# Is Blue Shift just as provable as Red Shift?

I've heard a lot about red shift and it sounds pretty legit. But it made it sound as if blue shift was a lot less likely. Can anyone help me out?

The expansion of the Universe can be expressed using Hubble's law. This is that the recession velocity that a galaxy has with respect to our own is proportional to its distance from us. i.e. $$v = H_0 D,$$ where $v$ is the recession velocity, $D$ is the distance and H_0 is the Hubble "constant", which has a value of about 70 km/s per Megaparcsec.