Book Review: The Little Book of String Theory and The Hidden Reality

The Little Book of String Theory
by Steven S. Gubser
Princeton, 2010
174 pages (hardcover)


Science always seems to be in need of good PR. The lack of decent communicators has only contributed to the denialism that haunts discussions of evolution or climate change, leading outsiders occasionally to want to shoot the messenger.

Of course, any academic in any field can get so used to his or her own world that we forget how to engage in regular conversation. We construct long nuanced and specialized sentences that are free of colloquialisms and full of caveats, and then deconstruct the short and pithy to death. It is a hazard of the job.

With that in mind, I’m grateful to see that two recent volumes, Steven S. Gubser’s The Little Book of String Theory and Brian Greene’s The Hidden Reality, bring several complicated discussions down to earth for the rest of us.

The Little Book of String Theory delves into the world of superstring theory without losing the reader in a maze of mathematics. String theory is a fascinating and promising field that appears to be mathematically necessary, but as of yet, still needs experimental verification. There are hopes that the Large Hadron Collider will help to fill this gap, perhaps enabling string theory to be that elusive theory of everything.

What is it? “Strings are like little rubber bands,” writes Gubser, “but very thin and very strong. An electron is supposed to be actually a string, vibrating and rotating on a length scale too small for us to probe even with the most advanced particle accelerators to date.”

Everything is made of one thing, vibrating strings of energy, which are not entirely unlike the strings of a musical instrument. All fundamental objects exist based on the diverse vibrations of these strings.

Gubser focuses on the ideas rather than the math and the names involved (though he does introduce equations and offers an explanation as to what they mean). He introduces readers to fundamental physics and then takes us on a ride through the complicated world of string theory, which includes discussions of branes, black holes, multi-dimensional space, gravitons, symmetry, supersymmetry, etc.

It is an ambitious book which attempts to engage the reader on a very complicated topic in “plain English.” I enjoyed reading it and will likely read it again in the near future. My interest in science helped provide what I think was the necessary background for engaging a book like this on some meaningful level, but I believe that it may not be as accessible as it claims.

While I found Gubser’s book to be helpful, I think it still may underestimate the demands of the reader who picks up a book with the unassuming title of The Little Book of String Theory. I would not go as far as suggesting childish cartoons as found in the Dummies series of books (though he does offer several helpful illustrations), but a glossary would help the volume tremendously.

Having said that, I do recommend it. Readers benefit from fairly short chapters, leaving the book only at 174 pages. However, I might recommend one detour on the way to it, and that is through Brian Greene’s territory.

The Hidden Reality: Parallel Universes and the Deep Laws of the Cosmos

by Brian Greene
Knopf, 2011
370 pages (Hardcover)


Greene is known for drawing analogies from life to explain the complicated world of science for the masses, earning him a guest role and a bit of a jab at his expense on CBS’s Big Bang Theory (see below).

His book, The Elegant Universe (1999), also explored string theory and became a New York Times best seller as well as a NOVA special (see the end of this post). His newest book, The Hidden Reality, picks up the discussion with more on parallel universes—the multiverse—a potential outcome of string theory (see Brian Greene explain string theory for TEDTalks below).

Most people tend to think of the universe as enclosed and including everything there is, Greene reminds us. We are on a planet that is part of the solar system. That solar system is part of a galaxy and that galaxy is part of a universe of galaxies. That is everything.

Many scientists suggest, however, that our universe may be part of something bigger and infinite—the multiverse. The exact nature of the multiverse is not known and several theories have been offered. Perhaps it is the Quilted Multiverse or an Inflationary Multiverse, both of which are based on inflation, or the Brane, Cyclic, or Landscape Multiverses, which are derived from string theory. (There’s more where that came from.)

The possibilities pose some interesting scenarios.

An infinite multiverse would contain an infinite number of universes. Our universe in this multiverse inhabits a cosmic horizon that includes everything in our neighborhood of space (all our galaxies, stars, planets, etc.). We are contained within this horizon and shut off from other universes in the multiverse.

Now also consider that our specific universe is also made up of a finite number of possible particle arrangements. But what if space is infinite and our universe is only one of an infinite number of other universes? A finite number of arrangements and an infinite number of universes means that the combination found in our galaxy would eventually repeat in another.

Greene imagines this like a deck of cards:

…imagine that Randy, an expert card dealer, has shuffled a gargantuan number of decks, one by one, and neatly stacked each next to the others. Can the order of cards in every shuffled deck be different, or must they repeat? The answer depends on the number of decks…If the number of decks Randy shuffles exceeds the number of different possible card orderings, then some of the shuffled decks would match. If Randy were to shuffle an infinite number of decks, the orderings of the cards would necessarily repeat an infinite number of times.

The implications for reality are shocking. “The limited number of different card orderings ensures that with enough decks, Randy’s shuffles will necessarily repeat. By the same reasoning, the limited number of particle arrangements ensures that with…enough independent cosmic horizons—the particle arrangements…must somewhere repeat.

This means that somewhere out there is another universe like ours that has a galaxy exactly like ours and a planet exactly like ours. In some universes the repetition may be very close to ours, but vary only slightly (like having one card that is different from the others in an otherwise identical ordering).

In an infinitely big universe, the repetition is more extreme. There are infinitely many patches in an infinite expanse of space; so, with only finitely many different particle arrangements, the arrangements of particles within patches must be duplicated an infinite number of times.

If human beings also are understood to be an arrangement of particles, logic then necessitates that individuals and their lives are repeated in every possible variation in an infinite space.

Multiverse thinking is the best stuff of science fiction. In terms of Star Trek lore, it means that somewhere I may have that evil Spock goatee or I never existed at all. It allows us to think about the possibilities and alternate histories of the world (see Brian Greene explain the multiverse below).

Watch A Look at the Universe with Brian Greene on PBS. See more from Need To Know.

In thinking of the implications for religion in general, the discussion of the multiverse poses the most significant problems. The math may seem to imply the potential reality of the multiverse, but what would it mean for Christianity? In those universes where everything is exactly the same, how often does Christ die? How many Sons of God are there? In one universe, does Moses free his people and in another fail? Does Herod get his way? Do the Arians win at Nicaea? Does Harold Camping get the rapture correct? (Wait, now that can’t be possible in any universe.)

Perhaps that question is only one of theory, never to be proven to the point that it concerns the theologian. Greene himself acknowledges the difficulty in demonstrating the reality and testability of the multiverse, that is, it may be impossible to build the evidence necessary (beyond the math) because the laws of our own universe impose a barrier or horizon which we cannot pass.

And while he is also cautionary, he also reminds the reader that “Scientific work going back well over a century has accepted that a theory may invoke hidden, inaccessible elements—provided it also makes interesting, novel, and testable predictions about an abundance of observable phenomena.”

If the experimental and observational evidence supporting a theory compels you to embrace it, and if the theory is founded upon such a tight mathematical structure that there’s no room for cherry-picking among its features, then you have to embrace all of it. And if the theory implies the existence of other universes, then that’s the reality the theory requires you to take on board.

In any case, there is a lot to consider in reading The Little Book of String Theory and The Hidden Reality. Like Gubser, Greene assumes very little about the reader and leaves out the complicated math (mostly). If a reader is a bit more advanced and does not need read an introduction to a particular subject (like General Relativity, for example), Greene tells the reader where to jump ahead to in the book. As a tool, this helps to make his work assessable to readers of varying backgrounds.

But like Gubser, Greene’s book also could use a glossary.  Perhaps in another universe he included one.


Watch all three parts to the NOVA special of The Elegant Universe

Watch the full episode. See more NOVA.

Watch the full episode. See more NOVA.

Watch the full episode. See more NOVA.

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