The light from a distant galaxy shows that z = 0.11.Calculate the ratio size of the universe when the light was emittedsize of the universe at present
Question
The light from a distant galaxy shows that z = 0.11. Calculate the ratio size of the universe when the light was emitted to the size of the universe at present.
Solution
The redshift z is a measure of the factor by which the universe has expanded since the light was emitted.
The scale factor of the universe at the time the light was emitted is given by 1/(1+z).
So, in this case, the scale factor at the time the light was emitted is 1/(1+0.11) = 0.9009.
This means that the universe was 0.9009 times its current size when the light was emitted.
So, the ratio of the size of the universe when the light was emitted to the size of the universe at present is 0.9009.
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