String Theory- A Complicated Theory

String theory is perhaps the most high-profile candidate for what physicists call a theory of everything – a single mathematical framework capable of describing the entirety of the known universe.

At present, physicists have to rely on two such frameworks. Quantum theory, which accurately describes the physics of the very small, and general relativity, developed by Albert Einstein, which describes the physics of the enormously large. The trouble is, the two theories don’t get along.

The trouble boils down to gravity. It’s the only one of the four fundamental forces of nature described by general relativity, and the only one that quantum theory cannot address. Coming up with a model that ties up all four forces in one neat package is a long-standing dream for theoretical physicists.


String theory claims to make that dream a reality. In simple terms, it does this by reimagining what reality is made of. Instead of treating subatomic particles as the fundamental building blocks of matter, string theory says that everything is made of unbelievably tiny strings, whose vibrations produce effects that we interpret as atoms, electrons and quarks.

In order for that to work, string theory has to make one more radical assumption. That instead of living in a universe with three dimensions of space and one of time, we live in one with either 9, 10 or 25 dimensions of space. These extra dimensions are then curled up so tightly that we don’t notice them – much like a silken thread appears one-dimensional until you get close enough to notice its width.

This process of curling up, or “compactification”, can be done in countless billions upon billions of different ways. Each compactification produces a different spacetime, meaning that string theory can realistically predict a multiverse populated by 10^500 different universes. String theory can predict a multiverse with 10^500 universes due to countless compactification possibilities.

Many regard this profligacy as string theory’s fatal flaw. If a theory makes so many different, contradictory predictions, they say, then almost any set of observations could be found to confirm it. In other words, that makes it almost impossible to falsify, and consequently should disqualify it as a valid field of research.

While some attempts to give string theory predictive power are underway, many physicists are looking elsewhere. Whether in the form of loop quantum gravity, causal dynamical trangulation or something else, the true nature of a theory of everything remains elusive. For now.


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