Aurora, IL
Toilets are an ubiquitous part of our everyday lives around the globe, and a substantial difference within them in certain areas could be hard to imagine considering their omnipresence. However, it is a commonly held idea that toilets flush counterclockwise in the Northern Hemisphere and clockwise in the Southern Hemisphere. This intriguing and often-debated phenomenon has sparked curiosity and skepticism alike, captivating the imaginations of travelers and armchair scientists around the world. Numerous experiments near the Equator have supposedly demonstrated this mysterious effect and attribute it to the mysterious Coriolis Effect. Does this phenomenon really exist? And what is the Coriolis Effect? Let us delve into the fascinating world of bathroom folklore and scientific exploration to uncover the real story behind toilets and the enigmatic Coriolis Effect.
However, the fact of the matter is that the toilet flushing phenomenon is strictly a myth. Its connection to the Coriolis Effect is also an urban legend. The exact origin of the phenomenon is unknown, but it has been popularized by pop culture, media, and word-of-mouth ever since the 1960s when scientists at MIT demonstrated that the Coriolis Effect has a small effect on water swirling in a bathtub. However, because this experiment was conducted under near-perfect circumstances, it cannot be reasonably extrapolated to toilets’ flushing mechanisms. Movies and TV shows like Escape Plan (2013) and The Simpsons (1995) have incorrectly illustrated the phenomenon, leading to its presence as a commonly held misconception. In fact, the direction in which toilet water swirls is entirely dependent on how the toilet is created, not on its position on the Earth’s surface. All of the “experiments” conducted near the Equator demonstrating toilet water flushing in different directions are really just cheap tourist traps and should be avoided.
The mystery of the Coriolis effect, however, still stands. The Coriolis effect, otherwise known as the Coriolis force, is defined as Fc=-2m(Ω x V), where m is the mass of the object upon which the force is being acted, Ω is the angular velocity of the object, and V is the tangential velocity of the object. The Coriolis force is an application of Newtonian mechanics from a rotating frame of reference—that is, the observer is rotating either clockwise or counterclockwise. When this occurs, the object in question will appear to be deflected towards the right of the observer when spinning counterclockwise and towards the left of the observer when spinning clockwise. This can be demonstrated on a smaller scale using a spinning merry-go-round with two people on it. Let’s call the observer (the one throwing the ball) Person A and and the catcher Person B, who are both positioned on opposite ends of the merry-go-round. As the merry-go-round spins counterclockwise, Person A seems to throw the ball straight towards Person B, but the ball curves in the air to the right of Person A. While it may look like the ball traveled straight from a constant, non-moving frame of reference with respect to the Earth, from the rotating reference frame of Person A, the ball will have curved. This is the magic of the Coriolis effect: objects are deflected a certain direction depending on the frame of reference’s rotation.
The Coriolis effect can be similarly extrapolated to the scale of the Earth, as the Earth also rotates at a fixed speed. When observed from the top (near the Arctic), the Earth seems to be spinning counterclockwise. In addition, the Earth spins much slower near the North Pole than at the Equator, which is why storms and cyclones get deflected towards the right (eastwards) in the Northern Hemisphere. Similarly, the Earth seems to spin clockwise when observed from the South Pole, so cyclones and storms get deflected towards the left (westwards) in the Southern Hemisphere. In fact, hurricanes (Northern Hemisphere) rotate counterclockwise while cyclones (Southern Hemisphere) rotate clockwise, corresponding to their deflection directions. The Coriolis effect thus has a very large impact on weather and climate patterns across the globe. Coming back to our original example, the Coriolis effect does not impact toilet water because of the miniscule mass of the water. The Coriolis effect on its own is a very weak force and only comes into play when dealing with large entities such as hurricanes and cyclones. Therefore, the Coriolis effect definitely does not have any correlation with toilet water flushing in different directions in different hemispheres and the myth is debunked.
References
Evers, J. (2023, May 2). The Coriolis Effect: Earth's Rotation and Its Effect on Weather. The Coriolis Effect: Earth's Rotation and Its Effect on Weather. Retrieved July 24, 2023, from https://education.nationalgeographic.org/resource/coriolis-effect/7th-grade/
Rafferty, J. P. (2017, May 23). Do Toilets in Different Hemispheres Flush in Different
Directions?. Encyclopedia Britannica.
https://www.britannica.com/story/do-toilets-in-different-hemispheres-flush-in-different-directions
Britannica, T. Editors of Encyclopaedia (2023, July 11). Coriolis force. Encyclopedia Britannica.
https://www.britannica.com/science/Coriolis-force
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