In 2002, on a pleasant summer day in Maine, a particle physicist named  John Huth was on vacation.

He didn’t have much experience on the water, but rented a kayak on a whim. I was kayaking around the island again and a fog bank started to roll in.

And I realized I didn't have a compass or any way of orienting myself at that point. And there was an open ocean  that was just off to one side. With no map, and unable to  see the shore or the sun, John had to rely on his knowledge of physics to guide him back to shore.

He used clues from the wind and waves to paddle back into the bay, grateful  to be back to shore safely. This simple act of finding his way home sparked a fascination with traditional wayfinding methods. I became rather obsessed getting back to kind of thinking like a physicist… This eventually led him to the  people of the Marshall Islands, who’d documented oceanic wave systems completely unknown to Western science.

Huth’s collaboration with  traditional navigators would lead physicists and navigators alike to understand ocean waves more deeply than ever before. [♪INTRO] Before we get to the Marshall  Islands, I have to backtrack. Because that foggy paddle around the bay wasn’t John’s only memorable kayaking experience. One year after his 2002 kayaking adventure, John took to the waters again,  but this time he noted the wind direction and coastline  shape before setting off.

When the fog unexpectedly  rolled in again, he used the wind as a natural compass  to lead him back to shore. But that wasn’t true for everyone  else on the water that day. And it wasn't until the next  day when I went out paddling where the harbormaster caught  up with me in his boat.

That was when I learned that  basically at the exact same time that I launched my kayaks, only  half a mile down the beach, two young women had launched their kayaks… and they never got back. And I was floored with what I can  only surmise was survivor's guilt. The physics that had saved  him, but not others, wouldn’t leave his mind.

He wanted  to understand the ways that people can navigate using only nature’s cues. It sort of opened up the  world to me, whereas I felt before I was kind of more kind  of isolated in some sense from the world around me. And now  all of a sudden at my scale, my human scale, I was getting  sort of the same signs from nature that I also  sought in particle physics.

Through his obsession with  traditional navigation practices, he learned about wayfinding  traditions in the Pacific Islands. Including the Marshallese people, and the stick charts they use to navigate the oceans. The Marshall Islands are a cluster of tiny islands in the northern part of the Pacific Ocean.

They’re home to the Marshallese people, who arrived in the islands from Southeast Asia roughly 4,000 years ago. We know that’s where they came  from by studying their language – Marshallese is part of the Austronesian  family of languages, spoken by people in places like Malaysia,  Taiwan, the Philippines, and Fiji. Because the islands are so  tiny, the people living there have had to rely on trade  to supply their villages.

But the islands are also very spread  out, making that trade challenging. They’re spread across 750,000 square miles, and they’re pretty flat, so they  can be hard to spot from far away. If you’re trying to get  from one island to the next, you’d be sailing blind  basically until you ran ashore.

That’s why the Marshallese people became incredibly skilled navigators. Their boats carried forty  to fifty people at a time, bringing supplies to trade with  the people on other islands. And the navigators had to be  experts on everything ocean, earning prestigious positions in the community.

Their navigational knowledge was privileged and passed down generationally. Over the centuries, navigators, or ri-metos, built up an understanding of the  ocean so precise that it allowed them to navigate without any guides  other than the stars and the waves. They created charts from palm fronds  tied together with coconut fibers.

Most of them were small, but they  contained a ton of information. A simple chart could represent details about the winds, waves, and currents surrounding an island. And larger charts called rebbelith  could depict the entire archipelago!

Because of how hard it was  to become a master navigator, there aren’t many people who  can read these stick charts. In some cases, only the  maker knew what they meant. Unfortunately, this is a problem that, you know, a lot of the traditional  navigators are gone because they weren't able to pass on their knowledge.

These charts fascinated Huth, and  not just because of their mystery. Part of his interest came from  the nature of water itself, because water waves are incredibly  hard for physicists to study. In general, physicists are good at studying waves, from light to sound to gravitational waves.

And there are a few fundamentals  that are true for almost all waves. For instance, most of the time, the size of a wave doesn’t impact its speed through a medium. But in water, bigger waves also move faster, so they’re already harder to fully  model than waves in other mediums.

And things like water depth or salinity alter how waves move through water. Although we know the equations  that sort of describe them, we can't solve those equations. Those  fluid dynamic equations are kind of notorious to mathematicians of  being at least so far unsolvable.

And we can resort to computer simulations. We can resort to approximations. When you add islands to the equations, the complexity gets dialed up to eleven.

Waves bounce or refract off islands  and shores, and two overlapping waves can either cancel each  other out or amplify them both. The results are complex patterns of wave interference around and between islands. While physicists are still wrapping their heads around these complex water wave rules, Marshallese navigators have a  deep understanding of waves, which is the key to their navigational prowess.

So a team of researchers  partnered with master navigator, Captain Korent Joel, to study the science behind the wave piloting tradition. To map the complicated patterns of ocean swells, researchers deployed buoys to measure the height, frequency, and direction of waves. Joel chose the location of the buoys based on the wave patterns at those points.

Then, Joel showed the researchers that the best way to sense these wave patterns is to feel them. Marshallese wave piloters are  taught to lay in the bottom of their boat with their eyes  closed to better sense the waves. And Joel could detect some swells that were too faint for research buoys to pick up, and used what he felt to reorient their ship towards the shore.

Part of what Joel was picking up on was the different wavelengths coming at their boat. Short, choppy waves don’t tell you  much about the location of land, but long wavelengths are more  reliably reflected off the shore. So identifying the direction of long-wavelength swells can tell you when there’s land ho.

Many of the factors that contribute  to waves, like winds and currents, are really consistent throughout the year as well. So although the exact waves will differ day by day, reliable wave patterns emerge. But you kind of have to know what to look for, which is the challenge, is  knowing what to look for.

And that's what I believe the  Marshall Islanders were able to do. And they encode all this  knowledge in their stick charts. There are two basic kinds of  charts: meddo and mattang; Meddo are fairly similar to traditional maps that we use in the Western world.

Straight lines indicate potential routes for the boats, and shells mark islands. These maps aren’t to scale, and are  more about the vibes and general positioning of islands relative to  each other, not the exact distances. But the second kind of chart,  mattang, is even more interesting.

These charts don’t depict trade  routes or island locations. Instead, they represent stable  patterns formed by swells, winds, and wave interference  around an atoll or an island. Curved stripes indicate the direction of ocean swells as they are deflected by land.

The intersection of curved  stripes indicates confused seas, where waves come from multiple directions at once. So when navigators encounter  these specific wave conditions, they immediately understand  their orientation to land, even if they can’t see it.  It’s like if you’re walking down the street and start to smell pastries. Even if you can’t see the bakery,  you can bet there’s one nearby.

These charts are a powerful  tool for training navigators because they demonstrate  general ocean movements like how waves bounce off of land  or different water depths. But these charts were very fragile, so navigators wouldn’t even bring them along. They memorized them and left them at home!

Because they knew how to recognize  all of the elements marked in the charts just by the  water’s movements and weather. Maybe you can imagine why becoming a master navigator can take decades. After Huth visited the Marshall  Islands and began learning about their navigation culture, he  was interested in comparing stick chart knowledge to physics simulations.

And so what I did was I got a hold  of one of these simulators and you can put in anything you want. And it's usually just some  big, like a round object, but I took a map of the Marshall Islands and I laboriously drew out all of the,  you know, the Marshall Islands, you know, all the atolls  and the places they were in, and then had a big, frayed wind  swell coming in from the east. And then there were all these weird patterns that got created in the simulation.

The data gathered by research  buoys and simulations like the one Huth built  confirmed ocean patterns that Marshallese Navigators had known for centuries. It even revealed wave features that researchers had never known were possible. As far as I'm aware, all of  the salient features of the that I know of in the simulations are reproduced with the one exception of this thing called dilep.

According to the descriptions  of Korent and others, it's this disturbed passage of waves  that connects pairs of islands. Even though it’s common in stick charts, the dilep motif is still hard  for researchers to simulate. So it’s another thing that  Marshallese traditional knowledge has a better handle on than the  high-tech physics experiments.

Some Marshall Islanders, including Captain Joel, hope that the physicists can help their community. Given that wave piloting is  passed down directly from teachers to their students and  without a written curriculum, some knowledge can be lost or  inconsistent between teachers. And much of that knowledge transfer was interrupted by colonization in the region.

The islands were first claimed by Germany in 1886, and control of the islands  was traded between other foreign colonizer governments  until they gained their independence in 1986, a process  which took nearly twenty years. And, while under US control in the ‘40s and ‘50s, dozens of nuclear tests were  conducted on islands in the area. Like, if you’ve heard of Bikini Atoll,  that’s part of the Marshall Islands.

The people who’d lived there before the nuclear tests were forced to leave by the US government. Many of the islands where nuclear weapons testing happened still  can’t be occupied by people. So between the people who were  forcibly removed from their homes and those who were  poisoned with radioactive fallout wayfinding has become a threatened art form.

But the community hasn’t given up on wayfinding. In 1989, Alson Kelen, a navigator  and advocate launched a program to teach young Marshallese traditional  skills, including wave piloting and canoe building, to preserve  wayfinding traditions and culture. Plus, through measurements  and simulations, physicists have started trying to translate  stick chart motifs into physics jargon and equations, decoding  the wave knowledge they hold.

Unfortunately, life in the  Marshall Islands is becoming increasingly precarious, even  without the nuclear weapons. Sea level rise has led to catastrophic flooding, destroying homes, roads, and crops. These threats to their  physical space make it urgent to preserve their culture  and traditional knowledge.

Stick chart navigation developed in response to the needs of the Marshallese people at the time, and has constantly evolved as  life on the islands changed. In some ways, physicists like Huth are a part of the next step in the wayfinding tradition, integrating indigenous  knowledge with Western science tools to more deeply connect  both groups to the ocean. Here’s hoping that these  efforts help these charts, and the knowledge they represent, to stick around. [♪OUTRO]