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by iwnit on September 29th, 2007

iwnit

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If stars are light sources and black holes are light absorbers, could not one be the opposite of the other? Or black holes just be stars going back in time?

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  • by Greg Griffin on September 30th, 2007

    Greg Griffin

    Not really. You need to look at what the objects are.

    The direction of time is determined by something called entropy. Entropy must always increase therefore forward in time is always in the direction of increasing entropy.

    Now stars and Black Holes both have entropy. So their time direction must be the same. So one cannot be the other reversed in time as their time direction is the same. Black holes eventually die just as stars do.

    Also to view black holes as "Light Absorbers" and stars as "Light Sources" is somewhat simplistic. A black hole IS a star just a very very compact one. At these densities the object's gravity is so severe that nothing can escape. A light emitting star could be viewed as a black hole without sufficient mass to pull the light back in.

    SO I don't see how they could be viewed as opposites - they are the same thing just with different values of parameters. Is like saying a tall man is the opposite of a short man. not really they have the same features just at differing values.

    The opposite of a black hole would be a white hole though these are purely theoretical and somewhat sci-fi. This would be a singularity which emitted mass/energy.

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    • Greg Griffin: thank you very much for answering this somewhat crazy question with a very plausible explanation.

      iwnit

      by iwnit on September 30th, 2007

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