It’s a conundrum scientists need to solve because the kilogram is one of a few base units (like the second and the meter) that are used in the definitions of other, more complex units, such as those used to measure temperature, electricity or density. If the kilogram is off, even a little, critical measurements in science, engineering and commerce get messed up.[...]

The U.S. National Institute of Standards and Technology is backing a definition based on the Planck Constant, a number from quantum mechanics. It’s a more complex definition than a simple cylinder, but it’s unlikely to change over the next century.

Link | Image: Clipart

Humans like to measure things - distance, mass, time, you name it, we've measured it. And along the way, people have come up with some interesting and unusual units of measurements:

Apgar Score - If you were born in the past 50 years or so, chances are you have an Apgar Score. Indeed, it is the very first test all of us took. The Apgar Score was devised in 1952 by Dr. Virginia Apgar to evaluate the health of newborns immediately after birth, based on the Appearance, Pulse, Grimace, Activity and Respiration criteria. It ranges from 0 to 10. (Source)

atomus - In medieval time, the Latin Atomus meant "a twinkling of the eye," the smallest amount of time imagineable. Nowadays, it's defined as 1/376 minute or about 160 milliseconds.

Avogadro's number - Us common folks say a couple to mean 2, a dozen to mean 12, a gross to mean 144, and so on. Well, chemists have got us beat: they use Avogadro's number to mean 6.0221417930 x 10²³, the number of atoms or molecules in one mole. It was named after Italian scientist Amedeo Avogadro, who looked a little like a Hobbit.

baker's dozen - If you buy a dozen loaves of bread, bakers usually throw one in for free, so baker's dozen means 13. They didn't do this out of the goodness of their heart: the practice came to be in the 13th century, when a medieval English law made it so a baker could be punished by chopping his hand off with an axe if he was found to be shortchanging a customer. Tossing in an extra loaf of bread seemed to be a prudent way of keeping one's hand. (Source)

barn - Those nuclear physicists are a funny bunch. They define a "barn" (yes, from the saying "as big as a barn") as a cross section of an atomic nucleus. It is 10^-28 m². This unit of measurement is used when these physicists/comedians need to quantify the scattering cross-section of particles. An outhouse is defined as 10^-6 barn and a shed is 10^-24 barns.

baud (Bd) - With broadband Internet and all, we thankfully don't use this anymore, but anyone who's old enough to remember modems should know that baud (later supplanted by bit/second) is the measure of the rate of data transmission over telephone lines. The baud rate is the number of distinct symbols that can be transmitted per second. It is named after Emile Baudot, the inventor of the Baudot code used in telegraphy.

BB - Ever owned a BB gun? Well, BB doesn't stand for ball bearing or bullet ball, it actually referred to the size of the pellet. A BB pellet (0.180 inch or 4.57 mm) is between B and BBB size.

Big Mac Index - a measure of exchange rates (actually purchasing power parity) between two currencies. It was defined by Economist's editor Pam Woodall to measure whether a currency is under- or overvalued. She used a Big Mac because the burger is produced in about 120 countries. (Source)

The easiest way to explain this is by an example: say you want to know whether the exchange rate between the dollar and the British pound, say $2 = £1, is fair. You take the price of a Big Mac in the US ($3.57) and in Britain (£2.29). The idea is the price of a Big Mac should be equal in both countries, relative to their currencies - the implied purchasing power parity is 3.57/2.29 = 1.56. But the exchange rate is 2/1 - so this means that the pound is overvalued against the dollar by 28% (2 divided by 1.56).

blink - Oh, every few decades somebody proposed that instead of using 24 pesky hours, why not divide the day into units of 10. Basically 1 day is divided into 10 hours, each hour into 100 minutes, and each minute into 100 metric seconds or blinks. A blink works out to be 0.864 second, which ironically is twice the time it takes for you to blink your eye.

carat - A measure of how big a diamond is. The unit carat came from the Greek word keration meaning a carob bean, which was used as a standard weight in ancient Greece. It's now defined as 200 milligram.

cubit - A biblical unit of distance. It is the distance between a man's middle finger and his elbow. It is about 18 inches or 45 centimeters. A cubit is divided into 6 palms or 24 digits.

In Ezekiel 48: 34 it was written that the size of the New Jerusalem or heaven is 4500 cubits on each side. That translates to about 1,046 acres or 1.63 square mile - about 3/100th the size of San Francisco.

Needs more donkey power

donkey power - A third of a horsepower, about 250 watts.

farthing - An old English word for quarter. A farthing means 1/4 of a penny.

flock - Ever wonder how many birds are in a flock of seagulls? A flock means 2 score or 40.

fortnight - A fortnight is two weeks or 14 days. The 12th century word comes from "fourteen nights." Geeks have adopted this in a humorous way: instead of saying seconds, they say microfortnight (which comes out to be about 1.21 seconds).

Gillette - American physicists Ted Maiman, who made the first working laser, used to compare laser output power by how many Gillette razor blades it can burn a hole through. A 2 Gillette laser can only through 2 stacked razor blades.

googol - The googol was invented in 1938 by mathematician Edward Kasner, who asked his then 8-year-old nephew Milton Sirotta what he would name a really, really, really large number. A googol is a large number indeed: it is 1 followed by 100 zeroes or 10¹⁰⁰.

A year later, Kasner defined another number: the googolplex or 10^googol(10^{10^100}). How big is a googolplex? Carl Sagan estimated that it would be impossible to write out all the zeroes of the number, because it would take more space than the known universe.

If googol sounds familiar, that's because Larry Page and Sergey Brin named their company Google based on this word. They even called the Google headquarters in Mountain View, California, the Googleplex.

From the incomparable Adam "Ape Lad" Koford [Flickr]

Hobo Power - Radio personality Adam Carolla came up with this one: a measure of how bad something smells. It ranges from 0 (not stinky at all) to 100 (lethal). A "robust fart" is about 13 hobo. At 50 hobo, the person doing the smelling would projectile vomit.

jerk - Ever feel a jerk of the car when you accelerate fast? Well, engineers define a jerk as a unit of the rate of change of acceleration. 1 jerk is equal to 0.3048 m/sec³.

jiffy - there are two definitions of a jiffy, both of which are units of time and mean very, very fast. In computer engineering, a jiffy is one cycle or one tick of the computer's system clock. It is 0.01 second. The second definition is the time required for light to travel one centimeter, as proposed by American chemisty Gilbert Lewis. This translates to 33.3564 picoseconds.

klick - It's military-talk for kilometer. The term became popular in the 1960s among American soliders in Vietnam, though some believed it had been used as early as the 1950s by soldiers stationed in Germany. It probably came from the "k" and the "l" in "kilometer," but I suspect the soldiers thought it was cooler to say klick than kil-o-meh-tur. (Source)

Man-Month - it doesn't exist, the Man-Month is a myth: "Adding manpower to a late software project makes it later."

Mickey - Named after Mickey Mouse, a mickey is the length of the "smallest detectable movement" of the computer mouse. It's about 1/200 to 1/300 inch or about 0.1 mm.

Say it after me: Mickey Mouse moves the Mickey Mouse mouse a Mickey.

millihelen - If Helen of Troy had "the face that launched a thousand ship," then the amount of beauty needed to launch a single ship is a millihellen. A negative hellen is the amount of ugliness that makes a thousand ships sail the other way.

MegaFonzie - A measure of coolness. In Futurama, Professor Farnsworth defined MegaFonzi as having 1000 times the coolness of Fonzie of the TV show Happy Days.

moment - If you ask someone to wait a moment, you're asking them to wait for a very short period of time. But how short? Turns out a moment is a medieval unit of time equals to 1/40th of an hour or 1.5 minutes.

nybble - A byte is a unit of measurement of information that can be stored in a computer (for example: a 1 gigabyte hard disk). So what is smaller than a byte? A nybble, of course - it is defined as half a byte.

Platonic year - a year without sexual relationships. Actually, no - it's an astronomical unit of time (also called Great year or Equinoctial cycle) basically measuring the period of time required for planets to align. It's about 26,000 years, which is exactly how long a year being platonic feels like.

Potrzebie - In his first "scientific" article titled "Potrzebie System of Weights and Measures", published in Mad Magazine, Donald Knuth (yes, the computer science legend) defined a potrzebie as the thickness of Mad Magazine #26 or 2.263348517438173216473 mm. He also defined a unit of force as whatmeworry and so on.

proof - You've seen this in a bottle of liquor: 100-proof, 80-proof, etc. In the 18th century, before hydrometer was a common instrument, people used to "prove" that their alcoholic drink wasn't watered down by using a "gunpowder proof." The alcohol and gunpowder were mixed in equal proportion and then ignited. If the mixture burned, then it is proof that the alcohol wasn't diluted.

Today, proof liquor is defined as containing 50% of alcohol by volume. A 100-proof whiskey contains 50% alcohol.

Sagan - Carl Sagan loved to say "billions and billions of stars," so in his honor, a Sagan is defined as at least 4 billion. So that you know, there are nearly 100 Sagan (400,000,000,000) stars in the Milky Way galaxy.

Scoville - Named after its creator, chemist Wilbur Scoville, this unit measures the hotness of a chili pepper. A scoville is the dilution factor of a solution of chili pepper extract until the "heat" (the amount of the chemical capsaicin) is no longer detectable to tasters.

A bell pepper has a Scoville rating of 0, whereas a habanero has a rating of 200,000 (meaning a solution of habanero extract needs to be diluted 1:200,000 before the heat goes away). The hottest pepper in the world is the Naga Jolokia, with 1.05 million Scoville. A pepper spray is rated between 2 and 5.3 million Scoville.

smidgen - Yes, it means "small" but how small? A smidgen is exactly 1/2 a pinch or 1/32 of a teaspoon.

smoot - one smoot is defined as 5 feet and 7 inches (1.7 m), the height of Oliver R. Smoot, then an MIT undergrad who during his fraternity pledge was used by his fraternity brothers to measure the length of the Harvard Bridge between Boston and Cambridge, Massachusetts. They simply laid him down on the bridge and drew a mark where his head was, repeated the entire exercise along the bridge, and got a value of 364.4 smoots plus or minus one ear.

Oliver Smoot being used as a yardstick for the Harvard Bridge - source: Smoot 50th

The next time your on the Harvard Bridge, look out for the markings, which are actually used by the Cambridge police department to this day to identify the location of accidents on the bridge.

Twain - "Twain" is actually an archaic term for "two." If you're thinking of Mark Twain when you read this, you'd be right. Samuel Clemens, who used to work as a steamboat pilot on the Mississippi River, got his pen name because "mark twain" was what riverboatmen would yell out when they measured the depth of the river. It meant that the depth is two fathoms (about 12 feet), the minimum depth required by boats.

Warhol - Andy Warhol once said that "In the future everyone will be famous for fifteen minutes." So, warhol is a measure of fame. 1 kilowarhol is being famous for 15,000 minutes or approximately 10 days. Conversely, 1 milliwarhol is about nine-tenths of a second of fame, which is about how long it'll take my brain to forget a name. (Source)