What keeps galaxies floating in space?

Electromagnetic repulsion between halos of neighbouring galaxies keeps them apart, while gravitational attraction between galaxies tends to bring them nearer. read more

An astronaut floating in space is falling, and falling all the time. An astronaut floating around in the International Space Station is still very much subject to Earth's gravitational pull. The gravitational force on that astronaut is only reduced by about 10% compared to the gravitational force the astronaut experiences on the surface of the Earth. read more

Nothing really, but it is huge enough and other galaxies far enough away that we’d have to keep our eyes open for many millions of years to notice that it is moving. read more