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Astronomy: Edwin Hubble
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Edwin Hubble was born in Marshfile, Missouri USA in 1889 and lived until 1953. He studied law at the University of Chicago and Oxford and then studied astronomy. After military service during world war I he settled in Mount Wilson Observatory where he remained his entire life. In 1924 he used Cepheid variable stars to determine the distance to the Andromeda galaxy. After that he proposed the evolutionary theory that eliptical galaxies evolve from circular galaxies (the tuning fork diagram). Today this theory is found not to be correct. But the basic forms he described are still used. Hubble's lawIn 1929 he proposed that the Universe is expanding, which is referred to as Hubble's law. The fact that the Universe is expanding means that there is a start and a time of growing. The Big Bang theory was born.Hubble observed data from Vesto Slipher who studied around 40 galaxies in the early 1920s. Slipher found that most of them had redshifts* and only 4 had blueshifts. Most galaxies were moving away from us, which meant the stars were not moving at random.
vr = H0d
Hubble then stated that the velocity (vr ) of any distant galaxy is proportional to its distance (d ). The value H0 is known as Hubble's constant. Hubble constant to calculate the age of the UniverseWhen astronomers looked at the redshift of a galaxy* and with the Hubble telescope knew an accurate distance, it was possible to estimate the value of the Hubble constant.With an uncertainty of 10% the Hubble constant was estimated at 40 mi/s/Mpc. This means that the recession speed of galaxies increases by 40 miles (65 km) per second for every million parsecs distance from Earth. If the expansion of the Universe was steady and with the help of the Hubble constant it is possible to calculate back to the Big Bang moment. In that case - and that is our best estimate at this point - our Universe is 13.7 billion years old. * the redshift and blueshift of galaxies tells us if a galaxy is moving towards or away from Earth. It is comparable to traffic passing by. When a policecar with its sirine on, passes you by, the sirene sounds different. Redshift and blueshift shows astronomers the same. Related subjects>> The Universe>> The Hubble Space Telescope |
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