Clickory

Classroom mode

Run it in class

How long is a coastline — and would two people ever measure the same number?

Show of hands — before you project anything

Predict first: you measure a wiggly coast, then measure again with a much shorter ruler. Do you think the total gets shorter, stays the same, or grows? Why?

  • A Way more than you'd guess
  • B About what you'd guess
  • C Way less than you'd guess

Count the votes out loud. Hold them to it — then watch.

Project it (fullscreen)

Discussion prompts

  • Predict first: you measure a wiggly coast, then measure again with a much shorter ruler. Do you think the total gets shorter, stays the same, or grows? Why?
  • Predict first: does a perfectly round lake's length keep growing the same way a coast does as you measure finer? What's different about the two shapes?
  • If there's no single true length, how should a textbook or atlas decide what number to print for a country's coastline?

Where it shows up in real life

  • Atlases listing very different coastline lengths for the same country because they used different map scales
  • Tracing a wiggly border or river on a map and arguing about how 'long' it really is
  • Zooming into a coastline on a phone map app and watching new little bays appear that weren't visible before

A prediction-first worksheet — no answer key.

zero prep · no login · any projector

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