A hypothetical quantum or particle of time. It has been suggested that just as energy can only exist in very small packets or quanta, so time may also be quantal in nature. This idea is linked to the overall quantization of space and time, so that there exists a minimum spatial displacement, and a corresponding minimum time, the chronon, which would be the time needed for light to cross such a distance. One possibility is that under certain extreme physical conditions, such as those prevailing in and around a black hole, spacetime quantization effects could manifest themselves.
A leading advocate of the notion of chronons has been the physicist Robert Ehrlich of George Mason University. In 1976 Ehrlich noted1 that the lifetimes of all then known elementary particles were consistent with being an integral number of chronons, the magnitude of which he put at 2 × 10-23 s. But because it is impossible to measure very short lifetimes without relating them to the distance to which the particle is in some sense confined (a consequence of the Heisenberg uncertainty principle) Ehrlich turned his attention to the sizes of elementary particles and the minimum separation between colliding particles. The corresponding unit of length is set at 6.6 × 10-16 m.
If space and time are quantized in this way, it would suggest that space and time are only be defined at points in a four-dimensional lattice. Interestingly, this idea is the basis of lattice gauge theory, an approach used by some theorists to explain the confinement of quarks. But they would stop short of relating this to any physical reality: it is more in the nature of a computational device.
Related categories SPACE AND TIME
Source: "The graininess of space and time," New Scientist, 4 May 1978
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