Units: The Americans Have It Right

If you wanted a measure of American assimilation, adherence to imperial/customary units (miles, Fahrenheit, etc.) and the month-day-year system of record would be a good place to start. What follows is a defense of these three American customs that so often become flashpoints in the most Caltech of dinner table conversations.

The following unitary arguments are grounded in common sense, meant for quotidian chit-chat, not to clarify a gluttonous trend toward evermore obtuse scientific convention. Richard Feynman famously bemoaned “the idiocy of all the different units which [physicists] use for measuring energy.” Thankfully today the Système international (SI) and her seven base dwarves permeate across most modern literature, after years of redefinition and tinkering. Anything other than a combination of these base units, tidied up with standard form, warrants an academic red flag. Metric prefixes are passable for verbal discussion but their ad hoc employment of capitalization (e.g. kilo- vs Mega-) makes for ugly reading.

Of course, it would be remiss of me to ignore the holy grail of all units: namely the dimensionless or unitless number. Unshackled from the bonds of human-centric expression, free from confusion of language or historical inertia, dimensionless quantities such as Mach number or refractive index convey physical meaning, not an isolated measurement. Science will never claim to stand in the divine realm of Kronecker’s and Hawking’s integers, but at least dimensionless numbers are a prize we humans can unambiguously show off to the rest of the universe.

OK, now less lofty and more Red Door debate. Rule 1: the appropriate choice of unit maximizes the human-centric, full-scale range. Given the inclement weather of late (c.f. Vol. CXXVII, Issue 9), let us apply this rule to temperature and how best to report it.

Temperature emerges from the daily ménage à trois of the Earth’s surface, cloud cover, and solar severity. Unless you happen to be a professional baker, temperature and weather are inextricably linked and therefore placing anything other than the human-meteorological experience as the basis of this measurement is pure catering to the kettle.

For the median human, life is lived somewhat confined to a 0–35°C regime (meet your opponent in their echo chamber and waltz them over to your beat). I submit that such a span is insufficient to describe the subtleties of our temperate reality. Exams are marked 0–100%; human lives stretch ~100 years; childhood confectionery (at least in my day) is priced between 0–100 pennies; gym dumbbells run 0–100 lb. Save O(1) precision for a hinge date description; save O(100) discretization for batting averages. But O(10) descriptions are perfect for your everyday means.

And thus spoke Fahrenheit: the temperatures of life fit between 0–100°F. Those who tout the intuitiveness of a water-centric temperature scale are charlatans, or French, or both.

Rule 2: if there exists no significant full-scale range advantage, units should be selected on an aesthetic basis. Kilometers vs miles is the quintessential use case of such a rule and I am afraid, dear reader, that the Americans have it right once again.

Everybody and their advisor is running. Now if you have ever had the (mis)fortune of asking a runner about their running, they’ll tell you pace is the currency of their personality. You run fixed distances, with variable speeds yielding variable minutes.

If you subscribe to kilometers — and you are reading a California Tech article — you are probably confined to a pacing of 4:XX minutes per kilometer. The four becomes default and just takes up an obsolete digit of information. However, for us minutes-per-mile-ers, we have 6:XX, 7:XX and 8:XX all at our disposal. Furthermore, talking in kilometers represents a fundamental misunderstanding of the geometric progression of running distances: 100, 200, 400, 800 —— fill in the blank. Finally, imagine you’re running, panting, verbally not at your best. How long is it until the end? “One-point-two kee-low-mee-ters” you splutter back. The Proclaimers didn’t walk 500 kilometers, now did they? Stick to miles: one syllable of aesthetic sensibility.

Rule 3: convey maximal information in minimal duration. The final argument is on song with both our previous musings but is applied here to a clarification of date etiquette. I believe only a month-day-year system of record satisfies rule three. I hear your Pavlovian cries, bemoaning a non-ascending description of time. But I beg you apply a morsel of critical reasoning to your instincts. Ask why much of Eastern Asia speaks in year-month-day: chronological yes, but now descending in scope. Ask when, and for what purpose, do we report a three-step date? Next Caltech Rugby Session? — the following Wednesday (6:30 p.m., South Field). New Frank Ocean album? — oh probably sometime next decade. Both days and years have their place but if you are going to give the full three-step specification, the month is the most useful piece of information and therefore should be placed in pole position. It serves to guide the recipient as to where the priority of retention should be directed, and perhaps the expediency with which they have to buy their fancy dress costume for your next party.

The dichotomies I’ve presented are much akin to picking between your favorite Olivias: Dean or Rodrigo. Do you want range and soul that speaks to the depth of the human condition (Fahrenheit) or do you want to reduce life to a never-ending breakup ballad measured in Swiftian soundbites (Celsius)? Do you want the punchy, monosyllabic Dean (miles) or the oft-tangled Rodrigo (kilometers)? Has the precise Dean already given you the time and place, or has the vague Rodrigo just gotten [her] driving license last week? Despite what my Apple Music Replay might tell you, the choice couldn’t be clearer.

In sum: 996 words of wisdom, 49 bucks I’ll someday receive and 5 minutes you’ll never get back again. I hope you speak quantitatively of this article to your friends; I’ll leave the appropriate choice of unit as an exercise to the reader.