Chapter17.Cosmology

Chapter17.Cosmology - 1 Cosmology Chapter 17 2 Olbers...

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Unformatted text preview: 1 Cosmology Chapter 17 2 Olbers Paradox Why is the night sky dark? - This is a problem if the Universe is infinite and eternal . 3 Hubble Ultra Deep Field Galaxies like grains of sand. Almost every image is a galaxy, some as far as 13 billion LYs. 4 5 In an expanding Universe, every galaxy sees (almost) all the other galaxies receding from it! 6 The Universe is expanding The redshifts of galaxies is evidence that the universe is expanding. 7 The Universe is expanding If the universe is expanding, it must have been smaller in the past. If it was smaller in the past, then there must have been a beginning for the universe Working backwards, what would the universe be like at the beginning? Hot, dense, tiny 8 PROBLEM : What about Newtons Laws and Gravity? Shouldnt everything be coming together rather than moving apart? 9 Solution : We need a better theory of gravity to compare to the Universe Albert Einstein (1879 1955) Swiss/American physicist 10 Space-time and Gravity Albert Einstein stunned the scientific world in 1915- with publication of his general theory of relativity general theory of relativity- it illustrates how space-time can be used to describe the behavior of how mass and light interact - it is an explanation of how gravity works Isaac Newton saw gravity as a mysterious force.- even Newton had problems accepting this concept of action at a distance how the force of gravity is transmitted through space- Einstein theorized that the force of gravity arises from distortions of space-time itself! 11 Einstein showed that the Universe is four-dimensional Moving in one direction creates a line (1- D). Moving in two directions creates a plane (2- D). Moving in three directions creates a cube or space (3- D). Whats the fourth dimension? TIME! we exist in space-time dimension an independent direction of possible motion 12 The Universe is four-dimensional Let us use Einsteins description of space-time, the four dimensional fabric that makes up our universe. The universe has three spatial dimensions (length, width, height) and one time dimension In these next few pictures, we will show a 2-dimensional space, with the warping of space-time as the third dimension 13 Matter warps space-time like weights on a rubber sheet, pulled tight. The greater the amount and concentration of mass (density), the more that space-time warps, and the stronger gravity becomes. Matter Warps Space-time 14 The Strength of Gravity The greater the amount and concentration of mass (density), the more that space-time warps, and the stronger gravity becomes....
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Chapter17.Cosmology - 1 Cosmology Chapter 17 2 Olbers...

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