How did the universe begin? Hot Big Bang or slow thaw?

Did the universe begin with a hot Big Bang or did it slowly thaw from an extremely cold and almost static state?

Did the universe begin with a hot Big Bang or did it slowly thaw from an extremely cold and almost static state? Prof. Dr. Christof Wetterich, a physicist at Heidelberg University, has developed a theoretical model that complements the nearly 100-year-old conventional model of cosmic expansion. According to Wetterich's theory, the Big Bang did not occur 13.8 billion years ago -- instead, the birth of the universe stretches into the infinite past. This view holds that the masses of all particles constantly increase. The scientist explains that instead of expanding, the universe is shrinking over extended periods of time.

Cosmologists usually call the birth of the universe the Big Bang. The closer we approach the Big Bang in time, the stronger the geometry of space and time curves. Physicists call this a singularity -- a term describing conditions whose physical laws are not defined. In the Big Bang scenario, the spacetime curvature becomes infinitely large. Shortly after the Big Bang, the universe was extremely hot and dense. Prof. Wetterich believes, however, that a different "picture" is also possible. If the masses of all elementary particles grow heavier over time and gravitational force weakens, the universe could have also had a very cold, slow start. In that view, the universe always existed and its earliest state was virtually static, with the Big Bang stretching over an infinitely long time in the past. The scientist from the Institute for Theoretical Physics assumes that the earliest "events" that are indirectly observable today came to pass 50 trillion years ago, and not in the billionth of a billionth of a billionth of a second after the Big Bang. "There is no longer a singularity in this new picture of the cosmos," says Prof. Wetterich.
His theoretical model explains dark energy and the early "inflationary universe" with a single scalar field that changes with time, with all masses increasing with the value of this field. "It's reminiscent of the Higgs boson recently discovered in Geneva. This elementary particle confirmed the physicists' assumption that particle masses do indeed depend on field values and are therefore variable," explains the Heidelberg scientist. In Wetterich's approach, all masses are proportional to the value of the so-called cosmon field, which increases in the course of cosmological evolution. "The natural conclusion of this model is a picture of a universe that evolved very slowly from an extremely cold state, shrinking over extended periods of time instead of expanding," explains Prof. Wetterich.
Wetterich stresses that this in no way renders the previous view of the Big Bang "invalid," however. "Physicists are accustomed to describing observed phenomena using different pictures." Light, for example, can be depicted as particles and as a wave. Similarly, his model can be seen as a picture equivalent to the Big Bang. "This is very useful for many practical predictions on the consequences that arise from this new theoretical approach. However, describing the 'birth' of the universe without a singularity does offer a number of advantages," emphasises Prof. Wetterich. "And in the new model, the nagging dilemma of 'there must have been something before the Big Bang' is no longer an issue."

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The above story is based on materials provided by Heidelberg University. Note: Materials may be edited for content and length.

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Journal References:

1. C. Wetterich. Variable gravity Universe. Physical Review D, 2014; 89 (2) DOI: 10.1103/PhysRevD.89.024005
2. C. Wetterich. Universe without expansion. Physics of the Dark Universe, 2013; 2 (4): 184 DOI: 10.1016/j.dark.2013.10.002

How the universe has cooled since the Big Bang fits Big Bang theory

Radio waves from a distant quasar pass through another galaxy on their way to Earth. Changes in the radio waves indicate the temperature of the gas

Astronomers using a CSIRO radio telescope have taken the Universe's temperature, and have found that it has cooled down just the way the Big Bang theory predicts.

Using the CSIRO Australia Telescope Compact Array near Narrabri, NSW, an international team from Sweden, France, Germany and Australia has measured how warm the Universe was when it was half its current age.
"This is the most precise measurement ever made of how the Universe has cooled down during its 13.77 billion year history," said Dr Robert Braun, Chief Scientist at CSIRO Astronomy and Space Science.
Because light takes time to travel, when we look out into space we see the Universe as it was in the past -- as it was when light left the galaxies we are looking at. So to look back half-way into the Universe's history, we need to look half-way across the Universe.
How can we measure a temperature at such a great distance?
The astronomers studied gas in an unnamed galaxy 7.2 billion light-years away [a redshift of 0.89].
The only thing keeping this gas warm is the cosmic background radiation -- the glow left over from the Big Bang.
By chance, there is another powerful galaxy, a quasar (called PKS 1830-211), lying behind the unnamed galaxy.
Radio waves from this quasar come through the gas of the foreground galaxy. As they do so, the gas molecules absorb some of the energy of the radio waves. This leaves a distinctive "fingerprint" on the radio waves.
From this "fingerprint" the astronomers calculated the gas's temperature. They found it to be 5.08 Kelvin (-267.92 degrees Celsius): extremely cold, but still warmer than today's Universe, which is at 2.73 Kelvin (-270.27 degrees Celsius).
According to the Big Bang theory, the temperature of the cosmic background radiation drops smoothly as the Universe expands. "That's just what we see in our measurements. The Universe of a few billion years ago was a few degrees warmer than it is now, exactly as the Big Bang Theory predicts," said research team leader Dr Sebastien Muller of Onsala Space Observatory at Chalmers University of Technology in Sweden.

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Story Source:
The above story is based on materials provided by CSIRO Australia. Note: Materials may be edited for content and length.

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Journal Reference:

1. S. Muller , A. Beelen, J. H. Black, S. J. Curran, C. Horellou, S. Aalto, F. Combes, M. Guelin, C. Henkel. A precise and accurate determination of the cosmic microwave background temperature at z=0.89. Astronomy & Astrophysics, 2013 [link]

Big bang - Birth of the universe | Sci-english.blogspot.com

Big bang - Birth of the universe | Sci-english.blogspot.com

The big bang poses a big question: if it was indeed the cataclysm that blasted our universe into existence 13.7 billion years ago, what sparked it?

Three Perimeter Institute researchers have a new idea about what might have come before the big bang. It's a bit perplexing, but it is grounded in sound mathematics and is it testable?

What we perceive as the big bang, they argue, could be the three-dimensional "mirage" of a collapsing star in a universe profoundly different than our own.
"Cosmology's greatest challenge is understanding the big bang itself," write Perimeter Institute Associate Faculty member Niayesh Afshordi, Affiliate Faculty member and University of Waterloo professor Robert Mann, and PhD student Razieh Pourhasan.
Conventional understanding holds that the big bang began with a singularity -- an unfathomably hot and dense phenomenon of spacetime where the standard laws of physics break down. Singularities are bizarre, and our understanding of them is limited.
"For all physicists know, dragons could have come flying out of the singularity," Afshordi says in an interview with Nature.

The problem, as the authors see it, is that the big bang hypothesis has our relatively comprehensible, uniform, and predictable universe arising from the physics-destroying insanity of a singularity. It seems unlikely.
So perhaps something else happened. Perhaps our universe was never singular in the first place.
Their suggestion: our known universe could be the three-dimensional "wrapping" around a four-dimensional black hole's event horizon. In this scenario, our universe burst into being when a star in a four-dimensional universe collapsed into a black hole.
In our three-dimensional universe, black holes have two-dimensional event horizons -- that is, they are surrounded by a two-dimensional boundary that marks the "point of no return." In the case of a four-dimensional universe, a black hole would have a three-dimensional event horizon.
In their proposed scenario, our universe was never inside the singularity; rather, it came into being outside an event horizon, protected from the singularity. It originated as -- and remains -- just one feature in the imploded wreck of a four-dimensional star.
The researchers emphasize that this idea, though it may sound "absurd," is grounded firmly in the best modern mathematics describing space and time. Specifically, they've used the tools of holography to "turn the big bang into a cosmic mirage." Along the way, their model appears to address long-standing cosmological puzzles and -- crucially -- produce testable predictions.
Of course, our intuition tends to recoil at the idea that everything and everyone we know emerged from the event horizon of a single four-dimensional black hole. We have no concept of what a four-dimensional universe might look like. We don't know how a four-dimensional "parent" universe itself came to be.
But our fallible human intuitions, the researchers argue, evolved in a three-dimensional world that may only reveal shadows of reality.
They draw a parallel to Plato's allegory of the cave, in which prisoners spend their lives seeing only the flickering shadows cast by a fire on a cavern wall.
"Their shackles have prevented them from perceiving the true world, a realm with one additional dimension," they write. "Plato's prisoners didn't understand the powers behind the sun, just as we don't understand the four-dimensional bulk universe. But at least they knew where to look for answers."

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Story Source:
The above story is based on materials provided by Perimeter Institute. Note: Materials may be edited for content and length.

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Journal Reference:

1. Razieh Pourhasan, Niayesh Afshordi, Robert B. Mann. Out of the White Hole: A Holographic Origin for the Big Bang. arXiv, 2014 [link]

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