But there's more. There universe is known to contain billions of galaxies. There is a lot of matter out there. But something seems to be missing. It appears that what we can see may not be all there is.
Strong evidence is mounting that suggests there exists large amounts of dark matter in the universe.
Astronomers refer to this invisible mass as dark matter. The evidence for dark matter lies with gravity. Everything in the universe is mutually attracted to everything else. Scientists have been able to calculate the total mass of the visible universe. They have also calculated the gravitational forces that hold the universe together.