My understanding is that one can never observe an object crossing the event horizon. Instead, one will observe the infalling mass "smear" over the (imaginary) spherical surface of the event horizon. If my understanding is correct, then how do black holes grow in mass, and therefore, size? I've been reading about BHs at galactic centers that are millions of solar masses, and the articles usually state that this mass is acquired by the BH "consuming" everything in its vicinity over billions of years. I am having a hard time reconciling the two ideas... that to an observer, all infalling matter remains forever outside of the EH, yet a BH can grow to multi-million solar masses.