Floating in the air or levitating, sand move through hour glass. Close up of hourglass clock. Old time classic sandglass timer. Clos… | Levitation, Hourglass, Timer
robin. on Twitter: "I've just been reading about this Physics puzzle from the '60s. Quite baffling at first, if you haven't seen it before! Why, when the tube is inverted, is there
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Massimo on Twitter: "A famous physics puzzle: why does the hourglass not start rising right away? [source: https://t.co/iquNSPoJDn] If you want to know the answer, you may visit this site, that has