The Big Bang
Red-shift as Evidence for the Big Bang
People used to think that the Universe has always existed and the stars had always been in the same position, this was called the Steady State theory and existed into the mid-twentieth century. But then evidence from measurement of the light from distance galaxies changed this.
The universe is really old but it did have a beginning, when time and space started. Evidence for this has been found in star light, which is red-shifted because the space between galaxies is expanding.
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