Davies' research interests are theoretical physics, cosmology and astrobiology; his research has been mainly in the area of quantum field theory in curved spacetime. His notable contributions are the so-called Fulling–Davies–Unruh effect, according to which an observer accelerating through empty space will be subject to a bath of induced thermal radiation, and the Bunch–Davies vacuum state, often used as the basis for explaining the fluctuations in the cosmic background radiation left over from the Big Bang. A paper co-authored with Stephen Fulling and William Unruh was the first to suggest that black holes evaporating via the Hawking effect lose mass as a result of a flux of negative energy streaming into the hole from the surrounding space. Davies has had a longstanding association with the problem of time's arrow, and has also identified the mystery of ‘dark energy’ as one of the most important issues facing fundamental science. Davies was also an early proponent of the theory that life on Earth may have come from Mars cocooned in rocks ejected by asteroid and comet impacts. He is also a propagator of scientific research and technology development in order to prevent future comet impacts threatening the development or existence of humankind. He proposed that a one-way trip to Mars could be a viable option in the future. During his time in Australia he helped establish the Australian Centre for Astrobiology.
