How do we know dark matter exists?

Image credit: NASA, ESA, M. Postman (STScI), and the CLASH Team

Question from Oleg Shmetkov

Even though dark matter can’t be seen or detected with any of our scientific instruments, we know it’s there because of the effect it has on other matter in the universe. For example, stars and galaxies move much faster than they should do when pulled by normal gravitational forces, so there must be something else producing the gravity to make them move in this way. The best theory is ‘dark matter’ made up of as-yet undiscovered particles.

Answered by Jo Stass for Brain Dump in How It Works issue 125.

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