Last updated at 12:23 AM on 4th October 2011
You'd have to have a heart of stone not to feel a shiver of childish excitement as you stand on the metal strip marking the Prime Meridian at Greenwich.
From there, overlooking the East End of London, you can straddle the world, one foot in the Eastern hemisphere, another in the West.
The place is steeped in history. It is home to the most famous observatory in the world, to beautiful clocks that allowed sailors to explore the seas with safety, and to the Greenwich Meridian, the line that divides the world.
Man of his time: Michael Gambon as John Harrison in TV's Longitude
For nearly 130 years it's also been home to time itself.
The moment when the sun passes its highest point at Greenwich is noon Greenwich Mean Time.
And GMT is the standard that is used to set every timepiece in the world.
It's even the official time zone for outer space.
When astronauts wake up on the International Space Station, they don't follow Moscow or Washington time, they wake up to GMT.
But all that could soon change. Bureaucrats at the International Telecommunications Union in Geneva want to abandon GMT as the world's standard time.
For the first time in history, global time will no longer be linked to the spinning of the Earth. Instead, it will be determined solely by the ticking of atomic clocks.
If plans are voted through in January, the new guardians of time will be the International Bureau of Weights and Measures in Paris. It would be a bitter blow for British pride and — to make matters far worse — a belated victory for the French.
Exactly 100 years ago, French politicians were forced by international pressure to abandon Paris Mean Time and accept that the time in Lyons, Angers and Grenoble was determined by the sun moving overhead in London.
The meridian line: The Prime Meridian Plaque at The Royal Observatory in Greenwich, London
Suffice to say that the end of GMT as the world's benchmark for time would not be mourned in Paris.
Britain has a proud history of horology, the science of clocks and timekeeping.
The first known mechanical clock in Europe was made in 1283 for Dunstable Priory, Bedfordshire. Salisbury Cathedral is home to the oldest working clock in the world — an iron mechanism built in 1386, which gains or loses only a quarter of an hour per day.
Perhaps the single greatest British contribution to timekeeping came from John Harrison, a self-educated clockmaker who invented the first working ship's chronometer (a scientifically accurate timepiece).
All sailors, whether they use sextants and maps or global positioning satellites, navigate by latitude and longitude.
As every schoolchild was once told, circles of latitude run horizontally around the world, while circles of longitude — or meridians — run vertically, passing through the north and south poles.
Since the earliest sea voyages, sailors have been able to locate latitude — their position north or south of the Equator — by the length of day, the position of the stars, or the location of the sun at midday.
But working out longitude is much harder. To do so, a sailor needs two things — a fixed line of longitude, or 'home meridian', to act as a reference point and an accurate clock.
To find out longitude, a navigator must compare the time onboard ship (worked out by the sun) with the time at the home meridian.
An hour's difference between local time and the time at the fixed meridian is the same as 15 degrees longitude east or west.
The trouble was that in an era of pendulum clocks, keeping accurate time at sea, was impossible.
The motion of the ship, changes in temperature, even the salty air, would cause them to slow down or speed up.
Without accurate navigation, seafaring is obviously perilous. And only with accurate clocks could seafarers work out their longitude and navigate.
Harrison devoted his life to creating a watch that had no pendulum, needed no cleaning or lubrication and which worked now matter how rough the seas.
Childish excitement: The metal strip which marks the Prime Meridian at Greenwich
It took 40 years of battling with bureaucracy and rivals before his achievements were recognised and he was awarded his rightful cash prize from the Government in 1773.
His clocks were accurate to 0.06 seconds every day and — by helping sailors conquer the seas — saved countless lives.
But Britain didn't just come up with the first seafaring watch. It also invented the concept of standard time.
That might sound like patriotic hyperbole, but the idea that the time can be the same across an entire country is relatively recent.
Before the telegraph and the railway, when the quickest way to send a message or a person was on horseback, people worked out the time from the position of the sun overhead.
That meant every town had its own local time. In Plymouth 'real noon' — the point when the sun is at its highest — comes 17 minutes after London's noon.
For most of our history, the difference didn't matter. But the arrival of the railways changed that.
Timetabling journeys where every station has its own local time was a nightmare.
A traveller heading from London to Plymouth would need to reset his fob watch at every station along their journey.
The Victorians got around the problem by abolishing local time. The Great Western Railway was the first to introduce a standard 'Railway Time' in 1840 and others followed.
And when searching for a sensible standard, what better choice than the time at Greenwich — home of the Royal Observatory since 1675 and keeper of the most accurate astronomical records in the world?
By 1855 more than nine out of ten towns in Britain were operating on Greenwich Mean Time.
There was stubborn local resistance. Some town clocks — such as ones in Oxford and Bristol — continued to show local time as well as newfangled GMT.
Others refused to accept GMT at all. But by 1880, when GMT was officially adopted by the Government, the battle was won.
GMT went global four years later at the International Meridian Conference in Washington.
Persuaded by Britain, the world agreed to accept the Greenwich Meridian as the zero point for longitude — and GMT as the benchmark for world time.
Inevitably, not every country was willing to adopt British time as the world standard.
At the conference, France had proposed Paris as the home of the Prime Meridian. Snubbed and smarting, the French refused to adopt the new time, and declared they were following Paris Mean Time in 1891.
Their independence lasted just 20 years. In 1911, the French Parliament sulkily abandoned Paris Mean Time and moved in line with the rest of the world.
But rather than acknowledge the British source of their new time, legislators simply announced that the new official time would be 'Paris Mean Time' .?.?. retarded by nine minutes and 21 seconds. This neatly avoided mentioning the non-French word 'Greenwich'.
By the 1920s most countries had adopted the time zones based on GMT.
But just as GMT took over the world, the seeds of its doom were sowed. In the 1920s electric clocks were invented that told time more accurately than the rotation of the world.
In the next few decades new quartz and atomic clocks — which lose just one second in 20 million years — confirmed that the Earth's rotation is irregular.
The gravitational pull of the Sun and Moon, plus changes in the molten rock beneath our feet, cause tiny braking and accelerating effects. The Earth's spin is also slowing down.
These irregularities can wreak havoc with modern-day GPS and computer systems.
So to stop atomic time getting out of synch with global time scientists introduced a fix.
Every few years they introduce a 'leap second' into the global time keeping system. The owners of atomic clocks are given six months' notice that time needs to be adjusted to keep pace with the vagaries of the Earth's spin.
This last leap second was in 2008.
The fix has worked, but it has not satisfied the bureaucrats. The French-based Bureau of Weights and Measures — supported by America — has long argued that the introduction of leap seconds carries a risk of an error being introduced.
Rather that keep tweaking atomic clocks to make them match the rotation of the Earth, it wants to let them run with no connection to GMT.
That means as the Earth's rotation slows, real days — measured by the rising and setting of the sun — would become longer than standard days.
But the bureaucrats say that could be corrected by inserting a minute every 50 to 100 years. Larger corrections every few decades are less likely to cause mistakes.
The Government is lobbying against the move to scrap leap seconds, suspecting an undercurrent of nationalism at play.
Science Minister David Willetts said: 'We should stick to real time as experienced by humans, which is based on the Earth's rotation, not atomic clocks.'
David Rooney, curator at the Science Museum and former curator at Greenwich Observatory, believes scrapping the link with real time and standard time is a mistake.
'It would be bold cultural move. We are human beings. We are hard-wired to the time set by the Sun,' he said.
If this plan went ahead, it would be the first time in human history that there was no connection with the time of our clocks and the rotation of the Earth.
That's why a ticking time bomb should be attached to France's plan to switch off GMT.
In our village we have a globe monument marking the line where the Greenwich Meridian passes, so not all the French want to call it Paris time!
- Alice Martin, Chalandray, Poitou Charentes, France, 04/10/2011 06:47
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