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FQXi BLOGS
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TOPIC: What if string theory is wrong? asks Moataz Emam
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As physicists wrangle over whether string theory truly represents reality, FQXi invited Moataz Emam of Clark University to ponder over the fate of string theorists like himself, if string theory turns out to be wrong.
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From Moataz Emam:
As a string theorist, I am often asked an uncomfortable question: “What will you do if someone proves that subatomic particles cannot possibly be made of strings?”
What will happen to my career and life’s work if string theory is falsified? Is it worth the risk? These are certainly valid questions. My answer is that even if string theory is proved “wrong,” it will still survive, and possibly break away from mathematics and physics to form a new and separate academic discipline. Bear with me.
String theory already occupies a special niche in the history of science. It’s our best bet for finding a theory of quantum gravity, as FQXi’s Renata Kallosh of Stanford University explains in this article connecting string theory with cosmology , as well as for finding a theory of everything. However, it is also the only theory of physics with no experimental backing that has managed to not only survive, but also become “the only game in town” (to quote Nobel Laureate Sheldon Glashow).
This lack of experimental support has been seized upon by string theory’s vocal critics, notably FQXi’s Lee Smolin, of the Perimeter Institute, and Columbia University’s Peter Woit. In his book, “The Trouble with Physics,” Smolin points out that this “faith” in the string hypothesis has affected funding and hiring policies in a negative way, boosting the theory’s prominence disproportionately compared to other approaches to quantum gravity. Although there are many counterarguments to be made, it seems that string theory does receive more hype than it deserves if evaluated solely on its applicability to nature.
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In fact, string theory has so far failed to conform to the falsifiability criterion laid down for a scientific theory by Karl Popper. It might be argued that this situation is temporary—eventually technology will catch up with string theory. This hope is what saves string theory from being little better than astrology or creationism.
But back to the original question: What if it turns out that string theory does not describe nature? Will I, and other string theorists, be out of a job? My answer is no, and here’s why.
String theory has provided us with a wealth of possible solutions for the state of the universe that arise when we try to reduce the ten-dimensional string theory to the four spacetime dimensions we are familiar with. We have such a plethora of outcomes that they collectively form a “string theory landscape” of different theoretical descriptions of possible universes. The lack of experimental results to guide us through the vast string landscape leaves string theorists with no choice but to systematically explore all of it!
These explorations, even within theories that we already know are not related to nature, have resulted in the discovery of deep and elegant mathematics. Mathematicians today work in parallel with string theorists to explore the frontiers that the latter have opened. Aside from advancing abstract mathematics, the discovery of the ADS/CFT conjecture provides hope that results within a (nonphysical) perturbative string theory may be transformed to a mathematically dual (but physical) nonperturbative theory, such as quantum chromodynamics. If true, this duality would be a major breakthrough, and might by itself guarantee the survival of string theory in some form, even if falsified by experiment.
So even if someone shows that the universe cannot be based on string theory, I suspect that people will continue to work on it. It might no longer be considered physics, nor will mathematicians consider it to be pure mathematics. I can imagine that string theory in that case may become its own new discipline; that is, a mathematical science that is devoted to the study of the structure of physical theory and the development of computational tools to be used in the real world. The theory would be studied by physicists and mathematicians who might no longer consider themselves either. They will continue to derive beautiful mathematical formulas and feed them to the mathematicians next door. They also might, every once in a while, point out interesting and important properties concerning the nature of physical theory which might guide the physicists exploring the actual theory of everything over in the next building.
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Until experimentalists prove otherwise, Moataz Emam considers himself to be a physicist. His article, “So what will you do if string theory is wrong?” appears in July’s issue of the American Journal of Physics.
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What if it was shown that there could not be small scale extra dimensions of space?
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The picture of the bit of string covers the text.
For once I would like to see thinkers start without the assumption that matter exists. There is no proof for it, why base your science around it?
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String theory has gotten mathematicians and physicists to move away from the archaic idea that reality consists of the 3 Euclidean dimensions plus time. This belief has the same basic origin as the long discredited beliefs that the earth was flat and that the sun orbited the earth instead of the other way around.
If length. width and height are the only variables or dimensions of reality then all of reality could be explained with those variables. Scientists have to get past the notion that the eyes can perceive everything there is to perceive about reality.
We cannot see gravity nor can it be explained by length, width and height. Gravity can only be explained through the existence of dimensions that cannot be detected with the eyes.
The eyes can only detect a very narrow range of electromagnetic radiation and each eye sends a flat image to the brain. The idea that reality is 3-dimensional is an interpretation made by the brain.
The term "string" implies something composed of matter. "line of force" would make more sense.
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Dr. Emam,
I wonder if you find compelling the suggestion, touched on by Max among others, that all consistent mathematics describes some aspect of material reality, be it in this region of the multiverse or another?
If so, the fact that string theory is internally consistent would guarantee its relevance to nature at some level, whether we currently know where it "fits" or not.
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Hi Zeno,
We're trying to work out why the images are covering the text for some people and not for others. Can you tell us which browser, version, and operating system you are using?
Also, do you see the problem on the main blog page (http://www.fqxi.org/community/blogs), or the page for the individual blog entry (http://www.fqxi.org/community/forum/topic/223)? Or both?
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William Orem
I find the prospect you describe to be absolutely fascinating. It certainly is supported by experience. Almost (but not quite) every mathematical abstraction and advancement in the last few hundred years has found an application in physics (and/or string theory). Proving such an idea, however, is an entirely different matter. There does remain interesting questions such as: Is consistency enough for a mathematical theory to be a representative of some side of nature? I don't know. What about incompleteness (in the Godelian sense)? How does that affect the applicability of a mathematical theory to nature? No clue either. But it certainly is fun to just think about it :-)
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