Hubble’s law
Edwin Hubble looked at the light from galaxies further away from Earth and realised that the dark absorption lines showed greater red shifts. He concluded that distant galaxies had bigger red shifts because they were moving away faster.
The greater the distance from Earth, the bigger the red shift of the absorption lines.
Hubble used the red shift to calculate the velocities of galaxies against their distance from Earth.
When the data was put into a graph it showed a straight line through the origin.
This shows that the velocity of a galaxy is directly proportional to its distance away from Earth. In other words, if the distance of the galaxy away from us doubles, so does its The velocity away from an observer..
This is Hubble’s law.
The Hubble constant (H) is the gradient of the graph. \(\frac{1}{\text{H}}\) gives us the age of the Universe – currently thought to be around 13.7 billion years.
As the recessional velocity increases with the distance of the galaxy, it implies that all the galaxies originated from a single point.
