Perspective: How geckos stick and unstick their feet

Bjorn Christian Torrissen
Bjorn Christian Torrissen
Published Aug. 22, 2014

Your Benjamin goes furthest in Mississippi

The Tax Foundation, a think tank that generally has a probusiness leaning, studied how far $100 would go in each state, using data from the Bureau of Economic Analysis. Regional price differences are strikingly large and, as the foundation points out, have serious policy implications. A Benjamin goes the furthest in Mississippi, where $100 will buy what would cost $115.74 in another state that is closer to the national average. You can think of this as meaning that Mississippians are about 15 percent richer than their nominal incomes suggest. On the other end, $100 is worth the least in the District of Columbia and Hawaii. An example of what that means: A person who makes $40,000 a year after tax in Kentucky would need to have after-tax earnings of $53,000 in Washington, D.C., just to have an equal standard of living, let alone feel richer.

Sticky gecko feet

How can geckos run upside down across ceilings and stop short on smooth vertical surfaces? It's the angle at which they hold their feet and something called the van der Waals force — a weak intermolecular force between atoms. The sole of a gecko foot is covered in tiny folds of skin, which in turn have tiny hairs that branch and branch again until the tips, called seta, are just a few nanometers across. This provides millions of tiny locations where the van der Waals force can work so that, amplified millions of times over, it is strong enough to allow a gecko to hang from a ceiling indefinitely. But geckos can run at speeds of up to 20 body lengths per second, so its foot has to unstick fast, too. In the Journal of Applied Physics, researchers at Oregon State University explained how; the foot's angle makes them sticky or not. On a ceiling, a gecko pulls the hairs on its foot sideways a bit, giving enough force to support its weight. When the gecko wants to move its foot, it lifts straight up, "unsticking" it. No "gecko shoes" for us, though. "Geckos are the upper limit of the size of animal that can use this technology," said Alex Greaney, lead author of the paper.

Deborah Netburn, Los Angeles Times

Near death on a jet, the study

On Aug. 24, 2001, Air Transat Flight 236 ran out of fuel en route from Toronto to Lisbon with 306 passengers aboard. As the interior lights flickered and oxygen masks dangled from the ceiling, weeping flight attendants instructed everyone to prepare for a crash landing into the sea. Then the pilot located a small military base in the Azores, and after 25 minutes of hell, the plane touched down — violently — to tears and applause. (Also to flames: The wheels were on fire.)

One of the passengers was a psychologist named Margaret McKinnon, who studies behavioral neuroscience at McMaster University in Hamilton, Ontario. "After the lights went out and the plane lost altitude so sharply, I suspected we would probably die." Two years later, she and her colleagues got 15 of the men and women from the flight to recount their experience during those grueling minutes. The researchers wanted to understand more about terror's fingerprints on the brain; the relationship between mnemonic habits and posttraumatic stress disorder; and what role clarity and vividness play in a given memory's power to haunt.

The study, forthcoming in the journal Clinical Psychological Science, found that a survivor with PTSD was no more or less likely to mention the flight attendant "with the shaky voice" or the pilot shouting "Brace! Brace!" or the quiet punctuated by sounds of praying. What did vary among the accounts was the number of details that had nothing at all to do with the flight. Passengers with PTSD produced far more external details ("factual information or extended events that did not require recollection of a specific time and place," "tangential … autobiographical details," editorializing, repetitions, metacognitive claims like "I can't remember") than those without, who just stuck to the facts. It may be that those with a weaker command over their remembering machinery may be more at risk for PTSD, which is characterized by the chaotic bursting forth of past disturbances. Brian Levine, a co-author of the study and a professor at the University of Toronto, put it this way to the Association for Psychological Science: "What our findings show is that it is not what happened but to whom it happened that may determine subsequent onset of PTSD."

Katy Waldman, Slate

How fish hide? It's transparent

Sharks and whales can swim with impunity, but many seafaring creatures need to hide in plain sight to survive; in the deep ocean, there is no cover. Transparency is the most obvious strategy, one that Dr. Sönke Johnsen of Duke University began researching almost 20 years ago. The oceans, which make up more than 90 percent of the Earth's livable space, are full of almost invisible animals. Johnsen's measurements of the see-through creatures that he has brought up to the surface found that 20 to 90 percent of the light passed through, undisturbed. "You could read a book through these animals," he said. What the deep ocean takes away (it offers no cover), it gives back (in being nearly the same density as body tissue). When light passes into a material of a different index of refraction, which is often proportional to the density, part of the light reflects and part of it bends. That's one reason there are no transparent cows or pigeons: The density of air is so much less than that of flesh that even a crystal-clear, see-through animal or bird would probably be easily spotted from its reflections. Water is much denser, and body tissues are roughly the density of water, greatly reducing the amount of scattering.

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Kenneth Chang, New York Times