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Discusses why scientists believe in the existence of black holes, what they are, how they are formed, and how they are detected.Tags
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Strong entry in this series. Seems like Friedrich Bessel was not only the first to use parallax to measure the distance to a star but the first to suspect the presence of a white dwarf (too small for his telescope to detect but large enough to affect the motion of it's twin, Sirius-A).
Chapter 1: White Dwarfs
Bessel's discovery, improved telescopes, estimates of the size, density, etc. of Sirius-B.
Chaper 2: Limits and Explosions
The Chandraskehar limit. This is a boundary on mass. A star that weighs more is too big to collapse to a relatively large and non-dense white dwarf. The mass must collapse the white dwarf. This limit is 1.4 * the weight of the sum, approximately.
Chapter 3: Pulsars and Neutron Stars
Zwicky and Baade speculate on the show more neutron star, where protons and electrons fuse to form neutrons, and there is no charge to keep matter from collapsing further. A neutron star's surface after it has collapsed is too hot to give off visible light, but it will give off X-rays. Pulsars pulse radio waves, sometimes very fast, but always regularly. Could they be rapidly rotating neutron stars? Seems likely.
Chapter 4: Escape Velocity and Tides
A very short chapter relating escape velocity to tides. Probably the vaguest chapter in the book.
Chapter 5: Total Collapse
Can a star collapse even further than a neutron star? Oppenheimer said yes, and the star only has to be a bit over three times larger than the sun. The Schwarzschild radius is a thing that every massive body has. It's the radius of that body when the escape velocity is exactly the speed of light. The Schwarzschild radius of the earth is about 1 cm.
Chapter 6: Finding Black Holes
Black holes by definition can not be seen. But they can still be discovered by their effects. Some are one component of a double star system. The two stars rotate about each other, but one is clearly massive and yet can not be seen. Invisible, too heavy to be a neutron star, what else could it be but a black hole? Hawking advances the idea of mini black-holes and shows that they could eventually lose their mass.
David Wool's illustrations suit the text well. show less
Chapter 1: White Dwarfs
Bessel's discovery, improved telescopes, estimates of the size, density, etc. of Sirius-B.
Chaper 2: Limits and Explosions
The Chandraskehar limit. This is a boundary on mass. A star that weighs more is too big to collapse to a relatively large and non-dense white dwarf. The mass must collapse the white dwarf. This limit is 1.4 * the weight of the sum, approximately.
Chapter 3: Pulsars and Neutron Stars
Zwicky and Baade speculate on the show more neutron star, where protons and electrons fuse to form neutrons, and there is no charge to keep matter from collapsing further. A neutron star's surface after it has collapsed is too hot to give off visible light, but it will give off X-rays. Pulsars pulse radio waves, sometimes very fast, but always regularly. Could they be rapidly rotating neutron stars? Seems likely.
Chapter 4: Escape Velocity and Tides
A very short chapter relating escape velocity to tides. Probably the vaguest chapter in the book.
Chapter 5: Total Collapse
Can a star collapse even further than a neutron star? Oppenheimer said yes, and the star only has to be a bit over three times larger than the sun. The Schwarzschild radius is a thing that every massive body has. It's the radius of that body when the escape velocity is exactly the speed of light. The Schwarzschild radius of the earth is about 1 cm.
Chapter 6: Finding Black Holes
Black holes by definition can not be seen. But they can still be discovered by their effects. Some are one component of a double star system. The two stars rotate about each other, but one is clearly massive and yet can not be seen. Invisible, too heavy to be a neutron star, what else could it be but a black hole? Hawking advances the idea of mini black-holes and shows that they could eventually lose their mass.
David Wool's illustrations suit the text well. show less
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2,400+ Works 292,977 Members
Isaac Asimov was born in Petrovichi, Russia, on January 2, 1920. His family emigrated to the United States in 1923 and settled in Brooklyn, New York, where they owned and operated a candy store. Asimov became a naturalized U.S. citizen at the age of eight. As a youngster he discovered his talent for writing, producing his first original fiction at show more the age of eleven. He went on to become one of the world's most prolific writers, publishing nearly 500 books in his lifetime. Asimov was not only a writer; he also was a biochemist and an educator. He studied chemistry at Columbia University, earning a B.S., M.A. and Ph.D. In 1951, Asimov accepted a position as an instructor of biochemistry at Boston University's School of Medicine even though he had no practical experience in the field. His exceptional intelligence enabled him to master new systems rapidly, and he soon became a successful and distinguished professor at Columbia and even co-authored a biochemistry textbook within a few years. Asimov won numerous awards and honors for his books and stories, and he is considered to be a leading writer of the Golden Age of science fiction. While he did not invent science fiction, he helped to legitimize it by adding the narrative structure that had been missing from the traditional science fiction books of the period. He also introduced several innovative concepts, including the thematic concern for technological progress and its impact on humanity. Asimov is probably best known for his Foundation series, which includes Foundation, Foundation and Empire, and Second Foundation. In 1966, this trilogy won the Hugo award for best all-time science fiction series. In 1983, Asimov wrote an additional Foundation novel, Foundation's Edge, which won the Hugo for best novel of that year. Asimov also wrote a series of robot books that included I, Robot, and eventually he tied the two series together. He won three additional Hugos, including one awarded posthumously for the best non-fiction book of 1995, I. Asimov. "Nightfall" was chosen the best science fiction story of all time by the Science Fiction Writers of America. In 1979, Asimov wrote his autobiography, In Memory Yet Green. He continued writing until just a few years before his death from heart and kidney failure on April 6, 1992. (Bowker Author Biography) show less
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