ASP: Black Holes To Blackboards: God Divided By Zero Laying your hands on a black hole is hard (and dangerous) to do, but there are ways to understand these objects and avoid the pain of dimensionbending. http://128.241.173.3/pubs/mercury/9802/lockwood.html
Extractions: Sahuaro High School Laying your hands on a black hole is hard (and dangerous) to do, but there are ways to understand these objects and avoid the pain of dimension-bending. A couple of weeks ago, I was sitting in the second-floor bathroom at Steward Observatory, not thinking at all about astronomy or writing columns. On the stall door in front of me, written perhaps by a clever astronomy student, was an equation in bold black ink: BLACK HOLES = GOD/0. As I pondered the philosophical significance of the equation, I realized that I have never tried to bring black holes to blackboards as my column title states. One of the most esoteric and fascinating objects for students to ponder, a black hole comes with virtually no lab activities. How do you lay your hands on a black hole and survive? There are, in fact, a few demonstrations that can bring about some understanding of black holes. It's pretty easy to describe a non-rotating black hole: a single point of infinite density surrounded by a protective sheath called the event horizon. Throw in rotation, though, and things get more complicated. I have never liked the funnel-like diagrams in most textbooks that try to show a black hole's distortion of space-time. A sharp student will always question this representation, which shows a 3-dimensional warpage, and ask what happens when you approach from a different direction, like from "underneath."
Extractions: Our Sponsors Coupons advertising network Cheap Premium Tickets Philadelphia Eagles Tickets ... The Odd Couple Tickets A black hole is an (almost invisble) body in space, created most likely from a collapsed red super giant star, that is so dense that neither light nor matter can escape its gravitational pull. Inside a star there is a constant battle between inward pressure from gravity, and outward pressure from heat. If you were to throw an unopened can of soda into a fire, the beverage would expand from the heat and explode. This is the same principle at work when a star is burning, it's heat is generating great outward pressure but this constant explosion is matched by gravity that is equally strong, thus a star maintains its shape and size. When a star nears the end of its life it cools off slowly and the outwards pressure grows weaker and weaker as the temperature of the star drops. When the outward pressure from the heat is nearly gone, the inward pressure of gravity still remains and is determined by the size of the star. It is theorized that when a star roughly ten times the size of our own nears the end of its life, it shrinks as its own gravity slowly pulls it in, but as it becomes more and more dense the gravity becomes stronger. The gravity becomes so intense that not even light can escape it. If you have ever watched water swirling down a drain, then you have a pretty good idea what happens as a black hole pulls things in. As matter and light approach the vicinity of a black hole they are slowly drawn in. If they are not headed straight for the spacial anomaly then they are taken into a violent and unstable orbit around the black hole until finally the orbit falls apart and it is sucked down by the immense gravity.
2001: A Spacetime Odyssey Two theories revolutionized the 20th century view of space and time Einstein's General Theory of Relativity and Quantum Mechanics. Their union has spawned elementary particle theories with extra spacetime dimensions, the inflationary model of bigbang cosmology, dark matter in the universe, radiation from quantum black holes and the fuzzy spacetime geometry of superstrings and M-theory. http://www.umich.edu/~mctp/sto2001/
Extractions: University of Michigan, Ann Arbor Two theories revolutionized the 20th century view of space and time: Einstein's General Theory of Relativity and Quantum Mechanics. Their union has spawned elementary particle theories with extra spacetime dimensions, the inflationary model of big-bang cosmology, dark matter in the universe, radiation from quantum black holes and the fuzzy spacetime geometry of superstrings and M-theory. These developments, derived from the 19th century mathematics of Riemannian geometry and Lie groups, have in their turn inspired new directions in the pure mathematics of topology and knot theory. In view of the mission of the Michigan Center for Theoretical Physics to provide a venue for interdisciplinary studies in the mathematical sciences, this Inaugural Conference will bring together Astronomers, Cosmologists, Particle Physicists and Mathematicians to share their different perspectives on the 21st century view of spacetime. John Bahcall (IAS)
Black Holes: Fact And Fiction 1100, Roger Blandford (Caltech), New horizons in black hole astrophysics. 12 Noon, Jim Lochner (NASA/GSFC), Building a Black Hole in Your Classroom http://online.itp.ucsb.edu/online/bh_teach/
Extractions: home activities inside KITP directory ... UCSB Sep 19, 2005 INSTITUTE FOR THEORETICAL PHYSICS ITP Teachers Educational Forum on Black Holes: Fact and Fiction Saturday, February 6, 1999 Coordinators: O. Blaes. R. Blandford, D. Eardley and J.P. Lasota Schedule Time: Speaker: Title: 8:00 am Registration ITP Lobby 9:00 am David Gross Welcome to Conference 9:30 am Kip Thorne (Caltech) Black Holes: Predicted Properties and Behaviors Refreshment Break ITP Courtyard Roger Blandford (Caltech) New horizons in black hole astrophysics 12 Noon Jim Lochner (NASA/GSFC) Building a Black Hole in Your Classroom Lunch Break ITP Courtyard 1:45 pm Joe Polchinski (ITP) What is String Theory and What Does It Have to Do With Black Holes? 2:45 pm Town Hall
Laser Stars - Quasars Quasars are not black holes, they are laser stars within our galaxy. http://laserstars.org/glossary/quasar.html
Extractions: In the early 1960's quasars were known as 'radio stars' because the method used to discover the first quasars was based on coincidences between a strong radio source and a point-like optical source. Since each radio source was associated with a star it was originally thought that quasars were objects within the galaxy hence the term 'radio stars' Quasars or quasi-stellar radio source, from the method by which they where originally discovered : as stellar optical counterparts to small regions of strong radio emission. With increasing spatial resolution of radio telescopes the strong radio emission often seemed to come from a pair of lobes surrounding many of these faint star-like emission line objects. The method initial method of selection was strong radio emission, then later any object with blue or ultraviolet excess was considered a good quasar candidate. Very recent evidence from the near infrared portion of the spectrum indicates that a large fraction of quasars may in fact be brighter in the infrared than in other wavelength bands. Unfortunately, due to an error in spectral identification made by Maarten Schmidt (1963) these quasars were incorrectly classified as extra-galactic objects. In order to distance themselves from the term
Lives And Deaths Of Stars black holes have been portrayed as cosmic vacuum cleaners in Hollywood films, black holes are dangerous only if something gets too close to them. http://www.astronomynotes.com/evolutn/s13.htm
Extractions: This material (including images) is . See my for fair use practices. If the core remnant has a mass greater than 3 solar masses, then not even the super-compressed degenerate neutrons can hold the core up against its own gravity. Gravity finally wins and compresses everything to a mathematical point at the center. The point mass is a black hole . Only the most massive, very rare stars (greater than 10 solar masses) will form a black hole when they die. As the core implodes it briefly makes a neutron star for just long enough to produce the supernova explosion. The gravity of the point mass is strong enough close to the center that nothing can escape, not even light! Within a certain distance of the point mass, the escape velocity is greater than the speed of light. Remember from the gravity chapter that the escape velocity is the speed an object needs to avoid being pulled back by the gravity of a massive body. The escape velocity
Newton's Apple Teacher's Guides: Black Holes CONNECTIONS. How do we know about black holes when we can t see them? What would it be like if a black hole came near Earth? http://www.ktca.org/newtons/11/blckhole.html
Extractions: Try This Suppose you go outside and throw an apple straight up into the air. The Earth's gravity slows the upward speed of the apple until it finally stopsand then starts falling back down. But suppose you could throw the apple so fast that Earth's gravity could never quite make it stop and fall back down. That speed is called escape velocity for Earth, the escape velocity is 25,000 miles per hour. On planets or stars with more gravity, the escape velocity would be even higher. Some planets and stars have the same mass but different sizes. In that case, the smallest one will have the greatest gravity at its surface. Stars can change size (and gravity) very dramatically. A star's gravity works not only on objects outside the star but also among the particles that make up the star. These particles attract one another and the star would collapse if it weren't for the nuclear energy pushing outward. When the nuclear fuel runs out, there is no more energy to keep the star from collapsing into a very small and dense sphere.
Science -- Sign In Why have no black holes with intermediate masses of hundreds to tens of thousands The main alternative to intermediatemass black holes is that they are http://www.sciencemag.org/cgi/content/full/307/5709/533
Extractions: You do not have access to this item: Full Text : Fabbiano, ASTRONOMY: The Hunt for Intermediate-Mass Black Holes, Science You are on the site via Free Public Access. What content can I view with Free Public Access If you have a personal user name and password, please login below. SCIENCE Online Sign In Options For Viewing This Content User Name Password this computer. Help with Sign In If you don't use cookies, sign in here Join AAAS and subscribe to Science for free full access. Sign Up More Info Register for Free Partial Access including abstracts, summaries and special registered free full text content. Register More Info Pay per Article 24 hours for US $10.00 from your current computer Regain Access to a recent Pay per Article purchase Need More Help? Can't get past this page? Forgotten your user name or password? AAAS Members activate your FREE Subscription
Howstuffworks "How Black Holes Work" black holes are some of the most amazing objects in the universe they may even hold many galaxies together! Learn all about them! http://www.howstuffworks.com/black-hole.htm
Black Holes Simultions A series of images and simulations of various phenomena associated with a black hole. http://gravity.psu.edu/~sperhake/Research/BH_Simulations/bh_simulations.html
[hep-th/9801025] Quantum Fields Near Black Holes This review gives an introduction into problems, concepts and techniques when quantizing matter fields near black holes. The first part focusses on quantum fields in general curved spacetimes. The second part is devoted to a detailed treatment of the Unruh effect in uniformly accelerated frames and the Hawking radiation of black holes http://arxiv.org/abs/hep-th/9801025
Extractions: This review gives an introduction into problems, concepts and techniques when quantizing matter fields near black holes. The first part focusses on quantum fields in general curved space-times. The second part is devoted to a detailed treatment of the Unruh effect in uniformly accelerated frames and the Hawking radiation of black holes. Paricular emphasis is put on the induced energy momentum tensor near black holes References and citations for this submission:
Beyond The Event Horizon, BlackHols Beyond the Event Horizon An Introduction to black holes The first thing that a traveler into a Kerr black hole would discover is that he was being http://www.astronomical.org/astbook/blkhole.html
Extractions: distributed for profit Beyond the Event Horizon: An Introduction to Black Holes Imagine a world in which a beam of light rose into the sky only to fall back to the ground at your feet. Or, picture an infinite continuum of parallel universes, each inhabited by slightly different parallel twins of yourself.Visualize a place in which all the laws of physics, that combine to make our universe the place that it is, vanish into inscrutable infinities. Welcome to the world of one nature's most bizarre phenomena: the black hole. Figure 1: The Rubber Sheet Analogy of Gravity Shortly after the publication of the General Theory, physicists began to explore this strange new world. The theory is so very complex, and the mathematics so difficult, that even today, scientists have barely scratched the surface of this powerful theory. One of the very earliest solutions to the equations was developed by the German physicist, Karl Schwartzschild, in 1916. The Schwartzschild Black Hole Figure 2: Diagram of Schwarzchild Black Hole Assuming that we could find a volunteer to journey into a Schwarzchild black hole, what would he experience? Passing through the photon-sphere, he would be flooded with intense light. As our volunteer left the brightness, he would find himself in utter darkness. He would feel his velocity increase to unbelievable levels. Approaching the event horizon, our astronaut would be subjected to tidal forces of astronomical proportions. His feet would seem to weight uncounted trillions of tons more than his head. In a blinding instant, our poor volunteer would be disintegrated into atoms. He would then crash into the singularity, where his mortal remains would be summarily smashed out of existence (4).
ASP: Black Holes The Astronomical Society of the Pacific is an international nonprofit scientific and educational organization founded in 1889 that works to increase http://www.astrosociety.org/education/publications/tnl/24/24.html
Extractions: Black Holes by John Percy, University of Toronto What is a black hole? Mini black holes How can you "see'' a Black Hole? Supermassive black holes ... For Further Reading About Black Holes A black hole is a region of space in which the pull of gravity is so strong that nothing can escape. It is a "hole'' in the sense that things can fall into it, but not get out. It is "black'' in the sense that not even light can escape. Another way to say it, is that a black hole is an object for which the escape velocity (the velocity required to break free from an object) is greater than the speed of light the ultimate "speed limit'' in the universe. In 1783, British amateur astronomer, Rev. John Mitchell, realized that Newton's laws of gravity and motion implied that the more massive an object, the greater the escape velocity. If you could somehow make something 500 times bigger than the Sun, but with the same density, he reasoned, even light couldn't move fast enough to escape from it and it would never be seen. But it took Einstein's general theory of relativity, the modern theory of gravity, for astronomers and physicists to understand the true nature and characteristics of black holes. The boundary of a black hole is called the event horizon , because any event which takes place within is forever hidden to anyone watching from outside. Astronomer Karl Schwarzschild showed that the radius of the event horizon in kilometers is 3 times its mass expressed in units of solar masses; this radius is called the Schwarzschild radius. The event horizon is the one-way filter in the black hole: anything can enter, but nothing can leave.
Extractions: by Amir Alexander November 5, 2001: The SETI@home receiver at Arecibo scans the skies, searching for a signal from an alien civilization. So far no signal has been found, but SETI@home scientists are not losing hope. Searching for a signal is bound to be a long-term process, says chief scientist Dan Werthimer, and its success can only be evaluated on the time scale of generations. In the meantime, Werthimer and his colleagues are making sure that the mountains of data gathered in the search do not go to waste, and are used in shorter-term scientific projects. Most recently, astronomers have begun sifting through SETI@home's data looking for signs of "evaporating black holes." "Black holes" are those astronomical objects, predicted by Einstein's theory of relativity, whose mass and density are so great that their gravity allows nothing to escape their surface - not even light itself. As a result they are like black bottomless pits, which swallow anything in their vicinity. Stephen Hawking Until quite recently it was believed that black holes had an unlimited lifespan. "Once a black hole, always a black hole" summed up the understanding of these objects' longevity. This view changed when Stephen Hawking, the famed quadriplegic astro-physicist from Cambridge, showed that black holes do indeed expire. According to Hawking, at some point in their lifetime black holes begin to shrink, until in the end they practically evaporate in a great burst of energy.
ASP: Black Holes To Blackboards: God Divided By Zero Laying your hands on a black hole is hard (and dangerous) to do, but there are ways to understand these objects and avoid the pain of dimensionbending. http://www.astrosociety.org/pubs/mercury/9802/lockwood.html
Extractions: Sahuaro High School Laying your hands on a black hole is hard (and dangerous) to do, but there are ways to understand these objects and avoid the pain of dimension-bending. A couple of weeks ago, I was sitting in the second-floor bathroom at Steward Observatory, not thinking at all about astronomy or writing columns. On the stall door in front of me, written perhaps by a clever astronomy student, was an equation in bold black ink: BLACK HOLES = GOD/0. As I pondered the philosophical significance of the equation, I realized that I have never tried to bring black holes to blackboards as my column title states. One of the most esoteric and fascinating objects for students to ponder, a black hole comes with virtually no lab activities. How do you lay your hands on a black hole and survive? There are, in fact, a few demonstrations that can bring about some understanding of black holes. It's pretty easy to describe a non-rotating black hole: a single point of infinite density surrounded by a protective sheath called the event horizon. Throw in rotation, though, and things get more complicated. I have never liked the funnel-like diagrams in most textbooks that try to show a black hole's distortion of space-time. A sharp student will always question this representation, which shows a 3-dimensional warpage, and ask what happens when you approach from a different direction, like from "underneath."
Extractions: STScI-2005-13 Black Hole in Search of a Home A team of European astronomers has used two of the most powerful astronomical facilities ... ( more STScI-2004-19 Spitzer Leads NASA's Great Observatories to Uncover Black Holes, Other Hidden Objects in the Distant Universe Astronomers unveiled the deepest images from NASA's new Spitzer Space Telescope today, and ... ( more STScI-2004-45 New Hubble Study Reveals How Black Holes Get Their Kicks When black holes collide, look out! The "kick" from an enormous burst of gravitational ... ( more STScI-2002-30 Fast-Flying Black Hole Yields Clues to Supernova Origin A nearby black hole is hurtling like a cannonball through the disk of our galaxy. The ... ( more STScI-2002-18 Hubble Discovers Black Holes in Unexpected Places Medium-size black holes actually do exist, according to the latest findings from NASA's Hubble ... ( more STScI-2001-29 Ancient Black Hole Speeds Through Sun's Galactic Neighborhood, Devouring Companion Star
Extractions: German astronomer and physicist who developed the use of photography for measuring variable stars. He also investigated the geometrical aberrations of optical systems using ray optics by introducing a perturbation equation which he called the Seidel eikonal Schwarzschild volunteered for military service and, while on the Russian front, completed the first two exact solutions of the Einstein field equations of general relativity one in static isotropic empty space surrounding a massive body (such as a black hole ), and one inside a spherically symmetric body of constant density. Shortly after this work, Schwarzschild died of a rare metabolic disorder.
Cossc.gsfc.nasa.gov/htmltest/rjn_bht.html physics central physics in action black holesWith Physics Central, we communicate the excitement and importance of physics to everyone. We invite you to visit our site every week to find out how http://cossc.gsfc.nasa.gov/htmltest/rjn_bht.html
The Astrophysical Journal Founded in 1895 and published by the American Astronomical Society. It is devoted to recent developments, discoveries, and theories in astronomy and astrophysics. Quasars, pulsars, neutron stars, black holes, solar and stellar magnetic fields, Xrays, and interstellar matter. In addition, videos that complement specific issues are periodically available. http://www.journals.uchicago.edu/ApJ/
Wired News: Black Holes And Space Travel One possibility is that black holes may allow us to travel to very remote places in the In Burko s scheme, black holes may be doorways to wormholes, http://www.wired.com/news/technology/0,1282,58359,00.html?tw=wn_story_related
