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

No matter how hard you try to teach your cat general relativity, you're going to fail.

Science is very good at answering the 'how' questions. 'How did the universe evolve to the form that we see?' But it is woefully inadequate in addressing the 'why' questions. 'Why is there a universe at all?' These are the meaning questions, which many people think religion is particularly good at dealing with.

Nature's patterns sometimes reflect two intertwined features: fundamental physical laws and environmental influences. It's nature's version of nature versus nurture.

A watch worn by a particle of light would not tick at all. Light realizes the dreams of Ponce de Leon and the cosmetics industry: it doesn't age.

The universe is incredibly wondrous, incredibly beautiful, and it fills me with a sense that there is some underlying explanation that we have yet to fully understand. If someone wants to place the word 'God' on those collections of words, it's OK with me.

I like to think that Einstein would look at string theory’s journey and smile, enjoying the theory’s remarkable geometrical features while feeling kinship with fellow travelers on the long and winding road toward unification.