Feline physics

Cats are kings of animal acrobatics

Posted: Sunday, July 24, 2005


  A cat walks on a wood fence in Great Falls, Mont., Friday, July 22, 2005. (AP Photo/Great Falls Tribune, Robin Loznak) ROBIN LOZNAK

A cat walks on a wood fence in Great Falls, Mont., Friday, July 22, 2005. (AP Photo/Great Falls Tribune, Robin Loznak)


Cats can do some pretty amazing things. They seem to have a propensity for dogging death by a whisker, often leaving their owners and any onlookers wondering, "How'd they do that?"

Invariably someone will say the cat used up one of its nine lives, but what does that mean? Where did the expression that cats have nine lives come from, anyway?

According to "Brewer's Dictionary of Phrase and Fable," a cat is said to have nine lives because it is "more tenacious of life than many animals."

Most cat owners could tell you their furry friends are inquisitive explorers and fearless acrobats, especially when contrasted to humans, which are clumsy bipeds by comparison.

This superstition of felines' knack for dodging death appears to be closely tied to a cat's ability to seemingly always land on their feet after a fall, as well as their ability to frequently survive falls from high places with few, if any, visible injuries.

"Visible" is the key word here because, although cats may give the appearance that they are unscathed after a fall or other brush with death, they may sustain hidden injuries, such as bloody noses, cracked teeth or broken bones.

The ability of a cat to survive accidents that would kill humans or other animals is not due to multiple lives, however. It is due to several advantages they possess.

A cat's small size and low body weight soften the impact as they make contact with the ground after falling from great heights and, perhaps more importantly, the highly developed inner ears of cats equip them with an unusually keen sense of balance, which is critical to their ability to land on their feet.

This sense of balance allows a cat falling upside down to right itself by rapidly determining its position, repositioning itself and making any adjustments necessary to ensure it lands on all fours.

This feline ability was first explained in 1894 by a French physiologist, Etienne-Jules Marey, who recorded on film a cat that he held upside down by its legs and then dropped.

The resultant film took 60 images a second and demonstrated how a cat lands on its feet. As the cat fell, a twisting reaction began and the cat maneuvered its head, back, legs and tail to lessen the impact.

Since cats land on all paws, the impact from landing on the ground is absorbed by all four. Jared Diamond, author and professor of physiology at the University of California Los Angeles, determined cats bend their legs when they land, which spreads the impact not only through bones that could easily break, but through joints and muscles, as well.

After consulting several New York City veterinarians, Diamond was surprised to learn that a cat stands a greater chance of survival if it falls from a higher place than from a lower place.

Data gathered from the veterinarians on their feline patients indicated 10 percent of their patients died after falling from two to seven stories. The higher it fell from up to the seventh story, the greater the chance it would be killed.

In contrast, only 5 percent of fatalities occurred when the animals fell from the eighth through the 32nd stories.

Diamond used the laws of physics to explain why these survival rates vary in an article in Nature magazine titled "Why cats have nine lives." All falling, bodies — regardless of their masses — accelerate by 22 miles per hour per second through their falls, until reaching a final speed known as terminal velocity.

This happens because the object's — in this case, the cat's — friction with the air slows the fall. The smaller the object's mass and the greater its area, the more it will slow down.

A cat falling from a higher floor, after it stops accelerating, spreads its legs into an umbrella shape, which increases the area against which the air must push and increases the friction, thus slowing the cat's fall.

Through the cat's highly developed sense of balance, they buy more time to maneuver their body in preparation for landing on all fours. A cat falling from a lower height does not have the opportunity to increase its body's area, slow its fall or position its body to land on all four feet.

That's all well and good, but it still doesn't answer the question of "why nine?" This, unlike the physics of falling, has multiple possible explanations.

Nine is known as the trinity of trinities and is a mystical number often invoked in folklore and religion, particularly those that ascribe to the Father, Son and Holy Ghost.

The cat was once revered in Egypt and this is a possibility for where its nine lives began. The priesthood in On — known to the Greeks as Heliopolis and now a suburb of Cairo — worshiped Atum-Ra, a sun god who gave life to the gods of air, moisture, earth and sky who, in turn, produced Osiris, Isis, Seth and Nephthys. These gods are collectively known as the Ennead, or the Nine.

Vestiges of this ancient, cat-worshipping religion lingered into the middle ages, until the cat became a symbol of the profane rather than the sacred. Linked to witches and witchcraft, cats were caught and killed by the thousand for their believed supernatural powers, such as their resilience to injury and perceived ability to return from the dead.

Cat superstitions survive to this day, as black cats are believed to be unlucky, especially around Halloween.

Even with a cat's agility, grace and amazing ability to survive, the safe place for them is indoors with all doors and windows secured to prevent any possible escape or injury.

Joseph Robertia is a reporter for the Peninsula Clarion. He has worked with wildlife and domestic animals for more than 10 years as a veterinary technician, a zoo keeper, and most recently as a zoologist for the Wildlife Conservation Society. He welcomes any pet-related questions or story ideas, but please none of a veterinary nature. Ideas and questions can be sent to his attention by e-mail at news@peninsulaclarion.com.

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