TL;DR: the atmosphere will never ignite in nuclear fire, but if you add enough deuterium to the oceans you can get runaway fusion in the oceans with an absurdly large nuke.
> a 20 million megaton bomb (which is to say, a bomb with the yield equivalent to 200 teratons of TNT, or a bomb 2 million times more powerful than the Tsar Bomba’s full yield). If we assumed that such a weapon had even a fantastically efficient yield-to-weight ratio like 50 kt/kg, that’s still a device that would weigh around a billion metric tons
I've saved those two comments, because I found them to productive to this discussion. I see that their first comment contains "ethnic slur" (though not an ethnic slur), so that might be what caused the mistake?
Twenty times the total amount of deuterium currently present in the world's oceans.
Basically, you'd have to completely change the chemistry of the oceans on a global scale.
Also, AFAIK there is no realistic way to synthesize deuterium artificially (please let me know if I'm wrong!) so to get started you'd need to go out and find something like an order of magnitude more deuterium than exists on planet Earth. You'd have to scour a big chunk of the solar system.
So, not something an apocalyptic cult is going to pull off in the forseable future.
Well, based on another comment in this thread [0], after the ocean's concentration of nuclear fuel is covered, maybe about 2 million Tsar Bomba's would do the trick.
The physical dimensions of the Tsar Bomba are on the wikipedia page:
If 2 million are needed, then that's 100 cubed, twice. So two cubes of this bomb, with each cube measuring 100 units per edge, filled solid. The bomb is already designed, so producing 2 million of them would be a matter of setting up an assembly line, and churnning them out like automobiles, once the raw materials are procured.
Each one is about the size of a car, so a parking garage that holds 2 million cars is an okay frame of reference. Most stadiums have parking lots that hold 10,000 spaces, so 100 stadiums, across one hundred cities, but all together in one place. Realistically, though, two million cars easily fit inside any large city.
As for the gaseous concentration of fusion gas in the ocean, that's a much tougher problem to tackle. Really, because the huge fusion bombs that use deuterium (and tritium) are sourcing that material from the oceans (or other bodies of water). Culling deuterium from natural water sources is among the easier ways to produce weaponizable amounts of the gas. So, in order to create twenty times the natural standing concentration would require synthesizing your own new, man-made deuterium from the normal variety of hydrogen, by irradiating non-heavy water.
For every million gallons of ocean water, you can pull out maybe 156 gallons of heavy water, so you'd get about six hundred trillion gallons of heavy water, if you could capture all of the natural heavy water in the world. Take 600 trillion gallons, and multiply it by twenty. Bingo, you're there. That's the ignitable concentration, if you had 2 million Tsar Bombas.
I have a hunch - mathematically unverified - that yield wouldn't increase linearly with volume. And you might have to build your stadiums underwater, because a surface explosion would be unlikely to create the energy density.
Also, it's not obvious there's enough uranium in the world for that many fission devices.
If you want to kill everyone with nuclear weapons, there are easier ways to do it:
This wouldn't scour all life from the earth, but enthusiastic use of cobalt salt weapons would probably put life back to the plant and mutant insect stage.
From Hamming's paper Mathematics on a Distant Planet (1998):
...before going farther I need to mention a few things in my life that have shaped my opinions. The first occurred at Los Alamos during WWII when we were designing atomic bombs. Shortly before the first field test (you realize that no small scale experiment can be done - either you have a critical mass or you do not), a man asked me to check some arithmetic he had done, and I agreed, thinking to fob it off on some subordinate. When I asked what it was, he said, "It is the probability that the test bomb will ignite the whole atmosphere." I decided I would check it myself! The next day when he came for the answers I remarked to him, "The arithmetic was apparently correct but I do not know about the formulas for the capture cross sections for oxygen and nitrogen-after all, there could be no experiments at the needed energy levels." He replied, like a physicist talking to a mathematician, that he wanted me to check the arithmetic not the physics, and left. I said to myself, "What have you done, Hamming, you are involved in risking all of life that is known in the Universe, and you do not know much of an essential part?" I was pacing up and down the corridor when a friend asked me what was
bothering me. I told him. His reply was, "Never mind, Hamming, no one will ever blame you." Yes, we risked all the life we knew of in the known universe on some
mathematics. Mathematics is not merely an idle art form, it is an essential part of our society.
Maybe Hamming didn't "know about the formulas for the capture cross sections for oxygen and nitrogen". But "after all, there could be no experiments at the needed energy levels" seems like a valid point.
However, perhaps "knowing" physics includes coming up with likely values for currently unmeasurable parameters.
> I was pacing up and down the corridor when a friend asked me what was bothering me. I told him. His reply was, "Never mind, Hamming, no one will ever blame you."
Right. If there was any blaming to be done, nobody left alive would know what Hamming's role had been.
> The answer they found: if the Earth’s oceans had twenty times more deuterium than they actually contain, they could be ignited by a 20 million megaton bomb (which is to say, a bomb with the yield equivalent to 200 teratons of TNT, or a bomb 2 million times more powerful than the Tsar Bomba’s full yield).
A factor of twenty in the elemental composition of hydrogen, and a factor of a million in the fission efficiency of uranium. We’ve been lucky with regard to untested physical constants so far, but there’s no promise that that will hold going forward!
Humans are comparing notes with a new alien species, and find a huge discrepancy in one of the physical constants. It turns out that scientists had published a fake value, because the information would've allowed anyone to build a superweapon.
Initially I assumed this was going to be about how nuclear tests were 'self-declassifying' since all the bomb components, test fixtures and equipment, the tower it was mounted on etc. would be completely vaporized in the explosion, so there was nothing left to classify as secret. Except for that one embarassing time when the UCRL device in test Upshot-Knothole Ruth[0] fizzled and failed to destroy the steel tower it was detonated on...
24 comments
[ 3.2 ms ] story [ 16.2 ms ] threadhttps://news.ycombinator.com/item?id=18012339
Basically, you'd have to completely change the chemistry of the oceans on a global scale.
Also, AFAIK there is no realistic way to synthesize deuterium artificially (please let me know if I'm wrong!) so to get started you'd need to go out and find something like an order of magnitude more deuterium than exists on planet Earth. You'd have to scour a big chunk of the solar system.
So, not something an apocalyptic cult is going to pull off in the forseable future.
https://en.wikipedia.org/wiki/Heavy_water#Production
We're working on it... Not with this particular additive, but we're definitely doing that, so it's possible.
The physical dimensions of the Tsar Bomba are on the wikipedia page:
https://en.wikipedia.org/wiki/Tsar_Bomba
If 2 million are needed, then that's 100 cubed, twice. So two cubes of this bomb, with each cube measuring 100 units per edge, filled solid. The bomb is already designed, so producing 2 million of them would be a matter of setting up an assembly line, and churnning them out like automobiles, once the raw materials are procured.
Each one is about the size of a car, so a parking garage that holds 2 million cars is an okay frame of reference. Most stadiums have parking lots that hold 10,000 spaces, so 100 stadiums, across one hundred cities, but all together in one place. Realistically, though, two million cars easily fit inside any large city.
As for the gaseous concentration of fusion gas in the ocean, that's a much tougher problem to tackle. Really, because the huge fusion bombs that use deuterium (and tritium) are sourcing that material from the oceans (or other bodies of water). Culling deuterium from natural water sources is among the easier ways to produce weaponizable amounts of the gas. So, in order to create twenty times the natural standing concentration would require synthesizing your own new, man-made deuterium from the normal variety of hydrogen, by irradiating non-heavy water.
For every million gallons of ocean water, you can pull out maybe 156 gallons of heavy water, so you'd get about six hundred trillion gallons of heavy water, if you could capture all of the natural heavy water in the world. Take 600 trillion gallons, and multiply it by twenty. Bingo, you're there. That's the ignitable concentration, if you had 2 million Tsar Bombas.
[0] https://news.ycombinator.com/item?id=18011959
Also, it's not obvious there's enough uranium in the world for that many fission devices.
If you want to kill everyone with nuclear weapons, there are easier ways to do it:
https://en.wikipedia.org/wiki/Cobalt_bomb
This wouldn't scour all life from the earth, but enthusiastic use of cobalt salt weapons would probably put life back to the plant and mutant insect stage.
...before going farther I need to mention a few things in my life that have shaped my opinions. The first occurred at Los Alamos during WWII when we were designing atomic bombs. Shortly before the first field test (you realize that no small scale experiment can be done - either you have a critical mass or you do not), a man asked me to check some arithmetic he had done, and I agreed, thinking to fob it off on some subordinate. When I asked what it was, he said, "It is the probability that the test bomb will ignite the whole atmosphere." I decided I would check it myself! The next day when he came for the answers I remarked to him, "The arithmetic was apparently correct but I do not know about the formulas for the capture cross sections for oxygen and nitrogen-after all, there could be no experiments at the needed energy levels." He replied, like a physicist talking to a mathematician, that he wanted me to check the arithmetic not the physics, and left. I said to myself, "What have you done, Hamming, you are involved in risking all of life that is known in the Universe, and you do not know much of an essential part?" I was pacing up and down the corridor when a friend asked me what was bothering me. I told him. His reply was, "Never mind, Hamming, no one will ever blame you." Yes, we risked all the life we knew of in the known universe on some mathematics. Mathematics is not merely an idle art form, it is an essential part of our society.
http://libgen.io/scimag/get.php?doi=10.2307/2589247&download...
That had to have been Teller.
However, perhaps "knowing" physics includes coming up with likely values for currently unmeasurable parameters.
> I was pacing up and down the corridor when a friend asked me what was bothering me. I told him. His reply was, "Never mind, Hamming, no one will ever blame you."
Right. If there was any blaming to be done, nobody left alive would know what Hamming's role had been.
A factor of twenty in the elemental composition of hydrogen, and a factor of a million in the fission efficiency of uranium. We’ve been lucky with regard to untested physical constants so far, but there’s no promise that that will hold going forward!
https://www.lesswrong.com/posts/HawFh7RvDM4RyoJ2d/three-worl...
Humans are comparing notes with a new alien species, and find a huge discrepancy in one of the physical constants. It turns out that scientists had published a fake value, because the information would've allowed anyone to build a superweapon.
1: https://en.wikipedia.org/wiki/Tsar_Bomba
0. https://en.wikipedia.org/wiki/Operation_Upshot%E2%80%93Knoth...