Miniature and Stellar Black Holes

Such mini-black holes would have no obvious connection with star-sized, or stellar, black holes. So the formation of the smaller version likely has nothing to do with the life and death of stars. What force or process, then, could have created mini–black holes? In the early 1970s, noted British physicist Stephen Hawking offered a believable answer, namely that these tiny superdense objects came into being during the Big Bang the enormous explosion in which, most scientists believe, the known universe was created. “With vast quantities of matter exploding all over the place,” Isaac Asimov explains,

Stephen Hawking proposed that microscopic black holes formed in the huge explosion that gave birth to the universe.

some different sections of the expanding substance [i.e., matter] might collide. Part of this colliding matter might then be squeezed together under enormous pressure from all sides. The squeezed matter might shrink to a point where the mounting gravitational intensity would keep it shrunk forever.

Hawking and others think that millions of such mini-black holes might still exist in various parts of the universe. If so, sooner or later a few might come close to an asteroid, planet, or other large solid body and be drawn to it by its gravity. Such a cosmic meeting would probably be neither dangerous nor catastrophic, however. According to Asimov:

If a mini-black hole collides with a larger body, it will simply bore its way through. It will engulf the first bit of matter with which it collides, liberating enough energy in the process to melt and vaporize the matter immediately ahead. It will then pass through the hot vapor, absorbing it as it goes and adding to the heat, emerging at last as a considerably larger black hole than it was when it entered. The channel cut through a planet by a mini–black hole would be so small and narrow that it would be far less noticeable or consequential than a tunnel dug through a garden by an ant. If mini-black holes do exist, therefore, their physical effects on large bodies are minimal and they are of little concern to human beings and any other living beings inhabiting the universe.

By contrast, black holes of stellar and larger masses have far more important potential consequences for the universe and life. And this is why scientists have devoted so much time and effort in recent years to understanding how they form, as well as their properties. They realized that it would require a tremendously violent process or event to compress such gigantic quantities of matter into an extremely small space. Moreover, the energy produced would have to be millions of times larger than in those events people normally deem catastrophic including earthquakes, volcanic eruptions, and the crash of asteroids onto planetary surfaces. It became clear to scientists that only the phenomenally violent death of a large star could account for the creation of a stellar black hole.