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black holes in the lab

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IamSmooth

Mon Jun 12 2006, 05:54PM

Registered Member #190 Joined: Fri Feb 17 2006, 12:00AM
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Does this mean that at the center of every black hole, including the supermassive black holes thought to be at the center of galaxies, is a singularity?

mike0t4ever

Mon Jun 12 2006, 06:06PM

Registered Member #321 Joined: Wed Mar 15 2006, 03:33AM
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Firkragg wrote ...

....A mini black hole out of 2 protons or one in center of galaxy have no physical differences except size....

uhh and mass

Marko

Mon Jun 12 2006, 06:25PM

Registered Member #89 Joined: Thu Feb 09 2006, 02:40PM
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uhh and mass

Isn't mass proportional to size (of horizon, of course)?

But yes, that would surely be more appropriate word...

Quantum Singularity

Tue Jun 13 2006, 01:18AM

Registered Member #158 Joined: Sun Feb 12 2006, 09:53PM
Location: Central Ohio
Posts: 282

Firkragg wrote ...

Black hole occupies no space, and is infinitely dense.

The thing we see as a big black scary thing is generally it's horizon.

A mini black hole out of 2 protons or one in center of galaxy have no physical differences except size. (and you can divide them by size if you wish).

So than a black hole cannot exist without there being a singularity? Said another way, is it then impossible for there to be a 'stable' mass of a certain value and size that has a stong enough magnetic pull to not allow light to escape? Or is it that any object regardless of size or mass that has a gravitational pull that can suck light in must be of infinite density and not occupy any space (other than the apparent space of the event horizon)? I was under the impression that there was another threshold that had to be reached for a black hole to become infinitely dense and form a singularity.

Cesiumsponge

Tue Jun 13 2006, 01:20AM

Registered Member #397 Joined: Wed Apr 19 2006, 12:56AM
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I think black hole and singularity are used interchangably today By now, I am not sure it matters, but I recall "black hole" was a slang for singularities and describes the Schwarzschild radius of a singularity. Obviously it appears as a "black hole" in the backdrop.

A singularity can never be directly observed as it exists inside it's Schwarzschild radius but as mentioned, you can determine it's mass by measiring the Schwarzschild radius. Also the natural formation of such from dying stars are guided by the Chandrasekhar and Tolman-Oppenheimer-Volkoff limits based on a factor of solar masses.

In order to create a small singularity that fall well below those limits, you need to exceed neutron degeneracy which takes a LOT of energy.

Granted, scientists and physicists sometimes come up with clever ways to cheat and use backdoor methods to accomplish things without breaking the laws of physics so it might be possible. Occasionally you hear articles of teams proposing to create miniature black holes and other exotic research. I'm not sure if any of these have ever come into fruitation though.

Desmogod

Tue Jun 13 2006, 01:23AM

Registered Member #139 Joined: Sat Feb 11 2006, 11:01AM
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Firkragg wrote ...

Black hole occupies no space, and is infinitely dense.

No, that is not the case, one thing that we try to avoid in physics is infinities.
A black hole still has mass, and it will still emit (hawking) radiation like a hot body, therefore, a black hole isn't truly black.
It will also occupy volume in space.

Simon

Tue Jun 13 2006, 06:26AM

Registered Member #32 Joined: Sat Feb 04 2006, 08:58AM
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The event horizon of a black hole contains a volume and this is the usual definition of the size of the black hole. Saying that the hunk of matter inside occupies a finite volume is a different thing.

Theoretical physicists who shy away from the idea of infinite density have come up with alternative descriptions of black holes that do not involve singularities.

Quantum Singularity

Tue Jun 13 2006, 08:24AM

Registered Member #158 Joined: Sun Feb 12 2006, 09:53PM
Location: Central Ohio
Posts: 282

No, that is not the case, one thing that we try to avoid in physics is infinities.
A black hole still has mass, and it will still emit (hawking) radiation like a hot body, therefore, a black hole isn't truly black.
It will also occupy volume in space.

Don't the laws of physics not apply beyond the boundary of the event horizon of a singularity? In which case you wouldnt have to avoid the infinites because there are no laws that govern whats beyond the event horizon? And I thought by definition that a singularity is a single point in space (point, that means no dimension or volume)?

And I dont beleive anyone said they will not have mass, or infinite mass for that matter, although I could have missed that. They have infinite density because the mass they have takes up no space/volume.

Carbon_Rod

Wed Jun 14 2006, 01:27AM

Registered Member #65 Joined: Thu Feb 09 2006, 06:43AM
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â€Don't the laws of physics not apply beyond the boundary of the event horizon of a singularityâ€

Itâ€™s a mystery â€“ there are literally dozens of reasonable hypothesis. Some suggest manifolds in space-time that could not be considered classical mass by any means (infinite or otherwise.)

Most theories today however are not falsifiable by experiment â€“ but a plausible explanation may be observable someday

Personally I think cartoon ACME Inc. holes are less controversial and more logical then some of the ideas.

Cheers,

Dr. Slack

Wed Jun 14 2006, 11:11AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

Although both are hypothesised and neither has been proved conclusively to exist, black holes and singularities are very different things.

The theory behind black holes is very well supported. A black holes does not need a singularity inside to be black, only sufficient mass. There are places in the universe where a block hole would fit observations well. There are known simple mechanisms by which they could form.

There is no theory behind singularities beyond physicsits saying "so then when nuclear repulsion is overcome and Pauli exclusion is overcome, there's nothing to hold this stuff apart, and it all goes down to ... omg ... nothing". FWIW, I don't believe in singularities, I just don't think we know enough yet about what happens at the extremes of pressure and density (well it helps me sleep at night, other people believe crazier things!) Physicists are starting to come up with theories that avoid infinite density in a singluarity, partly 'cos it's interesting maths, and I suspect partly because they don't believe in infinite density either. Whether such will ever be testable is another matter.

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