I understand that the rotation of the Earth is what makes water drain in a spiral, and that the northern and southern hemisphere’s sinks will drain in opposite directions. Why is this so? Also, if the Earth stopped spinning, water would stop spiraling. Again, why?
It all spins in the same direction you’re just looking at it from the opposite side.
Oh yeah, and you might want to try a search on that.
The spin of the earth has less effect on which way water spirals down a drain than do a hundred other factors. The folk wisdom that says it always drains one way in the northern hemisphere and the other way in the south is a myth.
Here’s what Cecil wrote about it: http://www.straightdope.com/classics/a1_161.html
Try this: fill your kitchen sink with water. Pop the drain and give the water a stir clockwise - it’ll empty in a big spiral. Now, fill it back up, pop the drain and give it a counterclockwise stir. It’ll happily spiral that way instead.
Hours of enertainment …
Ironically, without reading this post, I noticed something very interesting in my kitchen sink as I was doing the dishes. Some teflon pans get washed by hand, and I noticed a whirlpool of suds had formed at the drain where water was slowly draining off. With the kitchen sink’s spout being able to swivel, I tried a little experiment myself.
If the spout was to my left, the whirlpool of suds rotated counterclockwise, but when the spout was swivelled over to my right, the suds reversed direction to a clockwise rotation!
Just a few nights before, I had gained similar results in the bathtub. When dumping out a ~5 gal vaporizer, allowing the water to
dump out along the centerline of the tub, the whirlpool at the drain rotated clockwise. Yet, when running the shower, the whirlpool rotated counterclockwise.
I was quite puzzled myself having always been taught about the Coriolus (sp?) effect caused by the earth’s rotation. I have never fully understood this effect, and this sink enigma makes the issue even less clear!
Finally, the same question has to be asked about the swirl of water of a flushing toilet. They say a toilet’s water will swirl counterclockwise in the Northern hemisphere, and clockwise in the Southern hemisphere. Has anyone observed an exception here, too?
“They’re coming to take me away ha-ha, ho-ho, hee-hee, to the funny farm where life is beautiful all the time… :)” - Napoleon IV
Yes. But it wasn’t in my toilet. Wait, of course it was. But I didn’t really look, I just sorta glanced.
rocks
There’s no enigma; as other posters have pointed out, the Coriolis force is way too small to affect the motion of water in a sink, bathtub, or toilet unless you take exceptional care to remove other effects. These effects include the symmetry (or lack thereof) of the containerand the intial conditions, and the initial state of motion of the water. Toilets are very asymmetric; they have angled water entries that force a particular rotation (to scrub the bowl and to move … er … solids towards the center of the rotation). And moving the sink faucet changed the initial motion of the water.
One report claims that the effect of the Coriolis force in a sink or bathtub is on the order of 0.01 percent of the effect of other factors. The Bad Coriolis FAQ is interesting and not excessively technical. The Coriolis Force Explained and Debunked is also worth a look.
jrf