Apparently a genuine concern of scientists carrying out the first detonation of an Atomic bomb was that it could ignite the atmosphere.
Is this feasible with any kind of nuclear weapon or is it just 1940s scientific mumbo jumbo up there with nuclear powered cars and improving your health by smoking?
I am not a scientist, but as far as I can tell, it just doesn’t seem feasible. There are two ways (that I know of) for the atmosphere to be “burned off” due to an explosion:
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[li]Normal burning (chemical reaction)[/li]For this to happen, one of two things has to occur:
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[li]a significant portion of the atmosphere would have to be a flammable gas, which it is not, otherwise the world would be engulfed in flame any time lightning struck or somebody lit a match. Who knows…maybe this was the case a long, long time ago and our current atmosphere is made up of the exhaust gases produced as a result of the flash-burning.[/li]
or…
[li]normal gases (nitrogen, etc) would be forced to oxidize. This doesn’t happen because forcing that kind of reaction would be highly endothermic, requiring a constant input of much larger amounts of energy than would be released by the actual combustion.[/li][/list=a]
[li]Nuclear reaction.[/li]
For this to happen (nuclear fusion/fission/whatever of the existing atmosphere) there would have to be a huge uncontrolled chain reaction. This doesn’t happen because gases are naturally not very reactible material. Atoms are too spread out to sustain a chain reaction, and not enough neutrons released would hit a nucleus and induce another reaction. Even Uranium and Plutonium fission under very special circumstances (they can’t just be put together and viola! [misspelled intentionally] a nuclear explosion, they have to be slammed together and compressed to cause the reaction to escalate). Otherwise they emit lots of radiation and heat up, but don’t explode.
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As always, anybody who knows more about this than I do is more than welcome to jump in and correct me (not that you need or wait for an invitation!)
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*Originally posted by Joe_Cool *
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[QUOTE…it just doesn’t seem feasible…**[/QUOTE]
To be fair, it’s much easier for me to say this considering I can look around, take a breath, and see that the atmosphere DIDN’T burn off when they detonated…quite a different story from the perspective of doing the first one. 
It was never a genuine concern of the scientists involved, nor, for that matter, of any scientist. There were worries about the radiation, and the EMP, and the fallout, and the effect on the test site, all legitimate, but they all knew well the reasons given by Joe_Cool. It was, of course, a worry of many luddites and anti-nuke activists, but these are much the same people who raised such a stink about the risk of the Relativistic Heavy Ion Collider producing a black hole that would engulf the Earth, which has even less basis in science. Rest assured that physicists aren’t that stupid; were there any real chance that what we’re doing would destroy the Earth, we wouldn’t be doing it on the Earth.
OK.
Chemical: It is true that our atmosphere is not composed of flammable gases. Why not? Well, our atmosphere is full of oxygen. Any flammable gases are quickly oxidized (burned). Our atmosphere used to contain all kinds of flammable gasses…methane, hydrogen, whatever…but all that was destroyed when the first cyanobacteria perfected photosynthesis and dumping O2 into the atmosphere, poisoning the whole world. So that’s not a problem anymore.
Nuclear: You release a lot of energy when you set off a fission bomb. That’s used in the creation of fusion bombs. A small fission bomb is used to heat and compress deuterium to the point where it fuses. The heat and energy of the fusion reaction quickly dissapates the hydrogen to the point where it doesn’t fuse anymore…but you still have quite a lot of energy released.
Now, any element smaller than iron will release energy when it is fused. The only trouble is that you need a hell of a lot of heat and pressure to make this happen…we’re talking heat of the sun or higher. But a fission bomb can generate very high temperatures and pressures. What if there was enough heat to cause the nitrogen and oxygen in the atmosphere to undergo fusion? And suppose that released so much energy that it caused more of the atmosphere to undergo fusion? Probably the explosion would dissipate the energy so quickly that fusion would stop, but what if it didn’t?
My understanding (I think this is from some Feynman book…don’t have a cite…) is that some people at Los Alamos got to thinking about this. It wasn’t that they thought such a scenario was likely, but they spent a little time doing some calculations to convince themselves that it couldn’t happen. The big problem with a fusion chain reaction is that the energy of the fusion reaction itself will dissapate and shut itself off. Not a problem, but it’s nice to know they checked.
“Rest assured that physicists aren’t that stupid; were there any real chance that what we’re doing would destroy the Earth, we wouldn’t be doing it on the Earth.”
We can churn pollutants into the atmosphere and seas, rip up large areas of natural habitats, strip the Earth of its resources but we can’t ignite the atmosphere in one fell swoop? Makes sense to me…
Exactly. Bad though pollution, strip mining, etc. may be, they’re nowhere near capable of destroying the Earth, nor of rendering it uninhabitable. This is espescially true when considered on a case-by-case basis: A single car releasing exhaust into the atmosphere doesn’t produce enough pollution to destroy any amount of habitat, for instance; it’s only in the aggregate that pollution becomes a significant problem. This is in contrast with the alleged danger of burning away the atmosphere, which as a single event would serve to render the entire planet uninhabitable to everything but a few simple bacteria.
Besides, it generally isn’t scientists responsible for environmental damage, at least not directly. Most environmental damage is due either to corporations or the net contributions of all citizens, as with cars.
First restaurant then: Great food, no atmosphere.
I vaguely recall reading that Oppenheimer was taking bets that the atmosphere wouldn’t ignite. I don’t know how the other guy was planning on collecting if it had ignited.
“AAAaaah! The atmos-peer! AAaaah!”