t*********t
发帖数: 1058 | 1 来自MIT, Princeton, 和Virgina Tech的四位科学家为我们揭开了谜底。
文章转自: http://www.nytimes.com/2010/11/12/science/12cats.html?_r=1
下载Paper: http://web.mit.edu/preis/www/mypapers/cats_Science_Express_Reis_Aristoff_Stocker.pdf
录像：http://video.nytimes.com/video/2010/11/11/science/1248069317702/how-cats-lap.html?scp=2&sq=cats%20and%20drinking&st=cse
By NICHOLAS WADE
Published: November 11, 2010
It has taken four highly qualified engineers and a bunch of integral
equations to figure it out, but we now know how cats drink. The answer is:
very elegantly, and not at all the way you might suppose.
Cats lap water so fast that the human eye cannot follow what is happening,
which is why the trick had apparently escaped attention until now. With the
use of high-speed photography, the neatness of the feline solution has been
captured.
The act of drinking may seem like no big deal for anyone who can fully close
his mouth to create suction, as people can. But the various species that
cannot do so — and that includes most adult carnivores — must resort to
some other mechanism.
Dog owners are familiar with the unseemly lapping noises that ensue when
their thirsty pet meets a bowl of water. The dog is thrusting its tongue
into the water, forming a crude cup with it and hauling the liquid back into
the muzzle.
Cats, both big and little, are so much classier, according to new research
by Pedro M. Reis and Roman Stocker of the Massachusetts Institute of
Technology, joined by Sunghwan Jung of the Virginia Polytechnic Institute
and Jeffrey M. Aristoff of Princeton.
Writing in the Thursday issue of Science, the four engineers report that the
cat’s lapping method depends on its instinctive ability to calculate the
point at which gravitational force would overcome inertia and cause the
water to fall.
Being engineers, the cat-lapping team next tested its findings with a
machine that mimicked a cat’s tongue, using a glass disk at the end of a
piston to serve as the tip. After calculating things like the Froude number
and the aspect ratio, they were able to figure out how fast a cat should lap
to get the greatest amount of water into its mouth. The cats, it turns out,
were way ahead of them — they lap at just that speed.
To the scientific mind, the next obvious question is whether bigger cats
should lap at different speeds.
The engineers worked out a formula: the lapping frequency should be the
weight of the cat species, raised to the power of minus one-sixth and
multiplied by 4.6. They then made friends with a curator at Zoo New England,
the nonprofit group that operates the Franklin Park Zoo in Boston and the
Stone Zoo in Stoneham, Mass., who let them videotape his big cats. Lions,
leopards, jaguars and ocelots turned out to lap at the speeds predicted by
the engineers.
The animal who inspired this exercise of the engineer’s art is a black cat
named Cutta Cutta, who belongs to Dr. Stocker and his family. Cutta Cutta’s
name comes from the word for “many stars” in Jawoyn, a language of the
Australian aborigines.
Dr. Stocker’s day job at M.I.T. is applying physics to biological problems,
like how plankton move in the ocean. “Three and a half years ago, I was
watching Cutta Cutta lap over breakfast,” Dr. Stocker said. Naturally, he
wondered what hydrodynamic problems the cat might be solving. He consulted
Dr. Reis, an expert in fluid mechanics, and the study was under way.
At first, Dr. Stocker and his colleagues assumed that the raspy hairs on a
cat’s tongue, so useful for grooming, must also be involved in drawing
water into its mouth. But the tip of the tongue, which is smooth, turned out
to be all that was needed.
The project required no financing. The robot that mimicked the cat’s tongue
was built for an experiment on the International Space Station, and the
engineers simply borrowed it from a neighboring lab. | r*****e
发帖数: 7853 | 2 Our cats are much better than these four engineers.
Without the elegant integral equations, they can lap water easily
【在 t*********t 的大作中提到】
: 来自MIT, Princeton, 和Virgina Tech的四位科学家为我们揭开了谜底。
: 文章转自: http://www.nytimes.com/2010/11/12/science/12cats.html?_r=1
: 下载Paper: http://web.mit.edu/preis/www/mypapers/cats_Science_Express_Reis_Aristoff_Stocker.pdf
: 录像：http://video.nytimes.com/video/2010/11/11/science/1248069317702/how-cats-lap.html?scp=2&sq=cats%20and%20drinking&st=cse
: By NICHOLAS WADE
: Published: November 11, 2010
: It has taken four highly qualified engineers and a bunch of integral
: equations to figure it out, but we now know how cats drink. The answer is:
: very elegantly, and not at all the way you might suppose.
: Cats lap water so fast that the human eye cannot follow what is happening,
| T*****u
发帖数: 7103 | |
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