Re: Is the universe computable?

From: CMR <jackogreen.domain.name.hidden>
Date: Thu, 8 Jan 2004 07:15:05 -0800

Possibly relevant to this thread:

NYTimes:
January 8, 2004

New-Found Old Galaxies Upsetting Astronomers' Long-Held Theories on the Big
Bang
By KENNETH CHANG

ATLANTA, Jan. 7 — Gazing deep into space and far into the past, astronomers
have found that the early universe, a couple of billion years after the Big
Bang, looks remarkably like the present-day universe.
Astronomers said here on Monday at a meeting of the American Astronomical
Society that they had found huge elliptical galaxies that formed within one
billion to two billion years after the Big Bang, perhaps a couple of billion
years earlier than expected.

A few days earlier, researchers had announced that the Hubble Space
Telescope had spotted a gathering cloud of perhaps 100 galaxies from the
same epoch, an early appearance of such galactic clusters.
On Wednesday, astronomers at the meeting said that three billion years after
the Big Bang, one of the largest structures in the universe, a string of
galaxies 300 million light-years long and 50 million light-years wide, had
already formed. A light-year is the distance that light travels in one year,
or almost six trillion miles.
That means the string is nearly 2,000 billion billion miles long.

Some astronomers said the discoveries could challenge a widely accepted
picture of the evolution of the universe, that galaxies, clusters and the
galactic strings formed in a bottom-up fashion, that the universe's small
objects formed first and then clumped together into larger structures over
time.

"The universe is growing up a little faster than we had thought," said Dr.
Povilas Palunas of the University of Texas, one of the astronomers who found
the string of galaxies. "We're seeing a much larger structure than any of
the models predict. So that's surprising."

In the prevailing understanding of the universe, astronomers believe that
slight clumpiness in the distribution of dark matter, the 90 percent of
matter that pervades the universe but still has not been identified, drew in
clumps of hydrogen gas that then collapsed into stars and galaxies, the
first stars forming about a half billion years after the Big Bang. The
galaxies then gathered in clusters, and the clusters gathered in long
strings with humongous, almost empty, voids in between. The first such
string, named the Great Wall, was discovered in 1989 about 250 million
light-years away.

The newly discovered string lies in a southern constellation, Grus, at 10.8
billion light-years away, and represents what the universe looked like 10.8
billion years ago, or three billion years after the Big Bang.
The international team of researchers identified 37 very bright galaxies in
that region of space and found that they were not randomly distributed, as
would be expected, but instead appeared to line up along the string.
Such structures are rarely seen in computer simulations of the early
universe, said Dr. Bruce E. Woodgate of the NASA Goddard Space Flight
Center, a member of the team.

"We think it disagrees with the theoretical predictions in that we see
filaments and voids larger than predicted," Dr. Woodgate said.

Dr. Robert P. Kirshner of the Harvard-Smithsonian Center for Astrophysics
said the findings were interesting, but that it was too early to eliminate
any theories. What is probably needed was a better understanding how of a
clump of dark matter leads to the formation of stars.

"What we're seeing here," Dr. Kirshner said, "is the beginning of the
investigation how structure grows."
At the astronomy meeting on Monday, another team of researchers reported
finding a large number of large elliptical galaxies. As part of an
investigation known as the Gemini Deep Deep Survey, the astronomers explored
300 faint galaxies dating from when the universe was three billion and six
billion years old. The large elliptical galaxies are supposedly a merged
product of smaller spiral galaxies.

Yet not only did they exist that early in the universe, but the stars within
these galaxies also appeared a couple of billion years old already, implying
that they had formed as early as a billion and a half years after the Big
Bang.
"Massive galaxies seem to be forming surprisingly early after the Big Bang,"
said Dr. Roberto Abraham of the University of Toronto and a co-principal
investigator on the team. "It is supposed to take time. It seems to be
happening right away."

The data actually fit better with the views that astronomers held before the
rise of the current dark-matter models, when they theorized that the largest
galaxies formed first.

"If we presented this to astronomers 25 years ago," Dr. Abraham said, "they
wouldn't have been surprised."
A third team of astronomers found two clusters of galaxies that also point
to a precocious universe. Using the Hubble telescope, the astronomers
spotted a cluster of at least 30 galaxies dating from when the universe was
younger than two billion years old and extending three million light-years
across.

"Which is similar in size to what we see today for the size of a cluster,"
said Dr. Marc Postman, an astronomer at the Space Telescope Science
Institute in Baltimore and a member of the team.
Present-day clusters contain hundreds to thousands of galaxies.

The same team found a second cluster, from when the universe was five
billion years old that was almost indistinguishable from modern clusters.

"It says these structures, which are common in the universe today, were
essentially being constructed very early on," Dr. Postman said.

The galactic cluster findings were reported in Oct. 20 issue of The
Astrophysical Journal and the Jan. 1 issue of Nature.

For now, the findings do not directly contradict the models that predict
that some structures should form, but rarely. But if many more start showing
up in observations, Dr. Postman said, "then you might get into a bit of a
problem explain how you get so many."
Received on Thu Jan 08 2004 - 10:18:42 PST