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

At c , will we live forever?

  1. Dec 14, 2014 #1
    I made a simple time dilation slider to experiment with the figs, i noticed at 100% c speed the time = 0
    So does it mean that a person in a rocket at c speed, will live forever?

  2. jcsd
  3. Dec 14, 2014 #2


    Staff: Mentor

    Welcome to PF!

    Well relative to someone on the Earth yes. However we can never go at the speed of light only approach it. The energy requirement becomes so great that even if we had all the energy in the universe we still couldn't quite reach 100%.

    The person on the spacecraft will not feel as though they lived forever. They will feel they are ageing just like someone on the Earth.
  4. Dec 14, 2014 #3


    User Avatar
    Science Advisor
    Gold Member

    Since we can't go 100% c, the question is meaningless.
  5. Dec 15, 2014 #4
    i am here to learn
  6. Dec 15, 2014 #5
    Everyone is, btw are you Robert Downey Jr. ?
  7. Dec 15, 2014 #6
    No, and my proof is my iron deficiency!
  8. Dec 15, 2014 #7
    Theoretically , yes. Experimentally, no one knows.
  9. Dec 15, 2014 #8


    User Avatar
    Science Advisor
    Gold Member

    Can you please provide a legitimate online reference to support your theoretical statement?
  10. Dec 15, 2014 #9
    I agree with Imperial Thinker's statement , can you imagine ask Albert Enistien about a legimate reference to support his theoretical ideas in 1905, yet we all know now that he was right, anything is possible my friend
  11. Dec 15, 2014 #10
    I think that's the whole point of scientific enquiry, Adam, is that anything is NOT always possible. That's what we're trying to figure out here, what is and what is not possible. And as far as we know, traveling at light speed and living forever for a massive object such as a human is not possible. Not even theoretically, as ImperialThinker asserted. Maybe "science fictionally," but not theoretically in terms of a consensus of contemporary physicists/cosmologists
  12. Dec 15, 2014 #11
    Yes I can, and he would support his theoretical ideas.

    That shows that you don't understand how science works. No, anything is not possible, and if you admit that Einstein was right, you can't agree with Imperial Thinker's statement, because what he says is that Einstein was wrong.
  13. Dec 15, 2014 #12
    You can live arbitrarily long relative to earth provided sufficient energy to accelerate and turn back at that speed.

    In fact, it theoretically takes infinite coordinate time (distant observer's) to get to the event horizon of Schwarzchild blackhole. However, you either never return or leave within short amount of time depending on your impact parameter (due to lack of stable orbit within 1.5 Schwarzchild radii).
  14. Dec 15, 2014 #13
    Sorry, I need to clarify that the speed I am referring to means certain speed arbitrarily close to speed of light without actually reaching it.
  15. Dec 15, 2014 #14
    At light speed, you would not be alive.
  16. Dec 15, 2014 #15
    Why not? If he could travel with the speed of light physics would be different, maybe he would be alive, or he would turn into a rabbit :D All we have is our physics and our world, in which there is no possibility to travel at the speed of light.
  17. Dec 15, 2014 #16
    In our world, the only way that I could think of is to evaporate every massive particles of an object into photons, such as annihilation and then pair creation, which travel at c. In that sense, I do not know any photon based organisms and I would assume the photons created not alive.
  18. Dec 15, 2014 #17


    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

    SR says that no matter what force you apply, you can never accelerate a massive object (like a person) to speed c. A massive object can however have a speed very close to c. In fact, you already do have a speed close to c, in some inertial coordinate system. There's always a particle such that you have a speed greater than 0.9 c in every inertial coordinate system that's comoving with it. Does that make you live forever, or almost forever? (No, it doesn't).
  19. Dec 15, 2014 #18


    Staff: Mentor

    Thread reopened. Please bear in mind the PF rules regarding references.

    Sure, and his answer would be to simply give you the legitimate peer-reviewed references that he himself published in 1905.
  20. Dec 15, 2014 #19


    Staff: Mentor

    No, theoretically and experimentally the answer is no. See below for why.

    A better way to say it, to avoid questions about whether the term "alive" could be applied to something made purely of photons, is that, to anything moving at c, whether a photon or anything else, the concept of "time" (more specifically "proper time", the time elapsed on a clock carried with the object) is meaningless. And since the concept of "living forever" depends on having a meaningful concept of time, the concept of "living forever" is also meaningless for anything moving at c. This is true both theoretically (because in the math of relativity, photons, and other objects that move at c, move on null worldlines, which do not have a meaningful concept of proper time) and experimentally (because the energy-momentum relation for photons, which is what verifies that they have zero invariant mass and move on null worldlines, has been extensively confirmed in experiments). So the answer to the OP's question is "no".
  21. Dec 15, 2014 #20


    User Avatar
    Gold Member

    The question is not meaningless; it is an opportunity to explore.

    You could - in theory - reach a speed arbitrarily close to light*. If you were to do so, you could manage to essentially outlive the universe. That's pretty close to forever. Of course, you would still only experience the same century lifetime, more or less, but you would be able to witness the universe aging and dying outside your spaceship window.

    * as measured relative to some arbitrary local point
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook