*************** Big Bang ********************** The Big Bang theory is the prevailing cosmological model for the early development of the universe.The key idea is that the universe is expanding. Consequently, the universe was denser and hotter in the past. Moreover, the Big Bang model suggests that at some moment all of space was contained in a single point, which is considered the beginning of the universe. Modern measurements place this moment at approximately 13.8 billion years ago, which is thus considered the age of the universe.After the initial expansion, the universe cooled sufficiently to allow the formation of subatomic particles, including protons, neutrons, and electrons. Though simple atomic nuclei formed within the first three minutes after the Big Bang, thousands of years passed before the first electrically neutral atoms formed. The majority of atoms produced by the Big Bang were hydrogen, along with helium and traces of lithium. Giant clouds of these primordial elements later coalesced through gravity to form stars and galaxies, and the heavier elements were synthesized either within stars or during supernovae.In the first second after the universe began, the surrounding temperature was about 5.5 billion Celsius. The cosmos contained a vast array of fundamental particles such as neutrons, electrons and protons. These decayed or combined as the universe got cooler.This early soup would have been impossible to look at, because light could not carry inside of it. The free electrons would have caused light (photons) to scatter the way sunlight scatters from the water droplets in clouds, NASA . Over time, however, the free electrons met up with nuclei and created neutral atoms. This allowed light to shine through about 380,000 years after the Big Bang.This early light — sometimes called the afterglow of the Big Bang — is more properly known as the cosmic microwave background (CMB).
Posted on: Mon, 08 Dec 2014 16:17:36 +0000
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