But if we take into account the fact that light rays also carry energy and
bent, curved spacetime, the picture will be similar.
We will also have a family of outgoing geodesics that are in this
region are going to infinity, in this region are going inside,
in the seeds we will see that.
For the seeds, this will be apparent.
But it will happen that this light ray will either belong to this family,
or to this family, but will not eternally stay on this surface,
due to the fact that it also bend to curved spacetime.
So, it will contribute to the emission of gravitational waves or
some other stuff like that.
So, let me re-phrase this what I am saying in different terms,
I'm saying the following thing.
That if this guy emits radiation which is received by
an absorber which stays always outside the black hole,
this absorber will see the very last sug,
the very last wave packet emitted by the star.
And the one which is after it will contribute to the body of the black hole
to the energy of the black hole, and will not be received by this observer.
So this observer will stop receiving light rays from the collapsing body.
Will stop receiving light rays from the collapsing body within finite
time as measured by this outside observer.
So, this moment can be considered as the moment of the creation of the black hole.
Of course, this explanation that I have gave to you,
has some drawback because the moment of the creation of the black
hole is somehow related to the energy carried by this light ray.
Stronger is the energy carried by each wave packet,
earlier the creation is happening.
This is a drawback.
And of course, I am vaguely explaining to you the picture
which demands some farther regress study, an explanation.
So I just gave you the idea, my idea of what is going on and
why the creation of the black hole happens within finite period
of time from the point of view of outside observers.
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