Q&A: Cosmology

Q:
What does it mean when you say that we're seeing light from many years ago?

A:
Because the Universe is very big and the speed of light isn't infinite, it usually takes many, many years for light from a star or a galaxy to reach us. So, we are sometimes seeing these objects as they appeared millions or billions of years ago, when the Universe was considerably younger than it is now. That's why astronomy is sometimes a little like time travel, as you say!