Springtime for Mythbuster Part III: Flat Earthers Score a Point!

Last week I introduced you to the Flat Earth Society Forum. Not all the posters on this forum are Flat Earthers. There are many "Roundies" who like to post there just to heckle or argue with the Flat Earthers.

One such Roundy is this fellow who challenges the Flat Earth doctrine with the phenomena of water swirling down the terlet when you flush it. (Caveat: Some of the posts on the thread I link to are crude and in bad taste. Just thought I'd warn you before you click.)

Roundy's argument is this: No one can deny that the toilet does not swirl when flushed as i gurantee every single one of you goes to the toilet several times a day and performs this action. Now i am sure many of you also know this is because of the rotation of a ROUND Earth. If the Earth were flat then the water would not swirl and the whole amusement of goign to Australia just to see the water swirl another way would be lost!!!!

The problem with Roundy's point? Besides grammar, spelling and capitalization? The direction water swirls down your terlet depends entirely on how your terlet is constructed, not which side of the equator it is installed.

Poor Roundy has fallen for the old urban legend that you can see the effect of the Coriolis force in water rotating down your bathroom drains. Specifically, according to the myth, water is supposed to swirl counter-clockwise in the northern hemisphere, and clockwise in the southern hemisphere.

The Coriolis force is caused by the fact that a point located on earth's equator will travel around the earth faster than any point north or south of it during one revolution of an earth day. This is because a point on the equator has to travel a greater distance than a point anywhere else on the globe, and in the same 24 hour period.

You can see, therefore, the Coriolis force working on big, slow moving hurricanes. The water underneath a hurricane will be moving faster nearer the equator, and that will cause the air to spin in the same direction as it flows toward the low pressure center. That is why satellite photos of hurricanes look like pinwheels: they spin counter-clockwise in the north and clockwise in the south.

However, your terlet covers a much smaller area than a hurricane, and there is only a minuscule fraction of a difference between how much faster the equater-side of your terlet is moving around earth's rotation than the opposite rim.

Now, Roundy's point is not entirely without merit. Under extremely controlled conditions, you can see the Coriolis force affect slowly draining water. These conditions are explained on this interweb.

But it is highly unlikely for you to find a terlet that operates under those controlled conditions. Most likely, your typical terlet swirls down the pipe in whichever direction the jets are pointed.

Unfortunately, debunking Roundy's terlet argument fails to actually disprove the round earth theory. But it is gratifying to see a round-earther get defeated in an argument.

And that's a victory we can all savor!