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Educational paper and video, Bertozzi, "The Ultimate Speed"

  1. Sep 12, 2014 #1


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    I thought others might be interested in an old educational paper and fim demonstrating that you can't accelerate material objects past c.

    Bertozzi, Speed and kinetic energy of relativistic electrons, Am. J. Phys. 32 (1964) 551

    The Ultimate Speed - An Exploration with High Energy Electrons -

    Abstract: Using a Van de Graaff electrostatic generator and a linear accelerator, the speeds of electrons with kinetic energies in the range 0.5-15 MeV are determined by measuring the time required for the electrons to traverse a given distance. The measurements show the existence of a limiting speed in accord with the results of special relativity. The kinetic energy, determined by calorimetry, verifies that an electric field exerts a force on a moving electron in its direction of motion that is independent of its speed.

    The film is honestly pretty dull -- it doesn't have the sense of humor that I associate with the old PSSC films from that period. It is nice, however, as a way of showing people very concretely what happens when you try to accelerate a material object past c. It makes it clear that this isn't just a matter of speculation. You can see all the hardware, cables, etc.

    The paper is easy to find online, although possibly illegally if your country's copyright laws are as repressive as mine.
    Last edited by a moderator: Sep 25, 2014
  2. jcsd
  3. Sep 12, 2014 #2


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    Ben, that's very cool indeed. I had never seen anything like that. A bit dry, as you say, but an excellent demonstration. Thanks for posting.
  4. Sep 12, 2014 #3


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    Nice use of a mechanical analog computer.
  5. Sep 13, 2014 #4


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    Brought back memories of old oscilloscopes with hoods, slide rules and hand drawn graphs. Thanks.
  6. Sep 13, 2014 #5
    Very nice; every time I thought, "But wait, what about..." (e.g., the timing paths to the scope) he was on it in the next moment (equal length cables - that he verified!).

    And white socks, no lab coat... :)
  7. Oct 2, 2014 #6
    I have a stash of some 30 slide rules. Kids miss out on a lot of insight by not learning slide rule. :)
  8. Oct 3, 2014 #7
    That's nice, I did not know that there's a movie related to the paper - and now on Youtube. :)
  9. Oct 7, 2014 #8
    I now watched the movie and I find it more instructive than the paper because the relevance of the energy measurement is better explained and even elaborated. This is very good teaching material.
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