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. ReflectedImage · 1790383246 · focus · HN ↗

         A 3d volume can contain a number of states equal to it's 2d dimensional surface.

         All the extra states you would assume the 3d volume can contain are actually a single state called Black Hole.

         There is a limit to how much you can fill a 3d volume before it's a Black Hole basically.

         1. api · 1790384538 · focus · HN ↗

            That's the clearest description of how this dimension collapse via gravity thing works that I've ever heard.

            I really think we live on the 3D event horizon of a 4D black hole, folks.

            1. rbanffy · 1790415535 · focus · HN ↗

               Why stopping at four dimensions?

               1. api · 1790419158 · focus · HN ↗

                  Oh sure. The parent universe could be the 4D event horizon of a 5D hole. It’s holes all the way up. If you draw little heads on them I guess they’re like round turtles so if this is true the turtles people weren’t as far off as we thought.

                  Since all the event horizons “touch” at N-1 dimensions I wonder if this is isomorphic with certain forms of string theory? Maybe there’s 11 levels of holes?

                  BTW this isn’t my idea. There’s papers on black hole cosmology. You can make the math work but no way to test it. Yet?

                  1. mjanx123 · 1790421943 · focus · HN ↗

                     Legs, also little legs.
               2. tclancy · 1790435839 · focus · HN ↗

                  The people at Gillette are working on five.

                  1. junkblocker · 1790452596 · focus · HN ↗

                     That's old news. They solved five a while ago.

                     1. rbanffy · 1790455879 · focus · HN ↗

                        I heard they were researching up to 18, but most of the blades were curved and really short.

Unofficial Hacker News client; not affiliated with Y Combinator.