The Bondi Approach to the Lorentz

This article summarises a very elegant way of teaching the Lorentz transformation, which was introduced by Hermann Bondi (see Resonance, March 2016 for more about him). The starting point of this approach is that the best way of assigning space and time coordinates to a distant event is by radar, i.e., by transmitting and receiving light signals, and noting the times of departure and arrival. There is no need for the rigid rod. Bondi’s method, which he called the k-calculus, makes good use of the Doppler effect (hence the delta in the title). For students who have learnt special relativity in the standard way, this approach provides a different view of the subject.