Theories in Physics: Hubble's Law
Did you know that every interstellar object currently is moving away from Earth. From solar systems to galaxies, all of the objects that we see in the night sky are actually moving away from us at different rates or speeds. As scientists it is important for us to understand these speeds so we can better understand how our universe began and how it may end.
An important figure in the world of astronomy and physics was a man known as Edwin Hubble, who discovered the equation needed to determine the dominant motion that is the expansion of the universe. The recessional velocity of our universe was calculated by Hubble to be a value known as Hubble’s constant multiplied by the distance from earth to the galaxy or V = H0 D. Hubble’s constant is the expansion factor of the universe, discovered in 1929 by Edwin Hubble, and is equal to 500 km/sec/Mpc (Mpc means megaparsec, which is equal to 3,260,000 light years).
Usually galaxies follow the smooth expansion, but it has been noticed that the further away a galaxy is, the faster it will move away from Earth.
This is a graph depicting how by increasing the distance between a galaxy and the earth increases the recessional velocity of that galaxy. As you can see the majority of galaxies are extremely close to the line of best fit; however there is a large cluster of galaxies in the middle of the graph that share the same distance from earth but have varying recessional velocities.
This cluster of data on the graph is caused by a large cluster of galaxies like the Virgo cluster or the Hydra cluster. Galaxy clusters have higher recessional velocities due to the orbital motion around the center of the galaxy cluster which can be over 100 kilometers per second. Due to the orbital motion of galaxy clusters, Hubble’s law cannot be used to find the distance to the galaxy given the recessional velocity or the recessional velocity given the distance.
Hubble’s Law is important in our understanding of how the universe is expanding and how given time our role in the universe may change. Edwin Hubble beyond being an astronomer was also the man whom the Hubble telescope was named after. Today the Hubble telescope is in orbit around the earth and remains one of the most instrumental tools in modern day science, similar to the scientist it’s named after.
