Why do you see stars if you bump your head? © Getty Images

Why do you see stars if you bump your head?

Ever wonder why you sometimes get starry eyed after a particularly bad bump on the head? It's all down to phosphenes.

Asked by: Anonymous

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Familiar from cartoon strips, this bizarre phenomenon is caused by the generation of so-called phosphenes – illusory flashes of light caused by pressure on the light-receiving cells in our eyes. The simplest – and least painful – way of generating them is by gently pressing on your closed eyelids then opening your eyes. Isaac Newton came up with another method while investigating the nature of light: sliding a bodkin (a think, blunt needle) between his eye and the socket-bone. Not recommended.


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