Toilets and Eggs at the Center of the World

Today at the Museo Inti-Nan, we were given a wonderful presentation of the Coriolis Effect!

Theorized by Gaspard-Gustave Coriolis in 1835, the Coriolis Effect is the curving of objects on a rotating frame. This means that when the frame moves clockwise, the object curves to the left as it moves. When the frame moves counterclockwise, the object curves to the right as it moves.

An example of this effect is widely known from the rotation of the earth. As the earth rotates, currents of the oceans and the wind move clockwise in the Northern Hemisphere and counterclockwise in the Southern Hemisphere. This is why there are only hurricanes and tornadoes in the Northern Hemisphere and only cyclones and typhoons in the Southern Hemisphere. However, these movements reflect away from the equator, which decreases the force of the Coriolis effect on the equator line.

This is why, as you can see in the first demonstration of the video above, the water draining from the tub does not form a spiral as it drains. But as you can see in the next two demonstrations, if the tub is moved away from the equator line, it will produce a spiral as the water drains. Unfortunately, this isn’t a true representation of the Coriolis Effect because the rotation of the spirals is highly influenced by the way the tub is filled. Depending on which side the presenter of the experiment is standing when the water is poured into the tub, the water will bounce along the sides of the tub creating a slow rotation before the water is drained. Toilets are also influenced by a similar effect except it is determined by the direction the water shoots out from the rim of the toilet. So, the Coriolis Effect does in fact have a slight influence on draining water, but other influences, such as the way the tub of water was filled, have a much greater effect creating the possibility of the predictions made by the Coriolis Effect to be wrong.

There are many other great experiments that can be done on the equator line as well. Due to the decrease of gravity and the Coriolis Effect at the equator, it is possible to balance an egg on a nail. This decrease in gravity also makes it very difficult to resist someone pushing down on your arms when they are completely stretched out. The forces reflecting off from each side of the equator also makes it very difficult to walk along the equator line with your eyes closed. Although these experiments are not perfect demonstrations of the Coriolis Effect due to how weak of an influence it really is, but they are still great for teaching and simplifying how the Coriolis Effect works. To observe a true Coriolis Effect, a great example are the movements of hurricanes, tornadoes, typhoons, and cyclones.


-Jacob G.


One thought on “Toilets and Eggs at the Center of the World

  1. Are you having trouble uploading video? You need to put it on your YouTube channel first. Ask Kim — she knows how to do it! 🙂

    Looks like you guys are having a great time! Love reading your reports … 🙂

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