The speed of the galaxy moving away is proportional to its distance away. Hubble created the equation distance/time per mega parsec (3.26 million light years) to show how it’s expanding. Evidence to theory Red Shift Red Shift is the idea that when a galaxy moves away from us it tends to shift toward the red section of the Electro Magnetic spectrum, when a galaxy moves toward us it shifts toward the blue end.
Hubble used this to support expansion. Scientists found this by examining light waves when galaxies and stars move away they show a red shift in the light they give off. In the graph above you can see that the wave lengths at the red side of the spectrum are longer while when you get closer to the blue end the wave lengths get shorter. Scientists observed that when a galaxy moves away its wave lengths get longer shifting to the red end of the spectrum. When a galaxy moves closer to earth its wave lengths get shorter shifting towards the blue end of the spectrum. Since all the galaxies beyond ours show a red shift it is believed that the universe is expanding, this evidence supports the Big Bang theory.
Evidence to the theory CMBR There are many pieces of evidence supporting the Big Bang theory such as Cosmic microwave background radiation, also known as CMBR. Cosmic microwave background is the afterglow radiation that was left over after the big bang. Scientists use this as evidence because there are traces of the radiation all across the universe. This type of radiation shifts toward the microwave section of the Electro Magnetic Spectrum. Microwaves are invisible to the naked eye, though if we could see them there would be uniformed lines all over the sky in every direction. The temperature of and location of CMB rays across the sky are very uniform, but there are extremely tiny fluctuations in them. These fluctuations offer amazing insight on the origin of our universe. Limitations to the Big Bang Theory Although the Big Bang Theory has successfully explained the cosmic microwave background radiation and expansion, it has three significant problems such as The flatness problem, the horizon problem, and the monopole problem.
The Flatness Problem:
WMAP has determined the shape of the universe to be nearly flat. However, according to Big Bang cosmology, curvature grows with time. A universe as flat as we see it today would have extremely different types of conditions in the past.
The Horizon Problem:
Distant parts of space in opposite directions of the sky are so far apart that, according to Big Bang expansion, they could never have been in contact with each other. This is because since the universe is so big the light travel time between them would exceed the age of the universe. Yet the uniformity of the cosmic microwave background temperature tells us that these regions had to have been in contact with each other in the past.
The Monopole Problem:
According to Big Bang cosmology there should have been a large number of heavy, stable magnetic monopoles in the beginning of the universe. However scientists have never found magnetic monopoles. So if they do in fact exist they are much rarer than the Big Bang theory predicts.
Solutions to these…