We continue to the Intiñan Solar Museum, known as the Trek of the Sun, to stand on the equator where summer turns into winter. As our driver took us, he mentioned that the exact latitude 0°0’0” was not actually at the museum. He had me take out my phone and open the compass. As we drove closer to the museum, my GPS went from 002”S to 001”N to 000”N on the road, kind of near the museum.

While in the museum we were shown how the Incas used sundials to tell conventional time. And how the ‘solar chronometer’ shows astronomical time, as well as the month, day and season – all by using the rays of the sun. We learned that water flows clockwise on one side of the hemisphere and counterclockwise on the other side. We attempted to stand up an egg on a nail. We were not successful, but others were. We learned there is a weakening of muscles due to low altitude as they tested arm strength. We walked on the equatorial line with our eyes closed to test our balance.  Mark and I stood on different sides of the equator – one of us in winter and one of us in summer. It was entertaining. 

After our visit, my driver asked if I told them the museum is not actually on the equator. I replied, “No, I did not want to ruin it for others.”

Then I started thinking – how could all those “experiments” work if it wasn’t exactly on the equator. So, I looked it up and immediately realized we had been duped.

From Wikipedia … “Tour guides and visitors demonstrate tricks which are supposedly possible only on the Equator, such as water flowing both counter-clockwise or clockwise down a drain due to the Coriolis effect. However, the Coriolis force has no effect on the apparent direction of draining water in household drains anywhere on Earth, as this is too small of a scale of motion to be affected by the larger-scale force. Another apparent trick performed here is balancing eggs on end. This is purportedly easier at the equator due to the claim of a relative maximum in the magnetic field at the equator. However, attempts to balance eggs work just as well anywhere else on Earth, and are not influenced by magnetism or the Coriolis force. Also, there is an apparent weakening of muscles due to low latitude. This is also linked to the claim that certain physical forces, including the Coriolis force, are significantly weakened at the equator.”

So, I looked past the picture of the sign I took at the museum about the Coriolis effect and went to see the science behind It. The Coriolis effect is caused by the Earth’s rotation. It influences the direction of large-scale movements like: hurricanes (spin counterclockwise in the Northern Hemisphere, clockwise in the Southern), ocean currents and trade winds.

But the Coriolis Effect does not happen in your bathtub because it is very weak on small scales. In toilets, sinks, or bathtubs the direction water drains is mostly influenced by the shape of the basin, the initial motion of the water and plumbing design.

So, while the Coriolis effect is real and does affect large systems, it does not reliably determine the direction water swirls in household drains. Where it does matter is in meteorology as storm systems rotate differently in each hemisphere. And in ballistics and aviation where long-range trajectories must account for it.

Oh well, just goes to show you cannot believe everything – even if you see it with your own eyes.