Why we measure distances

Measuring distances in astronomy is very important for many reasons. If we know the distance to an object we can learn more about:

• Its size. Until we know the distance we only know how big something looks, but the further away something is the smaller it seems to be.
• The energy it creates. Again, the further away something is, the fainter it seems to be. If we know how far away it is, we can work out how much energy it is actually generating, which will help us to understand the Physics of what makes it work.
• Differences between objects. Two objects might look different but actually be very similar, but with one further away than the other. This can make it very difficult to study them.