physics4me

physicsgg

Posts Tagged ‘Universe

The beginning of everything

leave a comment »

A new paradigm shift for the infant universe

The power spectrum in the cosmic microwave background (CMB) predicted in Loop Quantum Cosmology and in the Standard Inflationary Scenario are contrasted in this plot, which shows their ratio as a function of k, the inverse of wave length, of fluctuations in the CMB. For many of the parameters, observable wave numbers k are greater than 9 and the two predictions are indistinguishable. For a narrow window of parameters, observable k can be smaller than 9. Then the two predictions differ. Both are in agreement with currently available data, but future observations should be able to distinguish between them. Credit: Ashtekar lab, Penn State University

A new paradigm for understanding the earliest eras in the history of the universe has been developed by scientists at Penn State University. Using techniques from an area of modern physics called loop quantum cosmology, developed at Penn State, the scientists now have extended analyses that include quantum physics farther back in time than ever before—all the way to the beginning. The new paradigm of loop quantum origins shows, for the first time, that the large-scale structures we now see in the universe evolved from fundamental fluctuations in the essential quantum nature of “space-time,” which existed even at the very beginning of the universe over 14 billion years ago. The achievement also provides new opportunities for testing competing theories of modern cosmology against breakthrough observations expected from next-generation telescopes. The research will be published on 11 December 2012 as an “Editor’s Suggestion” paper in the scientific journal Physical Review Letters.

Read more at: phys.org

Written by physicsgg

November 29, 2012 at 1:14 pm

Posted in COSMOLOGY

Tagged with ,

Network Cosmology

leave a comment »

Dmitri Krioukov, Maksim Kitsak, Robert S. Sinkovits, David Rideout, David Meyer & Marián Boguñá

Prediction and control of the dynamics of complex networks is a central problem in network science. Structural and dynamical similarities of different real networks suggest that some universal laws might accurately describe the dynamics of these networks, albeit the nature and common origin of such laws remain elusive. Here we show that the causal network representing the large-scale structure of spacetime in our accelerating universe is a power-law graph with strong clustering, similar to many complex networks such as the Internet, social, or biological networks. We prove that this structural similarity is a consequence of the asymptotic equivalence between the large-scale growth dynamics of complex networks and causal networks. This equivalence suggests that unexpectedly similar laws govern the dynamics of complex networks and spacetime in the universe, with implications to network science and cosmology.
Read more: nature.com

Read also: Universe Grows Like a Giant Brain: livescience.com

Written by physicsgg

November 27, 2012 at 1:24 pm

Posted in COSMOLOGY

Tagged with

Galaxies without stars: The problem of the missing hydrogen in the early Universe

leave a comment »

Hydrogen is the most common element in the Universe, making up 75% of all normal matter and the content of stars.

Although stars themselves are hot, they can only form out of the coldest gas when a massive cloud of hydrogen can collapse under its own gravity until nuclear fusion starts – the fusing of atoms together which releases the huge amounts of energy we see as starlight.

Astronomers have been puzzled as to why they could not detect this cold star-forming gas in the most distant, and hence older, regions of the Universe.

At such vast look-back times, astronomers expected the gas to be much more abundant as it has yet to be consumed by star formation.

Dr Stephen Curran, from the University of Sydney’s School of Physics and CAASTRO – the ARC Centre for All-sky Astrophysics – and Dr Matthew Whiting, from CSIRO Astronomy and Space Science, have addressed this problem by devising a model that shows how the supermassive black hole, lurking within the centre of each active galaxy, is able to ionise all of the surrounding gas even in the very largest galaxies.

When hydrogen gas is in this state, where the electron is ripped out of the atom, the gas it too agitated to allow the cloud to collapse and form stars. Also, when ionised, it cannot be detected through radio waves at 21-centimetres – the way cold star-forming gas is normally found. “Previously, we had not known just how much of the gas was ionised by the black hole accretions disks – we had thought that perhaps it was just enough to take the abundance of cool gas to below the detection threshold of current radio telescopes.

So we’d thought that it was maybe a telescope sensitivity issue,” said Dr Curran. Dr Curran and Dr Whiting’s latest research, published in The Astrophysical Journal on 10 November 2012, shows that the extreme ultra-violet radiation given off by the material being sucked in – at near light-speeds – to the black hole, is sufficient to ionise all of the gas in even the very largest galaxies. “In order to probe further back in time, we choose the most distant radio sources. What appears as faint light from these, to us on Earth, is actually extreme ultra-violet, dimmed and stretched (redshifted) to visible light on its several billion year journey to us,” explained Dr Curran. “Unfortunately, these are the only objects we know of at the very limits of the cosmos and within these the radiation from the central black hole is so intense as to heat all the gas to the point where it cannot form stars. “We have shown that rather than being a telescope sensitivity issue, all of the billions of suns worth of gas is indeed ionised.

This means that even the Square Kilometre Array – the biggest radio telescope, which is currently being built in Australia, New Zealand and southern Africa – will not be able to detect star-forming gas in these galaxies,” said Dr Curran. “The Square Kilometre Array will excel, however, in detecting very cold gas that is too faint to be detected by optical telescopes, which must have existed to give us the stars and galaxies we see today.”

Read more at: phys.org

Written by physicsgg

November 9, 2012 at 2:39 pm

Posted in ASTRONOMY, ASTROPHYSICS

Tagged with

The Beginning and End of the Universe

leave a comment »


Berkeley Lab’s Science at the Theater traveled across the Bay to San Francisco’s Herbst Theater on Oct. 22, 2012 for a star turn by two of the Lab’s Nobel laureates. George Smoot received the 2006 Nobel Prize in Physics for the “discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.” Saul Perlmutter received the 2011 Nobel Prize in Physics for “for the discovery of the accelerating expansion of the Universe through observations of distant supernovae.” The host for the conversation was KQED’s Michael Krasny.

http://youtu.be/pfPKAjkTplc

Written by physicsgg

October 28, 2012 at 8:05 am

Measuring the Universe

leave a comment »


by Royal Observatory Greenwich
This is the film from our micro exhibition ‘Measuring the Universe: from the transit of Venus to the edge of the cosmos’

Written by physicsgg

May 30, 2012 at 8:42 am

Posted in ASTRONOMY, ASTROPHYSICS

Tagged with

The Known Universe

leave a comment »

http://vimeo.com/19568852

The Known Universe takes viewers from the Himalayas through our atmosphere and the inky black of space to the afterglow of the Big Bang. Every star, planet, and quasar seen in the film is possible because of the world’s most complete four-dimensional map of the universe, the Digital Universe Atlas that is maintained and updated by astrophysicists at the American Museum of Natural History.
The new film, created by the Museum, is part of an exhibition, Visions of the Cosmos: From the Milky Ocean to an Evolving Universe, at the Rubin Museum of Art in Manhattan through May 2010. Data: Digital Universe, American Museum of Natural History haydenplanetarium.org/universe/ Visualization Software: Uniview by SCISS Director: Carter Emmart Curator: Ben R. Oppenheimer Producer: Michael Hoffman Executive Producer: Ro Kinzler Co-Executive Producer: Martin Brauen Manager, Digital Universe Atlas: Brian Abbott Music: Suke Cerulo

Written by physicsgg

December 7, 2011 at 1:02 pm

Posted in ASTRONOMY, COSMOLOGY, SPACE

Tagged with

Mass of the universe in a black hole

leave a comment »

Nikodem J. Poplawski
If spacetime torsion couples to the intrinsic spin of matter according to the Einstein-Cartan-Sciama-Kibble theory of gravity, then the resulting gravitational repulsion at supranuclear densities prevents the formation of singularities in black holes.
Consequently, the interior of every black hole becomes a new universe that expands from a nonsingular bounce. We consider gravitational collapse of fermionic spin-fluid matter with the stiff equation of state in a stellar black hole.
Such a collapse increases the mass of the matter, which occurs through the Parker-Zel’dovich-Starobinskii quantum particle production in strong, anisotropic gravitational fields. The subsequent pair annihilation changes the stiff matter into an ultrarelativistic fluid.
We show that the universe in a black hole of mass MBH at the bounce has a mass

M~ MBHmn1/2 / mPl3/2

where mn is the mass of a neutron and mPl is the reduced Planck mass.
For a typical stellar black hole, Mb is about 1032 solar masses, which 106 larger than the mass of our Universe. As the relativistic black-hole universe expands, its mass decreases until the universe becomes dominated by nonrelativistic heavy particles…..
Read more: http://arxiv.org
Read also: http://arxiv.org2

Written by physicsgg

October 29, 2011 at 4:47 pm

Posted in ASTROPHYSICS, COSMOLOGY

Tagged with ,

Life in the Universe by Stephen Hawking

with 5 comments

In this talk, I would like to speculate a little, on the development of life in the universe, and in particular, the development of intelligent life. I shall take this to include the human race, even though much of its behaviour through out history, has been pretty stupid, and not calculated to aid the survival of the species. Two questions I shall discuss are, ‘What is the probability of life existing else where in the universe?’ and, ‘How may life develop in the future?’

It is a matter of common experience, that things get more disordered and chaotic with time. This observation can be elevated to the status of a law, the so-called Second Law of Thermodynamics. This says that the total amount of disorder, or entropy, in the universe, always increases with time. However, the Law refers only to the total amount of disorder. The order in one body can increase, provided that the amount of disorder in its surroundings increases by a greater amount. This is what happens in a living being. One can define Life to be an ordered system that can sustain itself against the tendency to disorder, and can reproduce itself. That is, it can make similar, but independent, ordered systems. To do these things, the system must convert energy in some ordered form, like food, sunlight, or electric power, into disordered energy, in the form of heat. A laptopIn this way, the system can satisfy the requirement that the total amount of disorder increases, while, at the same time, increasing the order in itself and its offspring. A living being usually has two elements: a set of instructions that tell the system how to sustain and reproduce itself, and a mechanism to carry out the instructions. In biology, these two parts are called genes and metabolism. But it is worth emphasising that there need be nothing biological about them. For example, a computer virus is a program that will make copies of itself in the memory of a computer, and will transfer itself to other computers. Thus it fits the definition of a living system, that I have given. Like a biological virus, it is a rather degenerate form, because it contains only instructions or genes, and doesn’t have any metabolism of its own. Instead, it reprograms the metabolism of the host computer, or cell. Some people have questioned whether viruses should count as life, because they are parasites, and can not exist independently of their hosts. But then most forms of life, ourselves included, are parasites, in that they feed off and depend for their survival on other forms of life. I think computer viruses should count as life. Maybe it says something about human nature, that the only form of life we have created so far is purely destructive. Talk about creating life in our own image. I shall return to electronic forms of life later on…… Read the rest of this entry »

Written by physicsgg

August 28, 2011 at 8:23 pm