The development of the standard models on the origin of black holes began with Albert Einstein, and his work developing his general theory of relativity—one of the most important discoveries to shape our understanding of physics. In the simplest possible terms, it predicts that there are regions in space with gravitational fields so intense that they warp the fabric of the universe where no matter or radiation can escape.
These regions are called black holes, and the threshold around the black hole where the escape velocity surpasses the speed of light is called the event horizon.
Additionally, it is thought that within the event horizon, is located the black hole's singularity. Research suggests that this is where the mass of the object that created the black hole has collapsed to an infinitely dense extent. The fabric of space and time around the singularity is theorized to be curved to an infinite degree, so the laws of physics as we know them break down.
However, some researchers believe singularities may actually be impossible, arguing that matter is not capable of collapsing to an infinitely small point. To get around this, some physicists have proposed singularity-free black holes, called “dark stars”. These objects may appear to be black holes, but instead of an infinitely dense core, dark stars contain a core of matter compressed to the tiniest possible scale, what is known as a “Planck core” (named for the incredibly tiny Planck length, a unit of measurement which is 10^-35 meters, around 100 trillion times smaller than a proton).
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