This teacher resource is a collection of unusual measurement units not in common usage but of interest to those fascinated by the unusual.

Student activities can be developed from some of the ideas presented, and by the end of such activities, students should be able to:

- understand the need for a simple, coherent and universal system of measurement
- realise that the human mind has a boundless imaginative capacity
- develop their own imaginative measurement system.

### Index

- Volume
- Mass
- Time
- Speed and power
- Computing
- Number
- New metric prefixes
- Related content and activity ideas

### Volume

**Mouthful **

This is about 28 mL and was once used to measure small volumes. Due to modern hygiene requirements, it is no longer in use!

**Olympic swimming pool**

The dimensions are 50 m long by 25 m wide by 2 m deep, so the volume is 50 x 25 x 2 = 2500 m^{3}. The volume of pure water flowing through the Huka Falls on the Waikato River often approaches 220,000 litres per second – this is enough water to fill an Olympic-sized swimming pool every 10 seconds!

### Mass

**Grain**

This is based on the seeds of cereal crops like wheat or barley. It is now taken to be 64.8 mg. It has been used to measure small masses in medicines, gemstones and precious metals.

**Carat**

This is a measure of how heavy a diamond or other gemstone is. It is now defined as 200 mg. ‘Carat’ also has a purity meaning when dealing with the precious metal gold. Pure gold is 24 carats, and 18 carat gold is 18 parts gold and 6 parts other metals, making it 75% pure.

### Time

**Moment**

In medieval times, the moment was 1/40 of an hour – 1.5 minutes. Next time you say “Wait a moment,” you have exactly 1.5 minutes to respond.

**Warhol**

Andy Warhol was a famous American ‘pop’ artist. He coined the expression “15 minutes of fame”. One Warhol is 15 minutes!

**Jiffy**

“I'll be back in a jiffy” is an informal term for a short period of time. In computing, a jiffy is the duration of one tick of the computer’s clock which is 0.01 seconds.

### Speed and power

**Knot**

The knot (kn) is a unit of speed still used in meteorology as well as maritime and air navigation. An aircraft or vessel travelling at 1 knot along a meridian travels 1 minute of geographic latitude in 1 hour. The take-off speed of a 747-400 plane is 160–180 knots. 1 kn = 0.514 m/s.

**Jerk**

In social circles, a jerk is an annoyingly unlikeable person, whereas in engineering, a jerk is defined as the rate of change of acceleration. It has the unit of m/s^{3}.

**Horsepower**

Originally defined to compare the output of steam engines with the power of draught horses, the horsepower (hp) is still commonly used. The SI unit for power is the watt (W), and 1 horsepower equates to 746 W. A 2-litre car engine with a power output of 148 horsepower is equivalent to 110 kilowatts.

### Computing

**Mickey**

Named after the cartoon character Mickey Mouse, the mickey is the length of the smallest detectable movement of a computer mouse. It is 0.1 mm.

**Byte**

Computers store information in binary code, which consists of a stream of 1s and 0s. Each 1 or 0 is known as a ‘bit’, and 8 ‘bits’ make up a byte. The letter A is stored as 1 byte made up of the 8-bit pattern 01100001.

**Nybble**

This is a set of 4 bits. Since there are 8 bits in 1 byte, a nybble is half of 1 byte. While it may take the average person several nibbles to equal one bite of a biscuit, in computing, 2 nybbles always equal 1 byte.

**Exabyte**

An exabyte is over 1 quintillion bytes. One gram of DNA can hold 490 exabytes. (For reference, 1 exabyte can hold the entire Library of Congress 3,000 times.)

### Number

**Googol**

A googol is the large number 10^{100}. In 1938, American mathematician Edward Kasner asked his nephew to come up with a name for a very large number – googol was the answer, and Kasner defined it as 10^{100}. The company name ‘Google’ was chosen by founders Page and Brin as a misspelling of googol.

**Baker’s dozen**

In 13th century England, if bakers were caught cheating customers, they were punished by having a hand chopped off with an axe. To guard against this, it became common practice to put in an extra loaf when a customer bought a dozen (12), so a baker’s dozen is 13.

**Apgar**

Immediately after birth, newborns are given an Apgar score. This score evaluates the health of the newborn based on appearance, pulse, grimace, activity and respiration. The score ranges from 0 to 10.

## New metric prefixes

In November 2022 international scientists voted for new metric prefixes to express the world's largest and smallest measurements, prompted by an ever-growing amount of data. This is the first time since 1991 that new prefixes have been added to the International System of Units (SI).

Welcome to ronna and quetta for the largest numbers – and ronto and quecto for the smallest.

## Related content

Read about earlier measurement systems – from the Babylonians to more recent European systems. An interactive timeline will take you through many of the significant milestones. Māori had their own measurement standards for building, carving and weaving.

How long is it? is a collection of length measurements found within the Science Learning Hub.

Explore the microscopic scale in this interactive diagram, showcasing examples from the Science Learning Hub.

## Activity idea

Use the activity Cubits, spans and digits to reinforce the degree of uncertainty when using non-SI measurements.

## Useful link

As computing processing power increases, the amount of data we consume and store also increases. Find out about the numbers involved in the article Terabytes, Gigabytes, & Petabytes: How Big are They?