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64 bytes removed ,  19:29, May 18, 2019
→‎General Relativity: "Euclidean geometry" is misleading, the universe has an overall stress-energy tensor which gives rise to empty space having a probably nonzero Gaussian curvature.
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General Relativity is a theory of gravity that is compatible with Special Relativity.  Einstein explains a thought experiment involving two elevators.  The first elevator is stationary on the Earth, while the other is being pulled through space at a constant acceleration of g.  Einstein realized that any physical experiment carried out in the elevators would give the same result.  This realization is known as the equivalence principle and it states that accelerating frames of reference and gravitational fields are indistinguishable.  General Relativity is the theory of gravity that incorporates Special Relativity and the equivalence principle.   
 
General Relativity is a theory of gravity that is compatible with Special Relativity.  Einstein explains a thought experiment involving two elevators.  The first elevator is stationary on the Earth, while the other is being pulled through space at a constant acceleration of g.  Einstein realized that any physical experiment carried out in the elevators would give the same result.  This realization is known as the equivalence principle and it states that accelerating frames of reference and gravitational fields are indistinguishable.  General Relativity is the theory of gravity that incorporates Special Relativity and the equivalence principle.   
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General Relativity is a mathematical extension of Special Relativity. GR views space-time as a 4-dimensional [[manifold]], which looks locally like [[Minkowski space]], and which acquires [[curvature]] due to the presence of massive bodies. Thus, near massive bodies, the geometry of space-time differs to a large degree from [[Euclidean geometry]]: for example, the sum of the angles in a triangle is not exactly 180 degrees. Just as in classical physics, objects travel along [[geodesic]]s in the absence of external forces. Importantly though, near a massive body, geodesics are no longer straight lines. It is this phenomenon of objects traveling along geodesics in a curved spacetime that accounts for gravity.
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General Relativity is a mathematical extension of Special Relativity. GR views space-time as a 4-dimensional [[manifold]], which looks locally like [[Minkowski space]], and which acquires [[curvature]] due to the presence of massive bodies. Thus, near massive bodies, the geometry of space-time differs to a large degree from that of other parts of the universe. Just as in classical physics, objects travel along [[geodesic]]s in the absence of external forces. Importantly though, near a massive body, geodesics are no longer straight lines. It is this phenomenon of objects traveling along geodesics in a curved spacetime that accounts for gravity.
    
The anomalous precession of Mercury's [[perihelion]] seems to support the Theory of General Relativity, though that is disputed on the[[Counterexamples to Relativity]] page.  Keep in mind that the precession in question is the ''"anomalous"''
 
The anomalous precession of Mercury's [[perihelion]] seems to support the Theory of General Relativity, though that is disputed on the[[Counterexamples to Relativity]] page.  Keep in mind that the precession in question is the ''"anomalous"''
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