Could Superdense Bodies Exist?

The new theory of curved space created a great stir in scientific circles. Many physicists, astronomers, and other scientists felt that Einstein’s ideas were compelling and they wanted to test and prove the theory. If space is indeed curved and massive bodies create gravity wells, they reasoned, a very deep gravity well should deflect a beam of light. In other words, though light travels swiftly enough to allow it to escape such a well, the well should bend the beam enough for scientists to measure it.

What was needed for the test was a very massive body, at least by human standards. And because it is the largest object in the solar system, the Sun was the logical choice. The historic experiment took place on May 29, 1919, during a solar eclipse that was visible from the western coast of central Africa. “Bright stars were visible in the sky near the eclipsed sun,” Asimov explains, “and their light on its way to Earth skimmed past the sun. Einstein’s theory predicted that this light would be bent very slightly toward the sun as it passed.” Sure enough, after analyzing the data gathered during the eclipse, astronomers found that the light from the more distant stars did bend slightly as it passed by the Sun. In fact, the light beams were deflected by nearly the exact amount Einstein had predicted.

Einstein’s theory of curved space had been confirmed. (Several other experiments proving the validity of his general theory of relativity have been conducted since that time.) The theory of relativity also forced scientists to readdress the questions raised long before by Michell and Laplace about the extreme effects of gravity. The experiment during the eclipse had demonstrated that the Sun’s gravity well bends light slightly. It stood to reason, therefore, that a much more massive object would bend light even more. And this naturally led to the theoretical possibility that supermassive, superdense bodies might exist. If so, such a body would possess an extremely deep gravity well, perhaps so deep that light could not escape. In 1939 physicist J. Robert Oppenheimer and his student George M. Volkoff published a scientific paper predicting the existence of superdense stars that would have extremely deep, perhaps even bottomless, gravity wells.

Yet there was still no direct observational proof of such bizarre cosmic bodies. So in the years that followed, the concept of dark stars and their potentially

This photo taken by the Hubble Space Telescope shows a cluster of distant galaxies whose combined gravity distorts and bends the light these objects give off.

weird effects on space and light remained in the province of science fiction stories and films. The first attempt to deal with the idea on film was an episode of the original Star Trek television series first broadcast in 1967. Star Trek’s Captain Kirk and his crew referred to the strange object they encountered as a “black star,” which turned out to be prophetic. At the time, interest in such objects was reviving among a handful of physicists, and only a few months after the Star Trek episode aired, noted Princeton University physicist John A. Wheeler coined the term “black hole.” The name was perfectly descriptive and highly catchy, and it immediately became popular. Thereafter, the concept of black holes captured the attention of increasing numbers of physicists, astronomers, and other scientists, as well as science fiction fans. As Wheeler himself later remarked:

The advent of the term black hole in 1967 was terminologically trivial but psychologically powerful. After the name was introduced, more and more astronomers and astrophysicists came to appreciate that black holes might not be a figment of the imagination but astronomical objects worth spending time and money to seek.

Indeed, time and money turned out to be important keys to unlocking the secrets of black holes. Their prediction in theory by scientists over the course of nearly two centuries had been only a first step. The next necessary steps, or goals, were: more serious and concentrated study of the concept, including a better understanding of how these strange objects form; and a serious attempt to detect them. Since the late 1960s, these goals have been largely fulfilled by a series of exciting researches and discoveries that have significantly altered and improved human understanding of the universe.