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Sound familiar?

Apr 27, 2002 08:14 AM
by alwilli

Taken from:

Since they talk Leon's talk, perhaps Leon would like to put this in context
for us...?

No beginning, no end to universe, pair suggest
By Edie Lau -- Bee Science Writer
Published 2:15 a.m. PDT Friday, April 26, 2002

If the universe was created by a big bang, which is the prevailing view of
science, what happened before that? And how will it all end?

These nagging questions are not addressed by the big-bang theory, but now
there's a model of the universe that offers an answer. It goes like this:
The universe expands and pauses, expands and pauses endlessly, so that time
neither begins nor ends.

"It gets rid of the problem of explaining a creation. ... The universe has
been around forever," said Paul Steinhardt, a Princeton University
astrophysicist, who, with Neil Turok at Cambridge University, proposes a
cyclic universe model in a paper published online today by the journal

Using exotic concepts in modern physics, the ambitious model liberally
rearranges certain ideas in big-bang theory. One implication is that the
bang wasn't all that big. The cyclic model says, for example, that galaxies
formed out of forces that existed before the bang.

For a culture such as ours, which marks history by linear time -- past,
present and future -- the idea of timeless time is mind-bending.

But as Steinhardt noted, other cultures, notably the ancient Hindus, saw the
universe as cyclic.

Western astrophysicists in the 1930s put forth similar "oscillatory" models
of the universe. The model described today recycles some old ideas and
incorporates new concepts, including the notion of the universe having extra

"I think it will make a splash," said Daniel Cebra, an experimental
physicist at the University of California, Davis, involved in a project
reconstructing the first moments after the presumed big bang. "Steinhardt is
a big name in this field, so what he says people listen to pretty

Andreas Albrecht, a UC Davis cosmologist, said the idea needs more
development to be persuasive, but called it "very stimulating and fun."

Stimulating more thinking on the fundamental form of the universe was the
reason Steinhardt began scouting for a new model.

In earlier years, Steinhardt -- along with Albrecht and others -- developed
a piece of the standard model of the universe known as inflation. Inflation
theory says that a period of extremely fast expansion followed the cosmic
boom that gave rise to the universe. Inflation then gave way to more sedate
growth, the era we're thought to be in today.

"One way of exploring my confidence in the (inflation) model is (seeing)
whether or not we can come up with something else," Steinhardt said. "We
decided to see ... just how far we could get. I'm as surprised as anyone
just how far we have gone."

Described very simply, the cyclic model works this way:

The big bang is not the start of time, but rather, a bridge to an earlier
era of contraction. Coming after the bang is the usual formation of matter
and radiation. The slow expansion lasts trillions of years.

Eventually, the matter and radiation are so diluted that the universe
becomes virtually empty. The expansion ends.

During this period of stagnant growth, the dynamics of the universe change,
such that energy rebuilds to fuel another bang.

What is the change? This is where even Steinhardt agrees that the model gets
quite strange.

Borrowing from a branch of physics known as string theory, the cosmologists
propose that the universe as we know it is really a surface in a
higher-dimensional space.

In Steinhardt's words: "We're stuck like flies on fly paper to move only in
our own dimension."

In his cyclic model, there is a second surface, like the second piece of
bread in a sandwich, that we can't touch, feel or see. The surfaces are
called membranes, or 'branes' for short.

The branes can move in two ways: They can stretch, remaining a fixed
distance apart; and they can smash together and come apart again. They
cannot be smashed together at the same time they're being stretched.

Matter and radiation cause branes to stretch. When they have stretched so
far that the universe is emptied of its matter and radiation, the branes
smash together. The collision of surfaces creates more matter and radiation.
The cycle begins anew.

By Albrecht's analysis, the collision is a weak point in the model. "The
(mathematical) equations they're using don't include any detail about the
inside of the branes, so to speak," he said. "So they just have to make a
wish basically, and say, I hope that when they collide, it comes out in this
particular way."

Such concerns may be best left for scientists to hash out, but the general
ideas are worth the attention of everyone, said Craig Hogan, an
astrophysicist at the University of Washington.

"It's not just talking about the first moments of the universe, but how
physics is put together at the most basic level," Hogan said. "What makes it
work? That sort of question has very immediate implications."

When Einstein published his theories of space, time and gravity nearly 100
years ago, the ideas were considered useless for everyday life, Hogan said.
Today, they're anything but.

A case in point: An understanding of how light travels through space, and of
the relationship between space and time, underlies the Global Positioning
System, the satellite navigation tool used for everything from aiming bombs
to hiking, golfing, and driving around an unfamiliar city.


Best regards,

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