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A
team of physicists has provided some of the clearest evidence yet that our
Universe could be just one big projection.

In
1997, theoretical physicist Juan Maldacena proposed that
an audacious model of the Universe in which gravity arises from infinitesimally
thin, vibrating strings could be reinterpreted in terms of well-established
physics. The mathematically intricate world of strings, which exist in nine
dimensions of space plus one of time, would be merely a hologram: the real
action would play out in a simpler, flatter cosmos where there is no gravity.

Maldacena's
idea thrilled physicists because it offered a way to put the popular but still
unproven theory of strings on solid footing — and because it solved apparent inconsistencies
between quantum physics and Einstein's theory of gravity. It provided
physicists with a mathematical Rosetta stone, a 'duality', that allowed them to
translate back and forth between the two languages, and solve problems in one
model that seemed intractable in the other and vice versa (see 'Collaborative
physics: String theory finds a bench mate'). But although the validity of
Maldacena's ideas has pretty much been taken for granted ever since, a rigorous
proof has been elusive.

In
two papers posted on the arXiv repository, Yoshifumi Hyakutake of Ibaraki
University in Japan and his colleagues now provide, if not an actual proof, at
least compelling evidence that Maldacena’s conjecture is true.

In
one paper , Hyakutake computes the internal energy of a black hole, the
position of its event
horizon (the boundary between the black hole and the rest of the
Universe), its entropy and other properties based on the predictions of string
theory as well as the effects of so-called virtual particles that continuously
pop into and out of existence (see 'Astrophysics: Fire in
the Hole!'). In the other paper,
he and his collaborators calculate the internal energy of the corresponding
lower-dimensional cosmos with no gravity. The two computer calculations match.

“It
seems to be a correct computation,” says Maldacena, who is now at the Institute
for Advanced Study in Princeton, New Jersey and who did not contribute to the
team's work.

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The
findings “are an interesting way to test many ideas in quantum gravity and
string theory”, Maldacena adds. The two papers, he notes, are the culmination
of a series of articles contributed by the Japanese team over the past few
years. “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.”

“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,” says Leonard Susskind, a theoretical physicist at
Stanford University in California who was among the first theoreticians to
explore the idea of holographic universes.

Neither
of the model universes explored by the Japanese team resembles our own,
Maldacena notes. The cosmos with a black hole has ten dimensions, with eight of
them forming an eight-dimensional sphere. The lower-dimensional, gravity-free
one has but a single dimension, and its menagerie of quantum particles
resembles a group of idealized springs, or harmonic oscillators, attached to
one another.

Nevertheless,
says Maldacena, the numerical proof that these two seemingly disparate worlds
are actually identical gives hope that the gravitational properties of our
Universe can one day be explained by a simpler cosmos purely in terms of
quantum theory.

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**Nature**]
Einstein's theory of relativity maybe.Sir Issac Newton had gravity first.I'm not saying Einstine may have gone further.An I have seen this said several times.I just wasn't taught Eistines theory of gravity but sir Issac Newton s was always taught.

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