The Universe

Origin of the Universe

When and how did matter first form?

After the Planck time, the universe expanded rapidly, and all the energy rushed outward to fill that expanding volume; as a result, the universe began to cool down. By about a millionth of a second after the Big Bang, the temperature of the universe was still well above a trillion degrees. But the energy density had probably dropped enough that subatomic particles of matter could come into existence for brief periods of time, reverting back and forth between matter and energy. This state of the universe, informally called the “quark-gluon soup,” may not even be the earliest appearance of matter in the universe. Still, it is the hottest and earliest cosmic state scientists have been able to simulate so far, using huge supercolliders that can generate microscopic bursts of tremendous energy density.


This is a web preview of the "The Handy Astronomy Answer Book" app. Many features only work on your mobile device. If you like what you see, we hope you will consider buying. Get the App