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John McChesney aka "Mr. Mack," is a mechanical engineer who teaches his brand of science wizardry in schools and homeschools throughout Santa Clara County. Send your requests and comments to:
John McChesney,
1659 Scott Blvd., #33,
Santa Clara, CA 95050.

Storybook Science - The Swimming Pool

By John McChesney

Once upon a time there was a beautiful underground world complete with trees, flowers, and hundreds of GLORCHES. For those that have never met a Glorch before, it is an experience that you would never forget. Glorches are BIG. They are FAT. But worst of all, Glorches can glorch (burp) with such power that they can blast a person clear out of sight! In this under-ground world, the Glorches play an important role: the walls of the cave glow yellow with light and warmth; the lake provides all the necessary water; but only the Glorches can provide the clean air needed to keep everything else alive so far beneath the surface of the earth.

Directly above our beautiful subterranean world, on the earth's surface, we find the house where Jack and Jill live! It is a very hot day so Jack and Jill are busy digging their own swimming pool. Day after day they work from sunrise to sunset. First, Jill (up in the hot sun) pulls the buckets of dirt up out of the hole with ropes; and Jack deep down in the cool shade shovels the dirt into the buckets. Then they trade places.

After 10 days of hard labor, Jack and Jill put on their swim suits, hook a huge hose up to the nearest fire hydrant, and start filling up their pool. Since the ground is so sandy and the pool so big, it took 5 hours with the fire hose going full blast to fill the pool. Once their swimming pool was full, Jill turned off the water and they both dove into the pool together.

Unfortunately, Jack jumped a little too high, and dove in too deep. When he hit the bottom, he punched a hole right through the remaining ground. The next thing Jack knew, he and Jill along with about 2000 tons of water were falling into the beautiful subterranean world!

When all the Glorches in the cave saw the water falling they all glorched at the same time in an attempt to blow the water back up out of their cave. But they were too late, the water was already inside so the pressure they created just pushed the wet ground back up and sealed the hole closed.

It was very lucky for Jack and Jill that they landed in the lake because otherwise they would have been flat as a pancake on the hard ground. Once Jack and Jill regained their senses, they noticed the warm glow of the walls, the tall green trees, and the many kinds of ducks floating on the lake. The ducks seemed a bit odd though. They would try to swim underwater to feed on the bottom but they floated so well that they could only swim down about 6 inches before they bobbed back to the surface.

When Jack and Jill swam to the beach they came across their first Glorch which was so angry that it blasted Jack and Jill right back into the middle of the lake!

"What did you do that for?!" yelled Jill, "We weren't trying to hurt you!"

"It's not me that I'm worried about," replied the Glorch, "you have dumped so much water into our lake that it is 3 feet deeper than before. The poor air-headed ducks can only swim down 6 inches so they can no longer reach the algae that they used to eat in the shallow water. Because of you, they are all going to die of starvation!"

If you were Jack or Jill, what would you do to save the poor air-headed ducks?

The Air-Head Experiment

Materials Needed:

  • A cup
  • 2 liter soda bottle full of water (label removed).
  • A very small balloon.
  • A few washers that will fit around the opening of the balloon.
  • Permanent marker


  1. Blow up the balloon (don't tie it) and draw a face on it with the marker.
  2. After the ink is dry, deflate the balloon and put the washers on the opening.
  3. Drop the balloon in a glass of water. Either add air or remove water from inside the balloon so that it just barely floats.
  4. Covering the opening of the balloon, remove it from the cup and drop it in the 2 liter bottle. It should just barely float there too.
  5. Put the cap tightly on the bottle.
  6. Try to make the balloon go to the bottom of the bottle and then come back up again without moving the bottle or using magnets.

Hint:  Air is compressible. If the air is squished, the balloon will be more dense.

Try This:  Put several 'air-heads' in the bottle so that some just barely float and some sink. Place the bottle in the fridge and see what happens!