Push One End Of A Long Pole, When Does The Other End Move?

Many areas of natural philosophy seem counterintuitive , with well - known examples likewave - particle dualityandtime dilation .

But you may feel like you have a pretty intuitive sympathy of middling unsubdivided macro objects , for instance , a pole . So here ’s a interrogative sentence ; when you take a long metal pole and push it at one end , how long does it take for the other end of the magnetic pole to move ?

Well , we know that the modification can not be inst , even if that would be really useful . If the other end moved instantly , then you could communicate faster than the amphetamine of igniter like sci - fi extraterrestrial , albeit with a really long pole or system of tenacious pole used to convey signification . And you do n’t want to make anytime travel paradoxesby poking thing with a with child joystick .

Another reasonable guessing would be that it moves away at the speed of light , from a " it ’s clearly very fast " perspective . But that ’s not right either . As explain by material scientist Brian Haidet on his YouTube channelAlphaPhoenix , the clock time it takes for the other remainder of the pole to move is defined by the speed of sound in the metal bar .

When we pick up a solid object like metal it feel , well , pretty unanimous . It seems at our scale of measurement to be one long set structure with no spread in between or compressibility . But at the small graduated table , the metal measure is a crystalline structure arranged from nucleon and their electron , held in home by their bonds .

When you push on the metal taproom , the first layer of speck pushes on the next , which pushes on the next , spreading through the bar like a wave , at the fastness of sound in that culture medium . That ’s not to say that it is n’t exceedingly fast . Sound move at different speeding through those medium , travel quicker through greater density . On Earth , effectual moves at 1,500 meters ( 4,921 feet ) per 2d in water , and in air around 340 meters ( 1,115 feet ) per secondly . In solids , sound moves much quicker , though how fastdepends on the square , and all these depend on factor such as temperature and pressure level .