Did the non-zero risk of the atmosphere igniting increase as nuclear weapon yields got larger and larger?
Obviously a result of watching Oppenheimer.
In: 789
They knew that in stars common elements of the earth’s atmosphere (like hydrogen, oxygen & nitrogen) will combine into other elements, releasing huge amounts of energy in the process. The fear was that a nuclear bomb would spark the same kind of reaction in the earth’s atmosphere.
They did calculations, and decided that even if some nuclear fusion did occur, the energy lost would outstrip the energy gained, and there would be no runaway reaction. The exact mechanisms require a decent level of understanding of nuclear physics (which I don’t have at the moment).
The risk didn’t increase, because it was never a real possibility. The “risk” was that their understanding of the science wasn’t correct or they missed something (like the unexpected reaction of Lithium-7 during the Castle Bravo test).
The type of physical reactions that happen in a nuclear weapon (or in a star for that matter) depend on density and concentration. You have to have both enough material AND have it be pure enough AND have it all adjacent to itself (a big ball of highly radioactive material, basically). Only then will it go bang. Once those conditions are met, the constituent parts of the atoms start interacting with each other in a way that ultimately tears the atoms to pieces, but without those conditions all you have is a bit of radiation. You would not want to stand next to it for long, but that is very different from a bang.
The atmosphere is insufficiently dense for this type of chain reaction to perpetuate itself outside the actual blast radius of the bomb. The bomb goes bang, and there is a big shockwave, but every atom outside the immediate blast radius just runs away when it comes to their turn to “join” the bang. The atmosphere is too squishy, basically. In order for the atmosphere to ignite, it would have to be contained in such a way that the atoms couldn’t run away from each other such that they would be “forced” to join the reaction and I don’t think even a James Bond villain is building a big containment shell around the whole planet for that purpose. A star works because there is so much material that *gravity* holds the material in place and the chain reaction can become self-sustaining, but a planet is not a star.
Edit: later, in the 50s, we came up with ways to make bombs that use gasses present in the atmosphere in great amounts (eg. Hydrogen), but same thing applies — the hydrogen making the bang is contained in the bomb under controlled conditions. The hydrogen just floating around in the atmosphere is too “loose” and too dispersed for such a reaction to continue the reaction that happens inside the bomb when it is detonated. We basically created a miniature star, but it could only last for as long as the bomb itself could hold together — a few milliseconds, maybe. Once the bomb’s containment was breached and the initial blast dissipated, the pressure drops back to “atmospheric pressure” and the reaction can no longer happen. Again, in a star this is perpetuated by gravity, in a bomb by a containment vessel. But in normal environment on Earth those conditions are simply too weak to enable the atoms to interact in that way.
I have not seen the “Movie” yet. However as to the actual historical events as actually described (and as such what – archived – on the internet….)
There’s this:
“a study was commissioned to explore the matter in detail, and six months before the Trinity test, the very first detonation of nuclear device, Edward Teller and Emil Konopinski announced their findings in a report with the ominous title “Ignition of the Atmosphere With Nuclear Bombs.”
“It is shown that, whatever the temperature to which a section of the atmosphere may be heated, no self-propagating chain of nuclear reactions is likely to be started. The energy losses to radiation always overcompensate the gains due to the reactions.”
As we’ve thankfully witnessed after more than 2,000 nuclear detonations, Teller and Konopinski’s conclusion appears to be correct.”
SOURCE:
[https://www.realclearscience.com/blog/2019/09/12/the_fear_that_a_nuclear_bomb_could_ignite_the_atmosphere.html](https://www.realclearscience.com/blog/2019/09/12/the_fear_that_a_nuclear_bomb_could_ignite_the_atmosphere.html)
and there’s this item of Woo Hoo Major Balls Plus info:
“Fermi began offering anyone listening a wager on “whether or not the bomb would ignite the atmosphere, and if so, whether it would merely destroy New Mexico or destroy the world.”
SOURCE:
[https://www.osti.gov/opennet/manhattan-project-history/Events/1945/trinity.htm](https://www.osti.gov/opennet/manhattan-project-history/Events/1945/trinity.htm)
and this link too, for info:
https://www.insidescience.org/manhattan-project-legacy/atmosphere-on-fire
Just imagine all that. THAT GAMBLE.
and **Why**. (They were Sighting on one kind of dude controlling the *show*. )
a Hitler.
Just think. **What would** all of **they** who Did All That – THAT kind of GAMBLE!
To Prevent – a – Hitler – World
**THINK OF**
**THIS 2023 GENERATION**
**ALLOWING A**
**TRUMP**.
to even be……
Let’s say you have a bag of wet sawdust. If it’s only a little wet, you could start burning a small bit of it, which would dry out the next bit of sawdust and allow the whole bag to burn. If it’s really wet, it doesn’t have enough heat to remove water and burn the next bit of sawdust. The atmosphere is basically “too wet” even though there is a lot of potential nuclear binding energy available.
Nuclear reactions sustain themselves if there is enough temperature and density. They looked at the energy made per reaction and figured out the energy lost given the conditions of the atmosphere and determined the nitrogen wouldn’t ignite. The suitability of the atmosphere to a sustained chain reaction producing more fusion energy per volume than dissipated is not changed by just having a bigger/hotter starting point.
Even if you burn some of the sawdust by adding more heat, it won’t spontaneously burn the rest of the sawdust.
I think the key thing is about how dense the ‘fuel’ (the atmosphere) is.
* Assume the atmosphere near the bomb undergoes fusion.
* It will release some extra energy beyond that of what the bomb produced.
* Is that energy enough to fuse at least slightly more air than was just fused?
* It turns out that the air on Earth is sparse enough, that the energy provided by a bit of it fusing, isn’t ennough to fuel an increase amount of air fusing.
* Therefore, there won’t be an endless chain reaction that ~ignites the whole atmosphere.
Here is generally what happened. I wasn’t going to say anything, but there are too many “mostly right” answers mixed with too many overly complicated ones. This is intended to be sufficiently accurate and comprehensible to be proper for this sub.
The first atomic bombs were nuclear fission. This means that they took atoms with large unstable nuclei (centers) and caused those atoms to split apart, releasing energy. Because of the way in which they did this and the atoms being used (U-235 and plutonium were both used), each of these atoms caused two other atoms of the same type to break apart. The result was a “chain reaction”, with each atom triggering two others, each of which triggered two others, and so on, roughly doubling with each breaking nucleus.
The scientists knew how much energy would be released with each splitting. They knew how many atoms of the right type (roughly) that they had in the bomb. So they could readily calculate how much energy would be released. They knew how much pressure this would create, and they knew the temperature that they would generate.
There is another type of nuclear reaction, nuclear fusion. This is what powers the Sun. Insteasd of big atoms breaking up and releasing energy, you crush small atoms together to create energy. In both cases the energy that might be released is related to how far you are from the “middle” element, iron. Breaking big atoms to create atoms closer in size to iron makes energy. Crushing small atoms together to create atoms closer in size to iron makes energy. Going in either direction from iron always uses energy, never releasing it.
To get nuclear fusion, you need enormous pressure and temperature, and the further you get from the lightest element, hydrogen, the more pressure and temperature you need. This is why fusion bombs generally use hydrogen and are thus called hydrogen bombs.
In the atmosphere, there is nowhere near enough hydrogen or helium to create a fusion reaction. However, most of the atmosphere is nitrogen, and this can be used in fusion under enough pressure and temperature.
The temperature and pressure required are enormous, far higher than any bomb ever created comes close to, even if you were to surround the bomb with densely frozen nitrogen. So much higher that the idea that the original “atom bomb” could ignite it was considered by most physicists to be ridiculous.
However, Teller took the idea seriously.
It has been suggested that some of the other physicists considered Teller to be inept at mathematics. I cannot confirm this. However, a quirk in how physicists talk about things versus most people gave him credibility. When asked about the possibility, the physicists said that the chance was virtually zero.
When physicists say that the chance is virtually zero, they mean things like the odds of taking a small pistol and firing it into the air in Oregon, USA, having the bullet be caught by freak winds, the winds carrying that bullet to Africa, and the bullet falling and going through the eye of a specific rhino into its brain and killing it. And, actually, even that isn’t good enough. “Almost zero” in physicist speak means “No way in Hell, ever, are you crazy?” in normal people language.
However, with Teller backing the idea and physicists being almost incapable of saying “impossible”, a study was commissioned that took months to investigate the idea. In the end, the study said it simply would not happen.
Then Enrico Fermi, it has been suggested just to mock Teller, went around trying to make bets with his colleagues on the likelihood of it happening during the first test.
This, unfortunately, firmly embedded in the public consciousness that scientists will risk anything, even the extinction of the human race, in order to do science.
As many have explained, they did calculations. But similar to the fears around LHC creating a black hole and dooming the planet not so long ago, there is one further reason why it is particularly unlikely:
The surrounding cosmos has done way worse than our little nukes. Remember the Chelyabinsk event, a ~10 meter meteorite exploding over Russia in 2013? That cute thing had about 7 to 8 times the explosive yield of the first three nukes (trinity, little boy, fat man) combined.
By meteorite standards, this was a firecracker at best. The legendary dinosaur killer was many **many** times more powerful. If our puny little bombs could set the atmosphere ablaze in nuclear fire, those things would have done so multiple timers over. Or rather every decade.
Same with the aforementioned black holes, each day cosmic rays hit Earth at energies current particle physicists can only dream of.
Imagine if cars didn’t exist, and yet you just built one. You put the spark plugs in the engine and think to yourself. Oh no! what if the explosion travels up through the tubes and into the gas tank, blowing up the whole car? You do a ton of mathematical calculations, and the math says you are fine. But it’s impossible to take everything into account. The only reason we know that cars don’t regularly blow up is that we have many cars in the world and they don’t do that. But in the absence of that data, you can’t be super sure. As the movie says, “theory only takes you so far”
Very ELI5 explanation.
Every atom in existence wants to be iron. Iron is a perfect stable element. (Another ELI5 topic)
If it is lighter than iron, than by fusing elements together you release energy.
If it is heavier than iron, than by breaking it up, you release energy,
When atomic bomb explodes, you use fission (breaking up) of heavy elements such as Uranium and Plutonium, to release large amount of energy.
The fear and hypothesis was, that this release might be so large, it might actually push surrounding air molecules to undergo fusion (joining into heavier elements) releasing more energy, causing more air atoms to fuse and on and on.
This hypothesis has been mostly dismissed because, the energy dissipation is just too fast and the the air is not dense enough or populated by right elements to sustain this reaction.
The way I understand it, causing a chain fusion reaction in an atmosphere cannot really happen. The one exception being, that if you have an explosion large enough to be able to fuse most of the atmosphere on it’s own, than the energy output from fusing the large portions of the atmosphere might give the explosion sufficient kick to fuse the rest. But at that point, there will be not much left of Earth left anyway so …
Less ELI5 but still ELI<12 Reality is, that pushing atoms into fusion is just so damn hard, and the energy of the blast dissipates very quickly. The H-Bomb that is specifically designed to fuse the most fusible material known to man, packs it around the core of nuclear bomb, and still, it is not 100% efficient (Not surprisingly not much information is publicly available, but I have seen estimations between 25%-60%). Showing exactly how hard it is to achieve fusion reaction by design.
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