Reduced microwave image of the universe
(Source: NASA)

Scientists think that our universe began sometime between 10 and 20 billion years ago, an event known as the Big Bang.

When the universe began so did space and time. The universe expanded very quickly. It also cooled. After a tiny fraction of a second, the universe consisted of several kinds of particles, including electrons, and the forces between them.

In time, atoms were formed, and then stars and planets.

Everything that exists, space, time, stars, galaxies, and you, can be traced back to the Big Bang.

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