Peter V asked in Science & MathematicsPhysics · 1 decade ago

When you run water out of your bath, it swirls anti-clockwise south and clock-wise north of the equator.?

When water flows from your bath, the direction it twirls is different in the Southern hemisphere to that in the northern hemisphere, why is that?

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  • 1 decade ago
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    We sit, fixed by gravity on the surface of our planet, unaware of its rotation (except by the movement of the sun, moon, and stars). Yet we are hurtling to the east at a speed of nearly 700 miles per hour, owing to the earth's rotation. Our perception of the direction of that rotation differs from northern to southern hemispheres. The earth clearly rotates to the east (the direction in which the sun rises). In the Northern Hemisphere, we perceive this rotation as counter-clockwise; in the Southern Hemisphere that same direction of rotation is perceived as clockwise. So the movement of the water is really our perception of fluid movement from our vantage point on a rotating sphere (called the Corliolis Effect). The effect isn't great enough to effect the water in your tube or toilet but can been witnessed in the movement of the atmosphere or ocean.

    Source(s): Ed Clifton - Monterey Bay Aquarium Mentor
  • 5 years ago

    The Correolis effect does cause water to swirl clockwise in the northern hemisphere and anti-clockwise in the southern hemisphere due to the Earths rotation. This however only occurs in large bodies of water such as the ocean. At a small scale, such as bath water or flushing the toilet, the direction the water swirls is entirely random.

  • Anonymous
    1 decade ago

    The previous poster is correct--in real life, the drain direction depends mainly on the drain design. I have at least two drains in my apartment that drain counter-clockwise.

    In theory, the Coriolis effect determines the direction of rotation of a vortex. However, the magnitude of the effect depends on how much surface area the vortex covers--and your kitchen sink covers very little area compared to a hurricane.

    If you had a perfectly calm sink with a perfectly symmetrical drain, and you let the water out without imparting in spin into the water, yes, it would rotate clockwise in the Northern Hemisphere. However, in real life, other factors predominate.

  • Just the opposite, north of the equator it swirls anti-clockwise just like a low pressure hurricane does. If you place a ruler on its side and put a marble on each side and call the sides north and south and the ruler the equator and pull the ruler from left to right, left being west and right being east, then the marbles will turn counter-clockwise (anti-) on the north side and clockwise on the south side, as the earth rotates towards the east .

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  • 1 decade ago

    No, its a classic urban myth. The Coriolis Effect has a _very_ small influence that can only be measured under carefully controlled laboratory conditions. Other influences like the form and the surface texture of the bath will allways dominate.

  • 1 decade ago

    No, this is a common myth. The direction of the flow has to do with how the drain was designed, not which hemisphere it's located in.

  • 1 decade ago

    The Earth speed of rotation is fastest at the Equator. As you go north or south in latitude the speed of the rotation slows. The water in your toilet gravitates toward the slower rotation hence the difference between cyclonic effect north or south of the Equator.

    Source(s): Always fascinated by the same issue.
  • Neil S
    Lv 4
    1 decade ago

    It's a furfy don't you know.

  • 1 decade ago

    good question i'll be watching this one.

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