The light from even our nearest stellar neighbour takes four years to reach us. When we look at the stars, we are looking back in time. This is an incredible gift. We can see parts of space, parts of our universe, as they were many years ago. The further we can collect light from, the further back in time we can look. If you look at the bright star Betelgeuse, which glows in the Orion constellation, you wind time back more than six hundred years. Its reddish glow started its journey to Earth in the Middle Ages. The stars in Orion's belt are even further away. Their light, familiar to generations of humans, has travelled at least 1,000 years to reach us. This means we have a chance of understanding the history of the universe because we can see the more distant parts of it as they were in the past, thousands or millions or billions of years ago.