[Freedom_Is_Not_Free]

Why couldn’t the moon and earth have been formed simultaneously? What is the physical evidence this can’t be possible?

[James C. Bennett]

I think orbital mechanics settles that issue.

[Pontiac]

Why couldn’t the moon and earth have been formed simultaneously? What is the physical evidence this can’t be possible?

The mentioned isotopic ratios of elements being nearly identical suggest that the earth and the moon are originally the same body.

If they had formed independently they would have different isotopic ratios because they would have formed of different stuff.

[ntmxx]

To some extent, you are correct. There is a theory that postulates the moon is a spin-off of Earth, during a period when the two masses were about where the Earth is now, caused by centrifugal force, as they cooled, the smaller mass was thrown off and held a geo-synchronous orbit which balances Earth in its location.