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Thread: Black hole and Time

  1. #1 Black hole and Time 
    Forum Freshman Alex009988's Avatar
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    I saw on Discovery Science the programme of the universe. There have been told a lot of interesting things, for instanse,For big bang happened due to "nothing".Stephen Howking explained this phenomenon by the fact the the law of conservation of energy is saved.And what is the sum of positive and negative energy is 0. The negative energy went into space.I don't understand the phenomenon that is explained there.The essence of it is that if the clock fall into a black hole, time will slow down.And when the clock will reach black hole, time stops.In other words, in black hole no time!I have a quetions.1) What frame of reference time stops K or K'?2) In this case, Does Lorentz transformation relate to this phenomena?t'=t/sqrt(1-(v/c)^2) and t=(t'+(v/(c^2))x')/sqrt(1-(v/c)^2)


    Last edited by Alex009988; January 24th, 2013 at 06:06 PM.
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    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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    Is this thread beyond the event horizon?
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    Moderator Moderator Markus Hanke's Avatar
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    The essence of it is that if the clock fall into a black hole, time will slow down.
    Can you specify which time measurement you are referring to - is it proper time ( what the clock itself measures ), or is it coordinate time ( what a distant stationary observer sees ) ? These two readings will not agree in this case.

    And when the clock will reach black hole,
    Do you mean the singularity or the event horizon ?

    1) What frame of reference time stops K or K'?2) In this case, Does Lorentz transformation relate to this phenomena?t'=t/sqrt(1-(v/c)^2) and t=(t'+(v/(c^2))x')/sqrt(1-(v/c)^2)
    No, this has nothing to do with Lorentz transformations, because the in-falling clock is not an inertial frame of reference. The phenomenon alluded to is gravitational time dilation which is an effect from general relativity, and is related to the curvature of space-time in the vicinity of a massive object like the black hole.
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    Brassica oleracea Strange's Avatar
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    There are two completely different things here. First, there is Hawking's (and other's) speculation that the total energy of the universe is zero.

    Stephen Howking explained this phenomenon by the fact the the law of conservation of energy is saved.And what is the sum of positive and negative energy is 0. The negative energy went into space.I don't understand the phenomenon that is explained there.
    The idea is, I think, that gravitational potential energy is negative and that balances the (positive) energy and mass in the universe. One problem with this (to my uninformed mind) is that gravitational potential energy is only negative by convention...

    Note that we don't actually know how, or even if, the universe was created.

    The other, completely separate thing is the gravitational time dilation as you approach a black hole. I don't think I have anything to add to Markus's description...
    ei incumbit probatio qui dicit, non qui negat
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    [QUOTE=Markus Hanke;386123]
    [COLOR=#333333]Can you specify which time measurement you are referring to - is it proper time ( what the clock itself measures ), or is it coordinate time ( what a distant stationary observer sees ) ? These two readings will not agree in this case.
    I think it should be proper time. Announcer said so.[QUOTE=Markus Hanke;386123]
    [COLOR=#333333]Do you mean the singularity or the event horizon ?
    Singularuty.
    Let's think what is the time. I deem time is measures of process. And it's true, look around of you. Everything is in process.One theory told to us that universe arose as a result of collision of two branes. But collision is also process, hence before big bang must be time, mustn't it?. In other hand, theory forbidden think so.

    And more, wherever we look of our earth, we see the distance is not more than 13 billions light-years. Hence. Is earth center of universe?

    By the way, I've been studying as a physicist at the university.
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    Brassica oleracea Strange's Avatar
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    Quote Originally Posted by Alex009988 View Post
    But collision is also process, hence before big bang must be time, mustn't it?. In other hand, theory forbidden think so.
    We don't currently know what happened before the big bang (or if there was a before).

    And more, wherever we look of our earth, we see the distance is not more than 13 billions light-years. Hence. Is earth center of universe?
    The same would be true everywhere. Wherever you are in the universe you will see everything moving away from you (because everything is moving away from everything else) and here will be a sphere of "observable universe" around you.
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    ei incumbit probatio qui dicit, non qui negat
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    time supposedly stops at the event horizon
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    Moderator Moderator Markus Hanke's Avatar
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    I think it should be proper time.
    In that case yes, the proper time of an observer very close to the black hole will be dilated as compared to the proper time of a far away observer. This is gravitational time dilation, due to the curvature of space-time.

    Singularuty.
    Well, that is largely academic, because when a clock falls into the singularity it ceases to exist in the normal sense of the word. If we pretend the singularity is a "normal" point in space-time, then yes, the clock will be infinitely dilated as seen from "outside", and thus stop to advance. That does not mean however that time no longer exists.

    But collision is also process, hence before big bang must be time, mustn't it?
    The term "before Big Bang" is meaningless; this would be much like saying "north of the North Pole".

    Is earth center of universe?
    No, the universe doesn't have a centre point.
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    Moderator Moderator Markus Hanke's Avatar
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    Quote Originally Posted by granpa View Post
    time supposedly stops at the event horizon
    It is coordinate time which appears to stop, but an in-falling observer ( proper time ) will not notice anything special when crossing the event horizon.
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    Quote Originally Posted by Markus Hanke View Post
    but an in-falling observer ( proper time ) will not notice anything special when crossing the event horizon.
    They'll notice something special, just not time related.
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    Forum Freshman Alex009988's Avatar
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    Let's think about space.
    Supposing our universe was point and it has four-demensional space . Moreover universe has been increasing everywhere or it has been inflating as a balloon.Consequently if we will throw something and it will have rectilinear move. Hence, it will have returned on starting position.As we would be walking around the earth.If it so, it will be prove that universe is increasing and it has four-demensianal space.
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    why is the sum of positive and negative energy zero?
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    1 + -1 = 0
    Disclaimer: I do not declare myself to be an expert on ANY subject. If I state something as fact that is obviously wrong, please don't hesitate to correct me. I welcome such corrections in an attempt to be as truthful and accurate as possible.

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    obviously and electron/ positron stuff create one and you create the other right? but what if more of one particle exsisted at the start of the universe?
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