This article originally appeared on Beliefnet in 2001.

If occasional brushes with relativity theory, quantum mechanics and similar concepts have made your head spin--quick now, is it fermions or bosons that occupy the same space?--you won't be pleased to hear that the most talked-about new idea in physics, "superstring" theory, makes Einstein seem like whistlin' Dixie.

Superstring theory posits there are at least 10 and perhaps 26 invisible dimensions crammed into every particle of your body, folded up to unimaginable smallness, and that from such structures, reality is composed. The invisible dimensions have no mass, but by spinning incredibly fast, they impart the qualities of mass to larger things such as protons and electrons. Thus, the universe is ultimately made of spinning nothing locked up in weird miniature dimensions that are wholly real, yet cannot be detected by any instrument, not even the largest and most powerful particle accelerator or "atom smasher."

More on superstring theory in a moment, but first let's make a parallel between it and theology. Einstein's General Theory of Relativity was considered strange when proposed, but it had testable elements. The theory predicted that there would be black holes, that some distant starlight would arrive at Earth "bent," and that the universe might be expanding. When the existence of black holes, bent starlight and cosmic expansion were confirmed, relativity theory became grounded in the observed. Quantum mechanics, in turn, predicted that subatomic particles would exhibit counterintuitive properties, such as the ability to hold energy only in discrete amounts--say, in units or one or two, but never one-and-a-half. When atom smashers found exactly those properties, quantum theory became an observed effect.

Superstring theory, by contrast, holds that the numerous hidden dimensions are so ultra-tiny (trillions of times smaller than atoms) that we'll never be able to prove they are there; yet, that they make us what we are. And so, in this, superstring theory is like theology. People of faith believe that in addition to the regular three dimensions plus time, the universe has one more critical aspect, the plane of the spirit, which is real and potent despite our inability to observe it directly or measure it with any instrument. Superstring physicists believe that in addition to the regular three dimensions plus time, the universe has at least six more critical aspects, the string planes, which are real and potent despite our inability to observe them directly or measure them with any instrument.

Of course since faith in one type of invisible dimension, the spirit, is loaded with value judgments, while faith in the superstring dimensions is just physics, reactions to the two vary widely. When superstring theory was first proposed in the 1980s, it won almost instant academic and media embrace. Many newspapers gushed over the news in their excited (if nearly incomprehensible) stories, while Time magazine named Ed Witten of Princeton, the first prominent superstring thinker, one of the "leading minds of his generation." If a member of the clergy had expounded on the reality of an invisible spiritual dimension in the same faculty lounges and media editorial meetings where the notion of a cornucopia of invisible dimensions was accepted with perfect equanimity, the clergyperson would have been dismissed as believing a kooky mythical idea.

Now back to superstring theory. The idea arose because Einstein's relativity laws, which are observed to work on the grand scale of the cosmos, and quantum mechanical explanations, which are observed to work on the infinitesimal scale of the inner atom, wipe each other out when they merge. We can skip the techno-details here, but suffice to say that relativity appears to govern very large things but break down at the level of the small; quantum mechanics appear to govern very small things but break down at the level of the large. A related problem is that quantum explanations of subatomic behavior work only if you (essentially) assume there is no gravity, and that's obviously not right.

Seeking to fix this, theorists pursued "Grand Unification," a way to tinker with relativity and quantum theories until they combined. Despite the media fixation with this idea (which is often mistakenly called The Theory of Everything, which it would hardly be; Grand Unification has smaller ambitions, like explaining why gravity doesn't crush subatomic particles), little progress has been made. Then theoretical physicists began to posit the existence of superstrings. Essentially, these thinkers proposed that events at the quantum levels are rendered sensible by much tinier factors--the hidden dimensions--that are sufficiently powerful to account for why matter exists, yet can never be seen.

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