Coriolis effect in baths and sinks.....

[Pikey P]

Fact or fiction.??

A mate of mine told me today that the position of you in the world (northern / southern hemmisphere)has no effect on the direction of the draining flow of water.

I have done some research (on wiki) and it seems that he was right. Why are we lead to believe different?

Lord Pikey

[mat205125]

I see you've played knifey spoony before

[robinhood21]

I knew it, that LHC has started to play tricks with the world already! Hold on everyone, the world is about to go into meltdown.

[GreenV8S]

It's fact, but the effect is so weak that it is almost impossible to measure unless you are very close to one of the poles. Which way the water spirals is very sensitive to the slightest disturbance in the water at the start and this will completely overwhelm the coriolis effect. The further away from the pole you get the weaker the effect is. If you ever see somebody 'proving' it works at the equator they're fooling themselves, or you, because the effect at the equator is zero.

[grumbledoak]

I don't believe your mate is right. But in a sink the effect is rather small, so you can make the water turn in either direction, in either hemisphere, if you swirl it. As far as I know, hurricanes and cyclones do naturally spin in opposite directions.

[Pigeon]

It's because people are ste observers.

Tell them that it always goes down the same way and they believe it to the extent of trying to come up with bks scientific explanations for it, when all they need to do is actually look at water going down plugholes and see that it does not in fact have a preferred direction of swirl, it goes either way, and indeed it is not uncommon for it to stop part way through and then start swirling the other way.

[ih8thisname]

Can anyone give me a simplified definition of whatever the hell this Coriolis Effect is? I was under the impression it was something to do with the curvature of the earth??

The Wikipedia description doesn't really make much sense at all to me!

[dilbert]

Get a bit of paper, and put it on the table in front of you.
Get a pen, and place it on the paper.
Push the pen forward, whilst moving the paper to the side.
That's the thing.

[Tpfkalm]

Water keeps flowing within itself for hours after being poured.

I was looking forward to seeing the water go down the plughole "the wrong way" in Australia and I was sad it didn't. It is ambiguous

[MK4 Slowride]

In the X-files Moulder found a sink somewhere that the magnetics were all messed up and it went both ways with a wobble.

Which was nice.

[grumbledoak]

Easy! The North and the South hemispheres spin in opposite directions (you really don't want to put one foot either side of the equator).


In truth, they sort of do, as one is upside down. At the surface the land has a tendency to 'drag' the air. Though it is only a small effect, it is enough for tropical storms to rotate in opposite directions in the two hemispheres. Even something as small as the water going down the plug-hole in your sink is subject to the same effect - try it for yourself, though don't expect it to be 100%.

[s2art]

ih8thisname said:

Can anyone give me a simplified definition of whatever the hell this Coriolis Effect is? I was under the impression it was something to do with the curvature of the earth??

The Wikipedia description doesn't really make much sense at all to me!

Things (air, water, whatever) want to travel in straight lines (Newtons laws). Unfortunately the Earth is spinning around. So to conserve momentum they will seem to move in a curve. (depending on what the direction is relative to the spin)

[AlVal]

Tpfkalm said:

I was looking forward to seeing the water go down the plughole "the wrong way" in Australia and I was sad it didn't.

talk about a ruined trip. glad I didnt use your travel itinerary

[schmokin1]

ih8thisname said:

Can anyone give me a simplified definition of whatever the hell this Coriolis Effect is? I was under the impression it was something to do with the curvature of the earth??

The Wikipedia description doesn't really make much sense at all to me!

imagine looking at the side of the earth, which is spinning on its axis, one revolution per day, west to east. on the equator you would be moving round in space faster than at the poles, because you are further away from the axis, but still spinning at one revolution per day. there is a drag effect on water molecules as eg. the further north the slower they move through space compared to their neighbour molecule that is to the south. therefore there is a curling away dragging effect from the equator that is anticlockwise in the northern hemisphere (as it's curling away back to the west) and clockwise (again curling away to the west) in the southern hemisphere.

Hope this helps, it's the best I can do!

[Pikey P]

mat205125 said:

I see you've played knifey spoony before

HaHa, i love that quote. it was even my text message noise for a while

[ih8thisname]

dilbert said:

Get a bit of paper, and put it on the table in front of you.
Get a pen, and place it on the paper.
Push the pen forward, whilst moving the paper to the side.
That's the thing.

Ah-ha.

So if you have a very long range weapon (ie. Sniper Rifle) and you are aimed at an object very far away, far enough away that you would encounter such things as the spinning of the earth, would I be correct in saying that you would not hit exactly where you are aiming, instead the bullet would swerve off to the left/right hand side?

Or have I got the wrong idea here?



Yes, this question did come upon me when playing Call of Duty on the 360.

[mat205125]

Pikey P said:

mat205125 said:

I see you've played knifey spoony before

HaHa, i love that quote. it was even my text message noise for a while

I think it has to be one of my favourite episodes.

[Pigeon]

MK4 Slowride said:

In the X-files Moulder found a sink somewhere that the magnetics were all messed up and it went both ways with a wobble.

Which was nice.

They all do that sir...

ih8thisname said:

dilbert said:

Get a bit of paper, and put it on the table in front of you.
Get a pen, and place it on the paper.
Push the pen forward, whilst moving the paper to the side.
That's the thing.

Ah-ha.

So if you have a very long range weapon (ie. Sniper Rifle) and you are aimed at an object very far away, far enough away that you would encounter such things as the spinning of the earth, would I be correct in saying that you would not hit exactly where you are aiming, instead the bullet would swerve off to the left/right hand side?

Or have I got the wrong idea here?

You have exactly the right idea. Long range artillery does indeed need a Coriolis correction applied.

[Pikey P]

So, was i right in calling the water draining phenomenon the Coriolis effect?

[TomE]

ih8thisname said:

dilbert said:

Get a bit of paper, and put it on the table in front of you.
Get a pen, and place it on the paper.
Push the pen forward, whilst moving the paper to the side.
That's the thing.

Ah-ha.

So if you have a very long range weapon (ie. Sniper Rifle) and you are aimed at an object very far away, far enough away that you would encounter such things as the spinning of the earth, would I be correct in saying that you would not hit exactly where you are aiming, instead the bullet would swerve off to the left/right hand side?

Or have I got the wrong idea here?



Yes, this question did come upon me when playing Call of Duty on the 360.

If you stood ontop of a high enough mountain and fired the sniper rifle, it theoretically could come back round on you as it would be falling all the time as it went round the curvature of the earth.

Often wondered whether the whole 6 minutes (or whatever it is) you lose when travelling round the earth would mean it would hit the ground six minutes before you were expecting it though.