It must have been terrifying being a medieval mariner with the firm knowledge that the world ended at the horizon - not to mention frustrating. Imagine being too afraid to sail off into the sunset. Christopher Columbus proved the world was not flat in 1492 when he discovered North America, and his fine work was given further credence when, on this day 480 years ago, the first ship managed to sail all the way around the world without falling off the edge.

Circumnavigation of the globe was achieved by one of Ferdinand Magellan’s five ships, the Victoria. Unfortunately, Magellan (after whom the Magellan Strait at the southern tip of South America is named) did not survive the journey, being felled by a poison arrow on the Philippine island of Mactan. He did, however, so enjoy a stretch of calm water he named it the Pacific, from the Latin word pacificus, meaning tranquil. Only one ship of the fleet, with just 22 crew remaining, made it home on September 6, 1522. It was a hard, long and tragic journey home but it does make for a fascinating read (www.mariner.orgagemagellan.html).

Four-hundred-and-seventy-eight years later, 17-year-old Australian Jesse Martin became the youngest person to circumnavigate the globe non-stop and unassisted - but that’s another story. In fact, it’s a book, called Lionheart by Jesse Martin and Ed Gannon (Allen amp; Unwin pound;6.99). A good biography is at www.achievers-odds.com.autopachieverjmartinfull.htm.

However, all of this (not to mention a few global satellite images, some of which can be found at http:visibleearth.nasa.gov) has failed to convince members of the International Flat Earth Research Society. Here is number 34 (edited) of the 100 reasons why they think the earth is flat: “If the Earth were a globe, there certainly would beI people who are HANGING DOWN, HEAD DOWNWARDS while we are standing head up? But since the theory allows to travel to those parts of the Earth where the people are said to stand head downward, and still to fancy ourselves to be heads upwards, and our friends whom we have left behind us to be heads downwards, it follows that the WHOLE THING IS A MYTH - A DREAM - A DELUSION - and a snare, and, instead of there being any evidence at all in this direction to substantiate this popular theory, it is plain proof that the Earth is Not A Globe.” Hmmm.

The IFERS has a map of what it believes the world is like. The North Pole is at the centre of a disc. At the outer edge lies the southern ice, a wall 50 metres high which no one has ever crossed. The Sun and Moon are only about 32 miles in diameter. They circle above the Earth in the vicinity of the equator, and their rising and setting are explained as “tricks of perspective”.

The society grew from the Universal Zetetic Society in the US and Great Britain, founded in 1832. It is not clear when the name changed but, at last count, the IFERS has nearly 4,000 worldwide members.

We may quietly chuckle at the beliefs of the IFERS, but it’s worth noting that no one has yet discovered a way of illustrating a round world on a flat map. For free downloadable modern flat maps, try www.worldatlas.comwebimageworldflata.htm Yet another website (www.strangehorizons.com200220020610medieval_maps.shtml) claims that Columbus’s discovery that the world was not flat is “preposterous”, instead suggesting that medieval people already knew the world was round and the modern assumption that they thought it was flat is all part of a 19th century reaction against the Catholic Church. As early as the 6th century bc, the Greeks suggested it was round, but never put it to the test. So, 480 years after the first circumnavigation it seems we not only can’t see eye to eye on whether the world is round - we can’t even agree on whether we ever thought it was flat.