Re: GR: 'Line-of-sight' distance to a black hole is infinite?

On Jun 28, 10:22 am, Roland PJ <rolan...@xxxxxxxxx> wrote:
On Jun 28, 9:32 am, Eric Gisse <jowr...@xxxxxxxxx> wrote:



Oh, yes, maybe it doesn't. I was trying to integrate ds = (1 - 2M/
r)^-1/2 dr and I cocked it up.


I get:

s = [r.(r-2M)]^1/2 + 2M.log[(r-2M)^1/2 + r^1/2] + K

Where K is the constant of integration.

So, this can be evaluated, and does not diverge, inwards right up to
(and including) r = 2M, inside which it goes imaginary.

What I was really trying to do was to measure the apparent distance of
an object close to r = 2M, which I guess means I was trying to work
out what path light from the object would appear to take towards the
external observer (a null geodesic).

Does this formula accurately describe the apparent distance (hence the
time) that a photon would take from an object in radial line-of-sight
out to an external observer?

I still think so, so please correct me further.

Thanks
Roland

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