Universe(s) Origin(s) 5 of 7 - Cyclic Universe?
(Top Posts - Science - 072802)

Excerpts from "New Theory Provides Alternative To Big
Bang " (Princeton physicist Paul Steinhardt and Neil Turok
of Cambridge University, April 29, 2002) ...
http://www.sciencedaily.com/releases/2002/04/020429080540.htm

A new theory of the universe suggests that space and time
may not have begun in a big bang, but may have always
existed in an endless cycle of expansion and rebirth.

---
Further information and a graphic animation
of the cyclic scenario:
http://feynman.princeton.edu/~steinh/
---

... The theory proposes that, in each cycle, the universe refills
with hot, dense matter and radiation, which begins a period of
expansion and cooling like the one of the standard big bang
picture.

After 14 billion years, the expansion of the universe accelerates,
as astronomers have recently observed. After trillions of years,
the matter and radiation are almost completely dissipated and
the expansion stalls. An energy field that pervades the universe
then creates new matter and radiation, which restarts the cycle.

The new theory provides possible answers to several longstand-
ing problems with the big bang model, which has dominated the
field of cosmology for decades. It addresses, for example, the
nagging question of what might have triggered or come "before"
the beginning of time.

The idea also reproduces all the successful explanations pro-
vided by standard picture, but there is no direct evidence to say
which is correct, said Steinhardt, a professor of physics. "I do
not eliminate either of them at this stage," he said. "To me, what's
interesting is that we now have a second possibility that is poles
apart from the standard picture in many respects, and we may
have the capability to distinguish them experimentally during the
coming years."

... The new model replaces inflation and dark energy with a single
energy field that oscillates in such a way as to sometimes cause
expansion and sometimes cause stagnation. At the same time, it
continues to explain all the currently observed phenomena of the
cosmos in the same detail as the big bang theory.

Because the new theory requires fewer components, and builds
them in from the start, it is more "economical," said Steinhardt,
who was one of the leaders in establishing the theory of inflation.

Another advantage of the new theory is that it automatically in-
cludes a prediction of the future course of the universe, because
it goes through definite repeating cycles lasting perhaps trillions
of years each. The big bang/inflation model has no built-in predic-
tion about the long-term future.

... The cyclic model entails many new concepts that Turok and
Steinhardt developed over the last few years with Justin Khoury,
a graduate student at Princeton, Burt Ovrut of the University of
Pennsylvania and Nathan Seiberg of the Institute for Advanced
Study.

... Sir Martin Rees, Royal Society Research Fellow at Cambridge,
noted that the physics concerning key properties of the expanding
universe remain "conjectural, and still not rooted in experiment or
observation."

"There have been many ideas over the last 20 years," said Rees.
"Steinhardt and Turok have injected an imaginative new specula-
tion. Their work emphasizes the extent to which we may need to
jettison common sense concepts, and transcend normal ideas of
space and time, in order to make real progress.

"This work adds to the growing body of speculative research
which intimates that physical reality could encompass far more
than just the aftermath of 'our' big bang."

The cyclic universe theory represents a combination of standard
physical concepts and ideas from the emerging fields of string
theory and M-theory, which are ambitious efforts to develop a
unified theory of all physical forces and particles. Although these
theories are rooted in complex mathematics, they offer a compel-
ling graphic picture of the cyclic universe theory. ...

(end excerpts)

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Excerpts from "A Recycled Universe" (JR Minkel and
George Musser, February 11, 2002) ...
http://www.sciam.com/article.cfm?articleID=000C55B5-C29B-
1CDA-B4A8809EC588EEDF

... A universal cycle of birth and rebirth occurs every trillion
years or so, according to one new cosmology.

---
Original ekpyrotic model:
http://pauli.physics.lsa.umich.edu/w/arch/som/sto2001/
Steinhardt/real/sld018.htm

---

... The big bang clearly marks some kind of first. That fearsome
flash of energy and expansion of space set in motion everything
our eyes and telescopes can see today. But on its own, the big
bang theory would leave us in a curved universe where matter
and energy aren't well mixed. In fact, we now know that space-
time is flat and that galaxies and radiation are evenly distributed
throughout.

To shore up the big bang theory, cosmologists proposed that
the universe began with a burst of exponential expansion from
a single uniform patch of space, whose stamp remains on the
cosmos to this day. Such inflationary cosmologies have worked
so well they've crowded out all the competition.

During this past year, however, one group of researchers has
started to challenge that idea's preeminence, though the field
of cosmology has yet to be completely taken with the new
approach. Drawing on some cutting-edge but unproved notions
in particle physics, the challengers interpret the big bang as a
violent clash between higher-dimensional objects.

In the latest installment to the saga, the authors of this interpreta-
tion have found a way to turn that single clash into a never-ending
struggle that rears its fiery head every trillion years or so, making
our universe just one phase in an infinite cycle of birth and rebirth.

... String theory has spawned more than one attempt to do away
with the big bang singularity. ... strings could also exist in a more
fundamental, 11-dimensional theory.

---
More on string theory:
http://sukidog.com/jpierre/strings/
---

They collapsed one of these dimensions mathematically into a
minuscule line, yielding an 11-dimensional spacetime, flanked
on either side by two 10-dimensional membranes, or branes,
colorfully dubbed "end of the world" branes.

One brane would have physical laws like our own universe.
From there, ... six of those 10 dimensions could be made
extremely small, effectively hiding them from everyday view
and leaving the traditional four dimensions of space and time.

... By turning back the clock in string theory, they found that as
our universal brane passed through its starting singularity in re-
verse, it went suddenly from a state of intense but finite heat
and density to one that was cold, flat and mostly empty.

In the process, it shed another kind of brane into the 11-dimen-
sional gap. Run forward in time, the big bang appeared as noth-
ing more than two branes smacking into each other like cymbals.
They christened this process the ekpyrotic model, after the an-
cient Greek "conflagration" cosmology wherein the universe is
born in and evolves from a fiery explosion.

... the singularity could be interpreted as a collision between the
two "end of the world" branes, in which only the gap dimension
separating them shrinks down to zero for an instant.

... The pre-bang universe had to be dark, flat and infinite, seem-
ingly by fiat. But why should it have begun in such a state? The
answer, according to the latest work from Steinhardt and Turok,
has to do with dark energy, the force that is driving the galaxies
apart at ever-increasing speeds.

Drained Branes - As the universe accelerates, it will become
harder for light to travel between distant corners of space. Over
time, galaxies will become isolated from their neighbors; stars
will wink out; black holes will evaporate quantum mechanically
into radiation; even that radiation will be diluted in a sea of space.
The universe could end up much as the ekpyrotic model suggests
it should appear before the big bang.

... the dark energy, combined with the milder singularity of the
ekpyrotic model, provides a tidy way of setting up a cyclic uni-
verse.

Our brane and its counterpart would bounce off each other as
usual, but instead of going their separate ways, they would smack
each other again and again as if connected by a spring. This at-
tractive force between branes would in fact be a special case
of the kind of force that inflationary cosmologies posit to ex-
plain the early universe's blowup. The branes' oscillating motion
would work to pump space into our universe like a bellows,
explaining the acceleration that we see today.

... "I think it's surprising how well this model works in terms of
reproducing everything we see and yet being so different,"
Steinhardt remarks. "That's quite shocking and, I think, impor-
tant, because we thought we were converging toward something
that was a unique cosmic story."

... "I happen to think the cyclic model is a real intriguing one,"
Steinhardt says. "It has a lot of new ingredients that people
haven't had a chance to play with. When they play they might
find other interesting things that we missed." Or not. ...

(end excerpts)

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Posts in this series:

Universe(s) Origin(s) Preface
http://prohuman.net/universes_origins_preface.htm

Universe(s) Origin(s) - 1 of 7
}}} String Theory / Infinities / Singularities {{{
http://prohuman.net/universes_origins_1_of_7.htm

Universe(s) Origin(s) - 2 of 7
}}} No Origin of the Universe? {{{
http://prohuman.net/universes_origins_2_of_7.htm

Universe(s) Origin(s) - 3 of 7
}}} Multiverse? {{{
http://prohuman.net/universes_origins_3_of_7.htm

Universe(s) Origin(s) - 4 of 7
}}} Universes from Black Holes? {{{
http://prohuman.net/universes_origins_4_of_7.htm

Universe(s) Origin(s) - 5 of 7
}}} Cyclic Universe? {{{
http://prohuman.net/universes_origins_5_of_7.htm

Universe(s) Origin(s) - 6 of 7
}}} Einstein / Big Bang / Superstrings {{{
http://prohuman.net/universes_origins_6_of_7.htm

Universe(s) Origin(s) - 7 of 7
}}} Nothing / Everything {{{

http://prohuman.net/universes_origins_7_of_7.htm

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