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  • What would happen if we were to detonate a very very powerful nuclear weapon on the moon?

  • Would the explosion knock its orbit towards earth, causing tidal waves and misery? Could

  • the moon be destroyed, showering the earth in a rain of meteoric death?

  • During the cold war the moon was a major target for space exploration and you know, military

  • bases. So the US Air Force commissioned a serious study into the effects of a nuclear

  • detonation on the surface of the moon. But just quoting stuff is boring, so let's conduct

  • a very important scientific experiment with an imaginary 100 megaton thermonuclear warhead,

  • about twice as powerful as the most powerful bomb ever detonated. We'll also place a

  • number of curious astronauts around the moon as observers.

  • Let's push the button and slow down time. For the first few milliseconds nothing much

  • happens outside our weapon. Meanwhile inside, high explosives send a shockwave to a radioactive

  • metal core, compressing it so much that it reaches criticality and starts a nuclear fission

  • chain reaction. The 100 million degree plasma created in this first stage sets off the second

  • stage, with atomic nuclei fusing like they do in the core of a star. Very briefly, our

  • weapon contains one of the hottest places in the universe. And only now, barely ten

  • milliseconds later, does the rest of the universe find out that anything has happened, as suddenly

  • the bomb dissolves and a flaming star of nuclear death is born.

  • So far so good. But everything that happens now is very different from what we're used

  • to on earth because of one major difference: There's no atmosphere.

  • As the fireball shines it releases a flash of X-rays and thermal photons, a wave of silent

  • heat which rushes outwards in all directions. On earth, this heat would char and burn everything

  • within a 50 kilometer radius at least. But on the moon, without an atmosphere and oxygen-rich

  • air, there's no burning at all. Also there are no things to burn. The crunchy topsoil

  • of the moon is made from silicate rock and metals chewed to dust by eons of meteorite

  • impacts, mixed with tiny traces of water. When heated by the explosion, X-rays from

  • the fireball vaporize a thin cloud of rock from the lunar surface, while the unlucky

  • dust that's inside the fireball melts into glass. Any astronauts watching the show within

  • about 50 km can expect to be fried.

  • And now, we begin to see one of the biggest differences between explosions in space and

  • on earth. On earth the atmosphere fights back against the plasma bubble: Its expansion is

  • violently stopped within moments by the pressure of the atmosphere. But this is not good news.

  • As the fireball rams the atmosphere it produces the most destructive part of a nuclear explosion

  • on earth: the shockwave. Compressed air around the explosion rushes out faster than the speed

  • of sound, shattering buildings and roaring so loud it ruptures organs. But on the moon

  • there is no shockwave. No atmosphere means nothing to impede the expanding explosion

  • in space. On the moon, the fireball just grows in eerie silence as there is no atmosphere

  • to stop it or to give it a voice.

  • This would be an amazing thing to watch from a safe distance. Unfortunately there's hardly

  • any safe viewing distance for a nuclear explosion on the moon. Without an atmosphere weakening

  • the deadly ionizing radiation that can scramble DNA, anyone close enough to get a good look

  • will be exposed to fatal amounts of radiation. But of course, that's not all.

  • While all of this happens the explosion hammers against the moon, transferring about a tenth

  • of the explosion energy into seismic waves, powering an intense moonquake. The moon is

  • much smaller than the earth, and our astronauts will feel an inescapable violent shaking no

  • matter where they're standing. Compared to an earthquake of 7 on the Richter scale,

  • this shaking could seriously damage or even level infrastructure we might have built anywhere

  • on the moon. Those who hid on the far side of the moon would have no idea it was an explosion,

  • the quaking would feel like an asteroid the size of the Great Pyramid had struck.

  • And it's not over yet: Where our bomb explodes, the ground splatters like water when a rock

  • strikes a pond. As the explosion pushes against the surface it may excavate as much as a hundred

  • million cubic meters of dust and rock, forming a crater a kilometer across while bedrock

  • is pulverized to rubble. Debris is shot into the sky in every direction.

  • Again without an atmosphere there's no drag to slow any of it down. Much of the debris

  • scattered never returns to the moon, flying off faster than escape velocity. A flurry

  • of micrometeorites have been cast off to explore the solar system, many of which will rain

  • down on the earth, though few will be larger than pebbles. Any satellite, astronaut or

  • space station in the way though will have a really bad time.

  • Micrometeorites are launched at many speeds and angles, allowing them to spread all over

  • the surface of the moon. Like bullets they'll punch through our curious astronauts no matter

  • where they stand.

  • Finally, our explosion comes to an end. On earth, the fireball rises like a hot air balloon

  • forming a sort of stalk; as it reaches up cooler air is drawn in around it, rounding

  • the top into a mushroom cloud. But on the moon, well, you know by now: no atmosphere,

  • no mushroom. The larger the plasma gets, the cooler it becomes, and the less energy it

  • has to make interesting or terrifying things happen. Within seconds of pulling the trigger,

  • the bubble reddens and fades from view. It would be visible from the earth, like a star

  • flickering to life only to fade out right away. A spark, and then nothing. As the cloud

  • of tiny debris reaches far above the surface of the moon, it's illuminated by the sun

  • for a few minutes giving it an eerie beauty for anyone left to observe the spectacle.

  • What about the moon's orbit? It is basically unchanged. Trying to move the moon with a

  • nuke is like trying to move a truck by blowing on it. Nuclear explosions may be big, but

  • space is bigger. Our mighty explosion just leaves another crater. One among millions.

  • Still, anyone on the moon will continue to not enjoy themselves. The material that ends

  • up raining back to the moon is radioactive, and without any natural processes to wash

  • it away or bury it, the surface of the moon will remain contaminated. Although fortunately,

  • the worst of the radiation will have decayed to a level comparable to natural levels from

  • cosmic rays in about a year.

  • In conclusion we can say with confidence that while the moon itself does not care about

  • being nuked and will barely notice, using the moon as a nuclear test ground kind of

  • ruins it for everyone trying to spend some time there or to build something useful. So

  • maybe we should just not do that.

What would happen if we were to detonate a very very powerful nuclear weapon on the moon?

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What if We Nuke the Moon?

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    OolongCha に公開 2021 年 06 月 30 日
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