What would the gravitational effects of the moon play on life four hundred million years ago?
The moon would have been slightly closer to the Earth 400 million years ago than it is now, but the difference in the gravitational effect would have been pretty negligible from the effect it currently has. Four hundred million years ago would have been right around the time animals were just beginning to leave the oceans and colonize land. As you can imagine, tides would have a major impact on these organisms. High tides back then would have been slightly higher, and low tides slightly lower, but local geography would have had more effect than the actual gravity. Bays and shallows channel the water movement and create greater variation than the moon’s gravity does. Today, places like the Bay of Fundy have tides that vary by 70 feet or more, while other sites may only change a few feet. Tides might have been a few inches higher and lower back then, but local geography would have a greater effect. The main influence the moon would have had would have already taken place. By stabilizing
