The Coriolis Effect
In: Physics
This is the sort of concept that’s really tough to describe with words and is much better understood visually through examples like these:
[https://www.youtube.com/watch?v=mPsLanVS1Q8](https://www.youtube.com/watch?v=mPsLanVS1Q8)
That’s a tough one, and I saw the other respondent posted a video but I’d like to try and test my teaching chops by explaining it by text. However, like the video it will use a lot of imagery just mental imagery.
It’s going to be a long explanation so feel free to just say screw it and not read it. No tldr for this one.
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So I want you to think of the Earth by looking down on it from the north pole. It looks perfectly circular right? And it spins and a constant speed too. So let’s just think of it as a flat circle.
Now I want you to mentally place 2 dots on that circle, one close to the center and one on the edge, and rotate it 360 degrees once. Now think about those 2 dots each tracing a line as they move. Compare those 2 lines side by side and you’ll see the inner dot traced a shorter distance after 1 rotation than the outer line. However both completed 360 degrees at the exact same time. Meaning that the outer dot had to have traveled faster than the inner dot to end at the same time over a longer distance.
I hope you’re still with me.
So we’ve established that the outer part of our circle is actually moving faster than the inner part as it spins which we can assume is true for any part of the circle. The inner part will always move faster than the outer part when spun. And as we know when you’re moving forward that motion is added to anything you throw. That’s why when you’re moving and hiring a stationary target you need to aim before the target do the forward motion added by the movement will carry the object to the target. Also why you need to throw ahead of a moving target so the motion of the target will carry it to the object.
Now let’s picture ourselves standing on that circle throwing a ball as it rotates. We’ll stand on the inner dot and throw the ball away from the center. As the ball is thrown it will move outwards and enter faster and faster areas, meaning compared to the motion of our circle the ball will actually have less speed moving sideways. So as it continues to move further and further into faster and faster rotating areas it seem to curve behind to you standing on the inner dot.
The opposite is true when you stand on the outer dot and throw in. The speed of that ball will be moving to slower area meaning it will curve ahead of the point you were aiming at.
Now we can once again make the Earth 3D by thinking of it as a series of circles getting smaller and smaller. So when you throw something from north to south (if the distance is long enough) the earth will rotate beneath it moving the target ahead of where you were aiming when you threw it, but to you it appears the ball curved to the West. Throwing from South to north the opposite will happen. The target will end up moving slower than the pint you’re aiming at so the ball will appear to curve to the east
If you’re looking for why this matters. It’s actually why in the northern hemisphere we have hurricanes that spin clockwise and in the southern hemisphere they have cyclones that spin counter clockwise. Because as the fast air from the equator moves away from the equator it moves relatively faster than. The air moving toward the equator creating a spinning mass of air that collects moisture and speed under the right conditions.
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