I would have thought that a planet's life form, shape and variety would be determined by:
1- the energy output of nearest star
2- the planet's gravity
He barely mentions gravity which is surprising. Earthlings probably wouldn't be as tall with 1.3x more gravity. Maybe life wouldn't even have made it out of water, or much more slowly.
Evolution would mean "heavier" eggs would be harder to carry. The entire evolution process hangs around reproduction so what would that mean?
Same for less gravity - except it would _probably_ be on a smaller planet. Gravity correlates with planet size in the solar system. Would <0.8G be enough to retain water, atmosphere, etc?
Somehow I'm not surprised to find out one day that an intelligent alien life would look a lot like us, on a planet that looks a lot like Earth.
I would have thought that a planet's life form, shape and variety would be determined by:
1- the energy output of nearest star
2- the planet's gravity
He barely mentions gravity which is surprising. Earthlings probably wouldn't be as tall with 1.3x more gravity. Maybe life wouldn't even have made it out of water, or much more slowly.
Evolution would mean "heavier" eggs would be harder to carry. The entire evolution process hangs around reproduction so what would that mean?
Same for less gravity - except it would _probably_ be on a smaller planet. Gravity correlates with planet size in the solar system. Would <0.8G be enough to retain water, atmosphere, etc?
Somehow I'm not surprised to find out one day that an intelligent alien life would look a lot like us, on a planet that looks a lot like Earth.