# How is the speed of galaxies determined?

Sep 16, 2015

This can be explained by The Hubble Law

#### Explanation:

According to Edwin Hubble, the most distant galaxies are receding from us at speeds proportionate to their distances. This is called Redshift. This means the further the galaxy is from us the faster it is moving away from us. Redshift can be given by.

$v = c z$
where,

• c is the speed of light.
• z is the redshift.
• v is the speed of the object.

Redshift can be calculated from the spectrum of the star or galaxy obtained from a telescope and comparing it laboratories values.

Formula for Redshift.

$\frac{\lambda \left(o\right) - \lambda \left(l\right)}{\lambda \left(l\right)}$
where,

• λ(l) is the wavelength at rest(in laboratory spectrum)
• λ(o) is the wavelength observed through a telescope