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Published byLeslie Copeland Modified over 8 years ago
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The Motion of the Universe
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What Keeps Celestial Bodies in Orbit? The First Person to attempt to answer this question was Isaac Newton Formulated the Law of Universal Gravitation Every object in the universe attracts every other object Force of gravity depends on two factors Mass of the object If mass increases, gravity increases Distance between objects If distance increases, gravity decreases
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So why doesn’t Earth fall into the Sun? Remember Newton’s First Law of Motion: Inertia keeps it in motion! Law of Inertia States: An object at rest will stay at rest or an object in motion will stay in motion unless acted on by a force This holds true for all objects orbiting other objects in the universe!
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Kepler’s First Law: Orbits of Celestial bodies Kepler's first law - sometimes referred to as the law of ellipses - explains that planets are orbiting the Sun in a path described as an ellipse
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Kepler’s Second Law The speed at which any planet moves through space is constantly changing. A planet moves fastest when it is closest to the Sun and slowest when it is furthest from the Sun. But if a line were drawn from the center of the planet to the center of the sun, that line would create a triangle of equal area. http://www.glenbrook.k12.il.us/gbssci/phys/mme dia/circmot/ksl.html http://www.glenbrook.k12.il.us/gbssci/phys/mme dia/circmot/ksl.html
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Newton vs. Einstein Newton thought that gravity was an instant force and did not take time to travel. (gravity is a pull) Einstein felt gravity moved like light – at a particular speed and propagated out from a source
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Einstein’s Theory of General Relativity Objects warp space Objects orbit because they are pushed into indentations that are created by other larger objects not because of a force that is pulling on an object.
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Big Bang Theory – Best Guess!! All celestial bodies in universe are made of the same 92 elements Spectral analysis using black line spectrum Found celestial bodies in universe are moving apart - black lines shifted to red side of spectrum Hubble telescope discovered background radiation leftover from Big Bang
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Red shift Red shift The shift in the visible light spectrum of a light to the red The shift in the visible light spectrum of a light to the red end of the spectrum Object is moving away from observer Object is moving away from observer Blue shift Blue shift The shift in the visible light spectrum of a light to the blue/violet end of the spectrum The shift in the visible light spectrum of a light to the blue/violet end of the spectrum Object is moving toward observer Doppler effect applied to stellar movement Longer wavelengths = red color Shorter wavelengths = Blue wavelengths
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Doppler shift applied to stellar movement
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Spectral Analysis Study of a star’s spectrum to determine composition, motion in space, and general temperature, pressure and rotational speed. (we will talk about this later) Astronomers produce spectra by means of a "spectrograph" affixed to the telescope.
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