When astronomers add up all the visible stars, planets, and gas in the universe, it accounts for only about 5% of what should be there. The rest is dark matter and dark energy—two mysterious substances we can’t see but know exist because of their gravitational effects. We still don’t know what dark matter is made of, but whatever it is, it outweighs normal matter by nearly six to one.
Enjoyed this article?
Get daily 10-minute PDFs about astronomy to read before bed!
Sign up for our upcoming micro-learning service where you will learn something new about space and beyond every day while winding down.