Lecture 14 - More on spacetime curvature, the equivalence...

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More on spacetime curvature, theequivalence principle, and introto the Milky Way
General Relativity and Spacetime• Remember our discussion in the first partof the course• Mass causes spacetime to curve• The curvature of spacetime tells mass(and other things) how to moveAstronomy 10G ©2015 C. Fassnacht2For more info: Chapter S3
Astronomy 10G ©2015 C. Fassnacht3Another view of black holes:The Sun at different sizes:The slope of the surface gives the strength of gravity thereA black hole is a hole in spacetime.The slope of the spacetimebecomes verticalHowever, the spacetime far outside the Suns radius is alwayscurved the same way
Astronomy 10G ©2015 C. Fassnacht4Reminder about curvedspacetime and orbits
Astronomy 10G ©2015 C. Fassnacht6What about light???• Light must obey thesame rules• It must stay within thecurved spacetime• Light travels on straightlines, but spacetimeitself is curved!
Astronomy 10G ©2015 C. Fassnacht8How does gravity bend light?• Theequivalence principle: Gravityequals acceleration
Astronomy 10G ©2015 C. Fassnacht9Acceleration• Consider a light ray moving through anaccelerating spaceship
Astronomy 10G ©2015 C. Fassnacht10= Gravity• Now consider the same situation seen ina gravitational field.
Astronomy 10G ©2015 C. Fassnacht11Light paths appear to bedeflected by mass!GravitationalLensing
Astronomy 10G ©2015 C. Fassnacht12First experimental test of Einsteinstheory of General Relativity (gravity)P.S. Need eclipse so you can see stars right nearthe sun, otherwise too bright!Dots show trueposition ofstars, linesshow positionsof stars duringeclipse.
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Term
Spring
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