Friday, December 15, 2006

Does water circles backwards below the equator?

Examining the Coriolis effect

There is the myth that water will vortex in a clockwise direction in the southern hemisphere and counterclockwise in the northern hemisphere.

What better place to test this myth than on the equator itself? We went to the exact equator about 15 miles north of Quito Ecuador (only a 4.5 hour flight due south of Miami). It's cool to stand with one foot in each hemisphere.

The Middle of the Earth

A village called “Middle of the earth” just a few miles north of Quito Ecuador is a great place to see the alleged "Coriolis Effect".

Everyone knows that tornadoes and hurricanes rotate counter-clockwise in the Northern hemisphere, but there has been the age-old debate about whether water will circle in a different direction north or south of the equator.

My Garmin GPS acquired five satellites and confirmed that “Middle of the World” is approximately at zero degrees latitude, give or take fifteen feet.

Our guide went on to say that you must be at the exact equator to examine the Coriolis effect because the vortex difference can be observed as little as ten feet into the Northern of Southern hemispheres. Her "proof" that water vortexes in different directions, was much more subtle, and it took me awhile to figure-out how she pulled it off.

Here is the tub that she used for the "proof". First, she proved that water drains straight down on the exact equator, and amazing, no vortexes

She said that a simple, repeatable proof can show the fact that water drains in a different direction in each hemisphere (I'm always suspicious of proofs). At equatorial sites in South America (Brazil and Ecuador) they commonly have a pail of water and a wash basin so skeptical folks can test the Coriolis Effect for themselves.

Next, we step ten feet into the northern hemisphere, where water should circle counterclockwise. Can you see her trick? Take a close look below:

Sho' nuff, the water circled in a strong counter-clockwise vortex when she pulled the plug ten feet into the northern hempsphere. Next we stepped ten feet into the southern hemisphere and repeated the "proof", with the water circling vigorously in a clockwise vortex.

I don't want to spoil the fun, but you can make water circle any way that you want with a subtle slight of hand trick. (hint: It's the way she pours-in the water).