The holographic principle — the idea that everything happening inside a region of space can be fully reconstructed from measurements on its surface — is now regarded by many physicists as the most profound proposal in theoretical physics of the last three decades. Quanta Magazine published a long-form essay on 25 September exploring the principle's evidence, interpretations, and open questions.
The mathematical backbone is the AdS/CFT correspondence: three landmark papers from the late 1990s proved that a gravitational universe inside an anti-de Sitter 'snow globe' is exactly equivalent to a non-gravitational quantum theory on its boundary. The two descriptions encode the same information, meaning the three-dimensional interior and the two-dimensional surface are interchangeable. Leonard Susskind, who proposed that black holes are literal holograms in the 1990s, called it 'the least crazy of all the possibilities.'
Physicists offer three ontological interpretations: (1) the surface is fundamental and three-dimensional space is emergent (the 'it from qubit' view), (2) the volume is fundamental and holography is a mathematical coincidence, or (3) neither description is truly fundamental and a deeper theory underlies both. Most holographers lean toward the first — space itself may be made of quantum information, much like pixels on a screen.
The biggest open question is extending the principle beyond anti-de Sitter space. Our universe is approximately de Sitter (expanding, with no boundary surface), and no complete holographic theory exists for it. Recent progress by Susskind and others suggests that de Sitter holography may project all dimensions not onto a surface but into a single quantum point — a radical restructuring that, if validated, would reshape our understanding of space and time.
