Since the dawn of civilization, we have needed ways to define and quantify the world around us, to conduct trade, build homes, and explore further. To do this, we need to agree on the way we measure the world, we need to agree on the units. While we no longer use the size of the king’s nose or the number of doughnuts a pregnant duck can eat to quantify things, and instead rely on carefully defined standards sweated over by the world’s best metrologists (measurement scientists), people have invented some wild and wacky ways of figuring out how much of something there is. Here are some of my favourite weird units of measurement.


First on my list, the helen, because it made me laugh.

The helen is a reference to Helen of Troy, the “face that launched a thousand ships”. One millihelen is the amount of beauty needed to launch one ancient Greek warship.

American author David Goines has further standardized the helen scale, defining a picohelen to be the amount of beauty required to “barbecue a couple of steaks and toss an inner tube in the pool”, while a terahelen will “launch the equivalent of one quadrillion Greek warships and make serious inroads on the welfare of the galaxy”.


The beard-second is a unit of length inspired by the light-year, but is considerably shorter. It is defined as the average length a beard grows in one second. Some sources define this length to be equivalent to 10 nanometres (about the size of a virus), but Google defines a beard-second to be 5 nanometres. I think Google’s measurements of average beard growth may include women.

As stupid as it sounds, beard-seconds would actually be useful in applications related to nanotechnologies such as integrated circuits.

My sternum is about 15 beard years from my chin.


A smoot is a unit of length equivalent to the height of Oliver R. Smoot when he was a college freshman in 1958 (170 cm). As part of Smoot’s initiation to the Lambda Chi Alpha fraternity, Smoot and other freshmen were tasked with measuring the length of the Harvard Bridge by laying Smoot on the ground and using him as a yardstick.

They found the bridge to be 364.4 smoots long, plus or minus an ear. Smoot’s fraternity brothers also painted marking on the bridge at roughly 10 smoot intervals.

Smoots have turned out to be surprisingly useful. When the bridge was renovated in the 1980s, the local police asked that the smoot markings be maintained because they were useful markers for indicating the position of an accident on the bridge.

Google, of course, recognises the smoot as a unit of measurement.

Smoots make the list because Oliver Smoot himself took up a career in metrology, and even became the chairman of the American National Standards Institute, so the smoot is a unit with some pedigree.

Metrology can be a real drag.

Pirate Ninja

This is probably my favourite unit in the list. The pirate ninja is a unit of power invented by author Andy Weir for his best-selling novel The Martian.

In The Martian, Weir’s hero, astronaut Mark Watney, has to carefully monitor and balance his daily power usage if he is to survive being stranded on Mars. Watney decides that “kilowatt hours per sol” (sol = Martian day) is annoying and cumbersome to say so decides he’ll call them “Pirate Ninjas” instead, making one pirate ninja equal to one kilowatt hour per sol.

The reason that pirate ninjas are probably my favourite unit is that the Mars rover teams at the Jet Propulsion Laboratory ACTUALLY USE THIS UNIT! Taking inspiration from The Martian, instead of talking about the Curiosity rover’s power generation and usage in terms of watthours per sol, they now talk in units of “millipirate ninjas”.

All this faffing about doesn’t make much sense to me though, because one kilowatt hour per sol is just a unit of power, and could be easily be converted to watts. One pirate ninja is equal to 40.6 watts. Pirate ninjas are more fun though.

Give me 5 millipirate ninjas and I’ll shoot this rock with a laser.


The shake makes the list because, although it’s not an official unit, it is actually used in practice. Equivalent to 10 nanoseconds, the shake is a reference to “two shakes of a lamb’s tail”. It was invented during the Manhattan Project developing the nuclear bomb because 10 nanoseconds is a convenient time interval for nuclear physicists, being roughly equal to the time taken for one step in a nuclear chain reaction.

Shakes might also be useful for signal propagation time in integrated circuits.


Unlike the rest of the units on this list, the barn is an officially recognized unit. Like shakes, barns come from nuclear physics and the Manhattan project and are used to quantify the cross-sectional area of atomic nuclei. It’s a reference to “couldn’t hit the broad side of a barn” and was originally coined to prevent eavesdroppers realizing that scientists were talking about nuclear reactions, but has become a standard unit in particle physics. One barn is roughly equal to the cross-sectional area of a uranium nucleus.

The nuclear physicists also took the analogy further, referring to microbarns as “outhouses” and yoctobarns (10-24 barns) as “sheds”.

The new nucleus is 1 barn wide plus or minus an outhouse…

The measure of things

While metrologists around the world work hard to carefully define and standardize the official SI units of measurement, this list shows that convenience and practicality, and a little bit of humour, will usually determine what and how a measurement is made. While I doubt we will be measuring milk in Hubble-barns and marathon times in microcenturies any time soon, imagination and creativity will continue to supply us with weird and wacky ways to measure the world around us. Though so far my colleagues have resisted all my attempts to define the power of our lasers in eye-meltyness…

One thought on “My Favourite Units

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