String Theory: The Theory Of Everything

Coy 1 Physicists have come extremely far in their quest for a universal theory; their current candidate for a theory to occupy this role is the string theory. A universal theory is what physicists call a theory that is able to explain everything. One of the most popular proposals today is string theory (also known as the superstring theory). String theory is nothing new; it has in fact existed since the late 1960s (Gribbin 154n). Although it has been around for about forty years, it has only became what we know it as it is today in the early 1990s. Even though many people agree with string theory, not everyone does. Stephen Hawking helps the reader of his book, The Theory of Everything, understand why some people claim that string theory does not make sense and cannot exist. Before explaining string theory, it is important it's background be explained. In 1665, The Theory of Gravity originated (NOVA). The man that came up with this theory is Sir Isaac Newton (NOVA). It was here that gravity became the “first force to be understood scientifically.” (NOVA). Although Newton was the one to come up with the theory, he did not have a full understanding of how gravity worked (NOVA). Newton’s theory is that gravity is an instantaneous force (NOVA). This means that it works instantly (NOVA). This is explained in The Elegant Universe with narration from Brian Greene. A visual shows that if our sun was to all of sudden disappear, and then we would instantly lose our orbit and then spin off freely into space (NOVA). By what Newton says, gravity is the fastest force in our universe (NOVA). It wasn’t until many many years later that he was proven wrong. Albert Einstein was the man that proved Newton wrong. It was in the early 1900s that Einstein made his proposal of Newton’s mistake. Einstein claims that gravity does

Coy 2 not work instantly; instead it takes time for the gravitational pull the Sun has on the Earth to reach us. He supports this claim with showing that there is a “cosmic speed limit.” It is said the cosmic speed limit is that of the speed of light, nothing is able to overcome this (NOVA). Since Einstein claims that nothing is able to surpass this, gravity then in turn takes the same time to reach earth. A revised visual in The Elegant Universe shows what would happen if the sun was to disappear following Einstein’s theory. When the Sun disappears, the Earth would stay in orbit and will continue to have light and gravity. This is because Einstein also says that the speed of gravity travels in ripples across space at the speed of light (NOVA). As the last of the light from the Sun reaches Earth, so does it’s gravitational pull. When the last of the both of these pass the Earth, it would be then that we veer off our orbit and wander into space. Einstein gave the name to his theory General Relativity (NOVA). It was after this that Einstein then wanted to come up with a theory that could explain everything. Einstein's goal was to be able to combine the theory of gravity and electromagnetism. Electromagnetism is the combination of electricity and magnetism. A man named James Clark Maxwell brought the relationship between the two together. Although Albert Einstein spent most of his life trying to create a universal theory, he ran out of time when he died. It was in the 1930s that a new type of physics was introduced. The name of this one is Quantum Mechanics. Quantum mechanics created a problem with general relativity. In general relativity, it states that everything in the universe can be predicted with equations (NOVA). With quantum mechanics, it is said that this is not true; that the best we can do is predict the chances of one outcome of another. Although many contradictory claims were made in quantum mechanics, many new ones were made as

Coy 3 well. One of these new claims is that parallel universes exist. Although there were many good points made with quantum mechanics it lacked in explaining one very important thing, gravity. Both general relativity and quantum mechanics make the claim that they (the theories) exist everywhere (NOVA). The problem that arises is that we are unable to have two “everywheres.” A reason to unite these two theories, or to completely prove one another wrong never really existed until the discovery of black holes was found. Black holes asked a question that made people think, which was “do you use general relativity because the star is incredibly heavy or quantum mechanics because it's incredibly tiny,” (NOVA). An answer to this question was not one or another of the two, but it was both combined, creating something completely new. It was here that quantum gravity was found. Quantum gravity is “a theory that successfully merges quantum mechanics and general relativity.” Quantum gravity is also the backbone to string theory. It was in 1968 that the first indication of string theory emerged (Gribbin 154n). Two men, Gabriel Veneziano and Mahiko Suzuki, who were researchers at CERN, came across a mathematical formula used in the 19th century by Leonhard Euler (Gribbin 154n). It was with this formula that the two researchers were able to “describe the behavior of strongly interacting particles.” These mathematical formulas were then later taken by Yoichuro Nambu at The University of Chicago and turned into physics (Gribbin 154n). It was then later in 1974 that Joël Sherk and John Schwarz published a paper that showed how string theory is able to describe gravitational force. As John Schwarz says, “We felt strongly that string theory was too beautiful a mathematical structure to be completely irrelevant to nature.” Although this is was a break through, but it was never really noticed; the popularity of string theory was dying

Coy 4 off. Ten years later, string theory became popular again. The reason for this was because the new theory that was proposed, quantum chromodynamics (John H. Schwarz) was getting nowhere and John Schwarz and Mike Green came published another paper. This paper showed how string theory was able to explain “the existence of particles with builtin left-handedness.” Before any more is said about string theory, it is important to state what it is. String theory is the theory “that describes particles in terms of strings” (Lidsey 51). It is these strings that make up everything in our universe. From You and I to the stars, they are all made up of strings. A string is defined as energy as a string vibrating at different frequencies (NOVA and Lidsey 52). It is with these different vibrations that give each string its “identity”. There are two different types of strings, open and closed (these will be talked about into further detail later). These strings have “elastic like properties” (Lidsey 52). The open strings are tied down to our membrane, or universal “fabric”. The closed strings are not tied down to these membranes (NOVA). Strings have on property that is shared in every string. Each string is one dimensional (Glossary), the dimension of length. String theory’s popularity was beginning to die off. But before string theory began to die off in the early 1970s, a few different types of string theories were already devised. These are known as Type I theory and Type II theory (Gribbin 170). Although Type I and Type II had many differences, there was one major difference. This was that Type I consists of open strings while Type II consists of closed strings (Gribbin 167-171). An open string is a string that is attached to the “fabric” of space and our universe. Type II has closed string, which are not attached to this “fabric” (Gribbin 167-171). The most

Coy 5 common type of closed string is a graviton. A graviton is the “smallest bundle of the gravitational force field” (Susskind 387). The special thing about a graviton and other type of closed strings (such as photons) is that they are not attached to the “fabric” (NOVA). Since they are not attached, they then become massless (John H. Schwarz) and then are able to float around freely. Since they can float around freely, this means (in theory) that other “parallel universes” can feel them. The easiest way to explain a “parallel universe” is through a visual. In Figure 1-1 (I still have yet to find a picture online, so I am thinking I will just photocopy a picture from one of my books), it is shown that it is possible for multiple universes to co-exist. One question that is always brought up is; why can’t we see it (“it” being the other universes). The answer to this question is fairly simple. When going back to Type I, it is explained that a string is attached to the “fabric” of our universe. We (people) are also composed of these open strings, and then are bound to our “fabric”. Each universe has its own “fabric”. Since we (our open strings) are bound to our “fabric”, that means that it would be impossible to see anything on another “fabric”, even if it is less than an inch away. This is where Type II comes into play. Since in Type II, the closed strings are NOT bound to our “fabric”, they are able to float around freely. As this is explained in The Elegant Universe, gravitons are able to travel from one universe to another. This is because they are not bound to the “fabric”, unlike open string. At this time, these two theories, along with another one called the heterotic theory, were battling among each other to be the correct version of string theory. This went on for some time until a revolutionary proposal was made to end this.

Coy 6 In 1995, Edward Witten, a theoretical physicist, made a proposal that got rid of these many different theories. His proposal was called the M-Theory. Witten claimed that these different theories were not different, they were in fact the same, and they were just being looked at in different ways. M-Theory is the theory that he came up with; it was a combination of Type I, Type II and the Heterotic. Along with the combination of these theories, there was also the proposal of there being eleven dimensions. A dimension is, “an independent axis or direction in space or spacetime” (Glossary). What was (and still is) accepted is that there are only the four dimensions, the three space and the one time. M-Theory is accepted by many notable physicists, but not everyone agrees with it. Stephen Hawking, in his book, The Theory of Everything, he explains the reasons that are given from string theory critics to attempt to prove how it does not exist (Hawkings 159). Hawking once again brings up the point that we cannot see these other universes, so they must not exist. Another reason is that of the extra dimensions (Hawking 158). Hawking explains how if these other dimensions did exist, it would not be possible for life, as we know it to exist, even in other universes (Hawking 159). An opposing argument is that it is unreasonable to make this claim. Since we are never going to be even to look into another universe. We can only make assumption, and who is to say that the same laws of physics that exist in our universe exist in others as well. The same is to be said about string theory. James E. Lidsey makes this very clear in his book The Bigger Bang, “ This picture of particles as strings is very appealing. We should emphasize, however, that the superstring concept is just a theory at this stage.” (Lidsey 52). Hawking then someone

Coy 7 restates this in his book as well, but with a bit more support. Hawking makes three suggestions about a “unified theory of everything.” They are… “ -

There really is a complete unified theory, which we will someday discover is we are smart enough There is no ultimate theory of the universe, just an infinite sequence of theories that describe the universe more and more accurately There is no theory of the universe. Events cannot be predicted beyond a certain extent but occur in a random and arbitrary manner.” (Hawking 160)

Coy 8 Works Cited "Glossary". NOVA. February 26, 2009 . Gribbin, John. The Search for Superstrings, Symmetry, and the Theory of Everything. Boston: Little, Brown, 1998. Hawking, Stephen. The Theory of Everything. City: New Millennium Press, 2002. Lidsey, James. The Bigger Bang. Cambridge: Cambridge University Press, 2000. NOVA - The Elegant Universe. Dir. Joseph Mcmaster. Perf. Michael B. Green, Joseph Lykken, Maria Spiropulu. DVD. Wgbh Boston, 2004. Schwarz, John. "John H. Schwarz". February 26, 2009 . Susskind, Leonard. The Cosmic Landscape. Boston: Little, Brown and Co, 2006.