Black holes
Black holes have played a part in countless science fiction stories. The black hole is a particular favorite of Fred Pohl, whom I met in the late 1970s. He has written a number of SF novels dealing with black holes, most notably Beyond the Event Horizon (1980) and Gateway (1977).
Scientist John Wheeler introduced the term "black hole" to describe a solar gravitational collapse in 1969, although it was first pointed out in the 18th century by John Mitchell and the Marquis de Laplace.
A black hole is an extremely dense star. The star has collapsed, increasing its density to the point where nothing, not even light, can move fast enough to escape its tremendous gravitational pull. Since nothing can escape, the star is like a "bottomless pit" or hole in space, sucking in everything that comes near. It is black because no light shines from it. Hence the name "black hole."
Physicists first theorized the existence of black holes, but science fiction writers brought these fascinating objects to the public awareness. In his 1974 novel The Forever War, Joe Haldeman wrote about an interstellar war using black holes for travel between battles. Black holes are also used as star gates in Joan Vinge's The Snow Queen (1980).
Black holes are formed from collapsed stars, yet they themselves are not solid bodies. Rather, a black hole is a region of space into which matter has fallen and from which nothing, not even light, can escape. Since light cannot escape the tremendous gravitational attraction of a black hole, it would be invisible to us, hence the name "black" hole.
Remo J. Ruffini, a Princeton astronomer, found the first black hole, Cygnus X-1, in 1971. Since then, many other black holes have been observed. In 1998, astronomers observed a binary star, XTE J1550, about 17,000 light years away in the Norma constellation. As the black hole siphons gas from its companion star, jets of x-rays are emitted at velocities close to the speed of light.
One giant black hole in the Perseus Cluster, a group of galaxies located 250 million light-years from Earth, has been emitting a musical note - a B-flat about 57 octaves below the middle C in a standard piano keyboard - for billions of years.
Another giant black hole, in a galaxy about 700 million light-years away, completely ripped apart a star the size of our sun within days, swallowing the equivalent of one Earth every 10 minutes. The star got caught in the black hole's powerful gravitation field when its trajectory brought the two objects close together.
The black hole, as massive as 100 million suns, stretched the star until it pulled apart; the gravity of the black hole produces a tidal effect similar, but many times more powerful, than our moon's pull on the oceans which creates the tides.
Our own galaxy, the Milky Way, also contains a giant black hole - weighing between 3 to 4 million times more than our sun. Fortunately, this super dense black hole is located in the center of the Milky Way, about 25,000 light years away from Earth. So it doesn't pose any danger to us any time soon.
At the other end of the size spectrum from giant black holes are miniature black holes: some physicists today believe that when cosmic rays, the most energetic particles in the universe, strike the Earth's atmospheres, some of these collisions could be forming miniature black holes.
These miniature black holes would have a diameter of just 1/100th of a quadrillionth of an inch and weight equal to a thousand protons. But they evaporate in a fraction of a second because, unlike ordinary, more massive black holes, micro-black holes leak energy.
CERN recently built and began testing the world's largest supercollider, capable of accelerating protons toward each other at 99.999999% of the speed of light. Some physicists stated that doing so could possibly produce tiny black holes, which if they do not decay as predicted, could potentially grow and destroy the Earth.