I used to watch the old 'Flash Gordon' series on TV, and it was thrilling to rocket to the planet Mongo every week. But after a while, I figured out that although Flash got the girl and all the accolades, it was really Dr. Zarkov who made the series work. Without Dr. Zarkov, there could be no Flash Gordon.

To understand the difficulty of predicting the next 100 years, we have to appreciate the difficulty that the people of 1900 had in predicting the world of 2000.

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.

Physicists often quote from T. H. White's epic novel The Once and Future King, where a society of ants declares, "Everything not forbidden is compulsory." In other words, if there isn't a basic principle of physics forbidding time travel, then time travel is necessarily a physical possibility. (The reason for this is the uncertainty principle. Unless something is forbidden, quantum effects and fluctuations will eventually make it possible if we wait long enough. Thus, unless there is a law forbidding it, it will eventually occur.)

If you could meet your grandkids as elderly citizens in the year 2100 … you would view them as being, basically, Greek gods… that's where we're headed.

Global warming is controversial, of course, but the controversy is mainly over whether human activity is driving it.

Scientists willing to risk their reputations on higher dimensions soon found themselves ridiculed by the scientific community. Higher-dimensional space became the last refuge for mystics, cranks, and charlatans.