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Cosmology

Cosmology is the astrophysical study of the history, structure, and dynamics of the universe. It addresses fundamental questions about the nature and evolution of the universe.

Cosmology includes topics such as Big bang, Cosmic abundance, Microwave background, Cosmological constant, Dark energy and matter, Event horizon, Expansion of the universe, Galaxy clusters, Hubble expansion, Inflation, Olber's paradox, Redshift, Steady state theory and Universe.

 

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Rewriting general relativity? Putting a new model of quantum gravity under the microscope Last Updated on 2009-08-24 00:00:00 American Physical Society (Aug. 24, 2009) – Does an exciting but controversial new model of quantum gravity reproduce Einstein's theory of general relativity? Scientists at Texas A&M University in the US explore this question in a paper appearing in Physical Review Letters and highlighted with a Viewpoint in the August 24th issue of Physics (http://physics.aps.org). FIGURE CAPTION: Scientists are trying to figure out to what extent a new theory of quantum gravity will reproduce general relativity -- the theory that currently explains, to very high accuracy, how masses curve spacetime and create the influence of gravity. Credit: Image copyright American Physical Society, Illustration: Carin Cain "If it ain't broke, don't fix it," sums up fairly well how many scientists have viewed Einstein's theory of general relativity. The theory, which Einstein developed in the early 20th... More »
Cosmic Journey - A History of Scientific Cosmology Last Updated on 2009-01-28 14:12:47 The history of cosmology is a grand story of discovery, from ancient Greek astronomy to space telescopes. This Website, prepared by experts, mirrors the structure of the science, with cosmological theory and astronomical instruments side by side. See also: "Exhibits and other online resources for history of physics and allied fields" (AIP) Brought to you by the Center for History of Physics, a Division of the American Institute of Physics.   More »
Notes from the Astronomy Underground- Astropalooza Last Updated on 2008-09-28 00:00:00   According to the tagline in Ridley Scott’s 1979 blockbuster Alien, “In space, no one can hear you scream.” It’s true that sound waves, unlike light, need a medium- some kind of substance to carry their energy across a distance. And space is a vacuum, which, save the occasional solar system, fuzzy nebula, or bizarre stellar end product, is devoid of any respectable amount of matter. No matter, no sound, right?   Well, almost. Space is not completely empty. There are about one or two hydrogen molecules per square centimeter in the sparsest of regions. It beats our clumsy, terrestrial vacuum chambers handedly, but it’s not a vacuum in the strictest connotation of the word. Sound waves can still propagate through space, but so slowly and ineffectively that it would be pointless for aerophilic humans to do anything about it. Unless of course, we had ears many millions... More »
Notes from the Astronomy Underground: Another Shameless Plug Last Updated on 2008-07-25 00:00:00 Things have been rather frenzied this summer, to say the least. I'm quickly learning that the once-venerated HST is a dilapidated geriatrics ward of telescopy, one whose shoddy WFPC2 camera I can only imagine was MacGuyvered from popsicle sticks, dryer lint, and unsold copies of Deep Blue Something's latest album. Because, well, we're never really going to run out of those, now are we? But there has been one very positive development in the last few months. As a serious Dude of Outreach here, I've had a chance to look into the Hayden Planetarium's latest version of their Digital Universe Atlas. This runs on Partiview, visualization software that allows you the thrill of aimless, haphazard flight without the disappointment of waking up from that amazing dream or crashing from that Friday night post-rave mescaline high. Or in my case, it saves me from doing grownup work and lets me play... More »
Early Cosmologies Last Updated on 2008-06-11 00:00:00 As humans struggle to understand the universe, we are like explorers on a strange island in an unknown sea. At this point in our explorations we know that the island is made of rocks and grains of sand. We know how big it is, we know that the sea is large, and we know that there are many other islands out there in the distance. Now we ask a series of deeper questions about our larger environment. Do the islands go on forever? Does the sea go on forever? Does our world have an edge, or is it infinite? These are questions that astronomers have only just begun to answer with some confidence. Cosmology is the study of the size and structure of the universe – In other words, the "geography" of the universe as a single system. Our subject is the universe, defined as all matter and energy in existence anywhere, observable or not. The scientific method is stretched thin in our speculation... More »