[Guest]

You made a journey to a country that acrosses the equator. You wonder where the equator exactly passes. Is there a method to find the line of equator without using any technical instrument, sun, moon, stars and any other geographical signs?

[Guest]

"]with just a bowl of water and a piece of tissue paper and a needle it is possible. no crafty tools needed.

[Guest]

"]with just a bowl of water and a piece of tissue paper and a needle it is possible. no crafty tools needed.

You've pointed some tools but didn't mentioned about how to use them. Please inform us.

[Guest]

Just a hunch

If I magnetise the needle it will normaly align itself along the north/south line of the earths magnetic field and as such makes a good rudimentary compass. This can be done with a regular magnet stroked along the length of the needle (is there another way?). Now this in itself is of no use, but will the needle be attracted to the north pole when i am north of the equator and South when I am south of the equator? When it stays in the middle of the bowl I would be on the equator.

I am thinking this may be stretching the strength of the earths magnetic field just a bit too much?

David

Edited January 12, 2009 by dehusky

[Guest]

Just a hunch

If I magnetise the needle it will normaly align itself along the north/south line of the earths magnetic field and as such makes a good rudimentary compass. This can be done with a regular magnet stroked along the length of the needle (is there another way?). Now this in itself is of no use, but will the needle be attracted to the north pole when i am north of the equator and South when I am south of the equator? When it stays in the middle of the bowl I would be on the equator.

I am thinking this may be stretching the strength of the earths magnetic field just a bit too much?

David

Are you sure that a magnetic needle will attracted to north if you're in north hemisphere, and to south if you're in south hemisphere ?. If this is true, then the compasses sold in eather hemispheres should be just opposite. Though, I may have missed what you intended.

[Guest]

also if you have two bottles and fill one with half amount of water then seal them together so they are waterproof then tip the bottles up so the water falls down the water will spin in dofferent directions on either side of the equator so on the northen side it will go clockwise and on the southern side it will go anti-clockwise.

no major tools needed.

[Guest]

also if you have two bottles and fill one with half amount of water then seal them together so they are waterproof then tip the bottles up so the water falls down the water will spin in dofferent directions on either side of the equator so on the northen side it will go clockwise and on the southern side it will go anti-clockwise.

no major tools needed.

Yes, this is the answer.

It may come incredible to someone who faces with this first, but in a serious tv program, it was demonstrated that even a 1 meter away from equator line changes the direction of spinning.

Now the question is that:

What is the reason of it?

[Guest]

Yes, this is the answer.

It may come incredible to someone who faces with this first, but in a serious tv program, it was demonstrated that even a 1 meter away from equator line changes the direction of spinning.

Now the question is that:

What is the reason of it?

This is actually a common urban myth. The reason why it should do this is because of the Coriolis effect, but the Coriolis effect is so minimal when talking about water in toilets, sinks, etc. that it can spin in either direction depending on how the water is entered or imperfections, as these have a much more significant impact.

Read http://en.wikipedia.org/wiki/Coriolis_effect (under "Corrections to common misconceptions about the Coriolis effect") or, if you don't believe in Wikipedia as anyone can edit it, just google it (e.g. "water spinning myth" or something similar) and you will find lots of references to the fact it is a myth.

[Guest]

This is actually a common urban myth. The reason why it should do this is because of the Coriolis effect, but the Coriolis effect is so minimal when talking about water in toilets, sinks, etc. that it can spin in either direction depending on how the water is entered or imperfections, as these have a much more significant impact.

Read http://en.wikipedia.org/wiki/Coriolis_effect (under "Corrections to common misconceptions about the Coriolis effect") or, if you don't believe in Wikipedia as anyone can edit it, just google it (e.g. "water spinning myth" or something similar) and you will find lots of references to the fact it is a myth.

I glanced at your link but found it hard to examine, I'm a lazy man.

Years ago I had investigated about this spinning myth, and had found a simple and reasonable answer:

If you have a bucket filled with water, and if you drill a hole at the base of it, water will spill out by spinning.

Assume you're in north hemisphere, the edges of bucket are actually in motion, even you don't see it. (Because of the motion of earth). The northern edge of bucket is in motion slower than the southern edge of it. Of course the water close to these edges are at different speeds. Thus the spinning is takes place so that faster water will move more than slower water.

This seemed me reasonable???

[Guest]

I glanced at your link but found it hard to examine, I'm a lazy man.

Years ago I had investigated about this spinning myth, and had found a simple and reasonable answer:

If you have a bucket filled with water, and if you drill a hole at the base of it, water will spill out by spinning.

Assume you're in north hemisphere, the edges of bucket are actually in motion, even you don't see it. (Because of the motion of earth). The northern edge of bucket is in motion slower than the southern edge of it. Of course the water close to these edges are at different speeds. Thus the spinning is takes place so that faster water will move more than slower water.

This seemed me reasonable???

Here's a link to that section and the issue we are talking about is the first two paragraphs of that section.

Your reasoning is absolutely correct. However, at the surface of the earth, the forces applied to the water due to this effect are relatively small. In the example you have given, the drill bit would have had a greater impact on creating a spinning motion and what direction it will spin in, even just for the split second when you have broken through the bottom of the bucket. Then, imperfections in the hole, etc. will also have an impact.

So basically your reasoning is absolutely correct and, if this were a mathematical model (where everything is perfect, there are no imperfections and no outside influences) you would observe the spinning change direction. However, in the real world things aren't perfect, so you wouldn't be able to predict it.

[Guest]

Here's a link to that section and the issue we are talking about is the first two paragraphs of that section.

Your reasoning is absolutely correct. However, at the surface of the earth, the forces applied to the water due to this effect are relatively small. In the example you have given, the drill bit would have had a greater impact on creating a spinning motion and what direction it will spin in, even just for the split second when you have broken through the bottom of the bucket. Then, imperfections in the hole, etc. will also have an impact.

So basically your reasoning is absolutely correct and, if this were a mathematical model (where everything is perfect, there are no imperfections and no outside influences) you would observe the spinning change direction. However, in the real world things aren't perfect, so you wouldn't be able to predict it.

Paradigms shattered!

Guess I can cancel that trip to Austrailia now... the mystique is gone

[Guest]

Paradigms shattered!

Guess I can cancel that trip to Austrailia now... the mystique is gone

Well, I'm in Brazil, already been there in the line of the equator and tried this water thing. No, it does not work

[Guest]

And the compass here also point to the north.

[Guest]

And the compass here also point to the north.

wow that is odd. And you are so near the tropic of capricorn too! Why is that?

[Guest]

wow that is odd. And you are so near the tropic of capricorn too! Why is that?

The compass always points to the north because of the orientation of the earth's magnet field. Of course, the compass do not point to the geographic north. It points to the magnetic pole. Most of the good compass have a way to adjust the declination, so that you can add or subtract the corresponding amount of degree to the compass, so that you can see an use it like it was point to the geographic north. That amount of degrees is determined by world magnetic maps, yearly published because magnetic field is not constant.

Everything I just said here its a hint for the puzzle I'm trying to create and soon I'll publish here in Braiden

[Guest]

The compass always points to the north because of the orientation of the earth's magnet field. Of course, the compass do not point to the geographic north. It points to the magnetic pole. Most of the good compass have a way to adjust the declination, so that you can add or subtract the corresponding amount of degree to the compass, so that you can see an use it like it was point to the geographic north. That amount of degrees is determined by world magnetic maps, yearly published because magnetic field is not constant.

Everything I just said here its a hint for the puzzle I'm trying to create and soon I'll publish here in Braiden

Hey! Another Brazillian in the Den!

Welcome!

[Guest]

Are you sure that a magnetic needle will attracted to north if you're in north hemisphere, and to south if you're in south hemisphere ?. If this is true, then the compasses sold in eather hemispheres should be just opposite. Though, I may have missed what you intended.

Hi,

The north of the needle will always point north.

My theory is that in the northern hemishpere the needle will be attracted towards the north pole with a slightly greater force than the southern end being attracted to the south pole and visa versa.

[Guest]

I hope you will all pardon the rant, but this whole business of coriolis, hemispheres and toilets flushing is a personal peeve of mine. I know some very intelligent people, who ought to know better, and yet still cling to this wholly unfounded belief.

[soapbox]

To begin, the coriolis force acts on objects that are moving toward or away from a center of rotation. Because toilets, even in Australia, are generally mounted to something quite solid and stationary, they are not moving relative to Earth's axis, not even by a tiny amount that one might argue is negligible. There is therefore absolutely, incontestably, undeniably, and unquestionably no coriolis effect on water draining from a toilet bowl, bucket, bottle of JD, or the Hoover dam. And before anybody asks about flushing the toilet on a train, airplane, or bus, ponder it for a while, and you will realize that even when a coriolis force exists, there is no reason for it to cause any fluid rotation.

[/soapbox]

If you have a bucket filled with water, and if you drill a hole at the base of it, water will spill out by spinning.

Assume you're in north hemisphere, the edges of bucket are actually in motion, even you don't see it. (Because of the motion of earth). The northern edge of bucket is in motion slower than the southern edge of it. Of course the water close to these edges are at different speeds. Thus the spinning is takes place so that faster water will move more than slower water.

The bucket has the same angular velocity as its contents. There is therefore no reason for the water to start spinning, relative to the bucket, simply because a hole has appeared in the bottom.

There is a perfectly rational explanation for the vortex that may form in your bathtub drain, and it does not require us to account for, or have knowledge of celestial motions. It also requires no prior angular motion of the fluid -- i.e. it occurs, as predicted, in a fluid that is initially perfectly stationary.

When you get out of your nice warm bath, the pressure at the free surface of the water is constant (and equal to the local atmospheric pressure). Below the surface, the pressure is higher, and increases the deeper down you go (hydrostatic pressure). The pressure in your drainpipe might be slightly above or below atmospheric pressure, but it is definitely lower than the pressure at the bottom of your full tub (or it wouldn't drain). So, when you pull the plug, you have an imbalance between what the hydrostatics say the pressure ought to be (something higher than atmospheric) and what the drainpipe says it ought to be (essentially atmospheric).

One way this can be resolved, when there is a (relatively) high suction at the drain, is for the free surface of the water to "sink" down toward the drain, to a point where it can find equilibrium. But, how do we create a free surface that is not normal to the gravitational vector? Our friend Bernoulli^* can help us, but only to a limited extent. Enter vorticity, and its radial pressure gradient, to the rescue. Just like solids, a "blob" of fluid will only go around in a circle if a force is pushing it toward the center of rotation. Therefore the pressure must be lower in the center, and increase as you move radially away. Fortunately for our bathtub, that is precisely the type of imbalance we are trying to resolve.

How the fluid begins to rotate is a much more complicated phenomenon, and I won't attempt an explanation here. Suffice it to say that once a sufficiently large disturbance has got things started in one direction, it very quickly becomes self-sustaining. You can predict reasonably accurately the magnitude of vorticity (i.e. the distribution of angular velocity). However, if the water is initially completely still, there is no way of predicting the direction of the vortex, regardless of which hemisphere you live in.

*Speaking of Bernoulli, that reminds me of another peeve, which I'll save for another day...

Edited: typo.

Edited January 13, 2009 by d3k3

[Prof. Templeton]

I'm sure the coriolis force must be quite great. Whenever I'm playing billiards the balls never go straight. I can't only figure this must be due to the earth spinning. Then again, maybe I'm just not that good at billiards.

[Guest]

I think the proof is trying to tell you something - but he never has "crossed the line."!

[Prof. Templeton]

I think the proof is trying to tell you something - but he never has "crossed the line."!

Oh, Yes! I remember when I first became a "Shellback". It was on an expedition to Hiva Oa when our ship crossed over the equator. Back in those days ships had no GPS so the only way to tell you were crossing the equator was to look for the red line floating on the surface of the water, or if at night you had to go flush the toilet every few minutes. Constantly trapsing off to the head was a big pain, but better then being beaten with a wet hose.