First thing i want to do is tell you what i do know. I know to that astronomers use a standard candle such as a Type 1a supernova or a cephied varibale because they are always the same brightness. I know that a light source is four times less bright when it is twice as distant. I know that they use supernovae to calculate the distances of galaxies using this information. The problem is for this method to work then surely they needed to know the distance to the original supernova. How do they measure the distance of the original original light source they are using as a standard candle?