Coriolis effect

August 27, 2005 11:59 AM

In University I was thought that the Coriolis effect while responsible for the spin of weather systems and ocean currents had no impact on the way water in a toilet bowl/sink spun. I believe this and understand the reasoning behind it. So my question is that why on my two trips to the Southern Hemisphere have I observed the water spinning anti-clockwise. Was this just coincidence or my mind playing tricks on me?
posted by daveirl to Science & Nature (20 answers total)

The Coriolis force is orders of magnitude smaller than other parameters affecting the direction of the spinning (as described in the article you are linking to). So, yes, it's coincidence.
posted by swordfishtrombones at 12:10 PM on August 27, 2005

It could also have to do with things which are common to plumbing in the southern hemisphere which are different in the northern hemisphere.

Perhaps threading on pipes or some other plumbing based practice is responsible?
posted by tomierna at 12:16 PM on August 27, 2005

If you cut a plastic milk jug in half, and place it over a bucket, you can see that with a little bit of a start, the water will run in either direction.
This is actually a tourist scam around the equator, where folks charge to see the water slosh one way on one side and the other way on the other side, by leaping back and forth over the equator. It's got nothing to do with the Coriolis effect.
posted by klangklangston at 12:18 PM on August 27, 2005

Oops, forgot to link to a classic Straight Dope article on this topic.
posted by swordfishtrombones at 12:19 PM on August 27, 2005

Response by poster: See the really weird thing is that the episode of the Simpsons was my first experience with the concept (although I knew about the ocean currents/hurricanes from secondary school). Then I went to Argentina and observed that the water spun anti-clockwise.

After I came back from Argentina I started University and learned that the Coriolis Effect didn't have anything to do with the water in the toilet and convinced myself that my mind had been playing tricks on me. So then when I arrived in New Zealand last June imagine my surprise when the water went anti-clockwise!

So the consensus is that it's my mind + coincidence!
posted by daveirl at 12:26 PM on August 27, 2005

I'm currently in Chile and have just observed the water draining clockwise.
posted by edd at 12:37 PM on August 27, 2005

.... and now in reverse.
posted by edd at 12:42 PM on August 27, 2005

the way the water spins in the toilet bowl is directly refective of the direction - angle the jets spit the water out at.
posted by crewshell at 12:56 PM on August 27, 2005

I used to go back and forth between the US and New Zealand all the time, and I entertained myself by fiddling around with various drains to make the water spin the "wrong" direction. Coriolis may exert some force, but not a determinative one.

(I was young.)
posted by socratic at 1:26 PM on August 27, 2005

hey edd - if you want to have a minimal mefi meetup, drop me a line at [e-mail] - i work at ctio, but live in santiago. there's another mefite in santiago (signal), so we could even make make it a wild threesome... this is the first time i've known someone visit (if you're observing i hope you're not staring at the same clouds my partner just emailed me about from las campanas).
posted by andrew cooke at 1:44 PM on August 27, 2005

Well, now that we have the toilet water figured out. How about the rotation of the storms and the inversion of super cooled air freezing the Earth's surface in the movie "The Day after Tomorrow" that I just watched last night on HBO? Any theoretical basis for this in science or just pure Hollywood "spin"?
posted by WoodChuck at 1:50 PM on August 27, 2005

That really bugged me about The Day After Tomorrow when I watched in theaters (well that and the fact it was incredibly stupid). The whole "we had to look up the temperature oil freezes at" is stupid, it freezes at a fairly high temperature and aviation fuel needs anti-freezing elements to keep the various molecules in the gas from freezing at high altitudes. A-1 is around -57F and the coldest recorded temperature on earth came in around -91F, so its not like no one has ever had this problem. I would imagine high altitude helicopters have insulation on them and other devices to compensate for the cold, keep in mind that -91F was recorded on the ground, not at a higher altitude. I don't know if that would incur instant freezing as shown in the movie, I highly doubt it. In Alaska they keep their cars running to prevent their standard motor oil from freezing. I doubt that our atmosphere could get colder than what the temperature in outer space (I think the dark side of our planet would be something less than -297F). There's obviously at atmosphere of some kind (as indicated by the blue sky in the hole itself), so I would guess that even in the "super cold" atmosphere it would be several times warmer than -297F.

Also stupid error #249 in the movie shows them walking from Philadelphia to NYC in just a day or two -- in blizzard conditions with minimal supplies.
posted by geoff. at 2:24 PM on August 27, 2005

I'm wrong, in the movie they state that the fuel froze at -150F ("We had to look it up..."). I really doubt any storm system could create temperatures like that. Perhaps a meterologist would like to correct me.
posted by geoff. at 2:27 PM on August 27, 2005

The Day After Tomorrow was an absolute disaster in terms of scientific accuracy. I wouldn't try to even apply basic logic or fact to any of its premises.

http://intuitor.com/moviephysics/dayAft.htm
http://www.csmonitor.com/2004/0528/p01s04-sten.html
http://www.decaturdaily.com/decaturdaily/news/040526/movie.shtml
posted by Rhomboid at 2:45 PM on August 27, 2005

Absolute disaster of scientific accuracy is right on the money... I work as a geophysicist and can attest to that.
posted by rolypolyman at 2:58 PM on August 27, 2005

I got really excited about "proving" the Coriolis effect not long after I moved to Sydney. Too bad I was entirely *wrong*.
posted by web-goddess at 3:19 PM on August 27, 2005

I also learned in university that this wasn't true. I learned it the embarrassing way: we were discussing coriolis forces, and I was telling my friends "That's like how below the equator the drain empties in the other direction". The professor overheard me, made me repeat it in front of everyone, and then said "That's an urban myth."
I hope your revelation was at least less embarrassing.
posted by easternblot at 8:37 PM on August 27, 2005

The reason you noticed it spinning the other way in the southern hemisphere is probably selection bias.
posted by mendel at 8:40 PM on August 28, 2005

Er, my mistake -- I mean confirmation bias.
posted by mendel at 9:11 PM on August 28, 2005

Woah, what is going on in this image!?
posted by delmoi at 11:26 AM on August 29, 2005