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B Is it possible Earth is a black hole?

  1. May 11, 2017 #1
    Yes I know. Sounds silly. I'm not a physicist, but it occurred to me to wonder: is it possible Earth is a black hole with data encoded in two dimensions on its surface? What would the proofs look like?

  2. jcsd
  3. May 11, 2017 #2
    No. Earth reflects light. Black holes don't, since light can't escape from them. EDIT: See e.g. Measuring Earth's Albedo.
  4. May 11, 2017 #3
    And this appearance of reflection couldn't be part of the encoding? I promise I'm not being flippant. Susskind explains that to the person entrapped beyond the threshold of the black hole, all seems fine. Outside the event horizon, all seems lost, but within it, there is no change. At least not initially. Is it possible that from here, we see things as they would normally seem as the information is encoded on the surface? I know. Funny questions.
  5. May 11, 2017 #4
    I know what you are talking about, black hole thermodynamics and the holographic principle. The holographic principle is theoretical physics. But I address your question from a more practical viewpoint:

    Let's assume you are on the Moon and you have got a powerful flashlight. Also assume there's a nearby black hole. If you shine that flashlight on the black hole, it will not reflect any light, the light will enter the black hole and not escape. But if you shine the flashlight on Earth, part of the light will be reflected. Thus, the Earth is not a black hole.

    Furthermore: The Earth can not be a black hole, it is too big and not heavy enough to be one. See The Schwarzschild Radius (HyperPhysics). EDIT: I haven't made the calculation myself but according to the http://en.wikipedia.org/wiki/Schwarzschild_radius#Parameters Earth's Schwarzschild Radius is about 9mm, that is, if the Earth had a radius of 9 mm it would be a black hole.
  6. May 11, 2017 #5


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    Thread closed temporarily for Moderation...
  7. May 11, 2017 #6


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    DennisN has covered pretty much all the ground here: there is no way that the earth can be a black hole. We know from the equations of general relativity what properties a black hole has, and the earth doesn't have these properties.

    The thread will remain closed, as there's no better answer than has already been provided.
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