Why universe is so perfectly made for us?

Question

I am very eager to learn that, "Why universe is so perfectly made for us?" Or our universe is just stable by chance?

Answer 1

This is related to the fine tuning argument. I like to turn this upside down in a way. What would be surprising is to find we exist in a universe or cosmology that renders life virtually impossible. That in effect would be far more remarkable than any observation on how we are well fitted for the character of the observable universe.

I will not go into this in any detail but the de Sitter vacuum or spacetime is not perfectly stable. Quantum gravitation with string theory works well with anti-de Sitter spacetimes that have negative vacuum energy. String/M-theory does not like de Sitter spacetimes with positive vacuum energy. Remember the bosonic string or type I has a negative ground state. The observable spacetime is approximately de Sitter to within $10^{-5}$ in anisotropy, and has been since dark energy dominance. Our de Sitter world is then maybe some sort of freak or something generated out of an anti-de Sitter spacetime. Cumrun Vafa has coined the term "swampland" to describe this situation, where cosmologies may exist that have quantum fields inconsistent with gravity.