The fishes will go up and down in the bottle when you squeeze and release the PET bottle. The mechanism of this experimental tool is related to a famous scientific principle. Let’s make this interesting tool!

Things which you need

• A PET bottle with cap (a round one is preferred)
• 2 or 3 small sauce bottles or eye droppers
• Metallic nuts which fit over the sauce bottles

You can get sauce bottles and nuts at a hundred-yen shop!

• A cup to prepare water in it
• Water (Tap water is fine.)
• Additional Materials : Things you can use for decoration, such as marker pens and marbles

How to make

For more detailed instructions, please watch the video above.

※To make this craft, you have to use water. Please make sure to use this in places where you wouldn’t mind spilling water.

1. Remove the lid from the sauce bottles, and replace them with metallic nuts.
2. Pour water into a cup, and float bottles.
3. Suck water into the bottles so that it only has the tip of it showing above the water surface when floating.
4. Fill the PET bottle with water.
5. Put the sauce bottles into the PET bottle, with the metallic nut facing down.
6. Making sure to leave no air inside it, close the PET bottle.
7. Also, have fun by decorating this with colored pens and marbles!

How to play

Squeeze the PET bottle and then release it. The sauce bottles will go up and down in the bottle!

コラム「アルキメデスと王冠おうかん」

古代こだいギリシャの科学者として名を遺のこしているアルキメデス。彼かれは、王様おうさまから、職人しょくにんの作つくった王冠 おうかんが純金じゅんきんで作つくられたものか、王冠 おうかんを壊こわさずに確たしかめよ、という命令めいれいを受うけます。その王冠 おうかんには金きんをいくらか減へらして代かわりに銀 ぎんを混まぜてあるという告発こくはつがあったからです。

職人しょくにんに渡わたした分ぶんと同量どうりょうの金塊きんかいと比くらべてみても、王冠 おうかんの重おもさは同おなじでした。その当時とうじ... 続つづきを読む