Scientists Say: Big Bang

This is the current theory about how our universe began

This image shows how the universe might have come to be, from a small dense point at left, through “quantum fluctuations” and then to the Big Bang. That time of rapid inflation left behind the light pattern that scientists see today — called cosmic background radiation. After a period called the “dark ages,” matter condensed and cooled, and stars and planets began to form. 

WMAP Science Team/NASA

Big Bang (noun, “Big Bang”)

This theory explains how our universe began. About 14 billion years ago, all the matter that makes up the universe was squashed into an incredibly small space. Because the matter was so condensed, it wasn’t in any form we would recognize today. No atoms, or even particles. Suddenly, though, that matter went through a rapid inflation — an explosion, in a way. That’s the Big Bang. The result was a super-hot mass of matter, including light and charged particles such as protons and electrons. The matter cooled slowly over billions of years. As it cooled, it formed elements such as hydrogen. The matter also began to clump together into stars and planets. At the same time, the universe kept on cooling and expanding. In fact, the universe is still cooling and expanding today. 

No one, of course, was around at the time of the Big Bang. And so scientists are always looking for more evidence that the Big Bang really occurred. For example, the Big Bang’s huge explosion should have sent ripples through space and time — gravitational waves. Using laser beams traveling down extremely long tubes, scientists have previously detected gravitational waves from two black holes colliding. In 2014, scientists thought they had detected gravitational waves from the Big Bang itself. Unfortunately, they were wrong. But don’t worry, they’re still looking.

In a sentence

The best evidence for the Big Bang is the remnants of the light — called cosmic background radiation — released from the original explosion.

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Bethany Brookshire is the staff writer at Science News for Students. She has a Ph.D. in physiology and pharmacology and likes to write about neuroscience, biology, climate and more. She thinks Porgs are an invasive species.

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