Alfred Arthur Robb FRS[1] (18 January 1873 in Belfast – 14 December 1936 in Castlereagh) was a Northern Irish physicist.
[3] He then proceeded to University of Göttingen, where, guided by Woldemar Voigt, he wrote his dissertation on the Zeeman effect.
The Croix de Guerre was awarded to him for WWI service in the Red Cross, and in 1921 he became a fellow of the Royal Society.
[1][4] He is known for his four books on special relativity (1911, 1914, 1921, 1936) where he gave a spacetime derivation of the theory in an axiomatic-geometric way.
In the first of these works he used a hyperbolic angle ω to introduce the concept of rapidity[6]: 9 and showed that the kinematic space of velocities is hyperbolic, so that "instead of a Euclidean triangle of velocities, we get a Lobachevski triangle of rapidities".