The real millennium bug

Will visitors to London's new billion-dollar Millennium Dome be celebrating in the wrong place? Tom Standage investigates

VISIT GREENWICH, the part of London where I live, and you'll notice a significant addition to its distinctive skyline. The Cutty Sark, a nineteenth-century tea clipper, still sits in its dry dock; the Old Royal Observatory, birthplace of Greenwich Mean Time and home to the meridian that separates the eastern and western hemispheres, is still perched at the top of the hill; the Royal Naval College, with its distinctive domes and columns and a wrought-iron gate that is opened only for royalty, still commands the riverfront. But directly to the north of historic Greenwich, on the peninsula that extends into the bend of the River Thames, a new construction has been taking shape over the past two years: the Millennium Dome, a vast white, tent-like structure whose distinctive yellow trusses, extending into the air like the legs of a huge crouching spider, can be seen from all over London.

Greenwich was chosen as the logical site for Britain's official celebration of the new millennium because it is the home of the internationally-recognized meridian, the line of zero longitude from which space (and hence time) are traditionally measured. On December 31st the Dome will be opened in a gala ceremony attended by the Queen, the Prime Minister, and a few thousand hand-picked assorted nobs and gentry. Its multiple exhibition zones, complemented with live performances in a central arena, will then remain open to the public throughout the year 2000.

But there's a problem. Despite these impressive-sounding plans, the Dome is widely seen in Britain as a white elephant. For a start, it will end up costing around $1 billion -- more than six times the cost of the stunning new Guggenheim Museum in Bilbao. Yet compared to the Guggenheim's innovative concrete-and-titanium structure, which looks as though it was built by visiting aliens, the Dome is merely a temporary construction that resembles a huge marquee. There is even a huge hole in the roof to prevent fumes from an underground car tunnel's ventilation duct from gassing visitors with noxious fumes -- a hole that was, for some reason, omitted from all the artist's impressions and computer models of the finished Dome, even though the duct has been there for years.

Grumblers about the Dome are concerned with more than just the hole in the roof. The exact form of the Dome's exhibition areas has only recently been decided, after much wrangling. Would the 100 meter-tall human form in the Body Zone be male, female, or a couple, and would there or would there not be genitalia? Would the Spirit Zone risk offending the Church of England by presenting Christianity as just one of many faiths in today's multicultural Britain, or would it risk offending other faiths, by giving Christians pride of place? (Archbishops and Op-Ed columnists thundered for months over that one.) Meanwhile, the new underground "tube" line being built to ferry the expected millions of visitors to the Dome has been subject to repeated delays. It was supposed to have opened two years ago, and still isn't ready -- and the latest suggestion is that it will only just be ready to operate a limited service by the end of the year. Worse still, surveys consistently show that the British public would much rather the millions being lavished on the Dome were spent on education or the health service. In one poll, fewer than half of those asked said they thought the Dome was an "appropriate" way to mark the Millennium.

My beef with the Dome, however, is different. Sure, I'd sooner have had six Guggenheims, but it's too late for that now. As for the content of the silly exhibitions, I'm not too bothered. No, mine is a more scientific objection. The whole reason for building the Dome in Greenwich in the first place is the meridian, the line of longitude zero, which cuts through the peninsula where the Dome is sited. Right next to the Dome a Meridian Walk is being built and, where the meridian hits the water of the Thames, a Meridian Pier, where visitors will disembark from river taxis. The meridian is the Dome's very raison d'etre -- yet amid the confusion over Body Zones and tube lines, nobody seems to have noticed that the meridian, a supposedly fixed reference point, has moved.

AS ANYONE who has read Dava Sobel's best-selling Longitude will know, the long brass strip sunk into the cobbles of the courtyard of the Old Royal Observatory in Greenwich marks a very special line. Originally ruled by Sir George Airy, the Astronomer Royal, in 1851, this north-south meridian was intended as a reference for timing the transits of stars and planets. In particular, the transit of the sun each day, signifying local noon, was used to define Greenwich Mean Time. By carrying a chronometer set to GMT on board a ship and observing the time difference between Greenwich time and local time (again, measured by a noon transit), navigators could determine their longitude at sea. (French sailors, similarly, carried chronometers set to Paris time, measured at the Bureau des Longitudes, which has its own meridian.)

In 1884, an international convention gathered in Washington, DC to determine which of the various meridians around the world should be adopted as the global Prime Meridian so that maps and charts could be standardized on a single definition of longitude zero. Since three-quarters of the charts then in existence took the Greenwich meridian as longitude zero -- a hangover from Britain's days as the dominant naval power -- it was, to the chagrin of the French, Airy's meridian that was chosen, thus becoming the dividing line between the eastern and western hemispheres.

Airy's meridian has since become quite a tourist attraction. Visitors from all over the world come to have their pictures taken outside the observatory with one leg on each side of the line, which has been marked since the 1970s by a brass strip. Since the meridian is the line from which time is measured, the Old Royal Observatory has long promoted the idea that Greenwich marks "the official start of the new millennium." A couple of years ago a countdown clock was installed on the observatory wall over the meridian line, ticking away the seconds to the year 2000. And when the Dome opens, the meridian will also be marked, and no doubt having your picture taken as you stand astride it will become an indispensable part of any visit to the Dome as well.

But the truth is that time and space are no longer bound together at Greenwich, as some of the tourists who visit the meridian have already noticed. As they pull out their handheld Global Positioning Satellite receivers and ask the orbiting network of satellites their precise longitude, they are rather surprised to find that, according to GPS, the Greenwich meridian actually lies slightly to the west of longitude zero; and the true dividing line between east and west lies 334 feet to the east.

This is because, when the GPS system was established, a compromise was devised so that none of the various grid systems and meridians used around the world would differ too much from the GPS system's own grid, which is called WGS84. This compromise was necessary because of slight errors in the relative alignments of these grids, and because of the simplified mathematical model used by GPS to approximate the shape of the earth and the position of its center of mass. In order to work at all, the GPS system also uses extremely accurate atomic clocks, governed by the International Earth Rotation Service (IERS) in Paris. The result is that latitudes and longitudes determined by GPS differ slightly from those determined by the old-fashioned grid systems and the surveying methods it has replaced.

So what? Well, the whole reason why Airy's meridian was chosen as the Prime Meridian was that his was the most-used meridian; in other words, its legitimacy stemmed from usage. But today nobody uses the Airy meridian. Ships have been using GPS for years, and on January 1st, 1998 it became the standard for air navigation too. (This meant re-surveying the world's major airports, to work out the relationship between the old local grids and the new GPS grid.) Although there has been no longitude convention, WGS84 has effectively been declared the new world standard.

Oddly enough, this would not be the first time that the Greenwich meridian has moved. In fact, Airy's line superseded three older meridians defined by his predecessors. John Flamsteed, the first Astronomer Royal, laid down the first Greenwich meridian in 1685 as the continuation of the spider's-web crosshairs in his telescope. Then in 1725 Sir Edmond Halley, of cometary fame, found that Flamsteed's telescope was sinking into the ground, and established a new telescope -- and a new meridian -- 73 inches to the east. In 1750 James Bradley, another Astronomer Royal, established a third meridian 436 inches further east.

And then in 1851 Airy ruled his own line in the sand a further 19ft to the east, and it was that line which became the Prime Meridian. So the fact that it has now been usurped by the WGS84 meridian 334ft further east still is entirely consistent with historical practice. The line of zero longitude is still in Greenwich; just don't expect to find it as you wander around Greenwich Park with your GPS receiver. There is nothing on the ground marking the new Prime Meridian; just a small tree, and a rubbish bin. The meridian may have moved, but the Old Royal Observatory, official advisor to the Millennium Dome and exhibition, simply doesn't want to know.

"IT MAY BE THAT more people are using those other meridians, but it doesn't supersede the authority of this meridian," says Maria Blyzinsky, curator of astronomy at the Old Royal Observatory. "There hasn't been an international treaty saying 'Sorry, you're out'." Airy's meridian, she insists, is "the only one with history and certainty behind it." But surely the whole point of millennium celebrations, including the Dome and its futuristic exhibits, is to look forward, rather than backward? "I would still defend our meridian -- we are the official starting point of the millennium in the view of the 1884 conference," says Blyzinsky.

This is a pity. Instead of doggedly defending Airy's brass strip, the Dome exhibition could include a meridian boulevard, a historical display showing the positions of the various meridians that have been ruled in Greenwich over the years, as testament to the history of international co-operation in navigation and surveying. But no. Rather than embrace a new global standard, the Observatory has advised the Dome's organizers to venerate a relic from Britain's imperial past.

Terry Watts, a Greenwich-based artist who has long had a personal interest in the meridian, believes the Old Royal Observatory is making a fool of itself by refusing to acknowledge the new meridian. "The one thing that is clear in all of this is that Airy's meridian is not the one in use," he says. "Throughout its history the Observatory has been meticulous about accuracy. Now they are prostituting scientific rigor for entertainment value. If we're talking about Disneyland, fine. But we're not. The whole business is a fascinating ongoing story, and they are trying to fossilize it."

Perhaps strangest of all is the response of Terence Gibbons, a spokesman for the New Millennium Experience Company, the organizers of the Millennium Dome exhibition. He insists Airy's meridian is "the most internationally recognized," even if it is in the wrong place. "It's the representation of it that's important, not the precise degrees longitude," he says.

Quibbling over the meridian's precise location may smack of pedantry, but Airy was himself a stickler for accuracy, particularly when it came to the scientific instruments he used to make his measurements. "If it is not fine," he once remarked, "it is of no use to anybody." And the truth is that Greenwich no longer rules space or time. Even the countdown clock at the Old Royal Observatory gets the time from the GPS system. And if GPS can be believed when it comes to measuring time, why not when measuring space? If Airy were still around today, I suspect that he would have abandoned his meridian long ago -- brass strip or no.

Tom Standage is the science correspondent at The Economist and author of The Victorian Internet: The Remarkable Story Of The Telegraph And The Nineteenth Century's Online Pioneers (Walker).

©1998 FEED Magazine