  A model of discrete space-time is presented which is, in a sense, both
Lorentz invariant and has no restriction on the relative velocity between
particles (except v < c). The space-time has an inbuilt indeterminacy.
  Published originally as 'A quantisation of time', J. Phys. A: Math. Gen., 10,
2115, 1977; identical to the original, apart from one or two minor corrections,
and some simplification towards the end of Section 6. The paper presents a
discrete model of time, in which the latter comprises a succession of instants
which are identified as collisions with particles called chronons. Proper-time
intervals are discrete; the structure of space-time is given by a radar map and
has an inbuilt indeterminacy, which leads naturally to Heisenberg's uncertainty
principle. If I were writing this paper today I would identify the chronon with
the virtual Higgs boson. Without the latter all particles would be massless and
would follow null paths; there would be no such thing as proper time. Time is
an emergent phenomenon, and the Higgs boson is the agent of that emergence.
