I observe a galaxy that is 100 million light-years away: what do I see?
A)the light from the galaxy as it is today,but it is blueshifted
B)the light from the galaxy as it is today,but it is redshifted
C)the light from the galaxy as it was 100 million years ago and it it blueshifted
D)the light from the galaxy as it was 100 million years ago and it is redshifted
E)Nothing: the galaxy lies beyond the cosmological horizon.

Question

Quizplus · Accepted Answer

Since the galaxy is 100 million light-years away, we will see the light from the galaxy as it was 100 million years ago. The light will be redshifted due to the expansion of the Universe, which causes the wavelengths of light to stretch out as they travel towards us.

I Observe a Galaxy That Is 100 Million Light-Years Away