Understanding Relativity: A Quick Overview of General and Special Relativity

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SUMMARY

This discussion provides a concise overview of general relativity (GR) and special relativity (SR), highlighting their foundational principles. Special relativity is defined by two postulates: the universality of physical laws across inertial frames and the constancy of the speed of light. General relativity, formulated by Einstein, describes gravity as the curvature of space-time. Both theories serve as predictive models, though they are acknowledged to be incompatible with quantum mechanics, prompting ongoing research into theories like string theory and loop quantum gravity.

PREREQUISITES
  • Understanding of Lorentz interval invariance in special relativity
  • Familiarity with the concept of non-Euclidean geometry
  • Basic knowledge of Einstein's theories of relativity
  • Awareness of quantum mechanics and its relationship with general relativity
NEXT STEPS
  • Study the implications of Lorentz transformations in special relativity
  • Explore the mathematical framework of non-Euclidean geometry in general relativity
  • Research the principles of string theory and loop quantum gravity
  • Examine experimental tests of general relativity and their limitations
USEFUL FOR

Students of physics, researchers in theoretical physics, and anyone interested in the foundational concepts of modern physics and the interplay between relativity and quantum mechanics.

TheShapeOfTime
Can anyone give me a quick overview of relativity, general relativity and special relativity? What does general and special relativity prove?
 
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SR has two postulates:
-The laws of the universe are the same regardless of your intertial frame of reference.
-The speed of light is constant.

GR is Einstein's gravity, modeling gravity as a curvature of space-time.

The implications of both are pretty broad.
 
TheShapeOfTime said:
Can anyone give me a quick overview of relativity, general relativity and special relativity? What does general and special relativity prove?

Special relativity can be understood as the invariance of the Lorentz interval for all observers. Special relativity suggests that as the only quantity that is invariant for all observers, the Lorentz interval deserves further study. In special relativity, distance/space, is not invariant, differently moving observers measure objects as having different lengths. Time is also not an invariant quantity, clocks moving along different paths will not agree when they meet up. Only the Lorentz interval is invariant.

General relativity probes the geometry of the Lorentz interval, and finds that it is not Euclidian. Space-time is a non-Euclidian manifold, it can be regarded as being "curved", much as the surface of the Earth.
 
And I can't help mentioning that neither theory proves anything -- they are models which can use to predict what an experiment will do. If a model accurately explains all known experiments (SR & GR do), then a model is considered valid. It is always possible, however, that there will one day be an experiment which is not adequately explained by the theories, and the theories will be shown to be wrong in at least some situations.

We already know GR must be "wrong" in the subatomic domain, because its results are incompatible with those of quantum mechanics. Theories like string theory and loop quantum gravity aim to merge quantum mechanics and general relativity into a single theory with greater predictive power than either theory alone.

- Warren
 
chroot said:
We already know GR must be "wrong" in the subatomic domain, because its results are incompatible with those of quantum mechanics.

Or we counld say we already know quantum theory is incorrect because its results are incompatible with GR!
 
Thanks for all your relies! I think I'm beginning to understand it better now.
 
TheShapeOfTime said:
Thanks for all your relies! I think I'm beginning to understand it better now.
Great. When you will start to think that you don't understand it anymore that means you have started to understand a bit of GR.

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