When we make an observation of a distant galaxy 10 billion light-years away, we are seeing this galaxy as it
A) is right now
B) was when the universe was only 10 billion years old
C) was when the universe was formed
D) was when the universe was only 4 billion years old

Question

Quizplus · Accepted Answer

Light from the galaxy has taken 10 billion years to reach us, so we see it as it was 10 billion years ago. Given the universe is approximately 13.8 billion years old, the universe was about 3.8 billion years old at that time.

When We Make an Observation of a Distant Galaxy 10