What way does the water go down the drain?

[Number Six]

I think it's a myth that the water goes down the drain in different directions in the northern and southern hemisphere. I read a really elegant explanation of it all once, I forget where but it might have been in the book "Bad Astronomy." It included and explanation of how some tricksters living right on the equator fool tourists by having the water going down the drain in one direction north of the equator and then moving to the other side of the room, across the equator, and having the water go down the drain in the other direction. But it was awhile ago and now I can't remember the details.

 

[Aoidoi]

http://www.ems.psu.edu/~fraser/Bad/BadCoriolis.html

There is a bit on it on Bad Astronomy the website (where I got the link), not sure about the book.

 

[pupdog]

It was often used as an example of the Coriolis force. But various local forces acting on the system and such things as slope of the sink surface and chance overpower the Coriolis force at this scale so that the water may swirl clockwise or it may swirl counterclockwise.

 

[phildonnia]

Weather systems and ocean currents will flow in the predicted direction however.

 

[WildCat]

It goes down where I live.

 

[TillEulenspiegel]

It's not woo-woo, it's a real phenomenon. There is an effect on rotation of water and weather systems. The cyclonic and anticyclonic nature of these are fact, it is due to the coriolis effect. That doesn't mean that it translates to local systems exactly ( like the sited sink) but rather larger systems.

I first took interest in this when I saw an episode of the simpsons ( US cartoon, irreverent, and sometimes poinient) when a main character called Austrilia to see if the toilet flushing was really opposite of the northern hemisphere...........and by golly it was!

 

[BillyJoe]

TillEulenspiegel,

Due to the coriolis effect, water would tend to swirl anti-clockwise in Australia but, take it from me, it doesn't always do that.
As someone said above, other factors such as movement in the water and the shape of the container are far more important than the coriolis effect in determining which way the water swirls as it passes out of the sink.

But this is true of anywhere in the world, so don't take it from me try it out for yourself

BillyJoe.

 

[ceptimus]

TillEulenspiegel,

Due to the coriolis effect, water would tend to swirl anti-clockwise in Australia but, take it from me, it doesn't always do that.
As someone said above, other factors such as movement in the water and the shape of the container are far more important than the coriolis effect in determining which way the water swirls as it passes out of the sink.

But this is true of anywhere in the world, so don't take it from me try it out for yourself

BillyJoe.

I think you have it widdershins BillyJoe. Clockwise in Australia (if the effect were pronounced enough to be observable that is).

 

[DangerousBeliefs]

Straight Dope - Do bathtubs drain counterclockwise in the Northern Hemisphere?

 

[TillEulenspiegel]

TillEulenspiegel,

Due to the coriolis effect, water would tend to swirl anti-clockwise in Australia but, take it from me, it doesn't always do that.
As someone said above, other factors such as movement in the water and the shape of the container are far more important than the coriolis effect in determining which way the water swirls as it passes out of the sink.

But this is true of anywhere in the world, so don't take it from me try it out for yourself

BillyJoe.

Ya Billy, that why I said it dosn't translate to "local" phenomonon, the link calls it's sphere of influience-macroevents. I love Australia ( and it's inhabitents) but I don't have enough money to fly there and test it for myself, so if someone wants to send me a ticket in the name of scientific inquirey , I'd be happy to come over

 

[Iamme]

Remember that thing you could buy, like at a Spencer's Gift Store in the mall, that had like two bottles conjoined neck to neck with some device in between, and you could watch the vortex effect when you turned the bottles upside down? I wonder if THIS swirled the water the same way everytime?

 

[athon]

Coriolis forces work due to the fact the planet is a rotating sphere. The atmosphere covering it, being fluid, does not move at the same speed as the solid rock beneath it. As the rotation at the equator is faster (i.e., think one wheel, the equator, having to move faster to complete one revolution, while another wheel, the pole, does not have to move as fast to do the same turn) the winds move in a slight bias towards the polar regions.

In other words, coriolis does work in a similar nature on small bodies, but only when it is a sphere surrounded by a fluid. The global coriolis forces (responsible for the trade winds) are not even distantly connected to how water goes down a sink, which depends on the force of the moving water, the shape of the bottom of the sink and where the tap is situated above the sink (we tested this in a school experiment last year, to disprove the very notion in a year 11 class. I was enraged because another science teacher had supported the theory, and my words were simply against his. We experimented with four different drains, measuring the variables. A victory for science that day!)

Athon

 

[BillyJoe]

Two errors in one post

It's anti-clockwise in Australia like Cepi said.
And Tulip was saying exactly what I corrected him for.

BJ

 

[The Bad Astronomer]

FWIW, it's chapter 2 in my book.

 

[scribble]

Remember that thing you could buy, like at a Spencer's Gift Store in the mall, that had like two bottles conjoined neck to neck with some device in between, and you could watch the vortex effect when you turned the bottles upside down? I wonder if THIS swirled the water the same way everytime?

Great memory, and brilliant to bring it up. Indeed, I had a few of these, being fascinated by shiny things and such. And indeed, it would happily swirl the water either way, depending on which way I shook it.

The fact is these forces exist, and they're far too weak to have an effect on this scale.

 

[iSani]

Joy! A testable hypothesis!

I quickly rushed to the bathroom to fill the sink and added a few drops of soap to make the movement of the water more apparent. And guess what happened?

Clockwise. And since I live in Finland, I'm pretty certainly in the northern hemisphere. While I'd like to do a proper statistical analysis on this (can you imgaine the water bill?), this little experiment at least shows that water can rotate against the direction of the coriolis effect.