Is it possible to blow a toroidal soap bubble (one shaped like a ring doughnut)? And if it is, would it collapse immediately to a sphere? Could its life be prolonged by spinning its surface, as with smoke rings?
• A soap bubble is the minimum surface which encloses a given volume. If a toroidal bubble were created, it would not provide such a minimum surface and would therefore tend to contract to reduce its surface area until it collapsed into a bubble which would then burst because of the forces created at the disappearing hole in the torus. This situation differs from that in a solid torus such as a bicycle inner tube, because soap bubbles can transfer part of their surface from the inner to the outer part of the torus as they shrink.
A temporary toroidal bubble could perhaps be created by sticking spherical bubbles in a ...
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