MOLINE, Ill — An old myth is recirculating once again on social media. This time, an added twist claims that by simply hopping to the south half of the equator, you'll be able to see water spinning in the opposite direction of what it would in the north. The video shows a tourist trap in Uganda, including three different bowls of water and a line supposedly marking the exact location of the equator.
Carolyn from Colona, Illinois, wrote in asking, "This was on Instagram. Is this for real? The equator and directional differences." Let's dig in!
Here is the post for reference and the examples that are used to supposedly 'prove' that this theory is legit.
Why this is a myth
The claim that water spins backward in the southern hemisphere is false. It's been around for a while, including the popular misconception that even toilet water spins in the opposite direction after being flushed. Scientists and even experiments have debunked it.
While it is true that the Earth's rotation does influence the direction of moving fluids, including air and in this case, water, the effect is too weak to be noticeable in something that is on such a small scale, like a bowl, sink, or toilet.
The Coriolis Effect
The Coriolis force is only noticeable and significant for much larger-scale systems, like weather patterns and ocean currents which can span hundreds of miles in diameter. This effect causes moving objects to appear to curve across long distances, instead of going in a straight line.
Different parts of the Earth rotate at different speeds due to the Earth's bulge at the equator. The equator spins at a much faster rate than the north and south poles.
With weather patterns, the Coriolis effect influences the direction of winds and helps form hurricanes, low-pressure systems, and even jet streams. It even impacts the direction of ocean currents, impacting the global climate.
It is too weak to be noticeable in small-scale scenarios like water draining in a sink or flushing a toilet.
What they are doing to make it appear to be true
The video shows a gentleman pouring water into three different bowls. One bowl is located on the northern side of the equator, the other allegedly right on the equator itself, and a third bowl is located some distance away on the south side of the equator.
After pouring the water into the bowl, it begins to drain. He then places a flower on top of the water to indicate which way the water is spinning, supposedly due to the earth's rotation. For the northern hemisphere, the flower spins in a clockwise direction, counterclockwise for the southern hemisphere, and on the equator itself, the flower sinks straight down into the drain.
The reason this is happening? The shape of the bowl for one is influencing which way the water is spinning. Also, the angle and direction in which the water is poured. It is simply an illusion being carried out. If you were to take identical bowls, using identical methods to pour the water at the same angle, the result would be much different.
Conclusion: A tourist trap
Simply traveling a distance of just a few hundred feet away from the equator is not a large enough distance to cause any kind of impact by the Coriolis force to change the direction of the water.
So, while it seems impressive, it is just a cheap tourist trap.
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