The Line Length Illusion
What to see and do: Does it look like the red line is longer than the pink line? Actually, the pink line is slightly longer than the red line! If you don't believe it, click on the lower pink line to drag and compare it with the red line.
What's happening: The bars make the red line look longer because the bars go outward as they go down the screen leaving lots of space on each end of the pink bar, making it look short.
Credit: This illusion is very old and we are not sure who first discovered it.