The Theory of Everything followed Albert Einstein to his deathbed. Einstein worked on the TOE — a theory that would tie together everything in nature, but he found himself short in attempts at unraveling the mystery.

Since Einstein, a new theory called the “string theory” has developed as an answer to the question of everything.

Physicist Edward Witten said that string theory traces its origins to a “theory of nuclear force,” in an article entitled, “Unraveling String theory” in a December 2005 in Nature. This theory explains the interactions occurring inside the nucleus of an atom.

It went in and out of style in the seventies and eighties until the mid-eighties when semi-realistic models of particles and their forces were within the grasp of string theorists — including the elusive one: gravity.

Quantum field theory explained the behavior and properties of elementary particles but only when gravity is weak enough that it may be neglected. On the other hand, general relativity can explain the behavior of the cosmos, the Big Bang and provide insights about planets, stars and galaxies.

But it works only when people ignore the quantum nature of objects. String theory brought two diverse, seemingly opposite ideas together.

Now string theory is an important part of a physicists’ education as he or she learns about the rules of the universe.

“In the middle ages, people looked for theories that would predict the maximum number of planets, and on the other hand, we have theories that predict that number of chemical elements,” Thomas Shaeffer, a professor of physics, said.

“We know that the former is wrong — the theory of gravity allows solar systems with multiple planets. So, the question now is whether the number of quarks is like the number of planets or the number of chemical elements. Physicists have a prejudice for the latter, but there are recent indications that maybe its like the former, viz. string theory.”

The theory

In classical particle physics models a theoretical particle called a “graviton” would account for the behavior of the gravitational force, according to the Scientific American award winning “official string theory Web site.” The problem, in particle physics, is that all interactions between particles occur at a zero distance.

But in string theory, strings collide over a small but finite distance.

String theory can be compared to guitar strings, according to the official string theory Web site.

The strings of a guitar resonate at various frequencies and produce various musical notes when they are plucked under tension. Similarly, elementary particles in particle accelerators are akin to the musical notes of vibrating strings. The main difference is that the strings are not tethered, but float in space-time while still retaining their tension.

To reconcile the theories of relativistic gravity and quantum effects, the average size of a string has been calculated to be that of a “Planck length,” which is about 10-33 centimeters. Since scientists lack the technology to detect such small “objects,” string theorists are at times confined to the theoretical domain to explain their results.

The quantum theory of gravity is very difficult to test, as quantum effects come into play when the gravitational fields are strong and such fields are almost impossible to generate on earth.

Other interesting results followed, such as the realization that string theory is not relegated to one-dimensional objects. Scientists have used strings to explain theories about nine, 10 and 11 dimensional space-time systems. Strings have also been applied to explain concepts of “multi-verses” — multiple universes occupying the same space-time domain, but existing in parallel dimensions.

These facets, along with a best-selling book by Brian Greene titled The Elegant Universe : Superstrings, multiple dimensions, and the Quest for the Ultimate Theory, and a related PBS show, created public awareness about string theory.

String theory explains the secret of the universe, but not every scientist is jumping on the bandwagon. The mathematical concepts required for comprehending the string theory are extremely complex, at times beyond the understanding of physicists themselves.

It’s gone super

Mathematicians and physicists are becoming more skeptical of the promises made by string theorists. They believe that inordinate amounts of money have been pumped into a field that has not yet shown concrete results, and that the theories are often nothing more than complex mathematical models followed, according Michael Lemonick’s August 2006 Time magazine article titled, “The Unraveling of String Theory.”

In fact, newer versions of string theory, called the “superstring theory,” speculate about the existence of an infinite number of parallel universes, with no experimental proof to back up the reasoning. Proponents of this theory argue that some version of their theory might describe all of these universes, which includes the idea that any theory or prediction, no matter how ludicrous, can be true in some universe.

Conversely, the possibility exists that a theory could not be true in any of these universes.

“Perhaps string theory is less of a theory and more of a philosophy, mainly because we cannot test any hypotheses related to the field,” Jaydeep Marathe, a doctoral student in computer science, said.

Schaeffer clarifies both sides of the problem. He said that the hope and the hype from string theory was that it would predict the number and properties of elementary particles such as quarks, gluons, neutrinos and electrons.

On the other hand, Schaeffer said he believes that critics argue about a sociological problem — string theory has influential supporters at major universities, such as Princeton and Harvard. Also, it is being hyped in books and popular television channels. This possibly results in support through academic positions and federal grants drained from alternative ideas.

“The promise of string theory was certainly hyped, but so is the promise of the latest cancer drug, or the next nano-tech revolution,” Schaeffer said. “This is not devious — if scientists were not overly optimistic about the promise of their work, why would they spend so much time on it?”

String theory is an extension of the ideas of quantum field theory and has proved useful in understanding both gravitational and non-gravitational phenomena. As a consequence, the time spent studying it is not wasted, according to Schaeffer.

Marathe said the main problem with quantum effects and relativistic gravitation occurs inside a massive black hole, where both effects will be true — other theories fall short while attempting to explain this situation.

As for N.C. State and string theory, Schaeffer said, “the physics department of N.C. State does not currently have a string theorist on the faculty, and if it was up to me, we would hire one.”