String Theory
By Jennifer Grigsby
I. Introduction
String theory was developed in hopes of being a theory of everything. If it’s right, it could potentially answer all questions about the universe. Gabriele Vineziano laid the basis for the idea of string theory was laid in 1968. From that point on, physicists made discoveries that all converged into this one theory. String theory, if correct, perfectly unifies general relativity and quantum mechanics.
Video 1: a brief summary of string theory
http://www.youtube.com/watch?v=_B0Kaf7xYMk
II. Laying Foundations
In the late 1600’s, Isaac Newton unified the solar systems and the earth by discovering gravity. He figured out that the same force that held together the planets was also responsible for making apples fall to the ground. Albert Einstein proved Newton wrong. Newton thought that the sun (the center of our solar system) reaches out and grabs planets with its gravitational pull, keeping them in orbital. Contradicting Newton’s theories, Einstein said that time and space are bound together (spacetime). The planets follow curves in spatial “fabric” created by the sun. If a cosmic catastrophe were to occur (where the sun disappears/vaporizes), Newton believed that the planets would instantaneously shoot off across the universe because the sun was no longer keeping them in line; whereas Einstein believed that the curve in spacetime fabric would disappear, and would make a ripple in the fabric. In Einstein’s scenario, the Earth wouldn’t feel the effect of the sun’s disappearance until the ripple reached it. By solving numerous mathematical equations, he concluded that light and gravity take the same amount of time to travel from the sun to the earth. So basically, he corrected Newton’s concept of gravity and made his own new version of it. This new picture of gravity (which included other examples) was called general relativity.
Earlier, James Clerk Maxwell had unified electricity with magnetism which resulted in a force called electromagnetism. Einstein wanted to unify general relativity with electromagnetism to form a master equation that could describe everything, but he didn’t know how he could because there was a huge difference in strength: electromagnetism is way stronger than general relativity.
A new group of young scientists came into the picture and made Einstein’s and Maxwell’s work seem useless. These physicists made the theory of quantum mechanics: described how subatomic particles interacted. Quantum mechanics was a radical theory that crushed all previous ways of looking at the universe. The laws of the quantum world are way different than what we know and live daily. There’s never certainty. This new theory explained the 3 forces in the microscopic realm: electromagnetism, the strong nuclear force, and the weak nuclear force. But no one could figure out how the 4th major force, gravity (and Einstein’s theory of general relativity) fit in with it. Essentially, no one could figure out how to put quantum mechanics (little) and general relativity (big) together, but they all knew somehow they had to fit because they all exist in the same universe.
Through Schwarzschild discovery of black holes, scientists began to find the key to a theory of everything. At the center of a black hole is an entire star crushed into a tiny speck. Does that mean it’s big, falling under the theory of general relativity, or does that mean it’s small, falling under the theory of quantum mechanics? Both theories have to work, which means there must be something that unifies these two separate parts of the laws of the universe. But the problem was, nobody could figure out how these two related, because they each came up with separate answers and wouldn’t mesh.
III. Development of the “Theory of Everything”
String theory states that every particle (of matter, force, etc.) is made up of tiny vibrating strands of energy, called strings. These strings “wiggle” and vibrate in different ways which determine the particle’s properties, such as mass and charge.
Figure 1: What strings are supposed to look like. Top left corner = the 4 main forces: gravity, electromagnetism, the strong nuclear force, and the weak nuclear force.
In 1968, a young Italian physicist named Gabriele Vineziano accidently found 200-year-old equations written by Leonard Boyler that described the strong nuclear force. Leonard Susskind, and American physicist, took those equations and manipulated them. He ended up noticing something peculiar within his math, and he developed the initial concept of the “string” and string theory.
String theory was, at this point, rather confusing and unexplained. It required 10 dimensions, which was inconceivable. In 1973, John Schwarz decided that strings unite the theories of general relativity and quantum mechanics, but his work had anomalies (mathematical inconsistencies). In 1984, he and Michael B. Green continued the search for the possibility of a theory of everything, and realized that their theory was free of anomalies and could encompass all four forces (gravity, electromagnetism, strong nuclear force, and weak nuclear force). This discovery fulfilled Einstein’s dream.
There were 5 different string theories, which was kind of embarrassing for string theorists. But Ed Whitten solved this problem. He discovered that these 5 different theories were really just 5 different ways of looking at the same thing, and thus he created M theory (nobody knows what the M stands for, he says it can be magic, mystery, matrix, or even murky). Now there must be 11 dimensions.
Figure 2: String theory demands 11 dimensions; 6 of the ones we can’t see are supposedly curled up into something that looks like this. (4 of the other dimensions we know: 1 in time, and 3 in space. The 11th dimension was conjured up by Whitten in his M theory, after this image was accepted by string theorists.)
String theory has an inability to experiment and make observations upon, so as far as we know, it can’t be proven. However, it remains permanently safe because it can’t be proven wrong.
IV. Impact on the World/Humanity
“The discovery of the T.O.E. [theory of everything]—the ultimate explanation of the universe at its most microscopic level, a theory that does not rely on any deeper explanation—would provide the firmest foundation on which to build our understanding of the world. Its discovery would mark a beginning, not an end. The ultimate theory would provide an unshakable pillar of coherence forever assuring us that the universe is a comprehensible place.” (Greene, 2003)
String theory could be the foundation of many scientific breakthroughs to come. With the knowledge it could potentially provide, we could make advances in technology and virtually anything else. After all, it explains the basis of everything.
V. Journal Article Review
Unifying general relativity with quantum mechanics into a theory of quantum gravity has been the challenge of many scientists over the years, and string theory is the closest they've gotten. General relativity was thought to have covered all there was to know about gravity, but it was flawed because it didn't apply to the quantum level, and so was the problem with quantum mechanics alone. Black holes were the key to the creation of string theory. At the center of a black hole is an entire star crushed into a tiny speck. Nothing, not even light, can escape a black hole. So since at the time there were 2 separate theories of the universe, which one would black holes be classified as? There couldn't be 2 separate universes, because black holes unified everything into one, as well as they unified the quantum world with the idea of general relativity - both applied.
References:
Greene, B. (n.d.). NOVA | The Elegant Universe | A Theory of Everything? | PBS. PBS: Public Broadcasting Service. Retrieved February 13, 2011, from http://www.pbs.org/wgbh/nova/elegant/everything.html
Maldacena, J. (1996, August 20). Black Holes in String Theory. arxiv.org. Retrieved February 18, 2011, from arxiv.org/PS_cache/hep-th/pdf/9607/9607235v2.pdf
Mcmaster, J. (Director). (2003). NOVA - The Elegant Universe [Motion picture]. US: PBS.
String Theory - (2 Minutes). (2007, March 13). YouTube. Retrieved February 17, 2011, from http://www.youtube.com/watch?v=_B0Kaf7xYMk
Pictures:
Kadimi, A. (2010, March 25). The impossible says i'm possible. Blogger. Retrieved February 17, 2011, from http://travelthroughtime-possible.blogspot.com/
Testing String Theory? How Real Science Progresses « The Skeptical Teacher. (2010, September 16). The Skeptical Teacher. Retrieved February 17, 2011, from http://skepticalteacher.wordpress.com/2010/09/16/testing-string-theory-how-real-science-progresses/
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