Yes, there is a quantitative aspect to science that should not be denied, but it can be in the service of interesting rather than boring problems. Ten years after high school, most students are not going to solve a problem with pulleys and levers. But they still might want to know about the expansion of the universe and about cool things in atomic physics and lasers — which they’ll find interesting and fun.

Q. “From Eternity to Here” is about the physics of time. Why do you study time?

A. Because it is a crucial part of how we think about the universe. It turns out that one of the great mysteries of time — why it has a direction — is really a question about how the early universe was organized. There’s something called “the arrow of time” and it is simply the direction in which time passes from the past to the future. There are many ways in which the past and future are different: things become messier toward the future; we remember yesterday and not tomorrow; actions we take now affect the future but not the past. All of those reflect the arrow of time.

Now, the origin of the arrow of time is a mystery. Based on the laws of thermodynamics, we understand how it works. But we don’t understand why there is an arrow. It comes down to conditions near the Big Bang; the universe started out highly organized and has been becoming more random and chaotic ever since. What I said on Colbert was that the universe is like a mechanical toy that started all wound up, and has been winding down for the last 14 billion years.

Q. You write that the nature of time is such that we can’t go backward.

A. It’s likely that we can’t do time travel. But we don’t know for sure. The arrow of time comes from the increase of entropy, meaning that the universe started out organized and gets messier as time goes on. Every way in which the past is different from the future can ultimately be traced to entropy. The fact that I remember the past and not the future can be traced to the fact that the past has lower entropy. I think I can make choices that affect the future, but that I can’t make choices that affect the past is also because of entropy. I can choose to have Italian food tonight, but I cannot choose to have not had it last night. But if I travel into the past, all that gets mixed up. My own personal future becomes part of the universe’s past. We’re not going to make logical sense of that. So the smart money would bet that it’s just not possible.

Image PRESENT Sean Carroll studies, among other things, why time has a direction. Credit... Natasha Calzatti for The New York Times

Q. The centerpiece of the recent movie “Benjamin Button” and the ABC television series “Flash Forward” is the time travel. How do you rate the science of those entertainments?