A joint Fermilab/SLAC publication
Image: Cinderella and her pumpkin
Illustration by Sandbox Studio, Chicago

Winner: Cinderella’s convertible carriage


Reader Emily Conover wins symmetry’s latest contest with her fairy-tale description of neutrino oscillation.

Last month we at symmetry challenged readers to send us their best metaphors to describe the strange behavior of subatomic particles called neutrinos.

The nearly massless particles come in three types, or flavors. But neutrinos refuse to settle on just one option; they oscillate among all three.

University of Chicago student Emily Conover submitted the winning contest entry, a text that explained neutrino oscillation in the manner of the Brothers Grimm:

Imagine Cinderella riding in her carriage to meet the prince at the ball. As she gets closer to the ball, the probability that her carriage will morph into a pumpkin increases. She started out in a vehicle that was definitively a carriage, but there’s a chance that it will suddenly become something entirely different! It turns out that this doesn’t just happen in fairy tales.

If Cinderella tried to hitch a ride on a neutrino, she’d have the same problem. Imagine that Cinderella jumped on the back of an electron neutrino. When she gets to the ball she may discover she arrived on a muon neutrino. What a social faux-pas!

An added complication is that, due to the probabilistic nature of quantum mechanics, the neutrino is actually multiple flavors at once. Yes, this means that a neutrino can be two different things at the same time! Only when the neutrino interacts is it finally determined which flavor the neutrino is. So, imagine this: Cinderella is inside the carriage, so she can’t tell if it’s a pumpkin or not. Until the prince pops his head out to look for her, Cinderella’s carriage is simultaneously pumpkin and not-pumpkin!

It’s too bad; it seems Cinderella might have had a handle on neutrino oscillation, and yet all people know her for are her shoes.

Honorable mentions

Three more readers earned a symmetry honorable mention for their entries:

  • David Boehnlein, who started his great contribution with the line, “Imagine a pitcher hurling a baseball from the mound and the batter seeing a golf ball cross the plate;”
  • Bruce Howard, who took the initiative to make an “explain it in 60 seconds” style video comparing neutrinos to shape-shifting billiard balls;
  • Alvaro De Rújula, who used “the cow oscillation paradigm” to describe the manner in which neutrinos change flavors.

This last one merits further explanation.

In De Rújula’s metaphor, two identical Swiss passenger trains, traveling side-by-side, offer through their aligned windows a view of cows in the Swiss countryside. However, one train, holding a larger number of passengers, starts to drag, causing it to fall behind. As the faster train passes the slower one, the windows of the two trains come in and out of alignment. When the windows align, an observer sees the cows; when they do not align, the cows are out of sight.

The cows are always there. But whether or not the observer can see them depends on the point on the journey at which the observer takes a look. In the same way, a neutrino always has the potential to be any of the three flavors; the flavor it takes on depends on the point at which it is observed.

We wanted to give De Rújula the “thinking most like a physicist” prize, but it turns out that wouldn’t be fair; he is a physicist.

Thanks to everyone who entered the contest, and a special mention for Kyle Simpson, who pointed out an excellent related video on the Veritasium YouTube channel.

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