It is a myth that the Coriolis force determines which direction water spirals down drains in everyday cases. The Coriolis force is too small in such cases. Sadly, charlatans have been using it as a tourist trap near the Equator, exploiting unsuspecting tourists.
Flat-Earthers realized the Coriolis tourist trap was just a parlor trick & used it to dismiss the Coriolis effect. In reality, scientists have been debunking this myth all the time. It is flat-Earthers who were duped into thinking it is a genuine scientific argument.
Usually, the tourist trap operator will guide the unsuspecting tourists to a sink supposedly placed directly on the Equator. They will then release the plug and show that the water does not form a vortex. Afterward, they will show a sink north of the Equator and another south of the Equator and demonstrate that the water spirals in a different direction.
In reality, this is only a parlor trick. These people make the water spin in a different direction by how they pour the water. Pouring the water to the right of the drain will make the water spin counterclockwise and vice-versa. Furthermore, when the water drains without spinning, it is because the water is already in the sink. They let the water sit for some time before unplugging the sink.
Scientists have been debunking this myth for some time. For example, Alistair Fraser from PSU debunked this myth in 2003 or earlier, far before the birth of the modern flat Earth craze in the late 2010s.
The myth began from an experiment by Ascher Shapiro from MIT, where he demonstrated that the Coriolis effect can be observed in a bathtub-sized tank. This is, however, an experiment done in a very carefully controlled environment, very different from our everyday bathtub.
References
- Bad Coriolis – Alistair Fraser
- Does the Coriolis Effect Determine Which Direction Water Goes Down a Drain? – Snopes
- How to show that the Coriolis effect is irrelevant for the whirl/vortex in the sink/bathtub? – Physics Stack Exchange
- Does Water Swirl the Other Way in the Southern Hemisphere? – Veritasium & Smarter Everyday
- Flushing out an equatorial fraud – Discover Magazine
- Can somebody finally settle this question: Does water flowing down a drainspin in different directions depending on which hemisphere you’re in? And ifso, why? – Scientific American
- The great plughole debate – The Guardian
- Myth busted: Water does swirl in different directions across the globe, but it’s not a toilet thing – Washington Post
- Verifying a Vortex – MIT Technology Review