*Paul Sutter is an astrophysicist at The Ohio State University and the chief scientist at COSI science center. Sutter is also host of Ask a Spaceman and Space Radio, and leads AstroTours around the world. Sutter contributed this article to Space.com’s Expert Voices: Op-Ed & Insights.*

In the late 1990s, theoretical physicists uncovered a remarkable connection between two seemingly unrelated concepts in theoretical physics. That connection is almost inscrutably technical, but it might have far-reaching consequences for our understanding of gravity and even the universe.

To illustrate this connection, we’re going to start at — of all places — a black hole. Researchers have found that when a single bit of information enters a black hole, its surface area increases by a very precise amount: the square of the Planck length (equal to an incredibly small 1.6 x 10^-35 meters on a side). [Are We Living in a 2D Hologram? Photos of Laser ‘Holometer’ Experiment (Gallery)]

At first blush, it may not seem all that interesting that a black hole gets larger when matter or energy falls into it, but the surprise here is that it’s the surface area, not the volume, that grows in direct proportion to the infalling information, which is totally unlike most other known object in the universe. For most objects that we’re familiar with, if it “consumes” one bit of information, its volume will grow by one unit, and its surface area by a only a fraction. But with black holes, the situation is reversed. It’s like that information isn’t inside the black hole, but instead stuck to its surface.

Thus, a black hole, a fully three-dimensional object in our three-dimensional universe, can be completely represented by just its two-dimensional surface. And that’s how holograms work.

## A black hol-ogram

A hologram is a representation of a system using fewer dimensions that can still pack in all the information from the original system. For example, we live in three (spatial) dimensions. When you’re posing for a selfie, the camera records a two-dimensional representation of your face, but it doesn’t capture all the information; when you later examine your handiwork and choose your filter, you can’t, for example, see the back of your head, no matter how you rotate the picture.

Recording a hologram would preserve all that information. Even though it’s a two-dimensional representation, you would still be able to examine it from all three dimensional angles.

Describing a black hole as a hologram might provide a solution to the so-called black-hole information paradox, the puzzle of where the information goes when matter is consumed by a black hole. But that’s the subject of another article. The black-hole-as-hologram concept is also a good example to keep in your head as we make the big jump — to consider the entire universe. [The Strangest Black Holes in the Universe]