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.

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.

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.

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

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

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

The bottom line is that time travel is allowed by the laws of physics.