One of the many interesting and fascinating items of modern physics is black holes. Complex and unusual, these objects have captivated many people. They have even been featured in many science fiction stories. In actuality, these objects, may be quite commonplace, and are not, in fact, a discovery of recent years. This essay will serve to describe how black holes were discovered, and briefly describe what they are.
Black holes are not holes in space, nor are they uniform in size, they are unusual and diverse in nature. One can briefly describe a black hole as an object that is so dense as that no radiation can escape its gravitational pull. (Cosmic 132) In fact, it's name is somewhat of a misnomer; black holes are in fact matter, and therefore tangible. One could even hold a black hole in one's hand, assuming the gravitational force hadn't crushed it. Black holes, originally thought to have only been formed by supermassive stars collapsing in by their own gravity, to a mass smaller than the moon, also exist in many other forms. "Proposed varieties include primordial black holes...low mass objects formed shortly after the beginning of the universe; stellar black holes...and supermassive black holes, equivalent to millions of stars in mass and located in the centers of galaxies." (Cosmic 132) The "primordial" black holes have only been theorized; created by the big bang. (Cosmic 110) The Hubble space telescope, on the other hand, has photographed supermassive black holes. Our own galaxy, the Milky Way, has a black hole in its center, having been measured indirectly. (Science Odyssey) Black holes have been found to give off X-rays; as matter is sucked into the black hole, large amounts of x-rays are expelled. One black hole candidate, Cygnus X-1, had been discovered by it's large x-ray signature. Black holes are one of the many irregular and fascinating objects in the universe.
Black holes are not a concept of the 20th century, but a concept that goes back over 200 years. "[The] earliest mention of what is now called a black hole came... by a man named John Mitchell... [in] 1783.... Mitchell...postulate[d] a celestial body so compact that its escape velocity would exceed the speed of light.... Mitchell's concept was essentially ignored by the scientific community [of the time]...." (Cosmic 101-2) It was not until "French astronomer Pierre-Simon Laplace independently reached the same [conclusion] as Mitchell...[in 1796]." (Cosmic 102) Black holes, however remained a theory for quite some time. Albert Einstein would play a part in the story of the black hole; his theory of relativity "became a tool for understanding the bizarre gravitational effects of dense stars and black holes." (Cosmic 102) It was only until recently did astronomers and physicists get their first glimpse at black holes, through the Hubble space Telescope. Today, such great physicists as Stephen Hawking continue to entertain the unusual properties of the black hole, and may even envision new types and characteristics of them.
Black holes, one of the great mysteries of the universe, remain a problem for modern physics. No one truly knows how they function or where their "holes" go. The theories and attributes of black holes are constantly being changed as we learn more about them, and our universe. One thing will always remain about black holes; they will always be an enigma to decipher, a riddle to be broken.
Cosmic Mysteries. Time-Life books: Alexandria, VA, 1990.
Cutnell, John D. and Kenneth W. Johnson Eds. Physics. 4th ed. John Wiley
and Sons: New York, 1998.
Golden, Frederic. Quasars, Pulsars, and Black Holes; a scientific Detective
Story. Charles Scribner's Sons: New York, 1976.
Video; A Science Odyssey; Modern Physics.