The Big Bang Theory
- Scientists have gathered a lot of evidence and information about the universe, and have used observations to develop the Big Bang Theory.
- The theory states that originally all the matter in the universe was concentrated into a single incredibly tiny point.
- This began to enlarge rapidly in a hot explosion and is still expanding today.
- Astromomers have even detected a cosmic microwave background radiation, that is thougut, to be the heat left over from the original explosion.
The Doppler Effect
When a source moves towards an observer, the observed wavelength decreases and the frequency increases.
When a source moves away from an observer, the observed wavelength increases and the frequency decreases.
Our Sun contains helium. We know this because there are black lines in the spectrum of the light from the sun where helium has absorbed light. These lines for he absorbtion spectrum for helium.
When we look at the spectrum of a distant star, we still see an absorption spectrum. However the pattern of lines has moved towards the red end of the spectrum, as you can see below.
Astronomers have found that the further from us a star is, the more its light is red-shifted. This tells us that galaxys are mving away from us, and that the further away a galazy is, the faster its moving away. Evidence for a generally expanding universe.