A black hole is “a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space.” Based on this definition, black holes break two fundamental laws of physics – Einstein’s law of general relativity and quantum mechanics.
Einstein came up with his theory of special relativity in 1905, determining that the speed of light in a vacuum was independent of the motion of all observers, because the laws of physics are the same for all non-accelerating observers. This was a new way of looking at, and offered new perceptions of, time and space. Einstein generalized special relativity and Newton’s law of universal gravity in 1916, and called it general relativity, which provided a unified description of gravity as a geometric property of space and time.
However, not all of nature follows the laws of general relativity. In the early twentieth century, scientists thought that the basic laws of physics should apply to every aspect of nature; however this was challenged when they began probing nature’s smallest scales. Scientists found that light waves, atoms, and electrons did not follow these laws. Niels Bohr and Albert Einstein began studying particles to understand physics at small scales, and discovered how peculiar it was. What arose from their studies were the laws of quantum mechanics, as named after the work of Max Planck.
Because the laws of quantum mechanics fill the gaps of physics that cannot be explained by Einstein’s theory of general relativity, it makes sense that the two theories are quite conflicting. Since the two theories are conflicting, there are discrepancies in how the two theories explain black holes. General relativity explains black holes as objects with a gravitational pull powerful enough that anything that crosses the event horizon will fall in and be forever trapped and eventually crushed, unable to escape. However, in quantum mechanics, the particles and matter that have fallen into a black hole have to be conserved somewhere.
Now that it has been established how controversial black holes are, Stephen Hawking’s statement that “there are no black holes,” should be revisited. In the 1970s, Hawking published a paper on black holes, and in it he proposed that black holes were losing mass and eventually would vanish. Black holes lose their mass by slowly radiating away light, a featureless glow called Hawking radiation. This means that whatever falls into a black hole will vanish with it, contradicting quantum mechanics, and causing issues in the scientific world.
What Hawking is now currently arguing, is that instead of an event horizon, there is something he is calling an “apparent horizon,” in which matter and energy are temporarily suspended, then released. If this were to be true, it would change how we look at black holes. The absence of event horizons would mean that there are not black holes, however only “in the sense of regimes from which light can’t escape to infinity,” as Hawking described in his most recent paper. In his paper, Hawking states “there is no such thing as black holes,” because he then goes on to describe a modification in the definition of a black hole, meaning, black holes still exist, but perhaps are slightly different than from how we originally conceived them.