Andrea Minini

NATURE gives rise to weird and wonderful things: dancing plants, sailing stones, flamingos. But no one, except perhaps on a hallucinogenic trip, has seen a flamingo melt into a wave or split itself into multiple copies. And that may be the weirdest thing of all, since our best theory of nature seems to suggest those things could happen.

That theory is quantum mechanics. Despite its spectacular success accounting for the bizarre behaviour of subatomic particles, it’s not clear how, or even if, it can explain why much larger bodies don’t behave in a similarly strange way. This is one reason why Einstein, among others, never accepted quantum theory as the ultimate description of nature.

Now a new experiment has seen a hint that these quantum critics may be right. The result must still be corroborated by many other tests, some now getting under way, but there’s no overstating the significance if it is shown to be correct. “It would be revolutionary,” says physicist and Nobel laureate Anthony Leggett at the University of Illinois at Urbana-Champaign. “It would shatter the notion that quantum mechanics is the whole story about the physical world.”

The real problem with quantum mechanics is simply stated. “What the hell is it about?” says physicist Sheldon Goldstein of Rutgers University in New Jersey. Quantum mechanics describes subatomic particles using undulating mathematical objects called wave functions, which evolve smoothly over time. A particle described by a wave function is more potentiality than point. It exists in superposition, meaning, roughly, that it is smeared out in space or is in many places at once. How …