Significance of String Theory

The debate on whether string theory has any credence in the physics community has raised harsh criticisms from both sides of the argument for more than thirty years. Despite the criticisms string theory is alive and thriving in the physics community, and is regarded by some physicist as being the only candidate for a theory of everything (Kaku 17). Though string theory is regarded by some physicist as not having any predictive power and no real world applications, it still has the interest of many young physics students. The interest associated with string theory is driven by Einstein’s dream of one day discovering a theory of everything. “Theory of everything” is a bold statement. According to Lisa Randall when people talk about a theory of everything it does not mean that we will know why we wake up every morning and “brush our teeth” for instance, it just means that we will know an awful lot about physics and the world around us (Randall Int.). Michio Kaku uses the analogy of chess and says that once we find this “theory of everything” we will not be “grandmasters” of the game. We will have just learned how the pieces move (Kaku Int.). String theory should be taught along with the standard model of particle physics so students can keep up with the physics of the 21st century. Students should be offered the opportunity to decide for themselves if string theory has any merit. String theory has lead to new insights in addressing the problems associated with the standard model of particle physics. These new theories addressing the problems associated with the standard model have sprung up in light of studying string theory, and according to Randall these new theories can be tested experimentally and have real world applications. (Using the P.B.S. video “The Elegant Universe” as my primary source I hope to convince you as to whether string theory has any credence in the physics community.)

A “theory of everything” is what many physicists are hoping to find. Our universe and everything in it is governed by four fundamental forces of nature (electromagnetic, gravity, strong, and weak). People are familiar with the force of gravity, it is what keeps the planets revolving the sun and keeps our feet planted safely on earth. Electromagnetism is complicated in some respects, but we can think of it as the force a positively charged particle is exerting on a negatively charged particle. The strong force is what keeps protons and neutrons tightly bound to the nucleus of an atom. The weak force is responsible for nuclear radiation. The unification of these four forces of nature is what many physicists refer to as a “theory of everything.” Electromagnetism and the weak nuclear force can be combined into one force using quantum mechanics and this is called the Electroweak theory. Quantum chromodynamics is a quantum theory of the strong nuclear force. The force of gravity embodies Einstein’s general relativity and Newton’s laws of gravity. Many physicists believe that these four forces are manifestations of one grand force that at some point was separated into four different forces. Thus a “theory of everything” would be an all encompassing theory of these four fundamental forces of nature (Greene).

The standard model of particle physics encompasses three of the four forces (electromagnetism, strong, and weak), but excludes gravity. Gravity is excluded from the standard model of particle physics because the force of gravity on the subatomic scale is negligible. Though the standard model is the greatest triumph in the physics since the dawn of time it can not address all the questions concerning our universe (Greene). For example, the standard model does not address “how the values of the free constants… are chosen in nature” (Smolin 13). Free constants are the experimentally tested values that correspond to a given theory. An example of a free constant that most people are familiar with is G, the gravitational constant associated with Newton’s force of gravity equation F=G*(m1*m2)/r^2. This equation says that given a mass (m1) separated by a distance (r) from another mass (m2) , we can calculate the gravitational force exerted on one mass to the other. The gravitational constant has an experimentally tested value of 6.67259E-11. Lee Smolin is addressing why nature chooses to give us this value of instead of another. Another problem would be that of quantum mechanics of which the standard model is based on. The fact that quantum theory tells us that a particle “can be anywhere until we measure it” is a hard pill to swallow. This means that “our observation in some sense determines its state” (Smolin 6). This idea is quite unsatisfying and many physics believe that there must be another underlying principle on which quantum mechanics operates (Smolin 6). Einstein himself believed that quantum theory was overshadowing a more fundamental theory which explains quantum theories predictions of the subatomic world (Kaku 160).

Our observations as human beings should not govern our physical reality. Before there was intelligent life to observe these fundamental particles (like the electron) the particles must have been there, thus our observations should not hinder the outcome of nature. The laws that govern nature should be the same whether we are here to observe them or not. For these reasons many physicists believe that there is a more fundamental theory governing quantum mechanics (Smolin 6-8).

Presently in the world of physics the force of gravity, using Einstein’s theory of General Relativity governs all massive objects such as planets, stars, etc., and quantum mechanics using the other three forces, governs the microscopic world of atoms, subatomic particles, etc. As Brian Greene suggests in the Elegant Universe these two theories need to be “molded” together in order to come up with this “theory of everything.” The law associated with the strength of gravity tells physicists that the force of gravity becomes extremely large on distance scales known as the Planck length (10^-33cm). At this length the force of gravity can not be ignored. But as was mentioned earlier gravity and Einstein’s equations are the physics of large objects. At these distances Einstein’s equations are not applicable. Many physicists refer to a theory of gravity at this level as a quantum theory of gravity (Randall 278-79). Brian Greene gives a great visual picture of the Planck length by saying “if our solar system represented the size of an atom this distance would be about the size of a tree on earth.” The physics of the very small (quantum mechanics) breaks down even at this level and gives “unpredictable” results (Greene). Thus a more fundamental theory that is consistent and predictable at all sizes is needed to explain nature. Greene, Michio Kaku, and many other physicists believe that string theory is the theory that might encompass all of nature’s phenomena.

String theory makes some outlandish, unintuitive claims about the world we live in. The theory suggests that the fundamental particles of nature are nothing more than vibrating bands of energy (Greene). Instead of treating these fundamental particles as point particles which has been done throughout time, string theorist are treating these particles, such as the electron, as vibrating strands of energy (Polchinski). This is an inherently different way of treating fundamental particles of nature. Though this ideas is inherently different way of viewing nature, Lisa Randall suggest that “string theory does have several remarkable features that lend credence to this promising picture” of nature (278). One of these remarkable features happened when John Schwarz and Joel Scherk found that Einstein’s equations fell directly out of string theory (Kaku 192-93). The fact that Einstein’s equations which where developed more than a half a century before fell directly out of this new theory must lend string theory some credence. Another remarkable feature of string theory happened in 1984 (the start of the “Superstring Revolution” according to Randall) when John Schwarz and Michael Green proved that string theory could incorporate all the “particles and forces” of the well respected standard model (Randall 291). “Superstring Revolution” is definitely a good description. The promises of being a quantum theory of gravity along with being able to incorporate all the “particles and forces” of the standard model made string theory seem like the sweetest thing to hit physics since the calculator. Though these features of string theory made a definite impact on the physics community, there were some stipulations that came with embracing this new revolution in physics.

The problem with string theory is that its predictions involve probing distances of 10^-33cm(the size of these strings) and energy scales far greater than any modern piece of technology could account for (Randall 278). This would leave experimental testing of this new found glory quite difficult. As Dan Vergano addresses in his article, without experimental evidence string theory will be “hanging by a thread.” Another big stipulation for physicists is that these strings need to exist in ten dimensions (Odenwald). Where are the other dimensions? String theorists believe that these extra dimensions are “rolled up” or are compacted into to the Planck length safely hidden from our reach (Greene). Thus many critics of string theory believe that experimental validity of these extra dimensions is beyond our grasp, and perceptions for that matter.

Critics of string theory say that it is “impossible to prove, period” (Kaku). The main critics of string theory that are incorporated into this article are Peter Woit and Lee Smolin. Peter Woit says string theory has no connection with the real world and there has not been one experiment to prove otherwise, “nor are there any prospects for this situation to change soon” (Woit 162-73). Lee Smolin says there does not exist any complete formulation of the theory and that they are nothing more than conjectured theories (theories that have not been formally proved) (Smolin 179). Physicist like Peter Woit and Lee Smolin believe that many physics students are wasting much of their time with just string theory and that these efforts should be concentrated on something that can actually be proven.

If the above statements are true, why has string theory become so popular in the physics community? In fact, string theory is popular enough that “string theorists are still being hired by universities in substantial numbers” and “graduate students are still flocking to the field” (Carroll). The concepts governing many aspects of string theory make it worth while. String theory has presented many new ways to view nature and what it actually may be made up of. These ideas and different ways of viewing our world has lead to countless new and fascinating advancements in physics. A few examples are new mathematics, brane physics, supersymmetry, multiverses, and alternative extra dimensional theories (Randall 277-324).

With all this hype on string theory, of course physicist are trying to work on ways of verifying its predictions experimentally. The Large Hadron Collider (L.H.C.) which turns on sometime this year might be able to lend some indirect evidence of the theory. The L.H.C. is a largest particle collider ever to be built which will send beams of protons approaching the speed of light toward each other. String theorists believe that the L.H.C. might produce new particles that should exist according to the string theory (Kaku). As Michio Kaku states indirect evidence is nothing to turn your nose up at. Many theories have been addressed indirectly. For example, John Michell hypothesized the existence of black holes in 1783, Michell’s idea regarding this “dark star was ridiculed for centuries” according to Kaku’s article. “Since a dark star is invisible, by definition, it was impossible to ever verify Michell's theory” (Kaku). Now we know that black holes exist through the indirect evidence of their gravitational effects and jets streaming out the top and bottom of a promising candidate. Yet another example Kaku uses of how theories that are “untestable” eventually become testable. “The physicist Wolfgang Pauli introduced the concept of the neutrino in 1930, a particle so elusive it could pass through a block of solid lead the size of an entire star system and not be absorbed. Pauli said, "I have committed the ultimate sin; I have introduced a particle that can never be observed." It was "impossible" to detect the neutrino, so it was considered little more than science fiction for several decades. Yet today we can produce beams of neutrinos” (Kaku). Peter Woit and Lee Smolin’s claim that string theory could never be proved, but throughout time many outlandish ideas have been proved to be correct.

Throughout history many ideas presented by physicist have been considered dismissible and sometimes even crazy. With respect to the other side of the argument, many crazy physics ideas turned out to be dead ends. Lisa Randall addresses string theory from the “middle ground” which is how physicists and students of physics should address string theory. Her conclusion on the credence of string theory as a valuable or significant physical theory is the correct approach which all physicists should embrace.

“We are trying to address difficult questions, and they will take time to answer. But this is an exciting time, and despite (or perhaps because of) the many unsolved problems, there is good reason to be optimistic. Physicists now have a better grasp of many consequences of both particle physics and string theory, and open-minded physicists today stand to profit from the achievements of both schools” (Randall 302).

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Work Cited

Odenwald, Sten. "What if string theory is WRONG?" Astronomy Feb 2007: 30-34. EBSCOhost. UCDHSC, Auraria Lib. 2 Jul. 2007<http://www.epnet.com/>.

Carroll, Sean. "Not Dead Yet." New Scientist 19 May 2007: 54-54. EBSCOhost. UCDHSC, Auraria Lib. 2 Jul. 2007<http://www.epnet.com/>.

Kaku, Michio. "Will We Ever Have a Theory of Everything?" New Scientist 18 November 2006: 62-65. EBSCOhost. UCDHSC, Auraria Lib. 2 Jul. 2007<http://www.epnet.com/>.

Vergano, Dan. "Hanging on by a Thread?" USA Today 19 September 2006. EBSCOhost. UCDHSC, Auraria Lib. 2 Jul. 2007<http://www.epnet.com/>.

Smolin, Lee. The Trouble with Physics: The Rise of String Theory, the Fall of a Science, and What Comes Next. New York: Houghton Mifflin Company, 2006.

Woit, Peter. Not Even Wrong: The Failure of String Theory & the Search for Unity in Physical Law. New York: Basic Books, 2006.

The Elegant Universe. Dir. Joseph McMaster. Perf. Brian Greene. 2003.

Randall, Lisa. Warped Passages: Unraveling The Mysteries of The Universe's Hidden Dimensions. New York: HarperCollins, 2005.

Polchinski, Joseph. "All Strung Out?" American Scientist Jan/Feb 2007: 4,72-75. EBSCOhost. UCDHSC, Auraria Lib. 2 Jul. 2007<http://www.epnet.com/>.

Randall, Lisa. Interview. 26 Feb. 2006. Bell, Art. Coast to Coast AM. Premier Radio Networks. 26 Feb. 2006.

Kaku, Michio. Civilization, Space & String Theory. 22 Jan. 2006. Bell, Art. Coast to Coast AM. Premier Radio Networks. 22 Jan. 2006.