Time Travel: Beyond the Science Fiction

As a kid who grew up watching Somewhere in Time, Back to the Future, and obscure Star Trek episodes (blame my Trekkie father), I couldn’t resist Allen Everett and Thomas Roman’s new book, Time Travel and Warp Drives, which comes out today. Roman, a mathematics professor at Central Connecticut State University, says the book attempts to strike a balance between whimsical sci-fi and dense textbooks. “We didn’t want to just write another ‘gee whiz ‘ book where you say lots of things but don’t give any reasons for them,” he told me.

To keep the material accessible to those who, like me, think time travel is cool but didn’t major in math, Roman and Everett, a retired Tufts physics professor, promise that readers need only have high-school algebra under their belts to understand their explanations. I caught up with the authors recently for a conversation about what makes time travel fiction good, the grandfather paradox, and, of course, Star Trek.  Excerpts of the interview are below.

Slate: What piece of time travel pop culture—movies, books, or television—has most influenced your work? 

Thomas Roman: Probably  H.G. Wells’ The Time Machine, wouldn’t you say, Allen?

Allen Everett: No, I think I might be inclined to say Star Trek.

TR: Well, Star Trek would be my second choice.

AE: Of course, [part of] the title of the book comes from Star Trek—the warp drive.

Slate: Tell me a little bit more about what a warp drive is.

TR: A warp drive is basically a method of faster than light travel. In Star Trek, that’s accomplished by matter and anti-matter engines. What we discuss in the book is that’s actually not the type of energy that you would need for a warp drive. It turns out what you need for a warp drive is something more bizarre, called negative energy, which the laws of quantum mechanics predict, and allow you to make in small amounts.

Slate: You spend a lot of the book talking about special relativity and how it provides proof for forward time travel. Can you talk about that a little bit?

TR: One of the predictions that came out of [special relativity] is the phenomenon of time dilation: If I have a clock in a space ship, and it’s moving relative to my clocks on the Earth, I will measure the clocks on the space ship to run slower compared to my clocks on the earth. If you had a space ship that went out to a distant star at a speed near the speed of light and came back, special relativity predicts that  maybe 100 years might pass on Earth where maybe only 10 years would pass on the ship.

Slate: Has this effect been proven?

TR: This hasn’t been done with space ships, [but] it has been done with elementary particles. In fact, the time dilation effect is tested literally thousands of times a day in particle accelerator laboratories all over the world. [Say] you have a particular particle that might live a certain amount of time before it decays and breaks up into other particles. Let’s suppose that the particle is at rest with respect to you. [The time it takes to decay] might take, say, a micro second. If the particle is whizzing along in a particle accelerator at a speed near the speed of light, that might take 30 micro seconds as measured by observers watching the particle whiz by. The particle’s clock compared to the lab observer’s clock appears to be running slow. The particle lives longer as seen by the lab observer than it would if particle were at rest with respect to you.

Slate: Any recommendations for great time travel movies or reads?

TR: I would suggest Terry Gilliam’s film called 12 Monkeys. Another one is an old Twilight Zone episode called “No Time Like the Past.

AE: I would add to that a short story by Robert Heinlein called “By His Bootstraps.”

Slate: What makes these superior to other titles? 

TR: Given that there’s an unknown mechanism for time travel that the author doesn’t really explain [because he can’t], then the question [becomes], how does the author deal with the paradoxes or potential paradoxes [of time travel]? And that’s what I think is well done in these things that we’ve mentioned.

Slate: What’s an example of a paradox?

TR: If I go back in time and try to kill my grandfather, and I succeed in killing my grandfather, then I would have never been born to build a time machine and go back and kill my grandfather.

Slate: So how do you get around that type of paradox?

TR: Either you go back in time and you try to kill your grandfather and something always prevents you from doing that—you slip on a banana peel or your thumb jams or something like that. The other possibility is you go back in time, kill your grandfather, and at that point the universe splits. The murder of your grandfather occurs in a different universe. The universe you find yourself in, i.e., the one in which you killed your grandfather, is the universe in which you were never born. So you have no past in that universe, only a future history. You live out your life in that universe for the rest of your life, but you can’t get back to the universe that you started from.