Final answer:
Observationally, the formation of a black hole appears to take infinite time due to gravitational time dilation, but this doesn't apply to primordial black holes, which formed early in the universe. These black holes and the seeds of supermassive black holes may have contributed to the dark matter content and are evidenced by indirect astronomical observations.
Step-by-step explanation:
If we observe matter falling into a black hole from an external point of view, it appears to take an infinite amount of proper time to do so. This phenomenon occurs due to the immense gravitational effects that significantly slow the passage of time near the event horizon as seen from an outside perspective. For objects within this gravitational influence, such as an astronaut, their perception of time remains unchanged, and they would continue to fall into the black hole at a normal rate. Observationally, this results in a redshift that stretches the light from the infalling object, making it dimmer and increasingly difficult to detect as it approaches the event horizon.
Contrary to what Einstein initially thought, primordial black holes are believed to have formed in the early universe under high-pressure conditions, long before the formation of stars and galaxies. These black holes do not develop via the collapse of stars; thus, the paradox of observing a black hole's formation from afar does not apply. Fundamental solutions to the formation of supermassive black holes are still being researched, with theories suggesting they emerged early in the universe's history, grown from large 'seed' black holes. Primordial black holes and these seed black holes are considered to have contributed to the dark matter content of the universe. These objects do exist, and evidence of their existence comes from indirect observations, such as the effects of their gravity on nearby visible matter and the radiation emitted when they consume matter.