Imagine a world in which everything is explained, in which human beings would know why they act, how they think, and how they came to be. A complete understanding of the entire universe would flow from one single equation: a grand unified theory. Finding such a theory has been the dream of physicists since the idea was first proposed by Isaac Newton, and lately, with technological advances bearing such names as particle accelerators and supercolliders, science is getting closer and closer to finding this theory. Along with the knowledge, however, comes speculation and debate. Some scientists do not see the need for a grand unified theory, sometimes dubbed a "theory of everything". However, such a theory would offer insight into nature and the forces that shaped our lives. The search for a grand unified theory is an important and potentially valuable step for all humankind.
The Search Begins
The search began with Isaac Newton. He first proposed the idea that one great theory might exist that would link all the other known theories. This theory would provide one blanket statement that would describe everything in the entire universe, known and unknown. Other physicists, starting with Albert Einstein, began searching for this grand unified theory, which, through their love of acronyms, they affectionately called GUT. Some even started calling it a theory of everything, which led to the acronym TOE. They started with four basic forces: the gravitational force, which Newton had earlier found to explain gravity; the electromagnetic force, a linked theory of electricity and magnetism; the strong nuclear force, which holds the nucleus of the atom together; and the weak nuclear force, which is involved in the decay of atoms. In 1979, Sheldon Glashow, Steven Weinberg, and Abdus Salam combined the theories of electromagnetic and weak interactions into the electroweak theory (Elementary Particles). This was a gigantic step toward a GUT because it showed how two of the four main forces could be linked together with theories.
The Standard Model, General Relativity, And Quantum Mechanics
The Standard Model proposes a set of theories that explains the forces and the interactions between particles. These theories are basically accepted by physicists as accurate in describing the known universe. For most, however, even though they accept the Standard Model, they feel there is more to be discovered.
There are two main theories that are used to describe everything; general relativity, proposed by Einstein and describing gravity as a result of curvature of space-time, and quantum mechanics, which describes force in terms of little packages (Bartusiak).
Physicists are searching for a GUT to describe all the known and unknown with one unified equation. Marcia Bartusiak likens making these two theories compatible to "bowling with tiddlywinks" or "jump-starting a car with an eggbeater". To create a bridge between these two theories, some physicists have developed new hypotheses. One such hypothesis is called string theory.
String Theory
String theory proposes that at the "Planck length," ten to the power of -33 centimeters, smooth space-time dissolves into tiny vibrating loops called strings (Odenwald). These strings comprise the entire universe and everything in it, including space-time itself. The strings are identical, but depending on how they vibrate, they form everything in the universe: quarks, electrons, neutrinos, and all other particles (Taubes, A Theory of Everything).
The only catch to this theory is that it requires the strings to vibrate in ten dimensions (Kaku). In our known world, there are four dimensions: three of space and one of time. Physicists are just beginning to learn how to work in the extra six dimensions essential to string theory. They call this six-dimensional space "phase space", and roll the dimensions up into tiny objects called "Calabi-Yau compactifications" (Cole). With these six-dimensional compactifications, though, comes a multitude of four-dimensional solutions to the theory. The main goal of physicists now is to choose the correct one that corresponds to our universe.
String theory holds much potential for physicists, but it is complicated and confusing, and thus has driven many scientists out of the field. In a new variant on string theory, black holes and strings are shown to be fundamentally alike, evolving into one another during a crucial point in the theorems called a "phase change" (Taubes, How Black Holes). These phase changes also link the Calabi-Yau compactifications, previously thought to be distinct entities. So-called dark matter, or "sparticles" (short for super particles) also helps string theory (Kaku). Sparticles serve to reduce the number of four-dimensional possibilities to string theory and make it considerably easier for physicists to find the real-world equivalent to the hypothesis (Peterson, Strings and Webs).
Michio Kaku insists that ten dimensions are necessary for string theory, because no fewer than ten dimensions can account for both general relativity and quantum mechanics, but Stan Odenwald maintains that it is possible to build working GUTs within four-dimensional space-time.
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