You need to know two things: how long it takes to make a full rotation, and Earth’s circumference. The time it takes Earth to rotate so the sun appears in the same position in the sky, known as a solar day, is 24 hours. However, the time it takes Earth to complete one full rotation on its axis with respect to distant stars is actually 23 hours 56 minutes 4.091 seconds, known as a sidereal day.
With this information, to work out how fast Earth is spinning we need only our planet’s circumference. At the equator, its circumference is roughly 40,075 kilometres, so dividing this by the length of day means that, at the equator, Earth spins at about 1670 kilometres per hour.
However, this speed of rotation isn’t consistent across the planet. As you move north or south, the circumference of Earth gets smaller, so the speed of spin reduces until it reaches its slowest at both poles. And all of this is nothing compared with the 107,000 kilometres per hour at which Earth orbits the sun.
Credit: newscientist
Picture credit: Google
