String Theory: Inside a Hologram
A hologram is a 2dimensional image that contains all the 3dimensional information of an object. When viewing a hologram, you can tilt the image and see the orientation of the shape move. It’s as if you see the object in the picture from a different angle. The process of making a hologram is called holography.
This is achieved through the interference patterns in light waves. The process involves using a laser — so all of the light has exactly the same wavelength — and reflecting it off of the object onto a film.
As the light strikes the film, it records interference patterns that, when properly developed, allow the film to encode the information about the 3dimensional shape that was holographed. The encoded information then has to be decoded, which means the laser light again has to be shown through the film in order to see the image.
“White light” holograms exist, which don’t need laser light to view them. These are the holograms that you’re most familiar with, which manifest their image in ordinary light.
The holographic principle is totally unexpected. You’d think that the information needed to describe a space would be proportional to the volume of that space. (Note that in the case of more than three space dimensions, “volume” isn’t a precise term. A 4dimensional “hypervolume” would be length times width times height times some other space direction. For now, you can ignore the time dimension.)
You can consider this principle in two ways:

Our universe is a 4dimensional space that is equivalent to some 3dimensional boundary.

Our universe is a 4dimensional boundary of a 5dimensional space, which contains the same information.
In scenario 1, we live in the space inside the boundary, and in scenario 2, we are on the boundary, reflecting a higher order of reality that we don’t perceive directly. Both theories have profound implications about the nature of the universe we live in.