Uncertainty principle

ΔpΔq ≥ ħ/2*

In 1927, Heisenberg wrote a landmark paper in which he called the tenets of classical physics into question. Physicists had believed that it was possible to predict the behaviour of a system infinitely, provided that the initial system had been measured with infinite precision. In contrast, Heisenberg stated that the more precisely the position of a quantum particle is determined, the less precisely the momentum is known in that instant. In other words, because it is impossible to measure the initial state of the system with unlimited precision, we cannot calculate exactly what a quantum particle will do in the future. Taken a bit further, the principle implies that the past and future events of quantum particles are uncertain.

What, if anything, does the Heisenberg uncertainty principle have to do with the practice of family medicine? Perhaps nothing. After all, the principle is based in the world of subatomic particles, in contrast to the macroscopic (and microscopic) world in which we live. Maybe the world we see has a different set of rules. A more predictable set of rules. Some scientists, however, postulate that the line between the subatomic and macroscopic worlds is blurred. They think the rules governing the subatomic world might also be at play in our macroscopic world of trees, streams, people, and butterflies.

I once had a frail elderly patient in a geriatric hospital. Late one night she suddenly went into profound septic shock. The nurses and I did everything we could to reverse the shock, but it became quite clear by midmorning that our efforts were futile. No blood pressure. No urine. I met with the family and explained the bad news. By the middle of the afternoon, however, she had a measurable blood pressure. By early evening she was producing urine, and by the time I left for home that evening, she was eating a snack. Why did she survive? I don’t know. By the rules of our macroscopic world, she should have died. But by the rules of the quantum world, who knows?

Several articles in this issue of Canadian Family Physician take a novel look at family medicine. Bawa ( page 386) further explores the relationship between quantum physics and the practice of family medicine, focusing on uncertainty and probabilism. Smith ( page 496) describes the difficulties of dealing with uncertainty in day-to-day practice, and Reynolds ( page 385) turns the whole idea of “hard knowledge” in medicine upside down.

Challenging ideas. Worth a read.

• Copyright© the College of Family Physicians of Canada