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  • Thanks to Brilliant for supporting this episode of SciShow.

  • 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 archeology.

  • 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 archeology.

  • 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 “barisfrom 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.

  • Another thing they definitely need is the ability to think like a scientist.

  • And even if you're not a trained researcher, that's something you can learn,

  • thanks to Brilliant's course on Scientific Thinking.

  • To try this course, you actually don't need any science background,

  • just a love of puzzles and a willingness to try new things.

  • The course will give you everything else you need to know, and by the end,

  • you'll know how to think about the world in a different, more analytical way!

  • Brilliant also has a bunch of other courses covering

  • science, engineering, math, and computer science.

  • So whether you want to learn basic logic skills

  • or how neural networks work, there's something for you.

  • If you want to try it out, you can sign up at Brilliant.org/SciShow.

  • And as a thank-you for watching the show, the first two hundred people to

  • sign up at that URL will get twenty percent off their annual Premium subscription.

  • If you find any courses you really like, let us know in the comments.

  • [♪ OUTRO]

Thanks to Brilliant for supporting this episode of SciShow.

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世界上最古老的沉船事件 (The Oldest Shipwreck in the World)

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    林宜悉 發佈於 2021 年 01 月 14 日
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