* Astronomy

Members Login
Post Info TOPIC: Big Bang


L

Posts: 131433
Date:
Helium 3 discrepancy
Permalink  
 


Using 3D models run on some of the fastest computers in the world, Laboratory physicists have created a mathematical code that cracks a mystery surrounding stellar evolution.
For years, physicists have theorised that low-mass stars (about one to two times the size of our sun) produce great amounts of helium 3 (³He). When they exhaust the hydrogen in their cores to become red giants, most of their makeup is ejected, substantially enriching the universe in this light isotope of helium.
This enrichment conflicts with the Big Bang predictions. Scientists theorized that stars destroy this ³He by assuming that nearly all stars were rapidly rotating, but even this failed to bring the evolution results into agreement with the Big Bang.
Now, by modelling a red giant with a fully 3D hydrodynamic code, LLNL researchers identified the mechanism of how and where low-mass stars destroy the ³He that they produce during evolution.
They found that ³He burning in a region just outside of the helium core, previously thought to be stable, creates conditions that drive this newly discovered mixing mechanism.

Read more

__________________


L

Posts: 131433
Date:
RE: Big Bang
Permalink  
 


An apparent discrepancy in the Big Bang theory of the universe's evolution has been reconciled by astrophysicists examining the movement of gases in stars.
Professor John Lattanzio from Monash's School of Mathematical Sciences and Director of the Centre for Stellar and Planetary Astrophysics said the confusion surrounding the Big Bang revolved around the amount of the gas Helium 3 in the universe.

"The Big Bang theory predicts a certain amount of Helium 3 in the universe. The trouble is, low mass stars (about one to two times the size of our sun) also make Helium 3 as a side product of burning the hydrogen in their cores. It's been thought that when the star becomes a giant it mixes the helium 3 to its surface and, near the end of its life, spews the helium 3 into space just before it becomes a planetary nebula. But there are inconsistencies with the amount of Helium 3 predicted to be in the universe and the amount that's actually there; there's much less than expected" - Professor Lattanzio.

Read more

__________________


L

Posts: 131433
Date:
Permalink  
 

Most cosmologists discarded the big crunch theories in favour of forever expanding (or currently accelerating) type versions.
Evidence such as observations of type Ia supernovae etc, seems to point towards an accelerating space-time.
When the universe does become a wasteland of nothingness, then according to Professor Roger Penrose the few particles (if we assume they remain) will have no other particles to `interact with` (the other particles are beyond the observable universes horizon) and time` becomes meaningless` - this may be the conditions to `reset` the universe to a state similar to before the big bang.

Watch Sir Roger Penrose talk about before the big bang. (realplayer stream)

__________________


L

Posts: 131433
Date:
Permalink  
 

If current computer simulations are anything to go by, the Big Bang is wrong, according to cosmologists. But the experts aren't throwing away the theory just yet, they're blaming the computers.

According to a report published in U.S. journal Science on Friday, current simulations, which theoretically map the formation of the universe from when the Big Bang 'unfolded' over 13 billion years ago, are inconsistent with actual observations of nearby galaxies.
Cosmologists might have to wait decades before computer simulations can substantiate their theories, as current computers are simply not powerful enough to yield useful data.
For example, the authors, Joss Bland-Hawthorn, of the Anglo-Australian Observatory and Big Bang theory pioneer, P. J. E. Peebles of Princeton University, USA said in their report simulations suggest "our Local Group is expected to have a thousand small mass concentrations but we infer the presence of fewer than 50 from the number of visible galaxies".

Such discrepancies are likely due to the limits of modern computers, rather than any particular flaw in the predictions of Big Bang inflationary cosmology.
Gas dynamics that determine how matter settles into galaxies and collapses from there to form much denser stars; and how stellar winds and explosions stir up the remaining gas and control the rate at which new stars form are concepts that are far too complex for current programs, the authors said.

"The simulations invoke many parameters to describe the four per cent of the universe that is made up of baryonic matter " But they said the simulations were not nearly as comprehensive for dark matter and dark energy, which make up the remaining 96 per cent of the universe.

So computer simulations are not about to revolutionise the way we think about the formation of galaxies.

"I think we are a long way from achieving this. There is so much more physics that needs to be included. It will be 10 to 20 years before we get this right." - Bland-Hawthorn.

Regardless, computer simulation is still an invaluable tool. Working with up to 10 billion 'particles', the "computations yield structures that look a good deal like real galaxies and clusters of galaxies," the authors said.

These include spiral galaxies which resemble neighbouring Andromeda and our own Milky Way, "adding to the evidence that our picture for the evolution of the universe is on the right track."

In turn, the reliability of computer simulations will improve as actual observations, such as those of forming stars, are applied to simulation programs.

Source

__________________


L

Posts: 131433
Date:
Permalink  
 

Kent State faculty and graduate students are among a team of physicists who recreated the material essence of the universe as it would have been mere microseconds after the Big Bang—a quark-gluon plasma.

This huge insight allows scientists to study matter in its earliest form and comes from an experiment carried out over the past five years at the Relativistic Heavy Ion Collider (RHIC), the giant crusher of nuclei located at Brookhaven National Lab, where scientists created a toy version of the cosmos amid high-energy collisions. Kent State is playing a vital role in this ongoing research partnership, which includes the University of California-Berkley, Massachusetts Institute of Technology, and the Academy of Sciences Nuclear Physics Institute.

At the fundamental level, this research advances our understanding of what the universe is really made of and how the early universe evolved into the universe as we now know it. In addition, the development of the equipment and techniques necessary to conduct the research at RHIC will ultimately improve nuclear equipment training for young researchers. Presently, nuclear techniques are used extensively in cancer radiotherapy and non-destructive analysis of steel, oil samples, ceramics and many other materials. As our understanding, equipment and techniques improve, we are able to better treat cancerous tumours and conduct material analysis.

The researchers’ work has appeared in the journals Nuclear Physics A and Physical Review Letters, as well as the Journal of Physics G: Nuclear and Particle Physics, and was presented at the annual meeting of the American Physical Society. Links to the most recent articles are available HERE.

Source

__________________
«First  <  16 7 8 | Page of 8  sorted by
Quick Reply

Please log in to post quick replies.



Create your own FREE Forum
Report Abuse
Powered by ActiveBoard