Messel was born in Canada of Ukrainian parents. He was brought up in Levine Siding in Manitoba and attended Queen's University, Kingston, Ontario. During the Second World War he served as a paratrooper with the Canadian Forces.
Messel moved to Australia in 1951. He lectured in mathematical physics at the University of Adelaide 1951-52, before being appointed in 1952 as Professor of Physics and Head of the School of Physics at the University of Sydney, a position he held for 35 years until his retirement in 1987. In 1952 he established the Nuclear Research Foundation, later known as the Science Foundation for Physics .
In 1962, Professor Messel started the International Science School (ISS), which aims to encourage scientifically capable and interested students in their final two years of school to extend their knowledge and apply it to achieve progress. He has frequently stated his discontent when sportsmen were praised and hailed whereas the next generation of scientists to change and run the world were given little to no encouragement. Over the past 51 years, over 4000 scholars have attended the ISS. For the past few years, the program has run once every two years with close to 150 students from up to 10 countries staying at the Women's College for two weeks, attending lectures and participating in activities around the University of Sydney.
- Commander of the Order of the British Empire (CBE), New Year's Honours 1979
- Companion of the Order of Australia (AC), Australia Day Honours 2006, the citation reading: For service to Australian science and to education as an outstanding educator raising awareness of the importance of the study of science and in particular physics, for instrumental contributions to improving science teaching in schools, and for conservation advocacy relating to endangered crocodile and alligator species.