Posts Tagged ‘Big Bang

The beginning of everything

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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.

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Written by physicsgg

November 29, 2012 at 1:14 pm


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The brain behind TV’s The Big Bang Theory

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Brad Hooker talks with David Saltzberg, science advisor to The Big Bang Theory

For those who live, breathe and laugh physics, one show entangles them all: The Big Bang Theory. Now in its fifth season on CBS, the show follows a group of geeks, including a NASA engineer, an astrophysicist and two particle physicists.

Every episode has at least one particle physics joke. On faster-than-light neutrinos: “Is this observation another Swiss export full of more holes than their cheese?” On Saul Perlmutter clutching the Nobel Prize: “What’s the matter, Saul? You afraid somebody’s going to steal it, like you stole Einstein’s cosmological constant?”

To make these jokes timely and accurate, while sprinkling the sets with authentic scientific plots and posters, the show’s writers depend on one physicist, David Saltzberg. Since the first episode, Saltzberg’s dose of realism has made science chic again, and has even been credited with increasing admissions to physics programs. Symmetry writer Brad Hooker asked the LHC physicist, former Tevatron researcher and University of California, Los Angeles professor to explain how he walks the tightrope between science and sitcom…..

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Written by physicsgg

March 4, 2012 at 9:30 am

Posted in HUMOR

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Standard Big-Bang Nucleosynthesis up to CNO with an improved extended nuclear network

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Primordial or Big Bang nucleosynthesis (BBN) is one of the three strong evidences for the Big- Bang model together with the expansion of the Universe and the Cosmic Microwave Background radiation. In this study, we improve the standard BBN calculations taking into account new nuclear physics analyses and we enlarge the nuclear network until Sodium. This is, in particular, important to evaluate the primitive value of CNO mass fraction that could affect Population III stellar evolution. For the first time we list the complete network of more than 400 reactions with references to the origin of the rates, including \approx 270 reaction rates calculated using the TALYS code. Together with the cosmological light elements, we calculate the primordial Beryllium, Boron, Carbon, Nitrogen and Oxygen nuclei. We performed a sensitivity study to identify the important reactions for CNO, 9Be and Boron nucleosynthesis. We reevaluated those important reaction rates using experimental data and/or theoretical evaluations. The results are compared with precedent calculations: a primordial Beryllium abundance increase by a factor of 4 compared to its previous evaluation, but we note a stability for B/H and for the CNO/H abundance ratio that remains close to its previous value of 0.7 \times 10-15. On the other hand, the extension of the nuclear network has not changed the 7Li value, so its abundance is still 3-4 times greater than its observed spectroscopic value….

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Written by physicsgg

July 9, 2011 at 2:47 pm

The Curious Case of Lemaitre’s Equation No. 24

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Sidney van den Bergh
In August of 1961 Abbé Georges Lemaître told me (with a twinkle in his eyes) that, being a priest, he felt a slight bias in favor of the idea that the Universe had been created. It must therefore have been a particular pleasure for him (Lemaître 1927) to have been the first to find both observational and theoretical evidence for the expansion of the Universe. His observational discovery was based on the published distances and radial velocities of 42 galaxies. Lemaître’s theretical result was based on the finding that the Universe is unstable, so that pertubations tend to grow. These results, which were published in French and in a relatively obscure journal, anticipated the work of Edwin Hubble (1929) by two years. It might therefore have been appropriate to assign the credit for the discovery of the expansion of the Universe to Lemaître, rather than to Hubble (Peebles 1984). The early evolution of our understanding of the expansion (and the scale-size) of the Universe has recently been discussed in detail by Kragh & Smith (2003) and by Nussbaumer & Bieri (2009). Because it had been published in such a low-impact place an authorized translation of Lemaître’s discovery paper was reprinted in the widely read Monthly Notices of the Royal Astronomical Society (Lemaître 1931). It is this translation, rather than the French original, which formed the basis of most subsequent discussions of the discovery of the expansion of the Universe. A comparison between the original French text and its English translation shows a few, but very interesting, differences (e.g. Peebles 1984, Way & Nussbaumer 2011). It does not previously seem to have been noted that one of the 31 equations in Lemaître’s paper is also different in the original and in its translation. [The unknown translator did his work well and corrected a typographical error in one of these equations in the French original version of the paper.] In the English translation the term

in which v is the radial velocity, r the distance and c the velocity of light is omitted. Of the three numbers given above the speed of light in cm/s, and the length of the parsec are well-known. Only the cosmic expansion term 625 x 105 [corresponding in modern parlance to a Hubble constant of 625 km/s] might possibly be considered to be controversial. The fact that dropping this term from Lemaître’s Eqn. 24 was intentional is supported by the fact that a short paragraph in the paper, which deals with the determination of what we now call the Hubble parameter was also omitted from the English translation of the text. (The latter fact had already been noted previously by Peebles (1984) and by Way & Nussbaumer 2011). That mention of the expansion of the Universe was omitted from the English version of both Eqn. 24, and from the English text, suggests that this exclusion by the translator was deliberate rather than accidental. The Editor-in-chief of the Monthly Notices has kindly informed me that his office no longer has any records of the events related to the translation of Lemaître’s article in 1931. Another factor which may have influenced the lack of credit assigned to Lemaître for the discovery of the expansion of the Universe is that the English translation of the article did not include the footnotes to the original French version of the article. One of these footnotes explains in detail how using weighted and unweighted radial velocities for galaxies leads to slightly different values for the Hubble parameter. In summary it appears that the translator of Lemaître’s 1927 article deliberately deleted those parts of the paper that dealt with the determination of what is presently referred to as the Hubble parameter. The reason for this remains a mystery.

Written by physicsgg

June 11, 2011 at 7:53 am