Whirly wonderings

Hey DougO,

There is discussion in these parts as to the validity to the common notion that toilets flush in the opposite direction south of the Equator. It has also been submitted that, when directly over the Equator, a toilet will flush straight down. Can you verify or debunk this?

A: I hate to say this, since the toilet swirl direction is one of my favorite science "facts", but, alas, it is a myth. The idea is that the fact that objects on or near the equator are moving faster around the Earth's axis than objects near or at the poles tends to give moving particles a clockwise spin in the Southern hemisphere and a counter-clockwise spin in the Northern hemisphere. True enough. this is called the "Coriolis Effect", named after Gaspard-Gustave Coriolis. He was some French guy.

However, the Coriolis Effect is generally only noticeable in large systems over time, say in weather patterns. Your petite little porcelain bowl is too tiny, globally speaking, to demonstrate much of a preference either way. The fact that water swirls so vigorously in one direction as it leaves the bowl is due to jets concealed under the rim that are pointed in one direction or the other. It does a nice job of picking up after you (so to speak) and makes a satisfying "whoooshgluglugrattle" sound for your entertainment. You could easily pick another model that does the same thing, only going the other way, no matter where you are on the globe.

If you really wanted to see how forces might work at the equator, you could theoretically build a toilet large enough for the forces to be more apparent. I would say about the size of Cuba. I'm not sure where you could get grant money for it, but people seem to have had luck soliciting money on the internet for more ridiculous things.