shape of our universe theory and questions..

The non amateur stuff. Hawking, black holes, that sort of thing

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Moonstruck
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Post by Moonstruck »

Thank you all for your response.
davep and spodzone,
May I suggest you refer to joes reply which, I think you will find is pretty straight forward.
Thank you joe,
moonstruck.
davep
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Post by davep »

You mean the reply that says what I was saying but in different words? :roll:
Moonstruck
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Post by Moonstruck »

If you like davep,
I felt joes was ,shall we say, more rounded. :P
davep
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Post by davep »

What was "unround" about me asking a question or two to try and understand the picture you had in mind?
Moonstruck
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Post by Moonstruck »

Davep,
I'm sorry,perhaps, instead of speaking of a back door I should have said a half sphere ,which at present we have not been able to explore.Have we? But,maybe one day the scientists will be able to satisfy their research as to what is or is not happening around the other side of a black hole.
Hopefully this will help you understand that which I was pondering upon.
No doubt I'm wasting my time even thinking about such things.
Hope this puts your mind at rest,
moonstruck.
davep
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Post by davep »

Moonstruck wrote:I'm sorry,perhaps, instead of speaking of a back door I should have said a half sphere ,which at present we have not been able to explore.Have we? But,maybe one day the scientists will be able to satisfy their research as to what is or is not happening around the other side of a black hole.
I take it then, from Joe's post at least, that you now gather that to think of a black hole as a sphere and one for which only half is visible is a misleading view to hold?

Hence what I said about the Moon and why it was a misleading example. Running with that analogy (as I did), there's nothing special or hidden about the other side of the Moon except for the fact that it's period of rotation is locked in with the period of its orbit. If this were not the case then you wouldn't have needed probes to take a peek at the far side.

Think of Mars for example. With your telescope, over the course of a few nights, you can get to see every side of the planet (okay, with the exception of a good view of the poles) because of its rotation.

The "hidden" thing with black holes, the "side" you can't see, is the "inside".
Moonstruck wrote:No doubt I'm wasting my time even thinking about such things.
Thinking never seems like a waste of time to me.
Moonstruck
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Post by Moonstruck »

No davep, I don't get that impression from joes post .(If only I knew how to append the comments of other peoples post).
I still get the idea that a black hole is maybe of spherical form and that it could always be presenting one veiw only that can be seen by ,I suppose radio waves.Which is why I used the analogy of the moons one face presentation toward earth.
As to wasting my time thinking.If I was much younger I could still dream o f pretty girls,which would be much more rewarding, than trying to understand things which are not yet totaly proven.And maybe never will.
Theres nothing wrong with you asking questions.But, some of your responses shot straight over my head and please don't ask me what I mean cause I shan't tellyou.
All the best,
Moonstruck.
davep
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Post by davep »

Moonstruck wrote:I still get the idea that a black hole is maybe of spherical form and that it could always be presenting one veiw only that can be seen by ,I suppose radio waves.Which is why I used the analogy of the moons one face presentation toward earth.
Why do you have this impression of a black hole? If you were to view one as a sphere, why do you think it would only present one face to us?
Moonstruck
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Post by Moonstruck »

Davep,
Why not, after all ( oh dear back to the moon) the moon presents one face. Why not a black hole?
Another silly thought goes through my mind,if within the black hole there is a sphere which is revolving,does that mean that the black hole entry is allways facing the same way?If not ,then can the radio waves beamed at such black hole only be absorbed when the black hole is is facing transmission. Or is it supposed that a black hole soaks up anything from all around it(front & back)Oh no, not the back door again.
Be happy,
spodzone
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Post by spodzone »

Moonstruck wrote:Davep,
Why not, after all ( oh dear back to the moon) the moon presents one face. Why not a black hole?
Because black holes tend not to be the moon?

As has already been explained, the moon rotates in sync with its orbit around the earth, hence why it only presents one "face" (modulo libration). This is a comparatively special relationship; given the potentially large number of black-holes out there, why should any/all of them do the same?
Last edited by spodzone on Mon Jan 23, 2006 11:35 am, edited 1 time in total.
~Tim
davep
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Post by davep »

Moonstruck wrote:Why not, after all ( oh dear back to the moon) the moon presents one face. Why not a black hole?
The Moon only presents one face to the Earth -- and even that isn't quite true (consider libration for example) -- due to synchronous rotation. The Moon does, however, rotate. For a given black hole to have the same effect, as viewed from the Earth, it would have to be stationary.

Are you suggesting that all black holes are stationary and only present one "face" to the Earth?
Moonstruck wrote:Another silly thought goes through my mind,if within the black hole there is a sphere which is revolving,does that mean that the black hole entry is allways facing the same way?
There is no "entry" in the way you're thinking about it. There is no single way into a black hole in the same way that there is no single way into the Earth's atmosphere.
Moonstruck wrote:Or is it supposed that a black hole soaks up anything from all around it(front & back)Oh no, not the back door again.
There is no "front and back", just like there's no front or back to the Earth, or the Sun, or the Moon, or any other sphere in space.
Moonstruck
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Post by Moonstruck »

Davep,
Pity libration is not libation.

Hope not otherwise they might all gang up and draw the earth into the black abyss.
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Post by joe »

Moonstruck wrote:if within the black hole there is a sphere which is revolving,does that mean that the black hole entry is allways facing the same way?If not ,then can the radio waves beamed at such black hole only be absorbed when the black hole is is facing transmission.
Could it be, Moonstruck, that the picture you have in your mind of a black hole is that of a kind of funnel or whirlpool where matter is being sucked in? Like the HMV gramaphone horn? Black holes are often depicted in diagrams as dark ....er..holes with everything falling into it. This is normally to show how mass effects the surrounding space/gravity but is not a real visual depiction.

A "truer" picture would be a black sphere, or balloon even, the centre of which is a tiny object of extremely large mass. Everything inside the balloon would INEVITABLY be drawn into this tiny object, the singularity. There would be no escape. Consequently there would be nothing there between the skin of the balloon and its centre (unless there is matter in the process of falling to the centre). If a spaceship was just outside the skin of this imaginary balloon it would have to keep firing its rockets in order to stay away from the skin (event horizon) just as in the same unexotic way a spaceship several metres from the surface of Cape Canaveral would have to keep firing its rockets if it wanted to stay off land. But the fact is that a black hole, the bit that we can "see" (darkness), is a three dimensional object that can be approached and orbited from any direction in the same way that Mars can, for instance.

Forgive me if this is patronising nonsense.
200mm Newtonian, OMC140, ETX90, 15x70 Binoculars.
davep
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Post by davep »

joe wrote:Could it be, Moonstruck, that the picture you have in your mind of a black hole is that of a kind of funnel or whirlpool where matter is being sucked in? Like the HMV gramaphone horn?
Like this diagram for example.
joe wrote:A "truer" picture would be a black sphere, or balloon even
Like this impression for example.
spodzone
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Post by spodzone »

davep wrote: Like this impression for example.
Oh, strange - I don't picture black holes that way at all. (It's only a schematic of a gravitational potential well, it doesn't mean you're going to see a rubber sheet with grid-lines from your space-ship window, after all.)

http://sci.esa.int/science-e-media/img/f4/17316.jpg sort of works for me, except note that we don't see X-rays so that'd be mostly black, right?
~Tim
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