For an explanation, see the main splats page
The principles of black holes
- In calculating the Milky Way's mass, based on its rotation, astronomers find there should be more mass: they call the deficit "the missing dark matter".
- The matter contained in stars and black holes makes up most of the known mass in the universe, possibly all of it, but nobody is sure at this stage.
- In 1783, John Michell outlined the nature of a Newtonian black hole, based on the idea that light consists of particles, and so would be affected by gravity.
- In 1916, Karl Schwarzschild offered a singular static solution of gravitational field equations which describes a minimal black hole, and sent it to Einstein.
- In 1916, while fighting on the Russian front, Karl Schwarzschild applied relativity to the inner workings of a star, then died of a battlefield illness.
- Black holes are so massive that no light can escape past a limit of the black hole, a surface called the event horizon. This is not the edge of the black hole.
- A black hole is typically surrounded by an accretion disc, a fast-rotating disc of dust and other material which eventually falls down into the black hole.
- Schwarzschild concluded that when a star contracts under gravity, there is a point when the gravitational field is so huge, nothing, not even light, can escape.
- The radius of a star of any given mass when it reaches the stage of collapse at which it traps all light is now known as the Schwarzschild radius.
- Our Sun has a Schwarzschild radius of 2.5 km, and if it ever actually shrinks below that radius, will become a black hole, from which nothing can escape.
- In 1967, John Wheeler, introduced the dramatic term 'black hole' to describe a concept that went back to earlier times, but never with such a name.
- In 1972, James Bardeen, Brandon Carter, and Stephen Hawking proposed four laws of black hole mechanics in analogy with the laws of thermodynamics.
- As material falls into a black hole it loses electrons and is broken down into charged particles, and as these accelerate, they emit large amounts of radiation.
- In 1973, Ostriker and Peebles found the amount of visible matter in typical spiral galaxies was not enough for Newtonian gravitation to keep the disks together.
- Wormholes are theoretical structures associated with black holes and loved by science fiction writers as possible ways to cross large lumps of space, fast.
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