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Isambard
09-16-2007, 06:01 PM
http://www.space.com/scienceastronom..._big_bang.html

What do you get when you turn the temperature up to a trillion degrees?

Quite a heating bill.

Actually physicists claim that at this temperature nuclear material melts into an exotic form of matter called a quark-gluon plasma - thought to have been the state of the universe a microsecond after the Big Bang.

Recreating this primordial soup is the primary purpose of the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory. After five years of data, it appears as if RHIC may have succeeded.

But a big mystery looms over the detection: the putative plasma explodes more violently than predicted.

"We expected to bring the nuclear liquid to a boil and produce a steam of quark-gluon plasma," said John Cramer from the University of Washington. "Instead, the boiler seems to be blowing up in our faces."

The explosive result, which goes by the name of the HBT puzzle, may call into question what RHIC is making in its high-speed collisions, or it might mean the theory needs retuning.

Cramer and his colleagues have another alternative explanation, too: perhaps the explosion is not as explosive as the data suggests. The scientists use 50-year old physics to reinterpret the measurements at RHIC.

"We have taken a quantum mechanics technique, called the nuclear optical model, from an old and dusty shelf and applied it to puzzling new physics results," said Gerald Miller, a coauthor also at the University of Washington. "It's really a scientific detective story."

Collecting clues

The main suspect in this detective story is the quark-gluon plasma. But how do you know when you've seen it? The plasma cannot be observed directly - it disappears in less than a hundredth of a billionth of a trillionth of a second. All that researchers can hope to do is detect the particles that fly out when the plasma freezes back into normal matter.

"You can't go in there and directly measure the quarks and gluons," Miller told SPACE.com. "You have to work back from what you measure to what you believe was there."

Scott Platt from Michigan State University, who didn't participate in the new research, compares detecting the quark-gluon plasma to what astronomers have to do when studying an exploding star.

"They only see the light coming from the star's surface and then try to infer what happened inside. We [physicists] have the same problem," he said.

Instead of light, RHIC researchers see thousands of particles - mostly pions, which are tiny things weighing about one-seventh as much as a proton, itself subatomic. The pions show up in detectors set up around collision points, where gold nuclei traveling at 99.995 percent of the speed of light hit each other head-on.

To see a movie of a gold-on-gold collision click here (note that the gold nuclei look like pancakes because they are traveling so fast).

"We can't stick a barometer or thermometer into the collision center," Platt explained, but by a careful reconstruction of the flight paths of all the debris coming out, scientists can extract information about the brief, but intense, furnace created when gold nuclei smash into each other.

From the RHIC data, research teams have identified three smoking guns for the quark-gluon plasma:

the collision center is under high pressure
the collision center behaves a lot like a fluid
very high energy particles do not escape
Although this evidence appears solid, physicists are hesitant to say they have created the melted nuclear goop. "That debate is going on as we speak," Platt said.

One of the reasons for this conservative approach has to do with how fast the supposed plasma appears to freeze back into ordinary matter. Theory assumed this phase transition would take almost twice as long as was measured.

"In science, if you have a bunch of things that are right, it won't matter if one thing goes wrong," Miller said.

The apparent explosion of pions and other particles coming from the phase transition is the so-called HBT puzzle.

"It is the one RHIC observation that deserves the word puzzle or surprise," Platt said.

HBT puzzle

To measure the duration of the plasma's phase transition, physicists use an astronomy tool, called Hanbury Brown-Twiss (HBT) interferometry, which can find the diameter of stars using the radio signals from two separate telescopes.

Tiny Terms

Quark: subatomic particle that is the building block of protons, neutrons and short-lived particles like pions.

Gluon: a particle that transmits the strong nuclear force - literally gluing quarks together into protons and neutrons and such.

Plasma: a separate form of matter - often referring to a gas of freed electrons and ions. In the case of the quark-gluon plasma, the quarks and gluons are liberated from their usual bonds, and can interact with one another freely.

Pion: Unlike protons and neutrons, which are made of three quarks, the pion is made of just two quarks. Pions eventually decay into photons, electrons and neutrinos.

Phase transition: A change between two forms of matter, like when water freezes or boils. There is a phase transition between the quark-gluon plasma and ordinary matter.

Michael Schirber, SPACE.com




Instead of comparing radio waves, physicists compare two pions flying out from the collision center. But these measurements require a lot of modeling and approximations, Platt explained.

Cramer and Miller and their collaborators have redone the calculations, incorporating something called the nuclear optical model. This dates back to 1950's, when scientists were beginning to understand the strong interactions inside the nucleus.

Effectively, this old-school physics accounts for the fact that, as pions form out of the cooling plasma, they will have to climb their way out of an attractive field - similar to the gravitational field that a rocket has to overcome to escape a planet's clutches.

"This is not surprising, since it has already been shown that the medium is very dense," Miller said. "It is as if the pions are trying to leave a crowded room."

According to Cramer, this crowded room "distorts" the data, making the transition look more explosive than it really is. In a sense, the HBT puzzle could be a simple misinterpretation of what the data shows.

Platt is unsure that Cramer and Miller's work, published this month in Physical Review Letters, indeed clears up the HBT puzzle entirely.

"They pointed out one of the ways that the calculations can be improved," he said. "But the analysis is ongoing."

If the puzzle does end up being solved, will physicists be ready to claim victory?

"It is not for me to say that we have found the quark-gluon plasma," Cramer said. "But we have made an important step."

This article is part of SPACE.com's weekly Mystery Monday series.
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Woodrow
09-16-2007, 08:01 PM
Interesting.

Actually physicists claim that at this temperature nuclear material melts into an exotic form of matter called a quark-gluon plasma - thought to have been the state of the universe a microsecond after the Big Bang.
I wonder if anybody stopped to think that to heat something to a trillion degrees, you have to have something(Matter) to heat. in other words matter would have to exist for this to occur. It does not "Create" matter.
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Isambard
09-17-2007, 03:13 AM
Originally Posted by Woodrow
Interesting.



I wonder if anybody stopped to think that to heat something to a trillion degrees, you have to have something(Matter) to heat. in other words matter would have to exist for this to occur. It does not "Create" matter.
Seeing how matter cannot be destroyed, is it really a surprise it cant be created either? :D

I think the findings of the article or proof of a eternal cyclical universe:shade:
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Woodrow
09-17-2007, 03:29 AM
Originally Posted by Isambard
Seeing how matter cannot be destroyed, is it really a surprise it cant be created either? :D

I think the findings of the article or proof of a eternal cyclical universe:shade:
I used to be a strong believer in the concept of an eternal cyclical universe. However, my old physics classes seemed to point out that the concept of matter can not be destroyed, is flawed and matter actually is decaying and will at some point cease to exist.

An interesting read here:

Teilchenphysik ohne Beschleuniger
(Non Accelerator Particle Physics)
Arbeitsgruppe (Group of)

Prof. Dr. rer. nat. habil. H.V. Klapdor-Kleingrothaus

Experimental and theoretical research in the areas of
Double Beta Decay, Dark Matter Searches and Physics beyond the Standard Model


H.V. Klapdor-Kleingrothaus and I.V. Krivosheina,
"The Evidence for the Observation of 0nu beta-beta decay:
the Identification of 0nu beta-beta Events
from the Full Spectra"

NN, det-s 2,3,4,5, from 1995 to 2003. 6.4 sigma (7.05 +- 1.11 events).
"The pulse shape selected spectrum (selected by neuronal net-NN) with detectors 2,3,4,5, from 1995 to 2003 in the energy interval 2000-2100 keV. The signal at Qbeta-beta has a confidence level of 6.4 sigma (7.05 +- 1.11 events)."
NN- 0 mm, det-s 2,3,4,5, from 1995 to 2003. 6.6 sigma. NN- 1 mm, det-s 2,3,4,5, from 1995 to 2003. 7.2 sigma. NN- 2 mm, det-s 2,3,4,5, from 1995 to 2003. 6.7 sigma.
"The pulse shape selected spectrum (selected by neuronal net-NN) with detectors 2,3,4,5, from 1995 to 2003 in the energy interval 2000-2060 keV. The signal at Qbeta-beta has a confidence level of 6.6, 7.2 and 6.7 sigma respectively for cutting boundary areas of 0(1)(2) mm are shown."
NN- 2505 kev Gam L., det-s 2,3,4,5, from 1995 to 2003. MSE- 2505 kev Gam L., det-s 2,3,4,5, from 1995 to 2003. NN- 2105 kev Gam L., det-s 2,3,4,5, from 1995 to 2003.
"Lines from the neuronal net (NN) pulse shape selected spectrum measured 1995-2003 for detectors 2,3,4,5, in the energy of some background lines. E.g. the 2505.7 keV line originating from summation of the subsequent 1173.2 and 1332.5 keV gamma-lines from 60Co naturally expected to consist of multiple site events is erased to 100% (please compare with pulse shape selected MSE spectrum, second figure (rosa))."
Source: http://www.mpi-hd.mpg.de/non_acc/
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noodles
09-17-2007, 03:29 AM
Originally Posted by Isambard
Seeing how matter cannot be destroyed, is it really a surprise it cant be created either? :D

I think the findings of the article or proof of a eternal cyclical universe:shade:
Didn't we discuss this exact same point in the 'Atheist Ideology' thread?
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Isambard
09-17-2007, 05:23 PM
Originally Posted by Woodrow
I used to be a strong believer in the concept of an eternal cyclical universe. However, my old physics classes seemed to point out that the concept of matter can not be destroyed, is flawed and matter actually is decaying and will at some point cease to exist.

An interesting read here:



Source: http://www.mpi-hd.mpg.de/non_acc/
Pfft

Way to spoil the ending Woodrow:p

Well, the occilating Universe model may be out (thou Ive heard some interesting new research has been found. If I wasnt so ignorant on the matter Id post some evidence)

But at the very least, the findings of the scientists do seem to indicate that some sort of previous universe's destruction was the cause for our own forming which raises a bunch of questions.

And hey, this could also mean God does exist in some way, albeit he would be the physical equivalant of Galactus lol:D
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Fishman
09-17-2007, 05:28 PM
:sl:
The title is a bit misleading, there was no new universe created, just big bang temperatures.
:w:
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Md Mashud
09-17-2007, 06:14 PM
Occilating theory was out last year - It was dealt a huge blow when Stephen Hawkin discredited idea of mulitverse or continuous Universe.
Reply

root
09-18-2007, 05:09 PM
Originally Posted by Md Mashud
Occilating theory was out last year - It was dealt a huge blow when Stephen Hawkin discredited idea of mulitverse or continuous Universe.
Occilation, Big-Crunch, Big-Bang and now the "sling shot universe"............

I AM a heretic,” Cristiano Germani announced to an audience of osmologists last month. Few would disagree, as he is proposing a
radical alternative to standard cosmology: a universe with no big bang
creation moment, and no rapid inflation. Rather than a big bang, he
suggests a slingshot.

In the early 1980s, Alan Guth at the Massachusetts Institute of
Technology proposed that our universe underwent inflation - a period
of rapid expansion in the first 10-34 seconds after the big bang.
Germani, a cosmologist at the International School of Advanced Studies
in Trieste, Italy, says that inflation is beautiful and successful,
yet he insists that we need to replace it.

“We don’t have any fundamental physical explanation for how or why it
occurred,” he says. “Yet cosmologists today accept it as though it is
a religion.”

Germani’s alternative, unveiled at a cosmology conference at the
University of Sussex, UK, last month, is based on a string-theory
model in which the three visible dimensions of space are confined to
the surface of a membrane, or brane, floating in a 10-dimensional
space. The extra dimensions are wrapped up into a complex shape known
as a Calabi-Yau space (see Illustration). The forces and particles in
our 3D world are shadows of the motion of branes and strings in the
Calabi-Yau space.

The problem with the simplest versions of this model is that the
Calabi-Yau space is unstable, constantly vibrating and changing size.
Each wobble of the surface creates unwanted particles and extra forces
in the universe - none of which have ever been observed. Attempts by
string theorists to stabilise the space always warp it, forcing
strange spikes and throats to pop out, Germani says. This warping, he
believes, is the key to explaining the evolution of our universe.

Germani and his colleagues examined what would happen if a brane
containing our universe fell down one of these throats. At first
things looked bleak: the universe dropped like a stone, getting
squeezed until it was crushed at the tip of the throat, corresponding
to a big crunch in which the universe collapses in on itself.

But then Germani considered a spinning universe. “In fact, it is much
more realistic that the universe will be rotating as it drops,” he
says. Something more interesting happens to a rotating universe as it
hurtles down the throat. Because it is spinning, it avoids falling
into the tip of the throat and whirls round it instead. Like a
boomerang or a stone from a slingshot, it then flies back up again.
Germani realised that the second leg of this journey could correspond
to the expanding universe we observe today.

Other cosmologists have suggested that our universe went through a
superficially similar cycle of big bangs and big crunches. Germani’s
slingshot mechanism is different from these because it never sends the
universe through a big bang singularity. As a result, the model can
solve the so-called “horizon problem” without resorting to inflation.

The horizon problem runs like this. No matter where you look in the
universe, the background temperature is about the same, but not enough
time has elapsed since the big bang for radiation to travel across the
universe and back, exchanging temperature information. Inflation
solves this problem because regions of space which sit on opposite
sides of the visible universe today could once have been close
together, and been blown far apart during inflation.

With the slingshot picture, there is no big bang and so no horizon
problem. “We have no beginning of time, so the universe is easily old
enough for regions on both sides of the sky to have been in contact in
the past,” Germani says. “In the slingshot scenario we could have an
ever-existing universe.” His team’s calculations also show that the
apparently finely tuned density of today’s universe arises naturally
using the slingshot, though inflation is also able to account for
this.

Last year, support for inflation was bolstered by measurements of the
pattern of cold and hot spots in the cosmic microwave background (CMB)
made by the Wilkinson Microwave Anisotropy Probe, which seem to fit
perfectly with the predictions of inflation. When Germani calculated
how temperature imprints would develop in his slingshot universe, he
found that they also matched the data. Germani and his colleagues are
now working out what signatures in the CMB could distinguish it from
inflation, in the hope that they might turn up when the European Space
Agency’s Planck satellite begins more detailed measurements in 2008.

Cosmologist Paul Frampton at the University of North Carolina, Chapel
Hill, likes the idea. “They have solved the key problems that
inflation solves and have good agreement with the latest
observations,” he says.

String theorist Damien Easson at the University of Durham, UK, agrees
that inflation needs an explanation based on fundamental physics.
However, he does not see the cosmological slingshot model as the
answer. “It’s extremely controversial to claim to have found an
alternative to one of the most respected theories in cosmology,” he
says.

Easson points out that string-theory models usually represent the
universe as a stack of branes in the non-warped region of the Calabi-
Yau space, and have successfully used this to explain why we see the
forces and particles that we do. “It’s difficult to see how this can
be achieved if our universe is flying down the throat,” he says.

Germani accepts that his model still needs work, but he believes that
he will eventually meet this challenge. “Remember, inflation theory
has been around for more than 20 years, while my theory is still
young,” he says.
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