Thread

1. anigbrowl · 1790380260 · focus · HN ↗

   Pause for a moment to reflect on how outrageous this assertion is. You can’t see into the box at all. Nevertheless, holography says that you can learn exactly what’s happening everywhere in the box without any access to the interior. Observing the surface alone is enough. In this sense, the amount of stuff that fills a box is the same as the amount of paint that covers it. That’s a violation of logic and geometry.

   The breathless tone of this article obscures rather than illuminates its subject. It sounds as if the author describes a box with some particles bouncing around inside, and every time a particle bounces off the wall of the box the outside glows briefly indicating the location and intensity of the collision. The author is amazed that by repeatedly measuring this, you can draw inferences about what's going on in the box.

   I can't see what's 'outrageous' about this. You need a lower surface which registers information about activity inside a higher-dimensional volume, some way to accurately read that information, and the time/patience to repeat the measurement many times. Isn't this how radar works, or feeling your way around a pitch-dark room using only the 2-dimensional surface of your hands (or shins)? We know from computer science that you can mathematically encode any structure of arbitrary dimension into a binary tree. One might as well ask how it's possible that our complex 3 dimensional world can be contained in the flat surface of a mirror, film strip, or camera sensor.

   1. pimlottc · 1790381917 · focus · HN ↗

      It’s not just drawing inferences, though; it’s saying you can determine exactly what’s happening in the box. But the pigeonhole principle would suggest there’s far more possible states in the 3-dimension volume than can be unique expressed on the 2-dimensional surface. That’s the part that defies common sense.

      1. senderista · 1790382804 · focus · HN ↗

         Is it any weirder than the fact that there is a bijection between the unit interval and the unit square?

         1. dnautics · 1790394126 · focus · HN ↗

            Yeah because you can prove that any such bijection cannot be a topological homeomorphism, for example. So necessarily some "nice to have" properties must drop out.

            1. zmgsabst · 1790428932 · focus · HN ↗

               Those drop out in holography too — eg, information local within the interior can get smeared out across the surface.

               1. senderista · 1790442514 · focus · HN ↗

                  That is exactly what I was wondering about in my other comment: is physical nonlocality somehow equivalent to topological noncontinuity?

                  1. dnautics · 1790461930 · focus · HN ↗

                     I am not a physicist but i presume that is the hope of some who pursue holographic modes

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