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

We can certainly go further than cats, but why should it be that our brains are somehow so suited to the universe that our brains will be able to understand the deepest workings?

I have long thought that anyone who does not regularly - or ever - gaze up and see the wonder and glory of a dark night sky filled with countless stars loses a sense of their fundamental connectedness to the universe.

How can a speck of a universe be physically identical to the great expanse we view in the heavens above?

The boldness of asking deep questions may require unforeseen flexibility if we are to accept the answers.

If the theory turns out to be right, that will be tremendously thick and tasty icing on the cake.

A unified theory would put us at the doorstep of a vast universe of things that we could finally explore with precision.

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

Physicists are more like avant-garde composers, willing to bend traditional rules... Mathematicians are more like classical composers.

We might be the holographic image of a two-dimensional structure.

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

All mathematics is is a language that is well tuned, finely honed, to describe patterns; be it patterns in a star, which has five points that are regularly arranged, be it patterns in numbers like 2, 4, 6, 8, 10 that follow very regular progression.

Art makes us human, music makes us human, and I deeply feel that science makes us human.

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.

As scientists, we track down all promising leads, and there's reason to suspect that our universe may be one of many - a single bubble in a huge bubble bath of other universes.

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.

Black holes, we all know, are these regions where if an object falls in, it can't get out, but the puzzle that many struggled with over the decades is, what happens to the information that an object contains when it falls into a black hole. Is it simply lost?

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.

Exploring the unknown requires tolerating uncertainty.

Falsifiability for a theory is great, but a theory can still be respectable even if it is not falsifiable, as long as it is verifiable.

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

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 believe we owe our young an education that captures the exhilarating drama of science.

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

I do feel strongly that string theory is our best hope for making progress at unifying gravity and quantum mechanics.

I enjoy reading blogs, but am not interested in having my spurious thoughts out there.

I like 'The Simpsons' quite a lot. I love the irreverent character of the whole show. It's great.

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.

I may be a Jewish scientist, but I would be tickled silly if one day I were reincarnated as a Baptist preacher.

I think it's too fast to say that all sci-fi ultimately winds up having some place in science. On the other hand, imaginative minds working outside of science as storytellers certainly have come upon ideas that, with the passing decades, have either materialized of come close to materializing.

I think math is a hugely creative field, because there are some very well-defined operations that you have to work within. You are, in a sense, straightjacketed by the rules of the mathematics. But within that constrained environment, it's up to you what you do with the symbols.

I think the appropriate response for a physicist is: 'I do not find the concept of God very interesting, because I cannot test it.'

I think the relationship between memory and time is a very deep and tricky one, to tell you the truth. I don't consider memory another sense. I do consider memory that which allows us to think that time flows.

I would say in one sentence my goal is to at least be part of the journey to find the unified theory that Einstein himself was really the first to look for.

I would say in one sentence my goal is to at least be part of the journey to find the unified theory that Einstein himself was really the first to look for. He didn't find it, but we think we're hot on the trail.

I wouldn't say that 'The Fabric of the Cosmos' is a book on cosmology. Cosmology certainly plays a big part, but the major theme is our ever-evolving understanding of space and time, and what it all means for our sense of reality.

I'd say many features of string theory don't mesh with what we observe in everyday life.

I've had various experiences where I've been called by Hollywood studios to look at a script or comment on various scientific ideas that they're trying to inject into a story.

I've seen children's eyes light up when I tell them about black holes and the Big Bang.

In any finite region of space, matter can only arrange itself in a finite number of configurations, just as a deck of cards can be arranged in only finitely many different orders. If you shuffle the deck infinitely many times, the card orderings must necessarily repeat.

In my own research when I'm working with equations, I never feel like I really understand what I'm doing if I'm solely relying on the mathematics for my understanding. I need to have a visual picture in my mind. I'm constantly translating from the math to some intuitive mind's-eye picture.

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.

Intelligence is the ability to take in information from the world and to find patterns in that information that allow you to organize your perceptions and understand the external world.

It's hard to teach passionately about something that you don't have a passion for.