The Railway Lines
Two orange bars laid across a railway track that runs off into the distance.
How to play
Look first, then answer
Two orange bars laid across a railway track that runs off into the distance.
- Under a minute · one question · then the explanation
How it works — best read after you have tried it
Further away must mean bigger
The two bars are exactly the same length. The converging rails say that the top of the picture is far away, and something far away that makes the same size of image in your eye as something near must really be bigger — so your brain quietly scales the upper bar up.
That correction is what keeps a person walking away from you from seeming to shrink; here it is applied to a flat picture where nothing is further away at all. Mario Ponzo described the effect in 1911.