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Meet the Measurement League

You can download printable versions of the superhero cards on our Resources page.


monsieur kilogram

With his immensely strong arms, Monsieur Kilogram is the master of mass.

The kilogram is a cylinder of special metal about 39 millimeters wide by 39 millimeters tall that serves as the world’s mass standard.


By reading the vibrations of her laser-cooled cesium atoms, Professor Second can synchronize any frequency and correct any clock.

A second is the time it takes an excited cesium atom to vibrate 9,192,631,770 times.

meter man

With his sharp eyes and stretchy ruler arms, no distance is too big or small for Meter Man to measure.

A meter is the distance light travels in a tiny fraction of a second.


Ms. Ampere has a shocking amount of power over the flow of electrons—electrical current.

In practical terms, an ampere is the measure of the flow of electrons past a point—about 6 quintillion electrons (that’s a 6 followed by 18 zeros!) per second.

Dr. Kelvin

With the ability to speed up or slow down particles, Dr. Kelvin can measure any temperature.

The kelvin temperature scale begins at absolute zero, the coldest possible temperature and the point at which even atoms would stand perfectly still.


Don’t let her small size fool you, Candela’s power over light helps to brighten the whole world.

A candela is a measure of brightness about equal to the light given off by a single candle.


Able to sniff out and count the atoms of every element, the Mole is the king of chemistry.

Equal to about 600 sextillion (that’s a 6 followed by 23 zeros!), a mole is a shorthand way to talk about huge numbers, especially of tiny things.

The Villain

Measurement League: Major Uncertainty
Credit: NIST

An alien invader from parts unknown, Major Uncertainty uses his less-than-trustworthy monkey wrench to generate a dreadful "chaos beam," which causes us to doubt the accuracy and precision of our measurements.

Major Uncertainty feeds on this doubt, which makes him bigger, stronger, and less pleasant to be around.


Created August 9, 2016, Updated November 15, 2019