Ask an astronomer what the hardest thing to do is in astronomy, and chances are they will say ‘measuring distance accurately.’  It is surprisingly difficult to take the light from stars we see and match them to a correct distance.  In the past we have used several different methods depending on how close a star is to us.  For the nearest stars we use parallax, which looks at the change in a star’s position as the Earth is on opposite sides of it’s orbit. All other methods rely on what we call the standard candle approach.  Let’s say you had...