Black holes are astrophysical objects with extremely strong gravitational fields. The concept of a black hole trapping light is based on the predictions of general relativity, a theory that describes gravity as the curvature of spacetime caused by massive objects.
According to general relativity, when a massive object, such as a black hole, is compacted into a sufficiently small volume, it can create a region of spacetime where the gravitational pull is so intense that nothing, including light, can escape from it. This region is known as the event horizon. Anything that crosses the event horizon is considered to be inside the black hole and cannot be observed from outside.
It's important to note that dark matter, which is a hypothetical form of matter that does not interact with light or other electromagnetic radiation, is distinct from black holes. Dark matter is believed to exist based on its gravitational effects on visible matter in the universe, such as galaxies and galaxy clusters. However, it does not play a direct role in the formation or functioning of black holes.
When we observe a black hole, such as the supermassive black holes at the centers of galaxies, we are not seeing a gathering of dark matter. Instead, we are observing the effects of the black hole's gravitational influence on its surroundings. This can include the accretion disk, a swirling disk of matter that forms around the black hole, and jets of high-energy particles that are emitted from the vicinity of the black hole.
The idea of trying to look through a black balloon full of crude oil is not an accurate analogy for observing a black hole. While black holes do not emit light themselves, their presence and effects can be detected through various indirect observations, such as the gravitational influence they have on nearby objects or the radiation emitted by matter falling into them.
In summary, black holes are objects with extremely strong gravitational fields that can trap light within their event horizons based on the predictions of general relativity. Observations of black holes are based on their gravitational effects and the radiation emitted by surrounding matter, rather than being a result of dark matter.