If I take the theory as we have it now, literally, I would conclude that extra dimensions really exist. They're part of nature. We don't really know how big they are yet, but we hope to explore that in various ways.

I wouldn't have thought that a wrong theory should lead us to understand better the ordinary quantum field theories or to have new insights about the quantum states of black holes.

String theory is an attempt at a deeper description of nature by thinking of an elementary particle not as a little point but as a little loop of vibrating string.

There was a long history of speculation that in quantum gravity, unlike Einstein's classical theory, it might be possible for the topology of spacetime to change.

In Einstein's general relativity the structure of space can change but not its topology. Topology is the property of something that doesn't change when you bend it or stretch it as long as you don't break anything.

Having those extra dimensions and therefore many ways the string can vibrate in many different directions turns out to be the key to being able to describe all the particles that we see.

As far as extra dimensions are concerned, very tiny extra dimensions wouldn't be perceived in everyday life, just as atoms aren't: we see many atoms together but we don't see atoms individually.

You have that one basic string, but it can vibrate in many ways. But we're trying to get a lot of particles because experimental physicists have discovered a lot of particles.

Spreading out the particle into a string is a step in the direction of making everything we're familiar with fuzzy. You enter a completely new world where things aren't at all what you're used to.

Even before string theory, especially as physics developed in the 20th century, it turned out that the equations that really work in describing nature with the most generality and the greatest simplicity are very elegant and subtle.

Technically you need the extra dimensions. At first people didn't like them too much, but they've got a big benefit, which is that the ability of string theory to describe all the elementary particles and their forces along with gravity depends on using the extra dimensions.

Quantum mechanics brought an unexpected fuzziness into physics because of quantum uncertainty, the Heisenberg uncertainty principle.

On the other hand, we don't understand the theory too completely, and because of this fuzziness of spacetime, the very concept of spacetime and spacetime dimensions isn't precisely defined.

As of now, string theorists have no explanation of why there are three large dimensions as well as time, and the other dimensions are microscopic. Proposals about that have been all over the map.

It's indeed surprising that replacing the elementary particle with a string leads to such a big change in things. I'm tempted to say that it has to do with the fuzziness it introduces.

One of the basic things about a string is that it can vibrate in many different shapes or forms, which gives music its beauty.

But the beauty of Einstein's equations, for example, is just as real to anyone who's experienced it as the beauty of music. We've learned in the 20th century that the equations that work have inner harmony.

If I take the theory as we have it now, literally, I would conclude that extra dimensions really exist. They're part of nature. We don't really know how big they are yet, but we hope to explore that in various ways.

As for the forces, electromagnetism and gravity we experience in everyday life. But the weak and strong forces are beyond our ordinary experience. So in physics, lots of the basic building blocks take 20th- or perhaps 21st-century equipment to explore.

The theory has to be interpreted that extra dimensions beyond the ordinary four dimensions the three spatial dimensions plus time are sufficiently small that they haven't been observed yet.

So when you ask me how string theory might be tested, I can tell you what's likely to happen at accelerators or some parts of the theory that are likely to be tested.

I don't care about movies. I tend to play badminton once a week.

I have a tendency, more than most other physicists, to try to figure out everything all at once, before I publish. And even to try to figure out everything in my head, without pencil and paper.

I just think too many nice things have happened in string theory for it to be all wrong. Humans do not understand it very well, but I just don't believe there is a big cosmic conspiracy that created this incredible thing that has nothing to do with the real world.

I'm actually, for the most part, a complete agnostic politically.

If you are a researcher, you are trying to figure out what the question is as well as what the answer is.

One very important aspect of string theory is definitely testable. That was the prediction of supersymmetry, which emerged from string theory in the early '70s.

Quantum mechanics brought an unexpected fuzziness into physics because of quantum uncertainty, the Heisenberg uncertainty principle. String theory does so again because a point particle is replaced by a string, which is more spread out.

Regardless of any deviations, it was clear I was supposed to end up in math and physics.

We know a lot of things, but what we don't know is a lot more.

You are not here merely to make a living. You are here in order to enable the world to live more amply, with greater vision, with a finer spirit of hope and achievement. You are here to enrich the world, and you impoverish yourself if you forget the errand.

Hope is the struggle of the soul, breaking loose from what is perishable, and attesting her eternity.

All the great things are simple, and many can be expressed in a single word: freedom, justice, honor, duty, mercy, hope.

The tender heart, the broken and contrite spirit, are to me far above all the joys that I could ever hope for in this vale of tears.

The most important training, though, is to experience life as a writer, questioning everything, inventing multiple explanations for everything. If you do that, all the other things will come; if you don't, there's no hope for you.

I hope that people will finally come to realize that there is only one 'race' - the human race - and that we are all members of it.

The only hope is that our civilization will collapse at a certain point, as always happens in history. Then, out of barbarity, a renaissance.

Infuse your life with action. Don't wait for it to happen. Make it happen. Make your own future. Make your own hope. Make your own love. And whatever your beliefs, honor your creator, not by passively waiting for grace to come down from upon high, but by doing what you can to make grace happen... yourself, right now, right down here on Earth.

Hope is generally a wrong guide, though it is very good company by the way.

I don't sit in the corner waiting for death: death has to pursue me. I'm going strong. I hope to reach 100 and ask for an extension, just like my grandmother did.

When I talk to people in need, they tell me they want to hope; they are eager for opportunity; they are ready for better days. And I can tell you that every time their hopes are disappointed, all nations lose.

I'd hope to reach any kid who feels apart from the group - those who seem to be outsiders, who feel different. Kids who want to reach their parents often don't know how to do so.

If we can just take a few companies, and use those as models, as examples, to show the rest of corporate America how they can become more competitive, that's what I'd like to do and that's what I hope to do.

It's part of the calling to at least do a few songs in the show that give people some hope. There's so much hurt in this world and... music is such a great healing balm and a great way to forget your troubles.

Just as a mother finds pleasure in taking her little child on her lap, there to feed and caress him, in like manner our loving God shows His fondness for His beloved souls who have given themselves entirely to Him and have placed all their hope in His goodness.

Yesterday I was a dog. Today I'm a dog. Tomorrow I'll probably still be a dog. Sigh! There's so little hope for advancement.

Testimony is an integral part of the Black religious tradition. It is the occasion where the believer stands before the community of faith in order to give account of the hope that is in him or her.

What can you say about such a man as Christopher Reeve? He embodied all the best that a human being can hope to be.

Hope springs eternal, even in politics.