Tom Armitage is a PhD student from the Jodrell Bank Centre for Astrophysics at the University of Manchester. Tom’s work focuses on weighing galaxy clusters, the most massive objects in the Universe. This is tricky as galaxy clusters are billions of light years away and are made of ~80% dark matter, ~15% gas which is 100 million degrees and emits lots of X-rays and only ~5% of the cluster mass is actually made of galaxies! Tom tests new techniques to weigh clusters in set of new simulations called C-EAGLE, to see which ones are the most accurate.