Large Hadron Collider Used to Recreate Miniature Version of Beginning of Universe

Posted by on October 14, 2010 No comments

Einstein’s famous E=mc2 equation and the Large Hadron Collider to recreate a miniature version of the event at the origins of our Universe, and the first findings from their work were published in the journal Physical Review Letters.

Dr. Andreas Warburton of McGill’s Department of Physics made leading contributions to the analysis of data from the experiment, known as “ATLAS,” meaning the findings have a special significance for Canadian science.

Warburton and 3171 colleagues from around the world are using the data collected from the recreation in an attempt to look for exotic new particles whose existence is suggested by theoretical calculations. His work may help to revolutionize our understanding of the fundamental components of the Universe.

“Understanding whether new kinds of matter exist or not is interesting because it holds clues to knowledge about how the Universe works fundamentally,” Warburton said. “The Standard Model of Particle Physics is a useful theoretical framework but it is known to be flawed and incomplete — we are searching for new particles that lie outside this framework, and we are also seeking to establish the non-existence of these hypothetical particles.” The research published this week falls into the latter category and is about determining the mass of a theoretical particle known as an “excited quark.”

Warburton offered the following analogy: “By exploring the high-energy subatomic frontier, it is metaphorically somewhat like turning over stones at the seashore and looking for new and interesting surprises hiding under the rocks. Here we are looking under stones that have been too heavy to lift before this summer. What we see or don’t see under those stones helps to paint new pictures about how the Universe works and tells us which stones are most important to look under next.”

Efficient Plastic Solar Cells

Posted by on October 14, 2010 No comments

The discovery, posted online and slated for publication in an upcoming issue of the journal Nature Materials, reveals that energy-carrying particles generated by packets of light can travel on the order of a thousand times farther in organic (carbon-based) semiconductors than scientists previously observed. This boosts scientists’ hopes that solar cells based on this budding technology may one day overtake silicon solar cells in cost and performance, thereby increasing the practicality of solar-generated electricity as an alternate energy source to fossil fuels.

“Organic semiconductors are promising for solar cells and other uses, such as video displays, because they can be fabricated in large plastic sheets,” said Vitaly Podzorov, assistant professor of Physics at Rutgers. “But their limited photo-voltaic conversion efficiency has held them back. We expect our discovery to stimulate further development and progress.”

Podzorov and his colleagues observed that excitons — particles that form when semiconducting materials absorb photons, or light particles — can travel a thousand times farther in an extremely pure crystal organic semiconductor called rubrene. Until now, excitons were typically observed to travel less than 20 nanometers — billionths of a meter — in organic semiconductors.

“This is the first time we observed excitons migrating a few microns,” said Podzorov, noting that they measured diffusion lengths from two to eight microns, or millionths of a meter. This is similar to exciton diffusion in inorganic solar cell materials such as silicon and gallium arsenide.

“Once the exciton diffusion distance becomes comparable to the light absorption length, you can collect most of the sunlight for energy conversion,” he said.

Nobel Prize in Physics for 2010

Posted by on October 10, 2010 Comments Off on Nobel Prize in Physics for 2010

ScienceDaily (Oct. 5, 2010) — The Royal Swedish Academy of Sciences has awarded the Nobel Prize in Physics for 2010 to Andre Geim and Konstantin Novoselov, both of the University of Manchester, “for groundbreaking experiments regarding the two-dimensional material graphene.”

A thin flake of ordinary carbon, just one atom thick, lies behind this year’s Nobel Prize in Physics. Geim and Novoselov have shown that carbon in such a flat form has exceptional properties that originate from the remarkable world of quantum physics.

Graphene is a form of carbon. As a material it is completely new — not only the thinnest ever but also the strongest. As a conductor of electricity it performs as well as copper. As a conductor of heat it outperforms all other known materials. It is almost completely transparent, yet so dense that not even helium, the smallest gas atom, can pass through it. Carbon, the basis of all known life on earth, has surprised us once again.

Geim and Novoselov extracted the graphene from a piece of graphite such as is found in ordinary pencils. Using regular adhesive tape they managed to obtain a flake of carbon with a thickness of just one atom. This at a time when many believed it was impossible for such thin crystalline materials to be stable.

However, with graphene, physicists can now study a new class of two-dimensional materials with unique properties. Graphene makes experiments possible that give new twists to the phenomena in quantum physics. Also a vast variety of practical applications now appear possible including the creation of new materials and the manufacture of innovative electronics. Graphene transistors are predicted to be substantially faster than today’s silicon transistors and result in more efficient computers.

Since it is practically transparent and a good conductor, graphene is suitable for producing transparent touch screens, light panels, and maybe even solar cells.

When mixed into plastics, graphene can turn them into conductors of electricity while making them more heat resistant and mechanically robust. This resilience can be utilised in new super strong materials, which are also thin, elastic and lightweight. In the future, satellites, airplanes, and cars could be manufactured out of the new composite materials.

This year’s Laureates have been working together for a long time now. Konstantin Novoselov, 36, first worked with Andre Geim, 51, as a PhD-student in the Netherlands. He subsequently followed Geim to the United Kingdom. Both of them originally studied and began their careers as physicists in Russia. Now they are both professors at the University of Manchester.

The Big Bang Theory

Posted by on October 10, 2010 Comments Off on The Big Bang Theory

The theory that the universe began in a state of extremely high density and has been expanding since some particular instant that marked the origin of the universe. The big bang is the generally accepted cosmological theory; the incorporation of developments in elementary particle theory has led to the inflationary universe version. The predictions of the inflationary universe and older big bang theories are the same after the first 10−35 s. See also Inflationary universe cosmology.

Two observations are at the base of observational big bang cosmology. First, the universe is expanding uniformly, with objects at greater distances receding at a greater velocity. Second, the Earth is bathed in the cosmic background radiation, an isotropic glow of radiation that has the characteristics expected from the remnant of a hot primeval fireball.

Tracing the expansion of the universe back in time shows that the universe would have been compressed to infinite density approximately 8–16 × 109 years ago. In the big bang theory, the universe began at that time as a so-called big bang began the expansion. The big bang was the origin of space and time.

In 1917, Albert Einstein found a solution to his own set of equations from his general theory of relativity that predicted the nature of the universe. His universe, though, was unstable: it could only be expanding or contracting. This seemed unsatisfactory at the time, for the expansion had not yet been discovered, so Einstein arbitrarily introduced a special term—the cosmological constant—into his equations to make the universe static. The need for the cosmological constant seemed to disappear with Hubble’s discovery of the expansion, though the cosmological constant has subsequently reappeared in some models.

Further solutions to Einstein’s equations, worked out in the 1920s, are at the basis of the cosmological models that are now generally accepted. These solutions indicate that the original “cosmic egg” from which the universe was expanding was hot and dense. This is the origin of the current view that the universe was indeed very hot in its early stages.