Jim was born in Baghdad on 20 September 1962 to an Iraqi father (an electrical engineer) and English mother (librarian). He grew up in Iraq with his brother and two sisters and they moved back permanently to the UK in 1979. He married his wife Julie in 1986.

He studied physics at the University of Surrey and graduated with a B.Sc. in 1986. He then stayed on to pursue a Ph.D. in nuclear reaction theory, which he obtained in 1989. In that year he was awarded a Science and Engineering Research Council (SERC) postdoctoral fellowship at University College London. He returned to Surrey in 1991, first as a research assistant then lecturer. In 1994, he was awarded an Engineering and Physical Sciences Research Council (EPSRC) Advanced Research Fellowship for five years, during which time he established himself as a leading expert on the structure of neutron halo nuclei (atomic nuclei exhibiting the unusual feature of having one or two loosely bound neutrons orbiting the rest of the nucleus). He continues to publish papers in this field and work within the nuclear theory research group at Surrey. He currently supervises or co-supervise six PhD students.

In 2000, he was promoted to senior lecturer at Surrey (associate professor) and then to full professor of physics in 2005. He also hold the first University of Surrey chair in the Public Engagement in Science. In 2006, he was awarded an EPSRC Senior Media Fellowship allowing him to pursue science communication activities in earnest alongside his other academic duties.

He has lectured widely both in the UK and around the world, particularly for the British Council for whom he now acts as a senior advisor on science and technology.

He has written a number of popular science books, which have between them been translated into thirteen languages.

As a broadcaster, he appears regularly on television and radio. In the summer of 2007, He will be presenting the three-part series, ATOM – on the history of our understanding of the atom and atomic physics – on BBC4 television.

He is an honourary fellow and trustee of the British Association for the Advancement of Science as well as a member of its Council. He is also a Fellow of both the Royal Astronomical Society and the Institute of Physics from whom he received, in 2000, the Institute's Public Awareness of Physics Award.