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Relativity

Relativity. Twinkle, twinkle little star How I wonder where you are “1.75 seconds of arc from where I seem to be For. 2GM. 2GM. ds 2 = ( 1 - ) dt 2 – (1 + ) dr 2 – r 2 d θ 2 – r 2 sin 2 θ d φ 2 “. R. R. Source Unknown. Relativity.

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Relativity

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  1. Relativity Twinkle, twinkle little star How I wonder where you are “1.75 seconds of arc from where I seem to be For 2GM 2GM ds2 = ( 1 - ) dt2 – (1 + ) dr2 – r2 dθ2 – r2 sin2θ dφ2 “ R R Source Unknown

  2. Relativity Frame of Reference - A set of coordinate axes in terms of which position or movement may be specified or with reference to which physical laws may be mathematically stated. Also called reference frame. Relativity – the study of the laws of physics in reference frames which are moving with respect to one another.

  3. Relativity Relativity – the study of the laws of physics in reference frames which are moving with respect to one another. Two cases: Case 1 (special case): reference frames move at a constant velocity with respect to each other. Case 2 (general case): reference frames accelerate with respect to each other.

  4. Special Relativity Introduced in 1905 by A. Einstein Special Relativity – the study of the laws of physics in the special case of reference frames moving at a constant velocity with respect to each other. Inertial Reference Frame – a reference frame that moves at a constant velocity.

  5. Special Relativity The Postulates of Special Relativity • First postulate • Observation of physical phenomena by more than one inertial observer must result in agreement between the observers as to the nature of reality. Or, the nature of the universe must not change for an observer if their inertial state changes. • Every physical theory should look the same mathematically to every inertial observer. • To state that simply, no property of the universe will change if the observer is in motion. The laws of the universe are the same regardless of inertial frame of reference. • Second postulate (invariance of c) • The speed of light in vacuum, commonly denoted c, is the same to all inertial observers, is the same in all directions, and does not depend on the velocity of the object emitting the light. When combined with the First Postulate, this Second Postulate is equivalent to stating that light does not require any medium (such as "aether") in which to propagate.

  6. Special Relativity The Postulates of Special Relativity As a result of the second postulate, once the distance to a celestial object is know, one can determine how far in the past the event occurred. Given the speed of light and the distance to the Large Magellanic Cloud, Supernova 1987a actually occurred 160,000 years before the observation, in about 158,000 BC !!

  7. Special Relativity The Postulates of Special Relativity Furthermore, it is understood that no phenomena can travel as a speed greater than 3 x 108 m/sec

  8. Special Relativity The Postulates of Special Relativity Furthermore, it is understood that no phenomena can travel as a speed greater than 3 x 108 m/sec What about Neutrinos (September 2011)?

  9. Special Relativity The Postulates of Special Relativity Furthermore, it is understood that no phenomena can travel as a speed greater than 3 x 108 m/sec What about Neutrinos (September 2011)? Probably not.

  10. General Relativity Introduced in 1916 by A. Einstein General Relativity – the study of the laws of physics in the general case of reference frames accelerating with respect to each other. Non-Inertial Reference Frame – a reference frame that accelerates.

  11. General Relativity – A Thought Experiment ? Scale reads 170 lb

  12. General Relativity – A Thought Experiment g = 9.8 m/sec2 ? ? Scale reads 170 lb Scale reads 170 lb

  13. General Relativity – A Thought Experiment a = 9.8 m/sec2 ? ? Scale reads 170 lb Scale reads 170 lb

  14. General Relativity – A Thought Experiment a = 9.8 m/sec2 g = 9.8 m/sec2 ? ? ? Scale reads 170 lb Scale reads 170 lb Scale reads 170 lb

  15. General Relativity – A Thought Experiment a = 9.8 m/sec2 g = 9.8 m/sec2 ? ? ? Scale reads 170 lb The Principle of Equivalency Scale reads 170 lb Scale reads 170 lb

  16. General Relativity Principle of Equivalency - Experiments performed in a uniformly accelerating (non-inertial) reference frame with acceleration a are indistinguishable from the same experiments performed in a non-accelerating (inertial) reference frame which is situated in a gravitational field where the acceleration of gravity = g = -a.

  17. General Relativity Principle of Equivalency 2001 A Space Odyssey

  18. General Relativity Principle of Equivalency - Experiments performed in a uniformly accelerating (non-inertial) reference frame with acceleration a are indistinguishable from the same experiments performed in a non-accelerating (inertial) reference frame which is situated in a gravitational field where the acceleration of gravity = g = -a. 2001 A Space Odyssey

  19. General Relativity Principle of Equivalency Centripetal Generotor at COSI

  20. General Relativity Principle of Equivalency - Experiments performed in a uniformly accelerating reference frame with acceleration a are indistinguishable from the same experiments performed in a non-accelerating reference frame which is situated in a gravitational field where the acceleration of gravity = g = -a. Centripetal Generotor at COSI When riding the Centripetal Generotor, you spin slowly at first, while increasing velocity. The force eventually pins you to the wall as the floor drops away. At about 3 g’s or 33 rpm's, the centripetal force is strong enough to make the static friction greater than the force of gravity, so when the floor drops away, you stick to the wall. When the rotor’s speed decreases, so does the centripetal force and the static friction, and you slide to the floor.

  21. General Relativity Example How is the Generotor G-force calculated? The force of Gravity (G) on Earth is used as a baseline for measuring these forces of acceleration. The force of gravity when you sit, stand, or lie down is considered 1 G. In normal activity, we rarely experience anything other than 1 G. As you exert more G's on the body, your weight increases correspondingly. Your 10-pound head will weigh 90 pounds when you pull 9 G's!If you continue to pull high G's, the G force will push the blood in your body towards your feet and resist your heart's attempts to pump it back up to your brain. You will begin to get tunnel vision, then things will lose color and turn white, and finally everything will go black. You've just experienced the onset of Gravity Induced Loss of Consciousness (GLOC). Riding the Generotor will not result in GLOC. Generotor G-force Calculations 1) The speed of the Generotor: 1 revolution / 1.82 seconds = 33 rpm (rotations per minute)2) The Generotor's drum radius = 7.5 feet or 2.29 meters.3) This translates to: speed = 2 x π x 2.29 / 1.82 sec = 7.9 m/s (meters per second) 4) Acceleration = speed x speed / radius = 7.9m/s x 7.9m/s / 2.29m = 27.3 (m/s)s5) Since 1 G = 9.8 (m/s)s = 27.3(m/s)s / 9.8 (m/s)s = the G force of 2.8G, which is ~ 3G's See http://www.cosi.org/visitors/exhibits/big-science-park/generotor/

  22. General Relativity

  23. General Relativity Implication of the Principle of Equivalency – photons should experience a gravitational force just like all other particles. The deflection is not observed under “normal” (ie, earth) gravitational fields because the photons move to fast. In order to observe the deflection of a photon, a large gravitational field is required. Because of the Principle of Equivalency, General Relativity is often referred to as the study of gravity Accelerating Systems and Photons

  24. General Relativity Experimental test True Position Apparent Position Einstein right Einstein wrong

  25. General Relativity Experimental test – Einstein proposed that the deflection of light from a star could be measured during a solar eclipse for a star near the edge of the sun during an eclipse. True Position Apparent Position Einstein right Einstein wrong

  26. General Relativity It is common wisdom now that the determination of the defelction of light from a star during the solar eclipse in 1919 by Arthur Eddington and his group was the second observational confirmation of General Relativity and the basis of Einstein's huge popularity starting in the 1920s. (The first one had been the explanation of Mercury's perihelion shift.) Recently, the value predicted by Einstein was confirmed to an accuracy better than 0.02% [104]. The position of the star was off by 1.75 seconds of arc

  27. Relativity Twinkle, twinkle little star How I wonder where you are “1.75 seconds of arc from where I seem to be For 2GM 2GM ds2 = ( 1 - ) dt2 – (1 + ) dr2 – r2 dθ2 – r2 sin2θ dφ2 “ R R Source Unknown

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