# I want to understand the concept of earths rotation (May be its a silly question)?

Science has proved that the earth rotates and due to gravity we don't feel that we too are rotating along. My question is, Imagine that from a point A, I vertically go up in the space above the earth(like in a helicopter). Stay there without moving horizontally and after some hours come back vertically as I went up. now I should land in a different point other than A since earth would have rotated some distance. Does this logic work ???

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• Bob G
Lv 6

It almost works.

You're already moving horizontally because you started from the source of the Earth. If you did this at the equator, you'd be moving East 465 meters per second. By moving vertically, you'd increase your distance from the center of the Earth, effectively increasing your radius.

The larger the radius, the larger the circumference (C=2*pi*r), so the horizontal 465 meters per second you're moving would be a smaller portion of your circumference. So, when you came back down, the Earth would have rotated a greater percentage of its circumference than you did, meaning you'd land to the West of where you started.

In fact, thinking of it like that is stepping towards thinking of angles in terms of how many radiuses you've swept out around the circle (except the plural of radius is actually radians, not radiuses).

By the way, gravity is why us and the atmosphere stay on or near the surface of the Earth. The reason you don't feel the rotation is because the Earth rotates at a constant speed and carries you and everything around you, including the air, at the same constant speed - just like how you don't really feel how fast you're moving when driving a constant speed down the interstate.

• Anonymous

Yes it works, and actually it happens like that... you experience Coriolis force when moving straight up, as seen from the surface of Earth. In fact, some soldiers have to deal with this already for centuries: artillery has to take the rotation of Earth in account, or miss by a huge distance.

Try this experiment.

Get a yo-yo. Tape one end of the string to the ceiling and let it hang free. Then pull the pendulum back and let it swing freely. You'll see the pendulum doesn't swing straight back and forth: it actually shifts its angle a very slight bit every single time it goes back and forth.

This is (partly) because the Earth is rotating under the pendulum, even as the pendulum is swinging free.