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Can math.atan2 return INF?


Gregory Ewing <greg.ewing at canterbury.ac.nz>:

> Marko Rauhamaa wrote:
>> Which phenomenon prevents a black hole from ever forming. Yet
>> astronomers keep telling us they are all over the place.
> Astronomers have observed objects whose behaviour is entirely
> consistent with the existence of black holes as predicted by general
> relativity.

As far as I understand, all we can ever observe is black holes in the
making since the making can never (seem to) finish. IOW, the event
horizon never forms.

These almost-black-holes are virtually indistinguishable from black
holes proper. However, we don't have to speculate about the physics of
the insides of the black hole.

> The singularity being talked about there is an artifact of a
> particular coordinate system; the theory predicts that there is no
> *physical* singularity at the event horizon.

That theory can't be tested even in principle, can it? Therefore, it is
not scientific.

> It's true that we outside can't be absolutely sure that things are as
> predicted at the horizon itself, because any observer we sent in to
> check would be unable to report back. But in principle we can observe
> arbitrarily close to it. The observations we've made so far all fit
> the theory, and the theory doesn't present any obstacles to
> extrapolating those results to the horizon and beyond, so we accept
> the theory as valid.

Religious theories about the afterlife face similar difficulties -- and
present similar extrapolations.

> There *is* a difficulty at the very center of the hole, where there is
> a true singularity in the theory, so something else must happen there.
> But for other reasons we don't expect those effects to become
> important until you get very close to the singularity -- something on
> the order of the Planck length.

That's my point: such speculation must remaing mere speculation. The
universe doesn't owe us an answer to a question that we can never face.


Marko