Solve it Sunday: In A Spin

Hello everyone! I’m back with another post for Solve it Sunday after missing last week.

I hope you enjoy this one. It was a lot of fun talking through it with some friends, seeing if we could find an answer.

Thanks to the work of Copernicus, Galileo, and may others, we know that the day happens because the world rotates on its axis, while the sun remains (apparently) still. But it is not always wise to blindly believe what you are told.

It would be reasonably straightforward to conduct an experiment that would prove that the Earth is revolving on its axis. You wouldn’t even need to leave the Earth’s surface.

Can you think of one?

One thought on “Solve it Sunday: In A Spin


    There are several good options. For one, drop a spherical object down a tall pipe or shaft (to avoid air currents), and measure how far it deflects from falling straight down. At the equator, a drop of 500 feet will give you an eastwardly deflection of more than an inch.

    Another is to weigh yourself precisely at sea level at the equator, and again at sea level of one of the poles. You will weigh slightly less at the equator, because you are moving faster theres and the rotational forces help to counteract gravity.

    You could also drive directly north from the equator to the North Pole, and examine the eastwards force acting on your vehicle by carefully measuring pressure on your right-hand types. It will be greatest at the equator and fall to nothing at your destination.

    As an aside, it may interest you to know that the sun does not actually revolve on its axis, just as the Earth does. It is a fluid rather than solid, however, so while its equator revolves once every 27 days, its poles revolve once every 31 days.


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