Introduction to M-theory
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| String theory |
|---|
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| Fundamental objects |
| Perturbative theory |
| Non-perturbative results |
| Phenomenology |
| Mathematics |
In non-technical terms,
Background
In the early years of the 20th century, the
In the 1980s, a new mathematical model of theoretical physics, called string theory, emerged. It showed how all the different subatomic particles known to science could be constructed by hypothetical one-dimensional "strings", infinitesimal building-blocks that have only the dimension of length, but not height or width. These "strings" vibrate in multiple dimensions and, depending on how they vibrate, they might be seen in three-dimensional space as matter, light or gravity. It is the vibration of the string that determines whether it appears to be matter or energy, and every form of matter or energy is the result of the vibration of strings.
However, for string theory to be mathematically consistent, the strings must be in a universe of ten dimensions. This contradicts the experience that our real universe has four dimensions: three space dimensions (height, width, and length) and one time dimension. To "save" their theory, string theorists therefore added the explanation that the additional six dimensions exist but cannot be detected directly. In essence, the idea was that the extra dimensions existed, but they were "curled up" to be so small that they could not be observed. The technical term for this is compactification. Physicists speculated that the compactified dimensions took the shape of mathematical objects called Calabi–Yau manifolds.
String theory as described above ran into a problem: another version of the equations was discovered, then another, and then another. Eventually, five major string theories were developed. The main differences between the theories were principally the number of dimensions in which the strings developed, and their characteristics (some were open loops, some were closed loops, etc.). Furthermore, all these theories appeared to be workable. Scientists were not comfortable with five seemingly contradictory sets of equations to describe the same thing.
Speaking at the string theory conference at the University of Southern California in 1995,
Status
M-theory is not complete, but the mathematics of the approach has been explored in great detail. However, so far no experimental support for the M-theory exists.[1] Some physicists are skeptical that this approach will ever lead to a physical theory describing our real world, due to fundamental issues.[6]
Nevertheless, some
One feature of M-theory that has drawn great interest is that it naturally predicts the existence of the
See also
References
- ^ a b c Wolchover, Natalie (December 2017). "The Best Explanation for Everything in the Universe". The Atlantic. Archived from the original on 15 November 2020. Retrieved 7 February 2018.
- ^ a b "Physicists and Philosophers Debate the Boundaries of Science | Quanta Magazine". Quanta Magazine. 16 December 2015. Archived from the original on 15 November 2020. Retrieved 7 February 2018.
- ^ Devlin, Hannah (5 July 2017). "Tying loose ends? Gravitational waves could solve string theory, study claims". The Guardian. Archived from the original on 15 November 2020. Retrieved 7 February 2018.
- ^ "University of Southern California, Los Angeles, Future Perspectives in String Theory, March 13-18, 1995, E. Witten: Some problems of strong and weak coupling". Archived from the original on 2020-11-15. Retrieved 2017-04-08.
- S2CID 17432791.
- Joe Polchinski.
Further reading
- ISBN 978-0-375-70811-4.
- Greene, B. (2004). ISBN 978-0-375-41288-2.
- Miemic, A.; Schnakenburg, I. (2006). "Basics of M-theory". S2CID 98007313.
- ISBN 978-1-59257-702-6.
- ISBN 978-0-618-55105-7.
- ISBN 978-0-465-09275-8.
External links
- The Elegant Universe – A three-hour miniseries with Brian Greene by NOVA (original PBS Broadcast Dates: October 28 and November 4, 2003). Various images, texts, videos and animations explaining string theory and M-theory.
