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There is a third option besides tidal lock and night/day cycle.

Some moons in the outer Solar System have Chaotic Rotation[1]. These bodies don't have a fixed rotation axis or period.

There could still be such a Moon orbiting a planet in the habitable zone, or even a small planet in a belt like structure orbiting close to a red dwarf.

I wonder what lifeforms could evolve when the amount of light/energy received is unpredictable and varies constantly?

[1] https://en.wikipedia.org/wiki/Chaotic_rotation

Chaotic rotation occurs primarily in bodies that are not spherical. These tend to be smaller, because gravity forces larger bodies into spheres, and would have a thinner atmosphere if any due to the small gravity.

Not saying life is impossible on such a moon, but it would be even weirder than just strange day night suggests.

But wont millions of years of chaotic rotation cause a large body to become round?

Thousands of years this sounds realistic, but remember the scale of things is in billions of years.

I believe the chaotic rotation would stop as soon as the body became round, to conserve angular momentum.

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