Long is not a number

About this video

What does it mean to measure something? Ask a friend to buy you a long rope, and they might bring one that is long enough for skipping but far too short for a swing. "Long" means different things to different people. It is a guess, not a measurement.

Now ask for a rope as long as 10 of your steps. Your friend can walk out the length and get it right. That is what measuring is: comparing something with a known amount you both agree on, and counting how many times it fits. This short animation shows why a number of steps works where a word like "long" fails, and why a measurement means the same thing to everyone who reads it.

Transcript

1. 0:00Buy me a long rope. But how long is long?
2. 0:04Your friend brings a rope that's long for skipping.
3. 0:08But for a swing, it's much too short.
4. 0:12Now say instead: as long as 10 of my steps. Your friend can walk it out, step by step.
5. 0:21That is measuring: comparing with something you both know.
6. 0:25Ten steps is a measurement. Everyone reads it the same.
7. 0:29Long is a guess. Ten steps is a measurement.