Couldn't you accelerate past light by means of gravitational acceleration?

  1. If I type in any equation for acceleration due to gravity, I can look and see that it will eventually become bigger than 186,000 miles per second. So, what's stopping the acceleration from being faster than light if the principal of the curvature of the fabric for space allows matter to follow a path that would do so? Your not adding kinetic energy to the system, your just converting the potential energy into kinetic energy via changes in gravitational potentials, the energy to travel faster than light is already there, and gravitational fields themselves don't lose energy through interaction, so there's your technical infinite energy supply.
    Also, what about black holes? We have no idea what goes on inside a black hole itself, for all we know they might not even be part of the universe and therefore are not subject to all the rules of the universe. Couldn't one of those super-massive black holes be so big that there's a big enough gravitational well to accelerate past light? I mean I read in long chapter book just called "Black Holes" that it would take days for in-falling matter to reach the singularity, surely that would be enough time for very high gravity to accelerate something that much...
  2. jcsd
  3. DaveC426913

    DaveC426913 16,537
    Gold Member

    You're using the wrong equation.

    You're using the equation for Newtonian acceleration; you need to use the relativistic equation for acceleration.

    Read up on Lorentzian Transform.
  4. So something about the fabric of space being stretched in a way relative to the observer so that the space between you and the observer would increase or decrease as you approached light or something like that? What about black holes where its already really stretched out?
  5. DaveC426913

    DaveC426913 16,537
    Gold Member

    Lorentzian Transform.

    Well, the universe is stopping it.
  6. How does traveling near the speed of light actually add more fabric of space into existence between you and an observer at rest? Or why would it stretch it out in such a way as to whatever its doing.

    By the way I think we keep responding to posts too soon...
  7. DaveC426913

    DaveC426913 16,537
    Gold Member

    It doesn't.

    What gets distorted is time.
  8. So as you accelerate near the speed of light, time (which I thought was part of the fabric of space?) or the rate at which you perceive photons coming from an object...and then something about dots following what looks like two inverse equations with slant asymtotes at y=x and -x.
    I'm assuming that those asymtotes represent the acceleration at speed of light in some way, but I don't get exactly what is happening in reality.
    So as you accelerate near the speed of light, what is happening to time exactly?
  9. DaveC426913

    DaveC426913 16,537
    Gold Member

    It might do you to read up a bit on the subject. There are about a thousand threads here alone.

    Can't really sum the whole thing up in one post.
  10. I kind of get what's going on.
    Does it have something to do with that as you get closer to the speed of light, the speed of time relative to you slows down? And maybe it can't slow down all the way because they you wouldn't be able to travel distance over time? Something like that?
  11. DaveC426913

    DaveC426913 16,537
    Gold Member

    Well, yes. No matter how much you accelerate, your velocity only asymptotically approaches c. It will never each it.

    At .999999999999999999c, you are time-dilated almost the the point of being frozen (from the point of view of the rest of the universe). Stars will grow old and die while you reach for the throttle.
  12. Ok, it makes more sense, thanks.
  13. Actually now that I thought about it more, there's a little piece missing. I understand that it "does" happen asymptotically, but there's some little middle piece missing about why time's speed slowing down relative to you makes it so that you can't ever accelerate to light speed that I can't quite figure out.
  14. PAllen

    PAllen 5,890
    Science Advisor
    Gold Member

    If you are going .99999999999999c passed one observer, it remains true for you that when you shine your flashlight in front of you, it is still going c. You have made no progress at all towards catching light as you see it. Further, note that for the observer you passed, light from your flashlight pointing forward goes at exactly the same speed as the observer's own flashlight (and both you and the 'stationary' observer see both beams going the same speed). There really is no distinguishable 'almost c' except from some chosen observer's point of view.
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