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Posted by: admin
on Nov 24, 2009
Tagged in: Untagged
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The flatness problem relates to the density parameter of the Universe, W. Values for W can take on any
number between 0.01 and 5 (lower than 0.01 and galaxies can't form, more than
5 and the Universe is younger than the oldest rocks). The measured value is
near 0.2. This is close to an W of 1, which is
strange because W of 1 is an unstable point for the
geometry of the Universe.
- values of Omega near 1 are unstable and require a mechanism
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Values slightly below or above 1 in the early Universe rapidly grow to
much less than 1 or much larger than 1 (like a ball at the top of a hill).
So the fact that the measured value of 0.2 is so close to 1 that we expect
to find in the future that our measured value is too low and that the
Universe has a value of W exactly equal to 1
for stability. And therefore, the flatness problem is that some mechanism
is needed to get a value for W to be exactly
one (to balance the pencil). |
- opposites of the Universe should not be connected, they are outside each others horizon
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The horizon problem concerns the fact that the Universe is isotropic. No
matter what distant corners of the Universe you look at, the sizes and
distribution of objects is exactly the same (the Cosmological
Principle). But there is no reason to expect this since opposite sides
of the Universe are not causally connected, any information that is
be transmitted from one side would not reach the other side in the
lifetime of the Universe (limited to travel at the speed of light).
All the Universe has an origin at the Big Bang, but time didn't exist
until after the Planck era. And by the end of that epoch, the Universe
was already expanding such that opposite sides were not causally
connected. |
- an era of inflation solves both these problems, the rapid expansion of the Universe during the GUT symmetry
breaking
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The solution to both the flatness and horizon problems is due to a phase
of the Universe called inflation. Currently, inflation is the only theory
that explains why the observable Universe is both homogeneous and causally
connected. During inflation the Universe expanded a factor of 1054, so that our horizon now only sees a small piece
of what was the total Universe from the Big Bang.
The cause of the inflation era was the symmetry breaking at the GUT
unification point. At this moment, spacetime and matter separated and a
tremendous amount of  energy was released. This energy produced an
overpressure that was applied not to the particles of matter, but to
spacetime itself. Basically, the particles stood still as the space
between them expanded at an exponential rate. |
- inflation occurs at faster than the speed of light, but there is no motion since the space under the matter
expands, objects do not move
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Note that this inflation was effectively at more than the speed of
light, but since the expansion was on the geometry of the Universe
itself, and not the matter, then there is no violation of special
relativity. Our visible Universe, the part of the Big Bang within our
horizon, is effectively a `bubble' on the larger Universe. However,
those other bubbles are not physically real since they are outside our
horizon. We can only relate to them in an imaginary, theoretical sense.
They are outside our horizon and we will never be able to communicate
with those other bubble universes. |
- the endresult is the formation of many bubble universes inside a large Multiverse
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Notice how this solves the horizon problem in that our present Universe was
simply a small piece of a larger Big Bang universe that was all in causal
connection before the inflation era. Other bubble universes might have
very different constants and evolutionary paths, but our Universe is
composed of a small, isotropic slice of the bigger Big Bang
universe. |
- both horizon and flatness problems are resolved by inflation
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Inflation also solves the flatness problem because of the exponential growth.
Imagine a highly crumbled piece of paper. This paper represents the Big
Bang universe before inflation. Inflation is like zooming in of some
very, very small section of the paper. If we zoom in to a small enough
scale the paper will appear flat. Our Universe must be exactly flat for
the same reason, it is a very small piece of the larger Big Bang
universe. |
- inflation forces curvature to zero and requires a cosmological constant for a low matter density Universe
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Thus, inflation resolves both the horizon and flatness problems. There is good
reason to believe that the early Universe must go through an inflation-like event
due to phase changes from symmetry breaking. Curvature is forced to flat (k=0) which means matter density and the
cosmological constant must sum to one. |
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