What are gamma-ray bursts? How do black holes form? Can we directly detect neutrinos from the relativistic jets in gamma-ray bursts? Can we detect gravitational waves from core collapse in a supernova or in a merger involving a black hole? What determines whether a core collapse becomes a black hole or a neutron star? The list goes on.
Exciting opportunities abound in the coming decade for exploring these fundamental questions, thanks to advances in applied physics and technology. A paradigm based on profound connections between cosmology and elementary particle physics—inflation along with cold dark matter—holds the promise of extending our understanding to an even more fundamental level and much earlier times and of shedding light on the unification of the forces and particles of nature. As we enter the 21st century, a flood of observations is testing this paradigm.