Our eyes see depth because light from different distances arrives slightly out of phase. Photos only store light intensity, so they don’t show depth, but holograms can show depth by storing the phase differences that encode it. A hologram is made by splitting laser light and letting the half that shines on the object interfere with the other half, to give a pattern (Figure 3.24). Light later shone on that pattern recreates the original object as a hologram.
The holographic principle is that we observe our universe like a hologram, or more precisely:
“Everything physically knowable about a volume of space can be encoded on a surface surrounding it” (Bekenstein, 2003).
This principle, widely accepted in physics, is that everything we observe about our world can be encoded on a flat surface, just like a hologram. The information in a space seems to depend on its volume, but if more and more memory chips are packed into a space, to increase its information, the end result is a black hole whose entropy depends on its surface area, not its volume.
Entropy, in physics, measures system disorder and directly relates to information. Black holes have more entropy than anything else, for a given volume, so the information of any physical object depends on its two-dimensional surface, not its volume. It follows that the holographic principle is maintained by the behavior of black holes (Bekenstein, 2003).
It is therefore interesting that if our world is a virtual reality, the same result applies. Every virtual event has to be observed from some direction, so the act of observing uses up one of the dimensions of space, which leaves only two dimensions to transfer the information of the observation. It follows that the information transferred to a point in a three-dimensional virtual world can always be painted on the surface of a sphere around it, because that is the way it is delivered. That our physical world is a virtual reality then requires the holographic principle, and conversely, that the holographic principle applies to our world supports the idea that it is virtual.
Does this result make our universe two-dimensional? The holographic principle just states that our world presents in two dimensions, not that it operates as such, so space still has three degrees of freedom. In our world, every observation comes from some direction, leaving only two dimensions to deliver the information across. The holographic principle implies that our world is virtual, not that it is two dimensional. It describes how physical events are observed, not how our space works.
Equally to imagine that our world is like a hologram is misleading. This is no Star Trek hologram that we can enter and leave at will, because our bodies are its images. If we left this hologram, or if it ever switched off, our bodies would disappear, along with everything else physical. The only way then to recover it would be to start it again from scratch, which last happened over fourteen billion years ago.