In these days of GPS telling us every turn to take and where to find a parking spot when we get to our destination, it’s easy to forget that finding your way from Point A to Point B used to be a substantial challenge. Substantial enough, in fact, that one aspect of it was the subject of large cash prizes offered by national governments.
But let’s start with the simplest end, which is navigation via landmarks. Even now, this is often a key component of how we give directions: not just “turn right on Grove Street,” but “turn right at the Peet’s Coffee onto Grove Street.” Makes sense; businesses are often much easier to spot than our tiny little street signs. But the street signs are still necessary, because the person following the directions may well pass more than one Peet’s along the way.
Since there are no street signs in nature, navigation via landmarks is how it’s most often worked from time immemorial. Follow the river until it makes a large bend to the west; by then you’ll be able to see a range of hills. Aim yourself for the gap between the two tallest ones. Partway there you’ll reach a stand of beech trees. Skirt their edge and look east for the smoke that will signal the presence of our house.
We most often make reference to tall things, because they’re easy to see — which caused problems for white settlers on the Llano Estacado, one of the flattest regions on earth. The near-total lack of trees or even bushes there left them without landmarks by which to orient themselves. According to the article I read (twenty years ago, so the reference to back this up is long since lost), the Native Americans of the area made their way by looking not for things that went up, but things that went down: small depressions in the ground, that might become ponds and the like when it rained. Harder to spot at a distance, but still useful for orientation.
You might think the sea presents similar problems, and far enough out, it does. That’s why a great deal of sailing is done within sight of the coast, despite the risks posed by rocks, shoals, and lee shores. In areas where islands are closely spaced, it’s possible to hop from one to the next by plotting a connect-the-dots course between visible waypoints. And, as with the depressions on the Llano Estacado, looking down can be extremely useful — not just for navigation, but to protect your vessel. Running aground is dangerous. But the contours of the seabed can act like a map, telling you when to change course to reach your destination.
This contrasts with dead reckoning, which is the art of guessing your current position based on your last known fix, your direction of travel, and your speed and the time elapsed. This approach is part of what made sea travel in the past such a perilous art: captains far out at sea had to measure the speed of their vessels and eyeball the effects of forces like currents to estimate where they were. Errors in either the measurement or the guesswork part of the equation could mean a ship missed its destination entirely, with potentially fatal results.
Which is why people spent a lot of time figuring out better methods — many of which started with the sky. These days we talk in general terms about the sun rising in the east and setting in the west, but our ancestors tended to be much more aware of the seasonal variation in its movements, as well as the movements of the moon and the stars. Astronomy is one of the oldest sciences, and its significance was practical as well as spiritual.
But we also made tools to help us out. Like many technologies, simple compasses aren’t physically difficult to make; you just need the understanding that such a thing is possible. Someone in Han Dynasty China invented the earliest versions somewhere between the second century B.C. and the first century A.D. The development of the sextant was another major innovation in navigation, because it allowed for more precise calculation of one’s latitude or north-south position. Longitude, however — east-west positioning — posed a far more difficult problem, to the point where sizable rewards were offered to whoever could come up with a reliable and accurate method of determining one’s current coordinates, especially at sea. The history of how that was resolved is a fascinating rabbit hole I won’t fall down here, but it’s worth pointing out that Ryan North, the author of How to Invent Everything: A Survival Guide for the Stranded Time Traveler, argues that it’s easier to create a primitive radio transmitter than to re-engineer John Harrison’s marine chronometer from scratch.
With that kind of challenge at sea, how did the Polynesians ever find all those islands scattered across the Pacific? It’s easy in the nearer reaches, where islands are within sight of each other or getting blown off course by a storm might result in finding another one just over the horizon — but the Hawaiian archipelago and Easter Island are a different matter entirely.
The answer lies not in precision engineering, but in a finely-tuned awareness of the natural world and its patterns. Polynesian navigators used stars as navigational landmarks, but they also understood things like the movements of ocean swells, the cloud formations that typically appear above islands, the changing color of low-hanging clouds over atolls, the movements of birds, the drift of flotsam — and how those things could signal the presence of nearby land. They also knew how the prevailing winds and currents moved in different regions, and could set out on a looping course that took advantage of those forces to bring them back to their starting point, in the process sweeping a huge swath of the ocean for new islands to settle.
But once those were found, you didn’t want to have to search for them all over again to return. The biggest aid in navigation, on land or at sea, was a map: a diagram of the terrain and its characteristic features that could allow you to identify your position and plot your own course to your destination, without needing someone else to tell you where to go. But what we think of as a map today and what they looked like in the past are not the same thing . . . which is why we’ll turn to that subject next week.