Stephen Hawking is a scientist.
Physics ( from [ φυσική , phusikḗ ( epistḗmē ) , knowledge of nature ] , from φύσις phúsis `` nature '' ) is the natural science that involves the study of matter and its motion and behavior through space and time , along with related concepts such as energy and force . One of the most fundamental scientific disciplines , the main goal of physics is to understand how the universe behaves . Quantum mechanics ( QM ; also known as quantum physics or quantum theory ) , including quantum field theory , is a branch of physics which is the fundamental theory of nature at small scales and low energy levels of atoms and subatomic particles . Stephen Hawking . Hawking was the first to set out a theory of cosmology explained by a union of the general theory of relativity and quantum mechanics .