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- The Universe is expanding but in an astronomer’s lifetime she would hardly notice. 100 years ago the astronomers were certain the Universe was “ static” neither expanding or contracting. The Milky Way Galaxy was our Universe. Then, 1920’s Hubble’s discoveries changed all that. Other galaxies were discovered that were moving away from us. The further away the galaxy was the faster it was receding away.
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- Today astronomers are studying galaxies that are billions of lightyears away. Today astronomers can model the Observable Universe, put the model on a computer. They can start the simulation after the Big Bang and use the algorithms in physics to run the expansion of time. Then see how the results compares with what we see today. If there is not a good match astronomers can change initial conditions, or change assumptions, and run it again.
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- Cosmology has entered the world of experimentation. Google the Bolshoi to learn more. http:hipacc.ucsc.edu/Bolshoi.
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- The observations are the inputs. The laws of physics run the software. Einstein’s Theory of General Relativity are the equations in the software.
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- The simulation assumes Cosmic Inflation occurred shortly after the Big Bang. The Inflation grew the Universe 1,000 times faster than the speed of light. The quantum fluctuations at the sub-atomic level when the expansion began grew into the lumps of matter and energy we see in the Universe today.
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- Gravity coalesced Cold Dark Matter into halos around ordinary matter . These structures eventually evolved into galaxies and clusters of galaxies interconnected by filaments of matter and separated by giant voids of space.
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- The simulation also assumes Einstein’s Cosmological Constant that opposes gravity . This is the Dark Energy that is expanding space and growing the size of the Universe.
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- The model’s assumptions best fit is when 73% of the Universe is Dark Energy and 22% is Dark Matter. 5% is ordinary matter ( Baryonic matter which is made up of protons and neutrons.). Only 0.5% is the matter visible as stars and gas/dust that we call “ our world”.
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- The simulations created take a lot of computer time, about 6 million CPU hours. the resolution in the software is down to 5,000 lightyears. ( The Milky Way Galaxy is 100,000 lightyears with a Dark Matter halo extending out to 2,000,000 lightyears.)
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- Using the simulations astronomers can observe the Dark Matter directly. We know the Dark Matter exists by measuring the speeds f stars and gas in galaxies and the speeds of galaxies orbiting in clusters of galaxies. Another measure is the bending of light from background galaxies passing by foreground clusters of galaxies.
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- The computer simulations are agreeing accurately with the observations we see today. The calculations and assumptions must be close to reality. Now astronomers can start experimenting with “ what if’s” in the laboratory. Astronomers can change the assumptions and quickly see the results. They can run the software forward in time and see what the Universe will look like in the future.
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- It all boils down to simple multiplication. The Earth is 10^7 meters, the Galaxy 10^22 meters, the Observable Universe 10^27 meters, the Whole Universe 10^58 meters. An announcement will be made shortly, stay tuned.
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RSVP, please reply with a number to rate this review: #1- learned something new. #2 - Didn’t read it. #3- very interesting. #4- Send another review #___ from the index. #5- Keep em coming. #6- I forwarded copies to some friends. #7- Don‘t send me these anymore! #8- I am forwarding you some questions? Index is available with email upon request. Some reviews are at http://jdetrick.blogspot.com Please send feedback, corrections, or recommended improvements to: jamesdetrick@comcast.net. ---- “Jim Detrick” -- www.facebook.com, -- www.twitter.com, -- 707-536-3272 Thursday, March 28, 2013
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