1 Discussion on Chapters Einstein’s Universe Gravity at work and play

2 Chapter 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 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. ”

3 Living in space h h

4 Chapter 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. ”

5 Warping of space and time

6 The Equivalence Principle h For Einstein intuition -- all motion should be relative his equivalence principle The effects of gravity are exactly equivalent to the effects of acceleration.

7 Weak equivalence principle In 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)

8 Light responds to a gravitational field es/LIGHTCONE/equivalence.html

9 Two basic ways to increase gravity/curvature of spacetime: Increase the mass Increase density of object of a given mass

10 Gravitational Lensing always Light always 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.

11 Gravitational Lensing Einstein’s Cross Background object is a quasar--a galaxy with a superluminous nucleus

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13 Gravity Probe-B Overview of Science and Results h Experiment in Newton’s Universe h Experiment in Einstein’s Universe h A simple experiment Results: Within uncertainty of statistical and systematic uncertainties, frame-dragging clearly detected.

14 Chapter 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. ” h LIGO

15 Jell-O waves LASER INTERFEROMETER GRAVITATIONAL-WAVE OBSERVATORY