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Re-Poll: We are in a Schwarzschild black hole-T or F?

  1. Dec 31, 2007 #1
    Re-Poll: We are in a Schwarzschild black hole--T or F?

    Would I be correct to say that time can "run" either way? That is, in physics, time can be forward or backward. I realise that this language is loose bigtime.

    Here's my problem...

    Matter added to a black hole is added (geographically) near the event horizon.
    The "latest events in time" then are near the event horizon.
    So, to the black hole it's historical record is from singularity out to event horizon.
    To the black hole the future points radially outward.

    Er, this makes a conceptual difference? Maybe I'm thick?
  2. jcsd
  3. Dec 31, 2007 #2


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    you are trying to see the world from the point of view of the black hole.
    you say "to the black hole" it looks thus and so.

    that is an interesting thing to try and do. but it is not conventional.
    the usual thing in physics is to talk about OBSERVERS and look at things from the standpoint of some observer.
    time has meaning to an observer, the future consists of all events he could in principle influence, his forward light-cone, whatever could receive signals from his present self.

    that includes his future self

    the observer's past is his past lightcone, whatver could have sent him a signal that is getting to him and possibly influencing him now.

    To study a black hole it might be better to think of an observer who has fallen in and is en route to the singularity.

    you can pretend it is a very big black hole so it takes years of falling, and a very small observer so that tidal forces don't affect him much for most of the way----so he has a lot of time to observe and think.

    to the falling observer, his future lightcone consists entirely of directions which end up at the singularity.
    his future is all INWARDS and his past is all outwards.

    I realize this is different from what you were doing, looking at things from the perspective of a personified black hole. I'd rather not do that. A Schwarzschild black hole is just a solution of Einstein GR equation of a particular kind (static, unchanging with time). Like any spacetime geometry which is a solution, it holds the possibility of many different observers----many different pasts, futures, trajectories. It is just a geometry.

    A black hole is not an observer. It is a geometrical context in which you can define many different observers. So I would suggest not personifying it and trying to look at things from its standpoint (which might result in more confusion than it's worth.)

    it was a creative idea though.
  4. Dec 31, 2007 #3
    Thanks for your thoughts Marcus.

    I gained courage for a change of perspective from the scenarios

    1. Observer out in flat space watching item falling beyond horizon... the item's time and motion appear to stop
    2. Item's perspective... time continues normally

    Seemingly both are valid depending on a declaration of reference frame.

    Looking into the black hole time would seem to us to continue running forward to the singularity ( hence to "get out" time would have to be reversed). It would seem then that space ...3d space.. would be circumferential. A sort of balloon analogy reversed.

    Then, thinking a little further, this would be identical to our universe heading for the big crunch. (forward time less space). Seems rather too close a match to me hence the temptation to arbitarily declare a reversal of time.

    Anyway thanks for comments maybe I am not so thick.
  5. Jan 1, 2008 #4
    still is???
  6. Jan 2, 2008 #5
    Ok so here we have some light cone problems.
    Our observer has passed beyond the event horizon and has been within for say 1 hour. In the conventional scenario:
    He has a past light cone. He examines his past and finds nothing unusual. He again checks his past light cone at time 1.5 hours and finds that his PAST has altered to include a following meteorite. AS time moves on he finds his past is continually being added to. This has some interesting cause/effect consequences. For example the appearance of the meterorite in his past suddenly changes his present by suddenly [lol] slowing his progress by gravitation such that he never got to where he was!!!
    Clearly there are some aspects of Black Holes that are subject to examination by holistic perception and these aspects require proper mathematical examination rather than half thought through Newtonian assumptions.

    Interestingly the forward light cone of our infalling observer has interesting consequence also; given a conventional assumption of the future lying toward the singularity:
    The usual conical shape of a light cone cannot apply as the future space is contracting (getting smaller toward the singularity). It would appear more like the icecream end of an icream cornet ... rounded. Exactly like a minature Past light cone as it is followed back to the Big Bang i.e. the usual 45 degree angled sides of a cone are modified to a curve as the "cone" is traced back to the BB singularity

    If we examine a shorter future cone of a few hours i.e. is a cone of an object travelling close to the speed of light we will find that it is orientated just slightly inward of the event horizon circumference. No matter how much energy we can add we cannot orientate the light cone to exactly match the circumference direction. Now lets say we have only just entered the black hole a few seconds ago. Whatever the scenario future /past, we can agree that we are very close to the event horizon though inside of it. Now we know, don't we(?) that the event horizon is moving radially outwards at the speed of light [see later]. We know then that in addition to our spatial speed we have a very high radial speed as we are situated close to the event horizon. We also agree that the radial direction measures time even if we disagree as to future/past.

    Further, our radial speed is outward, away from the singularity. Even more stunning; if we slow down and eliminate the energy input and become spatially stationary within the Black Hole
    we find that our future light cone orientates radially outwards!! We become, in effect, exactly as per the balloon so-called analogy which is exactly the same as our 'normal space' given that the possibility worked by Ned Wright (a slight curvature to the universe is possible). So, it becomes fairly obvious that a black hole is an inflationary universe. Well that's my opinion and I have said why so.

    Re the event horizon travelling radially outward at the speed of light when approached closely... The logic: Let's say you approach the event horizon closely but are scared you might cross the line. Clearly you would arrange your thrusters to push you directly away from the black hole. You would in fact be travelling close to the speed of light and only make very slow progress away from the hole. The event horizon then must be approaching you at "c".
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