Measurement

Season 05

Episode 17

Duration 23:06

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How wide is a chasm? How hot is boiling water? How old are you? Every answer starts with a measurement. In this episode of Bill Nye the Science Guy, Bill shows how humans understand the world by projecting a grid on it, using shared standards of length, mass, time and temperature.

In this episode you will discover:

Why nothing we build fits together without careful measurement
How the metric system is based on our ten fingers
Where the metre originally came from, the distance from the pole to the equator
Why the Celsius scale was designed around freezing and boiling water
How aircraft rely on hundreds of measurements to fly safely
What a standard is and why every country needs the same one

Shared units for a shared world

Bill takes measurement seriously. He proves it by measuring a chasm at 194 centimetres, cutting a bridge to exactly 194 centimetres, and crossing safely. Measuring turns the world into something we can compare, describe and build with, from a picture frame to a passenger jet, so long as everyone agrees on the same units.

Key concept
Standard unit
An agreed size that everyone measures against, so a metre in Paris is the same as a metre in Tokyo.

Key concept
Metric system
A worldwide scheme built on tens, where a metre splits into 100 centimetres, 1000 millimetres and a million micrometres.

Key concept
Celsius scale
Zero degrees where water freezes, 100 degrees where it boils, 100 equal steps in between for easy comparison.

Bill Nye’s demonstrations

Bill lowers a bridge onto a chasm to prove that a good measurement fits the first time. He then explains that the metre came from dividing the distance from the North Pole to the equator into ten million parts, and pulls out a thermometer filled with liquid metal that expands the same amount for the same warmth, so an astronomer named Anders Celsius could pin zero to freezing water and 100 to boiling water.

Try this at home

The hodometer roller. Draw a straight line 15.8 centimetres long on stiff card, use a drawing pin as a compass point and swing a pencil to draw a circle. Cut out two of these circles, tape them together on a stick and add matching arrows. When you roll the wheel and the arrows meet, you have travelled exactly one metre, because the outside of that circle is one metre around. Now you can measure a garden, a corridor or a whole football pitch.

Cool facts

There are 100 centimetres in a metre, just as there are 100 cents in a dollar.
Modern factory robots can find their way to any point within half the thickness of a sheet of paper.
Before standards, people measured with body parts, and a foot was literally whichever royal foot the king had.
The four measurements humans use most are length, mass, time and temperature.

Science update: since this episode aired

The International Bureau of Weights and Measures near Paris is preparing to redefine the second itself, replacing the caesium atomic clock with even more precise optical clocks, and its Consultative Committee reported in October 2025 that international comparison campaigns are on track for a decision around 2030. Bureau International des Poids et Mesures, Sèvres, 2025
Two extra Galileo satellites entered full service on 29 January 2025, completing Europe’s own satellite navigation constellation and letting phones and receivers pin down a position to metre level accuracy anywhere on Earth. European Space Agency, Paris, 2025
An international team including the UK’s National Physical Laboratory linked ten of the world’s best optical clocks across six countries in 2025, comparing them by fibre and satellite in the most extensive coordinated test to date, an essential step toward the new definition of the second. Optica Publishing Group, Washington and Teddington, 2025

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Curriculum focus

Built on NGSS MS-PS1-2 (measure and describe properties), MS-PS3-4 (thermal energy transfer) and MS-ETS1-3 (comparing solutions using data). Complementing that, it is pitched at KS3 physics (working scientifically and units) and works as an introduction or revision aid for GCSE and IGCSE physics and combined science on SI units, precision, accuracy and measurement, across boards such as AQA, Edexcel, OCR and Cambridge IGCSE. The worksheet and critical thinking questions take these ideas further than the episode alone.

NGSS MS-PS1
KS3 physics
GCSE revision
IGCSE revision
Metric system
Standards