The nature of what happens when an object passes through a black hole's event horizon, known as the point of no return, is still a topic of active scientific research and speculation. According to our current understanding of physics, including Einstein's theory of general relativity, it is thought that crossing the event horizon of a black hole would have profound effects on both space and time.
Once an object crosses the event horizon, it is believed to be pulled towards the black hole's singularity, a region of extremely high density at its center. The gravitational forces within a black hole are so strong that they cause extreme spacetime curvature, leading to a phenomenon known as "spaghettification." In this process, an object would be stretched into a long, thin shape, resembling spaghetti, due to the gravitational tidal forces acting upon it.
However, what exactly happens to an object beyond the event horizon and whether any information about it can ever be retrieved from within a black hole is still a subject of scientific debate and remains an open question. The extreme conditions within a black hole make it challenging to apply our current understanding of physics, and a complete theory that unifies general relativity and quantum mechanics (known as a theory of quantum gravity) is needed to accurately describe what occurs at the singularity.
It's important to note that the theoretical and mathematical models we currently have for black holes provide valuable insights, but they are still theoretical and require further scientific investigation to be confirmed or refined.