Universe And Solar System The two most common beliefs of the formation of the Universe and Solar System are The Expanding Universe Theory and The Big Bang. There are some comparisons between the two and some contrasts. Almost all astronomers believe that the universe is expanding although they may have different theories on how this is happening. The Expanding Universe Theory is based on the Doppler Effect, the redshift of different galaxies and the assumption of the Hubble Law. The Doppler effect occurs when a wave-emmitting object moves toward or away from an observer and the sound has a change in pitch as the object continues to move.
For example the sound a police car siren when it comes from behind and passes you. The redshift of different galaxies is the change or shift in the light radiated by an object such as a star of galaxy that indicates the objects motion. Scientists have used redshifts to measure the speed and direction of distant galaxies. The Hubble law showed that the further away the galaxies were the higher the redshift was, that means the more distant galaxies were moving away at a much faster velocity than those closer to us. The Expanding Universe theory is merely an assumption by astronomers that all the galaxies in the universe are moving away from the earth.
The more distant the galaxy the faster its moving away from us. According to the Big Bang theory a gigantic explosion created the universe billions of years ago. It appeared that the universe we now see could be the remnants of an enormous explosion of the distant past.