Land Ahoy! - Navigation at Sea in the Age of Sail

A few days ago, a friend of mine told me he’s thinking about buying a boat and learning how to sail it himself. He told me nowadays everybody keep sight of land at all times and just sail parallel to the shore, so it should be a piece of cake. When I asked him if he’ll be brave enough to go on a sea-crossing voyage without a GPS, he just smiled. That reminded me of the famous longitude problem.

In the 17th and 18th centuries, ships were crossing the vast oceans on regular bases, but often these journeys resulted in shipwrecks and loss of lives due to miscalculating the ship’s current location. Dead reckoning may be a good solution for short distances, but for long distances you need a way to know exactly where you are (within an acceptable margin of error). Although the ship’s current latitude had been relatively easy to find by reading the angle of a sextant aimed at the sun at its highest position in the sky, finding the ship’s longitude had been a much harder task. This problem was known as ‘The Longitude Problem’, and it was once though to be beyond human capabilities. Since the Board of Longitude has offered a large sum of money as a prize to the one who will solve the longitude problem, many had tried. But throughout the years, although many crazy solutions had been suggested, there had been only two that seemed at least partially sane.

The most popular proposition to solving this problem was known as ‘The Lunar Distance Method’. It was claimed that by creating extremely detailed tables of positions of the moon and the stars, it will be possible to calculate your exact longitude. Although using celestial bodies was a possible solution in theory, in practice, it produced errors of hundreds of miles, and therefore – useless to sailors.

Its rival proposition was to have a precise chronometer on board the ship. In theory, if you had a precise clock set to your home port local time, you could know your own longitude. For example, if the clock points to 1 PM when the sun is in its highest position in the sky, it means you are fifteen degrees west of your home port. The problem was to produce this extremely precise clock that will keep being reasonably accurate for long period of time while facing corrosion in salt air, wide variations in temperature and humidity, odd angles, and constant movement. Although thought to be an impossible task, one man, an English clockmaker named John Harrison, had managed to manufacture such a clock after years of relentless work (eventually reaching only two miles of error on a cross-Atlantic voyage). Not before a struggle had the Board of Longitude acknowledged Harrison’s solution and granted him his hard earned prize. The longitude problem was finally solved.

A modern GPS device relies on trilateration with satellites, using an accurate internal clock to measure its distance from these man-made artificial celestial bodies. I think it’s beautifully ironic that the modern solution to the exact location problem is some kind of a mixture between these two rival methods.

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p.s. If the Coriolis effect really affected draining sinks, plumbing was a big issue in Kenya.

1, 2, 3, God, 5, 6 - Why Do Clocks Use IIII Instead of IV?

Have you ever wondered why almost every modern clock or watch with Roman numerals uses ‘IIII’ instead of ‘IV’ to represent 4 o’clock? There are several possible explanations.

One likely explanation is that the strict use of IV instead of IIII wasn't common until after the Middle Ages. Clocks and watches are patterned after sundials, which were in use long before the Middle Ages.

Another likely explanation is that using IIII brings more symmetry and balance to the dial. The four-character form IIII is "heavier" than the IV and creates a visual symmetry with the "heavy" VIII on the other side. Another symmetry is achived because the I symbol would be the only symbol in the first 4 hours of the clock, the V symbol would only appear in the next 4 hours, and the X symbol only in the last 4 hours.

A practical reason can be that IV is difficult to read upside down and on an angle, particularly at that location on the clock (can be confused with VI).

Another reason is related to the molds used to cast the metal numbers. Using four I's instead of one I and one V will total in 20 I's, 4 V's, and 4 X's per one clock, so all the numbers could have been manufactured using one mold of 'I I I I I V X' four times.

There are some stories of several kings objecting to the IV form, but these seems unlikely.

But the most surprising explanation I’ve found would have to be this: In ancient Latin, ‘I’ was used instead of a ‘J’, and ‘V’ instead of a ‘U’. So ‘IV’ was an abbreviation for the Roman god Jupiter (IVPPITER) and using IV could have been considered sacrilegious. I guess the Romans thought 1, 2, 3, God, 5, 6… looks too weird on a sundial.

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p.s. Bringing your pet elephant to work is a bad idea, even if it is Casual Friday.