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## Come Rain or Shine

Skip to 0 minutes and 7 secondsSo now we're going to look at a demonstration of the Coriolis force in action. We know that the Coriolis force leads to a deflection on a curved trajectory of anything that's moving over the top of a rotating surface. To simulate that, we're going to use a rotating turntable here to simulate the earth's surface. And this ball bearing is going to simulate a parcel of air moving over the rotating earth's surface. So what I'm going to do is I'm going to start the turntable rotating. I'm going to drop ball bearing onto the turntable, and we're going to see the pattern that it traces.

Skip to 0 minutes and 37 secondsWe going to see that pattern from a camera that's outside the turntable, the one that you're filming me on now. And we're going to see the ball bearing takes one track. We're also going to look at the track of the ball bearing filmed from a camera that's rotating with the turntable. So this camera here is mounted on the turntable, and will rotate with it. And on a separate set of monitors, we're going to look at the apparent track that the ball bearing is taking relative to the rotating turntable. So I'll start the motor running here. It'll take it a little while just to get it to the right speed.

Skip to 1 minute and 13 secondsThat's looking pretty good now. So I'm going to drop the ball bearing down the ramp, and then we're going to watch the path that it takes.

Skip to 1 minute and 25 secondsSo what we can see with the fixed camera is that the ball bearing seems to be pretty much just rolling backwards and forwards across the dish. If we go over to the camera that's mounted on the turntable, what we see is that the ball bearing is actually following a very tightly curved trajectory relative to the motion of the dish itself. So that's like the weather systems above the earth's surface, rotating as they move over the earth's surface. We see that curve trajectory wiggling away like a little snake now. And we can see that the ball bearing's now losing its energy. It's starting to move down into the center of the dish.

Skip to 1 minute and 57 secondsSo what we've seen there is basically the fact that the Coriolis force, the effect of the rotation of the turntable, is making an apparent deflection of the ball bearing's track. So from the camera that was outside the turntable, the ball bearing is pretty much just rolling backwards and forwards. But from the camera that's mounted on the turntable, the ball bearing's taking quite curved, tightly curved, trajectories in a circular path. And that's just like air parcels moving over the earth's surface.

# The Coriolis Effect

In this video, Pete uses a turntable and a ball to simulate the effect of the Coriolis force. The ball is deflected on a curved trajectory, across a rotating surface, to help you visualise a parcel of air moving over the Earth’s surface.

As air blows from high to low pressure in the atmosphere, the Coriolis force diverts the air so that it follows the pressure contours. In the Northern Hemisphere, this means that air is blown around low pressure in an anticlockwise direction and around high pressure in a clockwise direction.