The bottom line is that time travel is allowed by the laws of physics.

But, as Einstein once said, “For we convinced physicists, the distinction between past, present, and future is only an illusion, however persistent.”5

My best teachers were not the ones who knew all the answers, but those who were deeply excited by questions they couldn't answer.

I can't stand clutter. I can't stand piles of stuff. And whenever I see it, I basically just throw the stuff away.

One of the wonders of science is that it is completely universal. It crosses national boundaries with total ease.

For me it's been very exciting to contribute to the public's understanding of how rich and wondrous science is.

In the far, far future, essentially all matter will have returned to energy. But because of the enormous expansion of space, this energy will be spread so thinly that it will hardly ever convert back to even the lightest particles of matter. Instead, a faint mist of light will fall for eternity through an ever colder and quieter cosmos.