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View Full Version : What Way Does Your Bathtub Drain?



Eroica
2005-Mar-13, 04:40 PM
OK, so the Coriolis Force has nothing to do with the way the water drains out of a bathtub - as the BA clearly describes in Chapter 2 (Flushed with Embarrassment) of his book. It's just a myth. So if you fill, say, a dozen different bathtubs and pull the plugs on them, some will drain clockwise and some counterclockwise. Right?

Why is it then that on every occasion I have tested this hypothesis the water always drains counterclockwise?

Is it possible that there's some truth to the myth after all, only it's not the Coriolis Force that is to blame, but something else? Like magnetism.

Water is a polar compound, so the water in your bathtub has a lot of ions in it - positively charged hydrogen ions (protons) and negatively charged hydroxyl ions (OH). Presumably as these drain out of the tub they are deflected by the Earth's magnetic field - pretty much the way air molecules in depressions and anticyclones are deflected by the Coriolis Force. Could this affect the way the water drains?

V-GER
2005-Mar-13, 04:50 PM
Just tested it with the kitchen sink, starts clockwise, ends up counterclockwise, strange.

Eroica
2005-Mar-13, 05:01 PM
Just tested it with the kitchen sink, starts clockwise, ends up counterclockwise, strange.
What about your bathtub? Sinks are smaller, so the effect might not be the same. I was hoping to exclude them from this survey.

By the way, did you just vote: "Southern Hemisphere - Counterclockwise"? When was Finland moved to the Southern Hemisphere?

V-GER
2005-Mar-13, 05:03 PM
Don't have a bathtub so I'll just exclude myself.

V-GER
2005-Mar-13, 05:06 PM
Eroica wrote:

By the way, did you just vote: "Southern Hemisphere - Counterclockwise"? When was Finland moved to the Southern Hemisphere?

Apparently I did, meant to vote other. Now I've really ruined your
survey.

Eroica
2005-Mar-13, 05:08 PM
Apparently I did, meant to vote other. Now I've really ruined your
survey.
Never mind. I tried to include a "None of the Above" option, but it didn't seem to come out.

W.F. Tomba
2005-Mar-13, 09:52 PM
I tried my bathtub. It started counterclockwise and finished clockwise.

How many times have you tested this, Eroica?

mutant
2005-Mar-13, 09:55 PM
Another urban legend sneaks it's way into the Bad Astronomy site.

Inferno
2005-Mar-13, 11:19 PM
It mostly just seems to flow into the drain, neither clockwise nor counterclockwise. I even tried to angle it in one direction or another, but it doesn't stay that way.

George
2005-Mar-14, 04:16 AM
Which way does the rubber ducky go? The two could be highly related.

Im right handed. If I'm in the tub, I swish the hot water to the back of the tub with more right hand motion than left. This initiates a clockwise motion.

If I shower, the nozzle is aimed more away from the curtain which, in my case, is to my left. This creates clockwise motion, too.

The drain pipes also are factors. Water flow has a non-uniform flow rate through a bend. A bend is, likely, just beneath your tub. This could have some effect on the flow, I think.

A Thousand Pardons
2005-Mar-14, 09:38 AM
Why is it then that on every occasion I have tested this hypothesis the water always drains counterclockwise?
Are you only doing this in one particular bathtub? The shape of the bathtub has a large influence.

For instance, when we used to model large scale fluid flow by using rotating water tables, the differences in latitude were most simply simulated by slightly sloping side to side the bottom of the table. If your bathtub is not perfectly level, that's going to induce a preferential rotation, similar to the appearance of large scale weather systems.

If you could jack up one side of your house, and repeat the experiment, that would be interesting, but you might have to play with it a little bit.

Eroica
2005-Mar-14, 12:55 PM
I've tested it in three different bathtubs in three different houses - all with the same result. Okay, hardly conclusive of anything. I'm just curious to see if the survey gives a fairly random spread among the various outcomes (which, I suppose, it should do).

Eroica
2005-Mar-14, 12:58 PM
Another urban legend sneaks it's way into the Bad Astronomy site.
At least have the patience to read the OP before you comment. I don't think there are any urban legends which suggest that Earth's magnetic field could possibly influence the way water drains down a plughole (though I may have just created one! :D ).

George
2005-Mar-14, 03:55 PM
I've tested it in three different bathtubs in three different houses - all with the same result. Okay, hardly conclusive of anything. I'm just curious to see if the survey gives a fairly random spread among the various outcomes (which, I suppose, it should do).
Another consideration is the plug removal. As the drain becomes unplugged, there may be a slight rotation established favoring one direction.

Can you use a pull-type plug? If so, pull from different directions.

mutant
2005-Mar-14, 08:47 PM
Another urban legend sneaks it's way into the Bad Astronomy site.
At least have the patience to read the OP before you comment. I don't think there are any urban legends which suggest that Earth's magnetic field could possibly influence the way water drains down a plughole (though I may have just created one! :D ).

Well, I was referring to the old urban legend that water drains a certain way down the toilet or bath tub or sink depending on what hemisphere you live in. I thought BA dealt with this in his book and that you seemed not to believe it. However I could be wrong. I usually am.

As far as reading the post, I read it 3 times. Next time I will take notes.

Eroica
2005-Mar-15, 12:27 PM
Well, I was referring to the old urban legend that water drains a certain way down the toilet or bath tub or sink depending on what hemisphere you live in. I thought BA dealt with this in his book and that you seemed not to believe it. However I could be wrong. I usually am.

As far as reading the post, I read it 3 times. Next time I will take notes.
I apologise if I came off a little snippy. I got the impression from your post that you were accusing me of somehow contaminating the purity of the BABB. :D

I was just throwing out an idea, expecting it to be quickly shot down. But no one has commented yet on a possible role for the Earth's magnetic field....

A Thousand Pardons
2005-Mar-15, 01:55 PM
But no one has commented yet on a possible role for the Earth's magnetic field....
The effect by a magnetic field is deflection in different directions for the opposite ions you talk about in the OP--since the charge below even the macro level is essentially neutral, the effect should be minimal or even non-existent, shouldn't it?

Eroica
2005-Mar-17, 05:47 PM
But no one has commented yet on a possible role for the Earth's magnetic field....
The effect by a magnetic field is deflection in different directions for the opposite ions you talk about in the OP--since the charge below even the macro level is essentially neutral, the effect should be minimal or even non-existent, shouldn't it?
If you say so, but the hydroxyl ions are 33 times as massive as the hydrogen ions. Would that make a difference?

A Thousand Pardons
2005-Mar-17, 10:14 PM
I'd have to do some calculations. What is the average molecule speed in water? :)

tjm220
2005-Mar-17, 10:44 PM
I'd have to do some calculations. What is the average molecule speed in water? :)

African or European? :-k

The Supreme Canuck
2005-Mar-18, 01:00 AM
Does it need to carry a coconut?

WaxRubiks
2005-Mar-23, 05:24 PM
So which way should the water go?
It seems as though it should be atomically a democratic decision.
10kg of water votes to go clockwise,
10kg+1molecule of water votes to go anti-clockwise,
(ignoring the fact that a more energetic molecule gets more votes than a less energetic molecule)

once the ball is rolling, the potential kinetic energy of the water provides the real energy(edit- for the wirlpool) as it falls through the hole...

And how ever small the difference, the molecules of water at the southern end of the bath are moving faster(west to east) than the molecules at the northern end. (edit- in the northern hemisphere anyway)

Hay presto, a democratically elected whirl pool!!!!!

WaxRubiks
2005-Mar-23, 05:34 PM
Perhaps, as it is a democracy based upon the energy level of the water molecule they could be said to be olichary wirlpools!

Eroica
2005-Mar-23, 05:40 PM
I guess the neutral molecules will always greatly outnumber the ionised ones, so my idea's a nonstarter. #-o

WaxRubiks
2005-Mar-23, 05:47 PM
I thought all water molecules existed in their ionic state...
.

A Thousand Pardons
2005-Mar-23, 06:30 PM
And how ever small the difference, the molecules of water at the southern end of the bath are moving faster(west to east) than the molecules at the northern end. (edit- in the northern hemisphere anyway)

Hay presto, a democratically elected whirl pool!!!!!
The problem is, there are other effects that completely swamp that "how ever small difference"--intial rotation of the inflow, shape of the basin, tilt of the basin, minor distrubances, etc.

It's like that effect of the moon's tide on earthquakes--of course there is an effect, but it is so small, that it is just useless for predicting earthquakes.

WaxRubiks
2005-Mar-23, 06:37 PM
I wonder if the gyroscopic effect has anything to do with it?
After all the Earth is just a giant gyroscope and so I suppose is the water, if taken as a single unit!!!

Grey
2005-Mar-23, 07:06 PM
It's nice to see that the results of the poll are, in fact, about what we'd expect.

Disinfo Agent
2005-Mar-23, 07:58 PM
You've still got very few replies...

Grey
2005-Mar-23, 08:18 PM
It is a small data sample, true. I'll admit that I haven't taken thetime to test this on my own bathtub, so I haven't voted myself. I'll have to check.

I do understand that there are folks living in countries on the equator who will "demonstrate" this effect for tourists. They take a big basin filled with water, walk across the equator to the north side, pull out the stopper, and the water circles one way. Then they refill the basin, walk to the south side of the equator, and the water circles the other way, amazingly enough. Of course, what you didn't notice, since you only saw them do this once or twice, was that after crossing the equator they always carefully turn around to face you again in the correct direction to start the water rotating the way they'd like imperceptibly. That small bit of angular momentum is all it takes to have the water spiral in either direction, provided that the basin itself is pretty uniform.

WaxRubiks
2005-Mar-23, 09:11 PM
Even if this did work at the equator, local gravity differences would cause the line going around the world to we wiggly, i think.

A Thousand Pardons
2005-Mar-24, 05:51 PM
Even if this did work at the equator, local gravity differences would cause the line going around the world to we wiggly, i think.
Is that some sort of UTI? :)

Candy
2005-Mar-28, 11:45 AM
Another consideration is the plug removal. As the drain becomes unplugged, there may be a slight rotation established favoring one direction.
I just did the bathtub test. The plug is built-in. To drain the tub, I have to turn it counter-clockwise. The water drained counter-clockwise, too.

George
2005-Apr-07, 11:11 PM
Another consideration is the plug removal. As the drain becomes unplugged, there may be a slight rotation established favoring one direction.
I just did the bathtub test. The plug is built-in. To drain the tub, I have to turn it counter-clockwise. The water drained counter-clockwise, too.
Ah ha! (Sorry it took this long to see your comment.)

Does anyone remember the BA's book section discussing the fraud at the equator? AS he changes hemispheres, he turns the direction needed to initiate the desired rotation direction in the water.

WaxRubiks
2005-Apr-07, 11:17 PM
Another consideration is the plug removal. As the drain becomes unplugged, there may be a slight rotation established favoring one direction.
I just did the bathtub test. The plug is built-in. To drain the tub, I have to turn it counter-clockwise. The water drained counter-clockwise, too.
Ah ha! (Sorry it took this long to see your comment.)

Does anyone remember the BA's book section discussing the fraud at the equator? AS he changes hemispheres, he turns the direction needed to initiate the desired rotation direction in the water.

of course if you rotate the water one way then that is the way it will spin when it drains but that doesn't mean that if the water is perfectly still before it drains that it won't spin anti-clockwise in the northen hemisphere.....

George
2005-Apr-07, 11:45 PM
of course if you rotate the water one way then that is the way it will spin when it drains but that doesn't mean that if the water is perfectly still before it drains that it won't spin anti-clockwise in the northen hemisphere.....
True, but why. The direction is caused by some force. It is likely due to one, or more, of the following...

1) The water has a net rotation direction prior to draining.
2) The drain plug removal forces a rotation direction.
3) The drain itself creates a rotation due to the non-perfect plumbing.

I can't think of anything else. I am intentionally leaving out the differential spin rate due to Earth's rotation and any electromagnetic possibilites.

Grey
2005-Apr-08, 12:36 AM
1) The water has a net rotation direction prior to draining.
2) The drain plug removal forces a rotation direction.
3) The drain itself creates a rotation due to the non-perfect plumbing.

I can't think of anything else.
Those sound pretty good. I'd also add a lack of symmetry in the bathtub itself that might provide a preferential direction as the water drains.

WaxRubiks
2005-Apr-08, 01:13 AM
In the science museum in London there is a 30ft(guess) pendulum suspend from a high ceiling, it is free to swing anyway it wants but as the day goes by its swing changes direction, due to the rotation of the Earth(this is the point of the demonstration). So if a small weight can keep its momentum relative to the Earth's revolution then why couldn't the water in a bucket? The amount of energy in the water in a bucket treating it like a fly wheel is 0.0000....1 (I've for forgotten how many zeros) joules but it may be enough to tip the balance in a still bucket of water.
Once the water is spiraling the actual energy for the whirl pool comes from the falling of the water through the hole...

WaxRubiks
2005-Apr-08, 01:58 AM
I calculate that water in a sink has 0.0000000046 joules of water due to the rotation of the Earth and if that was concentrated into 1 cubic centimeter of water, then that cubic centimeter could travel at 1.5mm a second. Maybe enough to get the whirlpool show on the road. I'm not sure about the mechanism for turning the gravitational potential energy into kinetic energy(as the water falls through the hole) but this would have to be considered even when pre-swirling the water anyway.

George
2005-Apr-08, 12:36 PM
1) The water has a net rotation direction prior to draining.
2) The drain plug removal forces a rotation direction.
3) The drain itself creates a rotation due to the non-perfect plumbing.

I can't think of anything else.
Those sound pretty good. I'd also add a lack of symmetry in the bathtub itself that might provide a preferential direction as the water drains.

4) Asymmetric bathtub. :)

George
2005-Apr-08, 12:47 PM
In the science museum in London there is a 30ft(guess) pendulum suspend from a high ceiling, it is free to swing anyway it wants but as the day goes by its swing changes direction, due to the rotation of the Earth(this is the point of the demonstration). So if a small weight can keep its momentum relative to the Earth's revolution then why couldn't the water in a bucket?"
Is the pendulum in a vacuum? It is very difficult to make them work right due to air currents, swivel friction, etc. I know of a 30 or 40 footer that was abandoned.


Once the water is spiraling the actual energy for the whirl pool comes from the falling of the water through the hole...
Sounds right. It should take little to get one started, but once started it is self-supporting if it doesn't roam around.


I calculate that water in a sink has 0.0000000046 joules of water due to the rotation of the Earth and if that was concentrated into 1 cubic centimeter of water, then that cubic centimeter could travel at 1.5mm a second. Maybe enough to get the whirlpool show on the road. I'm not sure about the mechanism for turning the gravitational potential energy into kinetic energy(as the water falls through the hole) but this would have to be considered even when pre-swirling the water anyway.
Is the 1.5mm/sec the differential rate from one end of the tub to the other? In the area near the drain, I would expect less of a differential rate calculation.

WaxRubiks
2005-Apr-08, 06:53 PM
Is the 1.5mm/sec the differential rate from one end of the tub to the other? In the area near the drain, I would expect less of a differential rate calculation.

No, the 1.5mm/sec is just if the energy was concentrated into 1 cubic centimeter of water(it's quite a small amount of energy). But the actual volume of the water involved in the whirlpool is probably quite small, just a few mm in from the surface(at the start), I would have thought.
If (for example) one centimeter of water has gone down the plughole then all that angular momentum in that top layer will have had to have gone somewhere.

WaxRubiks
2005-Apr-08, 06:59 PM
ps. the pendulum(I just googled it and found that it is called a Faucult pendulum) in London is just in the open air IIRC.

CJSF
2005-Apr-08, 07:26 PM
My water drains down.

CJSF

George
2005-Apr-08, 11:35 PM
Across a 15cm diameter at the drain, I get about 2 mm per minute as the differential rate of rotation around the center of the earth. The idea the Coriolis effect causes drain rotation seems to...uh...go "down the drain". :)

WaxRubiks
2005-Apr-09, 12:05 AM
Surely, all things being equal, even a small rotation in a round container will lead to a whirlpool in the same direction, although not at or near the equator, that is just a con(although I used to believe it).

2005-Apr-09, 07:37 AM
I did this experiment with a sink at work...

I found that it drained in whichever way I stirred the water; I had to do that to overcome the swirling motion caused by the asymmetric position of the tap relative to the sink's c.o.g. At no point did it reverse so as to conform to the mythology! :lol: :lol: :lol:

WaxRubiks
2005-Apr-09, 08:06 AM
I did this experiment with a sink at work...

I found that it drained in whichever way I stirred the water; I had to do that to overcome the swirling motion caused by the asymmetric position of the tap relative to the sink's c.o.g. At no point did it reverse so as to conform to the mythology! :lol: :lol: :lol:

there is noway that the initial energy of the system could overcome the active swirling of the water, that would put far to much artificial energy into the system.

Active swirling doesn't disprove the phenomenon. You have to perform the experiment with still water in a round bucket with a hole in the middle. And not at the equator, where the water is revolving perpendicular to the plane of any resulting whirlpool. After all when they dropped objects of the tower of Pisa they didn't use a hammer and a feather.

Eroica
2005-Apr-09, 11:07 AM
ps. the pendulum(I just googled it and found that it is called a Faucult pendulum) in London is just in the open air IIRC.
Foucault Pendulum (http://scienceworld.wolfram.com/physics/FoucaultPendulum.html)

mickal555
2005-Apr-09, 01:06 PM
mine just goes straght down, until the end where a funnell opens.

George
2005-Apr-09, 06:45 PM
Pendulums are smple to make. However, good luck making it work.

Foucault discovered it by serendipity. He built one in a Paris church (the Pantheon). His was 67 meters tall. The higher the better.

There appears to be one working at the University of Sydney... here (http://www.abc.net.au/surf/pendulum/). I saw another site showing it working in 1999. It would be interesting to know how many are actually operatonal.

It demonstrates inertia from which shows the rotation of the Earth. You can accurately calculate g from these and the rotation rate of the Earth. It does not demonstrate the Coriolis effect.


Across a 15cm diameter at the drain, I get about 2 mm per minute as the differential rate of rotation around the center of the earth.
:oops: . I missed it horribly. I believe it is 1e-15 mm/hr. (10 cm diameter). This is at the equator. (2xpi/24)x(1- cos(arctan(.333/(4000x5280)))) ft/hr.

WaxRubiks
2005-Apr-09, 06:58 PM
I don't know if the Coriolis effect is the same as treating the water in a bowl of water as a flywheel?

The effect should be greatest at either of the poles and nonexistant at the equator.

I remember hearing a saying once, "a penny a year profit=happiness, a penny a year loss=misery", surely any amount of rotation in one direction(in a still bowel of water) will cause the whirl pool to opt for the same direction(anticlockwise in the northern hemisphere).

The shape of a bath or sink shouldn't matter as long as the container is symmetrical.

Grey
2005-Apr-09, 10:56 PM
...surely any amount of rotation in one direction(in a still bowl of water) will cause the whirl pool to opt for the same direction(anticlockwise in the northern hemisphere).
Here's the issue. No bowl of water is entirely still, there will always be some random motion or residual motion from filling the bowl. Moreover, there may be asymmetrical effects from the way the drain is configured or other such issues. If the Coriolis effect is sufficiently small (which it is for a small container of water), it will be overwhelmed by these effects, so there won't be a preferential direction based on hemisphere. As you can see by the (admittedly small) poll sample here.

George
2005-Apr-10, 02:32 AM
The effect should be greatest at either of the poles and nonexistant at the equator.

Quite true. At 60 deg lattitude, the differential rate across 4 inches is about 1 inch per hour (hopefully my rushed math is right). Significantly higher, yet still insifnificant in it's effect on the rotation direction and rate.

jnik
2005-Apr-11, 03:31 PM
Down. Very slowly. I need to clean the drain...

(Northern Hemisphere, 40-mumble degrees)

Eroica
2005-Apr-11, 04:33 PM
I wonder has anyone tried the same bathtub in each hemisphere! If the water drained the same way both times, Coriolis's goose would be well and truly cooked.

Australian Custom Officer: Anything to declare, sir?
Eroica: Er, just a bathtub ... oh, and my genius! :D

Candy
2005-Apr-11, 04:41 PM
I wonder has anyone tried the same bathtub in each hemisphere! If the water drained the same way both times, Coriolis's goose would be well and truly cooked.

Australian Custom Officer: Anything to declare, sir?
Eroica: Er, just a bathtub ... oh, and my genius! :D
I can ship a bathtub via company mail (on United only) from ORD to an airport we fly into (must be a true United flight). :D

George
2005-Apr-11, 04:45 PM
I wonder has anyone tried the same bathtub in each hemisphere! If the water drained the same way both times, Coriolis's goose would be well and truly cooked.

Australian Custom Officer: Anything to declare, sir?
Eroica: Er, just a bathtub ... oh, and my genius! :D

Take the kitchen sink instead. :)

How 'bout using a round bucket, install a drain/plug and using a large hose to simulate the pipe works. Try different hose arrangements to see what influence this has on the rotation direction.

Candy
2005-Apr-11, 10:51 PM
http://www.cosgan.de/images/smilie/ekelig/c020.gif

Counter-Clockwise

jkmccrann
2005-Oct-22, 08:04 AM
Clockwise down here.

Tanalia
2005-Nov-13, 10:03 AM
I thought all water molecules existed in their ionic state...
.

Not all, but some. Water molecules may dissociate into separate ions (hydrogen [H+] and hydroxyl [OH-]), but, since they are oppositely charged, they tend to recombine fairly rapidly.



The effect by a magnetic field is deflection in different directions for the opposite ions you talk about in the OP--since the charge below even the macro level is essentially neutral, the effect should be minimal or even non-existent, shouldn't it?
If you say so, but the hydroxyl ions are 33 times as massive as the hydrogen ions. Would that make a difference?

Only 17 times as massive, but no. The force experienced due to the magnetic field is proportional to the charge, so it would be equal (though in opposite directions). This force would indeed accelerate the hydrogen ions faster than the hydroxyl, but the resulting momentum of each would be the same.


Details for any other lurking geeks ;) :

pH is a measure of average hydrogen ion concentration of a solution. Pure water is pH 7, meaning 1.0e-7 mole of [H+] per liter, so a rather small fraction of the water is ionized at any moment.
Acids have a higher concentration of hydrogen ions, directly provided by the acidic substance (stomach acid contains hydrogen chloride, HCl, in solution called hydrochloric acid, directly providing more [H+] -- stomach acid is often around pH 2, or 1.0e-2 M/l, a significantly higher concentration that pure water, though still a small fraction of the total solution).
Alkaline solutions, on the other hand, provide more [OH-] which tend to bind with the free [H+] from the water, so fewer are available at any given time. The lower concentration is represented by a higher pH value (just as the higher concentration for the acid is a lower value).
Most people learn that the pH scale runs from 0 (very acid) to 14 (very alkaline), an this is true for most substances people will encounter, but it is quite possible to exceed these limits -- an extremely strong acid could have a negatove pH.

An acid would not be affected any differently by the magnetic field than water; although it has more [H+] than the water, the excess is balanced by the other component of the acid, [Cl-] in the case of hydrochloric acid.

boppa
2005-Dec-26, 02:56 PM
interesting
i got 2 bathtubs,4 hand sinks,2 kitchen sinks and 2 laundry tubs

even just in my house i got an equal split-even to the tub types

ie 1 bath goes one way,one goes the other..
2 hand sinks go one way,2 the other..

and im `pretty sure' im not on the equator too

methinks local geometry of the sink/tub/etc is the deciding factor



(but its cool that im mr average in person tho..)
;-)

HenrikOlsen
2005-Dec-26, 03:10 PM
The poll lacks a couple of possibilities, one of which (the one in my bathtub), is that it depends on how I got out of it.

NASA Fan
2006-Sep-12, 04:40 PM
I know that it has been 9 months since the last post, but I thought that I would share my observation.

I filled my bathtub with about 6 inches of water, and turned the plug (I can't pull it out), and I could not see any direction to the water flowing out...even when I stirred the water clockwise, or counter clockwise.

So my vote would have to be straight down.

hhEb09'1
2006-Sep-12, 04:51 PM
So my vote would have to be straight down.We're going to have to throw out your datapoint as an outliar :)

Argos
2006-Sep-12, 05:16 PM
What about your bathtub? Sinks are smaller, so the effect might not be the same.

Ok, I did it to my pool, just to find out that it drains... Right downwards (because it is forced by a pump). You owe me 50,000 litres of water.:mad:

NASA Fan
2006-Sep-14, 11:06 PM
Who Me? I did not say that it was not possible for it to go straight down.

I'll tell you what, I will send you a bottle of water, then you only have to get 49,999.5 more liters of water. If you ask nicely, maybe one or two other poster will be kind and send a bottle.

Argos
2006-Sep-15, 01:10 PM
It wasn´t directed to you, but since you´ve asked, I prefer Evian, please...

;)

jimbo
2006-Sep-16, 10:50 PM
always i have noticed the water going anti clockwise.until the other morning when it went clockwise.the only reason i can think that it went that way is that the drains were partialy blocked.or perhaps it was my hangover making the room spin.

clop
2006-Sep-16, 11:05 PM
You're going to have to normalise the data because more people living in the northern hemisphere than in the southern hemisphere have responded.

I think (not being very good at statistics) that this means you have to divide the number of northern hemisphere votes in each category by the total number of northern hemisphere votes and divide the number of southern hemisphere votes in each category by the total number of southern hemisphere votes. Only then will you see if there is a relationship or not.

I'm in the southern hemisphere but rarely take a bath (we're very conscious of using water here in the driest state of the driest continent) so I'm sorry that I can't vote in your poll.

clop

grant hutchison
2006-Sep-17, 06:59 PM
I do understand that there are folks living in countries on the equator who will "demonstrate" this effect for tourists. They take a big basin filled with water, walk across the equator to the north side, pull out the stopper, and the water circles one way. Then they refill the basin, walk to the south side of the equator, and the water circles the other way, amazingly enough. Of course, what you didn't notice, since you only saw them do this once or twice, was that after crossing the equator they always carefully turn around to face you again in the correct direction to start the water rotating the way they'd like imperceptibly.The Kenyan demonstration of this which featured on Michael Palin's Pole to Pole TV series was particularly good, since the demonstrator got the expected directions of drainage wrong in his preamble, but in his subsequent demonstration the directions of rotation turned out to be just as he had (wrongly) predicted.
A very nice demonstration that other forces must predominate over Coriolis, and that they appear to be under the control of the demonstrator.

But there's a static demonstration set up beside an equator monument in Uganda, which doesn't allow for the "turn the bucket" trick to be used.
But the containers used are wide, flat dishes, and each of them has a spiral painted on its inside surface in thick white paint, indicating the predicted direction of rotation. Presumably this influences radial flow enough to set up the appropriate drainage spiral.

Grant Hutchison

jimbo
2006-Sep-18, 06:27 PM
how about this ,when the room spins when you have had too much to drink is the direction affected by which hemisphere you are on?

greatgreekcollector
2008-Aug-26, 05:57 AM
My bathtub drains straight down. ;)

Occam
2008-Sep-01, 12:37 AM
I think the most significant result of this poll, is that there are apparently more people with bathtubs in the Northern hemisphere, than the Southern.

chrissy
2008-Nov-17, 10:13 PM
Mine goes counter clock wise even my kitchen sink.