Bubble trouble: Adding glycerin to children's bubble mixture leads to much more stable bubbles which can be prodded and moved without bursting. They can also fall to the carpet and sit for a while before bursting. How does glycerin interact with the soapy water to stabilise the bubbles, and is there an even better substance I can use for doing this?
Top that: I have a small spinning top which has a low centre of gravity. When you give it a push it readily restores itself to the upright position. The top can be made to spin by twisting the stem between the index finger and thumb. The top then precesses with the axle getting lower and lower until it eventually flips over and continues to spin in an upturned position. When the spinning stops the top returns to its original stable state. Can anyone explain why this happens?
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