Geometry.Net - Basic_B: Black Holes

Www.askeric.org/Projects/Newton/11/blckhole.html
Similar pages Space News and talk to the world! New Theories Dispute the Existence of black holesJanuary 17, 2002 0800 CDT. Two US scientists have questioned
http://www.askeric.org/Projects/Newton/11/blckhole.html
PhysicsWeb - Galactic Lenses Cut Black Holes Down To Size
Galactic lenses cut black holes down to size 26 June 2002. The abundanceof primordial 'supermassive' black holes several billion
http://physicsweb.org/article/news/6/6/16

Extractions: 26 June 2002 The abundance of primordial 'supermassive' black holes - several billion times more massive than the Sun - could have been greatly overestimated, according to Stuart Wyithe and Abraham Loeb of Harvard University in the US. Wyithe and Loeb have calculated that the light emitted by certain quasars - the brightness of which is linked to the size of their parent black holes - has been greatly amplified by gravitational lenses. The claim could boost models of the early Universe, which predict a more modest number of supermassive black holes than some studies have suggested (J Wyithe and A Loeb 2002 Nature Quasars are the brightest objects in the Universe, and exist at the cores of active galaxies. As particles of gas and dust are sucked into the black hole at the centre of the galaxy, they release their gravitational energy as light, and this makes the quasar shine. Previous studies of remote, bright quasars have suggested that supermassive black holes were common in the early Universe. But existing models cannot explain how so much matter was formed at such an early stage in the development of the Universe. Now Wyithe and Loeb have studied the luminosity of four very bright quasars recently discovered by the Sloan Digital Sky Survey. The quasars have large 'redshifts', which means that they are extremely remote and emitted their light when the Universe was very young. The researchers say that the light from them could have been amplified at least ten times by intervening galaxies acting as 'gravitational lenses'.
PhysicsWeb - Supermassive Black Holes
Supermassive black holes Feature June 2002. Of all the legacies of Einstein'sgeneral theory of relativity, none is more fascinating than black holes.
http://physicsweb.org/article/world/15/6/9

Extractions: Feature: June 2002 Astronomers have confirmed that black holes weighing billions of solar masses lie at the heart of every galaxy and believe that some galaxies might contain pairs of black holes. Of all the legacies of Einstein's general theory of relativity, none is more fascinating than black holes. While we now almost take their existence for granted, for much of the 20th century black holes were viewed as mathematical curiosities with no counterparts in nature. Einstein himself never believed in black holes and wrote two papers in which he argued against their existence. Einstein's resistance to the idea is understandable. Like most physicists of his day, he found it hard to believe that nature could permit the formation of objects as extreme as black holes. Indeed, the gravitational fields of black holes are strong enough to prevent light from escaping, and even distort space and the flow of time around them. The modern view - that black holes are the unavoidable end result of the evolution of massive stars - arose from the theoretical work of Subrahmanyan Chandrasekhar, Lev Landau, Robert Oppenheimer and others in the first half of the 20th century. However, it was not until the discovery in 1963 of extremely luminous distant objects called quasars that the existence of black holes was generally acknowledged. What is more, black holes appeared to exist on a scale far larger than anyone had anticipated.
New Evidence For Black Holes
New Evidence for black holes. By seeing almost nothing, astronomers say they've discoveredsomething extraordinary the event horizons of black holes in space.
http://science.nasa.gov/headlines/y2001/ast12jan_1.htm

Extractions: NASA Science News home Listen to this story (requires RealPlayer January 12, 2001 NASA's two Great Observatories, the Hubble Space Telescope and the Chandra X-ray Observatory, have independently provided what could be the best direct evidence yet for the existence of an event horizon, the defining feature of a black hole and one of the most bizarre astrophysical concepts in nature. An event horizon is the theorized "one-way ticket" boundary around a black hole from which nothing, not even light, can escape. No object except for a black hole can have an event horizon, so evidence for its existence offers resounding proof of black holes in space. Right: Gravity draws gas from a companion star onto a black hole in a swirling pattern. As the gas nears the event horizon, a strong gravitational red shift makes it appear redder and dimmer. When the gas finally crosses the event horizon, it disappears from view; the region within the event horizon appears black. Click on the image for a side-by-side comparison with gas falling onto a neutron star.
Massive Black Holes Information Center - VLBI Imaging
VLBI imaging of galaxies with detected black holes. NGC 3894 galaxy.Next page Other galaxies with detected massive black holes.
http://arise.jpl.nasa.gov/arise/infocenter/info-center.html

Extractions: Massive black holes are thought to power most active galactic nuclei. The highest resolution images of the regions surrounding these black holes are made using VLBI. In some objects, orbital speeds within a light year of the black hole can thus be measured to "weigh" the black hole. In many other objects, the relativistic jets of plasma powered by the black hole are imaged in the central light year, helping determine the physics of the accretion onto the black hole. Only VLBI can image these regions; space VLBI missions such as ARISE will give yet higher resolution, probing ever closer to the most extreme power sources in the universe. (optional: click here to see this page with animated title) This page: VLBI imaging of galaxies with detected black holes. Next page: Other galaxies with detected massive black holes. VLBI imaging of galaxies with detected black holes Note: The images on the left and center are the best available of the massive black hole region and the host galaxies are on the right. Galaxy NGC 4258 (M106) VLBA observations show a disk of dense material is orbiting within the nucleus of the NGC 4258 galaxy at velocities up to 650 miles per second. The Very Long Baseline Array allowed precise measurements of the rotation of the material in the disk, which provides some of the most direct and definitive evidence to date for the presence of a supermassive black hole in the center of another galaxy.
X-ray Data Reveal Black Holes Galore: Science News Online, Jan. 15, 2000
Chandra has identified the origin of high-energy X-ray background and found that galactic black holes Category Science Astronomy Observatories X-ray new Xray telescope, astronomers have identified the origin of the high-energypart of the X-ray background and found that supermassive black holes at the
http://www.sciencenews.org/20000115/fob1.asp

Extractions: Week of Jan. 15, 2000; Vol. 157, No. 3 Ron Cowen Viewed in visible light, the sky appears as a dark expanse, adorned with the twinkling lights of faraway stars. But with an X-ray telescope, the sky seems uniformly bright, bathed in a diffuse glow. For 37 years, astronomers have struggled to find the multitude of pointlike sources that combine to produce this impressionistic glow, known as the X-ray background. Although they have made progress, the limited ability of telescopes to detect X rays in fine detail has hampered their efforts. Patch of sky imaged by the Keck Telescope in visible light (black dots and disks) and by the Chandra observatory at X-ray wavelengths (numbered circles). Mushotzky, Cowie, Arnaud, Barger Using the orbiting Chandra X-Ray Observatory, a sensitive telescope launched last July (SN: 9/4/99, p. 148), researchers now report that they've pinned down the origin of the background at energies where it had remained most elusiveabove 2,000 electronvolts. The results suggest that supermassive black holes lurking at the cores of galaxies are far more common than visible-light observations have revealed. An intriguing, but much less certain, possibility is that some of the X-ray-bright objects are the signposts of the earliest galaxies to assemble in the universe.
2002 News Releases - Black Hole Mystery Mimicked By Supercomputer
Advanced supercomputers have simulated extremely powerful energy jets squirtedout by black holes, the most exotic and powerful objects in the Universe.
http://www.jpl.nasa.gov/releases/2002/release_2002_21.html

Extractions: More images Advanced supercomputers have simulated extremely powerful energy jets squirted out by black holes, the most exotic and powerful objects in the Universe. "This research helps us unlock the mysteries of rotating black holes and confirms that their rotation actually produces power output," said Dr. David Meier, an astrophysicist at NASA's Jet Propulsion Laboratory, Pasadena, Calif. Meier is co-author of a paper that will appear in the journal Science. The leader of the research team is Dr. Shinji Koide of Toyama University, Toyama, Japan. A black hole is an object so dense and powerful that nothing, not even light, can escape. A black hole gobbles up stars and other material that approaches it, including other black holes. These odd objects form in one of two ways - when a dying star collapses, or when many stars and black holes collapse together in the center of a galaxy, like our Milky Way. Both types of black holes can rotate very rapidly, dragging along the space around them. When more material falls in, it swirls and struggles wildly before being swallowed. Astronomers have witnessed this violence, including the ejection of jets, with radio and X-ray observations, but they are not able to see a black hole itself.
JPL Images And Videos - Black Holes
Images by category Earth Solar System Stars Galaxies black holes Stars GalaxiesNebulae and Other Objects New Planets JPL's Camera on Hubble Technology
http://www.jpl.nasa.gov/images/blackholes/
Physics Central Physics In Action - Black Holes
History of black holes The existence of black holes was predicted well before the20th century. When a star dies. Seeing black holes. Exploring the universe.
http://www.physicscentral.com/action/action-01-2.html

Extractions: In Physics in Action we take you to a frontier area of physics every week. After a short introduction to the basic physics involved, we give you a taste of the current reseach in the field. matters of state gravity waves far out planets whole grains ... physics in action archives What Happens to a Star When It Dies A star exists in a delicate balance between the crushing force of gravity, on the one hand, and the push of incredibly hot gases on the other. This balance exists as long as there is fuel for the fusion process that powers the star. What happens when the star runs out of fuel? Then, gravity collapses the star. The more massive the star, the more drastic the collapse and the more condensed the remaining object. a star about the size of the sun:
X-ray Data Reveal Black Holes Galore: Science News Online, Jan. 15, 2000
Chandra has identified the origin of highenergy X-ray background and found that galactic black holes are far more numerous than visible-light surveys indicate.
http://sciencenews.org/20000115/fob1.asp

Extractions: Week of Jan. 15, 2000; Vol. 157, No. 3 Ron Cowen Viewed in visible light, the sky appears as a dark expanse, adorned with the twinkling lights of faraway stars. But with an X-ray telescope, the sky seems uniformly bright, bathed in a diffuse glow. For 37 years, astronomers have struggled to find the multitude of pointlike sources that combine to produce this impressionistic glow, known as the X-ray background. Although they have made progress, the limited ability of telescopes to detect X rays in fine detail has hampered their efforts. Patch of sky imaged by the Keck Telescope in visible light (black dots and disks) and by the Chandra observatory at X-ray wavelengths (numbered circles). Mushotzky, Cowie, Arnaud, Barger Using the orbiting Chandra X-Ray Observatory, a sensitive telescope launched last July (SN: 9/4/99, p. 148), researchers now report that they've pinned down the origin of the background at energies where it had remained most elusiveabove 2,000 electronvolts. The results suggest that supermassive black holes lurking at the cores of galaxies are far more common than visible-light observations have revealed. An intriguing, but much less certain, possibility is that some of the X-ray-bright objects are the signposts of the earliest galaxies to assemble in the universe.
A Short Course On General Relativity
A graduate level course which includes weak field theory, gravitational waves, radiation damping, cosmology, the Friedmann and Lemaitre dusts, singularities, black holes, the Schwarzschild metric and Kruskal's extension of it. This is a single postscript document.
http://www.ucolick.org/~burke/class/grclass.ps
Black Holes Made Simple
An overview of modern research in black holes without the use of mathematical equations.
http://www.geocities.com/autotheist/Physics/bh.htm

Extractions: The Schwarzschild Solution Shortly after Einstein developed the general theory of relativity , Karl Schwarzschild found a solution for the equations of general relativity in empty space. He started by assuming only that the solution was SPHERICALLY SYMMETRIC. This means that no matter how the system is rotated about its center, it remains the same. He then applied the required mathematical conditions to general relativity, and came up with a solution that approximates the behaviour of planets around the sun. In fact, one of the first tests of general relativity was the prediction of the motion of Mercury using the Schwarzschild solution. Another benefit of the solution is that it is static. This means that a star can pulse and evolve in any spherically symmetric way, and there is no way of measuring the effect on gravity. Unfortunately, there is a problem with the Schwarzschild solution. When the distance from the center of the system is equal to a constant multiplied by the total mass of the body, the Schwarzschild metric (recall that this is the function used to measure distance in general relativity) becomes infinite, and has no time dependence. Although it cannot be proved here, this corresponds to light being trapped at this distance. Even worse, when the distance is smaller, time and space swap properties, so that ordinary distance acts like time and time acts like distance.
New Observations Of Black Holes Confirm General Relativity
Satellite observations of black holes confirm framedragging effect 80years after prediction. Learn More about Spinning black holes!!!
http://science.msfc.nasa.gov/newhome/headlines/ast06nov97_1.htm

Extractions: November 6, 1997: T he next time you feel like you're barely dragging along, blame relativity. You'll be stretching the point, but it appears that Einstein was right: space and time get pulled out of shape near a rotating body. Einstein predicted the effect, called ``frame dragging,'' 80 years ago. Like many other aspects of Einstein's famous theories of relativity, it's so subtle that no conventional method could measure it. Using recent observations by X-ray astronomy satellites, including NASA's Rossi X-ray Timing Explorer , a team of astronomers is announcing that they see evidence of frame dragging in disks of gas swirling around a black hole. The discovery will be announced today at a meeting of the High Energy Astrophysics Division of the American Astronomical Society in Estes Park, Colo., by Dr. Wei Cui of the Massachusetts Institute of Technology, and his colleagues, Dr. Nan Zhang
Time Travel! Seriously!
Paradox, black holes and wormholes.
http://www.geocities.com/mistress_baka/blackholes/timetravel.html

Extractions: Time Travel! Seriously! But here's the catch. Time travel has consequences when not used correctly. Take the famous Grandmother Paradox. A mad scientist SOMEHOW creates a wormhole that takes him back to the time when his grandmother was 14. Without realizing it's his grandmother, he accidentally drops a flower pot on her head and she dies. If she's dead, she will not give birth to the mad scientist's mother and in turn, his mother won't give birth to him. But if he's not born, he can't go back in time to kill his grandmother. So she lives, gives birth to his mother, his mother gives birth to him, and he does go back in time and kill his grandmother... See? Very confusing stuff! Back
Black Holes To Blackboards - Sep/Oct '98
Building Universes in the ClassroomOur national education standards ask all science teachers to teach Category Science Astronomy Educationblack holes to Blackboards Building Universes in the Classroom.
http://www.aspsky.org/mercury/mercury/9805/lockwood.html

Extractions: Tucson Unified School District Our national education standards ask all science teachers to teach our students using an inquiry-based approach, allowing them to understand the nature of science by doing it. Each of the programs I describe here satisfies not only those standards but also the curiosity of our students as they travel into the science world as neophyte scientists, struggling with the evidence, moving steadily towards a real understanding of science and the process of discovery. Buying the Moon A gentleman walked into my classroom last spring and offered me a 150 kilometer square section of the Moon. That's about 5.4 million acres, and with an asking price of $500, it's quite a bargain at 108 acres per cent. But instead of delivering a title and map for my 500 bucks, George French, president of Space Explorers, Inc., offered real scientific data to analyze from the Lunar Orbiter satellite. George has a license from NASA to make Lunar Orbiter data available to our nations' classrooms. Called Project Moonlink ( moonlink@space-explorers.com
The Light Cone: The Schwarzschild Black Hole
A site explaining the Schwarzschild solution and how it leads to black holes.Category Science Physics Relativity black holes Here is a nice VRML visualization Geometry Around black holes Curvatureand Lightcones of the geometry of the Schwarzschild black hole.
http://physics.syr.edu/courses/modules/LIGHTCONE/schwarzschild.html

Extractions: Just months after Einstein published his work on his Theory of Gravitation, Karl Schwarzschild (1916) found one solution to Einstein's equations: the curvature due to a massive nonrotating spherical object. That is, using Einstein's equation, Schwarzschild had determined how spacetime is curved due to the presence of a nonrotating spherical mass. In practical terms, the Schwarzschild spacetime describes the gravitational field of the Sun, or of the Earth. (The Sun and the Earth do rotate, but this rotation is negligible in these cases.) This spacetime was studied carefully, and it led to a few physical predictions. Firstly, it did as good a job as Newton's Theory of Gravity in explaining the motion of the planets around the sun. Second, it accounted for a tiny effect concerning the path of the planets ("The Anomalous Advance of the Perihelion") that Newton's Theory was unable to completely account for. The orbit of Mercury was studied, and the prediction was confirmed. Thirdly, it predicted a value for a tiny effect concerning the path of light-rays ("The Bending of Starlight") that Newton's Theory was unable to completely account for. Light from a star passing near the sun was studied. The Einstein Theory correctly predicted the amount of the deflection of starlight. (For practical purposes, one could only make the observation during a solar eclipse since sunlight was much brighter than the starlight to be studied.)
BBCi - Space - Time Travel
Gravity, black holes, singularity and mini wormholes.
http://www.bbc.co.uk/science/space/exploration/timetravel/index.shtml

Extractions: by Neil Johnson The idea of travelling forward into the future or back into the past has always fascinated science fiction writers. The 'grandfather paradox' is the argument many people use to suggest that time travel is impossible. What if you went back in time and prevented your grandfather from meeting your grandmother so that your mother was never born? Then you would never have been born... and so on. Until very recently such arguments led most scientists to believe that time travel could never exist outside science fiction. But amazingly, some interpretations of the weirdness of the quantum world now suggest that time travel is possible - at least in theory. Gravity and black holes Einstein's theory of relativity brought space and time together in a single, four-dimensional arrangement that he called spacetime. We know that we can travel forwards, backwards and sideways in space, so why not forwards and backwards in time? Four dimensions are difficult to imagine, so physicists usually suggest you think of spacetime as a rubber sheet stretched out flat. If there are no large masses around, the sheet stays flat, and so any object placed on it will move around in straight lines. But a large mass, such as the
1st SPOT Cosmology
References to cosmological sites featuring indepth coverage of issues like dark matter, black holes and symmetric theory.
http://1st-spot.freeservers.com/topic_cosmology.html
Black Holes
Properties of black holes, What is a black hole like? Quantum mechanics turnsblack holes from cold, eternal objects into hot shrinking thermodynamics.
http://superstringtheory.com/blackh/

Extractions: What would happen if gravity were so strong that even light could not escape its pull? The answer to this question is the shocking and amazing object known as the black hole. basic advanced What is a black hole like? How were they first discovered? How do astronomers know if they're seeing one? basic advanced Quantum mechanics turns black holes from cold, eternal objects into hot shrinking thermodynamics. Physicists wondered: Is there a microscopic origin for black hole entropy? basic advanced Find out how and why string theory modifies the spacetime equations of Einstein.
[gr-qc/9803002] Higher Dimensional Chern-Simons Theories And Topological Black H
It has been recently pointed out that black holes of constant curvature with a chronological singularity can be constructed in any spacetime dimension. In this paper, a brief summary of these new black holes is given.
http://xxx.lanl.gov/abs/gr-qc/9803002

Extractions: It has been recently pointed out that black holes of constant curvature with a "chronological singularity" can be constructed in any spacetime dimension. These black holes share many common properties with the 2+1 black hole. In this contribution we give a brief summary of these new black holes and consider them as solutions of a Chern-Simons gravity theory. We also provide a brief introduction to some aspects of higher dimensional Chern-Simons theories. References and citations for this submission:

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