| A.Melon 2005-04-25, 10:51 pm |
| Hey Thomas, I just picked this off the BBC news.
Early Universe was 'liquid-like'
Physicists say they have created a new state of hot, dense matter by crashing
together the nuclei of gold atoms.
The high-energy collisions prised open the nuclei to reveal their most basic
particles, known as quarks and gluons.
The researchers, at the US Brookhaven National Laboratory, say these particles
were seen to behave as an almost perfect "liquid".
The work is expected to help scientists explain the conditions that existed
just milliseconds after the Big Bang.
The details, presented to the American Physical Society in Florida, will be
published across a number of papers in the journal Nuclear Physics A.
They summarise the work of four collaborative experiments - dubbed Brahms,
Phenix, Phobos and Star - which have been running on Brookhaven's Relativistic
Heavy Ion Collider (RHIC).
Already, the results have caused quite a stir in the research community.
"The experimental collaborations are still taking a cautious approach whereas
people like me, who use model calculations, are already so excited about the
data because we believe they have actually found the elusive state known as the
quark-gluon plasma," commented theoretical nuclear physicist Steffen Bass from
Duke University.
The QGP is the state postulated to be present just a few millionths of a second
after the creation of the Universe - before the formation of matter as we know
it today.
To create the ultra-hot, ultra-dense conditions seen in Brookhaven's RHIC, gold
ions were fired at each other at near-light speeds.
Although these impacts only occur in tiny volumes, they deliver sufficient
energy to "melt" the neutrons and protons that make up the nuclei, and allow
their even smaller constituent quarks and gluons to roam free for a few,
fleeting moments.
Cern, Europe's leading nuclear research lab, is thought to have had glimpses of
this remarkable state back in 2000, but the Brookhaven work is said to have
gone to another level.
Surprising data
However, the RHIC scientists are reluctant to make a firm declaration that a
QGP has been achieved.
"We know that we've reached the temperature [up to 150,000 times hotter than
the centre of the Sun] and energy density [energy per unit volume] predicted to
be necessary for forming such a plasma," said Sam Aronson, Brookhaven's
associate laboratory director for high energy and nuclear physics, but added
also that aspects of the data had surprised everyone.
In a sense we are working backwards to the Big Bang by going to higher energy
collisions, in order to be able to see this stuff
Prof Ken Peach, Rutherford Appleton Laboratory
There were unexpected patterns in the trajectories taken by the thousands of
particles produced in the individual collisions.
These suggest that the matter revealed at the heart of those collisions was
behaving not like the perfect "gas" of free quarks and gluons predicted for the
GDP, but more like a liquid.
"The matter in the RHIC behaves very much like an ideal fluid; like a liquid,"
said Bass, who also holds an affiliation at Brookhaven.
"And a liquid is, of course, very deferent from a gas - it is very strongly
interacting. Whereas what people like myself had assumed for many, many years
was that a quark-gluon plasma would more behave like a dilute gas, where the
particles would roam freely between scatterings for quite a distance."
Working back
The RHIC teams themselves intend to run more experiments and hope to make a
more definitive statement about the nature of what they have seen in due course.
Already, some commentators are saying the data appears to match some aspects of
string theory, an approach that attempts to explain the fundamental properties
of the Universe using *10* *dimensions* instead of the usual *three* *spatial*
*dimensions* plus time.
The international scientific community has put in place a programme of
development over the next few decades which will see new machines come on
stream that can probe matter states in new regions and at higher energies.
These experiments should put greater detail on our understanding of the
materials and forces that built the Universe.
"In a sense we are working backwards to the Big Bang by going to higher energy
collisions, in order to be able to see this stuff," said Ken Peach, the head of
particle physics at the CCLRC Rutherford Appleton Laboratory in the UK.
"We can't get all the way back to 't = 0' but we can get back to some place
that was near there and then look to see how this 'droplet' of primordial Big
Bang material develops.
"And the assumption is that provided you can create a large enough droplet, it
will evolve in the same way as the early Universe."
And Thomas, I "asterixed" the parts I once spoke off, but I don't care what the
scientists say, there has to be 13 dimensions for things to fit nicely
together, not 10, but then I hardly expect you to understand why, and neither
can I be bothered to explain it, and they already found the source of energy at
the centre of the universe last week, but hey, you are the google-boi, find the
news story yourself.
Alan
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