Roadmap Science Challenge
D:1. How do the laws of physics work when driven to the extremes?
We can learn an immense amount about physics in extreme conditions by studying astrophysical environments where such conditions are commonplace. These include compact objects such as neutron stars, pulsars, quasars and black holes (see Science Challenge D3), as well as transient phenomena such as supernovae and gamma-ray bursts. The early universe is also an ideal laboratory for studying such conditions, using observations of the Cosmic Microwave Background radiation.