npr must have a had a slow news day. but the result is fascinating…
Sanat Kumar, chair of the chemical engineering department at Columbia University, had this idea. He and I took out his superprecise scales and emptied out a couple of packages of M&M’s. We started counting how many M&M’s were in each peanut butter M&M’s package. Were they the same? Nope: One had 28 M&M’s, but the next had 26. Another beautiful theory destroyed by data.
But weighing the M&M’s did help us discover something weird that would turn out to be a critical clue. It was something I’d never noticed while I was stuffing these things in my mouth — Peanut Butter M&M’s and Milk Chocolate M&M’s are totally different species. The regular M&M’s are small, very precise candies with very precise weights, but the peanut butter ones are larger, lumpier and more irregular. When we put them on Kumar’s scale, the Peanut Butter M&M’s were much heavier, and their weights were all over the place.
And this larger size turned out to be the key to the whole puzzle.