Wikipedia:Reference desk/Archives/Science/2011 February 28

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February 28

Spaying and neutering of feral animals

I know that there are groups in America who trap feral animals (cats mostly, but sometimes dogs) and have them spayed/neutered and then return them to their ranges. I just had my cat spayed and she must wear bandages and a funnel for about 10 days, as per the vet's orders. How does this work for feral cats? Do they stay at the vet for a week or so, or are they turned loose early with some sort of slowly-degrading bandage? The Masked Booby (talk) 00:58, 28 February 2011 (UTC)

I think they're just kept for a couple of weeks in a cage. This site looks like it has all the answer but you have to go through a free registration process requiring an email address to access it. Vespine (talk) 01:17, 28 February 2011 (UTC)

Not to be insenstive, but wouldn't a .22 have a similar effect on population control at a tiny fraction of the cost? Googlemeister (talk) 17:31, 1 March 2011 (UTC)

Yes but it's insensitive. Vespine (talk) 21:39, 1 March 2011 (UTC)

it can also have other effects - feral cats are known to reduce the rodent population, for example. Kill the cats, you'll end up with more mice - which are infinitely harder to control and far more economically destructive. --NellieBlyMobile (talk) 01:46, 4 March 2011 (UTC)

where do aliens come from

where do aliens come from ? — Preceding unsigned comment added by Joshuad95 (talk • contribs) 04:06, 28 February 2011 (UTC)

Presumably the same place humans come from. But no one has even seen an alien, so it's hard to know. Ariel. (talk) 04:16, 28 February 2011 (UTC)

We have articles on these kinds of aliens, these aliens and even a list of aliens. Vespine (talk) 04:58, 28 February 2011 (UTC)

"Alien" is a word derived from the Latin words aliēnus (“belonging to someone else, exotic, foreign”) and alius (“other”). Basically, an "alien" is a word for someone or something from elsewhere. Hence the terms "illegal alien", "resident alien", and even "alienation" are literal usages of the term "alien", and are in no way metaphorical. So the answer to the question "where do aliens come from" is simply "somewhere (anywhere) else". -- 174.31.194.183 (talk) 05:01, 28 February 2011 (UTC)

If you mean extraterrestrial life, the general assumption seems to be that it would need an environment similar to that of Earth, which would mean a small, terrestrial planet/asteroid or a moon of a larger, Jovian planet. Planets like Venus, which at first seem inhospitable to life, due to extreme temperatures and pressures, may support life in a manner similar to that found at undersea volcanic vents on Earth. But, alien life could also be "totally alien", perhaps evolving in deep space or as magnetic currents inside stars. We don't know anything about such life, though, so it would be difficult to judge whether it's possible and what it requires, making it impossible to pick probable locations. StuRat (talk) 22:27, 28 February 2011 (UTC)

Pureed Food

Do vegetables and fruit lose their vitamins and nutrients if they are pureed? And if they don't if you added the puree into food like spaghetti or meatballs and then cooked the meatballs, would that cause the vegetables or fruit to lose their vitamins and nutrients, would it still be just as healthy as if you ate the veggies steamed or the fruit raw? —Preceding unsigned comment added by 70.141.255.136 (talk) 06:07, 28 February 2011 (UTC)

Vitamins and nutrients aren't destroyed by macroscopic mechanical stress. You can crush a cucumber with a hammer, steamoll a pumpkin, the vitamins and nutrients will stay intact. They are however destroyed or ruined by chemical attack, thermal damage, or excessive air pressure. Plasmic Physics (talk) 06:57, 28 February 2011 (UTC)

It may be a bit more complicated than that - vitamins and the like are stored inside cells where they are protected to some degree. Pureeing them breaks the cell wall exposing them to further damage. But in general I think it's not something to worry about. Ariel. (talk) 07:00, 28 February 2011 (UTC)

Yes, and breaking those cell walls makes it easier for our body to absorb the vitamins. No point in protecting the vitamines so that they can be flushed down the toilet. Dauto (talk) 15:12, 28 February 2011 (UTC)

Some of the water-soluable vitamins, such as Vitamin C, may dissolve into the cooking water. But if you use the cooking water when making the sauce etc, then that is not a problem. 92.15.3.182 (talk) 11:11, 28 February 2011 (UTC)

Something else to consider is that pureed fruits and veggies may oxidize and decompose more quickly, so don't puree until right before you consume them. StuRat (talk) 07:55, 2 March 2011 (UTC)

Pureed fruits and veggies are able to retain their contents and original compsition depending on the way in which they are processed, wheter at home or purchased from outside vendor. Like, while cooking at one particular stage, if tomato puree is needed, then it is possible to smash tomatoes and make puree out of it, however, most of the times it depends on the approach, way and method in which a puree is to be made. Making puree is a part of cooking process, however, puree can be made seperately and stored and then also routine cooking process can be started. Thus if vegetables and fruits when they are in their original form are converted into puree then they will retain their contents and add taste and flavor to the food that is been cooked. aniketnik (talk) 11:43, 2 March 2011 (UTC)

UV-A, UV-B, UV-C of metal halide lamp

Hello,

I wanted to ask here how dangerous the UV radiation of a 150w metal halide lamp can be, compared to the sun( i have the numbers of the lamp they are:

• UV-A:6.1
• UV-B:0.003
• UV-C:0.006. microwatt/cm2/500 lux

I cannot find the numbers for the suns radiation on earths surface (average, temperate climate)
TY
DST — Preceding unsigned comment added by DSTiamat (talk • contribs) 09:59, 28 February 2011 (UTC)

Sorry, I couldn't find anything. And if you get no other replies it means no one else found anything either. Ariel. (talk) 23:23, 28 February 2011 (UTC)

Of my interest would be the numbers of the sun, I have the numbers of the lamp and can make my own conclusions, TY Ariel, anyone?
DST — Preceding unsigned comment added by DSTiamat (talk • contribs) 08:17, 1 March 2011 (UTC)

solar spectrum

The Thekaekara Spectrum shows the amount of radiation at different wavelengths from the sun. Graeme Bartlett (talk) 11:46, 1 March 2011 (UTC)

Surely this is a simple case of dimensional analysis. John Riemann Soong (talk) 10:20, 3 March 2011 (UTC)

Birds and eyelashes

Random question, but something I was thinking about. How common is it for birds to have eyelashes? --95.148.106.158 (talk) 10:34, 28 February 2011 (UTC)

Birds do not have eyelashes. Some have bristles, which are feathers that lack barbs, around the eyes which appear to be similar to eyelashes. That feature is primarily only in insect-eating birds. -- kainaw™ 13:34, 28 February 2011 (UTC)

And do they serve to keep insects out of the eyes ? StuRat (talk) 22:13, 28 February 2011 (UTC)

view full size - not easy to see, but they're there

Budgerigars have eyelashes. The one in the pic doesn't have particularly prominent/thick lashes, but that's the only pic I could find on here with sufficient resolution to show them at all. I think (IIRC) that Cockatiels do too. --Kurt Shaped Box (talk) 22:57, 28 February 2011 (UTC)

They're also mentioned in our articles on the Hornbill and some of the Vulture species. Our Eyelash article mentions that they are barbless feathers as Kainaw describes, rather than true hairs as in mammals, but I don't think that that excludes them from being defined as eyelashes. 87.81.230.195 (talk) 23:39, 28 February 2011 (UTC)

It appears that ornithologists refer to those bristles as "eyelashes". --Sean 16:44, 1 March 2011 (UTC)

Yeah, I don't see anything particularly wrong with taking an 'eyelash is as eyelash does' attitude towards this... --Kurt Shaped Box (talk) 22:00, 1 March 2011 (UTC)

So, having a look at another couple of parrot species...

• 
  African Grey Parrot appears to have (very fine) 'eyelashes'
• 
  as does this Umbrella Cockatoo
• 
  Whereas this macaw seems to have a ring of 'nodules' (dunno) that may serve a similar purpose

--Kurt Shaped Box (talk) 23:53, 28 February 2011 (UTC)

The close up of that macaw is going to give me nightmares! lol.. Vespine (talk) 02:00, 1 March 2011 (UTC)

Reminds me a bit of elephant skin up close... --Kurt Shaped Box (talk) 22:00, 1 March 2011 (UTC)

It is tempting to look at such pictures and think that there must be a common basis for eyelashes. But this means tracing back from birds through the dinosaurs and other sauropsids to the synapsids, and supposing that hair and feather patterning (and perhaps, at least in most basic concept, the hair/feathers/scales themselves) have been conserved throughout all that evolutionary distance. Is it possible that basal amniotes possessed the ability to pattern eyelashes around the eye, or even to mount them on eyelids? There's a discussion of comparative homology between eyelids of amphibians, frogs, turtles, and crocodiles here [1] - there is a certain amount of uncertainty on major points, but the overall consensus seems to be that the structure could indeed be so ancient. But eyelashes won't be pulled out of the literature (nor, I suppose, the rocks) quite so easily. A person can look at things like the eyelash viper and crested gecko and wonder, but admittedly, it's not the same thing. At least to a quick search, the secret remains undiscovered. Wnt (talk) 23:44, 1 March 2011 (UTC)

Can holograms work in broad daylight?

Does it need to be very dark for them to be clearly visible? ScienceApe (talk) 13:26, 28 February 2011 (UTC)

It depends on what you mean by hologram. Ones that are generated by lasers must be brighter than the surrounding light. However, white-light holograms (seen commonly on credit cards) work best in daylight. -- kainaw™ 13:30, 28 February 2011 (UTC)

Yeah I was talking about the holograms that are suspended in midair, presumably generated by lasers. ScienceApe (talk) 14:19, 28 February 2011 (UTC)

Such holograms does not exist. A hologram can show objects in front of or behind its surface but only in the direction of the hologram as seen from the viewer. --Gr8xoz (talk) 17:33, 28 February 2011 (UTC)

I have seen laser-generated holograms that you could walk around 360 degrees. They are expensive. The one I was was being licensed by a popular magician for his stage show - which should give a general idea of the cost. -- kainaw™ 17:35, 28 February 2011 (UTC)

That seems interesting, do you have any idea of where to get more information. Are you sure it was a hologram? not every 3D projection is a hologram. Was there any transparent materials between you and the background? --Gr8xoz (talk) 18:50, 28 February 2011 (UTC)

I have never been able to find the manufacturer online. I was paid through a company named "Magic Stage", which I also cannot find online. I did computer programming - which was the easy part. The setup required a lot of lasers on little pivots. The best I could tell, the lasers do not produce noticeable light until the beams cross. I programmed vector lines in 3D space, which the lasers "drew" in the air - oscillating quickly to keep it visible. The program I wrote just drew a little red apple with a green leaf on top. The demonstrator had a transmitter on his wrist that relayed the position to another computer so as he moved his hand around the apple moved with it - looking like he was holding it. That's about all I remember - and it was a good 20 years ago. I'm sure that the technology is much better now. -- kainaw™ 19:11, 28 February 2011 (UTC)

Was it something like this? http://www.aist.go.jp/aist_e/latest_research/2006/20060210/20060210.html 83.134.177.173 (talk) 19:53, 28 February 2011 (UTC)

Yes. It was just like that with two exceptions. First, I never heard anyone mention plasma. Maybe the plasma in your example makes it much easier to see in normal lighting. Second, the one I saw used three colors (red, green, blue) to produce nearly real-color images. Now that I think of it - I may be mis-remembering the existence of blue since the only example I saw used red and green. I've always meant to get two laser pointers to see if they make a dot of light when you cross the beams, but just never think to try it when I actually have two laser pointers on hand. If it works, then there's no "plasma" involved - just a disruption of the laser beam. -- kainaw™ 19:58, 28 February 2011 (UTC)

That isn't a hologram BTW. Ariel. (talk) 20:31, 28 February 2011 (UTC)

I think the plasma involved is just air made very hot by pointing multiple lasers at it, rather than the plasma of neon that's used in a plasma globe - if that was what you were thinking. 81.131.17.66 (talk) 20:59, 28 February 2011 (UTC)

The air would not get hot! If the laser was strong enough to do that it would burn holes in the walls. Ariel. (talk) 23:15, 28 February 2011 (UTC)

The lasers are focussed, with the focal points in mid-air, and there it gets hot. After that point, the beam diverges. Icek (talk) 23:51, 28 February 2011 (UTC)

Reading it again, it seems it only uses one laser, focused through a lens. 81.131.65.79 (talk) 12:32, 1 March 2011 (UTC)

That sounds like an incredible amount of effort to go to, just to make an apple appear or disappear; something any magician could do with a regular apple. Maybe there's important information missing from the descriptions above. Light is not cohesive, the main "problem" with holograms is you can see THROUGH them. That might work if it is kept in front of a black curtain with the audience only to your front, but in other situations it would fail. Lasers also definitely do NOT make a visible "point" of light where beams intersect in air, they need something to reflect off, (the little balls of plasma are definitely not "rgb"). I'm not calling anyone a liar, but I smell something very fishy, IMHO something doesn't add up. Vespine (talk) 00:23, 1 March 2011 (UTC)

I made an apple disappear today for lunch and I'm not even a magician. Dauto (talk) 02:12, 1 March 2011 (UTC)

http://www.youtube.com/watch?v=thOxW19vsTg What's going on in this video? It seems like it's a legit 3D hologram. ScienceApe (talk) 03:03, 1 March 2011 (UTC)

Despite what they call it, it has absolutely nothing whatsoever to do with holograms. It's just computer graphics. They have a bunch of cameras (in a circle) that record the reporter, then they add that to the outgoing television stream - the person physically there does not see her. The "new" thing, is that the computer can dynamically adjust the look of the outgoing stream based on the motion of the camera. But otherwise it's not much different than the special effects shot of a hologram in Star Wars. Ariel. (talk) 03:22, 1 March 2011 (UTC)

Yeah, I looked into it and it seems like that is in fact the case. Really deceptive especially when it's coming from a damn news source. ScienceApe (talk) 03:30, 1 March 2011 (UTC)

I agree, they should not have called it a hologram, maybe call it a virtual presence or something. A true real time hologram would be a pretty big deal - it requires an enormous amount of computing to generate one on the fly. No ones done it yet as far as I know. Ariel. (talk) 03:50, 1 March 2011 (UTC)

MOND or MOG theory

If MOND or Scalar–tensor–vector gravity turns out to be correct, will any changes need to occur to other physical laws apart from gravity? Would it ever have any effect on everyday life? Thanks 92.29.122.72 (talk) 15:33, 28 February 2011 (UTC)

No, and No. Dauto (talk) 16:07, 28 February 2011 (UTC)

The second one seems to be answered in the article anyway:

On the scale of the solar system, the theory predicts no deviation[7] from the results of Newton and Einstein. This is also true for star clusters containing no more than a maximum of a few million solar masses.

Nil Einne (talk) 17:29, 28 February 2011 (UTC)

Just to answer the last question; when scientists tweak existing laws, it doesn't actually change the nature of the universe. The universe keeps doing what it always has, so there's no change to what happens to you. What changes is our understanding of how the universe works. Just because Copernicus figured out that the earth moves around the sun doesn't mean that it hadn't been doing that before he figured that out! Its the same deal here; if our understanding of gravity changes, it doesn't mean that it hadn't been doing the same thing even before we changed the laws... --Jayron32 17:43, 28 February 2011 (UTC)

No, really? I am not a three year old, thanks. 92.24.179.104 (talk) 22:18, 28 February 2011 (UTC)

You asked if it would have an effect on everyday life, and Jayron answered that question. --Sean 16:46, 1 March 2011 (UTC)

The second part of that is not true. 92.15.8.168 (talk) 00:10, 3 March 2011 (UTC)

Modified Gravity Makes Galaxies Brighter Count Iblis (talk) 22:41, 28 February 2011 (UTC)

Thanks for your answers, but I don't think anyone has shown signs of being sufficiently expert to give a considered reply rather than just repeating a snippet of what they've just read on Wikipedia. Physical laws have to be consistent with each other, so a change in one of them is likely to imply changes in some others. Secondly, having a better understanding of how gravity works may lead to new technology. 92.15.8.168 (talk) 00:25, 3 March 2011 (UTC)

I think that the answer of "at the scale we observe the universe, no changes would be needed to explain what we already see and understand" is fairly accurate. The biggest change would not be retroactive, because current laws and theories are based on things we've already observed and found consistant, but going forward. It may help us to explain things that are currently unexplained. There are things that are currently hard to explain, such as the fact accretion disks are disks and not spheres, that the theory might help explain. As to the changes to everyday life? Well it depends on your definition of "everyday" very little astronomical has any direct effect on the average life of the everyday "man on the Chapham bus" but improved understanding could lead to new models of the universe and greater understanding of gravity effects (especially gravitational lensing) would improve our ability to make accurate predictions about stellar phenomenon and understand the shape and distribution of the universe. HominidMachinae (talk) 06:38, 9 March 2011 (UTC)

Snake venom myokymia

I saw on a TV program that some type of snake can cause this.

1) Which is it ?

2) Also, could this venom be used (in low dosages, of course), to exercise the muscles of patients who are either comatose or immobile, to prevent muscular atrophy ?

StuRat (talk) 19:35, 28 February 2011 (UTC)

Timber rattlesnake?[2] DMacks (talk) 20:46, 28 February 2011 (UTC)

Thanks, I updated our article on Crotalus horridus. Any comments on part 2, anybody ? StuRat (talk) 05:15, 1 March 2011 (UTC)

Christchurch volcano

Following the recent quake there, a noticeable increase in the temperature of water in the harbor has been measured, leading to speculation that the earthquake may have either triggered, or been triggered by, an increase in volcanic activity in the area. So, then, which volcano(es) are involved and do we have article(s) on them ? StuRat (talk) 19:38, 28 February 2011 (UTC)

New Zealand has a lot of volcanoes. It's right on the Ring of Fire, and Volcanism of New Zealand lists quite a number. The map shows that most of them are on the North Island, not the South. But List of volcanoes in New Zealand has 4 candidates on the South Island. And of those, the first two are exactly in the right spot: Akaroa and Lyttelton Harbour. However those are very old, so it may also be a new unnamed volcano. Ariel. (talk) 20:56, 28 February 2011 (UTC)

Right, so which one is the likely candidate ? Also, do we have any articles on those volcanoes ? (The links you provided aren't to volcano articles.) StuRat (talk) 21:11, 28 February 2011 (UTC)

If it's an existing one, then most likely is Lyttelton Harbour I guess. But I think more likely is that it's a new opening that may or may not eventually become an underwater volcano. And I know those aren't links to volcano articles, but that's what was there. We don't seem to have anything else, probably because those volcanoes are so old. Ariel. (talk) 23:19, 28 February 2011 (UTC)

As the volcanoes are there a result of the subduction zone, it may just mean that the earth moment has provided new crevasses for sea water to peculate down to the hot rock in the zone (and then rise again). So I think it might be less to do with volcanism more to do with popular fear-mongering. In a few months/years time, the sea temperature may return to its former levels. Crack in the overburden around the volcano aren't going to afford easier passage for magma to rise. If it wants to rise - it will regardless of the overburden and the upage will have been noticed before now. Also, the quake was in the wrong place and over the subduction area --Aspro (talk) 21:21, 28 February 2011 (UTC)

The volcanoes on the South Island are not subduction-related as there is no subduction zone, the plate boundary being of transform fault type. The volcanoes are examples of intraplate volcanism that happened more than about six million years ago. Mikenorton (talk) 22:28, 1 March 2011 (UTC)

Chromosome numbers and speciation

We have articles about how an individual can have a different number of chromosomes than its parents, but how does this change occur to an entire species? When the first proto-human was born with 46 chromosomes instead of the 48 of chimps and gorillas, how did that individual produce viable offspring with its 48-chromosomed mates? If it happened gradually over many generations, why don’t we see species with fractions of a chromosome as part of their speciation? —Arctic Gnome (talk • contribs) 19:46, 28 February 2011 (UTC)

It seems that this individual must have reproduced with "normal" individuals matching one of his chromosomes to two of the "normal" ones. What is a fraction of a chromosome anyways? Dauto (talk) 19:54, 28 February 2011 (UTC)

Chromosomes do sometimes break: [3]. StuRat (talk) 02:02, 1 March 2011 (UTC)

When the number of chromosomes changes, it is usually because either one chromosome has split in two or two chromosomes have merged into one. As long as all the genes are still arranged in the same way, with just an extra split/join, then reproduction is still possible (although fertility would probably be greatly reduced). Women with Down syndrome can (with difficulty) reproduce, for example, despite having an duplicate chromosome. --Tango (talk) 20:03, 28 February 2011 (UTC)

There are people right now who carry abnormal chromosomes yet are phenotypically normal and reproduce -- albeit with a higher chance of having an offspring with severe birth defects. See Robertsonian translocation and balanced translocation. There are some rather complicated models of how primate chromosomes evolved - see [4] and [5]. --- Medical geneticist (talk) 20:11, 28 February 2011 (UTC)

Not an 'answer' but you might find Chromosome 2 interesting. I think the questions you are asking are one area which isn't fully understood yet. why don't we see fractions of a population with different numbers of chromosomes is a very interesting question... Different number of chromosomes occurs above the level of species. All Hominidae have 24 pairs of chromosomes, so it's possible to see many "speciation" events before you see any "chromosome count altering" events making them relatively rare, we struggled to find "speciation events" in action so it might be even harder to find the chromosome events. Also, if you think about scenarios where such an event might take place, they might take place relatively "fast", so it might make such events very hard to "catch in the act" so to speak. Vespine (talk) 23:23, 28 February 2011 (UTC)

We are Hominidae and we don't have 24 pairs of chromosomes... --Tango (talk) 23:53, 1 March 2011 (UTC)

We do, in fact, see species where interbreeding members of a population have different numbers of chromosomes. The phenomenon is called chromosomal polymorphism. In addition to the linked article, the phenomenon is discussed at Karyotype#Chromosomal_polymorphism. One observation which to me is pretty convincing that the evolving human species must have gone through a long period of chromosomal polymorphism (involving chromosome 2 and the two corresponding ape chromosomes), is the fact that a large number of molecular polymorphisms in the Major histocompatibility complex, by far predate the split between humans and chimps. This observation has been called the trans species hypothesis by Jan Klein. See also Jan_Klein#Trans-species_Polymorphism. --NorwegianBlue ^talk 21:58, 1 March 2011 (UTC)

Sorry, I did actually mean all Hominidae except us. Vespine (talk) 00:16, 2 March 2011 (UTC)

Toxorhynchites?

I was discussing mosquitoes with another entomology student, and he mentioned a blood-feeding Toxorhynchites species in Panama. I was quite certain that all Toxorhynchites species were nectar-feeding only and not one species was hematophagous. He mentioned that the mosquito was metallic, and thus he inferred it was a Toxorhynchites species. Can anyone find information on what mosquito species he may be referring to?130.127.130.191 (talk) 20:55, 28 February 2011 (UTC)

Well I can't find anything in google scholar searching for 'Toxorhynchites blood panama'. If it was true I'd imagine it would be mentioned somewhere in this or this which I can't access unfortunately. SmartSE (talk) 22:30, 1 March 2011 (UTC)

According to the first article, all Toxorhynchites species are not blood-feeders, as I suspected. Thank you for finding that.130.127.108.23 (talk) 04:54, 2 March 2011 (UTC)

Relativity and nuclear bombs

Did Einstein's theory of relativity have anything to do with discovering how to build and explode nuclear bombs? Could the latter have been done without the former? 92.24.179.104 (talk) 22:25, 28 February 2011 (UTC)

There have been previous Ref Desk threads about this. Certainly the role of special relativity (and "E=mc²") in nuclear physics is grossly oversold, and I think that the Manhattan Project could have succeeded without any understanding of special relativity, but that doesn't mean that special relativity wasn't helpful to them. -- BenRG (talk) 22:51, 28 February 2011 (UTC)

(EC)No, not directly. Off course relativity is one of the pillars of 20th century physics so it is a fundamental part of the science of physics as a whole including nuclear physics. Dauto (talk) 23:00, 28 February 2011 (UTC)

Einstein's other, "more important contribution", led to our understanding of modern atomic theory, and probably had more direct impact on the line of research that eventually led to nuclear fission. General relativity has more direct application to astronomy and gravity than it does to atomic or nuclear physics. Lawrence, Fermi, and Oppenheimer all made theoretical contributions that had far more direct impact on the discovery of nuclear fission than any work by Einstein. And even these contributors were primarily theoretical. Most physicists concede that experimental radioisotope research predated modern nuclear theory; but I don't think anyone could have discovered the energetic applications of fissioning radioisotopes without the development of theoretical nuclear physics. Nimur (talk) 00:09, 1 March 2011 (UTC)

Not forgetting the earlier work by Ernest Rutherford. 92.24.191.30 (talk) 12:48, 1 March 2011 (UTC)

Einstein's main contribution to the bomb was writing a letter to Franklin Roosevelt. Edison (talk) 01:47, 1 March 2011 (UTC)

... see Einstein–Szilárd letter (although, according to that article, Szilárd wrote most of the text). Gandalf61 (talk) 13:06, 1 March 2011 (UTC)

There is some good discussion of the ways in which it does and does not apply here. It's hard to ask ahistorical questions about what would have happened without something, but if you could somehow have quantum and nuclear theory without Einstein (only somewhat imaginable), then you could have a bomb without him. But you can say the same thing about Newton. --Mr.98 (talk) 03:00, 1 March 2011 (UTC)

E=mc² tells us that a large amount of energy is potentially available from nuclear reactions, but it does not address the issue of how to access this energy in practice. Uranium-235 is the only isotope that occuipes the narrow gap allowing it to be sufficiently fissile to sustain a chain reaction but at the same time having a long enough half-life to be naturally occuring on Earth in macroscopic quantities. Without U235, is not clear to me that we would have any mechanism to tap significant amounts of energy from nuclear reactions with current technologies. Gandalf61 (talk) 13:29, 1 March 2011 (UTC)

You can describe the energy release from U-235 entirely without recourse to relativity, though, which I think is Serber's point in the link I gave. If you calculate the electrostatic repulsion of two Barium-sized nuclei that happen to be right next to each other (but outside of the Coulomb barrier), you end up with the majority of the energy released in a fission reaction. (Some things don't work so easily, like the energy of the neutrons that result from it, at least as far as I know.) Presumably you could have discovered nuclear fission without the knowledge that E=mc^2. Your knowledge would be incomplete, to be sure, but seeing it as just an electrostatics problem gets you most of the way there.

As for fissile material without U-235... you could use particle accelerators to generate LARGE amounts of neutrons which would then be used to "seed" U-238 or thorium to create either plutonium or U-233. Such an idea was actually pursued by the U.S. government in the late 1940s and early 1950s, when they thought that they might have a uranium shortage. It was code-named the "Materials Testing Accelerator", and was the original basis for Lawrence Livermore National Laboratory (before it was a bomb design lab; our article is sadly deficient on this point, but if you Google around you can find a lot of info on it), even though it was cancelled when it became clear that the US had abundant uranium for its nuclear programs. It's a very inefficient neutron source, though, compared to a nuclear reactor (huge amount of electrical energy, gignormous facility, for not a lot of neutrons by comparison). But if we were imagining a hypothetical universe without U-235, that's one way you'd go about making other fissile materials. --Mr.98 (talk) 19:27, 2 March 2011 (UTC)

All particle accelerators use special relativity, for one. It's kind of hard to calculate the kinetic energy, critical mass, etc. required of various atomic physics calculations without special relativity. John Riemann Soong (talk) 10:21, 3 March 2011 (UTC)

Do you mean it is practically difficult or theoretically difficult? I agree that calculating those things without particle accelerators would have been hard in the 1930s, and you need SR when dealing with particle accelerators. But I don't think you need SR to talk about critical masses, do you? You need quantum to a degree, but SR? --Mr.98 (talk) 14:21, 3 March 2011 (UTC)

Did knowledge of the theories of relativity make designing the bomb more likely and quicker? In other words, was relativity a step towards making the bomb? Was relativity the only thing that indicated that a lot of energy could in theory be released? Thanks 92.15.30.242 (talk) 12:33, 4 March 2011 (UTC)

I suppose the answer to the first two of those questions are covered by the article link given by Mr. 98 above. Thanks 92.24.182.238 (talk) 20:25, 4 March 2011 (UTC)