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Discussion on Chapters 1 - 3Discussion on Chapters 1 - 3

Einstein’s Universe

Gravity at work and play

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Chapter 1Chapter 1

“From this apparently nonsensical idea that a falling person feels no gravity emerged the secrets of gravity and the universe.”

Living in micro-gravity presentation – astronauts are in a 0.95-g environment! PPT

p. 14 “The floor is moving up to meet the floating earring and bracelet and so obviously arrives at the two objects at the same time.”

p. 17 “The subconscious can work in strange ways.”

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Living in spaceLiving in space

http://www.youtube.com/watch?v=ya2vzagppVQ http://www.youtube.com/watch?v=HUe2HcFUPSo

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Chapter 2Chapter 2

p. 18 “…they think of a massive object, such as the earth, producing a field of force around it.”

p. 20 “The illusion is equivalent to, but not equal to, the reality.” What about Earth-Moon system?

THE BENDING OF LIGHT – PPT demonstration

p. 21 “Light is not falling, but the floor is rushing upward!”

p. 23 “That is all time warp is, dear reader, astonishing because it is fact….”

p. 26 “In a very real sense, the curvature of space and time is the gravitational field.”

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Warping of space and timeWarping of space and time

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The Equivalence Principle The Equivalence Principle

For Einstein

intuition -- all motion should be relativehis equivalence principle The effects of gravity are exactly

equivalent to the effects of acceleration.

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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)

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Light responds to a gravitational fieldLight responds to a gravitational field

http://www.phy.syr.edu/courses/modules/LIGHTCONE/equivalence.html

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Two basic ways to increase gravity/curvature of spacetime:

Increase the mass

Increase density of object of a given mass

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Gravitational LensingGravitational Lensing• Light alwaysalways travels at a constant velocity: c

follows the straightest possible path through spacetime

curved spacetime curves the trajectory of light• The light will “see” the star move towards and then away from it.

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Gravitational LensingGravitational Lensing

Einstein’s Cross

Background object is a quasar--a galaxy with a superluminous nucleus

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Gravity Probe-BGravity Probe-B

http://einstein.stanford.edu/Media/Newtons_Universe_Anima-Flash.html

Overview of Science and Results

Experiment in Newton’s Universe

Experiment in Einstein’s Universe

A simple experiment

http://einstein.stanford.edu/Media/Einsteins_Universe_Anima-Flash.html

http://einstein.stanford.edu/Media/Simple_Expt_Anima-Flash.html

http://einstein.stanford.edu/Media/Rel_gyro_expt-anima-flash.html

Results: Within uncertainty of statistical and systematic uncertainties, frame-dragging clearly detected.

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Chapter 3Chapter 3

p. 32 “If you were half as mighty as gravity, you would be incredibly famous.”

p. 35 “If mass and energy are effectively the same, then mass and energy can both produce gravity.”

p. 41 “… a less violent gravity wave will probably just send real-estate values plummeting.”

LIGO

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Jell-O wavesJell-O waveshttp://www.youtube.com/watch?v=GAwO1okR074

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LASER INTERFEROMETER GRAVITATIONAL-WAVE OBSERVATORY

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http://www.ligo-la.caltech.edu/LLO/overviewsci.htm