Perhaps there is no greater illustration of Nature’s subtlety than what we call the holographic principle. This principle says that, in a sense, all the information that is stored in this room, or any room, is really encoded entirely and with perfect accuracy on the boundary of the room, on its walls, ceiling and floor. Things just don’t seem that way, and if we underestimate the subtlety of Nature we’ll conclude that it can’t possibly be true. But unless our current ideas about the quantum theory of gravity are on the wrong track, it really is true. It’s just that the holographic encoding of information on the boundary of the room is extremely complex and we don’t really understand in detail how to decode it. At least not yet.And then comments:
This holographic principle, arguably the deepest idea about physics to emerge in my lifetime, is still mysterious. How can we make progress toward understanding it well enough to explain it to freshmen?
From what I can tell, the problem is not that it can’t be explained to freshmen, but that it can’t be explained precisely to anyone, since it is very poorly understood.I left this comment:
What is so profound about saying that things may be determined by boundary data? My textbooks are filled with boundary value and initial value problems. Some are centuries old. The boundary of a black hole mixes space and time, so the distinction between the 2 kinds of problems may not be so clear. But either way, a lot of physical theories say that things are determined by data on one lower dimension.He deleted my comment, so I am posting it here. After that, someone posted a similar comment:
On the topic of the holographic principle being held in such high regard, I have a naive question. What is the difference between the holographic principle and specifying the physics via boundary conditions? “all information in the room is in the walls” seems like an obvious quote given that the fundamental field equations are second order and hence are uniquely specified by giving the values of the fields on the boundary of the region?I do not think that his answer is very satisfactory, but you are welcome to read it.