The Origins of the Black Hole

Contrary to what one might think, black holes were not discovered first and then studied; rather, the curiosity surrounding them preceded their discovery. Astronomer John Michell was the first to propose the idea of “dark stars,” which have escape velocities that surpass the speed of light. He envisioned a theoretical star with a diameter 500 times that of our sun, where light would be unable to escape, rendering it invisible to observers.

Although many details of his theory were inaccurate, Michell was pioneering in suggesting that such a massive object could be identified through its gravitational influence on nearby celestial bodies. Initially, this idea generated excitement among scholars, but enthusiasm waned in the early 1800s when light was understood to behave as a wave, and the effects of gravity on light remained elusive.

The Dawn of General Relativity

The landscape changed dramatically in the 20th century with Albert Einstein's formulation of general relativity in 1915. Shortly after, Karl Schwarzschild provided solutions to the Einstein field equations, offering a novel perspective on gravity. These solutions introduced the concept of theoretical objects that could lead to singularities. At a specific radius, now recognized as Schwarzschild’s radius, certain values in Einstein's equations approached infinity, leading scientists to believe that this was merely an artifact of the theory, with some unknown phenomenon preventing reality from mirroring these mathematical extremes.

In 1933, Georges Lemaître clarified that the singularities at the Schwarzschild surface were more accurately described as coordinate singularities. His work indicated that an object with immense gravity could exist, causing spacetime to warp around it, making it impossible to reach.

The Mathematics of Black Holes

Long before their actual discovery, black holes existed as mathematical concepts. In 1931, Nobel laureate Subrahmanyan Chandrasekhar demonstrated that non-rotating electron-degenerate matter could lead to singularities, suggesting that black holes could form under specific conditions. He identified a critical mass, known as the Chandrasekhar limit, at approximately 1.4 solar masses.

Skeptics of the time speculated that unknown factors might prevent this from occurring. However, subsequent findings revealed that white dwarf stars exceeding this limit would ultimately collapse into neutron stars. Robert Oppenheimer and his collaborators showed that neutron stars beyond a certain mass would align with Chandrasekhar's predictions, indicating no known physics would inhibit black hole formation. Notably, at this juncture, neither neutron stars nor black holes had been observed; they existed solely in theoretical frameworks.

Event Horizon

In the years that followed, significant advancements were made in the mathematics concerning black holes. Interestingly, the term "event horizon" predated "black hole." In 1958, David Finkelstein coined the term "event horizon" to describe the Schwarzschild surface, portraying it as a boundary where causal influences could only flow in one direction. This marked a pivotal moment in the growing interest in understanding phenomena beyond the singularity.

Where Does the Name "Black Hole" Come From?

In the early 20th century, physicists commonly referred to these enigmatic objects as “gravitationally collapsed objects.” The phrase "black hole" was first popularized by physicist Robert Dicke, who likened it to the notorious "Black Hole of Calcutta," a prison infamous for its deadly reputation.

By the 1960s, the term gained traction in prominent scientific publications. Motivated by a student’s suggestion, physicist John Wheeler recognized the marketing potential of "black hole" and adopted it in a scientific context in 1967, leading to his association with coining the term. This new terminology significantly impacted the scientific community, helping to attract attention and funding for research in this area.

The First Observation of a Black Hole

Despite the term's establishment, black holes remained theoretical until the late 1960s. Jocelyn Bell Burnell's discovery of pulsars in 1967 marked a turning point, as it was established that these pulsars were rapidly rotating neutron stars—the first physical evidence of such objects.

In 1971, researchers independently identified Cygnus X-1, an X-ray source detected in 1964, as the inaugural black hole. This discovery heralded a new era in black hole research, transforming them from abstract concepts into a tangible reality in astrophysics.

If you appreciate my work, consider supporting me through claps, follows, and subscriptions. For further reading, check out "Why Is A Black Hole Really So Special?" and "How To Really Deal With The Friendship Paradox?"

The first video, "Where does the name 'black hole' come from?", explores the origins and significance of the term, offering insights into its historical context.

The second video, "What is a black hole? Astro-Investigates Ep. 1 (Black Holes)", delves into the fundamentals of black holes and their importance in our understanding of the universe.