# Thread: Imagined trip towards a black 'hole'.

1. ## Re: Imagined trip towards a black 'hole'.

Originally Posted by Neverfly
Your wording is odd- essentially, you just said there is no evidence of any Black holes at all.
even if we had a BH on our doorstep, I'm not sure that we could prove it had an event horizon, or whether it was a compact object just a little larger than its schwarzschild radius.

I think objects collapse to small balls, maybe the size of grains of sand, but the space-time warps around them so that they look like larger objects(self lensing type of process)....I can't prove it as I haven't got the maths, and maybe it cant be proved with maths, but needs powerful computer modelling...anyway, I accept that it is all ATM.

2. ## Re: Imagined trip towards a black 'hole'.

Originally Posted by Frogmarch
even if we had a BH on our doorstep, I'm not sure that we could prove it had an event horizon, or whether it was a compact object just a little larger than its schwarzschild radius.

I think objects collapse to small balls, maybe the size of grains of sand, but the space-time warps around them so that they look like larger objects(self lensing type of process)....I can't prove it as I haven't got the maths, and maybe it cant be proved with maths, but needs powerful computer modelling...anyway, I accept that it is all ATM.
Well, here is my point of contention.
That you are saying there is no event horizon and that light can escape. In which case, it is not a black hole.

That you are saying that it collapses into a physical object that has dimension is not something I am arguing with.

3. ## Re: Imagined trip towards a black 'hole'.

yes, it wouldn't be a black hole, but that label will be used by people to describe the object, because it is convention...it would be black though....and there would be some radiation. I have read the name 'pre-Hawking radiation' for such objects.

4. ## Re: Imagined trip towards a black 'hole'.

Originally Posted by Frogmarch
yes, it wouldn't be a black hole, but that label will be used by people to describe the object, because it is convention...it would be black though....and there would be some radiation. I have read the name 'pre-Hawking radiation' for such objects.
What do you mean "it would be black though?" Are you saying that light would be able to escape but that it would not produce any light of its own?
If I were to shine light on the object, would it reflect that light back to me?

5. ## Re: Imagined trip towards a black 'hole'.

Originally Posted by Neverfly
What do you mean "it would be black though?" Are you saying that light would be able to escape but that it would not produce any light of its own?
If I were to shine light on the object, would it reflect that light back to me?
I don't know....the small dense object would be heavily time dilated, so if you shone a light on it, the light might not come back for a long time. Not sure how the surface of such an object would respond to light either, whether it would be reflective at all, or absorb the light.

All I mean in theory, light from any part of the object could escape, just based on the shape of space-time......it would still be very black, because of the time dilation.....in a constant state of collapse for hundreds of billions of years...

6. ## Re: Imagined trip towards a black 'hole'.

Originally Posted by Frogmarch
I don't know....the small dense object would be heavily time dilated, so if you shone a light on it, the light might not come back for a long time. Not sure how the surface of such an object would respond to light either, whether it would be reflective at all, or absorb the light.

All I mean in theory, light from any part of the object could escape, just based on the shape of space-time......it would still be very black, because of the time dilation.....in a constant state of collapse for hundreds of billions of years...
OK.
Well remember that light moves at 'c.'
In this, 'c' represents a Universal Constant. It is not the speed of light, rather light speed is limited to 'c' by a fundamental property of space time.
So, if I was in a very fast startship moving at 99.99% of 'c' and I turned on my headlights, the light from my headlights would still move at 'c.' Not at my speed plus 'c' nor less then 'c,' simply at 'c.'
That this is a Constant and that the constant limits the propagation of light or gravity at that limit placed by the constant tells us what our upper bound is.
My question is aimed at this and I'm not concerned about the reflective index of the object. For this talk, let's assume it has the surface of a mirror, if that helps.
What you have clarified is that you think that light would escape from the object.
This means "There are no Black Holes."
Which goes back to my other question: Are you saying that the gravitational pull currently calculated (Enough gravity to warp or bend spacetime so drastically as that spacetime is bent back in itself, causing light to also be curved back inward) is in error and that the object would have less gravitational pull?
Or, are you saying that the object would have the same currently calculated gravity but that spacetime would not behave in that way?

7. ## Re: Imagined trip towards a black 'hole'.

well they say that time dilation rises exponentially as something falls towards the event horizon. I just don't think anything can actually cross any event horizon, and that the co-ordinate system that describes a spherical co-ordinate system is in error. I have read that the EH's sphere all has the same co-oridnate, in some syetm, and I think that is because the EH, is a point, not a surface. There is no inside the EH; eg you can't go further north than the north pole.

Obviously I only have a loose grasp of what I feel to be right...without the maths. The collapse of a star needs to be modelled continuously, for an outside observer, and in that case, nothing will fall through any event horizon.

I think gravitational time dilation slows down light...I think it is supposed to, so your torch light would blueshift in, reflect off the grain of dust ball and red shift back out..or something like that. Maybe it would come back out in a billion years..?

8. ## Re: Imagined trip towards a black 'hole'.

I can't remember what was said on BAUT but I'm not sure how a photon would be reflected by a collapsing object....blueshifted inn, redshifted out, but there was more....as the ball is collapsing..maybe that would cause more redshifting reflecting back......I don't really know, but I think photons would come back out in some form or other.

9. ## Re: Imagined trip towards a black 'hole'.

Originally Posted by Frogmarch
well they say that time dilation rises exponentially as something falls towards the event horizon. I just don't think anything can actually cross any event horizon, and that the co-ordinate system that describes a spherical co-ordinate system is in error. I have read that the EH's sphere all has the same co-oridnate, in some syetm, and I think that is because the EH, is a point, not a surface. There is no inside the EH; eg you can't go further north than the north pole.

Obviously I only have a loose grasp of what I feel to be right...without the maths. The collapse of a star needs to be modelled continuously, for an outside observer, and in that case, nothing will fall through any event horizon.

I think gravitational time dilation slows down light...I think it is supposed to, so your torch light would blueshift in, reflect off the grain of dust ball and red shift back out..or something like that. Maybe it would come back out in a billion years..?
In Relativity, time is a relation to energy and mass.
According to the theory of Relativity, time dilation would not have the same effect on a massive object as a massless object.
In this case, light would still be limited to 'c' even near a black hole because photons have no mass.
While a starship approaching a black hole would be subject to time dilation, photons would not. Light would not be slowed down by the vicinity of a black hole.
But light still must follow spacetime even if spacetime is curved. Light always moves at 'c' and it also always moves in a straight line. But if spacetime itself is curved, then light follows a straight line through a curve. This is analogous to a car following a banked curve in a road not turning its steering in either direction but maintaining a straight course. The banked road redistributes the path of the car.

10. ## Re: Imagined trip towards a black 'hole'.

yes, that sounds right.

Well then the light from the torch would just blueshift in, reflect and redshift out. Not sure what effect reflecting off an object collapsing at close to the speed of light(in its own time frame) would have on the frequency of the light reflected...redshift it I think.

As it would be reflected off a small sphere the light would go off in all directions, but I do believe that some photons would leave the object, and return to the torch holder.

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