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12:1:09 The Expanding Universe

# 12:1:09 The Expanding Universe - groups of galaxies The...

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The Expanding Universe The Expanding Universe Light waves get stretched -> redshift Individual galaxies do not get stretched What is the redshift? While we talk about Doppler shift, the “cosmological redshift” is really a  result  from the expansion of space. The photons get stretched as they travel along  expanding space Since this stretching is the expansion of space rather than the movements of  objects in space, the redshift can be as high as you want. How old is the universe? With Hubble’s Law, for the distance to every galaxy, you also know how fast it  is moving away? If you know how far away something is, and how fast it is moving, you can  figure out how long it took to get there H O  is observed to be 23km/s/Mlyr Some small scale variations in motions due to gravity from other galaxies and

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Unformatted text preview: groups of galaxies The Next Step • What is the most important thing we have not accounted for in the calculation so far? o The gravitational attraction of the mass in the universe pulls matter together and slows the expansion. • Was it always expanding this fast? The evolving Universe • Starts incredibly small – expands rapidly • Kinetic energy vs. gravitational attraction • The search for two numbers o Rate of expansion o Change of rate of expansion How can we tell? • Add all the mass up. Since the amount of matter in the universe determines its fate, we just need to add it all up o Not really all that easy, but we have worked at it • Since future is expansion vs. gravity o Gravity is how much mass, so measure mass ← 01/12/2009 08:39:00 ← 01/12/2009 08:39:00 ←...
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12:1:09 The Expanding Universe - groups of galaxies The...

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