The scientific conjecture that the universe is just one big 3D projection of a 2D flat universe. First proposed in 1997 by theoretical physicist Juan Maldacena, the holographic model describes a universe in which gravity arises from infinitesimally thin, vibrating strings, which exist in nine dimensions of space plus one of time, would merely be a hologram. In the hologram, the real action would play out in a simpler, flatter cosmos where there is no gravity. In essence, the holographic principle suggests that, like the security chip on a credit card which is a two-dimensional surface but it contains all the information needed to describe a three-dimensional object - which in this case is the universe.

The holographic idea excites physicists because it offers a way to put popular but still unproven theory of strings on a more solid footing and solves apparent inconsistencies between quantum physics and Einstein's theory of gravity. It provides physicists with a mathematical 'duality' allowing them to translate back and forth between the two languages, and solve problems in one model that seems intractable in the other and vice versa. Although the validity of Maldacena's ideas has pretty much been taken for granted ever since, a rigorous proof has been elusive.