The beard-second, the barn and 4 other humourous units of measurement

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Can you use a man to measure a bridge? What’s your bacon with the US President? What’s a beard-second? Can you hit the broadside of a barn with a particle accelerator? How much power is in a donkey?

A Vernier Calliper – Photo Credit: Simon A. Eugster

Units are a fundamental component of science. Without units, you have no measurements and without measurements you have no experiments. We are all familiar with the basic units of science, the metre, the Kelvin, the kilogram, etc.

However, there are others, sometime less useful units, that show that scientists do occasionally like their funny bone tickled.

The beard-second

Ah, the beard. Follicular manliness. Just look at the guy below, glorious!

Did you know that the only member of ZZ Top who doesn’t have a beard is called Frank Beard? – Photo Credit: Craig ONeal

The beard-second is a facetious unit of distance inspired by the light-year (the distance light travels in a year) and is defined as the amount the average beard grows in a second. One beard second is equivalent 100 angstroms or 10 nanometres. Google even accepts it as a unit, though it defines it as 50 angstroms. According to google, a ten day beard would be 4.3 mm long.

The Smoot

Oliver R. Smoot was a freshman at MIT in 1958. His fraternity brothers made him, as a pledge, measure the Harvard Bridge (connecting Boston and Cambridge, Massachusetts) using his height. He lied down on the bridge and a chalk line was drawn where the tip of his head was. The process was repeated, and the bridge was measured to be 364.4 smoots plus or minus one ear (one smoot in approximately 1.7 m). At first he would get up and lie down himself, but he soon got tired of all the exercise and his frat brothers picked him up and moved him for each measurement.

Plaque at MIT commemorating the 50th anniversay of the prank – Photo Credit: Dayan Paez

There are smoot measurements markings on the bridge, repainted every semester by the new members of the fraternity. Halfway through the bridge there is a graffiti with the measure in smoots (182.2), the words “Half-way to Hell” and an arrow pointing towards the end of the bridge leading to MIT. When the bridge was renovated in the 1980s the graffiti were kept and the contractors that renovated the bridge marked the concrete blocks of the bridge in 1.7 metre (5 foot 7 inches) increments, instead of the usual 6 feet.

Fittingly, Smoot became the head of the American National Standards Institute (ANSI) and then of the International Organisation for Standardisation (ISO), which oversee standards including units of measurement.

Google Maps and Google Earth let you calculate distances in Smoots.


Not technically a unit, the Bacon number measures the interconnectedness of people. For example, you and a friend have a Bacon number of 1, you and a friend’s friend have a Bacon number of 2, etc.

The name of this number does not come from the pork product or the English philosopher but from Mr Footloose himself, Kevin Bacon. In the popular game “Six degrees of Kevin Bacon” the goal is to link any actor to Kevin Bacon in less than 6 connections, with the appearance of the two in a film or a commercial valid as a connection. You can search for any actor’s Bacon number in Google since 2012.

It was hypothesised by Frigyes Karinthy that all people in the world are 6 degrees of separation from each other, you can chain friend-of-a-friend connections and reach anyone in the world in less than 6 steps.

Not this kind of Bacon, though now I’m hungry

In 2011 Facebook used its database of (at the time) almost 800 million users to determine their degrees of separation. They found that the average degree of separation, or Bacon number, was 4.74, while the maximum was 12.

The Dirac

Paul Dirac was one of the most important theoretical physicists of the 20th century. He predicted the existence of antimatter and formulated the Dirac equation, which describes the behaviour of fermions, as well as lending his name to the Dirac delta function. He won a Nobel prize in 1933 for his work.

However, he was not the most talkative man. His colleagues at Cambridge University coined a humourous unit to describe how taciturn he was. The Dirac is a measure of talkativeness defined as 1 word per hour. So for example, my ex-girlfriend Dirac measure would be around 10 to the power of 15.

Paul Dirac not looking directly at the camera


The Barn is actually used as a unit by experimental physicists to measure area. A very tiny area. One barn is equal to 10-28 m2 or 0.00000000000000000000000000001 m2. It’s so tiny as it was originally used to measure the cross sectional areas of  atomic nuclei. These days it is also used to express the cross-section of a scattering process.

It is named after the folk expression “couldn’t hit the broadside of a barn”, as it was always quite difficult to get particles to collide in particle accelerators. The Barn has spawned a couple of other units such as the outhouse (10-34 m2) and the shed (10-52 m2), though they are rarely used.


Donkeypower is a whimsical  measure of power defined as approximately 250 watts, a third of a horsepower, since, you know, donkeys are weaker than horses.


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