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Answer to light speed travel is E=mc2 itself?

  1. Jul 24, 2011 #1
    First off, I'm new here so if this is in the wrong section I apologize. Now to the question:
    As dumb as this may sound to people that know more about physics then me (I'm a med student but I find myself reading about physics time to time) it makes perfect sense in my head (due to lack of knowledge most likely), anyway, I was once told a simple way to understand E=mc2, "if something is going at 10mph, it doesn't simply take twice the energy to go twice as fast, it requires exponentially more energy. As such, the faster you go, the heavier the object gets. So in order to get to lightspeed, you would need infinite energy, to get past lightspeed you would need infinite energy+x". Now for the question, couldn't the fact that the weight of the object moving is increasing infinitely somehow be used to create infinite energy? ie something moving 100mph weighing 100lbs could generate 100 units of energy and that energy could be used to move it at 101mph weighing x lbs which would then generate x units of energy etc?
  2. jcsd
  3. Jul 24, 2011 #2


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    Staff: Mentor

    In your reference frame you are always stationary so you notice no change in your fuel, but even if you did the energy content isn't based on mass anyway, it is based on chemistry.
  4. Jul 24, 2011 #3


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    Staff Emeritus
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    An object travelling at high velocity does NOT have an increased mass. The aspect of Relativistic mass is very misleading. A simple way to understand it is that if you were travelling 99% the speed of light, you would not even know it without comparing your frame to another frame of reference. If MASS increased, you would know how fast you were going compared to an "absolute" frame to judge from. This does not happen.
  5. Jul 24, 2011 #4


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    If we have an object initially at rest (and use that as our reference frame) and then if the object is accelerated, it would begin to require more and more energy to accelerate it by the same amount as it got closer to the speed of light. Which is why we say the relativistic mass of the object will increase.
    frdk91 had the thought that maybe the energy of the moving object could be harnessed and used to further increase its velocity. But when you try to make use of the energy of the moving object, you must slow it down. So you'd simply be slowing the object down, and speeding it up again by the same amount.
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