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- This Review illustrates the first of two equations that lead to the discovery of an expanding Universe. The Redshift of light occurs because the space between the galaxies is expanding stretching the wavelength of the light as it travels over that distance. Longer wavelengths are stretched towards the red end of the light spectrum. Blue light is a shorter wavelength of 400 nanometers. Red light has a longer wavelength of 700 nanometers.
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- The Brightness method to measure galaxy distance follows in the next Review # 1597. To illustrate measuring recession velocity we will do the calculation on a familiar star in our Milky Way Galaxy. The star Vega in the Constellation Lyra The Harp is directly above us this time of year.
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- We can measure the absorption line of hydrogen gas in the laboratory on Earth to be 656.285 nanometers wavelength. When an astronomer identifies a hydrogen gas absorption line come in a from the light from Vega we find it at 656.255 nanometers wavelength. The wavelength is shorter by 0.03 nanometers. The velocity of the star Vega is coming towards us. It is Blueshifted to a shorter wavelength.
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- To calculate the velocity of Vega coming towards us we use the relationship that the ratio of the velocity to the speed of light is equal to the amount of wavelength shift to the original wavelength.
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--------------------------- Velocity / Speed of Light = w1 - w0 / w0
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---------------------- w1 - w0 / w0 -------------- is the amount of Blueshift
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---------- Blue shift = 656.285 - 656.255 / 656.285 = 0.03 / 656.285
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--------- Blue shift = 0.00004572
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- Light from the star Vega is being compressed, or shortened, by 0.00457 %. It is Blueshifted by that percent because the velocity of the star is coming towards.
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------------------------ Velocity / Speed of Light = 4.582*10^-5
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------------------------ Speed of Light = 3*10^5 kilometers per second.
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------------------------ Velocity = 13.7 kilometers per second.
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------------------------ 1 kilometer per second = 2,237 miles per hour
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---------------------- Velocity = 30,647 miles per hour.
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- The star Vega is coming towards us at 30,647 miles per hour. However, it is 580 lightyears away from us, so, it will take a long time to get here. Stars in the Milky Way Galaxy are all gravitationally connected. The are rotating in a disk shape around a common center. Some stars are coming towards us and some are moving away from us. It is dance of stars that are all connected inside the Milky Way.
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- There is a different story when we measure velocities of galaxies relative to each other. The space between galaxies is so vast that gravity’s connection is no longer dominate. The energy in space itself is more dominate and causing galaxies to recede from each other. We say space is expanding. We call the energy that creates this expansion Dark Energy. “ Dark” because we do not know what it is.
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- Galaxies in our Local Group of galaxies are also gravitationally connected. The Andromeda Galaxy is also coming towards us at high velocity. It will reach us in another 5 billion years. However, galaxies farther out in space are all being Redshifted, are all moving away from us. See Review #1083 where this same calculation is performed on a distant galaxy with a Redshift of 6. It has a receding velocity of 6,696,000 miles per hour. That velocity is 1% the Speed of Light. Its distance is 136,000,000 lightyears.
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- The next review #1597 (Part IV of VI ) Shows how the Brightness Method is used to calculate these distances.
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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 Wednesday, October 23, 2013
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