Friday, October 18, 2013

Digging too deeply into a Heisenberg (Physics not crystal meth) joke

Some days ago I saw and retweeted this joke:
Police officer: "Sir, do you realize you were going 67.58 MPH?
Werner Heisenberg: "Oh great. Now I'm lost."
Ok, it's a funny joke, provided you have a passing acquaintance with basic physics.

But here's my problem: a lot of people who kinda-sorta understand that joke have no idea what's really behind it. And that's a problem I've had for a while now with the "science fanclub that cannot do basic science" as I call them. (The people who think that Surely you're joking Mr. Feynman is a physics book and like to watch soap opera biographies of scientists, heavy on the drama, light on the actual science.)

[Added later] My problem with these people is that they perceive science as something that comes from authority and must not be questioned or further investigated by others. For example, they "know" that the position and the velocity of an elementary particle cannot be jointly determined with arbitrary precision; but when pressed about how they know that, they say something about "Cosmos" or mention a Richard Dawkins book (which of course would not cover this); they behave as acolytes to those they recognize as high priests of science, who – presumably – are anointed by a Council of Wise Ones. That's precisely the opposite of what gave science its success, the idea that anyone can question received wisdom and experiment or observation are the ultimate arbiters of correctness. [End of addition.]

A simplified form of Heisenberg's inequality, good enough for our purposes, is

$\qquad \Delta p \, \Delta x \ge h $

Going by orders of magnitude alone, assuming that the mass of Heisenberg plus car is in the order of 1000 kg, and noting that the speed is given to a precision of 0.01 mi/h, an order of magnitude of 10 m/s, with $h \approx 10^{-34}$ Js, we get a $\Delta x$ of the order of

$\qquad \Delta x  \approx \frac{ 10^{-34} }{10 000} = 10^{-38}$ m.

That's a lot of precision to consider oneself lost. For comparison, the width of a typical human hair is in the order of 10-100 micrometers, or $10^{-5}$ to $10^{-4}$ m.

Yes, these numbers show how stupid it would be to use Heisenberg's Uncertainty Principle for macroscopic observations. That's the joke; the fact that many members of the science-fanclub have no idea of the magnitudes involved but like to lord their science-fandom over others is part of my irritation.

I see this all the time in my job, with people who can't write Bayes's formula talking loudly about graphical models (should really be graphal models, BTW, since they are based on graphs, not graphics).