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.)

Science is definitely part of America's infrastructure, the engine of prosperity. And yet science is given almost no visibility in the media.

I would like to believe that crop circles are evidence of visitation. But there have been too many people who have admitted to creating these crop circles, and too many people who have shown how to make one on TV programs, so I have my doubts.

I have nothing against investment banking, but it's like massaging money rather than creating money.

Today's clunky smart glasses will be replaced by smart contact lenses. We'll command them by voice, blinking, or even thinking, to interact visually in 3-D with the Internet.

Once again, my colleague Stephen Hawking has upset the apple cart. The event horizon surrounding a black hole was once though to be an imaginary sphere. But recent theories indicate that it may actually be physical, maybe even a sphere of fire. But I don't trust any of these calculations until we have a full-blown string theory calculation, since Einstein's theory by itself is incomplete.

I don't. We've had three technological revolutions that have changed the course of human history, all driven by physics. In the first, the industrial revolution, physicists developed Newtonian mechanics and thermodynamics, which gave us the steam engine and machine power. The second technological revolution was the electricity revolution. That gave us radio, television, and telecommunications. Then, physicists developed the laser and the transistor.