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----------------- 1821 - Describing the Universe
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- The Universe can be described with a model using 6 qualities:
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- (1) The Universe is expanding at 47,000 miles per hour per million lightyears distance.
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- (2) The density of ordinary matter. It is only 5% of the mass-energy that is in the Universe.
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- (3) The Cosmic Microwave Background (CMB) is the Universe’s first light that was emitted 380,000 years after the Big Bang.
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- (4) An invisible substance called Dark Matter is 24% of the Universe. It interacts with gravity but not with electromagnetic radiation.
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- (5) Dark Energy is 71% of the Universe and responsible for the expansion that is accelerating. It is causing space to stretch apart at this ever accelerating rate. The more space the faster the whole Universe expands.
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- (6) There are subtle temperature variations in the CMB which reflect earlier quantum fluctuations. These got amplified with Cosmic Inflation to become vast regions of varying density. Mass in the higher density regions collapsed into galaxy clusters.
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- One important assumption to explain Cosmic expansion is that Dark Energy per unit volume has remained constant over time, 47,000 miles per hour per million lightyears.
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- Another assumption is that Cosmic Inflation actually occurred shortly after the Big Bang. The model has yet to explain why and how this happened. If it did we should be able to detect some evidence of this rapid expansion in observing gravitational waves. But, we have yet to discover the gravity wave evidence. ( See LIGO review for the experiments that are doing the searching)
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- Astronomers would hope to connect gravitational wave measurements with matter density deviations in the CMB.
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- The Universe is so vast that even at the speed of light, 186,282 miles per second, the light from distant galaxies takes millions, even billions, of years to reach us. During that time for the light to travel that distance the Universe has been expanding even more and the distances have gotten even greater.
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- Astronomers use the Cosmic Redshift to measure the rate of expansion and how it has changed over time. Astronomy is a time machine to look backwards in time. Galaxies that we see today are actually more distant then they were when the light reaching us now was first emitted.
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- The Redshift (z) is the fractional difference between the observed wavelength (w) as a line in the object’s spectrum and the wavelength at the time it is emitted (Wo), original wavelength.
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---------------------------- z = Wo - w / w
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--------------------------- v = the receding velocity of the light source (Wo)
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--------------------------- v = c * z
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--------------------------- c = the speed of light, 186,282 miles per second, or 300,000
km / sec.
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- If a blue light spectrum was emitted at 400 nanometers wavelength. And, it got stretched out traveling through expanding space to reach us, and, we observed this spectrum in the far infrared at 800 nanometers wavelength, then, the Redshift would be:
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----------------------------- z = 800 - 400 / 400
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------------------------------ z = 1
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----------------------------- v = 300,000 kilometers per second
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- The receding velocity is at the speed of light. The galaxy is so far away the space expanding between us is causing the galaxy to appear to be speeding away from us at the speed of light. This is not real velocity, but expanding space, it does not break the laws of physics to ever be exceeding the speed of light since it is expanding space and not a moving object.
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- Hubble’s Law (Ho) is that this expansion is a linear relationship between receding velocity (v) and the distance of the galaxy away from us (d).
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--------------------------------- d = v / Ho
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-------------------------------- Ho = 22 kilometers per second per million lightyears, or 47,000 mph per million lightyears.
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-------------------------------- d = 3*10^5 / 22 million lightyears
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-------------------------------- d = 13,600 million lightyears
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---------------------------- d = 13.6 billion lightyears
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- But, the age of the Universe is only 14 billion lightyears. actually the reciprocal of Hubble’s Constant is the age of the Universe:
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-------------------------- 1 / Ho = 10^6 * (3*10^5 km/sec) * 1 year / (22 km/sec)
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-------------------------- 1 / Ho = 13.6 billion years.
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- This assumes that the Hubble Constant is linear and truly “ constant” over the life of the Universe. Astronomers believe this as “not” the case. Gravity was dominate the first 7 billion years slowing expansion. Then Dark Energy became dominate and has been accelerating expansion the last 7 billion years. We just happen to have a convenient average being in the middle.
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- The most distant galaxy, measured to date, has a Redshift of 8.63. The calculation is that this light took 13.24 billion years to reach us. The Universe was only 4% of its current age and the Universe was only 573,000,000 years old.
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- Because the Universe was expanding over that same time span today that galaxy is 30.35 billion light years away. That galaxy’s light today would never have time to reach us. It has expanded beyond our light horizon. Distant galaxies are steadily disappearing from view.
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- New satellite telescopes that can see in the far infrared wavelengths ( higher Redshifts) will allow us to see galaxies even further back in time.
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---------------Redshift --- Light travel ----- Age of Universe ------ Distance ------
------------------------------ billion LY ------- million years ----------billion LY ------
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-----------------12 ---------- 13.34 ------------ 365 -------------------32.7 -------------
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---------------- 15 ---------- 13.55 ------------ 267 -------------------34.1 -------------
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-----------------18 ---------- 13.61 ------------ 206 -------------------35.1 --------------
-----------------20 ---------- 13.64 ------------ 177 -------------------35.7 -------------
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-----------------25 ---------- 13.68 ------------ 128 -------------------36.8 -------------
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- Far away galaxies offer a glimpse into the past. When we look at distant galaxies we are seeing them as they were in the distant past.
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- Our closest spiral galaxy is the Andromeda. We see it as it looked 2,500,000 years ago. You can view it with binoculars on a clear night. In the north eastern sky.
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- The future of our Universe will be dominated by Blackholes. Our Universe today has lots of stars, but, the number of new stars forming each year is dropping. All stars will eventually burn out. Super massive Blackholes will still survive. Galaxies have super massive Blackholes at their centers. That will be what is left. Eventually even Blackholes evaporate due to Hawking Radiation. Only fundamental particles in cold expanses of space will exist with nothing to bump in to. No worries this will not happen for a very long time from now. Stay tuned, an announcement will be made shortly.
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- Request these Reviews to learn more:
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- #1808 - History of the Universe 16 pages long.
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- # 1782 - Telescopes looking back in time.
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- #1759 - Why is the Universe expanding?
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- #1672 - Beginning with a Universe
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- #1665 - Universe - How it all started.
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- #1634 - The Universe started out in the realm of particle physics.
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- #1590 - Structure of the Universe
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- #1563 - How old is the Universe?
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- #1311 - Is the Universe spinning, or is it just me?
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- #1234 - Why is the sky dark and the Universe leaving us?
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- #1225 - Is the Universe really a computer?
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- #1050 - The Universe almost didn’t happen?
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- #842 - Pressed for time.
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- #744 - What is the Universe expanding in to?
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- #342 - The Whole Shebang. Timothy Ferris 1997
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- --------------------------------------------------------------------------------------
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--- Some reviews are at: -------------- http://jdetrick.blogspot.com -----
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- to: ------- jamesdetrick@comcast.net ------ “Jim Detrick” -----------
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----- 707-536-3272 ---------------------- Saturday, January 30, 2016 -----
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