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A black hole is a region of spacetime where gravity is so strong that nothing, including light or other electromagnetic waves, has enough energy to escape its event horizon. The theory of general relativity predicts that a sufficiently compact mass can deform spacetime to form a black hole. The boundary of no escape is called the event horizon. Although it has a great effect on the fate and circumstances of an object crossing it, it has no locally detectable features according to general relativity. In many ways, a black hole acts like an ideal black body, as it reflects no light. Moreover, quantum field theory in curved spacetime predicts that event horizons emit Hawking radiation, with the same spectrum as a black body of a temperature inversely proportional to its mass. This temperature is of the order of billionths of a kelvin for stellar black holes, making it essentially impossible to observe directly.
General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of second order partial differential equations.
The theory of relativity usually encompasses two interrelated theories by Albert Einstein: special relativity and general relativity, proposed and published in 1905 and 1915, respectively. Special relativity applies to all physical phenomena in the absence of gravity. General relativity explains the law of gravitation and its relation to the forces of nature. It applies to the cosmological and astrophysical realm, including astronomy.
In physics, gravity (from Latin gravitas 'weight') is a fundamental interaction which causes mutual attraction between all things with mass or energy. Gravity is, by far, the weakest of the four fundamental interactions, approximately 1038 times weaker than the strong interaction, 1036 times weaker than the electromagnetic force and 1029 times weaker than the weak interaction. As a result, it has no significant influence at the level of subatomic particles. However, gravity is the most significant interaction between objects at the macroscopic scale, and it determines the motion of planets, stars, galaxies, and even light.
A gravitational singularity, spacetime singularity or simply singularity is a condition in which gravity is so intense that spacetime itself breaks down catastrophically. As such, a singularity is by definition no longer part of the regular spacetime and cannot be determined by "where" or "when". Gravitational singularities exist at a junction between general relativity and quantum mechanics; therefore, the properties of the singularity cannot be described without an established theory of quantum gravity. Trying to find a complete and precise definition of singularities in the theory of general relativity, the current best theory of gravity, remains a difficult problem. A singularity in general relativity can be defined by the scalar invariant curvature becoming infinite or, better, by a geodesic being incomplete.
A Brief History of Time: From the Big Bang to Black Holes is a book on theoretical cosmology by English physicist Stephen Hawking. It was first published in 1988. Hawking wrote the book for readers who had no prior knowledge of physics.
The Schwarzschild radius or the gravitational radius is a physical parameter in the Schwarzschild solution to Einstein's field equations that corresponds to the radius defining the event horizon of a Schwarzschild black hole. It is a characteristic radius associated with any quantity of mass. The Schwarzschild radius was named after the German astronomer Karl Schwarzschild, who calculated this exact solution for the theory of general relativity in 1916.
John Michell was an English natural philosopher and clergyman who provided pioneering insights into a wide range of scientific fields including astronomy, geology, optics, and gravitation. Considered "one of the greatest unsung scientists of all time", he is the first person known to have proposed the existence of black holes, and the first to have suggested that earthquakes travelled in (seismic) waves. Recognizing that double stars were a product of mutual gravitation, he was the first to apply statistics to the study of the cosmos. He invented an apparatus to measure the mass of the Earth, and explained how to manufacture an artificial magnet. He has been called the father both of seismology and of magnetometry.
General relativity is a theory of gravitation developed by Albert Einstein between 1907 and 1915. The theory of general relativity says that the observed gravitational effect between masses results from their warping of spacetime.
Neil deGrasse Tyson is an American astrophysicist, author, and science communicator. Tyson studied at Harvard University, the University of Texas at Austin, and Columbia University. From 1991 to 1994, he was a postdoctoral research associate at Princeton University. In 1994, he joined the Hayden Planetarium as a staff scientist and the Princeton faculty as a visiting research scientist and lecturer. In 1996, he became director of the planetarium and oversaw its $210 million reconstruction project, which was completed in 2000. Since 1996, he has been the director of the Hayden Planetarium at the Rose Center for Earth and Space in New York City. The center is part of the American Museum of Natural History, where Tyson founded the Department of Astrophysics in 1997 and has been a research associate in the department since 2003.
Gravitational waves are waves of the intensity of gravity generated by the accelerated masses of an orbital binary system that propagate as waves outward from their source at the speed of light. They were first proposed by Oliver Heaviside in 1893 and then later by Henri Poincaré in 1905 as waves similar to electromagnetic waves but the gravitational equivalent. Gravitational waves were later predicted in 1916 by Albert Einstein on the basis of his general theory of relativity as ripples in spacetime. Later he refused to accept gravitational waves. Gravitational waves transport energy as gravitational radiation, a form of radiant energy similar to electromagnetic radiation. Newton's law of universal gravitation, part of classical mechanics, does not provide for their existence, since that law is predicated on the assumption that physical interactions propagate instantaneously – showing one of the ways the methods of Newtonian physics are unable to explain phenomena associated with relativity.
The following outline is provided as an overview of and topical guide to black holes:
In astrophysics, an event horizon is a boundary beyond which events cannot affect an observer. Wolfgang Rindler coined the term in the 1950s.
Wonders of the Universe is a 2011 television series produced by the BBC, Discovery Channel, and Science Channel, hosted by physicist Professor Brian Cox. Wonders of the Universe was first broadcast in the United Kingdom on BBC Two from 6 March 2011. The series comprises four episodes, each of which focuses on an aspect of the universe and features a 'wonder' relevant to the theme. It follows on from Cox's 2010 series for the BBC, Wonders of the Solar System. An accompanying book with the same title was also published.
Cosmos: A Spacetime Odyssey is a 2014 American science documentary television series. The show is a follow-up to the 1980 television series Cosmos: A Personal Voyage, which was presented by Carl Sagan on the Public Broadcasting Service and is considered a milestone for scientific documentaries. This series was developed to bring back the foundation of science to network television at the height of other scientific-based television series and films. The show is presented by astrophysicist Neil deGrasse Tyson, who, as a young high school student, was inspired by Sagan. Among the executive producers are Seth MacFarlane, whose financial investment was instrumental in bringing the show to broadcast television, and Ann Druyan, a co-author and co-creator of the original television series and Sagan's wife. The show is produced by Brannon Braga, and Alan Silvestri composed the backing score.
"Hiding in the Light" is the fifth episode of the American documentary television series Cosmos: A Spacetime Odyssey. It premiered on April 6, 2014 on Fox and aired on April 7, 2014 on National Geographic Channel. The episode explores properties of light, cameras, the scientific method, and the composition of the universe. The episode includes a look at the contributions of the 10th century physicist Ibn al-Haytham, described as the "father of the modern scientific method".
"Deeper, Deeper, Deeper Still" is the sixth episode of the American documentary television series Cosmos: A Spacetime Odyssey. It premiered on April 13, 2014 on Fox and aired on April 14, 2014 on National Geographic Channel. The episode explores the smallest particles in the universe, where host Neil deGrasse Tyson "hunts for elusive neutrinos and the distant, early universe." The episode features the underground neutrino laboratory, Super-Kamiokande, located underneath Mount Kamioka in Japan.
"Sisters of the Sun" is the eighth episode of the American documentary television series Cosmos: A Spacetime Odyssey. It premiered on April 27, 2014, on Fox, and aired on April 28, 2014, on National Geographic Channel. The episode explores the violent cosmic phenomenon of supernovas, which on average occur once per galaxy per century or one billion times per year in the observable universe. The episode pays homage to the discoveries of two female astronomers, Cecilia Payne and Annie Jump Cannon, and the obstacles faced by women scientists, especially those working in the early 20th century. Payne discovered the chemical composition of stars and that they consist largely of hydrogen. Cannon developed the first catalog for the spectral characteristics of stars. The episode's title refers to the scientific contributions of the women scientists featured in the episode as well as how their discoveries helped advance our knowledge of the composition of stars.
"The Electric Boy" is the tenth episode of the American documentary television series Cosmos: A Spacetime Odyssey. It premiered on May 11, 2014 on Fox, and aired on May 12, 2014 on National Geographic Channel. The episode was directed by Bill Pope, and written by Ann Druyan and Steven Soter. The episode explores the Earth's magnetic field and the contributions of Michael Faraday, which paved the way for high technology and light-speed communication.
The first direct observation of gravitational waves was made on 14 September 2015 and was announced by the LIGO and Virgo collaborations on 11 February 2016. Previously, gravitational waves had been inferred only indirectly, via their effect on the timing of pulsars in binary star systems. The waveform, detected by both LIGO observatories, matched the predictions of general relativity for a gravitational wave emanating from the inward spiral and merger of a pair of black holes of around 36 and 29 solar masses and the subsequent "ringdown" of the single resulting black hole. The signal was named GW150914. It was also the first observation of a binary black hole merger, demonstrating both the existence of binary stellar-mass black hole systems and the fact that such mergers could occur within the current age of the universe.
References
- ↑ Poladian, Charles (March 30, 2014). "'Cosmos' Episode 4 Preview: 'A Sky Full Of Ghosts' Trailers Highlight Time, Light, Gravity And Patrick Stewart". IB Times. Retrieved March 31, 2014.
- ↑ "In-Depth Preview of "Cosmos: A Spacetime Odyssey" --The Discovery of Black Holes (Episode 4)". The Daily Galaxy. The Daily Galaxy. March 28, 2014. Archived from the original on March 31, 2014. Retrieved March 31, 2014.
- ↑ Kaminski, Jeff (March 31, 2014). "'Cosmos' Review: 'A Sky Full of Ghosts'". Geeksmash.com. Archived from the original on March 31, 2014. Retrieved March 31, 2014.
- ↑ Brown, Laurel. "'Cosmos' episode 4: Speed, size and black holes in 'A Sky Full of Ghosts'". Zap2It. Zap2It. Archived from the original on March 31, 2014. Retrieved March 31, 2014.
- 1 2 Bibel, Sara (April 1, 2014). "Sunday Final Ratings: 'The Good Wife', 'Resurrection', 'Crisis', '60 Minutes' & 'America's Funniest Home Videos' Adjusted Up; 'The Mentalist' Adjusted Down". TV by the Numbers. Archived from the original on April 4, 2014. Retrieved April 1, 2014.