1. PF Contest - Win "Conquering the Physics GRE" book! Click Here to Enter
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Traveling at the Speed of Light

  1. May 4, 2009 #1
    In A brief History of Time, Hawking says that it is impossible for us to go the speed of light because if we were able to go that speed our mass would be infinite...or something like that. Is it really just as simple as that? Or was there something I misunderstood? Sorry if it is a dumb question...I am a first time poster. Thanks!
  2. jcsd
  3. May 4, 2009 #2


    User Avatar

    Staff: Mentor

    I wouldn't call it simple, but it is like that.
  4. May 4, 2009 #3
    So put simply, as you move faster, your mass becomes bigger? Why is that?
  5. May 4, 2009 #4


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    No, as the traveler you observe no change in mass.
  6. May 5, 2009 #5
    because it would take an infinite number of energy to make that happen.
  7. May 5, 2009 #6


    User Avatar
    Science Advisor

    A simple explanation of why "mass" increases as your speed approaches the speed of light is this:

    To make thing simple, let's just accept that nothing can move faster than the speed of light. So imagine you are putting a constant amount of energy into an object to make it go faster. Of course, eventually you get close to the speed of light, but you cannot keep speeding up indefinitely or else your speed would exceed that of light! But, you are still putting in energy at the same rate. So, where does the energy you are putting in go? Effectively, it goes into the inertia, or mass, of the object, making it progressively harder and harder to increase it's velocity with the same amount of energy.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook