Until physicists definitively answer these questions, they can’t really be said to understand quantum mechanics — thus Feynman’s lament. Which is bad, because quantum mechanics is the most fundamental theory we have, sitting squarely at the center of every serious attempt to formulate deep laws of nature. If nobody understands quantum mechanics, nobody understands the universe.

You would naturally think, then, that understanding quantum mechanics would be the absolute highest priority among physicists worldwide. Investigating the foundations of quantum theory should be a glamour specialty within the field, attracting the brightest minds, highest salaries and most prestigious prizes. Physicists, you might imagine, would stop at nothing until they truly understood quantum mechanics.

The reality is exactly backward. Few modern physics departments have researchers working to understand the foundations of quantum theory. On the contrary, students who demonstrate an interest in the topic are gently but firmly — maybe not so gently — steered away, sometimes with an admonishment to “Shut up and calculate!” Professors who become interested might see their grant money drying up, as their colleagues bemoan that they have lost interest in serious work.

This has been the case since the 1930s, when physicists collectively decided that what mattered was not understanding quantum mechanics itself; what mattered was using a set of ad hoc quantum rules to construct models of particles and materials. The former enterprise came to be thought of as vaguely philosophical and disreputable. One is reminded of Aesop’s fox, who decided that the grapes he couldn’t reach were probably sour, and he didn’t want them anyway. Physicists brought up in the modern system will look into your eyes and explain with all sincerity that they’re not really interested in understanding how nature really works; they just want to successfully predict the outcomes of experiments.

This attitude can be traced to the dawn of modern quantum theory. In the 1920s there was a series of famous debates between Einstein and Niels Bohr, one of the founders of quantum theory. Einstein argued that contemporary versions of quantum theory didn’t rise to the level of a complete physical theory, and that we should try to dig more deeply. But Bohr felt otherwise, insisting that everything was in fine shape. Much more academically collaborative and rhetorically persuasive than Einstein, Bohr scored a decisive victory, at least in the public-relations battle.

Not everyone was happy that Bohr’s view prevailed, but these people typically found themselves shunned by or estranged from the field. In the 1950s the physicist David Bohm, egged on by Einstein, proposed an ingenious way of augmenting traditional quantum theory in order to solve the measurement problem. Werner Heisenberg, one of the pioneers of quantum mechanics, responded by labeling the theory “a superfluous ideological superstructure,” and Bohm’s former mentor Robert Oppenheimer huffed, “If we cannot disprove Bohm, then we must agree to ignore him.”

Around the same time, a graduate student named Hugh Everett invented the “many-worlds” theory, another attempt to solve the measurement problem, only to be ridiculed by Bohr’s defenders. Everett didn’t even try to stay in academia, turning to defense analysis after he graduated.