Cosmogony the theory about the origin and development

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Cosmogony – the theory about the origin and development of the universe a) Seeks to explain how the universe came to be 155) Cosmology – is the science of the universe, the universe as a whole a) and includes cosmogony b) Explain the composition of the universe and the laws that govern it 156) The Radial velocity of galaxies is the component of relative velocity that lies in the line of sight. Remember that velocity consists not only of speed, but also of direction.
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a.i) The radial velocity of a galaxy is its velocity in the line of sight, or in other words its speed straight towards you or away from you. a.ii) Evidence from the radial velocities of the galaxies acknowledges that the universe is expanding. The first radial velocities of galaxies were measured by V. M. Slipher at the Lowell Observatory. 157) The more distant a galaxy, the greater, in direct proportion, its speed of Recession as determined by the shift of its spectral lines to the longer (or red) wavelengths. a) By the 1930's, M.L. Humason and Edwin Hubble had begun to photograph spectra of fainter galaxies and found that in general, the fainter and smaller a galaxy appeared, the higher was its redshift. b) This was then interpreted to mean that the more distant a galaxy, the higher its speed of recession--in other words, the faster it's moving away from us. c) This finding is known as the law of red shifts; it is often simply referred to as Hubble's Law. 158) Big Bang Theory - The currently most widely accepted theory for how the universe was formed a) According to the Big Bang theory, the universe started around 12 to 14 billion years ago. b) There are other theories which have been espoused by big name scientists, c) Currently the Big Bang theory is the most commonly accepted and well-known explanation for how the universe came to be. 159) Singularity - In the Big Bang theory, everything originated from a single tiny, infinitely dense and hot and massive point a) Inside of this singularity was contained all of the matter and energy of the universe, which means nothing (not even space) existed outside of it. This singularity then expanded into the universe as we know it today. (a.i.1) Note that at the core of each black hole is also thought to exist a singularity. b) A singularity simply refers to a point of infinite density and infinitesimal (immeasurably small) volume. c) It is imagined that in a singularity, space and time would become infinitely distorted. 160) There are three main ideas which are seen as supporting evidence by proponents of the Big Bang theory. (a.i.1) The first is that according to Hubble's Law, the universe is Expanding (a.i.1.a) As you recall, Hubble discovered that the light coming from almost all galaxies is redshifted (only about 100 galaxies have been recorded which are blueshifted), which he interpreted to mean that they are moving farther away and that the universe is expanding.
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  • Winter '12
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