They are not trying to pull a fast one—they are pulling a rather slow one, if anything.

If you'd like to know about evolution, read one of the books by any of the aforementioned scientists. Go ahead, it won't hurt. Make up your own mind as to whether they are serious about it. They are subtle thinkers and not one of them is trying to proclaim atheism upon the world.

Dawkins is not so subtle, though he is clever. But he definitely does believe that evolution leads to atheism. Plenty of scientists disagree with him on this point, though. In the end, whether evolution and religion are ultimately compatible is a philosophical/metaphysical question, not a scientific one. Evolution is not compatible with a very literal and narrow reading of the Bible—neither is modern medicine, or really any basic scientific outlook. Whether you see that as a reason to reject science—despite all of its apparent mastery over nature (your computer that you are reading this on right now would not work if quantum mechanics wasn't basically correct)—or whether you see that as an imperative to read the Bible in a more interpretive way, is obviously a personal decision. --Mr.98 (talk) 23:37, 26 January 2010 (UTC)

Sorry Jayron yes I was talking to the OP. In regards to the above point made by Mr.98, maybe it has been a while but Dawkins has certinally very much done "real work" on evolution. The Selfish Gene is highly regarded as an important work in the field. Vespine (talk) 00:57, 27 January 2010 (UTC)

It's true that Dawkins doesn't get out in the field or in the lab anymore. What he does is important though. He collects information from the real scientists out in the field and puts together the disparate stories into a coherent and populist whole. There is no way I'm going to wade through a bazillion issues of some obscure journal looking for interesting and convincing examples of evolution in action. In one of Dawkins' books, I can find the story of the pepper moth - and the ridiculous way one of our laryngial nerve is connected up and the complete craziness of the way the giraffe has gotten stuck with such an incredibly unintelligent design! So Dawkins deserves a place on the bookshelf as a collector of stories. (He's also a Wikipedian...he gets bonus points for that!) SteveBaker (talk) 02:53, 27 January 2010 (UTC)

Evolution precludes original sin and its variants. It precludes the selection of Homo sapiens by a god. To say that it and religion should co-exist is incorrect, I think. 66.65.139.33 (talk) 01:42, 27 January 2010 (UTC)

There are plenty of religious people who are happy to accept it. There are few atheists who don't. The thing that makes intelligent, open minded people doubt this entire description is that there are two gigantic holes in the scientific account of the universe: What caused the Big Bang? and Where did the first life-form come from? These are questions that science doesn't have good answers for - and it's going to be exceedingly tough to find and prove them. So there is the room for your god or gods. God pushed the big red "GO" button to start the universe running - then (s)he stepped back until the earth appeared with it's nice warm oceans and appropriate chemistry and God pushed the large green "LET THERE BE LIFE" button to cause the first self-replicating molecule to appear, then (s)he steps back and lets evolution produce people. I don't personally believe that story - but it's pretty much the only one that allows religion to co-exist with science. Sadly, this is a "God of the gaps" argument - and it's only a matter of time until one or other of those two gaps gets plugged and this kind of rational religion is left clinging by a fingernail. Will people jump ship to the atheist side of the fence or will the be forced to dump their rational instincts and wind up with the loonies? SteveBaker (talk) 02:40, 27 January 2010 (UTC)

It's not necessary that god/s had any direct bearing on the 'creation' of the first self-replicating molecules. There's no reason why a religious person can't believe that god/s started the big bang, fully aware of the eventual outcome including the evolution of humans. It's surely fully within the realm of a fully omnipotent god/s.

Evolution does contradict any human creation stories as well as any literal acceptance of the garden of Eden and original sin. However a number of Christians regard much of the bible as allegory [1] and I would say accepting the bible as the entire literal truth raises a lot of issues outside of evolution. Ditto with similar religious concepts.

On the issue of Homo sapiens being chosen, that's not really precluded by evolution. Evolution says humans are just one possible evolutionary outcome and should not be thought of as some sort of goal or ideal outcome. In other words, in a biological evolutionary sense, it's nonsense to think of humans as chosen and god/s had no influence on the development of life forms on earth including humans. However this doesn't preclude god/s selecting that outcome as special, which he/she may have fully know was going to happen. (The question of 'why humans' raises some interesting issues but it's easy to see a number of possible answers.) Note also the idea of god/s having a direct influence in the world is something quite a number of scientists disagree with however it's not something that evolution itself in some way precludes. (Of course doing science generally means automatically discarding such a suggestion when considering anything you want to study scientifically.) It clearly doesn't preclude god/s becoming involved in human society after they evolved, even sending his son (however you think that happened) who sacrified himself for humans.

In terms of 66's point, his/her view of religion is a little simplistic. Not all things often thought of as religions have an original sin, the selection of Homo sapiens by god/s, or even a concept of god/s itself. Of course without any concept of God, you could define a religion as atheist, and that argument is commonly made for Buddhism but on the other hand a number of the spiritual ideas of Buddhism are clearly anathema to many Western atheists, particularly strong atheists.

As a final consideration, it's probably true that many religious people who accept evolution (particularly of the Abrahamic religions) don't do it completely, e.g. they may like to think god/s had some influence in the evolution of humans or even that humans didn't evolve but as I've been emphasising this clearly isn't essential for accepting religion.

Some links that may be of general interest [2] [3] [4]

Nil Einne (talk) 05:44, 27 January 2010 (UTC)

In my experience, a small number of theists ridicule the writings on natural selection by Darwin and others, saying The theory of evolution is nothing but a theory! Now that Darwin's writings on natural selection have been vindicated by vast amounts of new material from a large number of independent sources, Darwin's thesis can legitimately be called the Law of Natural Selection.

Scientific skeptics and others who aspire to be rational thinkers know that proofs are rare. It is only in man-made sciences like mathematics that proofs can be constructed. In nature, nothing comes with a proof. One could easily say What proof is there that God exists? (I think I know my own name but there is nothing that I would accept as absolute proof of my name - I haven't actually sighted my original birth documentation; my parents could have made errors in the documents; or my spelling or pronunciation of my name could be in error.)

So there will never be a proof that evolution, or Darwin's Law of Natural Selection, is correct. Scientists are happy to live with this situation. It appears to be theists with alternative motives who demand What PROOF is there of evolution?

Is natural selection an atheist hoax? There are many so-called conspiracy theories. Our personal world-view immediately tells us which theories we want to accept and which we want to dismiss as conspiracy theories. It is a legitimate field of enquiry. One aspect which appeals to me is that if a theory requires a very large number of people to know the truth, and a very large number to be ignorant, but the first group to keep it secret from the second group, it is worthy of being dismissed as nothing more than a conspiracy theory. For example, if natural selection is an atheist hoax it requires that a very large number of atheists know that natural selection is nothing but a hoax, but none of those atheists leaks that knowledge to a believer. My experience of small groups of people is that they are hopeless at keeping secrets. If natural selection were nothing more than an atheist hoax the believers would have uncovered the secret over a century ago. The reverse is true - every year brings new knowledge that corroborates the Law of Natural Selection. The religious world of believers continues to be divided. The various major religions of the world agree on almost nothing. Even the multitude of religious denominations choose to remain divided by maintaining a variety of churches, synagogues, mosques etc in every city. There are many who believe in a God but almost none of them show much interest in achieving unity or finding agreement. Dolphin51 (talk) 07:13, 27 January 2010 (UTC)

I found this talk by Francis Collins' (leader of the Human Genome Project and outspoken evangelical Christian) to give an interesting insight into the mind of a religious scientist. He speaks of the overwhelming evidence for evolution at about 0:44:00 and evidence against both young earth creationism and "intelligent design" at about 1:00:00. He warns against worship of the "God of the gaps", as such worshipers are setting themselves up for a fall when science catches up. 124.157.247.221 (talk) 07:49, 27 January 2010 (UTC)

Happy Brains à gogo, TMS Experiment

A Boscovich/Nikola_Tesla type Electromagnetic Household Theory. I'd like to prove similarties to the Apple IPOD users with an unawared type of Transcranial_magnetic_stimulation. Lets say some magnetic chemically bonded minerals of sorts is in the American foodstuffs and/or water supply. And the magnetic field of the two Ipod Headphones (if you just hold the two white factory Apple Ipod earpieces together, they stick magnetically) creates similar effects to TMS. As well as Cellphones and Bluetooth tech users. My experiment in this would be, and here's the question in regards, to buy a used Etch-a-Sketch, break open, and put in a Fishbowl full of water. With this magnetic dust, if my Theory is correct, would the Etch-a-Sketch dust form a visible magnetic field in the bowl if I held the two Ipod earpieces at opposite ends? --i am the kwisatz haderach (talk) 17:18, 26 January 2010 (UTC)

What makes you think that an Etch A Sketch is filled with "magnetic dust"? --LarryMac | Talk 17:22, 26 January 2010 (UTC)

Pretend he said Magna Doodle instead of Etch A Sketch. (And that just about exhausts my ability to make sense of the question.) -- Coneslayer (talk) 17:24, 26 January 2010 (UTC)

I don't know, I discriminated it by its gray color. Maybe one of those Magnetic Moustach Pen/Dust toys. So usage of Finely grounded visible Magnetic Particles. --i am the kwisatz haderach (talk) 17:27, 26 January 2010 (UTC)

TMS requires an incredibly powerful magnet. The magnetic fields created by an IPOD or any other household device are orders of magnitude too small to matter. Looie496 (talk) 17:44, 26 January 2010 (UTC)

I should add, the reason I brought this up is when I drink Coffee from the Starbucks, at my workstation, I have really good Radio reception. But if I don't drink of the corporate cup, my desk radio has a lot of static. I then concluded that I'm a radiowave receptor, and when I'm full of the metalic minerals, I get good music. --i am the kwisatz haderach (talk) 17:46, 26 January 2010 (UTC)

We are all radiowave receptors. Some people can hear long-wave amplitude modulated radio transmissions in their fillings! Are you writing a Science Fiction (or fantasy) story? Dbfirs 18:43, 26 January 2010 (UTC)

Is it possible that you only go to Starbucks on days when it is not raining? APL (talk) 20:20, 26 January 2010 (UTC)

I am reading a bunch of sci-fi actually. And I watch Noir-films. I also want to add, that I'm not trying to equal the effects of TMS, so the exact radiofrequencies of those magno tests--i'm not trying to match. I'm just questioning the possiblities of a weak electro spectrum. Something that ties in with microwaves from electric power lines over the streets, or plasma/lcd screens in homes. And I wanted to test this theory, with a fine Ferrofluid powder--these things don't need extremely powerful magnets. I want to create a new term calling these things in our drink MAGNO-MINERALS. --i am the kwisatz haderach (talk) 18:57, 26 January 2010 (UTC)

Here's an example of exactly what I'm talking about for Film Noir, Notorious_(1946_film), Under Plot, in the middle of the 3rd Paragraph: 'The poison is initially mixed into Alicia's coffee'. This film was right after WWII, there's an aura of wrongness that they don't really go into, but as I remember, in this Hitchcock film, Cary Grants character sneaks into the cellar, accidentally breaks open this bottle of wine, but instead of wine, all this metalic dust a comes crashing out. DUN-DUN-DUUUN!!! --i am the kwisatz haderach (talk) 21:39, 27 January 2010 (UTC)

I would encourage you to pause, and first execute a controlled, double-blind experiment on your fundamental premise that drinking from the corporate cup is the exact factor that is altering your radio reception. The assertion seems silly on its face. Comet Tuttle (talk) 19:42, 26 January 2010 (UTC)

Can anyone answer his original question? Would the small magnets in a set of earbuds create enough of a field to be seen with iron filings? I suspect that they would, at least for filings near the earbud, but the best way to find out's just to try it. And I think the whole fishbowl/Magnadoodle thing is a bit more complicated than you need. Just buy some iron filings, sprinkle them on paper, and stick the earbuds underneath the paper, about 8 inches apart from each other. Buddy431 (talk) 21:09, 26 January 2010 (UTC)

This Youtube video is a good tutorial on making a magnetic field viewer that is probably more sensative than just sprinkling iron on a piece of paper. I doubt that actual ferrofluid would react at all to ear buds, and besides it is expensive and messy. APL (talk) 22:40, 26 January 2010 (UTC)

Thanks for this video link, THIS IS IT. This is the test style I'd like to do in regards to our drinking supply provided by the Conglomerate Corporatesque Controls that be. --i am the kwisatz haderach (talk) 21:39, 27 January 2010 (UTC)

TMS is not a subtle thing. It feels like someone knocking on your head. (At least, it was when I had it done to me, about five years ago.) Just pointing that out. I find it very unlikely that your choice of coffee has anything to do with your radio reception. That sounds a wee bit crazy to me. --Mr.98 (talk) 23:19, 26 January 2010 (UTC)

Ok, lets say TMS in movie talk, is the equivalent of Dr. Evil, and what I'm talking about here is Mini-Me. In regards to the coffee/radio connection sounding crazy, I agree with it sounding a wee bit crazy. But I'm not here to talk of entertainment or sanity, I'm here to talk of science, and the sciences of the unseen, aka Magnetism. At that, and in regards my observations, its like this. I go to work, M-F, like clockwork, I have my radio station tuned to 89.9 KCRW here in Sun Valley, CA, close to the Burbank Airport, I believe they block out some radio frequencies somehow for air traffic control reasons, so at that the reception isn't all that great. I drink a cup of joe a day. Sometimes I get a little tense, and I think, hmmm, maybe I should not drink me my caffiene, and so I just stop drinking coffee for a few weeks. Now, because I don't change the station, I don't move the dial on the radio at all, and in my zen seeking non-coffee drinking, I like music sometimes, but then I get all this static, and in the enjoying of music, static, not good. Most of us remember the rabbit ears on the TV's, and when we hold the two ends, to find the good reception, we get clarity on the screen, and then we let go, and the static comes back, so yes, we all know we are all radio receptors, and some of us are acute enough in this to actually hear some frequencies at times. It would be a bit diabolical if there were these electronic magnetic activator machines underneath the barista that added extra magnetic juice to the magnetic nano-scale iron works in the drinking supply. I'm not questioning on the political front implications, I question the science of simply, 'radio reception and coffee making it better'. That doesn't make sense, but if there was some nano-magnetic jiz up in the coffee, that may make something like this a possiblity. Now at that, I'm trying to come up with ways to experiment further in this than just drinking coffee and playing with my radio. If we can try to refrain from sarcasm, and if not, at least come with a sarcasm that's Niels Bohr-ish. In this frame of questioning, lets think, if something like this was in fact plausible, how would we go about testing for it? I can't really take this to corporate funded learning institutions, this is a grass roots science project. --i am the kwisatz haderach (talk) 16:20, 27 January 2010 (UTC)

Earbuds usually use piezoelectric speakers rather than electromagnetic speakers, so I wouldn't expect to see a field large enough to move iron filings. --Carnildo (talk) 00:55, 27 January 2010 (UTC)

Lets say you ate some meat with "Mercury_(element)", aka poison, in it--which is a Diamagnetic, the Bioaccumulation of this and other magnetic elements in the body, I'm sure can cause Neurosis. --i am the kwisatz haderach (talk) 23:50, 28 January 2010 (UTC)

why has no one investigated the acid-base properties of chloramines?

I just want to find out how much having the chloro groups on there influences the acidity of the amino proton as well as the pka of its conjugate acid. However, google gives a grand total of zero results for such queries as "pka of chloramines" and "basicity of chloramines". HELP?!!! John Riemann Soong (talk) 18:32, 26 January 2010 (UTC)

Surely this must be a simple undergrad experiment, right? It can't be that troublesome to measure the pka of a chloramine. I just don't have the clearance for that kind of thing right now. John Riemann Soong (talk) 20:14, 26 January 2010 (UTC)

um, yeah, I googled "pka of chloramines" and got a shitload of sites which have information on that. I don't get one site that lists a bunch of pKa in like a table format, but I get LOTs of good stuff. Are you sure you typed the right thing in? This site gives the pKa of chloramine itself. This pdf seems to have a bunch of general properties of chloramine. here is a scholarly paper on the a specific experiment to determine the pKa of a specific chloramine derivative. I'm not sure how you could NOT find stuff. Both a straight google search and a google scholar search turn up tons of links. Also, have you tried both the CRC handbook and the Merck Index? They both tend to have lots of physical data on various compounds. --Jayron32 21:27, 26 January 2010 (UTC)

I don't get why there isn't an easily-available pKa index stored on a central federal science database or something? I don't have access to print materials. John Riemann Soong (talk) 00:08, 27 January 2010 (UTC)

Also that site doesn't give the pka of chloramine. It's a mirror site of Wikipedia. Also some other sites give irrelevant pkas of the wrong functional group -- like they give the pka of some alpha-proton or carboxylic acid that happens to have a chloramine group on it.

The guide you cited also doesn't say anything about the acid-base properties of chloramine. It gives a bunch of irrelevant stuff about water treatment and all that. I'm simply trying to oxidise an amine-alcohol compound with bleach to get a carbonyl group while minimising the amount of chloramine side product. I don't know why everyone seems to be focusing on the annoying water treatment aspect (no one should use chloramine for water treatment) and not on the organic synthesis perspective, which seems more important. John Riemann Soong (talk) 00:24, 27 January 2010 (UTC)

Finally, that last paper talks about a molecule with a sulfonyl group on it ... uhhhhh that's like talking about trichloroacetic acid when the pKa of acetic acid is desired. And I can't even access the paper because it's only an abstract. =( John Riemann Soong (talk) 00:28, 27 January 2010 (UTC)

You ask far too many inane and absolutely ridiculous questions. Open up a bloody book, or in this case, spend more than 30 seconds quickly perusing google before harassing these lovely Wiki reference desk folks. And stop asking questions like you've got an epic hardon for the answer and need "it" immediately. Try to be a bit less neurotic and nicer. MrFudgey (talk) 23:36, 26 January 2010 (UTC)

I do try to be nice but I don't know why my question goes unanswered for days. I mean, people ask simple questions all the time. I don't have access to anything besides my textbook, which btw, doesn't cover chloramines as functional groups. Also, when I google "pka of chloramines" (with quotes) I get no results, whereas without quotes returns me irrelevant results.

I spent around 5 minutes before giving up. Researchers often know pKas from experience so I thought it was something someone could tell me right off the top of the bat (along with the pka of phenol being around 9-10, mercaptans 10-11, amines 35 for the conjugate base and 10 for the conjugate acid, etc. John Riemann Soong (talk) 00:07, 27 January 2010 (UTC)

John. Listen to me. Go find a good old hard copy of the Merck Index or the CRC Handbook. Before coming here, did you look in either of those places? Any good chemist will have both lying around. Unfortunately, I have dug through my stuff, and I can't find them right now; I think my wife has taken them to her work and keeps our home copies there now. But seriously, try those two places first before asking something simple like this. --Jayron32 03:55, 27 January 2010 (UTC)

OK. Kiss me later. I found the SPARC online database located here:[5]. The software uses the SMILES system, but it has a little javascript SMILES converter from ChemDraw, so basically you draw the molecule in a simple ChemDraw applet, and it creates the SMILES string for you. If you play around with the site, it will give you all sorts of good info. It took me about 5-10 minutes to figure out the software, but once I did, I got the numbers. Based on their data, the pKa of H2NCl --> HNCl^- is 21.51, and the pKa of H3NCl⁺ --> H2NCl is 0.10. I hope that helps some! --Jayron32 04:10, 27 January 2010 (UTC)

planetary nebula

Do planet survive inside panetary nebula or they will get destroy in planetary nebula. Planetary nebula is between RGB and white dwarf, if Mars go in shell of planetary nebula will it be vanish? --209.129.85.4 (talk) 20:46, 26 January 2010 (UTC)

We don't know, it depends on the density of black-body objects which are often difficult to resolve from the ground because of atmospheric opacity in the infrared. With the Wide-field Infrared Survey Explorer we should have better data on which to answer that. 99.56.138.51 (talk) 03:26, 29 January 2010 (UTC)

Planet to keep a descent atmosphere

What do planet need to have a descent atmoshpere. Since Tango always say Titan will bleed away it's atmoshpere it is always unsource statement. This said Titan might keep it's atmosphere in 6 billion year sun, just the orange haze at the upper part will deplete, but it will keep some, just not that thick. Do planet diameter matter? Could planet be 1/10th the size of earth and still have an atmosphere. Pluto is also made of ice, I never hear anybody else say Pluto will just outgass. Could surface gravity also be weak and have the planet hold it's atmosphere.--209.129.85.4 (talk) 20:53, 26 January 2010 (UTC)

It's basically all about gravity. So the size and density of the planet/moon/whatever is what matters. Also, if the body is too cold then there may be no materials in it's makeup that are gaseous at those temperatures. Whether a planet like Pluto would outgass from icy stuff on the surface also depends on temperature. SteveBaker (talk) 21:50, 26 January 2010 (UTC)

Temperature is more important than that. The particles in the atmosphere will have velocities based on the Maxwell-Boltzmann distribution. That is a function of temperature. That means that, at higher temperatures, a greater proportion of the particles will have escape velocity and will escape. The remaining particles then exchange momentum through collisions and get back to the same distribution, meaning some more particles have escape velocity and escape. This process means that any atmosphere constantly loses particles to space, the atmosphere can only survive over long time scales if enough new gas is added to compensate for the losses. Those losses depend on temperature, so at higher temperatures you need more replacement gas to maintain the atmosphere. That is one of the main reasons that Titan has a thick atmosphere while the Moon, which is a very similar size and mass, and essentially no atmosphere at all. If Titan warmed up to similar average temperatures as the Moon, it would lose its atmosphere. I will try and find some references for that. --Tango (talk) 22:42, 26 January 2010 (UTC)

First of all, the source cited by the article the OP links to is talking about Titan getting warm enough for a water-ammonia ocean to form, not a water ocean. They are talking about maximum surface temperatures of about -70°C - a long way below Earth-like temperatures, but perhaps warm enough for life based on a slightly different biochemistry to us to arise. Those lower temperatures mean the atmosphere would escape far slower than it would at Earth-like temperatures, so could well survive for millions of years. --Tango (talk) 22:56, 26 January 2010 (UTC)

I have failed to find any reliable sources talking about Titan at Earth-like temperatures since a red giant sun isn't expected to heat it that much and people discussing terraforming dismiss it as essentially impossible, so no-one gets as far as thinking about what would happen to the atmosphere at those temperatures. --Tango (talk) 23:29, 26 January 2010 (UTC)

. Tango, I've heard the same argument about the Maxwell tail that you give on many occasions. It is certainly true that an object with a hot enough surface or a low enough escape velocity will bleed atmosphere into space. But I'm not sure how relevant that is to an object the size of the moon. Lunar escape velocity is ~2.4 km/s. At 300 K, an oxygen molecule has only a 1×10⁻¹⁵ probability of having enough velocity to escape (i.e. from Maxwell-Boltzmann). And in order to escape it needs to be moving in the right direction and living in a part of the atmosphere that is already of such low density that its mean free path is nearly infinite, or else it will collide with other molecules and lose energy before escaping. Once you combine low probability with low density, it seems like the rate of mass loss to the Maxwell tail for any gas much heavier than helium should be nearly nil under lunar gravity. By comparison it seems like collisions with solar wind particles, with typical velocities of 400-750 km/s, would be a much more effective means of providing gas molecules with enough velocity to escape out into space. So I'm not sure drawing your comparison to the Moon makes sense because I'm not sure if losses on the Maxwell tail are really a determinative factor for the Moon's lack of atmosphere. Dragons flight (talk) 00:40, 27 January 2010 (UTC)

Solar wind is certainly a key factor in atmospheric erosion - I think that's the main reason for Mars' lack of any significant atmosphere. 1×10⁻¹⁵ is quite high, though. How long do you think it would take for a particle with escape velocity to escape and for the distribution to adjust itself? I really don't know, but I'm guessing not long. A second, maybe? That means you lose 1×10⁻¹⁵ of the atmosphere every second. That corresponds to 22 million years to lose half the atmosphere. That means Jeans escape (as it is called) cannot be ignored on the timescales we are talking about. --Tango (talk) 00:55, 27 January 2010 (UTC)

No, you lose 1×10⁻¹⁵ of the fraction of the atmosphere with a mean free path long enough that escape is plausible before it hits other gas molecules. For oxygen molecules at 300 K that corresponds to a pressure of order 1×10⁻⁸ atmospheres. That certainly occurs, but only at high altitude in an atmosphere of non-trivial mass. Once you combine those two factors, the half life for an oxygen atmosphere to Jeans' escape from a lunar mass object should but much longer than the age of the solar system. Dragons flight (talk)

Ah, I've found a forum where someone has actually done the calculation: [6]. Apparently Titan's current atmosphere with an exobase temperature approximately equal to that of Earth's (1000K) would take on the order of a few billion years to escape (there are all kinds of assumptions involved in that calculation which almost certainly aren't true, so I'd say that is give or take an order of magnitude). They don't provide a reference for the formula or values they use and I haven't checked their arithmetic, but it all looks plausible. So, if Titan had been at those temperatures for its entire existence, we could expect the atmosphere to be largely gone by now, but heating it up either as a terraforming project or by the sun becoming a red giant should be reasonably safe. Either the source I was remembering reading years ago was wrong, or I was remembering it wrong and it was actually just talking about why Titan still has an atmosphere now despite being so small. However, the estimate that Titan will only warm up to about 200K when the sun goes red giant puts the entire premise on very shaky ground, so the question is pretty much moot. Thank you for the very interesting discussion and for giving me the incentive to actually look it up rather than rely on memory! --Tango (talk) 02:47, 27 January 2010 (UTC)

This is the link article links to. This book is made in 1997 now they estimate the sun expansion to be bigger inofrmations could be a little outdate. They said in first paragraph could be 300K, but for Wiki policy informations have to stick with the verifility.--209.129.85.4 (talk) 18:00, 27 January 2010 (UTC)

Number of seeds contained in a grape

How many seeds are on average contained in a grape?--87.11.120.169 (talk) 21:10, 26 January 2010 (UTC)

Seedless varieties have zero, Grignolino grapes can have as many as 10. Most normal varieties have between 2 and 4. SteveBaker (talk) 21:47, 26 January 2010 (UTC)

• Thanks for the aid!--87.11.120.169 (talk) 23:00, 26 January 2010 (UTC)