The most important application of astronomy in Polynesian societies was oceanic navigation. Polynesian navigators regularly traversed from one small island to another across hundreds of miles of open sea. To accomplish these feats of seafaring, they relied on an intimate knowledge of the night sky.

Transcript

Good evening, and welcome to the Song of Urania, a podcast about the history of astronomy from antiquity to the present with new episodes every full moon. My name is Joe Antognini.

Last month we looked at a number of the astronomical practices among the Aboriginal Australians. In this episode we will remain in Oceania but we will put out farther to sea and look at the astronomical practices of Polynesia, along with Micronesia and Melanesia.

In some ways the people of Polynesia are the mirror image of the Aboriginal Australians. The Aboriginal Australians largely inhabited a single landmass, the Australian continent, with the important exceptions of Tasmania and a number of islands in the north. But in this one landmass there was a huge diversity of languages and cultures. I mentioned in the last episode that there were some 30 separate language families, which is really quite incredible when you consider that in Eurasia, a single language family, the Indo-European language family, stretches from India all the way through Iran, to Armenia, Russia, Poland, Greece, Germany, France, Spain and Portugal, with many other countries besides. The huge diversity of languages in Australia came about from the relative isolation of Aboriginal Australians for tens of thousands of years. And in this time the Aboriginal Australians learned how to traverse large distances across inhospitable terrain.

By contrast the Polynesians spread out over a far larger area, around 6% of the Earth’s surface. But all share the same language family. One archaeoastronomer, William Liller, visited Easter Island once and was surprised to find that an elder reported that he was able to understand the Samoans he had encountered without any need for a translator. And whereas the Aboriginal Australians had inhabited their continent for tens of thousands of years, parts of Polynesia were inhabited relatively recently. Hawaii was settled around a millennium ago or possibly a little earlier and the Maori first settled in New Zealand less than 700 years ago. Like the Aboriginal Australians, the Polynesians had to learn how to traverse vast distances across an inhospitable environment, but in their case they had to learn how to travel over open sea rather than land.

Well, before we get into the astronomy we will, as always, start with the geography. With the Polynesians, the connection between their astronomy and the geography is straightforward. Since the region consists of some 1000 islands scattered across a vast area of the Pacific Ocean, Polynesian culture naturally centered around seafaring, and Polynesian astronomy was developed largely in service of their seafaring needs.

Now, I’ve been saying Polynesia for simplicity, but actually much of what I’ll be talking about in this episode also applies to Micronesia and Melanesia. The fact that these regions all have different names suggests that there are hard and fast boundaries between them, but in reality it’s more of a convenient way to subdivide the region rather than a set of mutually exclusive cultures. Cultural practices between the three regions all bleed into each other, and if you were traveling from one island to the next you’d be hard pressed to pinpoint where exactly Micronesia ended and Polynesia began.

Well, the whole region more or less owes its existence to the so called Ring of Fire. Almost the entire Pacific ocean sits on top of a single gigantic continental plate, called, appropriately enough, the Pacific Plate. All around its edges, its interactions with neighboring tectonic plates causes a great deal of geological activity. Where I sit recording this podcast in Los Angeles, California, the Pacific Plate to my west is slowly moving southeast with respect to the North American plate that I am on top of, forming the San Andreas fault. This fault line has caused no shortage of big earthquakes for us Californians and, in fact we are overdue for the big one now. Hopefully it comes after I finish with this series so that it doesn’t interrupt the podcast schedule for all of you listeners. The Pacific plate continues up northwest along the North American coast, and then curves around under Alaska. Its thanks to its actions up there that you have the Aleutian islands, that chain of volcanically active islands in the southwest of Alaska. Then the Pacific plate moves down, butting up against Japan, where its motion is responsible for the major earthquakes that that country sees. Then it moves south right up to New Guinea, where it starts to move southeast. Then it swings southward, passing through New Zealand. To the west is the Australian plate, and at many points, the Pacific plate is subducting under the Australian plate, and the interaction between these two tectonic plates has created mountain ranges. But, because the Pacific plate is so low, being under a huge amount of water, what we actually see is not an impressive mountain range, but an archipelago of islands.

The main exception to this is the island chain of Hawaii, which sits pretty well near the center of the Pacific plate. This island chain was created by what is called a “hotspot” in geology, a place where for whatever reason the mantle happens to rise up through the crust to create a volcano. In fact, Hawaii gets its characteristic arc of islands to the northwest due to the fact that the Pacific plate is moving to the northwest over this hotspot. Over the course of millions of years, magma would emerge through the hotspot to form a volcanic island. But over time, tectonic motion would move this island to the northwest so that it wasn’t over the hotspot anymore. Then the activity of the hotspot would create a new volcanic island and the process would continue again. Over time the older islands to the northwest would erode away, and so the chain has a characteristic pattern where the largest island is the one that is currently over the hotspot and contains an active volcano, and then the islands get smaller and less volcanically active as you move to the northwest. The shape of the island chain essentially traces the motion of the Pacific plate over the last 30 million years or so.

Well, following the border of the Pacific plate down south along its western edge, we run into the area known as Micronesia. Micronesia extends just to the east of the Philippines and to the north of New Guinea, and as its name implies, it consists mostly of small islands. There are four main archipelagos in Micronesia: the Caroline Islands, which extend east-west, the Mariana islands, which extend north-south, the Marshall islands in the northeast, and the Gilbert Islands in the southeast. To the south of Micronesia is Melanesia, which extends from New Guinea to the south and east. Here the main archipelagos are the Solomon islands which extend south and east of New Guinea, New Caledonia, in the south, and Fiji in the east. Melanesia gets its name from the fact that 19th century anthropologists perceived that the peoples in Melanesia had darker skin than in Micronesia or Polynesia. But in both Micronesia and Melanesia there is quite a diversity of ethnicities and languages. Polynesia, by contrast, is relatively homogeneous ethnically and linguistically, which is due to the fact that the islands of Polynesia were settled much more recently. Polynesia is traditionally bounded by the so called Polynesian triangle which stretches from New Zealand in the southwest, up to Hawaii in the north, and Easter Island far in the east. In addition to these three corners, one of the most important archipelagos was Tonga, which sits at the western border of Polynesia with Melanesia. To the north of Tonga closer to the point where Polynesia, Melanesia, and Micronesia meet is Samoa. And near the center of the Polynesian triangle are the Cook Islands and the Society Islands, of which Tahiti is the most important. Now, we generally speak of the Polynesian triangle because all of the islands of Polynesia fall within this triangle between Hawaii, Easter Island, and New Zealand when you plot them on a map. But the Polynesians themselves tended to conceive of the shape of their world as more of an octopus, with the head of the octopus centered near Tahiti, and its various tentacles stretching out through the ocean to other archipelagos along the sea routes they would take.

Now, it’s important at this point to emphasize just how vastly separated the islands in Polynesia are. As I mentioned earlier, the Polynesian triangle makes up around 6% of the Earth’s surface, but less than 0.2% of this area is land, and the majority of that is New Zealand alone. Out in eastern Polynesia, the typical distance between islands is on the order of hundreds of miles. This meant that if you were going to travel from one island to another, you really had to know what you were doing and where you were going. On the open sea, you can see out to a distance of about three miles or so. If the island you’re aiming towards has tall palm trees you can see it a little ways further than that, maybe about ten miles away or so. In fact, a handy rule of thumb is that a rough estimate of the distance to the horizon in miles is the square root of the height of the observer in feet. If you want to be somewhat more accurate, bump this number up by 20%. So, for a person standing on a boat, maybe about six feet above water, they will be able to see out to a bit more than the square root of six miles, which works out to be just under three miles. If the island has a palm tree of around 60 to 70 feet, then it will be visible at a distance of square root of 64, or 8 miles, bumped up by 20%, gives you nearly 10 miles.

At any rate, if you’re making a voyage to an island some 300 miles away, but you can only see it if you get within 10 miles of it, in good conditions, you can see how this is a very tricky navigational problem. If you’re off in your bearings a little bit and drift just 10° away from where you were aiming, you’ll miss the island completely. If you keep going, there’s no telling where you might end up. The next landmass might be several thousand miles away. This, of course, raises the important question of how people ended up on these islands at all in the first place. An early hypothesis was that these islands were essentially discovered accidentally through random drifts. Some hapless voyagers missed their targets, or got blown off course, drifted around aimlessly at sea and eventually they happened to get lucky and drift to some remote island. Now, it can’t be ruled out that maybe a couple of islands were discovered this way. But there’s really no way that the furthest flung Polynesian islands like Hawaii or Easter Island could have been discovered in this manner. The main problem is that the prevailing currents in the Pacific Ocean go east to west. So if you get blown off course and start to randomly drift around, you will end up in Micronesia, and eventually hit the Asian landmass. You would never get to Hawaii or Easter Island that way. In fact, during the 1600s when the Spanish were beginning to colonize the Philippines there are records of Polynesian sailors drifting ashore. One missionary named Father Serrano noted that he had spent 37 years in the Philippines and in that time he saw eight Polynesian crews drift ashore. But he was astonished to find that in the following year, 1664, he saw 30 ships drift ashore, presumably because that year was exceptionally stormy.

Now, how the most distant islands in Polynesia were first discovered remains an open question, but the overall timeline of settlement across Micronesia, Melanesia, and Polynesia is by this point fairly well established. The western parts of Micronesia and Melanesia were first settled very early on, at least 50,000 years ago, in the same population expansion that settled Australia. These first groups were ethnically distinct from the later Polynesians and remained hunter gatherers. They never developed many of the necessary technologies to make the long voyages over the open sea that would allow the settlement of distant lands: pottery, animal domestication, sophisticated shipbuilding, to name a few. But sometime during the fourth millennium BC, these technologies emerged in Taiwan. It seems that these early seafarers got their practice traversing the Taiwan Strait to the Chinese mainland, which is a distance of about 80 miles. These early inhabitants of Taiwan developed the so called Dapenkeng cultural package, which included domesticated pigs and chickens and a tool called a bark beater. In the absence of sheep, cotton, or other sources of fiber, the bark beater was used to pound the bark of a native tree into clothing and rope. Another important development here was a tool called an adze which was used to hollow out tree trunks to make canoes or make flat planks of wood. A few centuries later, this cultural package made its way south to the Philippines and by about 2000 BC it had gotten to Indonesia. Over the next millennium the tools and techniques needed for long ocean voyages became highly refined and the Austronesian people began to expand across Micronesia and Melanesia, in many cases displacing the earlier inhabitants.

Now, at this point it’s worth pausing to talk a little bit about the kinds of boats that these peoples were using as they began their expansion across Oceania. The earliest kind of boat that appears is called a dugout canoe. It’s a simple thing to build, at least in principle, even if it’s maybe somewhat tedious. You take a large tree trunk, lie it on the ground, chop off the top, and hollow out the insides. Then you taper the ends to make it more hydrodynamic. This works, but it’s a bit precarious even in relatively calm inland waterways like lakes or streams. If you get just the slightest bit off balance, the whole thing is liable to roll over and capsize. Because of this, dugout canoes were never suitable for navigating on the open ocean. Eventually, coastal peoples hit upon a solution to this problem called the outrigger. The idea is that you take two logs and fasten them a few yards out on either side of your canoe. This makes the boat far more stable. If it starts to roll in one direction, the outrigger in that direction will start to submerge, and the buoyancy force will keep it from sinking too far, and the canoe won’t capsize. The development of double outrigger canoes is what made it possible for the Austronesian people of Taiwan to travel to mainland China and later south to the Philippines and beyond.

But the original Polynesians who made the much longer voyages to reach eastern Polynesia used a different style of boat called a catamaran. Whether the catamaran evolved from the double outrigger boats or evolved separately is still a matter of debate, but the principle is similar, it just solves the stability problem in a slightly different way. Instead of lashing two outriggers to either side of the canoe, a catamaran just takes two identical canoes and lashes them together, usually separated by a few yards. This has the same effect of greatly increasing the stability of the boat over a single hulled canoe, and these boats are stable enough to sail across the open ocean. One of the advantages that the catamaran style had over the double outrigger was just that there was a lot more space in the boat, so you could carry more people and supplies. Obviously a boat that consists of two canoes instead of one has twice as much space in the canoes, but on top of this, the lashing between the two canoes was done in such a way that there was a flat platform between the two, so this could carry even more crew. Oftentimes this platform had a little hut built on it to protect against the elements.

Now, the crafts that the Polynesians used to travel to remote islands on the Pacific are usually referred to as canoes, but that nomenclature does them something of a disservice. When you hear the word “canoe,” you think of a little wooden boat that seats a couple of people who paddle out onto a lake or something. But the Polynesian catamarans were in an entirely different class. These boats were typically around 50 to 75 feet in length and supported a crew of 40 to 50 men. The largest boats had crews of 100 men. When Captain Cook, the famed English explorer, first encountered the Polynesians in the 18th century he was astonished to find that they had boats that were larger than his own. The Polynesian catamarans were also powered by sail, not paddled, so they could travel extremely long distances. Polynesian boats were actually very similar to Scandinavian boats prior to the Vikings. According to the adventurer and sailor David Lewis, who did much of the fieldwork to reconstruct Polynesian navigation techniques, the only substantial differences in construction between Norse boats and Polynesian boats was that the Norse boats used leather for their lashings whereas the Polynesians used sennit and that the Polynesian boats were carvel-built whereas the Norse boats were clinker-built. In a carvel built boat, the planks of wood that make up the hull are arranged so that they sit right next to each other and make a smooth surface, which makes for a more hydrodynamic boat. In clinker built boats the planks overlap with each other, which is less hydrodynamic, but sturdier and tends to hold together better in rougher seas. So, at any rate, if you want a description of what a Polynesian boat was like, you could do worse than read the first part of Beowulf.

Well, to get back to the origin of the Polynesian people, around 1500 BC, a distinct culture evolved in Melanesia, called the Lapita culture. This cultural package included all the technology and skills needed to make long sea voyages, including the boats, the navigation techniques, and everything they would have to carry on board to settle a new, uninhabited island, like crops and domesticated animals. It’s at this point where the ancestors of the Polynesians really take off. They start moving eastward across Melanesia and by 1000 BC they’ve reached the western parts of Polynesia. Some of them move north and start to inhabit the easternmost islands of Micronesia by 200 BC. By 500 AD, some of them have moved west past Indonesia, all the way across the Indian Ocean, and have reached Madagascar. By 700 AD, the easternmost islands like Tahiti have been discovered and settled. By around 1000 AD Polynesians had traveled around 2000 miles north to discover and settle Hawaii. And around 1300 AD they had traveled a similar distance southwest to discover and settle New Zealand.

Even though the people in these farther flung islands later became isolated from the archipelagos that they originated from, thanks to this extremely rapid expansion, there simply wasn’t enough time for many cultural and linguistic features to diverge tremendously, so there are large similarities in culture and language all across the islands of Polynesia. As an example, on the island of Tonga, the word for the number one is “taha.” Just to the north in Samoa it is “tasi.” All the way across the Pacific on Easter Island it is “tahi.” And in Hawaii it is “kahi.” Similarly on Tonga the word for “two” is “ua”. In Samoa it is “lua.” On Easter Island it is “rua.” And on Hawaii it is “lua.” On Tonga the word for three is “tolu.” In Samoa it is also “tolu.” On Easter Island it is “toru.” And on Hawaii it is “kolu.” So while the languages were not generally mutually intelligible, which after all is what defines having different languages, it’s also not a surprise that an elder of Easter Island could understand a Samoan with some effort. The similarities between many of these languages might be comparable to the similarities between Portuguese and Spanish.

Well, the initial wave of expansion of Polynesians across the Pacific Ocean was not a one time occurrence. People did not set sail for some distant island and then never return to the place from whence they came. With the exception of the farthest flung islands like Hawaii, New Zealand, and Easter Island, there have always been regular voyages between the various islands throughout Polynesia, Micronesia, and Melanesia. Now, the overall frequency of these voyages waxed and waned with the political conditions, but they never ceased altogether. During certain periods some islands would make war on other islands, and during these times voyaging became more dangerous. A particularly notorious period was between 1200 and 1500 AD when the archipelago of Tonga expanded to conquer much of eastern Micronesia and Melanesia. Times of war were always a precarious time for seafarers because it was common practice for islanders to kill anyone who showed up on their shores on sight. For the more distant islands like Hawaii and New Zealand, it’s believed that after their initial settlement there was a period during which there were regular journeys between these new lands and their original home in Tahiti, though by the time of European contact in the 18th century these extremely long journeys had long since died out.

Nevertheless, thanks to this deep culture of frequent voyaging between distant islands across the open sea, the Polynesians developed highly refined navigation techniques. Unfortunately, in understanding them, here we are in a similar situation as we were with Aboriginal Australian astronomy. Prior to European contact, Polynesian culture was illiterate, so navigation techniques were transmitted orally. And furthermore, as with Aboriginal Australian astronomy, this knowledge was considered secret. It was only held by the navigators themselves and they generally did not willingly yield it up to strange foreigners. So many early European interlocutors tended to come away with a rather poor impression of Polynesian navigation techniques. Nevertheless, even if they seemed to to play dumb as to how they knew where to steer their ships, in practice their ability to get to one island from another was formidable. There is a rather remarkable story of a navigator named Bakapu. During the 19th century and early 20th century the South Pacific suffered from the rampant practice of what was called “blackbirding.” European ships would arrive at some island and the crew would kidnap a few dozen locals, and transport them to some distant land where they would be pressed into slavery. Bakapu was unfortunately one such victim of blackbirding and was transported from his home in the Reef Islands in Melanesia to Fiji, over a thousand miles away. But after some period of time on Fiji, he and a companion were able to escape their captors. During their escape they found a small boat. They stole the boat, and Bakapu then managed to sail the 1000 miles right back to his home.

Well, one important early source we have for Polynesian navigation techniques was the Tahitian navigator Tupaia, who joined James Cook on his first expedition in the south Pacific. Tupaia had been born into a high station on the island of Ra’iatea and in addition to becoming a navigator was a priest as well. But when he was in his late 30s, his island was invaded by warriors from the island of Bora Bora to the west, and wiped out the ruling clan. Tupaia managed to escape and fled to Tahiti. A few years later, when Captain Cook showed up at the island, Tupaia agreed to join in the expedition and provide help with navigation. Having been dispossessed of his status he seems to have been somewhat more willing to divulge Polynesian navigational techniques than others.

Well, in the late 1800s and early 1900s the region was colonized by a number of outside powers: Germany, the United States, Japan, France, and Britain among others. Many of the colonial powers prohibited unregulated travel between islands. These rules were not observed by the native Polynesians very strictly of course, but it did have the effect of reducing the frequency and length of voyages. By the middle of the 20th century, the proliferation of instrumental navigation started to cause traditional navigation techniques to fall out of use. One of the most important sources we have for Polynesian navigation techniques came from the sailor David Lewis, who did fieldwork in the 1960s and 70s to preserve what remained of Polynesian navigation. He spent several years voyaging with elder navigators all over Micronesia, Melanesia, and Polynesia, letting the navigators work their craft, and asking them for detailed explanations of what they were doing and why. Although this research saved many of the most important techniques from being lost to history, it’s almost certainly the case that two centuries ago the best navigators were making use of additional techniques that have since been forgotten. There is, for example, a story that during the 1820s there was a great flotilla of Tongan canoes returning from a trip to Samoa carrying the Tongan king. The flotilla was being led by the High Navigator, a man named Akau’ola. But during the trip Akau’ola became lost. He had expected to have seen Tonga by now, but hadn’t, and now wasn’t quite sure where he was. Aboard one of the ships in this flotilla was another navigator, a very old blind man named Kaho Mo Vailahi. When Akau’ola confessed that he was lost, the blind navigator dipped his hand into the sea and tasted the water. He then asked his son where a few stars were on the sky, and, given that information, he pointed the direction that they should go. And, sure enough, the flotilla arrived at Tonga the following day.

Well, I have been speaking at some length about Polynesian navigation, but this podcast at least claims to be a history of astronomy. But the truth is, when it comes to Polynesia, there’s really no separating astronomy from navigation. In general, throughout Polynesia, there’s no word for an astronomer, someone who specializes in studying the heavens. But, of course, that’s not to say that no one in Polynesian societies had this expertise. If you wanted to speak to someone who knew the stars, you would ask to speak to a navigator. The exception that proves the rule is on New Zealand, where the Maori did have a word for an astronomer, but here oceanic navigation was not nearly as foundational to the culture.

Polynesian navigators used a wide variety of techniques to orient themselves at sea, but the sky was by far the most important. Ships would generally sail both day and night, but navigation during the night was considered far easier and more reliable. Journeys from one island to another would be described in terms of a set of stars used to guide the ship. Although the stars rise at different times of night over the course of the year, at a given latitude, whenever they rise, they always rise at the same azimuth. So when a star is low on the horizon, it’s a reliable indicator of a particular direction. The use of the stars to navigate was recorded very early on by European visitors. One, named Ignacio Andia y Varela wrote in 1774,

When the night is a clear one they steer by the stars; and this is the easiest navigation for them because these being many [in number], not only do they note by them the bearings on which the several islands with which they are in touch lie, but also the harbours in them, so that they make straight for the entrance by following the rhumb of the particular star that rises or sets over it; and they hit it off with as much precision as the most expert navigator of civilised nations could achieve.

Now, this technique was not quite as simple as just orienting the boat towards a star on the horizon. There is a wrinkle, which is that the stars do not remain on the horizon for long. If it’s on the eastern horizon it will inexorably rise higher in the sky, and if it’s on the western horizon it will soon sink. And to make matters worse, at higher latitudes, when the stars do rise or set, they don’t do so vertically. They rise or set obliquely, so its azimuth changes as it sets, and this can be quite a lot due south when you’re in the southern hemisphere. So Polynesian navigators had to develop an intuition for just how high a star could rise before it was no longer a good indicator of the bearing. For east-west navigation near the equator, a star could rise some 45° and still be a good indicator of the direction. But for more north-south travel at higher latitudes, you might need to switch stars after it rose only 15°. Typically, though, a star would be good for one to two hours, so you would only need between six and twelve stars throughout the night.

Now it’s important to mention that a course between two islands would be described by a series of stars. But these were not the only stars actually used for navigation. The stars described in the route were just a shorthand. A savvy navigator would know that for each star in the path, there were a dozen other stars at equal declination and which would provide the same bearing. Another wrinkle here is that the stars themselves might not be exactly the right direction to navigate. Even if the steering star was, say, Canopus, the navigator might just know from experience that on this journey you don’t sail straight towards Canopus, but instead aim a hair to the side, putting the star above a particular feature on the boat.

To complicate matters even further, a navigator would have to account for ocean currents. The water in the open sea is in general not stationary. There are large scale movements of the water. But because all of the water is moving together, it is very hard to detect this motion. In the south Pacific these generally run east to west. So you might be sitting, apparently perfectly still on the water in a perfectly still ocean, but without realizing it, you are actually drifting west at a knot or two. And if you don’t account for this, you can end up very far off from where you intended to go. Now, fortunately for the navigators, the currents are relatively regular. There is day-to-day variation and this might cause you to end up 20 or 30 miles away from where you expected to go, but the day-to-day variation tends to average out, so for long voyages you tend to just be carried away by the average motion of the current. But the genius of using horizon stars is that they can account for the average effect of the currents. The horizon star would not necessarily be the compass direction that the island actually was. It would be the direction you would have to target after accounting for the effect of the current. The impact of the currents can be seen by the fact that stars used to navigate from one island to another generally weren’t on the opposite side of the sky as stars used to make the return journey. If, for example, the prevailing current was east to west, as it is in much of the south Pacific, and you wanted to make a journey to an island due north, you would have to orient your boat a bit east of north. But on the return journey, you wouldn’t just head in the opposite direction. If you did that, you’d end up way too far west of home. You’d instead want to orient your boat again a bit east, this time east of south. Furthermore, if they made a journey to an intermediate island, navigators would keep track of how far off they were from where they expected. If they were very far off, then the currents were unusually strong, and they might use a different set of stars to steer by. For navigators closer to the equator they would also keep track of where the currents switched. A bit north of the equator there is a countercurrent, where the prevailing current switches from being east-to-west to going west-to-east. But where the currents switch, there are doldrums, where there is little current at all. This region tends to accumulate debris and flotsam. So by keeping an eye out for these signs, an experienced navigator could detect when he was crossing a region where the currents were changing.

Well, the principal set of horizon stars used to navigate constituted the so called “sidereal compass.” The specific stars used in the sidereal compass varied from archipelago to archipelago since the azimuths of the stars on the horizon would vary with latitude. But the principle was similar all across Polynesia. A standard compass in the West is defined by the cardinal points, north, east, south, and west. Then these get subdivided into the so-called “ordinal directions” of northeast, southeast, southwest, and northwest. Then there are further subdivisions like west-northwest, north-northwest, north-northeast, and so on. And the finest set of subdivisions goes one step further to get bearings like north-by-east, or southwest-by-west. All together, these directions form the points of the compass, a 32-wind compass specifically. This set of bearings gives you 32 separate directions with a precision of 11 1/4° when specifying a direction.

The sidereal compass used by the Polynesian navigators is similar, but instead of specifying these cardinal directions and the various derivatives, you specify a star and whether it is rising or setting. Towards the north you have Polaris, of course, and then north-northeast roughly maps to the rising of Beta Ursae Minoris. And the various stars at rising map out different points that are generally eastward. The corresponding stars at setting then map out the mirror image in the westward direction. So Beta Ursae Minoris is approximately north-northwest. So, to specify an island that was north-northwest, you would say that its star was Beta Ursae Minoris at setting. Likewise to indicate the direction of an island that is to the southwest, you’d say that its star is Lambda Scorpii at setting. In the Carolinian archipelago, the sidereal compass had seventeen unique stars or asterisms. Polaris, of course, pointed due north, and for due south they used the Southern Cross when it was vertical in the sky. The other fifteen stars in the sidereal compass rise and set and so specify another 30 directions. So the Carolinian sidereal compass has 32 points, just like the standard western compass. But there is a difference. If you plot the location of these stars against the directions on a compass, you’ll find that they’re spread pretty far apart in the north and south directions, and they’re clustered together pretty closely in the east-west directions. So, while the sidereal compass on average has the same resolution of 11 1/4° as the standard western compass points, towards north and south this resolution is quite a bit lower, and towards the east and west it is quite a bit higher. The reason for this is that the Carolinian islands are generally oriented east and west. Most of the travel that Carolinian navigators did was in the east-west direction, so it was helpful for them to have more specificity in those directions.

Well, navigating by the stars of the sidereal compass of course required a strong knowledge of the night sky. But being able to reliably make journeys using the sidereal compass required an even more detailed memory of the night sky than it might first seem. Ideally the horizon would be clear and you would be able to just point your ship to the appropriate star. But conditions aren’t always ideal. Oftentimes there are clouds, particularly on the horizon. So a navigator would have to be able to look at the parts of the sky that aren’t covered by clouds and use the stars that were visible to him to figure out the position of the star he was aiming towards. In quite poor conditions, a good navigator would be able to keep his way even if only a small patch of sky with a handful of visible stars opened up every now and again.

Now, of course, this doesn’t help you if it is completely overcast for long periods of time. But fortunately this isn’t terribly common in the south Pacific. David Lewis estimated from his travels that it was completely overcast for an entire night at most about 5% of the time. But these conditions were also seasonal and could be avoided by making journeys during certain times of the year.

Well the other limitation of the sidereal compass is that it only works half the time. You can navigate by the stars all you want during the night, but once the Sun comes up you’re out of luck. Navigation during the day was more difficult and less accurate than nighttime navigation, but still possible. In the early morning as the Sun rose, a navigator would make a note of where the Sun was rising on the horizon with respect to the star he was aiming for. Once the Sun rose and washed out the navigation star, he would try to keep the Sun in the same position with respect to his boat. This would be nearly as accurate steering towards the navigation star at least for an hour or so after sunrise. As the Sun rises higher in the sky, the navigator would have to keep in his head the path that the Sun was following in the sky and how that related to his bearing.

Because Sun tracking was necessarily less accurate, navigators would supplement this technique with other signals. The most important of these was orientation by ocean swells. If you imagine yourself out on a boat in the open ocean you’ll probably picture waves lapping up against the boat. But these waves come in two categories. There are surface waves, which are more or less random, and swells. Swells are much lower frequency waves, with a period of, say, 10 to 30 seconds and a wavelength of dozens to hundreds of meters. If you’ve ever been out on a deep sea boat, it’s the ocean swells that cause the very slow up-and-down motion of the boat and which tend to make people feel seasick. Now, generally speaking, the source of waves is from the wind. As wind blows across the surface of the water, it imparts some momentum to the water, starting a wave. In fact this is the principal mechanism that heat gets transferred from the atmosphere into the ocean. Now, locally, the winds can be kind of random. They blow this way and that and so locally there are waves going every which way. But if you zoom out, the winds on average start to be more consistent. The average motion of these trade winds adds up, and the waves they produce reinforce each other, and produce ocean swells. Because the swells originate from these relatively stable trade wind patterns, the ocean swell patterns are relatively stable as well. They tend to come from the same direction with a particular period and amplitude. A savvy navigator can observe the direction that the swells are coming from to determine his orientation.

Now, in practice this is a lot harder than it might sound in the abstract. The swells are very slow, so this is not something that you observe with your eyes. Across Micronesia and Polynesia, navigators describe swells as something that’s felt, not seen. When a boy is training to become a navigator, his mentors will have him get out of the boat and float out in the ocean so that he can feel the swells periodically move him up and down. On the boat, the swell will rock the boat differently depending on the angle at which it impinges the boat, and from these differences in rocking the navigator can estimate his bearing. But, to make this even more difficult, there isn’t just one swell at a time. There are typically at least three separate swells and sometimes as many as five in a location, all arriving from different directions. But the different swells have different periods and amplitudes. In some cases a navigator will lie down flat in the boat and close his eyes to feel the various swells hitting the boat. With time he could sort them all out and identify them by their period, amplitude, and direction. There are also reports that some navigators found that they could best sense the direction of the swells by the feeling it caused in their testicles. At any rate, between a combination of tracking the Sun and feeling the ocean swells, a navigator could roughly maintain his bearing during the daylight hours as well.

Well, with the stars of the sidereal compass and the various techniques for daylight navigation, a navigator had a variety of tools to ensure that he was heading in the right direction. But this is only half of the equation in wayfinding. You have to go in the right direction, of course, but you also need to go the right distance. Generally for this purpose a navigator would use dead reckoning. They would know how many days a particular journey would take under typical conditions, and then they’d estimate how they were comparing against this typical journey. If they felt they were traveling more slowly than usual, they’d assume that they were behind by some amount, and if the winds were in their favor, they’d estimate that they were ahead. Now, dead reckoning can be notoriously unreliable, so navigators had to avail themselves of as many clues as they could to assess their progress through the waters. After all, when you’re on the open sea, there are very few clues as to where you are. The ocean looks the same in every direction and no matter how much or little you travel the ocean still pretty much looks the same.

So one of the most important techniques that navigators would use to track their progress along a journey was purely mental and was called the system of “etaks”. An etak is an intermediate reference island that a navigator would track along the course of a journey. A typical journey would be broken into segments of around 60 to 100 miles in length. Each segment would be governed by an etak. The idea was that the navigator would have a mental map in his head of all the islands in the region. As he was travelling from one island to another, he would know that as he made this journey, he would pass by some third island off in the distance, say, to his left hand side. This island wouldn’t actually be visible to him, but he knew that it was there. When he started out in his journey, he would mentally know the bearing of his destination and the bearing of the reference island, the etak. The destination would be in the direction of some star on the horizon, and the etak would be in the direction of another star on the horizon. As he travelled towards his destination, his destination would remain under its same star, at least until it rose too high in the sky and had to be switched out with some other star. But as he passed by the etak, it would move through different stars. So, based on his intuition as to how fast the boat was moving, he would mentally picture the etak being in the direction of a succession of stars along the horizon. Finally, he knew what star the etak would appear under at his destination, so when he pictured the etak being under that star, he would know that he had traveled approximately the right distance, and that the destination island should be nearby. Now, in this process the etak was never visible to him. In fact, in some cases the etak is not visible at all. Some etaks were reefs and were entirely underwater. But the ability to be able to mentally track where the origin, destination, and etak was over the course of a journey, helped the navigator to mentally triangulate his position. One of the fundamental skills that was taught to any boy learning to navigate was to be able to be on a boat and immediately point in the direction of any given island or landmark.

This system was also used to help with tacking. Now, probably a lot of us have an intuition that the way a sailboat works is you put up a sail, and then the wind blows on the sail and pushes your boat forward along with the wind. Then maybe you use the rudder to steer a little bit this way and that. But what if you want to go in the direction that the wind is blowing? Naively you would think that this should not be possible. You’d just have to wait until the winds change. But the sail of a sailboat can actually work rather like the wing of an airplane. The sail can be angled nearly parallel to the wind and the sail acts as an airfoil. The lift on this airfoil propels the boat forward. One of the counter-intuitive consequences of this is that this makes it possible to sail upwind with a technique called tacking. The idea is that you can use the wind to sail in a direction that is, say, 45° away from upwind. So you do this for a little ways and then you turn around and do the same thing going back, again going about 45° away from upwind. In this way you zigzag back and forth, each time making a little progress in the upwind direction. When Polynesian navigators needed to tack, they would visualize the island they were headed towards under a particular star on the horizon. Then they would move nearly perpendicular to the island until the island was visualized to be under a second star. Then they’d turn around and go back until the island was visualized to be under a third star that was equidistant from the original star as the second star, but on the opposite side. Then they’d continue tacking between these two stars until the points converged and they arrived at their destination.

Well, for shorter or moderate length voyages these techniques kinds of techniques were largely sufficient for navigation. In fact, for voyages of a couple of days, navigators were so confident in their abilities that they would sometimes decide to make such a voyage on the spur of the moment while drunk on palm wine in order to by some cigarettes from a store on another island. But longer voyages required some additional techniques. Longer voyages would almost always result in a non-negligible change in latitude, so tracking their latitude was an important part of these kinds of journeys. Now, in Western astronomy, typically when we want to estimate our latitude from the stars, we do so by measuring the elevation of Polaris, the north star. This wasn’t commonly done in Polynesian navigation, though. One issue is that it only works in the northern hemisphere, and much of Polynesia is in the southern hemisphere. But even navigators who lived in archipelagos in the northern hemisphere still tended not to use the elevation of Polaris to estimate their latitude. In David Lewis’s interviews with navigators, they would say that they knew that Polaris’s elevation changed at different islands, but they couldn’t say by how much it changed, and that it wasn’t something that they paid much attention to. It’s possible that the motion of the boat made it too difficult to get a good estimate of the star’s elevation above the horizon to within a degree or two, and a two degree error in latitude works out to be around 120 miles.

Instead, navigators would use zenith stars. They would know that each island had a particular zenith star. If that star did not pass overhead, you knew you were not near the island. If it did pass overhead, you were probably near the island. Although Polynesian navigators didn’t think in terms of latitude, in Western terms, if the zenith star passed overhead, you knew you were at least at the right latitude. So, for instance, the zenith star of the island Tikopia was Rigel. Now, there’s actually a problem here, which is that the zenith stars do not generally pass directly overhead of their corresponding islands. In the case of Tikopia, Rigel actually passes about 4° south from the zenith. One hypothesis here is that probably the zenith star was observed by lying flat on the boat near the mast and looking straight up, using the mast as a guide. The mast will wobble around due to the motion of the boat, but it will trace some small ellipse on the sky, and by observing it for a little bit, it’s not too hard to identify the center of this ellipse. But due to the trade winds, no matter which direction you were approaching the island from, your mast would be inclined off of vertical towards south by 3 to 4 degrees. So although Rigel wasn’t strictly at the zenith, it would appear to be at the zenith if you were using your mast as a reference.

Well, there’s another very interesting technique that was developed for estimating latitude, although there’s no evidence as to whether Polynesian navigators historically used it. This technique came about in the 1970s in preparation for a voyage from Hawaii to Tahiti of the Hokule’a, which was a recreation of a traditional Polynesian catamaran. The navigator for this voyage was a Hawaiian man named Nainoa Thompson, and to practice for the voyage he did hundreds of dry runs in a planetarium until he developed an intimate knowledge of the sky along every step of the journey. In an earlier voyage at sea, he had noticed that when he was near Tahiti, Vega and Rigel would rise at the same time. At other latitudes they would rise at separate times, either Vega before Rigel, or Rigel before Vega. In general, two stars will only rise simultaneously at a single latitude. If you see the two stars rise together, this is a very easy to observe measure of your latitude, even if you’re on a boat that’s rocking all about in the sea. So during his dry runs in the planetarium, he identified multiple pairs of these stars that rose simultaneously at particular latitudes. Then by watching out for these stars and tracking whether one rose before the other, at the same time, or after each other, he was able to track his latitude extremely precisely.

Well, even with this smorgasbord of techniques to estimate your position, if your journey is of moderate length, it is still hard to come within eyesight of your target. As I mentioned earlier, this would require you to end up within about 10 miles of your target. For a journey of 300 miles, this means that you could drift away from your target by no more than two degrees or so. So navigators used other techniques to tell if land was close, even if it wasn’t visible. I won’t go into these techniques in too much detail since they weren’t astronomical in nature, but one of the most important of these was to observe birds. Now, you had to know what you were doing to use birds to determine whether land is near and if so, how far away it was. Not all birds are useful for this purpose. Some birds are pelagic and take long, migratory paths over the ocean, periodically stopping to hunt fish. You can be way out in the middle of the Pacific Ocean and still see these birds, so their presence doesn’t really tell you anything. But other bird species are land based, and if you see them you can assume that you’re likely to be near land. How far away you are from land varies with the species. Some will venture out only 10 miles or so, others might go as far as 30 miles. But again, you have to be careful when using them to figure out the direction of the land. When you see them flying overhead, they are unlikely to be indicative of anything. During the daytime they hunt out at sea and will fly around more or less randomly. So you have to wait until dusk when they fly back to land to determine which direction the island is in.

Another important technique is again to use the ocean swells. Out in the open sea, the swells are basically plane waves. But if there is an island present, it will affect the wave dynamics. There will be reflection off of the island back in the direction that the swells came from. And on the other side of the island, the waves will be refracted. The effect of this is that an observant navigator can feel the changes in the swells due to the reflection and refraction of the island, and because the reflected and refracted waves feel different, the navigator is usually able to tell which side of the island he is on with respect to the swells.

The last category of land signs are atmospheric. Land will reflect light from the sun back up into the atmosphere differently from the ocean. The effect of this is that a careful observer can perceive a subtle change in the sky over the island. On completely clear days this is described as the sky being lighter, and on totally overcast days it tends to darken the clouds above the island. On days where there are patchy clouds moving across the sky, navigators describe the clouds as lingering over islands longer than they otherwise would.

Now, it’s important to note that none of these signs was instantaneous. Even a trained navigator would have to spend at least half an hour carefully studying his surroundings in order to assess if land was near and in a particular direction. But if he was able to this he could generally detect land up to 30 miles out, which effectively tripled the allowable error in bearing.

For the true odysseys like the 2000 miles between Hawaii and Tahiti, navigators would generally also aim upcurrent of their target. So if you were sailing from Tahiti to Hawaii, you would aim your boat so that you would end up a ways east of Hawaii. Then, when you arrived at the right latitude, they would know that the islands were to the west of them. Then they could turn and sail west until they spotted land. This technique avoided the risk that they accidentally ended up on the wrong side of the archipelago and ended up sailing around aimlessly in the middle of the Pacific.

Well, in practical terms, astronomy in Polynesian society was by far most important for navigation, and so I’ve spent the bulk of this episode talking about how they used astronomy to solve the very challenging navigational problems they had. But, of course, like every society they also had creation stories. So I thought I would end this episode with a brief overview of the cosmogony and cosmology of the Hawaiians. Like other preliterate societies, ideas about the origin and structure of the universe were passed down orally. The most important source we have is a 2000 line poetic chant called the Kumulipo, which literally translates to “beginning in the darkness of night.” The Kumulipo was closely associated with the royal family since, in addition to describing the creation of the universe, it described the genealogy of the royal family. By naming their ancestors back through the generations, from deceased kings still in living memory to epic heroes of distant past, to the gods of the heavens, the poem helped to establish the legitimacy of the king’s rule. Because of this, the poem was not the exclusive reserve of the royal family. It was ritually chanted by priests and other men of high status at certain times of the year.

The beginning of the poem describes the creation of the universe. It goes,

At the time when the earth became hot
At the time when the heavens turned about
At the time when the sun was darkened
To cause the moon to shine
The time of the rise of the Pleiades
The slime, this was the source of the earth
The source of the darkness that made darkness
The source of the night that made night
The intense darkness, the deep darkness
Darkness of the sun, darkness of the night
Nothing but night.
The night gave birth
Born was Kumulipo in the night, a male
Born was Po’ele in the night, a female. \

These two gods, Kumulipo and Po’ele, then continue the creation of the universe during the era of darkness, or “po,” by creating the land and the sea and populating them with animals and fish. Then comes the era of “ao,” or light, which begins with the birth of the god Kane, generally the most important of the Hawaiian deities. After the Kane is born comes the creation of man as the progeny of two other gods.

There are, however, a few other creation stories that are independent of the Kumulipo. In some of these the god Kane is the creator of the universe. During the time when there is nothing but darkness, Kane senses his own existence, and then through a sheer act of will separates himself from the darkness. His sibling gods, Lono and Ku, then sensed his presence and separated themselves from the darkness as well.

In another story, the creation of the universe is due to the gods Wakea and Papahanaumoku, who were husband and wife. Papahanaumoku, often shortened to Papa, created the calabash, a type of gourd. She cut the gourd in half so that it had a top and a bottom. Wakea then threw the top half up and it became the heavens. He then took the bottom of the bowl and used it to create the land and the sea. The meat of the calabash he used to make the sun and the moon, and its seeds became the stars. The name Wakea means zenith or heaven, and so he is associated with the sky, and Papa means foundation, so she became associated as being the goddess of the Earth.

Well the idea that the universe resided within a great gourd was not simply of value as an abstract explanation of the structure of the universe. It was a valuable pedagogical tool as well. When navigators were teaching their sons how to navigate, one of the tools they would use would be the bottom half of a calabash gourd. This was a rounded dome that they could then use to represent the heavens and draw the meridian, celestial equator, ecliptic, tropics of Cancer and Capricorn, and so forth.

Now, although the Polynesians recognized that the sky was different at different islands, they did not independently come up with the idea that the Earth was a sphere. Instead, they had a rather unique cosmography. The idea was that a person standing on an island would appear to himself to be at the center of the world. If he looks off into the distance over the ocean he will see a horizon. But this was just the visible horizon. Beyond the visible horizon was an invisible horizon, which was the wall where the sky meets the Earth. But this wall was permeable. When a voyager arrived from a distant land, he was said to have “broken through” the heavens. Each archipelago, in effect, formed its own universe, bounded by its own horizons, and with its unique stars.

Beyond the overall structure of the universe, many of its features were ascribed to a god named Maui. Maui was a trickster god, so unlike Kane and Wakea, he wasn’t worshipped per se. But his various exploits were an important part of Polynesian mythology. One of these tales tells of how a long time ago, the Sun followed no set path in the sky. The Sun would rise and set whenever and wherever he pleased, and people became too hot and too cold and didn’t know when they should plant and harvest. Another version has it that he did follow a fixed path, but moved far too quickly. When Maui’s mother beat her bark cloth, it could never dry out. Either way, Maui resolved to tame the Sun. In the Hawaiian version, he climbed to the top of the mountain Male-a-ka-la, which means house of the Sun. He then constructed a lasso from his sister’s hair and caught the Sun as he was speeding across the sky. He demanded the Sun slow his pace if he wanted to be free from the lasso, and the Sun agreed. The Sun now rises between two points in the east, a northernmost point and a southernmost point. On Kumukahi, the easternmost point of the archipelago, there are said to be two stone women, one at the northern limit of the Sun, and the other at the southern limit, and the two women push the Sun back and forth between themselves to create the seasons. This site was a place of healing.

Maui is typically depicted with his principal attribute, a magic fishhook. This fishhook had various powers, among which was the ability to fish anything. In one of the stories, Maui was out fishing with his brothers when he cast his fishhook deep into the ocean. He told his brothers that he had caught a very large fish and that they needed to paddle very hard to pull it out of the water. But his hook had actually hooked the ocean floor and as they paddled, they pulled it up to create the Hawaiian islands. In some versions of the story he tells his brothers not to look back as they’re paddling, but at some point one of the brothers looks back, at which point the line snaps. Maui then berates his brother and tells him that if he hadn’t looked back, it would have been an even mightier land. The Maori of New Zealand also have a similar story about Maui creating their islands. Maui’s legendary fishhook was placed into the sky and is now visible as the tail of Scorpius.

Well, this episode is now quite late, so I am going to leave things here for now. In the next episode we’ll cross the Pacific and turn to the astronomy of Mesoamerica. I hope you’ll join me then. Until the next episode, good night, and clear skies.

Additional references

• Lewis, We the Navigators