Published: November 2012
Escape Velocity
Awkward on land, emperor penguins soar through the sea. Now scientists have discovered the secret of their speed.
Photograph by Paul Nicklen
Roger Hughes has never seen emperor penguins in the wild.
But when he saw them in a BBC documentary, rocketing through the sea
with trails of bubbles in their wakes, he had an insight that would lead
to a surprising discovery. A marine biologist at Bangor University in
north Wales, Hughes had recently been talking with his wife about the
lubricating properties of new competitive swimsuits. He wondered: Maybe
those bubbles help penguins swim faster.
Over beer in a pub, Hughes bounced his hypothesis off his friend John Davenport, a marine biologist at University College Cork in Ireland. “Roger thought I’d have the answer straightaway,” says Davenport, who studies the relationship between animals’ body structures and their movements. But he didn’t know what the bubbles did for the penguins. It turns out no one else knew either. The two men combed the scientific literature and found that the phenomenon had never even been studied. So they decided to do it themselves.
With the help of Poul Larsen, a mechanical engineer at the Technical University of Denmark, they analyzed hours of underwater footage and discovered that the penguins were doing something that engineers had long tried to do with boats and torpedoes: They were using air as a lubricant to cut drag and increase speed.
When an emperor penguin swims through the water, it is slowed by the friction between its body and the water, keeping its maximum speed somewhere between four and nine feet a second. But in short bursts the penguin can double or even triple its speed by releasing air from its feathers in the form of tiny bubbles. These reduce the density and viscosity of the water around the penguin’s body, cutting drag and enabling the bird to reach speeds that would otherwise be impossible. (As an added benefit, the extra speed helps the penguins avoid predators such as leopard seals.)
The key to this talent is in the penguin’s feathers. Like other birds, emperors have the capacity to fluff their feathers and insulate their bodies with a layer of air. But whereas most birds have rows of feathers with bare skin between them, emperor penguins have a dense, uniform coat of feathers. And because the bases of their feathers include tiny filaments—just 20 microns in diameter, less than half the width of a thin human hair—air is trapped in a fine, downy mesh and released as microbubbles so tiny that they form a lubricating coat on the feather surface.
Though feathers are not an option for ships, technology may finally be catching up with biology. In 2010 a Dutch company started selling systems that lubricate the hulls of container ships with bubbles. Last year Mitsubishi announced that it had designed an air-lubrication system for supertankers. But so far no one has designed anything that can gun past a leopard seal and launch over a wall of sea ice. That’s still proprietary technology.
source
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Behind the Lens
Penguins are pretty big. Did you worry one might hit you?
I
was hit once, quite hard in the head. I was in a safe place—out of
their way—but a penguin went way off course, flew through the air, and
landed on my head. He just casually stood up and walked away. A 70-pound
bird to the head hurts a lot, but I’m lucky I’ve never been injured. I
was also hit by a leopard seal. Its strategy is to fly out of the water
and knock over penguins like bowling pins.
How close were you to the penguins in this shot?
I
was about three feet away. My camera was in a [protective] Seacam
housing; they were sending up so much spray and ice it would’ve
destroyed my camera. The noises and thuds when they landed on the ice
were incredible. They knocked the air out of themselves and made a
squeak. We were lucky in that there was really only one opening where
the penguins entered and exited the ocean.
Did you enjoy living with them?
The
first night in camp, the penguins followed me home. They stood outside
and bugled all night. By the third night, I had a hard time sleeping,
and the romanticism began to wane.
source
Over beer in a pub, Hughes bounced his hypothesis off his friend John Davenport, a marine biologist at University College Cork in Ireland. “Roger thought I’d have the answer straightaway,” says Davenport, who studies the relationship between animals’ body structures and their movements. But he didn’t know what the bubbles did for the penguins. It turns out no one else knew either. The two men combed the scientific literature and found that the phenomenon had never even been studied. So they decided to do it themselves.
With the help of Poul Larsen, a mechanical engineer at the Technical University of Denmark, they analyzed hours of underwater footage and discovered that the penguins were doing something that engineers had long tried to do with boats and torpedoes: They were using air as a lubricant to cut drag and increase speed.
When an emperor penguin swims through the water, it is slowed by the friction between its body and the water, keeping its maximum speed somewhere between four and nine feet a second. But in short bursts the penguin can double or even triple its speed by releasing air from its feathers in the form of tiny bubbles. These reduce the density and viscosity of the water around the penguin’s body, cutting drag and enabling the bird to reach speeds that would otherwise be impossible. (As an added benefit, the extra speed helps the penguins avoid predators such as leopard seals.)
The key to this talent is in the penguin’s feathers. Like other birds, emperors have the capacity to fluff their feathers and insulate their bodies with a layer of air. But whereas most birds have rows of feathers with bare skin between them, emperor penguins have a dense, uniform coat of feathers. And because the bases of their feathers include tiny filaments—just 20 microns in diameter, less than half the width of a thin human hair—air is trapped in a fine, downy mesh and released as microbubbles so tiny that they form a lubricating coat on the feather surface.
Though feathers are not an option for ships, technology may finally be catching up with biology. In 2010 a Dutch company started selling systems that lubricate the hulls of container ships with bubbles. Last year Mitsubishi announced that it had designed an air-lubrication system for supertankers. But so far no one has designed anything that can gun past a leopard seal and launch over a wall of sea ice. That’s still proprietary technology.
source
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Emperor Penguins
Photograph by Dean Gushee
The Moment Paul Nicklen
Shooting Stars
Capturing the flight of emperor penguins in Antarctica is no easy feat.
They rocket around underwater, then explode out of holes in the sea ice
(above). To follow them, Paul Nicklen used polar survival skills he
learned as a child living among the Inuit on Canada’s Baffin Island. He
read the ice and winds, and pressed the shutter even when he lost
feeling in his fingers. Every so often, penguins burst from the water at
this site, where Nicklen lay waiting. “They soared underwater like
fighter jets in a dogfight,” he says. “Then they’d fly out, land, push
down with their bill, and stand up, going back to that slow, waddling
bird. It was a privilege to see.” —Luna Shyr
Behind the Lens
Penguins are pretty big. Did you worry one might hit you?I
was hit once, quite hard in the head. I was in a safe place—out of
their way—but a penguin went way off course, flew through the air, and
landed on my head. He just casually stood up and walked away. A 70-pound
bird to the head hurts a lot, but I’m lucky I’ve never been injured. I
was also hit by a leopard seal. Its strategy is to fly out of the water
and knock over penguins like bowling pins.How close were you to the penguins in this shot?I
was about three feet away. My camera was in a [protective] Seacam
housing; they were sending up so much spray and ice it would’ve
destroyed my camera. The noises and thuds when they landed on the ice
were incredible. They knocked the air out of themselves and made a
squeak. We were lucky in that there was really only one opening where
the penguins entered and exited the ocean.Did you enjoy living with them?The
first night in camp, the penguins followed me home. They stood outside
and bugled all night. By the third night, I had a hard time sleeping,
and the romanticism began to wane.source
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