📏 #2 answers: Weird Units Day

The 'hand' unit was fixed at exactly four inches by a law that King Henry VIII passed about horses.

Horses are still measured in hands in many English-speaking countries.

“It was standardised at four inches by a statute of King Henry VIII, the Horses Act 1540 (32 Hen. 8. c. 13), but some confusion between the various types of hand measurement, and particularly between the hand and the handsbreadth, appears to have persisted.”

The unit of distance called a furlong gets its name from the Old English words for 'furrow' and 'long'.

It was once the length of a furrow in a ploughed field.

“The name furlong derives from the Old English words furh (furrow) and lang (long).”

Carob seeds were used for centuries to weigh jewellery because people believed every seed weighed the same.

They don't, but the idea gave us the word 'carat'.

“Carob seeds have been used throughout history to measure jewelry, because it was believed that there was little variance in their mass distribution.”

A morgen, an old Dutch and German unit of land, was the area a farmer could plough in a single morning.

'Morgen' simply means 'morning' in Dutch and German.

“The word is identical to the German and Dutch word for "morning" because the measurement was determined by the area that can be ploughed with a single-furrow horse or ox plough in one morning (measured from morning to noon).”

In the Middle Ages a 'moment' was an actual unit of time, lasting about 90 seconds on average.

It was based on the shadow on a sundial, so its exact length changed with the seasons.

“The length of a solar hour depended on the length of the day, which in turn varied with the season, so the length of a moment in modern seconds was not fixed, but on average, a moment corresponded to 90 seconds.”

The 'beard-second' is a joke unit of length: the distance an average beard grows in one second.

It's handy for describing the tiny parts inside computer chips.

“It is the length an average beard grows in one second.”

Geologists have a unit called the Bubnoff for very slow processes, equal to one millimetre per 1,000 years.

It is used for things like erosion and land rising, which happen at a crawl.

“The Bubnoff unit is defined as 1 micrometre per year (3.169×10−14 m/s), or one millimeter per 1,000 years.”

In 1926 a 'jiffy' was proposed as the time it takes light to travel one centimetre, about 33 picoseconds.

The chemist Gilbert Newton Lewis suggested it, so 'in a jiffy' can be very fast indeed.

“He proposed in 1926 a unit of time called the "jiffy" which was equal to the time it takes light to travel one centimeter in vacuum (approximately 33.3564 picoseconds).”

Physicists' tiny unit of time called the 'shake' is named after the saying 'in two shakes of a lamb's tail'.

One shake is just 10 nanoseconds.

“The word "shake" was taken from the idiomatic expression "in two shakes of a lamb's tail", which indicates a very short time interval.”

Nuclear physicists named a unit of area the 'barn' partly as a joke that it was 'really as big as a barn'.

A barn is tiny to us, but huge compared with the targets particle physicists aim at.

“But this latter association, combined with the "rural background" of one of the scientists, suggested to them the term "barn", which also worked because the unit was "really as big as a barn".”