A hole that can never be filled

So far, I have described the formation of a black hole in terms of
gravitational collapse. But we have learnt that Einstein’s view of
gravity is in terms of the curvature of space. Ablack hole can also
be described in this way.There are two interesting observations we can make here
based on this simple picture. Firstly, a black hole can never be
plugged up or filled in with matter. The more matter that is poured
into a black hole the bigger it gets. It will feed and grow.
Secondly, the size of a black hole, as measured by the volume
within its event horizon, is really only a measure as seen by
an outside observer. As an example, a black hole formed by
the collapse of a star ten times the mass of the Sun will have a
Schwarzschild radius of thirty kilometres, making the black hole
roughly the size of a large city. Of course, an outside observer
cannot see beyond the event horizon anyway and therefore can
have no idea what things are like inside. But if space inside the
horizon forms an infinitely deep hole then the distance from the
horizon to the singularity should really also be infinite. In reality,
and as I shall describe later, if you were to fall into a black hole then
it would take you only a very short time to reach the singularity
since space and time go haywire inside the horizon and one cannot
use simple rules such as speed equalling distance divided by time.
From the outside, all black holes of the same mass look
identical; we are unable to learn anything about the object that
created the black hole in the first place, even being ignorant
of its original chemical composition. All that information has
been lost from our Universe forever. William J Kaufmann makes
this point clearly in his excellent book, Universe. He considers
two hypothetical black holes—one produced by the gravitational
collapse of ten solar masses of iron and another from ten solar
masses of peanut butter. Once they have both collapsed beyond
their event horizons, they become identical and we are unable to
tell which black hole was formed from which substance.
A common misconception regarding black holes is that they
will eventually gobble up everything in the Universe. This is
not true. Gravity is said to behave relativistically in a region
where the predictions of Einstein’s version depart radically from
those of Newtonian gravity. For example, a black hole with
a Schwarzschild radius of thirty kilometres will only cause the
gravitational field around it to behave relativistically out to a
distance of a thousand kilometres. Outside this range, the black hole obeys the rather boring laws of Newtonian gravity and behaves like any normal star of that mass in the way it affects
the motion of distant objects.