Physics grapples with the largest questions the universe presents. 'Where did the totality of reality come from?' 'Did time have a beginning?'

Sometimes attaining the deepest familiarity with a question is our best substitute for actually having the answer.

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

The fact that I don't have any particular need for religion doesn't mean that I have a need to cast religion aside the way some of my colleagues do.

The idea that there could be other universes out there is really one that stretches the mind in a great way.

The number of e-mails and letters that I get from choreographers, from sculptors, from composers who are being inspired by science is huge.

The pinpoints of starlight we see with the naked eye are photons that have been streaming toward us for a few years or a few thousand.

There's no way that scientists can ever rule out religion, or even have anything significant to say about the abstract idea of a divine creator.

We know that if supersymmetric particles exist, they must be very heavy; otherwise we would have spotted them by now.

We're on this planet for the briefest of moments in cosmic terms, and I want to spend that time thinking about what I consider the deepest questions.

As every parent knows, children begin life as uninhibited, unabashed explorers of the unknown. From the time we can walk and talk, we want to know what things are and how they work - we begin life as little scientists.

Before the discovery of quantum mechanics, the framework of physics was this: If you tell me how things are now, I can then use the laws of physics to calculate, and hence predict, how things will be later.

Black holes provide theoreticians with an important theoretical laboratory to test ideas. Conditions within a black hole are so extreme, that by analyzing aspects of black holes we see space and time in an exotic environment, one that has shed important, and sometimes perplexing, new light on their fundamental nature.

Einstein's theory of relativity does a fantastic job for explaining big things. Quantum mechanics is fantastic for the other end of the spectrum - for small things.

Even when I wasn't doing much 'science for the public' stuff, I found that four or five hours of intense work in physics was all my brain could take on a given day.

Every moment is as real as every other. Every 'now,' when you say, 'This is the real moment,' is as real as every other 'now' - and therefore all the moments are just out there. Just as every location in space is out there, I think every moment in time is out there, too.

For most people, the major hurdle in grasping modern insights into the nature of the universe is that these developments are usually phrased using mathematics.

I believe the process of going from confusion to understanding is a precious, even emotional, experience that can be the foundation of self-confidence.

I can assure you that no string theorist would be interested in working on string theory if it were somehow permanently beyond testability. That would no longer be doing science.

I love it when real science finds a home in a fictional setting, where you take some real core idea of science and weave it through a fictional narrative in order to bring it to life, the way stories can. That's my favorite thing.