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The quest for a theory of everything

Theoreticians are seeking the Holy Grail of physics: one set of principles for relativity as well as quantum mechanics.
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Over the past century, physicists have unlocked the secrets behind radio and television, nuclear energy and the power of the sun. Now they’re seeking the ultimate prize: a “theory of everything” that could reveal a bizarre realm of interdimensional wormholes and time warps.

Such a theory would give us the ability to “read the mind of God,” says Cambridge cosmologist Stephen Hawking. And in Hawking’s opinion, there’s a 50-50 chance that someone will discover the Holy Grail of physics within the next 20 years.

It won’t be easy, though: The discoverer would have to find the harmony underlying two themes as discordant as light Bach and heavy rock.

On one side is Albert Einstein’s theory of general relativity. Einstein saw the large-scale universe as a smooth, curved surface in four dimensions (the three dimensions of space plus time). The gravitational force that binds us to the earth arises from the very structure of that space-time continuum.

On the other side is quantum theory. Beginning in the 1920s, a generation of scientists defined the small-scale universe as a collection of fuzzy phantoms. These subatomic particles couldn’t be precisely located in space and time, but their interaction could be described in statistical terms.

Space-time's out of joint
Both theories are proven successes — but taken together, they’re out of joint. The equations that describe the gravitational field are completely different from those for electromagnetism and subatomic interactions.

Moreover, each theory is incomplete by itself. Relativity cannot tell us how the big bang gave rise to the universe as we know it, or what lies within the black holes created by the collapse of massive stars. Quantum theory, meanwhile, only describes an assortment of particles, mathematical constants and equations — without divining the sense and symmetry underlying them all.

For decades, theorists have tried various strategies to roll up the gravitational field and the quantum field into one set of equations. Most of the attempts failed. “Whenever we tried to calculate numbers from these theories, we would arrive at meaningless infinities,” said theoretical physicist Michio Kaku.

Superstrange superstrings
But one bizarre approach is gaining popularity. It turns out that the equations of quantum theory can mesh perfectly with the theory of relativity — if we look at them from the perspective of a 10-dimensional universe.

The concept is called “superstring theory,” because theoreticians imagine the core components of the universe as tiny loops of string or membranes vibrating in 10 dimensions. Different resonances of the vibrations correspond to different types of particles. Thus, electrons, neutrinos and other elementary particles fit on a grand cosmic scale, just as the notes A, B and C fit on a musical scale.

Kaku says it should come as no surprise that the universe makes more sense in higher dimensions. After all, Einstein made the universe seem more sensible by including time as the fourth dimension.

But if the universe we only dimly understand as having four dimensions really has 10 — where are the other six dimensions? Kaku and his fellow string theorists contend that when the big bang inflated our four dimensions into the universe as we know it, the extra six dimensions collapsed into loops smaller than the smallest observed subatomic particle.

If humans could somehow identify and harness those dimensions, it might become possible to manipulate those interdimensional fields. You could create stable “wormholes” for rapid transit across the universe. You might even be able to drop into parallel “quantum universes” that operate under physical laws completely different from our own.

Needle in a cosmic haystack
Exploring such science-fiction possibilities would require resources of science-fiction proportions.

There are millions of possible solutions for the superstring equations — and figuring out the right solution for our universe would be like picking a needle out of a galaxy-sized haystack. Even if the theory turns out to be right, probing the shrunken dimensions would require energies approaching the scale of the big bang — trillions of trillions of times more powerful than a hydrogen bomb.

However, outer space could open a window to the hidden dimensions and at least provide some confirmation of superstring theory. By observing the patterns of particles and antiparticles flying through space, researchers just might find indirect evidence to back up a “theory of everything.”

This article is based on material from “Hyperspace” and “Visions” by Michio Kaku.