We’ve been hearing a lot about the polar vortex that’s freezing most of the country right now, but what is a vortex? It has to do with the way the air and the moisture in it are moving.
To make your own vortex at home and see for yourself what’s happening, you’ll need two 2-liter bottles with the labels removed, a washer with a 3/8’’ opening, duct or electrical tape, water and glitter. Fill one bottle almost all the way with water and shake in as much glitter as you like. The glitter will help you see the movement of the water once your vortex gets going.
Tape the mouths of the empty bottle and the full bottle together with the washer between them. The washer will make an even smaller opening between the two bottles so only a little water can get through. Use enough tape to make a very tight seal; you don’t want any water leaking out.
Your vortex is now ready to go! Get started by turning it upside down so that the full bottle is on top, and just set it on the table or floor and observe. What do you see happening? How fast is the water moving, or is it moving at all? What about the glitter?
You may be seeing a little water dribbling into the bottom bottle and a few air bubbles pushing up into the top bottle, or the water may not drip much at all. That’s because of pressure and how small the hole is between the two bottles.
When lots of water molecules get together, like in a big bottle, they like to stick together and develop surface tension. Surface tension is like a skin on top of the outside edges of the water. It’s what helps lightweight things float. The edge of the water that’s touching the washer has surface tension.
When there’s lots of water in the top bottle, gravity is strong enough to push through the surface tension and pull drops of water into the bottom bottle. And there’s enough pressure in the bottom bottle to push air bubbles up to the top. But when there’s less water in the top bottle, there’s no longer enough pressure to break the surface tension, so in spite of the hole, the water stays in the top bottle.
Now try swirling your vortex around very fast several times. What’s different in how the water and glitter are moving now? How fast is the water draining into the bottom bottle?
Notice the spiral shape that the waves of water and glitter are forming in the center of the bottle. When you add spinning motion, angular momentum causes the molecules in the middle of the bottle to move faster than the molecules near the sides. That helps the top bottle drain quickly and smoothly.
And then you can turn your vortex over and do it all again! What you’re witnessing in your bottle is very similar to the weather happening over most of the country right now — that’s why meteorologists are calling it a polar vortex!
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