notes for the day: general theory of relativity (a gravity theory): ingredients: the principle of...
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NOTES FOR THE DAY: General Theory of Relativity (a gravity theory):
Ingredients:
The Principle of Equivalence: acceleration ~ gravity
Riemann's Curved Geometry: acceleration ~ curved space-time
( ' ~ ' means 'is equivalent to'.)
This implies: gravity ~ curved space-time (Einstein's Field Eqns.)
This is important when objects are massive, like sun or black hole. Supercedes Newton's Law in these cases.
Three experimental-observational proofs of General Relativity:1. Perihelion precession of Mercury's orbit. (Slow rotation of
ellipse.2. Light bends near the sun.3. Time slows in a strong gravity field. (Ex. Gravitational redshift, and clocks flown in planes vs those on ground.)
The General Theory of Relativity (GTR)is a new theory of gravity, beyond Newton’s, & based on two ingredients:
1. The Principle of Equivalence: acceleration ~ gravity
Conceived byErnst Mach1838-1902
~ means ‘is equivalent to’.
Einstein can’t tell whether he is on the earth or in space, accelerating at 1 g.
2. Riemann's Curved Geometry was another ingredient, implying acceleration ~ curved space-time
George Riemann1826-1866
The essential idea of Einstein’s GTR
acceleration ~ gravity and acceleration ~ curved space-time imply
gravity ~ curved space-time (Einstein's Field Eqns.)
This is important when objects are massive, like sun or black hole. Supercedes Newton's Law in these cases.
Black hole—HELP! We need Einstein!
Three experimental-observational proofs of General Relativity:
1. Perihelion precession of Mercury's orbit (slow rotation of elliptical orbit 16 degrees/10,000 yrs).
Three experimental-observational proofs of General Relativity:
2. Light bends near the sun.
Arthur Eddington went to South Africa during a total eclipse of the sunTo test the bending of light by the sun’s gravity. He was the first to suggest this.It was later confirmed by anotherobservation.
Three experimental-observational proofs of General Relativity:
3. Time slows in gravity
The frequency of light (time-dependent) is decreased by a massive star (toward the red end of the spectrum).
This is called a gravitational red shift.