Filled Space
Two stretches between three marks: one filled with ticks, one left empty.
How to play
Look first, then answer
Two stretches between three marks: one filled with ticks, one left empty.
- Under a minute · one question · then the explanation
How it works — best read after you have tried it
Full looks longer than empty
The two stretches are exactly the same length. A stretch divided into many small parts tends to look longer than an empty one, perhaps because there is simply more there to take in along the way.
Johann Joseph Oppel first mentioned it in 1860 and August Kundt studied it systematically in 1863. It is sometimes blamed for why a path with many landmarks feels longer than a bare one.