Brunos and Smoots

We recently spent a lecture in my first year engineering course introducing the concepts of units, unit systems, and unit conversions. We talked about meters and feet. We discussed kilograms and slugs, pounds mass and pounds force. We even talked about esoteric units like furlongs and fortnights. But I realized afterward that I’ve short-changed their education by not mentioning two important engineering units: the bruno and the smoot. Both these units were created by (and named for) undergraduate students at the Massachusetts Institute of Technology (MIT).

Image by Jason Eppink via flickr (CC BY 2.0)

Image by Jason Eppink via flickr (CC BY 2.0)

A smoot is a unit of length. One smoot is equal to 67 inches (170.18 centimeters) which was the height of Oliver Smoot in October of 1958. While pledging a fraternity, Smoot was forced to lay down repeatedly on the Harvard Bridge while his fellow pledges used his body to measure its length. Chalk was used to mark each smoot, and every ten smoots a line and marker were painted onto the bridge. Smoot was chosen because he was the shortest but also because his name had a certain scientific ring to it. This proved to be prophetic. [1]

The prank also had a practical value. The fraternity house was on the opposite side of the Charles River from the MIT campus. The bridge itself is over half a kilometer. It can be a long, cold walk to class and during inclement weather (like fog or snow) it can be difficult to tell exactly where you are. The smoot marks served as a gauge to your progress. But not just in 1958. Repainting the markers became an annual tradition for Lambda Chi Alpha.[2]

The smoot is a legendary unit, both in the Boston area and in geek circles. When the bridge was renovated, rather than score the sidewalk at the standard six-foot intervals, the city put the breaks every 67 inches. Googling the term “5 feet in smoots” will return the converted distance.

While the bruno may not be as popular, it makes up for it by the audacity of its experimental derivation. Officially, the bruno is defined as follows:

A unit of volume equal to the size of the dent in asphalt resulting from the free fall of an upright piano. Determined to be 1158 cubic centimeters when the experiment was first performed in 1972.[3]

This first drop was performed from the roof of MIT’s Baker House and was the brainchild of Charles Bruno. The event —which, it should be noted, always involves a non-working piano— has been celebrated periodically since 1972. The most recent drop was in April 2015.

You can see footage of the inaugural piano drop and its aftermath in this YouTube video:

In a wonderful footnote to these events, Oliver Smoot’s experience on the bridge served him well during his career. After graduating from MIT in 1962, he studied law at Georgetown. He later became chairman of the American National Standards Institute (ANSI) and the president of the International Organization for Standardization (ISO).[4]

Oh, and for those who are curious, the Harvard Bridge is 364.4 smoots (± 1 ear) long.


  1. ^ David A. Fahrenthold, “The Measure of This Man is in the Smoot”, Washington Post, December 8, 2005. <>
  2. ^ “Smoot, Namesake of a Unit of Length, Retires”, All Things Considered, December 7, 2005. <>
  3. ^ Matt McGann, “Have Your Cake & Drop Date Too”, MIT Admissions, April 28, 2006. <>
  4. ^ “Speaker Bureau”, ANSI website. <>

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