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My physics teacher says,

“ When a train moves, there is a matter wave attached to it. Waves move from positive to negative. Outside of train is positive and inside is negative. So, the train may pull us towards it if we stand very close to it."

Is he correct?

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  • $\begingroup$ But why it is positive outside and negative inside? $\endgroup$ – Gurbir Singh Mar 19 '18 at 10:11
  • $\begingroup$ Welcome to Physics! Note that questions of the form "Is this right?" tend to be poor fits for this site because the answer, yes or no, is too short to be a valid answer. Please consider editing the question to be more open-ended and allow for longer answers. $\endgroup$ – Kyle Kanos Mar 19 '18 at 10:15
  • $\begingroup$ He is at least using a strange vocabulary. He may refer to a kind of suction if for some reason / irregularities / light between wagons the air displaced by the train suddenly regain its position. I personally won't stand by a passing train anyway :) $\endgroup$ – Alchimista Mar 19 '18 at 10:18
  • $\begingroup$ I have stood on a train platform when an express went through the station at about eighty miles per hour. I stood just behind the yellow line painted on the platform, but even there, the force of the wind was startling. I could easily believe that closer to the tracks, it could knock an unprepared person off his/her feet. $\endgroup$ – Solomon Slow Mar 19 '18 at 14:00
  • $\begingroup$ P.S., Matter waves have absolutely no significance in the description of any object that is large enough for you to see with your naked eye or even, with an ordinary light microscope. $\endgroup$ – Solomon Slow Mar 19 '18 at 14:10
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I am afraid I don't understand exactly what your teacher means, but I think that the main dangers of standing close to a moving train (particularly a fast moving train) is

  • air - movement of air and/or turbulence in the air caused by the train passing may push/pull you towards the train

The Bernoulli effect is relevant here. If the air between you and the train is moving quickly in the same direction as the train and the air on the other side of you is stationary (or at least not moving so fast) then the pressure of the air near the train will be lower than the pressure on the other side of you and there will be a net force pushing you towards the train. I suspect the closer you get to the train the greater this force would become, which would make it feel as if you were being sucked into the path of the train.

There are also some trivial practical considerations about standing close to moving train.

  • something sticking out from the train may hit you
  • if you move the wrong way you could hit the train
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