The Math of the Beijing Water Cube

The Water Cube

The National Aquatics Center (or “Water Cube”) was built in Beijing as the venue for the swimming and diving events in the 2008 Olympics. Not surprisingly, there is some cool math behind this cool building.

Way back in the 1880’s Lord Kelvin asked what the shape of the bubbles would be if you wanted a foam made of very small bubbles which all have the same volume and have the smallest possible surface area.

Like many math problems, this one came from a question in physics: If there is a luminiferous ether, then what does it look like?

Also like many math problems, this is easy to ask and hard to answer. Here we are 120 years later and we still don’t know the answer! In 1993 Denis Weaire and Robert Phelan, two Irish physicists, gave us the Weaire-Phelan foam and conjectured that this is the foam that answers Kelvin’s question. We still don’t know if they’re right, but their foam is the source of the cool geometry of the Water Cube. You can read more about it in this article in Science News by Julie Rehmeyer and in this blog post by John Baez.

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