You have taken a picture of a galaxy 1 billion light years away. That picture shows:
A) a galaxy that is 1 billion years old.
B) a galaxy that is 13 billion years old.
C) a galaxy as it was 1 billion years ago.
D) a galaxy that is 1 billion light years old.

Question

Quizplus · Accepted Answer

When we look at objects in space, we are looking back in time because light takes time to travel to us. If we are looking at a galaxy that is 1 billion light years away, the light we see from the galaxy left it 1 billion years ago. Therefore, we are seeing the galaxy as it was 1 billion years ago, which is the correct answer. Option A is not correct because we cannot determine the age of the galaxy just by looking at it. Option B is also not correct because the universe is estimated to be 13.8 billion years old, and we cannot see back to the beginning of time. Option D does not make sense because light does not have an age.

You Have Taken a Picture of a Galaxy 1 Billion