Big Bang Theory
The Big Bang theory is the main theory about the creation of the universe. there are a lot of theories, based on your beliefs. The big bang theory states that the universe started off as a hot dense ball of radiation about 10 billion years ago. an explosion started in its center and the matter expanded and cooled, creating elections, protons and neutrons. further expansion created atoms of gases like helium and hydrogen. some matter was denser than others and as they moved gravitation forces squeezed them together making galaxies and stars. This theory has evidence and this evidence is called "The Red Shift." A spectrometer is a instrument that measures the wavelength of light. the wavelength coming from most stars has shifted towards the red end of the spectrum. This is "The Red Shift" and this is evidence that the "Big Bang Theory" is true.
Steady State Theory
The "Steady State Theory" is a theory of the universe. This was the leading theory about the creation of the Universe until the "Big Bang Theory" was brought to attention. this theory states that the universe always existed, it as it was in the past and as it is in the future. This means the universe is infinitely old with no start and no end. This suggests that new matter is created everywhere this matter forms galaxies which slowly move away from each other. This theory has some attractive features such as the universe will never die and reform. this theory has much less supporters because the "Big Bang Theory" has evidence supporting it. This called the "Red Shift."