Bear with me, I am (not even) a chemist. This is something that bothers me for some time. The larger the black hole, the smaller the density and the smaller the tidal forces. Supermassive black holes (expected to exist in centers of galaxies) have density comparable to that of water, and I was told (in some other thread at PF) that tidal forces on the event horizon are "bearable" - that is, it can be in theory possible to cross the event horizon without being changed into a pretzel or rotini. For any given mass we can easily calculate Schwarzschild radius, and the the density of the matter inside. Here comes the part that can get me banned. A hypermassive black hole can have density comparable to that of the Milky Way, or a local group of galaxies. If so, is there anything that would make those living inside aware of the fact they are inside of a black hole? Or is there some other problem I am not aware of? Instant ban: if the situation I described above is possible, what stops black holes from being nested?