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I like that there was no way even to guess that this coincidence occurred until we became able to scan Venus with radar. Visually, all faces of Venus are indistinguishable.

I wonder whether we have the moon to thank for Earth having retained a short day, and the short day for our magnetic field. Big moons of inner terrestrial planets must be vanishingly rare in the galaxy. If terrestrial planets with magnetic fields are uniquely suited to breed up complex life, that might by itself account for the Fermi paradox.

But I don't know how to evaluate the notion that our gross moon has protected Earth from the near tidal locking Mercury and Venus suffer.


What is it that would make big moons of terrestrial inner planets vanishingly rare?

And how likely is it that a planet without a large moon would fail to retain a short day? Mars has a day of similar length to that of Earth (though no magnetic field worth speaking of...).

That gets weird when you look up the ancient history of moon as a god and a time before when there was no moon and how it relates to chaos.
Ancients also thought solar eclipses were bad omens yet they happen on a predictable basis.

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