To explain this I�ll have to explain a little wave theory first. Very simply, when Maxwell was researching electromagnetics in the 19th century, he came up with the idea that matter radiates three-dimensional waves of alternating magnetic and electric fields. Imagine an expanding sphere radiating from a source, and the sphere is rotating in one given direction, say to the right. We�ll call this the magnetic field, and it is expanding at the speed of light away from the source. Some distance behind this expanding sphere, the strength of the magnetic field gets weaker until it eventually reaches zero. At that point, imagine another expanding sphere gaining strength and following the first magnetic sphere, but this one is rotating at 90 degrees to the magnetic field, say in the direction of top or bottom. This is the electric field. A three dimensional electromagnetic wave is a series of alternating magnetic and electric fields like this that propagate themselves through space at a constant speed (the speed of light) because the energy (or vibration if you will) that they contain fluxes between being a magnetic field and an electric field. Where there is a moving electric field near a magnetic field, a moving magnetic field perpendicular to it is created. Where there is a moving magnetic field and an electric field nearby, a moving electric field perpendicular to it is created, and so on.
The wave theory explained light and radio waves, but it had one problem with it: If the nature of matter is to constantly radiate these energetic waves across the entire spectrum, and if you add up the energy that is carried away from a given radiating body, then according to the formulas this total would be infinite, clearly an absurd result. At the turn of the century, a fellow named Max Planck realized that if energy is radiated in a discrete �packet?or �quanta?for a given frequency, then the total would be finite. Planck called these quanta of electromagnetic energy �photons? and thus began the realization that light has a dual identity as a wave and a particle, but that is not our concern here.
So what�s quantum gravity? Well, right off the bat it tells you that gravity is �something?if it can be quantified, whereas in General Relativity it is �nothing? The other eminent theory of reality before Superstrings came along is Quantum Mechanics, and it can�t explain gravity either because it can�t even acknowledge that there IS gravity! However, even in early Superstring calculations, a mysterious massless particle with �double spin?would refuse to go away from the calculations, however much it annoyed physicists everywhere. In the 1970s somebody finally realized that this may be the calculation for gravity that was needed in a theory that explained our gravity-burdened universe. Thus, the idea of the �graviton?was incorporated into Superstring theory, and so far there has been nothing to suggest that this is wrong.
In basic Newtonian physics, gravity can be observed to act across any distance with no apparent �lagtime. It was this observation that sparked the idea for General Relativity in the first place, because gravity as a distortion wave in space-time that travels at the speed of light just like an EM wave seemed more credible than a force that has infinite speed and range. There is also another startling implication suggested by Supersymmetry.
?1998 [email protected]
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