Black Holes, for Eta Carinae

I guess I should feel honoured with a thread directed at me personally.No offence guys - but you really need to brush up on GR.I shall return (and hopefully) clear up your misconceptions on black holes. You know they are the simplest macroscopic objects in the Universe.It's been a very (understatement) hectic weekend for me from a personal standpoint (about to be a daddy again) so I will be back to answer as soon as I am able.Bye

As I alluded to earlier I am really busy right now so I'll be brief.Mike Holland:No, the observer falling through the event horizon does not see the universe age - he sees their clocks run slow just as they see his clock run slow.NosyNed:You can argue that the speed of light changes near a gravitational field (you often hear people say the metric changes the effective refractive index of space since measured with respect to flat space the geodesic is not straight but curved hence an analogy to the refraction of light in a material medium.) But most physicists don't like this analogy as it is coordinate dependent. The velocity of light only changes when you measure it using your time coordinate. If you use the proper time coordinate of the photon (i.e. along the null geodesic itself) then it's velocity is still c.To All:The event horizon has no physical reality. Nothing special happens there if you are passing it. It is a consequence of the coordinate system you are using. Yes you observe an object falling in to slow down (and get redshifted) BUT the object in reality fell in long ago. It is just the photons emitted from the falling object have a hard time climbing out of the potential well. Remember the object will rapidly fade from view as the photons as well as slowing down get redshifted out of existence.Remember that if you transform to certain other coordinate systems (Kruskal, Finkelstein) then you don't see anything special from a physical standpoint at the R=2M position but only at R=0 the singularity itself. Thus as I stated above the event horizon is an artificial effect of the coordinate system you are using (typically spherical polar in a Schwarzchild solution for a point mass in a flat spacetime.)

Read my earlier post more carefully.You jumped the gun and assumed something I did not say.Of course a clock runs faster in a plane at higher altitude than lower altitude.I was talking about when the observer 'observes' the other persons clock.OK think about it like this.As you fall through the event horizon you can only observe events in which the light can get to you.i.e. only light rays that end up on your PAST light cone can you observe.Distant future events cannot get in your past light cone THUS you do not see the universe live and die in your eyes as you fall through.Sorry if I wasn't clearer. This is hard to explain without drawing light cones and embedding diagrams.See Wald's book.

Eeeeeeeeeeeeek!OK I realise something you pointed out and I made a boo boo in my first post answering.I meant to say the person at the event horizon observes the distant observers clock run FAST. (I said slow - sorry). I was tired but heck not that tired. LOLBut there is a competing effect here - the fact of how fast you are falling in.I'll be back over the weekend to (hopefully) clear this all up. I'll crank out some calculations - it's been years since I have thought about some of this stuff.But I stand by my later comment about not observing the entire universe age in front of your eyes - though I am wondering as to how much you can see any effect of this - hence I need to crunch some numbers and get out my copy of Misner/Thorne/Wheeler.When I said the event horizon has no physical reality I meant from the perspective of the person passing through it. He/she notices nothing special - only if they try to leave it then they find that their future time coordinate now points to R=0 - meet the singularity - CRUNCH!