Gravity Newton vs Einstein

# Gravity Newton vs Einstein - π r Limitations of Analogy...

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Gravity Newton vs. Einstein Newton viewed gravity as a mysterious “action at a distance” Einstein: what we perceive as gravity arises from curvature of spacetime Curved Space o Travelers going in opposite directions in straight lines will eventually meet o Because they meet, the travelers know Earth’s surface cannot be flat- it must be curved o Gravity can cause two space probes moving around Earth to meet o General relativity says this happens because spacetime is curved o Classical Analogy Rubber sheet with masses – masses would depress the rubber Heavier masses cause a greater distortion of the rubber sheet Matter distorts spacetime in this same way On a flat rubber sheet Free falling objects move in straight lines Circles all have circumference 2 π r Mass of Sun curves spacetime Free-falling objects near Sun follow curved paths Circles near sun have circumference <2

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Unformatted text preview: π r Limitations of Analogy Rubber sheet shows only two dimensions of space Path of orbiting object spirals through spacetime as it moves forward in time o Time in an accelerating spaceship Light pulses travel more quickly from front to back of an accelerating spaceship than in other direction Everyone on ship agrees that time runs faster in front than back o Time in a Gravitational Field Effects of gravity are exactly equivalent to those of acceleration Time must run more quickly at higher altitudes in a gravitational field than at lower altitudes o Acceleration = gravity Acceleration bends light Gravity bends light • Gravitational Lensing o Gravitational lensing can distort the images of objects o Lensing can even make one object appear to be at two or more points in the sky...
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Gravity Newton vs Einstein - π r Limitations of Analogy...

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