Space and time, strings attached

A few years ago, Brian Greene, a mathematician and physicist at Columbia University, wrote a witty, deep, yet wholly accessible book on the remote subject of string theory, which deservedly became a bestseller and made Greene the closest thing to a rock star in his field. He was even the host of a TV show based on the book, “The Elegant Universe: Superstrings, Hidden Dimensions, and the Quest for the Ultimate Theory.”

Such a debut is hard to live up to, and Greene’s new book, “The Fabric of the Cosmos: Space, Time, and the Texture of Reality,” does lack some of the loveliness of his first. The difficulty comes with the territory: This book covers all of space and time -- which includes just about everything in physics and sometimes reads that way. At his best, though, Greene is as elegant as ever, cutting through the fog of complexity with insight and clarity; space and time, you might even say, become putty in his hands.

In the end, Greene confirms our worst fears: Rumors of the doom of space and time have not been exaggerated. They’ve been unraveling ever since Albert Einstein, and the worst is yet to come. Understanding the “why” requires confronting a question that has blown minds for millenniums: What are space and time, anyway? Begin by leaving your smug notions of “reality” at the door. “It’s easy to be seduced by the face nature reveals directly to our senses,” writes Greene, who compares everyday reality to a magic act in which nature tricks us with her clever sleights of hand. “In recent years, physicists have expended much effort in trying to explain nature’s ruse.”

What they’ve found is enough to turn your insides out. Take space. Is it real? The argument has raged for centuries. Isaac Newton unambiguously asserted that space is “out there” like a chess board on which we play our lives; philosopher Gottfried Wilhelm von Leibniz scoffed, saying space is merely a way to order relationships between objects -- no more real than a family tree. Einstein turned Newton’s solid space to taffy, showing that it stretched and shrank depending on the relative motion of observers. Then he warped it, and so explained gravity. But even Einstein wasn’t willing to believe the implications of quantum mechanics, which predicted that two particles having no contact whatsoever can somehow be in touch over arbitrarily large swaths of space -- an obvious absurdity. Yet laboratory experiments have since demonstrated that particles do just that. And what is “space” if it doesn’t separate one thing from another?

As for time, it too feels intuitively “out there.” Newton saw it as a cosmic metronome that orders events: Future follows present follows past. But Einstein showed that two observers can’t even agree on which events are simultaneous -- never mind how fast time flows.

“These theories,” Greene writes, “showed that we each pick up a shard of Newton’s old universal time and carry it with us.” Worse, we can’t even pass from one moment to the next because all moments are ever-present.

Consider: Someone writes you a letter from New York, saying it’s snowing “now.” Two days later, you receive the letter. Is it snowing “now”? When is “now,” anyway? And where?

You don’t have to decide because each moment exists for always somewhere in space-time. “If you were having a great time at the stroke of midnight on New Year’s Eve, 1999,” Greene writes, “you still are.” Wherever you go, it’s here. Whenever it is, it’s now. This is not your grandfather’s clock. Between relativity and quantum mechanics, there’s no where to stand; no when to stand, either.

Greene explains much of this through the imaginary adventures of Marge, Bart, Lisa, Homer and a large cast of other characters drawn from popular culture. In “The Elegant Universe,” Isaac and Albert, George and Gracie, played similar roles. But many of his “thought experiments” in “The Fabric of the Cosmos” are so overwrought that they become confusing. It’s hard to imagine a story starring Scully and Mulder that’s harder to follow than an episode of “The X-Files.” But here it is.

Soon enough, though, Greene woos us back, explaining ideas in clear, direct, often poetic language. For example, one of the ways our everyday notions of “here” and “now” may emerge from the state of all heres, all nows, is through the act of observation. Once we note something, we pin it down.

The underlying reason is that particles are really probability waves, and waves don’t occupy a single time or space. Your observation “breaks” the wave -- bringing about what physicists call the “collapse of the wave function.” The description of how all this works (and how it doesn’t) is as good as it gets. And yet, Greene writes, “[a]fter more than seven decades, no one understands how or even whether the collapse of a probability wave really happens.”

However it happens, the implications are freaky: When you break the wave, you not only determine the future, you also determine, in a sense, the past -- because you’ve “pruned” all the possible heres and nows that didn’t lead to the present you observe.

When Greene turns to big-time space-time, or cosmology, the book loses focus, embracing so much that the picture blurs, points get diluted. An entire chapter is devoted to the notion that time is the direction of increasing disorder, which is why eggs don’t unscramble. The punch line here is important: The laws of physics don’t tell time which way to go. So where does the arrow come from? Somehow, the fiery big bang put the universe into an almost impossibly ordered state, from which it has been running down ever since. “A splattered egg,” he writes, “tells us something very deep about the big bang.”

Very nicely put. But how many times -- and in how many ways -- do we need to be told that ice cubes melt rather than spontaneously appear out of warm water?

Another chapter is devoted to the Higgs field, a kind of universal molasses physicists think all particles slog through, thus acquiring mass. True, the “freezing” of the Higgs field did happen in space and time, and has to do with infusing order into the universe, but this discussion does little to illuminate the fundamental nature of space itself. (By the time he gets to the pile of worms in the hot bowl with the frog, you want to jump in yourself.)

It’s also hard to imagine a reader sophisticated enough to enjoy this book who won’t be annoyed by such statements as: “When things get hot or cold, they sometimes change.”

There are other tics: Too much is described as “bizarre,” “profound,” “mind-boggling,” “shocking.” Greene is at his best when he seems to be trying the least: Imagining space-time as a warm loaf of bread, for example. He’s most endearing when he allows himself to contemplate things quietly. Do particles really take all possible paths through space and time, or is this just a story physicists use to make sense of the facts? “I wish I could give you a definitive answer,” he writes, palpably wistful. “But I can’t.” Or: “One can’t help feeling that the fantastic predictive power of quantum mechanics means that it is tapping into a hidden reality that underlies the workings of the universe.”

We can’t yet see this hidden reality -- the magician behind the special effects. But there is some hope, perhaps through string theory, Greene’s specialty, which describes everything from gravity to garbage as “loops and snippets of energy.” Perhaps string theory eventually will allow physicists to pull back the curtain all the way to the big bang and reveal at last how the universe got so orderly. (For now, the most probable answer is that this was merely a probabilistic fluke -- like tossing a coin and getting 10 heads in a row.)

In the meantime, string theory has, among other things, increased the number of spatial dimensions to 10. Creepier still, extensions of string theory imply that descriptions of reality using, say, four dimensions are equivalent to descriptions of the same reality using three or five.

“More and more,” Greene writes, “these clues point toward the conclusion that the form of space-time is an adorning detail that varies from one formulation of a physical theory to the next, rather than being a fundamental element of reality.”

None of this is science if not proved by experiment, and Greene describes some of the ways this might, in fact, happen. Perhaps, the evidence is right in front of our noses, encoded in the cosmic microwave background, the afterglow of the big bang.

“Maybe,” Greene writes, “the universe has already drawn out the microscopic fibers of the fabric of the cosmos and unfurled them clear across the sky, and all we need do is learn how to recognize the pattern.” Sheer loveliness. *

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From ‘The Fabric of the Cosmos’

Physicists spend a large part of their lives in a state of confusion. It’s an occupational hazard. To excel in physics is to embrace doubt while walking the winding road to clarity. The tantalizing discomfort of perplexity is what inspires otherwise ordinary men and women to extraordinary feats of ingenuity and creativity; nothing quite focuses the mind like dissonant details awaiting harmonious resolution. But en route to explanation ... theorists must tread with considered step through the jungle of bewilderment, guided mostly by hunches, inklings, clues and calculations.... Nature does not give up her secrets lightly.