THE SHAPE OF THE EARTH
the age of space travel, we all know the world is "round." But ancient
civilizations had no way to measure the size or the shape of the Earth. So, they
came up with their own imaginative explanations. For example:
In the Cherokee nation, people believed that mud rose from under the waters and
formed an island with four corners - the Earth. The Sun went underneath the island
at night, and rose again the next day.
Ancient Babylonians thought the Earth was inside a hollow mountain, floating on
a sea. Everything - the sun, moon, sky, star, water - was inside this mountain
Ancient Egyptians believed the whole Earth was part of their god, Keh. The stars
were the jewels of a goddess in the sky and their god of air held her aloft.
Ancient Hindus thought that the Earth was in an upside-down bowl, being carried
by elephants. The elephants stood on the back of a turtle that was standing on
top of a snake. What the snake stood on, they hadn't quite worked out.
Polynesian creation stories set the Earth in a basket with a lid. A hole cut in
the top by a god lets in light. The woven grass at night lets light peek through
in the form of stars.
people believe that Columbus was the first to realize that the world is round.
Actually, the round-Earth concept has been with us since ancient Greece.
very early Greeks thought Earth was a flat disc floating on water. But in about
540 BC, the renowned mathematician Pythagoras proposed the theory that the world
was a sphere. The concept had many supporters, including Aristotle.
about 250 BC, Eratosthenes, librarian at the Library of Alexandria, even came
up with a calculation of the Earth's spherical size.
heard that in midsummer in the town of Syene, Egypt, the noonday sun shone directly
into a deep well. He measured and discovered that in Alexandria, 787 kilometers
north, the angle of the sun was about 7.2 degrees on the same date. With these
measurements, he computed the circumference of the Earth.
enough, considering how he came up with the numbers and how little he had to prove
them, Eratosthene's estimates were very close.
Scholar, Posidonius (135-151 BC) did something similar over a century later, using
the bright star Canopus. He measured the angles of the star from the horizon in
two locations to get a fairly accurate estimate of the Earth's circumference.
FOURTEEN HUNDRED AND NINETY TWO
years later, Christopher Columbus came along, trying to make his now famous voyage
to Asia by going west. The decision of whether to fund his trip came down to analyzing
the accumulation of estimates that had been gathered over the centuries.
on Eratosthenes' numbers, King Ferdinand believed that Columbus's fleet could
never make it all the way to Asia: it was simply too far. He didn't see any reason
to supply ships and crews only to have them die halfway from their goal.
used a ploy common in modern-day politics, marketing and engineering: If the numbers
don't support your conclusion, find some numbers that do. He found another estimate
by Ptolemy dating from about AD 150. It was completely erroneous, but estimated
that the Earth was about half its true size
so Queen Isabella agreed to
support the voyage.
for Columbus, America got in his way, or he never would have reached India or
anywhere else. Crossing both the Atlantic and the Pacific combined would have
been an impossible feat with the ships and supplies he had.
wasn't until 1958 when the Vanguard I satellite took the first photographs of
earth from space that scientists were able to determine the planet's exact shape.
The photographs proved the world is round
not exactly. Scientists reported that the Earth is an oblate spheroid - i.e.,
it's not quite round.
the Earth spins, it gets a slight bulge near the equator. Near yes, but not (as
you might suspect) exactly on the equator.
of this bulge, the Earth is flattened very slightly on either end. Its circumference
at the equator is 24,902 miles, and the circumference around the poles is 27 miles
less than that: 24,875 miles. Not a big deal really - if the world were the size
of a basketball, it would be more perfectly round than a real basketball is. But
still, after guessing for so long, scientists can't resist the opportunity to
get it exactly right.
WORLD IS PEAR SHAPED
toward the end of his life, Columbus came to believe the Earth was shaped like
a pear. He developed this theory during his third voyage to the New World. When
he was sailing west near the equator, he noticed that the North Star made a wider
circle around the Pole than it did when he was sailing in more temperate latitudes.
this he deduced that he had been sailing gradually up hill and therefore closer
to the sun, which explained why the weather was getting warmer. "I have come
to the conclusion," he wrote, in a letter to Queen Isabella, "
that the Earth is not round, but of the form of a pear
Where the stalk grows
being the highest and nearest the sky."
believed that if he sailed far enough, he would eventually reach the Garden of
Eden, which is located in the pear's stalk. (Ripley's Believe It or Not.)