I like to engage the public because when I was in high school, I had all these questions about anti-matter, higher dimensions and time travel. Every time I went to the library, every time I asked people these questions, I would get some strange looks. Nobody could answer any of these questions.

I distracted myself from the fear and terrorism by thinking about things like how the universe began and whether time travel is possible.

Time travel is such a magic concept.

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

People who think about time travel stories sometimes think that going back in time would be fun because you would have all the information you needed to be much more astute than the people there, when the truth is of course you wouldn't.

The way that people feel changes everything. Feelings are forces. They cause us to time travel. And to leave ourselves, to leave our bodies. I would be that kind of psychologist who says, 'You're absolutely right - there are monsters under the bed.'

I myself believe that there will one day be time travel because when we find that something isn't forbidden by the over-arching laws of physics we usually eventually find a technological way of doing it.

I mean, the first 'Back to the Future' is kind of a perfect script, I think, in terms of handling time travel the best. It depends on your definition. To me, that means it effectively uses it in the story.

Time travel was once considered scientific heresy, and I used to avoid talking about it for fear of being labelled a 'crank.'

Look at anyone's bookcase at home, no matter how modest, and you're going to find a book that contains wisdom or ideas or a language that's at least a thousand years old. And the idea that humans have created a mechanism to time travel, to hurl ideas into the future, it sort of bookends. Books are a time machine.

Even if it turns out that time travel is impossible, it is important that we understand why it is impossible.

I think the idea of time travel is very seductive.

You know you're a hopeless record nerd when your time travel fantasies always come around to how cool it would be to go back to 1973 and buy all the great funk and jazz and salsa records that came out that year on tiny obscure labels and are now really rare and expensive.

Unlike some of the time-travel movies I love, like 'Primer' or '12 Monkeys,' 'Looper' is not about time travel. It's about this situation that time travel creates and the people dealing with that situation. So narratively, the big challenge was to have time travel get out of the way.

When you look at the calculation, it's amazing that every time you try to prove or disprove time travel, you've pushed Einstein's theory to the very limits where quantum effects must dominate. That's telling us that you really need a theory of everything to resolve this question. And the only candidate is string theory.

If you're going to write time travel stories, you have to sort of figure out how does time travel work in this particular universe that I'm dealing with.

One of the great things about music is that it has the capability of time travel - you smell a certain smell in the room and it takes you back to your childhood. I feel like music is able to do that, and it happens to me all the time.

Making money is often more fun than spending it, though I personally have never regretted money I've spent on friends, new experiences, saving time, travel, and causes I believe in.

Time travel is a fantasy we all have. The 'Back to the Future' series really exploits that wish.

In Einstein's equation, time is a river. It speeds up, meanders, and slows down. The new wrinkle is that it can have whirlpools and fork into two rivers. So, if the river of time can be bent into a pretzel, create whirlpools and fork into two rivers, then time travel cannot be ruled out.