[ExI] NEW SCIENTIST: Our world may be a giant hologram

[Michael LaTorra]

Our world may be a giant hologram
15 January 2009 by Marcus Chown

DRIVING through the countryside south of Hanover, it would be easy to miss
the GEO600 experiment. From the outside, it doesn't look much: in the corner
of a field stands an assortment of boxy temporary buildings, from which two
long trenches emerge, at a right angle to each other, covered with
corrugated iron. Underneath the metal sheets, however, lies a detector that
stretches for 600 metres.

For the past seven years, this German set-up has been looking for
gravitational waves - ripples in space-time thrown off by super-dense
astronomical objects such as neutron stars and black holes. GEO600 has not
detected any gravitational waves so far, but it might inadvertently have
made the most important discovery in physics for half a century.
For many months, the GEO600 team-members had been scratching their heads
over inexplicable noise that is plaguing their giant detector. Then, out of
the blue, a researcher approached them with an explanation. In fact, he had
even predicted the noise before he knew they were detecting it. According to
Craig Hogan, a physicist at the Fermilab particle physics lab in Batavia,
Illinois, GEO600 has stumbled upon the fundamental limit of space-time - the
point where space-time stops behaving like the smooth continuum Einstein
described and instead dissolves into "grains", just as a newspaper
photograph dissolves into dots as you zoom in. "It looks like GEO600 is
being buffeted by the microscopic quantum convulsions of space-time," says
Hogan.

If this doesn't blow your socks off, then Hogan, who has just been appointed
director of Fermilab's Center for Particle Astrophysics, has an even bigger
shock in store: "If the GEO600 result is what I suspect it is, then we are
all living in a giant cosmic hologram."

The idea that we live in a hologram probably sounds absurd, but it is a
natural extension of our best understanding of black holes, and something
with a pretty firm theoretical footing. It has also been surprisingly
helpful for physicists wrestling with theories of how the universe works at
its most fundamental level.

The holograms you find on credit cards and banknotes are etched on
two-dimensional plastic films. When light bounces off them, it recreates the
appearance of a 3D image. In the 1990s physicists Leonard Susskind and Nobel
prizewinner Gerard 't Hooft suggested that the same principle might apply to
the universe as a whole. Our everyday experience might itself be a
holographic projection of physical processes that take place on a distant,
2D surface.

The "holographic principle" challenges our sensibilities. It seems hard to
believe that you woke up, brushed your teeth and are reading this article
because of something happening on the boundary of the universe. No one knows
what it would mean for us if we really do live in a hologram, yet theorists
have good reasons to believe that many aspects of the holographic principle
are true.

Susskind and 't Hooft's remarkable idea was motivated by ground-breaking
work on black holes by Jacob Bekenstein of the Hebrew University of
Jerusalem in Israel and Stephen Hawking at the University of Cambridge. In
the mid-1970s, Hawking showed that black holes are in fact not entirely
"black" but instead slowly emit radiation, which causes them to evaporate
and eventually disappear. This poses a puzzle, because Hawking radiation
does not convey any information about the interior of a black hole. When the
black hole has gone, all the information about the star that collapsed to
form the black hole has vanished, which contradicts the widely affirmed
principle that information cannot be destroyed. This is known as the black
hole information paradox.

Bekenstein's work provided an important clue in resolving the paradox. He
discovered that a black hole's entropy - which is synonymous with its
information content - is proportional to the surface area of its event
horizon. This is the theoretical surface that cloaks the black hole and
marks the point of no return for infalling matter or light. Theorists have
since shown that microscopic quantum ripples at the event horizon can encode
the information inside the black hole, so there is no mysterious information
loss as the black hole evaporates.
Crucially, this provides a deep physical insight: the 3D information about a
precursor star can be completely encoded in the 2D horizon of the subsequent
black hole - not unlike the 3D image of an object being encoded in a 2D
hologram. Susskind and 't Hooft extended the insight to the universe as a
whole on the basis that the cosmos has a horizon too - the boundary from
beyond which light has not had time to reach us in the 13.7-billion-year
lifespan of the universe. What's more, work by several string theorists,
most notably Juan Maldacena at the Institute for Advanced Study in
Princeton, has confirmed that the idea is on the right track. He showed that
the physics inside a hypothetical universe with five dimensions and shaped
like a Pringle is the same as the physics taking place on the
four-dimensional boundary. ...

...continues at:

http://www.newscientist.com/article/mg20126911.300-our-world-may-be-a-giant-hologram.html
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