Bad Astronomy: Misconceptions and Misuses Revealed, from ...

22 BAD ASTRONOMY BEGINS AT HOME
south of the line, the water drains the other way. Proof positive
that the Earth is spinning!
The demonstration is convincing, and McLeary has done it for
many years, raking in tips from the credulous tourists. It has been
seen by countless travelers, and was even featured on the PBS series
Pole to Pole, in which former Monty Python silly man Michael
Palin tours the world, taking in interesting sights. In this particular
episode Palin watches McLeary do his thing and adds, “This is
known as the Coriolis effect . . . it does work.”
Actually, no, it doesn’t. Palin, and who knows how many tourists
before and after him, are being taken in by a fraud. And it
doesn’t end there. This hoary idea is used to explain why toilets
flush in different directions in the northern and southern hemispheres,
as well as the way northern and southern sinks and bathtubs
drain. Many college students claim that their high school science
teachers taught them this fact. The problem is, it’s no fact. It’s
bad astronomy.
The Coriolis effect is real enough. By the 1800s, it had been
known for years that cannonballs fired along a north-south line
tended to deviate from a straight path, always landing west of
their mark if fired toward the south, and east if fired to the north.
In 1835 the French mathematician Gustave-Gaspard Coriolis published
a paper with the unassuming title of, “On the Equations of
Relative Motion of Systems of Bodies.” In it, he describes what has
become known as the Coriolis effect.
Imagine you are standing on the Earth. Okay, that’s easy
enough. Now imagine that the Earth is spinning, once a day. Still
with me? Okay, now imagine you are standing on the equator. The
rotation of Earth takes you eastward, and after a day you have
swept around a big circle in space, with a radius equal to the
Earth’s radius. On the equator, that means you have traveled about
40,000 kilometers (25,000 miles) in one day.
Now imagine you are on the north pole. After one day, you
have rotated around the spot on which you are standing, but you
haven’t actually gone anywhere. The north pole is defined as the
spot where the Earth’s rotation axis intersects the ground, so pretty