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Spacetime and GravitySpacetime and Gravity
Albert Einstein (1879 – 1955)Swiss/American physicist
Einstein’s Second RevolutionEinstein’s Second Revolution
• Gravity is the primary topic of the general theory of relativity.• What is the equivalence principle?• What is spacetime?
Isaac Newton saw gravity as a mysterious “force.”
Einstein theorized that the “force” of gravity arises from distortions of space (or spacetime) itself!
spacetime…the 4-dimensional combination of space & time that forms the very fabric of the Universe
Matter Distorts SpacetimeMatter Distorts Spacetime
• Matter distorts spacetime like weights on a taut rubber sheet.• The greater the mass, the greater the distortion of spacetime.
The Equivalence Principle The Equivalence Principle
For Einstein• intuition -- all motion should be relative• his equivalence principle: The effects of gravity are
exactly equivalent to the effects of acceleration.
Weak equivalence principleWeak equivalence principleIn a small region of space, the physical effects of a gravitational field as perceived by an observer are indistinguishable from the physical effects reported by another observer accelerating at a constant rate in the absence of a gravitational field. (A. Zee, p. 18)
Working with: Time Lines in SpaceTimeWorking with: Time Lines in SpaceTime
http://physics.syr.edu/courses/modules/LIGHTCONE/events.html
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