Gravity is probably the big one as it is the hardest to approximate in space, but we're likely dependent on a lot of stuff that exists on Earth. We evolved to l

Gravity is probably the big one as it is the hardest to approximate in space, but we're likely dependent on a lot of stuff that exists on Earth. We evolved to live on Earth. Earth may not be particularly suited for life, but what we consider life may be particularly suited for Earth.