We didn't go to the moon to explore or because it was in our DNA or because we're Americans. We went because we were at war and we felt a threat.

To assert that the universe has a purpose implies the universe has intent. And intent implies a desired outcome. But who would do the desiring? And what would a desired outcome be? That carbon-based life is inevitable? Or that sentient primates are life's neurological pinnacle? Are answers to these questions even possible without expressing a profound bias of human sentiment? Of course humans were not around to ask these questions for 99.9999% of cosmic history. So if the purpose of the universe was to create humans then the cosmos was embarrassingly inefficient about it.

The remarkable feature of physical laws is that they apply everywhere, whether or not you choose to believe in them. After the laws of physics, everything else is opinion.

Anyone who has wrestled knows that it's the hardest thing in the world to do. Anyone who says something else is the hardest thing has never wrestled. That's what I have found. ... You don't wrestle because it's easy, you wrestle because it's hard. I don't do astrophysics because it's easy, I do it because it's hard. And I juxtapose the two in my mind, body, and soul all the time.

The school system is constructed to praise you if you get high grades. And if you get straight A's, you're the one that everyone puts forward, and they prognosticate that the straight-A person is the one most likely to succeed, because that's the way the school system is constructed and conceived.

To achieve this density of a neutron star at home, just cram a herd of 50 million elephants into the volume of a thimble.

Our entire universe emerged from a point smaller than a single atom. Space itself exploded in a cosmic fire, launching the expansion of the universe and giving birth to all the energy and all the matter we know today. I know that sounds crazy, but there’s strong observational evidence to support the Big Bang theory. And it includes the amount of helium in the cosmos and the glow of radio waves left over from the explosion.