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by Elizabeth Howell
September 18, 2013
from
UniverseToday Website
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Artist's
conception of the event horizon of a black hole.
Credit: Victor de
Schwanberg/Science Photo Library
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Could the famed "Big Bang" theory need a revision?
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A group of theoretical physicists
suppose the birth of the universe could have happened after a
four-dimensional star collapsed into a black hole and ejected
debris.
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Before getting into their findings,
let's just preface this by saying nobody knows anything for sure.
Humans obviously weren't around at the time the universe began.
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The standard theory is that the
universe grew from an 'infinitely dense point' or
Singularity, but
who knows what was there before?
"For all physicists know, dragons
could have come flying out of the singularity," stated Niayesh
Afshordi, an astrophysicist with the Perimeter Institute for
Theoretical Physics in Canada who co-authored the new study.
So what are the limitations of the Big
Bang theory?
The Singularity is one of them.
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Also, it's hard to predict why it would
have produced a universe that has an almost uniform temperature,
because the age of our universe (about 13.8 billion years) does not
give enough time - as far as we can tell - to reach a temperature
equilibrium.
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Most cosmologists say the universe must
have been expanding faster than the speed of light for this to
happen, but Niayesh Ashford says even that theory has
problems:
"The Big Bang was so chaotic, it's
not clear there would have been even a small homogenous patch
for inflation to start working on."
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Representation
of the timeline of the universe over 13.7
billion years, from the Big Bang, through
the cosmic dark ages and formation of the
first stars, to the expansion in the
universe that followed.
Credit:
NASA/WMAP Science Team.
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This is what the physicists propose:
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The model they constructed has
the three-dimensional universe floating as a membrane (or
brane) in a "bulk universe" that has four dimensions. (Yes,
this is making our heads hurt as well, so it might be easier
to temporarily think of the brane as two-dimensional and the
"bulk universe" as three-dimensional when trying to picture
it.) You can read the more technical details
in this 2000 paper on which the new theory is based.
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So if this "bulk universe" has
four-dimensional stars, these stars could go through the
same life cycles as the three-dimensional ones we are
familiar with. The most massive ones would
explode as supernovae, shed their skin and have the
innermost parts collapse as a black hole.
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The 4-D black hole would have an
"event horizon" just like the 3-D ones we are familiar with.
The event horizon is the
boundary between the inside and the outside of a black hole.
There are a lot of theories of what goes on inside a black
hole, although nothing has ever been observed.
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In a 3-D universe, the event
horizon appears as a two-dimensional surface. So in a 4-D
universe, the event horizon would be a 3-D object called a
hypersphere.
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So basically, what the model
says is when the 4-D star blows apart, the leftover material
would create a 3-D brane surrounding a 3-D event horizon,
and then expand.
The long and the short of it?
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To bring this back to things that we can
see, it is clear from observations
that the universe is expanding (and indeed is getting faster as
it expands, possibly due to the
mysterious dark energy). The new theory says that the expansion
comes from this 3-D brane's growth.�
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But there �is at least one limitation.
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This artist's
impression shows the surroundings of the
supermassive black hole at the heart of the
active galaxy NGC 3783 in the southern
constellation of Centaurus (The Centaur).
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New observations
using the Very Large Telescope
Interferometer at ESO's Paranal Observatory
in Chile have revealed not only the torus of
hot dust around the black hole but also a
wind of cool material in the polar regions.
Credit:
ESO/M. Kornmesser
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While the model does explain why the
universe has nearly uniform temperature (the 4-D universe preceding
it would have existed it for much longer), a European Space Agency
telescope called Planck recently
mapped small temperature variations in the cosmic microwave
background (CMB), which is believed to be leftovers of the universe's
beginnings.
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The new model differs from these
CMB
readings by about four percent, so the researchers are looking to
refine the model. They still feel the model has worth, however.
Planck shows that inflation is happening, but doesn't show�why�the
inflation is happening.
"The study could help to show how
inflation is triggered by the motion of the universe through a
higher-dimensional reality," the researchers stated.
You can read more about their research
on the prepublished Arxiv paper "Out
of the White Hole - A Holographic Origin for the Big Bang".
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The Arxiv entry does not specify if
the paper has been submitted to any peer-reviewed scientific
journals for publication.
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