Ask Ethan: Does A Time-Stopping Paradox Prevent Black Holes From Growing?
“[F]or any object falling into a black hole, time slows down upon approach and comes to a standstill as the object reaches the event horizon. Reaching and passing that border would take an infinite amount of time measured by a distant observer… if ‘eating’ matter would take infinite time… how could supermassive black holes come into existence?”
From the perspective of an infalling particle, when you pass the event horizon of a black hole, you simply go straight through and head inevitably towards the central singularity. That should increase the black hole’s mass and cause the black hole and its event horizon to grow. On the other hand, from an external observer’s perspective, any particle that falls in will never be seen to cross the event horizon, creating an apparent paradox by where black holes would be disallowed from growing.