Why does a straw look bent when it sits in a glass of water?
The Straw's Secret Swerve
Why does a straw look bent when it sits in a glass of water?
Drop a straw into a glass of water and something sneaky happens. The part underwater seems to slide sideways, like the straw cracked in half at the waterline. Pull it out — perfectly straight. Put it back — bent again. Your straw is fine. Your eyes are being pranked, and light is the prankster.
To get the joke, you have to know one thing about light. Light travels in straight lines, racing along until it hits your eye. Your brain trusts those lines completely. It assumes light always came at you straight, no detours, no turns. Usually that's a safe bet. Around water, it isn't.
