# Hubble's Law: Can somone be nice and answer this.

1. Jul 28, 2008

### XxBioFrenzyxX

How are the distance and speed of a galaxy related?

2. Jul 28, 2008

### Kurdt

Staff Emeritus
3. Jul 28, 2008

### JimJast

They are related by so called Hubble law which really relates the distance and the observed redshift of a given galaxy which is assumed to be proportional to the "speed of recesion" of the galaxy v. The observed redshift is converted to the assumed "speed of recession" through the Doppler law, which for small Z's is v = Z c, where Z is observed redshift, and c the speed of light and then the distance is calculated from d = v / H, where H is Hubble constant (presently about 70 km/s/Mpc, Mpc being about 3,000,000 light years).

Last edited: Jul 28, 2008