How do scientists think the universe began?
(Lansing State Journal, November 19, 1997)
The most widely accepted scientific theory for the creation of the universe is the "Big Bang" theory. This theory arose from observational evidence that virtually all galaxies are moving away from us, and the farther away they are the faster they are moving. Then, if we imagine going back in time, all galaxies get closer and closer together.
According to the "Big Bang" theory, the universe starts as a point. It then begins to expand, being comprised mainly of high energy radiation. After about 1000 years of expansion the universe cools enough for there to be more matter than radiation, and atoms can begin to form. Galaxies begin to form after one million years. The universe continues to evolve through the death of old stars and the birth of new ones.
The name "Big Bang" seems to imply an explosion; however, this in not quite an accurate picture. Although galaxies are moving away from each other, it is not because they were shot out into the "rest" of the universe as in an explosion. Instead, the universe itself is expanding. Picture the universe as a lump of raisin bread dough, and the raisins represent galaxies. As the dough rises and expands the raisins get farther apart from each other. No matter which raisin you consider, all the other raisins are moving away from it.
Although the "Big Bang" theory is generally accepted by the scientific community, the details are still being debated. These include such topics as the age of the universe and whether or not the universe will continue to expand forever. New data clarifying these issues continues to be gathered through improved observational techniques and computer simulations.
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