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Comment by cousin_it | Hacker News Reader

Surely the easiest way to make money on the Moon is by threatening kinetic bombardment of Earth?

Seems very unlikely that for the foreseeable future, any Moon->Earth threat of kinetic bombardment could stand against an Earth->Moon threat of nukes and cutting off supplies. There is a fundamental asymmetry in that rendering Earth completely uninhabitable to humans would almost amount to terraforming a planet, whereas a Moon colony is rendered uninhabitable by, among other approaches, making a small number of strategically-placed holes in buildings.

I saw Dr Strangelove, certainly anyone who plans to (seriously) threaten the Earth with moon-launched WMDs would include some kind of dead man's switch in their plan.

What I think is this: so the UN (of Earth) acquiesce to your demand for a trillion dollars and mining rights to Ganymede. What next? It's not like you can go back to Earth and enjoy your new wealth.

Which is most vulnerable. Planet Earth or a small bubble of air on the Moon?

Earth is a bigger target, in terms of both mass and size, compared to the Moon and especially compared to a small bubble of air thereon. So almost any weapons would need to be far more precise against a lunar colony than against Earth.

* * * * *

If we were talking about nukes, things would of course get far more interesting.

Nukes aimed at Earth would only have to detonate somewhere in the atmosphere, if there were enough of them.

By contrast, nukes aimed at this lunar air bubble would have to hit the bubble precisely; lacking a direct hit or an ambient atmosphere, nukes only produce radiation, blinding light ... and seismic activity if they detonate somewhere on the Moon's surface. No aerial shockwave, no convection, much less fallout, no climate changes.

Also, since Earth has greater mass, Earthbound projectiles would need less energy to escape the Moon and deorbit to Earth's atmosphere, compared to the energy that Moonbound projectiles would need to escape Earth and deorbit onto the Moon's surface.

If only we had developed the technology to target weapons precisely, or something like a warhead that breaks up into millions of fragments to hit a large area. Or if nuclear weapons emitted thermal radiation across a large area. Oh well. I suppose the Moon wins.

Earth. They're ("we're") at the bottom of a steeper gravity well.

https://en.wikipedia.org/wiki/The_Moon_Is_a_Harsh_Mistress

If you do the orbital math you realize there's no advantage to putting weapons on the moon.

If there was, 50 years after we acquired the capability to get there it would probably be bristling with fortresses.

I don't think there is any benefit to moon-based weapons that space-based weapons don't already have, and we already have ICBMs and FOBSs.

Tanstaafl

For those confused about the relevance of fegu's comment. That acronym was popularized by Robert Heinlein's "The Moon is a Harsh Mistress", which includes kinetic bombardment of Earth by lunar inhabitants as a plot point.

Your comment was opaque, but was the first thing I thought of too

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