The latest visual trick making the rounds is an image of intersecting grey lines against a white background, with 12 black dots on the nodes where the grey lines meet. All 12 dots are really on ...

The new illusion looks simple, showing intersecting grey lines on a white background. But looking closely starts it moving – and though there are actually 12 black dots in it, it’s only ...

So white spots on a black background look bigger than same-sized black spots on white background, and Galileo's glowing stellar objects are not really as big as they might appear to the unaided eye.