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Go to Brilliant.org/SciShow to learn more. [♪ INTRO]. In 2017, scientists were scouting the floor of the Black Sea, trying to study how sea levels had changed since ancient times.

But then, something unexpected suddenly appeared in the darkness: a ship. An ancient ship, as a matter of fact, half-buried on the cold, dark seafloor nearly two kilometers below the water's surface. Upon further investigation, the team discovered that this 23-meter trading vessel actually seemed to date all the way back to Ancient Greece, to the days of philosophers like Plato.

That meant that they had accidentally found the world's oldest known intact shipwreck. The scientists were able to crack this ship's secret thanks to a combination of biology, engineering, and ocean sciences; all of which are involved in a field called maritime or marine archaeology. And by looking at how they did it, there's a lot we can learn about how we study shipwrecks in general.

This might not come as a surprise, but not all shipwrecks are as beautifully-preserved as this one. Even wrecks half as old are prone to serious damage and decay. The problem is often the critters that live in the ocean.

Many types of organism like to burrow into or eat waterlogged wood, including mollusks like shipworms and piddocks, and tiny crustaceans called gribbles. Not to mention plenty of microbes. Shipwrecks can also turn into impromptu reefs as corals and other types of sea life grow on top of them.

And while that's very cute in an, “Aw, look they found a home!” sort of way, it's not great for the ships themselves. This kind of life either hides wrecks, or breaks them down into a pile of mush. This ancient ship managed to avoid that fate, though, but not because there was anything special about Greek shipbuilding back then.

This boat just happened to sink in a very convenient location. 2 kilometers beneath the Black Sea, in the cold, lightless depths, there's very little oxygen. It's what's known as an anoxic environment. In this case, it happens because the Black Sea is really two separate layers of water: a less salty one that generally comes from rain, rivers, or streams, and a more salty one that comes in through a deep channel from the Mediterranean.

That extra-salty layer is more dense than the fresher stuff, so it stays near the bottom of the sea and generally doesn't mix with the water above it. And since oxygen gets absorbed from the atmosphere down, no mixing means no oxygen. This makes it extremely hard for life to survive down there, and that means ships rot much, much more slowly.

The Black Sea is actually home to all kinds of wrecks, and the team that found this 2017 one discovered about five dozen others on their expedition. This one just happened to be the oldest. The researchers found it while prowling around the seafloor using an ROV, or remotely-operated vehicle.

Along with human-operated and autonomous versions, vehicles like these are really your bread-and-butter when it comes to exploring deep sea shipwrecks. ROVs are underwater robots. They typically look like a box covered in cameras with propellers, and might come with extra features like robotic arms or scientific instruments.

They also come in all different sizes, where the largest ones can be the size of a truck. As they descend, long cables connect the ROV to a human operator on the surface. Then, the operator can send commands to the robot, while the robot sends video and data to the operator.

Now, normally, expeditions don't just send ROVs to patrol the ocean and hunt for sunken ships. Instead, they might use something like a magnetometer to scan huge areas for promising metal objects, and then send an ROV to investigate. This team just happened to skip that step because they were already using an ROV for their other research.

In a lot of ways, they just got really lucky. Still, even though finding this ship was straightforward, studying it took more calculations and planning. Since the boat was so deep, researchers couldn't just send a couple of scuba divers down there.

The world's deepest scuba dive only went down about 300 meters, and deep dives can be dangerous because of water pressure. So instead of sending down humans, the marine archeologists used their ROV. And to really examine it, they used something called photogrammetry: a way to measure and study objects by, essentially, taking their picture.

To do it, they used the camera and imaging device on the ROV to take a long series of snapshots. Then, once they collected hundreds or even thousands of them, they fed them into a computer, which built a highly detailed, composite 3-D portrait. This portrait then let the team figure out things like the exact size and shape of the boat, which is how they knew it was about twenty-three meters long.

It also allowed them to zoom in on specific features, like how the hull was put together. That gave them more information about how it was constructed and how well it might have performed in the open sea. Photogrammetry is really helpful for record-keeping, too.

Like, in this case, the scientists decided to blow away some of the seafloor sediment to study the buried parts of the ship. So now, if they want to know what things looked like beforehand, they have a detailed record. Also, besides being useful for the scientists themselves, these 3-D models are cool because they make it very easy to share exactly what an expedition is seeing.

Compared to using traditional diagrams, scientists can more easily publish papers, invite analysis from other colleagues, or give the public insight into a hidden treasure. They can even build virtual reality simulations. Because looking at diagrams in a paper?

That's cool. But flying through a VR simulation of a spooky underwater shipwreck? That is awesome.

Of course, scientists don't just want to know how big a boat is, or what condition it's in. They also want to know things like its age or where it came from. Which is, you know, generally important in archaeology.

To do that, researchers can look for certain artifacts or historic construction methods. But when that kind of thing isn't available, or if they want more info, they might also take small samples from the wreck itself. For this Black Sea wreck, one of the ROVs took samples of the ship's wood for study.

That allowed them to figure out what species of wood the boat was made of, and it helped them figure out how old it was. To determine the boat's age, the team used radiocarbon dating. It's a method that's super common in all kinds of fields related to natural history, because it relies on carbon.

And virtually all living things are full of the stuff. Normally, carbon is made of six protons and six neutrons, but occasionally, you find forms with an unusual number of neutrons, too. One of those oddballs is carbon-14, which usually forms when radiation alters nitrogen atoms in the atmosphere.

Carbon-14 is unstable, so over time, it turns back into nitrogen. When an organism is alive, it uses both unstable and stable carbon atoms to build its body. And since it's always bringing more carbon in, the ratio of carbon-14 and stable carbon stays roughly the same.

But once the organism dies, it stops acquiring new carbon, and the ratio starts to slowly change. Its percentage of carbon-14 starts to go down. So, by examining the ratio of C-14 to stable carbon, you can tell how long it's been since that organism died.

This is true for all kinds of things, from animal bones to plants. And it's a great way to tell how old a wood sample is. Like, say, a piece of wood you pulled from the bottom of the Black Sea.

For that wreck, scientists were able to use this technique to tell that the wood from that ship came from about 400 BCE. And cue the record books. At the end of the day, having all this information about shipwrecks and where they came from is great.

It's awesome to come across a ship deep underwater and be able to say, “Hey, look, that thing is ridiculously old.” But marine archeologists don't just study these things to collect stats. They want to learn about human history, too. And there's a lot these ships can tell us.

First, and most obviously, they can teach us about the history of sailing and shipbuilding. Because while we might know a society had ships, it's not always clear how those old ships worked. Like, how did they steer?

How were they actually put together? Sometimes all we have to answer those questions is a written description or an artistic drawing, both of which can be inaccurate or biased. For instance, a Greek historian named Herotodus once described a type of river barge called a “baris” from ancient Egypt, but we never actually had proof they existed, until a wrecked one was found in 2003.

Secondly, studying ancient ships reveals things about the world its builders lived in. For one thing, ships often represented some of the pre-industrial society's most complex pieces of technology. They also reveal patterns in how people lived, fought, explored, or traded.

The Black Sea shipwreck, for instance, shows that trade was extensive, even in the time of Ancient Greece. We actually don't know a ton about ancient Black Sea seafaring, so the construction, cargo, and other artifacts can give us hints about who was trading with whom and how. And as we keep using these methods to find more sunken ships, there's likely more we'll learn.

If you want to see this Black Sea wreck in person, you're unfortunately out of luck. In order to preserve the ship, the team is leaving it in its final resting place, which actually happens with a lot of other wrecks. Still, the methods we used to study it, from ROVs to radiocarbon dating, will continue to be used by marine archeologists all over the world.

They'll keep scanning, diving, and exploring, and as they do, we'll learn more about our history sailing the oceans. To understand history, archeologists rely on all kinds of science. They need computers to analyze their data, engineers to build their equipment, and tons of knowledge about biology, chemistry, and physics.

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