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.
In many ways, string theory attempts to go beyond Einstein's dream... an all-encompassing description of nature that works at large distances where gravity becomes important as well as small distances where quantum mechanics is important.
As you say, the way string theory requires all these extra dimensions and this comes from certain consistency requirements about how string should behave and so on.
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.
M-theory is the unified theory Einstein was hoping to find.
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.
I came to realise that string theory offers us the best hope of finding a unified theory of all matter and forces.
Some string theorists prefer to believe that string theory is too arcane to be understood by human beings, rather than consider the possibility that it might just be wrong.
One of the strangest features of string theory is that it requires more than the three spatial dimensions that we see directly in the world around us. That sounds like science fiction, but it is an indisputable outcome of the mathematics of string theory.
I think the discovery of supersymmetric partners for the known particles would revolutionize our understanding of the universe.
Physicists have yet to understand why the Higgs boson's mass is what it is.
It's an exaggeration to say that I came up with M-theory.
String theory is the most developed theory with the capacity to unite general relativity and quantum mechanics in a consistent manner. I do believe the universe is consistent, and therefore I do believe that general relativity and quantum mechanics should be put together in a manner that makes sense.
I spent most of my career doing high-energy physics, quarks, dark matter, string theory and so on.
Our best theory of describing space at a fundamental level is probably string theory.
The most important single thing about string theory is that it's a highly mathematical theory, and the mathematics holds together in a very tight and consistent way. It contains in its basic structure both quantum mechanics and the theory of gravity. That's big news.
We know that if supersymmetric particles exist, they must be very heavy; otherwise we would have spotted them by now.
I'd say many features of string theory don't mesh with what we observe in everyday life.
In order to achieve a true understanding of string theory, some new idea will be required, and most likely, some break with the concepts on which we've traditionally based physical theory.
I do feel strongly that string theory is our best hope for making progress at unifying gravity and quantum mechanics.
I started out working on supersymmetry. The theory predicts that for every particle we know about, there will be an additional particle.
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.
In the book, I make the point that here we have string theory and here we have twistor theory and we don't know if either one of them is the right approach to nature.
The stability of what's called the Standard Model of particle physics and its ability to make so many clever predictions with immense precision suggests that we may just be stuck with it, and there may never be an overthrow of that.
My work on symmetries of string theory is on what is known as strong-weak coupling duality, or S-duality.
