When You Push A Long Pole, How Long Does It Take The Other End To Move?

There are a mountain of areas of physics that appear counterintuitive , with some of the most famous examples includingwave - particle dualityandtime dilation .

But you may feel like you have a somewhat nonrational understanding of somewhat simple macro objects , for illustration , a perch . So here ’s a interrogative ; when you take a long alloy pole and labour it at one end , how long does it take for the other death of the magnetic pole to move ?

Well , we have it off that the variety can not be instant , even if that would be really useful . If the other end moved instantly , then you could communicate faster than the speed of luminance like sci - fi aliens , albeit with a really long pole or system of long perch used to bring meaning . And you do n’t want to induce anytime travel paradoxesby dig things with a big reefer .

Another reasonable dead reckoning would be that it moves away at the speeding of sparkle , from a " it ’s clearly very fast " perspective . But that ’s not correct either . As explain by real scientist Brian Haidet on his YouTube channelAlphaPhoenix , the time it takes for the other close of the pole to move is delimitate by the upper of sound in the metal taproom .

When we pick up a strong object like alloy it feels , well , middling satisfying . It seems at our scale to be one long strict structure with no gap in between or compressibility . But at the low scale , the metal measure is a crystalline structure order from nucleon and their electron , hold in place by their shackle .

When you push on the metallic element bar , the first level of atoms push on the next , which pushes on the next , distribute through the bar like a moving ridge , at the speed of sound in that sensitive . That ’s not to say that it is n’t extremely debauched . Sound movement at different speed through those mediums , traveling faster through greater density . On Earth , levelheaded moves at 1,500 meters ( 4,921 feet ) per 2nd in water , and in air around 340 meters ( 1,115 metrical foot ) per second . In solid , sound moves much quicker , though how fastdepends on the substantial , and all these calculate on factors such as temperature and pressure .

In the television above , Haidet quiz the wait by hitting a rod at one remainder and detecting when the signal passed down through the pole to the other end . He notice that the delay touch what you would expect if it took position at thespeed of soundin steel , in a neat tabletop experiment .