Black holes a Xeno thing?

I read somewhere that there are only assymptotic black holes. These are collapsed junk-heaps of matter that are getting closer and closer to being a black hole, but will never quite cross the event horizon.

Never? Well, not from an outside point of view. If you fall into one of these things, though, there will indeed be a black hole…but only by the time you get there.

Is this true? The idea makes sense to me, but I’ve also heard plenty of talk about black holes, from respected scientists, as if they are here now. Have I been misinformed? Or does it just sound better not to say “There’s something at the center of the galaxy that is forever approaching black-hole-ness?”

You are dealing with some of the time paradoxes that end up occuring whenever we speak in terms of relativity. Black holes are one of your basic relativity machines and work in such a way that it’s difficult to speak in terms of “here now”. One of the ways we can demonstrate this is by dropping a transmitter into a black hole that spits messages back at us. As it falls in, the messages (travelling at light speed) get gravitationally redshifted as well as occur far later than in flat space if they are given off at equal intervals. At the event horizon, the message never quite makes it out of the potential well. One way to think of it is that the light takes an infinite amount of time to reach you, the observer, very far away.

Now consider all the debris that initially fell in to make the blackhole. It spews off light (which is the way we know about it) that takes literally forever to reach us. So, in effect, it appears that the stuff sits forever at the event horizon, or at least it is sending us signals that that’s what’s going on. In reality, the junk as passed the point of no return long before and left our observable universe.

Zeno.