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A Layperson's Description in 465 wordsAfter Larry's book came out in '95, the folks at Houston Advanced Research Center (HARC) knew me a bit because the compression chapter had lead me to research HARC-C [which was a very big deal right at that time!]. As part of the gig I got with them, I composed the following summary of string theory, which was pertinent because of Prof. Dimitri Nanopoulos' strong association with HARC. I was really proud that he pronounced: "It was a miracle how you could shrink it down to such a nutshell." An additional source for this was Steven Weinberg's Dreams of a Final Theory (Pantheon Books, 1992).The established worldview of particles and force fields has been replaced by the new perspective of "quantum fields". These quantum fields are described by wave functions, which can resolve themselves in a variety of ways, some of which are more probable than others. Any particle exists because its wave function has collapsed into a discrete quantum form. Even so, particles retain the potential to behave like waves under certain circumstances, as illustrated by the well-known example of an electron passing through two slits at the same time. Also, a field produced by any of the four major forces of nature (gravity, electromagnetism, and the weak and strong forces) can collapse into one of the types of force particles called "bosons". Although gravity is now thought of as a curvature of space-time, even gravity is predicted to have its own unique force particle or boson - known as the "graviton".
Two different particles in a formula may be called "symmetrical" if they can trade places. It is now supposed that as the universe cooled in the first minutes after the "Big Bang", particles which could previously exchange places could no longer accomplish this "symmetrical" switch. The symmetry would spontaneously break as the energy state fell below a critical threshhold. In this hierarchy of breaking points, first gravity and then the strong force became unable to switch with the others. At still lower energies, the electromagnetic and weak forces became assymetrical. The now-cancelled Superconducting Super Collider would have been able to produce this lower energy state, above which the electromagnetic and weak forces become symmetrical. Many groups of elementary particles are symmetrical with each other even at lower energies and, in the absence of fresh data, the trusty yellow pad may be the source of many insights and speculations quite useful to other physicists.
A striking departure from the mathematics of quantum field theory began in 1968 when Gabriel Veneziano at CERN tried to describe the strong force without using quantum fields. This was the beginning of string theory, which identifies particles as minute tears or rips in the fabric of space-time. These strings are so small that their standard identification has been as mere points, but strings have properties which points don't possess: infinite modes of vibration, as well as a property of being either open or closed (e.g., a string that is closed like a loop results when two open strings collide together). When early string theory predicted a particle which was not subject to the strong force, the development of superstring theory identified this particle as the graviton. This approach led to related theories of supersymmetry (in which particles of different spin are grouped into superfamilies) and supergravity. In superstring theory a string may have infinite modes, leading to infinite varieties of elementary particles.
© 1995 Philip Merrill all rights reserved
Philip Merrill |