In physics the so-called Correspondence Principle, put forth by Niels Bohr, says that the quantum world has to mesh smoothly with the universe of everyday experience. Anything you figure out using quantum mechanics eventually needs to correspond to ordinarily observed properties of macroscopic bodies.

Electrons and protons can act weird, for instance — they're tiny and they don't know any better. But if you get enough of them together to approach the "classical limit" then they've gotta start doing what we know bulk matter normally does. At ultralow temperatures or ultrahigh densities it's all right for strange activities like superfluidity and superconductivity to occur. Just don't let it happen in the streets, please! In the same way, relativistic phenomena are hunky-dory for things going near the speed of light, or for supermassive astrophysical objects. But at slower velocities and for commonplace materials the laws of relativity need to produce the results that we all know and love.

In other words, an exotic environment can evoke exotic events — but theories that explain such exotic events must nevertheless work in ordinary surroundings, where our prejudices from daily life remain valid.

And turning now to the topic of interpersonal interaction, some free-association on Bohr's Correspondence Principle leads me to concoct a not-altogether-unrelated but much-more-mundane rule of thumb: when exchanging letters with a friend, write twice for every reply you hope to get.

Sure, you shouldn't need to; a decent party at the other end of the pipeline ought to respond whenever you send out a ping. But messages get lost or misplaced, and daily distractions cause many return notes to remain forever unwritten. Extraordinary events excuse many sins. People do have a princely side. They mean to do well, but sometimes you need to tug at them a bit to make that inner nobility surface.

So give your correspondent's prince a pull ...

(see also TitForTat (31 Oct 1999), InvisibleDifferences (8 Nov 1999), QuantumNondemolition (5 Feb 2000), TwoFaces (10 Feb 2000), No Concepts At All (22 Feb 2001), ScientificRevolutions (16 Aug 2002), ...)

TopicScience - TopicHumor - 2003-03-04

(correlates: Comments on Unknown Knowns, Geons, Black Holes, and Quantum Foam, SelfImprovement, ...)