Albert Einstein

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Albert Einstein

• A New Vision of the Cosmos

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Einsteins Vision

• Space Time Spacetime
• Four dimensions 3 of space and 1 of time
• Cosmos has only these 4 dimensions
• Must know where and when

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Natural Motion

• Newton Natural motion is constant speed along a
  straight line (constant velocity, no
  acceleration)
• Straight line Shortest distance between two
  points
• Assumed A flat (Euclidean) geometry

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Einstein

• NO assumption about local or global geometry of
  cosmos (flat or curved)
• Options flat (Euclidean), open (saddle), closed
  (sphere), in four dimensions (spacetime)
• Natural motion Freefall (weightlessness)

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General Theory of Relativity

• Gravity not a force! Natural motion in a curved
  spacetime.
• Objects follow straight (4-dimensional!) lines
  in spacetime
• Matter tells space how to curve, and space tells
  matter how to move.

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Gravity-Two Views

• Newton Forces (interactions at a distance)
• Einstein Courses (local paths in spacetime)
• Predicts bending of light (eclipses,
  gravitational lenses), expansion of universe
  used in GPS satellites

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General Theory Cosmology

• Physics of cosmological models
• Explains past, predicts future
• Big Bang (any geometry)
• Big Bore (flat or open)
• Big Crunch (closed)
• Compare actual density to critical density (open,
  flat critical closed gt critical)