Shut up and calculate!

Quantum mechanics is confusing. Little by little you wrap your head around the math, just going with the assumption that objects are simultaneously particles and waves, until you feel like maybe there’s something to all those wavefunctions and probabilities. Then you ask what it all means. The confusion rushes back as your professor shrugs.

In the 1920s, the founders of quantum mechanics gathered together in Copenhagen, Denmark to discuss what their math said about the physical universe. In the end, they decided there are fundamental limits to what we can know. They came up with the Copenhagen Interpretation, which according to physicist David Mermin of Cornell University means “shut up and calculate!”

Everyone accepted the Copenhagen Interpretation—if the inventors of the theory aren’t quite sure what it means, how are you supposed to know?! But a small group of scientists aren’t content with the ambiguity of quantum mechanics. With the right perspective, they argue, the meaning will become clear.

The Perimeter Institute for Theoretical Physics is hoping to find clarity. As Christopher Fuchs, one of the Institute’s researchers, says the right perspective will “write a story—literally a story, all in plain words—so compelling and so masterful in its imagery that the mathematics of quantum mechanics in all its exact technical detail will fall out as a matter of course.”

Fuchs is proposing the probabilities inherent in quantum mechanics come from the viewer, not from the object itself. He’s designed a new approach called QBism that, using a type of statistics called Bayesian inference, gets rid of the wavefunctions, amplitudes, and Hilbert-space operators—all necessary in quantum mechanics—and replaces them with simple probabilities.

All in all it’s pretty exciting. I’ve been interested in quantum mechanics and what it really means since I was old enough to realize that we, as scientists, don’t really know everything about the universe. It will be a good day when we can explain the meaning of quantum mechanics to elementary school students in an interesting and understandable story. Maybe QBism will give us that story.

3 thoughts on “Shut up and calculate!

  1. I like your blog. It’s rich and enthralling and diverse. Your Categories list is pretty awesome, but I do notice one thing missing:


    You should have a math category.


    That math guy with the WordPress about math. 😛


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