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Gravity seems holographic. What does that mean for reality?

300 points · 234 comments · ibobev

  1. qnleigh · · focus · HN ↗
    Susskind's original paper is shockingly readable, at least the first section. It doesn't use a lot of fancy math or derivations to justify holography. Mostly it uses basic concepts from undergraduate physics to show how the idea of holography is consistent and makes sense, despite it seeming incredibly counterintuitive at first glance.

    For instance, figure 3 shows how you can't hide a black hole behind another black hole, which has implications for how a 3D universe can be completely encoded in a 2D region.

    <a href="https:&#x2F;&#x2F;arxiv.org&#x2F;html&#x2F;hep-th&#x2F;9409089v2" rel="nofollow">https:&#x2F;&#x2F;arxiv.org&#x2F;html&#x2F;hep-th&#x2F;9409089v2

    1. Obscurity4340 · · focus · HN ↗
      What shape is space? Like, how far does space extend &quot;above&quot; and &quot;below&quot; where the Earth hangs in space? What stuff is there in both areas?

      My concept of space is informed by the hammock analogy where gravity is the result of the bodies&#x27; mass&#x2F;density causing the fabric to sag and draw in approaching objectz

      1. pas · · focus · HN ↗
        space is 3D, but the information content can be encoded on a 2D hologram. general relativity works, mass-energy is curving spacetime, it just happens to do it in a way, that these curves and slopes and ... the whole 3D geometry can be flattened to 2D without loss of information.
        1. Obscurity4340 · · focus · HN ↗
          So is there stuff below and above Earth
          1. qnleigh · · focus · HN ↗
            Yes, lots and lots of stuff. For all we know, space may extend infinitely in all directions.
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