Black holes were first theorised by John Michell in 1783. He named them ‘Dark Stars’. At that time, it was a common belief that light was made up of particles which reacted to gravity. Michell believed that these so called ‘dark stars’ were very large stars with a very strong gravitational field, so strong that no particles could leave, including light particles. This meant that ‘dark stars’ would be invisible to the human eye.
Progress was not made on the theory of black holes and dark stars until the 1900s, when Albert Einstein started work on his theory of general relativity. His theory stated that space and time were different directions in ‘space-time’. This was then bent, creating black holes.
The current theory of black holes came from John Wheeler in 1967. They originate as stars, formed when stars begin to die, cooling and shrinking, increasing in density, until it becomes a concentrated mass that bends space-time, punching a bottomless hole through it. The smaller and more dense the mass, the stronger it’s gravitational pull, eventually even light cannot escape. The Event Horizon is a point where the gravity is just strong enough to drag light backwards. Past this boundary, light can escape, meaning we can see up to, but not beyond, this point. Nothing can travel faster than light, so if light cannot escape the black hole, nothing else can. However, if you are beyond the event horizon, it is possible to resist the gravitational pull, albeit with great difficulty.
The stark lack of light is just as eye catching as a bright light. A black hole appears as a black void, in which nothing can be seen, not even a slight outline. Space is always lit up by stars, and so a sudden gap in light is noticeable.
The size of a black hole relates to how much matter is in it. A larger black hole contains more matter. Due to the uncertainty relation, a concept imagined by Werner Heisenberg in 1923, some particles are able to escape from a black hole, despite the fact that nothing can travel faster than the speed of light. The uncertainty relation means that with sub-atomic, and atomic sized objects, such as the particles in black holes, it is impossible to tell more than one aspect of its movement accurately. If the exact location of a particle is known, the exact speed cannot be known and vice versa.
In smaller black holes, the location is known, so the speed can only be estimated, and varies to a certain degree. This then makes it possible for particles to move just over the speed of light, despite what anyone’s ever been told about light being that fastest thing to ever move. Anything moving over the speed of light has the ability to ‘outrun’ the gravity that is pulling it back into the hole, meaning it can escape past the event horizon. Inside a black hole, the most popular theory is of a singularity. The remains of the dead star, once it has finally stopped shrinking. Atoms, in their common state, are mainly empty space.The gravity in a dying star becomes so strong that it causes these atoms to collapse on themselves, leaving no space, either between that atoms and within the atoms. This is the densest an object can ever become, and since the atoms no longer exist as atoms due to them losing their atomic structure, the singularity has no specific material or chemical elements.
It has been theorised, that in seeing the singularity, it would be possible to avoid hitting it and being compressed to become part of it. In simpler words, it would be possible to avoid being squashed to death. Instead, one could almost swim past it, falling through a wormhole. These are disturbances in the fabric of space-time. By falling through one, you would end up in another area of space-time; a different place, a different time, or both.
Some original uses of black holes appeared in fiction writing long before the idea had been properly investigated by scientists. To start with, they were imagined as ‘monsters’, the villains in a story that would consume anything near it. They may also travel through space, eating anything in it’s way. They were ‘vacuum cleaners for the universe’, often sucking up nearby stars and planets, and the occasional unlucky astronaut or space-explorer.
Later, they were adapted into wormholes, used as portals for people to travel between different places, galaxies and sometimes even universes. Being able to travel faster than light became a common occurrence, with both dystopian and utopian novels using wormholes as the futuristic method of transport. Sometimes, characters would appear in unpredicted places, however star-gates were also made, where each wormhole had a partner that linked to each other, much like a doorway between different sides of the universe.
They were also used as a method for people to travel in time, being able to see the future and travel to the past. This attribute could be used for both good and bad characters, used to fix the future or to change the past.
Featured image: By Event Horizon Telescope – https://www.eso.org/public/images/eso1907a/ (image link) The highest-quality image (7416×4320 pixels, TIF, 16-bit, 180 Mb), ESO Article, ESO TIF, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=77925953