More rotating toilet bowl insanity

[rsk]

CW or CCW?
It all depends if the clock is facing up, or facing down.
Most people look at the rotation as if a top view is the most natural perspective, but a bottoms up view is just as valid.
Even the videos from the science guys ( Get Smarter and V... ), at least I did not notice, do not state their reference perspective.

Yes. I'd have liked to see it from underneath, but couldn't work out how.

 

[sophiecentaur]

but a bottoms up view is just as valid.

Valid but not intuitive. I always need to look twice at my Planisphere, just to make sure of where to find things in the night sky. That's the only example that I come across of the upside down world. Looking upwards at the vortex in my bath drain would upset the flow and require me to hold my breath a long time.

 

[bland]

It's not true to say that you cannot test this yourself. I remember as child over 50 years ago watching the water spiral down the bathtub drain and forcing it to spiral in the opposite direction by swirling it by hand, then gradually it closed up and resumed it's normal direction. I did not need a giant wading pool to see this.

 

[256bits]

Valid but not intuitive. I always need to look twice at my Planisphere, just to make sure of where to find things in the night sky. That's the only example that I come across of the upside down world. Looking upwards at the vortex in my bath drain would upset the flow and require me to hold my breath a long time.

Like @rsk stated also, it is difficult to visualize.
We look at hurricanes from a satellite view and for the NH they are spinning CCW - no argument there from anyone. ( anyone ? )
But tornadoes we look at from the side and up, and yet most of us, if not all, would still say the spin is CCW for the NH ( a few do spin the other way ).
I base my conclusions on at least 3 data points - you, me and rsk.

 

[sophiecentaur]

It's not true to say that you cannot test this yourself. I remember as child over 50 years ago watching the water spiral down the bathtub drain and forcing it to spiral in the opposite direction by swirling it by hand, then gradually it closed up and resumed it's normal direction. I did not need a giant wading pool to see this.

But what were you testing? You had just one bath tub in one location. That's not the basis for a proper verification of any rule - just the opportunity for a nice relaxing bath. But kids don't know about those.
I could build you a bath that would behave in exactly the opposite way in the same position and I doubt you would spot the difference (certainly not the 'you' of 50 years ago). If you can accept the calculation for the Coriolis Force for the sort of water movements in a bath then that tells you the force is way too small to be relevant. If y ou find it hard to accept that sort of calculation then why do have faith that the computer you are using will work and get your message back to me? The calculations used in making that system are way more complicated.

 

[bland]

But what were you testing?

That water spirals down a drain in opposite directions in the northern and southern hemisphere was a well spoken about 'phenomenon' as far back as I can remember. I'm not saying it's a fact as if it is not a fact and this is upheld by proper science then I'm of course fully prepared to accept that. If it's taken this long to be debunked then I'm even more amazed. However to answer your question I was testing if I could force it to reverse and what would happen. And in fact what happened always was what I mentioned. If this is some phenomenon caused by the drain itself, then I'm happy to accept that too!. That's all I'm saying.

So from what I now gather, the direction it spirals is either a product of the drain design or in the case of the two huge pools of water, just a coincidence that they swirled in opposite directions. As the two pools appear to by symmetrical with merely a small hole for a drain, am I to understand that if they were both repeated say 50 times each that we'd find the resultant vortex direction to be of equivalent probability as tossing a coin?

 

[sophiecentaur]

If it's taken this long to be debunked then I'm even more amazed.

It hasn't taken "all this time". When I was at Uni, (pre-history) the discussion was rife and the sums were done. They showed (as they always would) that the forces involved are too small to be significant.
Fact is, it's just one of those things which have the same appeal as conspiracy theories and they keep being brought up. People love magic. Proper Science is not easy or attractive enough.

 

[Herman Trivilino]

Any news on those stats? How significant were they?

No. Sorry it took me so long to respond. I tracked down the passage I read, it's on page 133 of Teaching Introductory Physics by Clifford E. Swartz and Thomas Miner, AIP Press, 1997. There's no specific reference given for the passage, but there are three references at the chapter end.

These authors simply state that the rotation was "generally counterclockwise in Boston" and that in Australia "the drainage there was clockwise".

They also do a calculation where they estimate the Coriolis acceleration to be about $7 \times 10^{-6} g$.

 

[256bits]

So from what I now gather, the direction it spirals is either a product of the drain design or in the case of the two huge pools of water, just a coincidence that they swirled in opposite directions. As the two pools appear to by symmetrical with merely a small hole for a drain, am I to understand that if they were both repeated say 50 times each that we'd find the resultant vortex direction to be of equivalent probability as tossing a coin?

If you are referring to the two tubs from Getting Smarter Everyday and V..., the experiment was a copy of that done by Shapiro ( 1962 ) and colleagues.
In a very controlled experiment, with temperature effects, surface air motion, filling motion, ... eliminated, it appeared that the 1962 experiments did show the rotation of the Earth did have an affect upon draining water. Same as what @Mister T had written about. And that the rotation rate of the vortex measured with a floating crosshair was consistent with that due to the Coriolis affect. If the tubs and setup in the videos were of the same caliber as that, then a similar affect should be noted. I do not think anyone has ever come out claiming Shapiro's setup and results were faked, inconsistent, inconclusive, ..., but that they are a show of micro forces on water movement.

In an uncontrolled experiment, such as with a bathtub, sink, the Coriolis force is overwhelmed by other factors. Toilets usually have directed flow when flushed and the swirl will always be in one direction everytime. Bathtubs and sinks may or not have a 50 % of swirl in either direction, perhaps due to leveling, drainage hole, induced swirl, etc.

At the equator, 50% chance of direction or no vortex at all.
If one, refers to the video in post # 1, you can if you want, travel to that location and for a $ or $$, whatever they charge, ask for a demonstration from an ingenious entrepreneur - fascinating for a street exhibit it would seem, at least he is demonstrating as aspect of science.

What does Straight Dope have to say about Shaprio.
https://www.straightdope.com/column...-counterclockwise-in-the-northern-hemisphere/
You can find the original paper in Nature, still under copyright access.
https://www.nature.com/articles/1961080b0
a better description,
https://www.technologyreview.com/s/429479/verifying-a-vortex/

 

[DaveC426913]

It goes without saying that a sufficiently large mass will be affected by Coriolis (because, storms), so the 1962 study is certainly corroborating that. (which unfortunately will only add fuel to the myth.)

But the urban legend deals with toilet bowls and sinks. I'd prefer to see the experiment done on that scale to make an iron clad pronouncement of debunkage.

[EDIT] Ah. I see your last link has done that.

"For the first 12 to 15 minutes, the float remained motionless. Then it began to rotate almost imperceptibly, counterclockwise, reaching a peak speed of approximately one revolution every three to four seconds.

Proving that the Coriolis effect can be detected in a bathtub-size tank, albeit under carefully controlled conditions, was a remarkable achievement. At MIT’s latitude of 42°, the effect was “only thirty-millionths that of gravity, which is so small that it will be overcome by filling and even temperature differences and water impurities,” reported one of many newspapers and periodicals covering the experiment. "

(Strange, it never actually says what size the container is in his experiment)

 

[rootone]

The answer seems to be that once a vortex is established one way or the other, it becomes self sustaining in either hemisphere.
Coriolis is one of several factors involved in starting the spin, and it does bias things depending on latitude.
We never see clockwise cyclones (or lesser low pressure weather systems) in the northern hemisphere though. they always anticlockwise,

 

[DaveC426913]

The answer seems to be that once a vortex is established one way or the other, it becomes self sustaining in either hemisphere.

Yes, but the myth contends that it is statistically much more likely to get established in the direction of Coriolis Force. (Actually, that's being generous - the myth contains that it always does, but I'll put that down to hyperbole.)

 

[rootone]

It's not true to say that you cannot test this yourself. I remember as child over 50 years ago watching the water spiral down the bathtub drain and forcing it to spiral in the opposite direction by swirling it by hand, then gradually it closed up and resumed it's normal direction. I did not need a giant wading pool to see this.

Strangely though and as I mentioned earlier I did this same kid experiment and got a different result!
Once the vortex is up and running it stays that way unless you mess with it again to turn it around,

 

[DaveC426913]

It's not true to say that you cannot test this yourself. I remember as child over 50 years ago watching the water spiral down the bathtub drain and forcing it to spiral in the opposite direction by swirling it by hand, then gradually it closed up and resumed it's normal direction. I did not need a giant wading pool to see this.

But that's not a valid test. There are a host of confounding factors that need to be eliminated.

Doing the test on only one tub is as problematic as performing the test only once.

For all you know, every other bathtub on your block might drain in the opposite direction from yours.

 

[bland]

But that's not a valid test. There are a host of confounding factors that need to be eliminated.

Doing the test on only one tub is as problematic as performing the test only once.

For all you know, every other bathtub on your block might drain in the opposite direction from yours.

All this is true, however I still have to give myself some plaudits for attempting a scientific if ultimately flawed experiment as a child! And while I accept that this has been debunked long ago, the falsity of this early spinning hypothesis has not yet entered the general consciousness. Much like the equally false explanations for the tides! Both of these these are such popular misconceptions I am surprised that they have not during the past 50 years been corrected in the popular consciousness.

The answer seems to be that once a vortex is established one way or the other, it becomes self sustaining in either hemisphere.

Well there you go. I found the opposite, it did become self sustaining at first but *always* (for me at least) gradually blocked up and then reversed! I guess I'll have to put it down to the magical southern hemisphere bath elfs.

 

[DaveC426913]

I still have to give myself some plaudits for attempting a scientific if ultimately flawed experiment as a child!

And plaudits from me too. That was kind of oblivious of me.

 

[sophiecentaur]

The title of the thread reflects the popular view on what will happen. The results of the most carefully done experiment showed that results can be the same as the large scale effects with weather systems. This can hardly be too surprising because the sums predict a Coriolis Force and classical Physics is not likely suddenly to change its mind as the scale decreases. What we are (should be) discussing is a signal to noise problem and when the noise is reduced sufficiently and the signal is raised enough, we detect the effect.
The 'noise' associated with domestic sanitary ware is too high.

 

[DrGreg]

The noise associated with domestic sanitary ware is too high.

This deserves to be taken out of context and be the quote of the week!

 

[DaveC426913]

The title of the thread reflects the popular view on what will happen. The results of the most carefully done experiment showed that results can be the same as the large scale effects with weather systems. This can hardly be too surprising because the sums predict a Coriolis Force and classical Physics is not likely suddenly to change its mind as the scale decreases. What we are (should be) discussing is a signal to noise problem and when the noise is reduced sufficiently and the signal is raised enough, we detect the effect.
The 'noise' associated with domestic sanitary ware is too high.

Agree. But laypeople, who promote the trash in the OP, are interested in results. They're not going to care about what 'wouldn't' or 'shouldn't' happen; I want to hit them with 'here is the empirical evidence, now shuddup'.

 

[sophiecentaur]

Agree. But laypeople, who promote the trash in the OP, are interested in results. They're not going to care about what 'wouldn't' or 'shouldn't' happen; I want to hit them with 'here is the empirical evidence, now shuddup'.

I sympathise with you but what could you tell them about Quantum Physics or Relativity that would fit that requirement? I think "Correct but probably too small to measure accurately in your bathroom" should do.

 

[DaveC426913]

I sympathise with you but what could you tell them about Quantum Physics or Relativity that would fit that requirement? I think "Correct but probably too small to measure accurately in your bathroom" should do.

To which the inevitable retort is: "So you admit it is true!"

 

[sophiecentaur]

Which one of us is the devil and which one is the advocate here?
There is nothing to admit. The sums correctly predict that it works (mostly) in the case of weather systems but, even then, only when the conditions are right. If it were always true, everyone would be in a permanent cyclone / depression and that is not topologically possible. In fact, the situation in the atmosphere never produces the sort of conditions for a true bathtub effect because they are always triggered by linear motion of air masses and rising / falling air. It is also possible to get air moving the wrong way. I foundhttp://www.kdlt.com/2015/04/09/do-all-tornadoes-rotate-the-same-way/and several others, which tells us that clockwise tornados can sometimes form in the northern hemisphere, going against the coriolis effect even at that scale.
I'm sorry Dave (to coin a phrase) but I think it's all just too hard to present to your dumkopf lay friends in a cut and dried assertion. You and I, of course, are fine with it all.