The New Time Travelers: A Journey to the Frontiers of Physics by David Toomey

“I know well enough what it is,” St. Augustine wrote of time, “provided that nobody asks me, but if I am asked what it is and try to explain, I am baffled.”

We don’t call his major book the Confessions for nothing. On this topic, almost all of us could produce a confusing volume. Ponder, for instance, your stance on a point made by David Toomey, a teacher of nonfiction writing at the University of Massachusetts at Amherst, about how most of us walk around with two theories of time, tensed and tenseless.

In the tenseless theory of time, Toomey states, “all that has existed and will exist is located at some point along a continuum. By its distance from a given moment, most commonly the year 0, any event may be located. … The tenseless theory deals with the problem of the present by simply dismissing it. It allows the present moment no privileged position other than that it is coincident with the moment at which one says, `This is the present moment.'”

Here, Toomey asserts, “our intuition objects” because we also view time as segmented into “past,” “present” and “future.”

“Surely,” he writes, “the present moment is a privileged position. After all, we can see, hear, and otherwise sense things that exist in the present, whereas we cannot see, hear, or otherwise sense things that existed in the past or things that will exist in the future. Especially by such comparison, the present seems real. … The two theories are utterly incompatible.”

Except, of course, in the mind of Joe Time-Clueless, going about his normal day.

That’s the bad news: Most of us are Augustinians (so to speak), even if we can pick out Einstein from Schweitzer in a poster shop. But remember the most fun thing you ever imagined in junior high school? (Maybe the second most fun thing.) Hurtling back in a time machine to Elizabethan England, ancient Greece, or the day before you flunked an exam? Exploring a month from now whether so-and-so at the next desk will be smitten with you? H.G. Wells, “A Connecticut Yankee, Robert Heinlein, all of that?

Here’s the good news. Futureward time travel isn’t just possible, it’s real, what Toomey calls “an inevitable consequence of Einstein’s theory of special relativity.” And it appears nothing in modern physics theoretically bars the possibility of “past-directed time travel, though presumably airlines will find a way to make you buy a round-trip ticket anyway.

All right — before you physicists out there start e-mailing, take a cold shower. Yesterday. That’s why the book is here. This is a book review. Argue with Toomey.

First, he holds your hand and offers what might be called a relatively clear explanation of both “commonsense” and sophisticated theories of time: how inventions such as the clock swayed the former notions, spurring belief in universal time, and how Einstein and others articulated and refined the latter efforts. Then he leads us through the last three decades of serious discussion among physicists at California Institute of Technology and elsewhere — figures such as Kip Thorne, Igor Novikov, Frank Tipler, John Wheeler and Stephen Hawking (a skeptic) — about how modern physics might permit time travel. (See Black Holes and Time Warps by Thorne for more technical descriptions than Toomey attempts.)

In comparing science fiction and science fact, Toomey gives due credit to the former, admitting he learned while researching the book that it often prods exploration of the latter. He discusses “cause and effect” paradoxes of pastward travel, mechanical obstacles, and ethical dilemmas. He familiarizes you with the notorious wormhole — the postulated “shortcut” in time-space that would permit connection between two widely distant points — as well as cosmic strings, bubbles of space, and more likely additions to your conceptual vocabulary.

Also: Before you start cutting out lattes to save for a ticket, be advised that top physicists think pastward time travel would require the manipulation of black holes and titanic amounts of energy, perhaps drawing on “ten thousand average-sized stars.” Even China may not be able to do it cheaper.

An inevitable conclusion is that at least one man, David Toomey, can claim to have experienced time travel — to have ventured to where few English-literature Ph.D.’s have dared before — and returned to speak of it.

To judge The New Time Travelers “multidimensional” seems only fair. For now — whatever that little word means — accompanying him through his light cones and other odd places looks like the best option for the rest of us.