Nuclear weapons do not work as described in The Dark Forest
It's a point of physics in The Dark Forest that bothers me because it is one of the real world touchpoints of physics in the series. The weapons are described as "burning" and that the fire ball was somehow directly part of the fusion process / that the nuclear weapons they'd create would explode for minutes at a time. That's not how nuclear weapons work at all.
Nuclear reaction only happens at insane temperatures and pressures that exist for fractions of a second before the whole device starts exploding outward and critical conditions disappear. Everything you're seeing after that initial flash is just the after effects of the nuclear reaction dumping an absolute fuck ton of energy into the atmosphere, not ongoing nuclear chain reactions.
Another point is that most of the material in a nuclear weapon doesn't undergo fusion or fission. Regarding the Hiroshima bomb:
Regarding Fusion weapons:
[So it takes 327kg of hydrogen to produce 50MT of energy by using a thermonuclear reaction ( Proton-Proton chain).
Of that 327kg, only 0.712% or 2.33kg is converted to energy.](https://physics.stackexchange.com/questions/135013/hydrogen-bomb-mass-to-energy)
The scientists would do better to figure out a way to convert more of the mass to energy in smaller bombs than create "building sized" nuclear weapons.
That's all, had to get that off my chest. I love the series and the hypothetical physics otherwise, it's just that point is understood physics.
Posted May 27, 2023, 8:22 PM UTC
What's the exact quote on these descriptions?
Highly inaccurate description of how nuclear weapons work. It might have a fireball for 20 seconds, but 19.999 seconds earlier everything fusible would have rapidly left the critical region.
Edit: Here's how nuclear weapons work. No combustion people....
Fission devices:
A. If in a vacuum / space, all of this energy remains electromagnetic energy. You get an incredibly bright flash that will blow out exposures on cameras to make it look big See here, but is actually remarkably small in size. It's a effectively a sun in low earth orbit... You'd get a little bit of a nebula from the material from the remaining materials from the nuclear weapon. Very little of the actual fusible or fissile material ends up being turned into energy.
OR
B. In an atmosphere, the energy gets dumped into the surrounding atmosphere and it's the transmission of this energy into the matter surrounding the nuclear weapon that causes the massive blast.
A fusion weapon works by
Both of these processes happen within microseconds and are far more cool than Cixin's bad description. Like I said, I like the books, but the description is just wrong.
So your beef is that there is a ball of fire that exists for 20 seconds, but you don't want anyone to think that the ball of fire that exists for 20 seconds is combusting actively for 20 seconds?
The description that it's the fireball that's "combusting" that's the issue. The only thing that's burning is shit in the atmosphere.
Kinda seems like splitting hairs, but as a hair splitter myself, I get it.
Ok, I can see your point, but it does have a "fireball" that lasts for 20 seconds. So are you splitting hairs? Or just trying to explain nuclear weapons to the sub? No sarcasm, honest question.
Literally said it in the description...
And fireballs do not happen in space.
From NASA:
If a nuclear weapon is exploded in a vacuum-i. e., in space-the complexion of weapon effects changes drastically:
First, in the absence of an atmosphere, blast disappears completely. - The important one, no blast, no fireball.
Second, thermal radiation, as usually defined, also disappears. There is no longer any air for the blast wave to heat and much higher frequency radiation is emitted from the weapon itself.
Third, in the absence of the atmosphere,** nuclear radiation will suffer no physical attenuation and the only degradation in intensity will arise from reduction with distance.** As a result the range of significant dosages will be many times greater than is the case at sea level.
Yeah don't they specifically mention how useless nuclear weapons are in space for this exact reason?
The fireball he is referring to is not the detonation itself, but the hot and luminous spherical mass of air and gaseous weapon residues that forms after the detonation. You can use this calculator put together by MIT to calc the size and duration of the fireball. It’s real.
However the timing the author gives seems an order of magnitude higher than reality 🤔
I had to come back to this because here's a nuclear physicist describing what happens with nukes in space. I was correct about what happens with nuclear weapons in space.
Bright flash, then nothing. All that shit you see comes from nukes in atmosphere.
No, they literally say the above. It is not a combustion. Nuclear material isn't burning in the fire ball. The actual nuclear portion happens in microseconds.
And that'd be (the MIT link) for an explosion in atmosphere, there's no fire ball in space where these explosions would be taking place in the story. The fire ball comes from everything in the atmosphere being super heated, something deeply lacking in deep space.
Edit: Fire balls are not a process of nuclear bombs exploding, they're the results of. You can explode nuclear bombs and get zero fireball as noted above.
From NASA:
If a nuclear weapon is exploded in a vacuum-i. e., in space-the complexion of weapon effects changes drastically:
First, in the absence of an atmosphere, blast disappears completely.
Second, thermal radiation, as usually defined, also disappears. There is no longer any air for the blast wave to heat and much higher frequency radiation is emitted from the weapon itself.
Third, in the absence of the atmosphere,** nuclear radiation will suffer no physical attenuation and the only degradation in intensity will arise from reduction with distance.** As a result the range of significant dosages will be many times greater than is the case at sea level.
Edit: The guy you all upvoted has no clue what he's talking about. How can I prove this?
In research that NASA states:
In regards to point 3 he responded:
They either didn't bother to read the research or fundamentally didn't understand it.
They are speaking gibberish. But please, someone go on and explain how what he said has anything to do with what's said on this page.
His case is not making the case that the process of nuclear fission is like burning, he is saying that the a nuclear bomb’s explosion is like burning. There is a fireball that persists in time which is separate from the detonation. The process is slow, like burning. The times he gives are basically correct. He is making the point that these bombs will look like actual stars for a minute.
That you would simultaneously read this far into something but in the wrong direction is astounding to me