12 September, 2003

Coriolis Force

If you ever look at the weather map, you will see storms circle counter clockwise in the northern hemisphere and clockwise in the southern hemisphere. People wondered if sinks and toilets would also spiral in the same direction as the clouds. In fact, there is an official toilet in the hallway here (I kid you not), that scientist use to measure this (see picture).

You have felt a different Coriolis force when you play on a merry go round. Have you ever tried to walk on one as it is spinning? Spin it counter clockwise, then walk in any direction, you will always be pushed to your right side. The faster you walk the greater the push. It is like some magic force is pushing you and it vanishes when you stop. Now spin it the other way and walk, you will feel the force to your left no matter how you walk.

The Earth is a spinning Merry go Round. Here in the North, no matter how you walk you will always be pushed to your right. It is a small force because you do not walk very fast or far in comparison to the earth spinning, so you don't feel the effect. But if you shoot a missile the effect is huge and there is a large deflection. In fact the British made an embarrassing mistake once with a sea battle. They knew about the Coriolis force and adjusted all their guns so that they would hit the correct target. They forgot to think about fighting in the Southern Hemisphere! So when they fought in the Falkland Islands, the Navy ships kept missing their target by twice the amount.

Toilets and sinks do not flush in any parcticular direction; the Coriolis force is too small for this. People try to trick you on this fact by spinning the water before hand. You can't tell that it is moving, so when the plug is pulled it will spin in one direction. Many adults in Antarctica were disappointed with their toilets. Which way does your toilet spiral?

Tomorrow we will have an evening launch to match an ozone sonde that was launched days ago from Belgrano station across the continent.

The official site for Coriolis testing in the Southern Hemisphere.

A physics penquin is the best thing to have around.