If you want to assert a truth, first make sure it's not just an opinion that you desperately want to be true.

If aliens did visit us, I'd be embarrassed to tell them we still dig fossil fuels from the ground as a source of energy.

There are no wild, seedless watermelons. There's no wild cows... You list all the fruit, and all the vegetables, and ask yourself, is there a wild counterpart to this? If there is, it's not as large, it's not as sweet, it's not as juicy, and it has way more seeds in it. We have systematically genetically modified all the foods, the vegetables and animals that we have eaten ever since we cultivated them. It's called artificial selection.

If we have the power to turn another planet into Earth, then we have the power to turn Earth back into Earth.

In science, if you don't do it, somebody else will. Whereas in art, if Beethoven didn't compose the 'Ninth Symphony,' no one else before or after is going to compose the 'Ninth Symphony' that he composed; no one else is going to paint 'Starry Night' by van Gogh.

I have a multivolume history of the world from the 19th century that begins with Noah's flood as though it's as historical a fact as the rise and fall of Rome.

Where there's water on Earth, you find life as we know it. So if you find water somewhere else, it becomes a remarkable draw to look closer to see if life of any kind is there, even if it's bacterial, which would be extraordinary for the field of biology.