Why do galaxies look like they're moving away from us?

History of the Big Bang theory

Why do galaxies look like they're moving away from us?

Imagine you're at a party where everyone is moving away from you as you dance. You can see your friends getting further apart as time goes on.

The universe is like that party, with galaxies moving away from each other as space expands. This idea is called "redshift."

Example

If you watch a friend walk away while waving a flashlight, the light stretches and shifts towards the red end of the spectrum.

Remember this

Redshift shows that the universe is expanding, supporting the Big Bang theory.

Text adapted from Wikipedia, licensed under CC BY-SA 4.0.

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