Except the galaxies do not travel. Galaxies are more or less stationary, it's the space inbetween that expands. Think in terms of raisins in a dough or points on expanding baloon. Neither of them could be said to travel, yet they can be seen to become more and more far away.
> In physical cosmology, peculiar velocity refers to the components of a galaxy's velocity that deviate from the Hubble flow. ....
> Galaxies are not distributed evenly throughout observable space, but are typically found in groups or clusters, where they have a significant gravitational effect on each other. Velocity dispersions of galaxies arising from this gravitational attraction are usually in the hundreds of kilometers per second, but they can rise to over 1000 km/s in rich clusters.
That's why I wrote "more or less stationary", which is describing 1000km/s compared to double the speed of light that would come from naive calculation.
