Black Holes.....

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Black Holes.....

Postby George99 » Sun Jun 05, 2016 9:45 pm

A Black Hole has a mass - right?

Is it an object or an area of space?
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Re: Black Holes.....

Postby Gfamily2 » Mon Jun 06, 2016 9:12 am

It's an object. An object with mass, as you say, that has been compressed into a very small volume, such that it forms an event horizon which means that:
In simple terms, light cannot escape.
In General Relativity terms, all light cones are directed inwards.
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Re: Black Holes.....

Postby Rongolan » Sun Jun 12, 2016 5:44 pm

It's both.
According to classic physics or Astrophyics, balck hole is just a very small star with a vary large mass.
the thing is that....this uniqe situation (extreme mass value mainly) couses very unusuall things to hapen - the light cannot escape, objects are being stretched, and the time velocity become different. This is why sienctist use to think about a black hole as a area of space.
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Re: Black Holes.....

Postby david48 » Mon Oct 10, 2016 10:04 pm

Is there any proof that black holes really exist?
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Re: Black Holes.....

Postby Gfamily2 » Mon Oct 10, 2016 11:43 pm

david48 wrote:Is there any proof that black holes really exist?

There is evidence that there are objects that are so massive that they would form Black Holes according to the laws of physics as we know them.

Evidence includes direct measurement of the movement of stars around the supermassive Black Hole in the centre of the galaxy. https://www.youtube.com/watch?v=EvuV3GdVaY4
The LIGO gravitational wave detection is only really consistent with the collision of black holes (reason being that if they were extended objects - and not stuck behind the event horizon, their collision would have taken longer)
Having come up with these two, I had a look on wikipedia, and found there's a list of observations that are consistent.

https://en.wikipedia.org/wiki/Black_hol ... l_evidence

i.e. if Black Holes don't exist, we need a whole lot of new physics to explain
a) why not
b) what else is going on to explain these observations
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Re: Black Holes.....

Postby david48 » Wed Oct 12, 2016 4:22 pm

Thanks Gfamily2 for the links. I've viewed them, and they do seem to make a strong case.

Nevertheless, I am still sceptical. For two reasons:

1. The presentations in your links, seem to rely heavily on computer-generated images. Such images can be produced by computers, depending entirely on how they're programmed. So I wouldn't trust them to represent reality.

2. The idea that trillions of tons of solid physical matter, can be squeezed down into a "zero-point" mathematical point, or "singularity", offends against all common-sense and logic. I don't believe it at all. it smacks of magic and irrationality. Like believing in millions of angels dancing on the head of a pin.

No, there's something wrong about it.

Probably so-called "Black Holes" are extremely condensed objects. But not mathematical points, surely.
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Re: Black Holes.....

Postby Gfamily2 » Wed Oct 12, 2016 7:27 pm

david48 wrote:Thanks Gfamily2 for the links. I've viewed them, and they do seem to make a strong case.

Nevertheless, I am still sceptical. For two reasons:

1. The presentations in your links, seem to rely heavily on computer-generated images. Such images can be produced by computers, depending entirely on how they're programmed. So I wouldn't trust them to represent reality.

2. The idea that trillions of tons of solid physical matter, can be squeezed down into a "zero-point" mathematical point, or "singularity", offends against all common-sense and logic. I don't believe it at all. it smacks of magic and irrationality. Like believing in millions of angels dancing on the head of a pin.

No, there's something wrong about it.

Probably so-called "Black Holes" are extremely condensed objects. But not mathematical points, surely.

If you follow the physics (as we understand it)*, they have to collapse to a point, but that point is within an event horizon, which prevents us from knowing anything about what's inside the black hole other than its mass, its charge and its spin.

* This is the important consideration of course, as far as we know a collapse to a point is inevitable, but in order to avoid a collapse to a singularity you need to develop a physics in which something else happens. It's very likely that 'something else' happens inside the event horizon, but at the moment we don't have a clue what that might be.
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Re: Black Holes.....

Postby david48 » Tue Oct 18, 2016 4:43 pm

Yes - as you say, "something else" very likely happens, to prevent the collapse into a singularity.

The singularity appeals to mathematicians. Because they view it as the inevitable result of a "gravitational" force which can theoretically go on without limit. Until it squeezes an object into an infinitely small, zero-dimensional point.

These mathematicians might just as well argue that the "acceleration" force, can theoretically go on speeding up an object, until it acquires an infinitely great velocity.

But this doesn't happen in the real Universe. Something intervenes to prevent infinite speed.

So similarly, something may intervene to prevent infinite collapse?
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Re: Black Holes.....

Postby The Man with the Corrugated Iron Roof » Thu Nov 10, 2016 10:45 pm

I don't buy this singularity bit either BUT ...

It could be very very VERY small, like dividing 10 into 1 about 33 times, so that it's size if finite but much smaller than an electron. It may also be capable of spontaneously expanding in other dimensions that are unseen to us, thus creating another universe.

OK, gross simplification but that's pretty much a summary of string theory.
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