Dark matter, because it gravitationally attracts, it tends to encourage the growth of structure, OK.

As the universe cooled, the rest mass energy density of matter came to gravitationally dominate that of the photon radiation.

But because gravitationally attracting matter is embedded in this space, it tends to slow down the expansion of the space, OK.

The Roche lobe is the region of space around a star in a binary system within which orbiting material is gravitationally bound to that star.

Saturn grabs it gravitationally and flings it up and out of the solar system, so if I just keep letting this go, you can see Voyager 1 fly up like that.

Approximately three months before the end, the Solar System (or systems similar to our own at this time, as the fate of the Solar System 22 billion years in the future is questionable) would be gravitationally unbound.

So the evidence that we have that a quarter of the universe is dark matter this gravitationally attracting stuff is that galaxies, the speed with which stars orbiting galaxies is much too large it must be embedded in dark matter.

So the evidence that we have that a quarter of the universe is dark matter this gravitationally attracting stuff is that galaxies, the speed with which stars orbiting galaxies is much too large it must be embedded in dark matter.