The Earth's Rotation

About how long does it take for the Earth to rotate half a turn on its axis?

And the answer: 12 hours.      

It takes a day, or about 24 hours, for the Earth to complete one rotation on its axis. So it takes half that time – 12 hours – for the planet to rotate halfway.

Photo credit: Maulor

The Earth is constantly rotating on its axis. The invisible line which runs from the South to North Pole defines which areas of the Earth receive sunlight at which times – thus, time zones. However, did you know that not every place on Earth rotates at the same speed? The regions closest to the equator have the highest rotational speed (explaining why they launch so many rockets from Florida), while those farthest away from the equator rotate the slowest.

Additionally, the tilt of the Earth's axis is the reason for the phenomenon called Midnight Sun in Nordic countries (which means exactly what it's named for: nearly 24 hours of sun), as well as the complete lack of sunlight in winter months. At a tilt of 23.5 degrees, the ability for sunlight to reach far northern or southern regions highly depends the month of the year – AKA the position of the Earth relative to the sun. This means that in the north's summer, the northern hemisphere is tilted towards the sun, while in the winter, the northern hemisphere is tilted away from the sun.

But why can't we feel the Earth rotate under us every day? Well, the short answer is that we're moving too. Even though the Earth is hurtling around its axis (and around the sun at the same time), there are no changes to its speed. Thanks to gravity and centrifugal force – which refers to the outward force on a mass when it is rotated – we stay grounded on our planet and cannot experience its spin.

Learn more about Earth's rotation from Neil deGrasse Tyson here.

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