The Spinning Earth
Did you know that the Earth spins at about 1,600 kilometres an hour? That’s supersonic, faster than a flying jet plane. That’s how fast the Earth has to turn to make a complete rotation every day.
So why don’t we feel it, or feel giddy, or queasy? After all our stomachs get queasy even when we spin around on a merry-go-round, which turns at a much slower speed.
It turns out we don’t feel ourselves spinning on Earth for the same reason that we don’t feel ourselves moving while we’re on a steadily moving train. That’s because both the Earth and the train are what physicists call “frames of reference” – it’s all relative.
Frames of Reference
Take the steadily moving train passing by a station without stopping. A person standing in the train will have one perspective or view (a ‘frame of reference’), while a person standing on the station platform will have another.
If you were standing on the station platform, you would clearly see that the platform you’re standing on is standing still while the train passes by. But if you were inside the train looking out the window, you’d feel like you were standing still while the station passed by. From either ‘frame of reference’, you feel like you’re the one staying still.
Inside the speeding train, we wouldn’t be able to feel the wind rushing through our hair to make us realise how fast we’re going. The air inside the train (just as the atmosphere that surrounds our planet) moves along at the same speed we do.
The same is true of Earth and space, but on a much bigger scale. From inside the Earth’s frame of reference, we can’t tell that we’re spinning. But if we viewed Earth from the frame of reference of space, we would be able to see Earth’s rotation instantly.
One important difference between a train and the spinning Earth is that when the train slows down or speeds up, we can feel the change in force on our bodies. And if you’re standing up, you could even lose your balance and fall over with the change in force.
Fortunately the Earth doesn’t ever speed up or slow down. Imagine what you’d feel if it did slow down – from 1,600 km/h!
Want to know more, and the physics behind it? Enjoy this video (click here).
And when you’re done, have fun with your Science teacher and classmates.
This article is extracted from Popular Science magazine.
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