Neil deGrasse Tyson

Carl Sagan spoke fluently between biology and geology and astrophysics and physics. If you move fluently across those boundaries, you realize that science is everywhere; science is not something you can step around or sweep under the rug.

Those who see the cosmic perspective as a depressing outlook, they really need to reassess how they think about the world. Because when I look up in the universe, I know I'm small but I'm also big. I'm big because I'm connected to the universe, and the universe is connected to me.

Supplying fuel for a Mars expedition from the lunar surface is often suggested, but it's hard to make it pay off - Moon bases are expensive, and just buying more rockets to launch fuel from Earth is relatively cheap.