The geeks at the Massachusetts Institute of Technology are fond of merry japes, locally known as “hacks”. One of the more memorable happened one night in October 1958 when an MIT fraternity had the idea of initiating new members by making them measure a bridge over the Charles River connecting the Cambridge campus with Boston. Crossing the bridge was often a wet, windy and unpleasant business and it was thought that students returning at night from downtown would like to know, by visible marks and with some precision, how far they still had to go. The older fraternity brothers decided to use one of the new pledges as a rule, and selected Oliver R. Smoot, the shortest of the lot at 5ft 7in. The other pledges laid Smoot out at one end of the bridge, marked his extent with chalk and paint, then picked him up and laid him down again, spelling out the full measurement every ten lengths, and inscribing the mid-point of the bridge with the words “halfway to Hell”. In this way, it was determined that the span was 364.4 smoots long, “plus or minus one ear” (to indicate measurement uncertainty).
The hack was too good to let fade away, so every now and then the fraternity makes its pledges repaint the markings. You might think this isn’t the sort of vandalism the police would tolerate, but they do. The smoot markings soon became convenient in recording the exact location of traffic accidents, so (as the story goes) when the bridge walkways needed to be repaved in 1987, the Massachusetts Department of Public Works directed the construction company to lay out the concrete slabs on the walkway not in the customary six-foot lengths but in shorter smoot units. Fifty years after the original hack, the smoot markers have become part of civic tradition: the City of Cambridge declared 4 October 2008 “Smoot Day”. MIT students ran up a commemorative plaque on a precision milling machine and created an aluminium Smoot Stick which they deposited in the university’s museum as a durable reference standard: the unit-smoot is now detached from the person-Smoot. Through the legions of MIT graduates driving global high-tech culture, the smoot has travelled the world. If you use Google Earth, you can elect the units of length in which you’d like distances measured: miles, kilometres, yards, feet – and smoots.
Robert Crease, The Historic Quest for an Absolute System of Measurement, 2011.
January 5, 2022
QotD: Measurement hack that lives on
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