Gravity May Be Holographic, and That Would Mean Space Isn't What It Seems
Gravity Seems Holographic. What Does That Mean for Reality?
The holographic principle suggests that everything inside a region of space can be reconstructed from its surface alone — a radical idea that has become one of the most cited proposals in theoretical physics. This essay traces the evidence from black hole entropy to the AdS/CFT correspondence, weighs skeptics' objections, and asks what it would mean for our universe if gravity truly is holographic.
It asks us to erase the categorical difference between square meters and cubic meters.
- anigbrowl
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 camer […]
- senderista
I don't think the author has relevant scientific background and it's frustrating this wasn't written by one of the Quanta journalists who does.
- SA9G
Fascinating article... reminds me once again why I went into EE/CS instead of physics, I just wasn't smart enough :-(
- VyseofArcadia
Mathematician, not physicist, but it seems reasonable to me that you could encode a sufficiently constrained 3D space on a 2D boundary. And if you have such an encoding, it also doesn't seem insane that some things might be more easily modeled on the 2D boundary than the 3D space.
If you can convert back and forth between a 2D representation and a 3D representation, and different phenomena are more easily modeled in each, does it matter which is "real"? Unless of course you can come up with a specific prediction and experiment to test it.
- analog31
This is cool, but I've noticed that an idea of a "holographic universe" makes the news roughly once a decade.
Maybe fifth time's the charm. ;-)
- tananaev
I think the box explanation is misleading. There isn't literally a box whose surface you measure. The idea is that the state of a higher-dimensional gravitational system can, in some cases, be completely described by a theory in one fewer dimension.
- glenstein
As a non expert who's just curious about science but also tries to talk like a normal person, from what I can tell holography really seems like it's now the leading candidate to be the next big conceptual revolution in physics.
There's not necessarily any breakthrough right around the corner and we shouldn't rush to coronation preemptively, but there's a lot of physics "voting with their feet" for holography as the article says, and I think it's officially time to start getting hyped. It could have sanity-restoring answers to questions of quantum weirdness, albeit at the rather expensive cost of giving up even more on our day to day intuitions about space and time in favor of an apparently informational substrate.
String theory had a generation of great science communicators writing its books and singing its praises, but holography doesn't yet have equivalent public champions, and I hope that's something that changes sooner than later.
- wateralien
To me (a total physics layperson with just an interest in it) space and time HAVE to be emergent and not fundamental because of the real phenomena of spooky action at a distance and dual slit craziness. All spacetime surely has to be connected is what it’s telling us.