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Only large air masses spin with Earth
![[NOAA] Hurricane Diana, Sep. 11, 1984](hurricane-diana.jpg) Q: In the North Hemisphere does water go clockwise down the sink and counterclockwise in the
South Hemisphere? What happens on the Equator ? -M. Kelvin Harris, Cambridge, England
A: Water doesn't go down drains in any particular direction no matter where you are on Earth. The
rotation of Earth does effect great masses of air (this phenomenon is called the Coriolis force), causing
them to rotate around a low pressure center in the same direction as the underlying Earth. The water in a
sink, however, doesn't cover enough of Earth's surface and drainage lasts too short a time for the weak
Coriolis force to affect it. In fact, Coriolis force doesn't even cause tornadoes or dust devils to spin-just
hurricanes and other large storm systems.
[NOAA] Hurricane Diana, Sep. 11, 1984
If it weren't for the Earth's rotation, winds would blow fairly straight from a high pressure region to a low pressure one and Earth would
have no hurricanes. The Earth's spin curves the wind to the right of its direction of travel in the Northern Hemisphere and to the left in the
Southern one. On the Equator, the effect vanishes. So air masses there appear to move in more or less straight lines and do not form
hurricanes.
(Answered by April Holladay, science correspondent, Apr. 10, 2002)
Further Surfing:
USATODAY.com: Weather basics, Understanding Coriolis Force
Pennsylvania State U., Alistair Frasier Bad Science: bad Coriolis
The Weather Book by Jack Williams, pp. 35 - 36.
Hurricane Watch by Bob Sheets and Jack Williams, pp. 38 - 40
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