HOW MAnY M&MS?

Physics professor Paul Chaikin loves M&Ms so much his students once gave him a 55-gallon barrel filled with the chocolate candies. They never guessed their gift would lead him to make an important scientific discovery.

Chaikin began to think about how tightly M&Ms could be packed. Scientists have been studying arrangements of perfectly round spheres-like oranges or marbles-since the 1600s. They've proved that you can fit many more spheres in a container if you stack them neatly rather than just pouring them in any which way.

Since M&Ms are basically just squashed spheres-a shape called an oblate spheroid-Chaikin thought the same would be true for M&Ms. But it turns out that even though spheres and spheroids behave the same when neatly stacked, there's a big difference when they're randomly poured. You can fit nearly as many M&Ms in a container just by pouring them as you can by carefully stacking them. Their flattened shape allows the candies to shift and tilt to fit together more closely.

What's the big deal? Well, besides helping them win those contests where you guess how many candies are in a jar, knowing which shapes fit together best will help scientists develop clearer glass and stronger ceramics. Both those materials are made up of lots of little particles all packed together-just like candies in a jar.

Copyright Carus Publishing Company Jul/Aug 2004
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