For hundreds of years sailors have told stories about miles of glowing ocean during moonless nights. This phenomenon is known as "milky seas," but the only scientific sample was collected in 1985. So atmospheric scientist Justin Hudson, a PhD candidate at Colorado State University, used accounts spanning 400 years to create a database of milky seas. By also using satellite images to visually confirm the tales, Justin hopes his research brings us one step closer to unraveling this maritime mystery. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave.Got a question about a scientific mystery? Let us know at [email protected]. Learn more about sponsor message choices: podcastchoices.com/adchoicesNPR Privacy Policy
Chapter 1: What are milky seas and their historical accounts?
You're listening to Shortwave from NPR. It's 1849. You're on a ship coasting through the middle of the ocean at night. It's calm, glassy waters and a clear sky full of stars. Then you see off the side of the boat a glow. Not from another ship or the night sky, but from the surface of the sea. It's coming from the water.
I cannot permit this opportunity to pass by without describing to you, in the best way I am able, a most extraordinary phenomenon.
There's a miles-long swath of glimmering milky water.
Chapter 2: What is Justin Hudson's research on milky seas?
The vessel shortly after entered a vast body of water of the most dazzling brightness and of highly phosphorescent nature. In fact, it looked as if we were sailing over a boundless plain of snow or a sea of quicksilver.
This is just one of many written accounts of Milky Seas that goes back 400 years, according to Justin Hudson, an atmospheric science researcher at Colorado State University. He compiled a database of recent satellite images and all the reports of Milky Seas he could find from over the years as part of his PhD thesis.
And a lot of them were written off as just, you know, drunks, drunk sailors at the bar trying to impress each other with more, you know, better tall tales than someone else had.
Chapter 3: Why were milky seas tales often dismissed?
Justin's research advisor, Stephen Miller, says it wasn't until about 100 years ago that tales of glowing seas began to be taken more seriously.
I think in the 1900s, we started receiving more reports from sources such as navies, commerce vessels. These are trustworthy accounts. These aren't pirates and sailors of yore spinning their tall tales like Justin was just mentioning.
One group definitely not spinning a tall tale, the lone research vessel that accidentally wandered into a milky sea and took the only scientific sample in 1985.
And the reason for the lack of sampling is simply because milky seas tend to be very remote. And about 70% of the world is covered in ocean and there's just very few people out in any one given spot.
Chapter 4: What was the significance of the 1985 scientific sample?
So today on the show, maritime lore deconstructed. How a database of sailor stories and satellite images could help scientists better understand an enduring mystery of the sea. I'm Regina Barber. You're listening to Shortwave, the science podcast from NPR.
Justin, a lot of the stories, like the one we heard at the top of the episode here, are from this database that you compiled as part of your PhD. But this is not the first time a Milky Sea database has been made. Many have been made over the last couple centuries, right?
Chapter 5: Why haven't more scientific samples of milky seas been collected?
So about every 40 years, someone seems to learn about Milky Seas, gets fascinated by the idea, and then builds the best database they could of all the sightings they were able to gather on Milky Seas. And what has happened to all of those previous databases is that they've all been lost in some way.
At sea?
Not at sea, I hope. The last person to make a database before us, his name was Dr. Peter Herring. And as far as he knows, his database, if it still exists, is just in some unknown archive room in the UK Navy storage somewhere.
We say that there's the first scientific sample in 1985, but people did take samples in these historic references. So somebody might have drank it?
Yeah, there are a few accounts in the database. where the best scientific tool someone had to study this was just taking a swig of this strange glowing water out of the ocean and seeing what they could figure out from there. And there's this one account from the early 1800s where the ship's surgeon had heard about this before from sailors in the Middle East.
And they had claimed that the water tasted fresh. And so when he encountered one, he immediately took up a bucket and tasted it himself. And he actually complains in the account that it just tastes like normal seawater.
Yeah, I think that just adding to this a little bit of irony is that the leading idea for what causes milky seas is bacteria. Right. A form of bacteria that will glow upon reaching a critical population. But anyway, the Vibrio bacteria that are thought to be causing milky seas are also of the sort that would cause things like cholera.
and other, you know, pretty nasty things that can happen inside of our bodies. So the idea of drinking the water may not always be the best advised thing to do.
So, like, this bacteria, Vibiro harveyi, right? And it's, like you said, like, we think it causes these other things. It's been pretty well studied. Stephen, can you tell me more about this bacteria and why we think it's the cause of the Milky Seas?
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Chapter 6: What is the role of bacteria in causing milky seas?
You know, this is a hypothesis. I want to clarify that. We don't know for sure that this is what's happening, but it's the leading hypothesis.
Justin, what's so special about this bacteria? Like what does this bacteria, how does it glow and how is that different from the bioluminescence we like have seen in like fireflies or other marine bioluminescence?
Yeah. So the main way it differs is kind of what Steve touched on is that it's the function behind why they're bioluminescing. So a firefly, its bioluminescence is sort of like communication of other fireflies. And the more typical bioluminescence you see out in the ocean is caused by this organism called a dinoflagellate. and it glows in response to some kind of shock.
Something nudges it, or it gets inside a crashing wave that's on the shore, and it glows as it's called a burglar alarm response, as sort of a way to tell whatever is trying to eat it, that like, you've been spotted, so you're in danger and you should get away from me.
Chapter 7: How do luminous bacteria function in the ocean?
Whereas with this Vibrio harvey that we think is behind it, it's glowing actually not to scare away predators, but to attract predators intentionally.
So Justin, like scientists at this point, we're like, we know it's this like luminous bacteria. And you mentioned that there's a story from like the 1700s of Captain Newland. And he said he thought it had to do with some like microscopic organism. How does that make you feel? Like we're only just like a little bit further than what he thought, right? Like how much further are we?
Yeah, I have a couple different emotions about that actually. Ben Franklin actually has a letter he wrote to a friend of his in the 1750s where he was complaining how he had carried all these experiments to prove that it was actually electricity and lightning in the ocean causing bioluminescence, but actually he has come to the conclusion that it's just some unknown living being we can't see.
Captain Newland, 20 years later, sort of in that same, I guess, scientific discourse, comes to the same conclusion about Milky Seas. And I'm just kind of impressed that they were able to sort of really narrow it down that well back then And then the fact that we still haven't been able to come that much further since then is kind of...
It's a little depressing and shows just kind of how hard it is to actually study this.
Is that the whole point of this database, Stephen, so that we can finally know a little bit more? Can you tell me, like, why this database is so needed?
We need to find a way to position ourselves to sample very thoroughly, spatially and temporally, what a Milky Sea is made out of and how it's different from the surrounding waters.
So what we're doing is forming a database, then looking for relationships between when milky seas happened and other parameters that we measure all the time, like the nuances of sea surface temperature changes and which directions the winds are blowing and the circulations that happen seasonally and subseasonally.
And the plan is to pair the database with other tools, like satellite images, right, to get a real-time look at things.
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