- #1

Grinkle

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1. Particles fall towards a black hole but never cross the event horizon

2. After observing this for a few million years, the mass of the black hole is observed to have grown over that few million years. Or whatever time period less than infinity one chooses.

If it matters how one infers black hole mass in the answer, please help me understand how.

I am having trouble understanding how a black hole can be observed to grow in finite time if one can never actually observe it obtain an additional particle in finite time.

The best answer I can come up with is that GR does not prohibit an particle crossing the absolute event horizon in finite time, only the apparent event horizon. But I don't know if that is a correct statement about the math, I am just left without anything else to suspect.