Why Study Black Holes?

If black holes are so mysterious and in many ways unknowable, it is only natural for the layperson to wonder if they are worth studying at all. Would it not make more sense for astronomers to spend their time, energy, and money pursuing more practical endeavors? The answer to this question is a resounding no. More and more evidence suggests that black holes are intimately connected to many of the most fundamental processes of the universe. First, these objects are manifestations of ordinary gravity working overtime, so to speak. Gravity is the force that holds the universe together, and the more that scientists can learn about gravity, the better they can explain the origins and structure of the universe. “A strong motivation for searching for black holes,” physicists Mitchell Begelman and Martin Rees write, “is that they represent objects where gravity has overwhelmed all other forces, allowing one to test theories of gravitation under the most extreme conditions.”

Among the other reasons that scientists are eager to learn more about black holes is the fact that many of these objects evolved from ordinary stars. Understanding how black holes form from stars tells much about the final stages of stellar evolution. (The term “stellar” refers to stars.) Also, increasing evidence points to the possibility that the evolution of galaxies large swirling masses made up of billions of stars may be inexorably tied to the formation and life cycles of gigantic black holes occupying their central regions.

In addition, scientists now believe that black holes may contain important clues to the nature of the relationship between space and time, that is, between the familiar three-dimensional world and the fourth dimension time. Scientists often refer to the interaction of space and time as “spacetime.” Near black holes, “spacetime behaves in peculiar and highly ‘non-intuitive’ ways,” Begelman points out:

For instance, time would “stand still” for an observer who, managing to hover or orbit just outside the horizon [the outer edge of a black hole], could then see the whole future of the external universe in what, to him, was quite a short period. Stranger things might happen if one ventured inside the horizon. . . . Our uncertainty about the “interior” of black holes doesn’t reduce our confidence in predicting their astrophysical consequences [effects on the universe around them]. As an analogy, there are many mysteries deep inside the atomic nucleus, but this realization doesn’t prevent physicists from calculating the properties of atoms.

Thus, black holes seem to be closely connected to many of the basic properties and processes of the universe. Evidence shows, for example, that gravity,

Researchers put the finishing touches on an instrument that detects X-rays, a kind of radiation that can reveal a black hole’s location.

stellar evolution, the formation of galaxies, and the effects of time on space (and vice versa) are all associated in various ways with these cosmic monsters. And the search for answers to the many riddles of black holes is opening up an exciting new chapter in the ongoing saga of science.