General relativity is in the old Newtonian framework where you predict what will happen, not the probability of what will happen. And putting together the probabilities of quantum mechanics with the certainty of general relativity, that's been the big challenge and that's why we have been excited about string theory, as it's one of the only approaches that can put it together.

Nature's patterns sometimes reflect two intertwined features: fundamental physical laws and environmental influences. It's nature's version of nature versus nurture.

Energy is the ultimate convertable currency.

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.

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.

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.

We do not know whether there are extra dimensions or multiverse. Let's go forward with the possible ideas that come out of the mathematics. It's hard for us to imagine a universe that would have no time at all.