Astro Bob | Celestial happenings you can see from your own backyard As bright as a hundred million Suns: The clusters of monster stars that lit up the early universe -- ScienceDaily The first stars in the Universe were born several hundred million years after the Big Bang, ending a period known as the cosmological 'dark ages' -- when atoms of hydrogen and helium had formed, but nothing shone in visible light. Now two Canadian researchers have calculated what these objects were like: they find that the first stars could have clustered together in phenomenally bright groups, with periods when they were as luminous as 100 million Suns. Alexander DeSouza and Shantanu Basu, both of the University of Western Ontario in Canada, publish their results in a paper in Monthly Notices of the Royal Astronomical Society. The two scientists modelled how the luminosity of the stars would have changed as they formed from the gravitational collapse of disks of gas. In a small cluster of even 10 to 20 protostars, the ongoing bursts would mean the cluster would spend large periods with enhanced brightness.
New? Start Here Hi, and welcome to my site “Of Particular Significance”. If you are an interested layperson, whether you have very little knowledge of science or quite a lot already, this website is mainly intended for you — although as you’ll see, it has a number of scientists among its readers. It’s still young and growing, so check back often for new material. You’ll see there’s a blog with up-to-date comments, but most of the web-pages are permanent or semi-permanent articles. To step your way through the website from the beginning, click here to go to my “About this site and how to use it” page. Like this: Like Loading... 125 Great Science Videos: From Astronomy to Physics & Psychology Astronomy & Space Travel A Brief, Wondrous Tour of Earth (From Outer Space) - Video - Recorded from August to October, 2011 at the International Space Station, this HD footage offers a brilliant tour of our planet and stunning views of the aurora borealis.A Universe from Nothing - Video - In 53 minutes, theoretical physicist Lawrence Krauss answers some big enchilada questions, including how the universe came from nothing.A Year of the Moon in 2.5 Minutes - Video - The Lunar Reconnaissance Orbiter has been orbiting the moon for over a year. The footage gets compressed into 2 slick minutes.A Day on Earth (as Seen From Space) - Video - Astronaut Don Pettit trained his camera on planet Earth, took a photo once every 15 seconds, and then created a brilliant time-lapse film.Atlantis's Final Landing at Kennedy Space Center - Video - After more than 30 years, the space shuttle era comes to a close. Physics Biology & Chemistry Environment, Geology and & Ecology Psychology & Neuroscience
BBC Space – Explore the planets, black holes, stars and more FQXi - Foundational Questions Institute Black Hole Cores May Not Be Infinitely Dense The cores of black holes may not hold points of infinite density as currently thought, but portals to elsewhere in the universe, theoretical physicists say. A black hole possesses a gravitational field so powerful that not even light can escape. A black hole generally forms after a star dies in a titanic explosion known as a supernova, which crushes the remaining core into dense lumps. A maddening enigma called a singularity -- a region of infinite density -- lies at the heart of each black hole, according to general relativity, the modern theory of gravity. Scientists have long sought ways to avoid the complete breakdown of all the known laws of physics brought on by singularities. These new findings are based on loop quantum gravity, one of the leading theories seeking to unite quantum mechanics and general relativity into a single theory that can explain all the forces of the universe. "Adding matter and having a black hole that evolves is what we are aiming for next," Pullin said.
Eliezer Yudkowsky on Bayes and science: what? By Massimo Pigliucci It is no secret that my already normally skeptical baloney detector now jumps to deep orange alert any time I hear the word “singularity.” I was not too impressed with David Chalmers’ lecture about it at the City University of New York Graduate Center, and I debated singularitarian guru Eliezer Yudkowsky on BloggingHeadsTV on the same topic. My later encounters with that particular group of techno-optimists and futurists have not improved my opinion of the whole shebang a bit. Still, in the spirit of open inquiry and of keeping myself on my own toes, I devoted about an hour to reading three not-so-recent posts by Yudkowsky on the theme of quantum mechanics, science and Bayesianism (the philosophy of science related to Bayesian statistics). I actually intended to read only one of Yudkowsky’s posts, intriguingly entitled “The Dilemma: Science or Bayes?” But I was disappointed. Now, I should hasten to say that I don’t really have a dog in this fight. So there.
Time Machines and Event Horizons » Undivided Looking I've written a pop-article about Time Machines and Event Horizons, which has appeared on the Scientific American blog Critical Opalescence. George Musser, my host, is an editor at Scientific American, and kindly gave me this opportunity to talk about some of my ideas in my article, The Generalized Second Law implies a Quantum Singularity Theorem. If you have any questions about the physics in the article, please feel free to leave comments on this post here. (Questions left on the Scientific American website will be answered in the comments to this post, if anywhere.) I am a postdoctoral researcher studying quantum gravity and black hole thermodynamics at the Institute for Advanced Study in Princeton.
Physics and Astronomy Glossary Technical terms of science have very specific meanings. Standard dictionaries are not always the best source of useful and correct definitions of them. This glossary is not intended to be complete. It focuses on those terms which give students particular difficulties. Some words have subtle and intricate meanings which cannot be encapsulated in a short definition. That's why textbooks exist. This document is continually under development and may never be finished. Glossary Accurate. Absolute uncertainty. Compare: relative uncertainty. Action. Avogadro's constant. One must specify whether the value of Avogadro's constant is expressed for a gram-mole or a kilogram-mole. Though it seems inconsistent, the SI base unit is the gram-mole. Is Avogadro's constant just a number? , e, 3, 100, etc. The reciprocal of Avogadro's constant is numerically equal to the unified atomic mass unit, u, that is, 1/12 the mass of the carbon 12 atom. 1 u = 1.66043 x 10-27 kg = 1/6.02252 x 1023 mole-1. Because. cgs.
Loop quantum gravity More precisely, space can be viewed as an extremely fine fabric or network "woven" of finite loops. These networks of loops are called spin networks. The evolution of a spin network over time is called a spin foam. Today LQG is a vast area of research, developing in several directions, which involves about 50 research groups worldwide. They all share the basic physical assumptions and the mathematical description of quantum space. Research into the physical consequences of the theory is proceeding in several directions. History The canonical version of the dynamics was put on firm ground by Thomas Thiemann, who defined an anomaly-free Hamiltonian operator, showing the existence of a mathematically consistent background-independent theory. General covariance and background independence In theoretical physics, general covariance is the invariance of the form of physical laws under arbitrary differentiable coordinate transformations. LQG is formally background independent. .
Physicists Discover Geometry Underlying Particle Physics Physicists have discovered a jewel-like geometric object that dramatically simplifies calculations of particle interactions and challenges the notion that space and time are fundamental components of reality. “This is completely new and very much simpler than anything that has been done before,” said Andrew Hodges, a mathematical physicist at Oxford University who has been following the work. The revelation that particle interactions, the most basic events in nature, may be consequences of geometry significantly advances a decades-long effort to reformulate quantum field theory, the body of laws describing elementary particles and their interactions. Interactions that were previously calculated with mathematical formulas thousands of terms long can now be described by computing the volume of the corresponding jewel-like “amplituhedron,” which yields an equivalent one-term expression. Locality is the notion that particles can interact only from adjoining positions in space and time.
How To Identify That Light In The Sky? What is that light in the sky? Perhaps one of humanity’s more common questions, an answer may result from a few quick observations. For example — is it moving or blinking? If so, and if you live near a city,the answer is typically an airplane, since planes are so numerous and so few stars and satellites are bright enough to be seen over the din of artificial city lights. SEE ALSO: Night on Earth: biggest cities without power Still unsure?