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Slowly spinning Earth, Let lying dogs lay
Q: How fast does the world spin on its axis? (Annie,
Poowong, Australia)
 A:
So fast that our planet bulges at the equator, and yet slower than the fastest
jet.
The Blue Marble, taken by astronaut Harrison Schmidt of
Apollo 17 on Dec. 7, 1972. Courtesy of Earth Sciences and Image Analysis
Laboratory NASA Johnson Space Center and Wikipedia
Earth spins on its axis once, on the average, every 24 hours.
More precisely, a mean solar day is 24 hours plus 0.0016 seconds.
If you lived on the equator, your surface speed through space
would be the distance (Earth’s circumference at the equator) divided by the time
(24 hours). That speed is
40,075.0041 km / 24 h = 1669.79 km/h or 1038 mph.
At your home in Poowong County of Australia, your speed is
somewhat less because you live closer to the pole, where the distance around
Earth is smaller. Indeed, your speed is less by a factor of the cosine of your
latitude (about 38 degrees south). So, your speed is 1038 mph x cos (38
degrees) = 817 mph or 1315 km/h.
Moreover, if you lived at either pole, the distance around
Earth there is zero (a point). So, the speed is zero. "But, you would rotate
along with the Earth, much like being at the centre of a children’s
merry-go-round. The Sun and, in winter, the stars would appear to move around
the sky once a day, more or less parallel to the horizon," says
Robert Massey of the
Royal Observatory Greenwich in London.
In Poowong County, the speed at which you spin seems fast.
But, a 727-passenger jet goes almost as fast (600 mph), a Winchester .270 rifle
bullet goes over twice as fast (1924 mph) and the Space Shuttle races ahead over
20 times faster (17,500 mph).
By the way, if Earth spun about 800 times faster, she would
hurl us off her surface (at the equator) and into space.
Further Reading:
Royal Observatory Greenwich:
Planet
Earth
Wikipedia:
Earth
Boy Scout space exploration merit badge:
how fast
is fast?
University of Michigan, Windows to the Universe:
Movement of the Earth
Q: Why do dogs lie on their backs? Our
Okie does in a contorted manner, but he seems happy. (Birdie, Browns Summit,
North Carolina)
 A:
In general, dogs lie on their back for three reasons.
"A dog lying down" Pencil and watercolor on paper, by James
Ward, 1769 – 1859.
First, if your dog lies there totally relaxed, he probably
does so because it "just feels good", says veterinarian
Holly R. Nash, of Drs. Foster & Smith, Inc. in Rhinelander, Wisconsin. He
must feel safe since he’s exposing his throat, gut, and heart to possible
attack.
Or, second, he may be showing respect. Dogs live in
family-based packs like wolves, and follow deference rules, controlled, perhaps,
by the oldest female, says
Karen L. Overall, ABS Certified Applied Animal Behaviorist and researcher at
the University of Pennsylvania.
So, a dog that lies down and rolls over on his back may simply
be deferring to you.
Dogs have let us — a different species — into their social
structure over the millennia since we first domesticated wolves, at least 14,000
years ago and perhaps 60,000 to 100,000 years ago.
Finally, he may be withdrawing, disengaging, seeking time
alone. Note the dog lying on his back in the drawing. His chest is partially
covered (with his paws). This indicates withdrawal, says Overall. In the canine
world, his behavior clearly states, "Leave me alone." Disturb him, even to pet,
at your own risk.
Further Reading:
Karen L. Overall, How animals perceive the world: non-verbal signaling,
Atlantic Coast Veterinary Conference, 2001
Dog behavior and training by Drs. Foster & Smith, peteducation.com
Karen L. Overall, Development of behavior: evolutionary background – normal dog
behavior, Atlantic Coast Veterinary Conference, 2001
The Origins of the Domesticated Dog,
Yext Vets -- Find a vetinarian
Nicholas
Dodman, What does your body language say to your dog, PetPlace.com
Charlie’s dog safety tips for kids, Department of Internal Affairs, New
Zealand
(Answered Jan. 24, 2006)
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