Joel began his talk by giving us an overview of supernovae (SNe) and their role in cosmology as standardizable candles. After showing us the very impressive existing results, Joel pointed out that we have reached a stage where systematic and statistical errors are of comparable size. As a result we must make progress in understanding both in order to improve our measurement of cosmological parameters.
One particularly important systematic is cosmic dust. Joel explained the effects of dust (both reddens and lessens the light from supernovae) and its nature. He then moved on to explain the ways in which intergalactic dust can be constrain: from quasar colour and from x-ray halo scatter. Joel’s work involved considering both of these constraints simultaneously.
In the second half of his talk Joel discussed various aspects of the physics of dust in more detail and summarized the results of his work.