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Oct. 1, 2013 - Skeptoid
15:23
Skeptoid #382: Into the Maelstrom (or Not)

A look into the plausibility and historicity of the ferocious maelstrom of legend. Learn about your ad choices: dovetail.prx.org/ad-choices

Transcriber: nvidia/parakeet-tdt-0.6b-v2, sat-12l-sm, and large-v3-turbo
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Time Text
Real Maelstroms vs Literary Myths 00:04:09
Edgar Allan Poe's Maelstrom is one of those wonderfully romantic literary devices, a huge gaping whirlpool that swallows entire ships whole.
Maelstroms are, of course, real, but is there actually one somewhere in the world with the gargantuan dimensions described by Poe?
And is it truly a real hazard to navigation?
The Maelstrom is up next on Skeptoid.
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You're listening to Skeptoid.
I'm Brian Dunning from Skeptoid.com.
Into the Maelstrom.
Or not.
Today we're going to go in search of a real live sea monster, one that has graced the pages of fiction and non-fiction alike.
The legendary Maelstrom is a whirlpool that eats men and ships alike.
Anything that gets caught up in its great funnel is sucked to the depths and crushed forever, never to return to the surface or the light.
Does such a mighty beast actually exist somewhere in the world?
The word maelstrom comes from the Dutch for grinding current and has come to refer to any current-induced whirlpool.
There are a lot of them throughout the world, including famous ones that reappear with each tide.
Maelstroms first became infamous among the public at large when Edgar Allan Poe wrote his fictional 1841 short story, A Descent into the Maelstrom, in which an ancient mariner recounts his tale of being aboard a ship that was sucked down to its doom.
Never shall I forget the sensations of awe, horror, and admiration with which I gazed about me.
The boat appeared to be hanging as if by magic midway down upon the interior surface of a funnel vast in circumference, prodigious in depth, and whose perfectly smooth sides might have been mistaken for ebony,
but for the bewildering rapidity with which they spun around and for the gleaming and ghastly radiance they shot forth as the rays of the full moon from that circular rift amid the clouds which I have already described streamed in a flood of golden glory along the black walls and far away down into the inmost recesses of the abyss.
At first I was much too confused to observe anything accurately.
The general burst of terrific grandeur was all that I beheld.
When I recovered myself a little, however, my gaze fell instinctively downward.
In this direction I was able to obtain an unobstructed view from the manner in which the smack hung on the inclined surface of the pool.
She was quite upon an even keel, that is to say her deck lay in a plane parallel with that of the water, but this latter sloped at an angle of more than 45 degrees so that we seemed to be lying upon our beam ends.
I could not help observing, nevertheless, that I had scarcely more difficulty in maintaining my hold and footing in this situation than if we had been upon a dead level.
And this, I suppose, was owing to the speed at which we revolved.
The story referenced an actual maelstrom in Norway called the Muskstraumann, an area between some islands off the coast where the incoming and outgoing tides collide.
Herman Melville referenced the same maelstrom 10 years later in Moby Dick.
At its height, the Muskstraumann comprises an area 8 kilometers wide that's peppered with maelstroms up to 50 meters across.
Today, tourist boats and airplanes go out there daily to show off the spectacle.
Why Water Doesn't Suck You Down 00:09:00
Tourists in the maelstrom?
How could that be?
Why don't they get sucked down?
As you can probably surmise, Poe grossly exaggerated the Muskstraumann.
It is not, as the old mariner described, a single near-vertical funnel hundreds of feet across.
A maelstrom that large couldn't have enough energy to hold back enough water to form much of a funnel.
Let's take a quick look at the science of maelstroms.
First of all, we're not going to discuss eddies.
An eddy is a current flowing around in a circle.
It has no vortex in the center, and it's really just a conventional current where all the water is flowing around at the same speed.
Many of the maelstroms you might think you see are just eddies.
For example, there was a famous eddy about a half a kilometer across in a Japanese harbor following the 2011 tsunami.
It was not a maelstrom.
For our purposes today, eddies are not the type of whirlpool we're going to discuss.
There are two very different types of whirlpools that are commonly seen in water, and it's important to differentiate between the two.
The most common is a suction vortex, seen when you pull the plug in a bathtub or sink.
All the water moves toward the drain, and when it collides in the middle, its momentum is converted to angular momentum, and a vortex forms.
A vortex is nature's way for an agitated fluid to seek its lowest energy state.
We've discussed the physics of vortices before on Skeptoid, but we didn't discuss whether they actually suck you down.
They don't, really.
This is a huge misconception.
The hole in the center of a whirlpool is not the result of water moving downward, but of water moving outward.
As it rushes around the vortex, going faster at the center, its momentum tries to carry it in a straight line, away from the center.
Centripetal force pushes the water away from the center of the whirlpool.
At the surface where water pressure is least, it's possible for a hole to form.
But deeper, as water pressure counteracts the centripetal force, the hole gets smaller, so we end up with a funnel shape.
There is no downward current.
This is better illustrated by the second type of whirlpool, which is the type of the maelstrom of legend.
Rather than the agitating force being an outward flow through a drain at the bottom, the agitating force is two opposing currents colliding.
This is a constant input of energy, which the water must dispel.
A vortex is the most efficient way for this to happen.
Most maelstroms around the world are of this type, caused by river currents or tidal currents.
Depending on a number of factors such as the size of the body of water and the speed of the differential, the vortices might be small or large, many or few.
A ship pulling away from a dock might create a lot of little fast vortices, while a tide churning through a large inlet might create one huge slow one.
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But in none of these whirlpools is there a downward current at the center.
The physics of where the water goes just don't work that way.
If you were swimming on the surface near one, you would go around and around, but you wouldn't be drawn toward the center.
If you swam into the center, you would descend along with the surface to the depth of the funnel, but once at the bottom, you would just be spinning like a top.
There is nothing pulling you down.
There are two effects you've probably observed that don't seem to square with this explanation.
First is when you stir a bucket of water that has some sand in it.
Notice that all the sand at the bottom collects in the center.
You might ask how that could be if water does not flow toward the center of the vortex.
When you stir a bucket, you're not creating a vortex.
In a vortex, water moves slowest at the outside and fastest at the center.
When you stir a bucket, the opposite is true.
You're creating a uniformly rotating mass, like a record on a turntable.
Fast-moving water at the outside where you're stirring creates turbulence where it moves against the bottom of the bucket, kicking up sand.
The sand bounces around on the turbulence and settles at the center, where current and turbulence are the least.
The second effect is seen when you stir a cup of tea, all the leaves go toward the center, which suggests that a current is pulling them there.
Wrong, there is no current toward the center, which is why the swimmer doesn't get sucked in.
Pressure is lowest in the center of the vortex, the eye of the storm, as it were.
It's also lowest at the center of a uniformly rotating mass, like the stirred bucket.
Anything lighter than water floats toward the center, squeezed out of the high pressure areas toward the low pressure center.
A lucky few divers have seen thread-like vortices caused by currents stretching all the way from the seafloor to the surface, their visible filaments made of tiny bubbles and other lightweight debris from the water.
Poe got another technical detail wrong, and that's the way the ship traveled bow first all the way around the funnel, as if it were sailing forward at high speed.
Because fluid in a vortex moves faster at the middle, a boat pointing north would point north all the way around.
The physics of a vortex are such that any rigid object placed in it would be held in the same orientation at every point, regardless of how far it is from the center.
If Poe had known that, he could have sent his ancient mariner on an even more terrifying and sickening tumble into the abyss.
Maelstroms are indeed dangerous to boats, however, but not because of the threat of being sucked underwater.
In the most violent maelstroms, currents are strong enough and rotate at a sharp enough angle that small boats can be capsized.
Water is pretty dense and heavy, and exerting that much pressure from different angles on a small boat can easily manhandle the hull in just about any direction.
Larger boats can be knocked aside by the sideways current, but maelstroms wide enough to encompass a larger boat are lower energy than the small sharp ones.
So in practice, a maelstrom is not likely to give a large boat much more than a thrill ride.
Water has so much mass that the gravity easily overcomes any centripetal force in a large maelstrom.
The square cube law tells us that as the dimensions of the maelstrom double, the mass cubes.
Thus, funnels are biggest in smaller whirlpools and small or non-existent in the largest.
Famous maelstroms are found all over the world.
The most violent is the Saltstraumen, also in Norway, where the tide rushes through a narrow inlet.
However, the real danger here is from turbulence caused by the rocks, creating boiling currents that flow up, down, and all around.
But the maelstroms themselves are scarcely more than a few meters across at their best.
Scotland, Canada, Japan, and New Zealand all have their share of famous tidal maelstroms, and none approach the type of monstrosity described by Poe, nor should we expect them to.
Let the myth that whirlpools suck things underwater be put to rest.
It seems to make sense and the shape of the funnel makes the suction appear to be obvious.
But the science behind the maelstrom shows that it just ain't so.
Swimming Safely in Boiling Currents 00:02:09
But please don't email me that the mythbusters tried swimming in one and found the claim to be plausible.
They stirred a giant bucket, creating a uniformly rotating mass, not a vortex.
And Adam never tried letting go of the tether.
If he had, he would have been stuck spinning in the middle at the lowest point and would have struggled.
But there simply wasn't any downward current that could have sucked him to the bottom.
So swim with a bit more confidence.
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