Why do we study black holes?

Abstract

<p indent="0mm">Black holes are arguably the most mysterious object in the universe. They are an important research subject in physics and astronomy, as well as a favorite topic among the general public. The concept was conceived in the 18th century based on the mathematical form of Newton’s gravitational theory. Now, more than <sc>200 years</sc> later, black-hole research has evolved from pure mathematical speculation to a “hard-core’’ science with sound theoretical and observational foundations. Many Noble prizes in physics were, in some degree, related to black holes. In particular, not long into the 21st century, three Nobels prizes in physics have been awarded to the studies directly related to black holes. Why is an object seemingly so disconnected with daily life attracting so much attention from the scientific community? By reviewing some of the most important breakthroughs over the history of studying black holes, I will try to show the readers that black-hole research is important. First, it has shaped our perception of space and time. The theory of general relativity predicts the existence, at least in theory, of black holes. However, it cannot self-consistently explain the existence of a singularity which is bound to form at the “center’’ of a black hole. The motivation of resolving the singularity problem has inspired the later studies of the quantum nature of black holes, but has also led to the discovery of the paradox of information loss. The potential solution of such a paradox has pointed to a more fundamental relationship between quantum mechanics and the nature of spacetime. Second, it has inspired a chain of scientific discoveries. Here, I will focus on the discoveries made by astronomers. I will show that the different approaches adopted by astronomers have given rise to a series of breakthroughs in black-hole research. These discoveries not only proved that black holes exist in our university, but also have greatly enriched our understanding of the formation and evolution of stars, galaxies, and even the whole universe. Third, black-hole research has triggered major technological developments in various fields. I will show that the history of discovering black holes is closely tied to the development of radio astronomy, X-ray detectors, measurement theory, as well as quantum technology. In particular, the requirements raised by the observation of black holes have, in turn, driven many technological breakthroughs. These breakthroughs have also resulted in inventions which have become important in our daily life. China is currently running and also planning many large-scale astronomy projects which list black holes as one of their major targets. These projects will place China in the forefront of scientific exploration and technological innovation, and probably open a new era of black-hole revolution.