There has been a most remarkable improvement in the accuracy to which time can be measured since WW2. And the ability to measure beyond microseconds to nanoseconds and picoseconds is essential to the Internet, GPS navigation and financial transactions – in fact, to modern life. But about a hundred years ago it was found that the rotation of the Earth was not constant, and that units of time based on a measured day were not consistent. Astronomers first tried to define a unit of time from the orbital periods of the planets, and consistency was later assured with the introduction of atomic clocks. The mismatch between measured timescales and the length of a day persist, however, and are currently resolved by the occasional use of “leap seconds”. But this can create difficulties in the operation of sat-nav and other systems requiring consistency and predictability in timescales – problems which have still not been resolved.
This talk will cover the history of time measurement, the origins of the current difficulties and ways in which they might be overcome.
Light refreshments will be served before the talk.