Alan Head had many scientific interests. He was a mathematical physicist but was so widely read that he could turn his hand to almost anything that had a scientific basis. His achievements were in many fields: they ranged from a design for a giant radio telescope to writing a computer program to simulate the diffraction of electrons as they pass through a crystalline specimen containing defects on an atomic scale and to calculate the images produced by these defects; from the elastic properties of engineering materials to the aberrations in aplanatic, non-spherical lens systems; from the causes of fracture in solid state materials to the patented design for a refrigerator that obtains its cooling power by selectively radiating electromagnetic radiation through a ‘window’ in the Earth's atmosphere to outer space; from Galois theory to quantum computers. Perhaps his greatest success was the theory of fatigue in aluminium alloys used in the construction of jet aeroplanes. Not only was he able to establish the micromechanisms involved, but his analysis was also such that the time that the processes would take to produce a complete failure could be estimated. Without this analysis, commercial aviation as we know it today would have been totally unsafe. But knowing the effective lifetime of components and replacing them before the end of their lifetime meant that, provided that the relevant maintenance was performed diligently, travel by air could be safe. I think the project that gave Alan most pleasure was his understanding of Galois theory and being the first person to apply it to a practical case concerning the elastic anisotropy of crystalline materials (see the section below on the correspondence between Professor H. M. Edwards and Alan Head).
His work on fatigue and Galois theory epitomizes the value that Alan put on ‘theory’. Theory was only good if it led to a practical, useful result. Alan Head had a brilliant career, but his feet were always firmly on the ground. He was modest, quietly spoken and very approachable. He was a friend and mentor to many. There are more than 10 scientific topics (including those mentioned above) described in this short biography, and he made significant contributions to all of them. The memoir is in three parts: a narrative of Alan Head's life and career, recollections of him by his colleagues and family, and a list of his published works cited in the text.
Highly effective photon-to-cooling thermal device
