The earth rotates on its axis and one full rotation takes 24 hours to complete.
We’d be very surprised if you didn’t already know that, but what you may not know is that the speed of the earth’s rotation can change from day to day and year to year. So a true solar day is not exactly 24 hours, but the variations are a matter of seconds.
A mean solar day is based on the yearlong average, but the basic concept of a solar day itself is the length of time for the earth to complete one full rotation on its axis.
In 1851, the French physicist Léon Foucault demonstrated how the earth rotates by suspending a lead-filled brass ball from the top of the Panthéon in Paris. This device, now known as the Foucault Pendulum, showed that the plane of the swing of the pendulum rotated relative to the Earth’s own rotation.
Foucault Pendulums can now be found in science museums across the globe. Isaac Newton discovered gravity but he did not actually explain the cause behind it, merely that it exists as a force. The earth’s rotation is the cause for gravity and Foucault’s pendulums demonstrated this.
Earth’s Rotation Day honors Foucault’s first public demonstration and from what we could find it has historically been celebrated on the anniversary of that occasion. That being said, we’re less clear on who first marked the occasion of Earth’s Rotation Day or when they decided to do it. It probably didn’t happen in Foucault’s lifetime, but we can’t be completely certain either way.
The earth rotates every day, but not every day is Earth’s Rotation Day, so you should celebrate it.
If you want to see a Foucault Pendulum in real life, try visiting the nearest space and science museum as many of them have one. They’re actually quite interesting to look at in action.
You could also visit your local space and science museum, so you can learn more about the earth’s rotation. You could do some research on the history of how the way we view the earth’s relation to the universe has changed.
At one time, it was a widely held belief that the earth was the center of the universe and everything revolved around it – the planets, the sun, the moon, and the stars.