Earlier this year, on July 20, we celebrated the 50th anniversary of the first landing on the moon. I wrote about it—well, mostly about the Apollo Guidance Computer—that day in my post The First Computer on the Moon. Increasingly, getting to the moon successfully with 1960s technology is looking more and more extraordinary. But that's not the topic for today.

450 years before Apollo 11 launched, the cutting-edge technology of the day for exploration was the sailing ship, and the cutting-edge guidance computer was a compass and astrolabe. Exactly 500 years ago today, September 20, 1519, Ferdinand Magellan's fleet of five ships set sail from Sanlúcar de Barrameda in Spain, going west across the Atlantic, seeking a western route to what is today Indonesia.

His voyage was financed by something close to venture capital. Magellan was Portuguese—his real name was Fernão de Magalhães. He tried to get the King of Portugal to fund the voyage without success. So he turned to the King of Spain. In 1494, Spain and Portugal had signed the Treaty of Tordesillas, splitting the newly discovered territories outside Europe between the two countries. There's a lot more to it than that, especially since the English and Dutch were not signatories and ignored it, but one important point was that the routes to Asia around Africa were owned by Portugal, but routes across the Atlantic were owned by Spain. So if Magellan successfully got to the Spice Islands (part of Indonesia today) by sailing west, it would potentially open up a new trade route for Spain that was not in violation of the treaty. So the King of Spain largely funded the voyage.

Only one of the ships, the Victoria, made it all the way around the world and back to Spain. Magellan himself was killed in a battle in what is now Lapu Lapu City in the Philippines. The fleet got there by sailing through the navigable strait between mainland South America and the Tierra del Fuego archipelago. This stretch of sea is now called the Strait of Magellan, although obviously was not back then. That took him into, and across, what he named the Mar Pacifico (in both Portuguese and Spanish), and we now know in English by the same name: the Pacific Ocean. He wasn't, in fact, the first European to reach the eastern Pacific Ocean. That was Vasco de Balboa who led an expedition over the Panama Isthmus in 1513, just a few years earlier. He named it Mar del Sur, the southern sea, but his name lost out to history (not least because the Pacific Ocean is more Pacific than South).

Circumnavigation

Since Magellan had previously visited the Malay Archipelago, the islands between Singapore and Australia, sailing East around Africa, and on this voyage he arrived there again sailing West across the Atlantic and across the Pacific, he is generally credited as being the first individual to make a personal circumnavigation of the world. Of course, he didn't do it in a single voyage, and he never got all the way to the Philippines on his first eastward voyage, so it is a bit dubious.

The real first circumnavigation of the world was by the rather less famous Juan Sebastián Elcano. That's him in the picture. He eventually took command of the Victoria after Magellan's death, and sailed it back to Spain, arriving on September 6, 1522 with 18 survivors from the original 250 men.

The next expedition to successfully circumnavigate the world was Francis Drake in 1580, decades later. He was the first person to complete the journey as captain from start to finish. He (probably) landed at Drake's Bay in Marin County in 1579 during the voyage.

Navigation

I wrote a lot about the Apollo Guidance Computer in my post about the Apollo 11 landing on the moon. In the Magellan era, navigation was done using astrolabe and compass. Everyone knows what a compass is, and why you need one for navigation.

An astrolabe is an instrument that can be used to measure the angle above the horizon of a given object such as the sun or a star. In the northern hemisphere, Polaris, the "pole star" is especially important since it is exactly on the axis around which the earth rotates and so if the pole star is X degrees above the horizon, then the ship is at X degrees latitude. In the southern hemisphere, there is a barely visible star with the same property, Polaris Australis. The sun's noon altitude can also be used to determine latitude, noon being when the sun is highest in the sky, so not requiring accurate clocks.

Longitude was much more problematic since it did require accurate clocks. You didn't just need to know when it was noon locally, you needed to know when it was noon in some reference location such as Greenwich, the difference in the times giving the difference in longitude (one hour = 15°).

Accurate clocks didn't appear until the invention of the marine chronometer by Harrison in the 18th century. Until then, the best approaches used observations of the patterns of the moons of Jupiter as a time reference but that didn't really work at sea with the motion of the ship since it wasn't possible to train a telescope accurately on Jupiter for long enough to make the observations. However, it worked from islands. You probably already know the story of measuring longitude from Dava Sobel's wonderful book Longitude and the TV series made from it.

If you are ever in London, I recommend a trip to Greenwich Observatory by going to the Cutty Sark station on the Dockland Light Railway, another association with sailing ships. There you can see Harrison's original chronometers and you can stand athwart the zero meridian which runs through the courtyard, with one foot in each hemisphere.

Or if you are in Edinburgh, Scotland, at precisely 1:00pm every day, they fire "the one o'clock gun" on the top of the wall of Edinburgh Castle, originally to allow all the ships in the Firth of Forth to synchronize their chronometers. It has been fired every day since 1861 (except Sundays, Christmas Days, and Good Fridays). A black ball is simultaneously dropped on the top of the Nelson Monument on Carlton Hill to give a visual time signal. In fact, the black ball started earlier. The gun was a later addition as a backup for when there was too much fog to see the ball. I took the video below from Princes Street. You can see the smoke from the gun (just to the right of the green tree) on the castle wall a second or so before you hear the gun (due to the speed of sound).

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