Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Hypothetical implication of Lorentz contraction

  1. Aug 14, 2012 #1
    Would it be possible for a truck, measuring 5ft tall when stationary, to pass under a 4ft barrier by accelerating towards the speed of light?

    If so what would a spectator see if standing next to the barrier, would the spectator see the truck shrink? What would you see of the barrier from the trucks frame of reference, would the barrier seem to grow?

    Sorry if my question appears unclear I couldn't think of another way to explain it. Thank you in advance for reading/attempting to answer the question.
  2. jcsd
  3. Aug 14, 2012 #2


    User Avatar
    Science Advisor

    There is no contraction in the transverse direction, so a five-foot tall truck will remain five feet tall in all reference frames.

    There is a longitudinal contraction, and the longitudinal version of this asks why the contracted truck does not fall into a pothole. This is called the Thin Man and the Grid Paradox. See here.
  4. Aug 14, 2012 #3

    Doc Al

    User Avatar

    Staff: Mentor

    Length contracts only in the direction parallel to the motion, not perpendicular to it. The height of the truck would remain unchanged in the road frame.
  5. Aug 14, 2012 #4
    Thank you, that helped a lot. Do I now need to close the thread?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook