A soul might very well exist, but we, as physicists, try to measure and quantify everything. So far, no one has been able to create an experiment to do this for the soul. Efforts have been made to weigh the body after death, but each time we find no evidence of a soul. So a soul may very well exist, but it is not a testable theory.

Science is about principles. It's about concepts. It's not about memorizing the parts of a flower. It helps to know some of these things, but if that's all you do that's not science, science is about principles and concepts.

Math is discovered. To be invented requires an inventor, but math exists outside of humanity. But ultimately, the laws of the universe will be reduced down to a single equation, perhaps no more than one inch long. But leaves the final question, where did that one inch equation come from?

A hydrogen bomb, for me, was puny compared to the Big Bang - the creation of the universe. That's what I really wanted to work on - the nature of the universe itself, and that's what I do for a living.

Science is the engine of prosperity. All the prosperity we see around us is a byproduct of scientific inventions. And that's not being made clear to young people. If we can't make it clear to young people they're not going to go into science. And science will suffer in the United States.

We can summarize electricity, magnetism and gravity into equations one inch long, and that's the power of field theory. And so I said to myself: I will create a field theory of strings. And when I did it one day, it was incredible, realizing that on a sheet of paper I can write down an equation which summarized almost all physical knowledge.

We should explore new ways to drive down the cost of space travel. instead of costly booster rockets, maybe we should think of laser/microwave driven rockets, or space elevators. Until then, the cost of space exploration will limit our ability to explore the universe.