What is the holographic principle?

The holographic principle is a concept in theoretical physics that suggests that the information contained within a volume of space can be represented by data encoded on the boundary of that region, much like a hologram. In essence, it posits that the three-dimensional information about a physical system can be fully described by two-dimensional information living on the boundary of that system. This idea has significant implications for our understanding of the nature of space, time, and gravity, particularly in the context of black holes and quantum gravity. The holographic principle originated from the work of scientists like Gerard 't Hooft and Leonard Susskind in the 1990s and was motivated, in part, by the study of black hole thermodynamics. Notably, it was found that the entropy of a black hole (a measure of the amount of information that can be contained within it) is proportional to the area of its event horizon rather than its volume, suggesting that a black hole's information is encoded on its surface. The principle has also been connected to string theory and quantum field theory, where it provides a framework for understanding how gravity and quantum mechanics may be reconciled. Thus, the holographic principle challenges conventional notions of dimensionality and locality in physics, suggesting that our perception of a three-dimensional universe might emerge from more fundamental two-dimensional physics.