SINCE the dawn of human existence, people have lived by the rising and setting of the sun - but now American corporations want to change for ever the way time is measured.
An international argument has developed between British astronomers and scientists working for American telecommunications firms who have called for the abolition of the "leap second" - the additional time unit used to keep modern atomic time-measuring systems in line with the earth's movement round the sun.
Removing that extra second would make some communication systems run more smoothly, but very slowly the clock would start to fall out of sync with the sun, eventually leading to 12 noon falling in the middle of the night.
The Royal Astronomical Society says the proposal has been raised by United States firms involved with the Global Positioning System, because design flaws mean GPS struggles to cope with leap seconds.
But the astronomers say losing the extra time would disrupt many other communications and "disconnect people" from the rotation of the earth.
Mike Hapgood, secretary of the RAS, said: "It's breaking the link between human time and the natural world."
It would be thousands of years before the change had a noticeable impact on the correlation between the clock and daylight, but the astronomers say it would immediately effect scientific projects, such as the satellite system used to track the progress of Hurricane Katrina.
The proposals to abolish the leap second from 2007 are to be discussed at a meeting of the International Telecommunications Union in Geneva.
Dr Hapgood said: "This proposal is from the US precision timing people involved with GPS, which was never designed very well to handle leap seconds - although it could have been. They need to think again.
"We've followed the rules and they work for most situations."
There have been 21 leap seconds since 1972 and the next is planned at the end of 2005.
Their use is determined by the International Earth Rotation Service, sponsored by scientific bodies.
Those seeking to end the leap second say it causes problems such as GPS receivers losing track while the system adapts.