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Albert Einstein and the Theory of Relativity

Albert Einstein and the Theory of Relativity. Chapter 7. Great Idea: All observers, no matter what their frame of reference, see the same laws of nature. Frames of Reference. Frames of Reference: Physical surroundings from which you observe and measure the world around you.

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Albert Einstein and the Theory of Relativity

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  1. Albert Einstein and the Theory of Relativity Chapter 7 Great Idea: All observers, no matter what their frame of reference, see the same laws of nature

  2. Frames of Reference • Frames of Reference:Physical surroundings from which you observe and measure the world around you. The forward motion of an adjacent bus can give you an impression that your own bus is moving backward.

  3. Frames of Reference • Coin’s path appears different depending on your frame of reference

  4. The Principle of Relativity • Baseball vs. Light (1) ball 40km/hr, train 100 km/hr, throw forward and backward; (2) flash light on a train, speed measured forward and backward. • Three possibilities • (1) The laws of nature are not the same in all frames of reference • (2) Maxwell’s equation could be wrong • (3) Our intuitions about the addition of velocities could be wrong • Einstein focused on the third possibility

  5. The Principle of Relativity • Principle of Relativity • Every observer must experience the same natural laws • Special relativity: deals with reference frames in uniform motion relative to one another. • General relativity: applies to any reference frame whether or not it is accelerating relative to another • The speed of light, c, is the same in all reference frames

  6. Special Relativity: Time Dilation • Time Dilation • Moving clock appears to tick more slowly • to the stationary observer.

  7. The Size of Time Dilation • Calculation of time dilation • tGG=tMM =d/c • Observation of moving clock by ground-based observer: distance and time traveled by light in 1 tick The expression is a number, called Lorentz factor

  8. Time Dilation: Twin Paradox At a speed of 0.995c for v, the difference in aging of the twin sisters could be quite striking: 10 vs 100 years.

  9. Distance and Relativity • Length Contraction • Moving object appears shorter • rest • 0.5c • 0.95c • 0.99c

  10. Mass and Relativity • Third consequence • Mass is the lowest for stationary objects

  11. Mass and Energy • Einstein • All objects contain a rest energy • Mass can be converted to energy and vice versa • The amount of energy involved are prodigious. • Energy form nuclear reactors conforms this prediction.

  12. General Relativity: Nature of Gravity • Gravitational forces or acceleration • No experiments in your frame of reference can tell the difference

  13. Nature of Gravity: Newton vs Einstein • Newton: forces cause objects to accelerate. Space and time are separate dimensions; • Einstein: objects move according to distortion in space, while the distinction between space and time depends on frame of reference.

  14. Space and Time Continuum • General theory of relativity is largely about the nature of gravity. • Euclidean (ordinary) geometry: parallel lines never meet. • Non-Euclidean (Einstein’s) geometry: parallel lines will meet. • Black hole: Light gets in but cannot get out

  15. Predictions of General Relativity • Gravitational bending of light passing near the Sun • Changing orientation of the orbit of Mercury • The gravitational redshift • (a clock in a strong gravitational field runs more slowly than one in a weaker gravitational field) Gravity Probe B

  16. Who Can Understand Relativity • Everyone!!!

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