One of the great challenges facing physics is the unification, or rather, the reconciliation of quantum mechanics and gravity. The conflict between these two fields has manifested on multiple occasions, but beyond the differences, experts continue working to find that valuable piece of the puzzle that still eludes us. The so-called holographic principle is part of the search, and in very relaxed terms it proposes that we exist as two-dimensional information on the edge of the universe, while the universe itself is an expression of that information... a 3D hologram, so to speak.
The world of physics was completely shaken when a young scientist named Stephen Hawking admitted that everything that falls into a black hole, including its information, is lost completely and impossible to recover. Quantum mechanics experts automatically saw this as a paradox, and to put it a certain way... they did not agree with Hawking. One of those experts is Leonard Susskind, who said Hawking was wrong because his conclusion violates one of the fundamental laws of the universe, which is the conservation of information.
Susskind wrote a book about his "battle" with Hawking, "The Black Hole War", which is highly recommended for anyone wanting to know more. The differences between Hawking and Susskind (beyond the subsequent debate) led to what is now known as the holographic principle, presented by physicist Gerard 't Hooft and Susskind himself, which the world seems to have interpreted as follows: The universe... is a hologram.
The holographic universe
But before continuing with the universe, let's go back to black holes. Through the holographic principle, 't Hooft and Susskind developed the idea that when an object falls into a black hole, the event horizon takes on the role of a "photographic film", storing an exact copy of the object, and what fell in is its three-dimensional image.
In other words, the object is in two places at the same time, but the most interesting thing is that the holographic principle does not apply exclusively to black holes, but also extends to the entire universe. Everything we touch, see, and feel is a 3D projection of the information stored on the cosmological boundary. So... what is the real version? According to Susskind, it doesn't matter. The math indicates that both are equivalent, but it's a question we can't ignore.
The same goes for the next question: What are the chances that it's true? Recent studies based on analysis of cosmic microwave background radiation applied the holographic principle to predict the lack of uniformity (specific deviations) in that background, and their results were much more precise than expected. Obviously, we're barely scratching the surface here, and it will take extra years of study to confirm or deny the validity of the holographic principle. Until then... "computer, end program?"
