Lecture 10 - GEOS 1004, SPOTILA Lecture 10, 10/1/09 PART...

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GEOS 1004, SPOTILA Lecture 10, 10/1/09 PART II: THE EARTH AND ITS FORMATION Formation of the Earth how did the Earth form? what was the earliest history of Earth? Big Bang: sudden explosion from a single, infinitely dense point at the center of the Universe; 10-15 b.y. ago. Big Bang theory does not explain why the bang occurred, but predicts the consequences of such an event would be. Evidence: 1) universal abundance of helium and hydrogen -first few seconds, no matter or atoms (too hot) -then nuclei of 1 proton form (hydrogen); some of these undergo nuclear fusion into He -cooling proceeds, fusion stops; no heavier elements * Elemental abundance of primordial stars = 75% H, 25% He (nothing else) 2) cosmic background radiation -proves the universe is still expanding 3) expansion -universe expands from a “singularity” (single focused point) Doppler effect; approaching object shifts to shorter wavelength (blue), receding object shifts to longer wavelength (red), called a "red shift". Hubble expansion; trace distance and velocity of all moving objects to a singular point. All galaxies exhibit a "red shift". During expansion, energy is lost due to “geometric spreading”. Gravitational attraction. .. of particles overcomes inertia Gravitational force is inversely proportional to the distance between the objects Local “gravitational instability” -a runaway process; mass accumulates and comes together in larger and larger bodies; accretion. What is the force of gravity, G, proportional to?
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Lecture 10 - GEOS 1004, SPOTILA Lecture 10, 10/1/09 PART...

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