A team of physicists has found evidence to support an idea long theorized by philosophers and stoners alike that the universe might actually be one big holographic projection.
Theoretical physicist Juan Maldacena proposed in 1997 that gravity is the result of vanishingly small, vibrating strings that that exist in nine dimensions of space and one of time.
If that were the case, then the universe would essentially be a hologram – a simpler, flatter cosmos without gravity – that is perceived much the same way that Plato described in his Allegory of the Cave.
“The work culminated in the last decade, and it suggests, remarkably, that all we experience is nothing but a holographic projection of processes taking place on some distant surface that surrounds us,” wrote physicist Brian Greene, of Columbia University. “You can pinch yourself, and what you feel will be real, but it mirrors a parallel process taking place in a different, distant reality.”
Plato compared human perception to some ancient cave-dweller watching shadows flicker across a dimly lit wall, and Green suggests that his metaphor may describe a reality that theoretical physicists are just beginning to map out.
“Reality -- not its mere shadow -- may take place on a distant boundary surface, while everything we witness in the three common spatial dimensions is a projection of that faraway unfolding,” Greene wrote. “Reality, that is, may be akin to a hologram. Or, really, a holographic movie.”
The holographic principle suggests there’s a two-dimensional surface that contains all the information needed to describe a three-dimensional object – even the universe.
Physicists have been fascinated with Maldacena’s hologram conjecture because it could help prove string theory and solve inconsistencies between quantum physics and Albert Einstein’s theory of gravity.
Einstein understood that space and time were bound together as spacetime and theorized that they could be warped by massive objects – much like a heavy ball dropped onto a trampoline.
General relativity describes planets and galaxies, but quantum mechanics zooms in to the subatomic scale and the fundamental particles that make up matter – and gravity is negligible at that level.
The quantum field theory of particle physics holds that one fundamental particle exerts force on another by sending over messenger particles called gauge bosons, which has been observed in three of the fundamental forces -- the electromagnetic force, the weak nuclear force and the strong nuclear force.
But physicists have not observed gravity’s hypothetical messenger particle, the graviton.
The idea that fundamental particles are actually tiny vibrating strings allows physicists to work around mathematical problems in quantum gravity, but there are many physical qualities that string theories can’t describe – and physicists had not been able to test them.
Maldacena may have solved the riddle by imagining gravity as an illusion conjured up by a quantum hologram, and his conjecture has been accepted as valid for years.
New calculations published by Japanese physicists from Ibaraki University make the same predictions as Maldacena's 10-dimensional model, but in fewer dimensions.
For one study, physicist Yoshifumi Hyakutake and his colleagues created a computer model of a black hole – which is formed when a large amount of mass is concentrated in a tiny region of space and creates a gravitational pull so strong that not even light can escape.
They computed the internal energy of a black hole, the position of its event horizon – or the boundary between the black hole and the rest of the universe -- its entropy and other properties based on string theory predictions and other factors.
In the other study, Hyakutake and his team calculated the internal energy of the corresponding lower-dimensional cosmos without gravity.
Significantly, they found the two computer calculations matched.
“They have numerically confirmed, perhaps for the first time, something we were fairly sure had to be true, but was still a conjecture -- namely that the thermodynamics of certain black holes can be reproduced from a lower-dimensional universe,” said Leonard Susskind, a theoretical physicist at Stanford University.
What this means is that there may be physical processes taking place on some distant surface that can be perceived as three-dimensional reality.
Or, put even more simply, it’s possible that what we call reality is actually a hologram projected onto the surface of a black hole in which our universe exists.
Maldacena, who now works at the Institute for Advanced Study in Princeton, New Jersey, said the works appears to be a correct computation.
“(The findings) are an interesting way to test many ideas in quantum gravity and string theory,” Maldacena said, noting that the Japanese team had worked for several years to test the theory. “The whole sequence of papers is very nice because it tests the dual (nature of the universes) in regimes where there are no analytic tests.”
Neither model universe resembles our own, Maldacena said.
The cosmos with the black hole has 10 dimensions, he pointed out, with eight of them forming an eight-dimensional sphere.
The gravity-free universe has only one dimension with quantum particles resembling a group of springs attached to one another.
However, Maldacena said, the numerical proof suggests that our own universe can one day be explained purely in terms of quantum theory.
“I view this idea as a model, but it's a model that gives a mathematical description of quantum spacetime,” he said in a previous interview. “So we should take it seriously until someone refutes it, or comes up with something better."
[Image via Agence France-Presse]