Everything we understand in science is based on no more than four fundamental forces. Gravity and electromagnetism are well known forces, and are sufficient for all chemical and biological phenomena. Physics, astrophysics and cosmology are greedier. Two additional forces were discovered in the first half of the twentieth century; the strong force which binds the atomic nucleus, and the weak force which allows the Sun to shine. In 1983 an experiment which collided matter with antimatter showed that the weak force and electromagnetism were actually aspects of the same force.
Peter Kalmus is Emeritus Professor of Physics at Queen Mary, University of London, UK. He has carried out research in particle physics at accelerators in the UK, USA, Germany and CERN, and is an author of 230 research publications. He was awarded the Rutherford Medal for his contribution to the discovery of the W and Z particles which showed that electromagnetism and the weak interaction were aspects of the same force. He received the Kelvin Medal and the EPS Outreach Prize for public understanding of physics, and an OBE for services to physics.