Thanks to Daniel Whiteson for the answer!

James - When cosmologists gaze into space, they're looking at the stars and galaxies as they were long ago. This is because light travels at a finite speed. And given the huge distances it has to travel to reach our telescopes and eyes, it's often taken millions of years to reach us. In addition, and crucial to your question, Darren, the universe is expanding. Here's Daniel Whiteson, particle physicist at the University of California in Irvine.