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

Black hole - entrance theory

  1. Sep 1, 2005 #1
    I read the following theory:

    As you enter a black hole, your time will slow, and the entire life of the universe will flash before your "eyes" as you fall in.

    If you see the life of the universe flash before your eyes, wouldn't the black hole evaporate by then?

    Wouldn't other matter hit you by then?
    Would you ever hit the singularity?

    Question about the singularity itself - If you hit it, and time and space splits there(Another read theory), how will the material in the singularity move? Can there be motion without time?
  2. jcsd
  3. Sep 2, 2005 #2


    User Avatar
    Gold Member

    I wouldn't worry too much about it; the tidal forces would rip you to atoms long before you'd notice any time-dilation effects. And you'd already be dead from the radiation before that happened.
  4. Sep 2, 2005 #3
    In Schwartzchild coordinates you will take an infinite amount of time to reach the event horizon. (Although you won't see the whole life of the universe before you cross it - I'm not sure what you might see after you have crossed it). However, this is not the only possible coordinate system, and with respect to your proper time you will cross the event horizon in finite time. So the standard answer is that no, the black hole won't evaporate before you have fallen in. See http://cosmology.berkeley.edu/Education/BHfaq.html#q9

    I have to say that actually I feel that the standard answer is flawed, and your idea that a black hole would evaporate before you fall is tenable. See http://www.chronon.org/articles/blackholes.html
  5. Sep 2, 2005 #4
    That just seemed some type of fairy-tale ending. In true sense, as you approach the black hole and when you are at a good healthy distance from the BH , the variation in forces due to the massive BH from your head to foot will be huge which will probably tear you apart much mor before you approach the event-horizon.Regarding the tme-slowing down , it doesnt. For an observer far-away , you would seem like stationary near the EH because you are accelerating at tremendous speeds , the observer on earth can probably never see you entering the BH because you seem stationary and as per the pbserver your time has slowed down to the limits that it has come to a hault.But for you time remains normal , you would enter the EH without the observer on earth knowing about it.

  6. Sep 2, 2005 #5
    This has always seemed flawed to me. If any matter that enters a BH would appear stationary at the horizon then surely, with the amount of matter that has previously fallen in, the BH would seize to be 'black' as it would appear to have a 'coating'/'shell' surrounding it.
  7. Sep 2, 2005 #6
    What you are interpreting from my statement is wrong.There's a considerable time-dilation effect in this case. Athough matter will easily fall into the BH , it doesnt for an observer far away . This doesnt apply directly that for an observer far away all matter whatsoever will never 'appear' to fall into the BH . Remember that for an observer far away , the matter approaching the BH will take much more time that the matter actually takes to get sucked in.It doesnt directly apply that 'matter doesnt enter the BH for an observer which is the case only when the matter is travelling at speeds approaching c"

  8. Sep 2, 2005 #7
    This isn't just from your statement. I've heard similar claims and I've wondered about it for years.
    I suspected it was because the explaination of matter falling into a BH was oversimplified to a high degree. I wasn't suggesting that matter doesn't enter the BH just that if the matter appeared to become stationary to an observer then all matter that's previously entered the BH would be visible. Since that is not the case the matter cannot appear to become stationary.
  9. Sep 2, 2005 #8
    In a previous thread https://www.physicsforums.com/showthread.php?t=87118
    you gave some various graphic representations of Dimensional logic.

    Firstly there are no "events" in a 0-D singularity? as the name implies, all things merge and therefore 'nothing seperates' a "dot" from a "line", nothing exists on a plane, a three-dimensional particle is the same as a two-dimensional particle, in that they are non-existent.

    Ok, now for particles that are emerging from "within" a zero-point dimension, to an area of Dimensional hierarchy, a *-* 1-D line gives energy freedom to expand, albeit in a linear mode. Away from the singularity particles merge and combine to a 2-D field, out of this field can emerge particles that are spacially connected, the Proton for instance is a 3-D particle, able to move and connect with other 3-D energies, and 2-D fields.

    Only now can events be directionally formed, in that a 'fixed' 3-D particles adhere to the laws of motion, and the Past Events precede the Present, and the Future follows thus. The fact spacetime is geometrically fused, is the reason that when you look over your shoulder as you walk along the pavement, you do not see yourself 1 second ago...2 seconds ago.. stretching out into a backwards diminishing horizon,you do not see "your" past events occuring from your realtime preference frame!

    Motion (particle) without time, can occur beyond a Quantum compact horizon (Planckscale) hidden variable,..and in the Macro Domain can occur at external to an observational horizon (same thing-hidden varable).
  10. Sep 2, 2005 #9
    Okay, so singularities, being 0-dimensional, have no "events", but motion IS possible between Planck time?

    The theory that I read (black hole stops time) was wrong? Figures... Meh.

    I understand the wormhole part, though. ^_^

    I'm going to look at info related to this, and maybe I'll figure it out.
    Thanks! ^_^
  11. Sep 2, 2005 #10


    User Avatar
    Staff Emeritus
    Science Advisor

    You won't see the entire universe after you cross the event horizon either, at least for a non-rotating black hole. The situation with a rotating black hole is much less clear. Take a look at


    I've attached the appropriate gif image from this long paper, which shows the trajectory plot of both an infalling observer and light rays in Finklestein coordinates.

    You can see that only a finite number of light rays cross the worldline of the infalling observer before he reaches the singularity.

    Note that there is a very similar thread in the relativity forum where I've also answered this question, BTW. The sci.physics.faq is actually a bit more detailed on this topic than Tedd Bunn's black hole FAQ.

    Attached Files:

    Last edited by a moderator: Apr 21, 2017
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook