Copyright © Philip M. Parker, INSEAD. Terms of Use.
Definition: Black Hole |
Black HoleNoun1. A region of space resulting from the collapse of a star; extremely high gravitational field. Source: WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved. |
| Domain | Definitions |
Computing | Black hole n.,vt. [common] What data (a piece of email or netnews, or a stream of TCP/IP packets) has fallen into if it disappears mysteriously between its origin and destination sites (that is, without returning a bounce message). "I think there's a black hole at foovax!" conveys suspicion that site foovax has been dropping a lot of stuff on the floor lately (see drop on the floor). The implied metaphor of email as interstellar travel is interesting in itself. Readily verbed as `blackhole': "That router is blackholing IDP packets." Compare bit bucket and see RBL. Source: Jargon File. |
Geography | Star that has collapsed beyond the theoretical limits for a neutron star; the gravitational field of these objects is so powerful that light waves cannot escape from them. Source: European Union. (references) |
Physics | A region of space that has so much mass concentrated in it that there is no way for a nearby object to escape its gravitational pull. (references) |
| An object whose gravity is so strong that not even light can escape from it. (references) | |
Space | An extremely compact object, collapsed by gravity which has overcome electric and nuclear forces. It is believed that stars appreciably larger than the Sun, once they have exhausted all their nuclear fuel, collapse to form black holes: they are "black" because no light escapes their intense gravity. Material attracted to a black hole, though, gains enormous energy and can radiate part of it before being swallowed up. Some astronomers believe that enormously massive black holes exist in the center of our galaxy and of other galaxies. (references) |
Source: compiled by the editor from various references; see credits. | |
(From Wikipedia, the free Encyclopedia)
Black holes are believed to form from the gravitational collapse of astronomical objects containing two or more solar masses. Astronomical observations suggest that the centers of most galaxies, including our own Milky Way, contain supermassive black holes containing millions to billions of solar masses.
Black holes are predictions of Einstein's theory of general relativity. In particular, they occur in the Schwarzschild metric, one of the earliest and simplest solutions to Einstein's equations, found by Karl Schwarzschild in 1915. This solution describes the curvature of spacetime in the vicinity of a static and spherically symmetric object.
According to Schwarzschild's solution, a gravitating object will collapse into a black hole if its radius is smaller than a characteristic distance, known as the Schwarzschild radius. Below this radius, spacetime is so strongly curved that any light ray emitted in this region, regardless of the direction in which it is emitted, will travel towards the center of the system. Because relativity forbids anything from travelling faster than light, anything below the Schwarzschild radius - including the constituent particles of the gravitating object - will collapse into the center. A gravitational singularity, a region of theoretically infinite density, forms at this point. Because not even light can escape from within the Schwarzschild radius, a classical black hole would truly appear black.
The Schwarzschild radius is given by
Since the mean radius of the Earth is around 6371 kilometers, the Earth would have to be compressed to a ludicrous 4 × 1026 times its current density for it to collapse into a black hole. For an object with the mass of the Sun, the Schwarzschild radius is approximately three kilometers, much smaller than the Sun's current radius of about 700,000 kilometers. It is also significantly smaller than the radius to which the Sun will ultimately shrink after exhausting its nuclear fuel, which is several thousand kilometers. More massive stars can collapse into black holes at the end of their lifetimes (see the section on "Black Hole Formation" below.)
More general black holes are also predicted by other solutions to Einstein's equations, such as the Kerr metric for a rotating black hole, which possesses a ring singularity, and the Reissner-Nordstrøm metric for charged black holes. The generalization of the Schwarzschild radius is known as the event horizon.
Black holes produce other interesting results when applied in unison with other physical theories. A commonly stated proposition is that "black holes have no hair", meaning they have no observable external characteristics that can be used to determine what they are like inside. Black holes have only three measurable characteristics: mass, angular momentum, and electric charge, and can be completely specified by these three parameters.
The entropy of black holes is a fascinating subject, and an area of active research. In 1971, Hawking showed that the total event horizon area of any collection of classical black holes can never decrease.
This sounds remarkably similar to the Second Law of Thermodynamics, with area playing the role of entropy.
Therefore, Bekenstein proposed that the entropy of a black hole really is proportionate to its horizon area. In 1975, Hawking applied quantum field theory to a semi-classical curved spacetime and discovered that black holes can emit thermal radiation, known as Hawking radiation. This allowed him to calculate the entropy, which indeed was proportionate to the area, validating Bekenstein's hypothesis. It was later discovered that black holes are maximum-entropy objects, meaning that the maximum entropy of a region of space is the entropy of the largest black hole that can fit into it. This led to the proposal of the holographic principle.
In the case of a stellar size black hole, matter can be drawn in from a companion star, producing an accretion disk and large amounts of X-rays.
Galaxy-mass black holes with 10 to 100 billion solar masses were found in Active Galactic Nuclei (AGN), using radio and X-ray astronomy. It is now believed that such supermassive black holes exist in the center of most galaxies, including our own Milky Way. Sagittarius A* is now agreed to be the most plausible candidate for the location of a supermassive black hole at the center of the Milky Way galaxy.
Black holes are also the leading candidates for energetic astronomical objects such as quasars and gamma ray bursts.
Instead of collapsing on themselves, black holes might also be created by compression of matter by extreme external pressure. Such black holes are called primordial black holes. The enormous pressures necessary for creating primordial black holes are thought to have existed in the very early stages of the universe. These black holes can have masses smaller than that of the sun.
The formation of supermassive black holes is currently matter of very active research. Though the mechanism of formation is still not clear, there is
increasing evidence that the growth of the black hole is intimately related
to the growth of the spheroidal component (elliptical galaxy, or bulge of a spiral galaxy) in which it lives.
See also:
Theoretical Consequences
Black holes demonstrate some counter-intuitive properties of general relativity. Consider a hapless astronaut falling radially towards the center of a Schwarzschild black hole. The closer she comes to the event horizon, the longer the photons she emits take to escape to infinity. A distant observer will see her descent slowing as she approaches the event horizon, which she never appears to reach. However, in her own frame of reference, the astronaut crosses the event horizon and reaches the singularity in a finite amount of time.Observational Evidence
There is now a great deal of observational evidence for the existence of two types of black holes:
This evidence comes not from seeing the black holes directly, but by observing the behavior of stars and other material near them.
A third proposed type of black hole, primordial black holes, have not been observed.Black Hole Formation
Black holes are created by the gravitational collapse of massive stars.
When a star exhausts its nuclear fuel, the equilibrium between gravitation and radiation pressure is disturbed, and it collapses. If the mass of the star is greater than about 3 times the mass of the sun, the collapse cannot be stopped, and a black hole is created. (See stellar evolution.)External Link
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Black hole."
| Context | Synonyms within Context (source: adapted from Roget's Thesaurus). |
Assemblage | Accumulation; (store); congeries, heap, lump, pile, rouleau, tissue, mass, pyramid; bing; drift; snowball, snowdrift; acervation, cumulation; glomeration, agglomeration; conglobation; conglomeration, conglomerate; coacervate, coacervation, coagmentation, aggregation, concentration, congestion, omnium gaterum, spicilegium, black hole of Calcutta; quantity; (greatness). |
Prison | Noun: prison, prison house; jail, gaol, cage, coop, den, cell; stronghold, fortress, keep, donjon, dungeon, Bastille, oubliette, bridewell, house of correction, hulks, tollbooth, panopticon, penitentiary, guardroom, lockup, hold; round house, watch house, station house, sponging house; station; house of detention, black hole, pen, fold, pound; inclosure; isolation (exclusion); penal settlement, penal colony; bilboes, stocks, limbo, quod; calaboose, chauki, choky, thana; workhouse. |
| Source: adapted from Roget's Thesaurus. | |
Crosswords: Black Hole |
| English words defined with "black hole": Cygnus ♦ Siraj-ud-daula. (references) |
| Specialty definitions using "black hole": active galactic nuclei, active galactic nucleus ♦ binary stars, Black Hole of Calcutta ♦ clearing hole, CORE LOADER ♦ drop on the floor ♦ event horizon ♦ Hawking temperature ♦ infinite loop ♦ neep-neep ♦ pellet powder ♦ Schwarzschild radius, shot firer, shot lighter. (references) |
| Domain | Usage | |
Screenplays | It's like kindergarten, school, university, black hole. (Peter's Friends; writing credit: Martin Bergmann and Rita Rudner.) Well, the Protector got super-accelerated coming out of the black hole, and it, like, nailed the atmosphere at Mach 15, which, you guys know, is pretty unstable, obviously, so we're gonna help Laredo guide it on the vox ultra-frequency carrier and use Roman candles for visual confirmation. (Galaxy Quest; writing credit: David Howard) If there's any justice at all, the black hole will be your grave! (The Black Hole; writing credit: Jeb Rosebrook; Bob Barbash) What are you, the black hole of basketball? (Eddie; writing credit: Steve Zacharias; Jeff Buhai) | |
Lyrics | WHEN YOU GONNA TAKE ME OUT OF THIS BLACK HOLE (Never Ever; performing artist: All Saints) | |
Movie/TV Titles | Black Hole High (2002) Paul Daniels in a Black Hole (2001) Descent Into the Black Hole (1990) Indiana Joan in the Black Hole of Mammoo (1984) The Black Hole (1979) | |
Song Titles | Black Hole Sun (performing artist: Soundgarden) | |
Source: compiled by the editor from various references; see credits. | ||
| Domain | Title | ||
Books |
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Theater & Movies | |||
Source: compiled by the editor from various references; see credits. | |||
| Thumbnail | Description & Credit | Thumbnail | Description & Credit |
 | Hubble Space Telescope's ongoing black hole hunt has bagged yet another supermassive black ...Credit: NASA. |  | Astronomers report that they have found new evidence that a black hole weighing 3 million ...Credit: NASA. |
 | Astronomers report today that they have found intriguing evidence that a black hole weighing ...Credit: NASA. |  | Astronomers have seen the exhaust products of black hole "engines": narrow beams of material ...Credit: NASA. |
 | Confirming the presence of yet another super-massive black hole in the universe, astronomers ...Credit: NASA. |  | A nearby black hole is hurtling like a cannonball through the disk of our galaxy. The ...Credit: NASA. |
 | Black hole candidate in the spiral galaxy M87. (Produced with the Wide-Field Planetary Camera 2, Hubble Space Telescope.).Credit: NASA. |  | Black hole at the center of a galaxy. (NGC 4438).Credit: NASA. |
Source: compiled by the editor from various references; see credits. | |||
| Play | Caption |
 | Clink; jail; prison; behind bars; locked up; lock up; lock down; incarceration; incarcerated; Bastille; big cage; big house; big school; black hole; booby hatch; brig; bull pen; caboose; cage; calaboose; can; cell; cooler; coop; county hotel; death house. |
| Source: compiled by the editor from various references; see credits. | |
| Title | Author | Quote |
Young Zaphod Plays It Safe | Douglas Adams | exclaimed both of Zaphod's heads in chorus. "So safe that you have to build a zarking fortress ship to take the by-products to the nearest black hole and tip them in! |
Les Miserables | Hugo, Victor | About the point where the ladder ended, a sort of black hole could be distinguished in the belly of the colossus. |
Grapes of Wrath | Steinbeck, John | Then Pa took the shovel, half filled it with dirt, and spread it gently into the black hole. |
Source: compiled by the editor from various references. | ||
Expression using "black hole": Black Hole of Calcutta. Additional references. | |
| Source: compiled by the editor from various references; see credits. |
| The following statistics estimate the number of searches per day across the major English-language search engines as identified by various trade publications. Hyperlinks lead to commercial use of the expression at Amazon.com. |
| Language | Translations for "black hole"; alternative meanings/domain in parentheses. | ||||||||||||||||||||||||||||||||||
Bulgarian | черна дупка, карцер. (various references) | ||||||||||||||||||||||||||||||||||
Czech | èerná díra. (various references) | ||||||||||||||||||||||||||||||||||
Danish | sort hul. (various references) | ||||||||||||||||||||||||||||||||||
Dutch | zwart gat. (various references) | ||||||||||||||||||||||||||||||||||
French | trou noir. (various references) | ||||||||||||||||||||||||||||||||||
German | schwarzes Loch. (various references) | ||||||||||||||||||||||||||||||||||
Greek | μαύρη οπή. (various references) | ||||||||||||||||||||||||||||||||||
Hungarian | magánzárka (cell, cells), karcer, kóter, iskolai börtön. (various references) | ||||||||||||||||||||||||||||||||||
Italian | buco nero. (various references) | ||||||||||||||||||||||||||||||||||
Japanese Kanji | ブラウン管 (black, Black Africa, black box, black chamber, black coffee, black comedy, black ghetto, black humor, black journalism, black magic, black market, black Monday, black money, Black Panther, black pepper, Black Power, black shaft, black tie, blackjack, blacklist, blackout, bland, blank, blanket, blanket area, blood bank, blood elite, bra, bra cup, bracket, Brad Pitt, branch, brand, brand image, brand loyalty, brandy, brass, brass-band, brasserie, brassie, brassiere, Bratislava, bravo, Brazil, brothers, brunch, brush, brush back pitch, brushy, Brussels, cathode-ray tube). (various references) | ||||||||||||||||||||||||||||||||||
Japanese Katakana | ブラックホール . (various references) | ||||||||||||||||||||||||||||||||||
Manx | towl doo. (various references) | ||||||||||||||||||||||||||||||||||
Pig Latin | ackblay olehay buraco negro. (various references) карцер (detention house, punishment room, sweat-box). (various references) calabozo (brig, calaboose, dungeon, oubliette, prison cell), agujero negro. (various references) темниця (dungeon). (various references) nh giam của quân đội. (various references) | ||||||||||||||||||||||||||||||||||
Misspellings | |
"Black Hole" is suggested in spellcheckers for the following: blach hole, blackhole. (additional references) | |
| Source: compiled by the editor, based on several corpora (additional references). | |
Scrabble® Enable2K-Verified Anagrams | |
| Words within the letters "a-b-c-e-h-k-l-l-o" | |
-1 letter: lockable. | |
-2 letters: backhoe, bechalk, becloak, kolache. | |
-3 letters: bleach, cholla, hackle, keblah, locale. | |
-4 letters: beach, belch, black, bleak, block, bloke, boche, bohea, cable, cella, cello, chalk, chela, choke, cloak, coble, hacek, hallo, haole, hello, holla, label, leach, loach, local, obeah. | |
-5 letters: able, ache, alec, aloe, bach, back, bake, bale, balk, ball, beak, beck, bell, blae, blah. | |
| Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro. | |
Hexadecimal (or equivalents, 770AD-1900s) (references)42 6C 61 63 6B 48 6F 6C 65 |
| Leonardo da Vinci (1452-1519; backwards) (references)
|
Binary Code (1918-1938, probably earlier) (references)01000010 01101100 01100001 01100011 01101011 00100000 01001000 01101111 01101100 01100101 |
HTML Code (1990) (references)B l a c k   H o l e |
ISO 10646 (1991-1993) (references)0042 006C 0061 0063 006B 0048 006F 006C 0065 |
Encryption (beginner's substitution cypher): (references)3678676977242817871 |
| 1. Definition 2. Crosswords 3. Usage: Modern 4. Usage: Commercial | 5. Images: Photo Album 6. Sounds 7. Quotations: Fiction 8. Expressions | 9. Expressions: Internet 10. Translations: Modern 11. Derivations 12. Anagrams | 13. Orthography 14. Bibliography |
Copyright © Philip M. Parker, INSEAD. Terms of Use.
