FOR THOSE in these increasingly frantic times for whom every second counts, the decision in Geneva today might appear monumental. Indeed, from the perspective of the history of science, the first decoupling of the measurement of time from the day and night of the earth’s rotation does have a landmark quality to it.
While the International Earth Rotation and Reference Systems Service (IERS) in Paris – the grand arbiter of time – has just announced that in this leap year a leap second will also be introduced on June 30th, the first since 2008, in Geneva today another organisation will probably decide to abolish the leap second altogether. The result will be that atomic clocks, accurate to one second in 100 million years, and now used as the standard reference measure of time, will gradually go out of sync with the rotation of the earth. The IERS in 1972 had introduced a leap second to bring the two measures back into perfect parity (known as Co-ordinated Universal Time, or UTC).The “second”, until now 1/86,400 of an average solar day, will be defined solely in terms of the oscillation frequency of an isotope of caesium (exactly 9,192,631,770 per second).
The problem is that the minor and irregular variation in the earth’s rotation cannot be programmed into computers years in advance, like the leap year, and necessitates a costly and potentially dangerous, periodic readjustment of thousands of those that require particular time-sensitivity. So, if the International Telecommunications Union (ITU) agrees to the change today, in hundreds of years well be a minute out of sync with the sun, and after several hundred thousand years we could be eating lunch in the middle of the night. Occasional adjustments every century or so will still be needed.
The 192-member ITU is the UN agency responsible for co-ordinating international communications standards and time is very important for synchronising radio communications and GPS systems. But some member states, notably Britain, China and Canada, are not convinced, preferring to keep the old link with astronomical time. They say that in 24 leap second introductions over 40 years there has been no evidence of problems. The US and France are leading the charge for its abolition.
For those out there who will worry, however, that precious moments may be about to be stolen from their lives, it is worth noting that what we are concerned with is only the measurement of time. Not its totality. Though that’s a distinction with which Einstein might have taken issue.