Question: Since we can only see because of the presence of light, if galaxies are millions of light years away, then aren't we technically seeing things that happened millions of years ago, because the light from the other galaxies would take a long time to reach us on Earth?

Imogen Whittam answered on 6 May 2020: last edited 7 May 2020 7:32 am

You’re right, when we look at distant galaxies we’re seeing what they looked like millions (or often billions) of years ago. But this is what makes it so exciting! We essentially get to travel back in time and see what the Universe looked like in the past, when it was much younger.

The key aim of my research is to understand how galaxies form, so by looking at really distant galaxies we’re looking at what these galaxies looked like millions of years ago, when they were much younger. By comparing these observations to images of galaxies closer to us, which are older, we can find out about how galaxies change during their lifetime.