"New results in biology indicate that the #SciFi idea of the multi-generational starship, which is already the only realistic way for humans to cross interstellar distances, will not work, because any closed biological life-support system will be too small to function over the centuries required.
[…]
So at this point, it’s important to point out that the idea of humanity going to the stars is a fantasy and is not going to happen."
#KimStanleyRobinson interview: https://www.terrain.org/2016/interviews/kim-stanley-robinson/