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Comment by galaxyLogic | Hacker News Reader

> no earthquakes No but how about moon-quakes? Ok, not geologically active you say. But moon's been bombarded by asteroids it's surface is full of craters. Creating a crater wouldn't that be an equivalent of a moon-quake?

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This is the correct answer. These lava tubes are, at their youngest, a couple billion years old. Since then, the moon has been thwacked very hard and -- on those timescales -- often. If the tubes haven't collapsed yet, then there's a high likelihood that they're exceptionally stable.

That could be survivor bias. Maybe there used to be a lot more of them.

Wouldn't a collapsed tube be very distinctive visually?

Very much so -- and one has even been explored by humans!

https://en.wikipedia.org/wiki/Hadley%E2%80%93Apennine

Yes survivor bias. But since these survived, they are likely to be structurally sound. Like antique furniture or structures on Earth.

Does that count as natural selection?

I don't think lava tubes breed.

Survival of the fittest, then.

You're not accounting for tidal forces. The same forces that create the tides on Earth also affect the moon. In this case via moon-quakes.

https://phys.org/news/2017-08-moon-tidal-stress-responsible-...

But the moon is one-face, so tidal stress should be constant.

What about the sun's? If the force is strong enough to make earth orbit, and moon-to-sun distance oscillates, plus seasonal behaviour, there must be quite some straining tides...

oh yeah, that makes sense. It's a tiny fraction of the moon-sun distance, but it would have some efrect. Is it a "tidal" force, though?

The sun also creates the tides.

You are absolutely correct.

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