Which definition is better for a black hole?

super-compact, super-dense celestial object
78%
7
a rapidly rotating, unimaginably dense celestial body
22%
2
 
Total votes: 9
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Burngate
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Re: Black Holes

Fri Feb 27, 2015 6:17 pm

I wanted to vote 'neither', but I can't :(

A black hole doesn't have to rotate.

And it doesn't have to be celestial - though no-one's created one here on earth (or at least not told us about it. Maybe they got killed by it. Short story by Asimov? Clarke? Heinlein?)

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mrpi64
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Re: Black Holes

Fri Feb 27, 2015 6:42 pm

Basically it's (usually) an old neutron star that has collapsed onto (or is it unto?) itself. The rotating stuff is usually dust, or, if it's close to another star, whatever that star contains, e.g: helium (for an old-ish star).

I guess that's a bit correct? I'm not sure myself.
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Re: Black Holes

Fri Feb 27, 2015 10:24 pm

bertwert wrote: Doesn't a supernova collapse into either a black hole or neutron star?
no... a super nova is when a star reaches the end of its life and blows up, while a black hole collapses in on itself.

Neutron stars on the other hand, are the left over star after a supernova :)

Or thats what my astronomy teacher taught us...
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Re: Black Holes

Sat Feb 28, 2015 9:26 am

Ok, theyve changed the theory in the last 5 years lol
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Re: Black Holes

Sat Feb 28, 2015 9:47 am

I though they only had
mass , rotation and circumference [not radius]
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Burngate
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Re: Black Holes

Sat Feb 28, 2015 10:47 am

RaTTuS wrote:I though they only had
mass , rotation and circumference [not radius]
... and charge.
I wrote:Short story by Asimov? Clarke? Heinlein?
Niven, The Hole Man, 1975

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kusti8
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Re: Black Holes

Sat Feb 28, 2015 3:25 pm

bertwert wrote:
dan3008 wrote:Ok, theyve changed the theory in the last 5 years lol
MY textbook is 2007... 8 years old.
Maybe this is the Canadian theory :-)
I have a science book (not textbook) from 2014 which basically says that a black hole is an object whose gravitational pull is so great that nothing can get out. Not the most scientific, I know, but that is what it classifies it as. Another book from '93 says more hypothesizing ( :lol: ), but basically says the same thing.
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Re: Black Holes

Sat Feb 28, 2015 9:48 pm

kusti8 wrote:
bertwert wrote:
dan3008 wrote:Ok, theyve changed the theory in the last 5 years lol
MY textbook is 2007... 8 years old.
Maybe this is the Canadian theory :-)
I have a science book (not textbook) from 2014 which basically says that a black hole is an object whose gravitational pull is so great that nothing can get out. Not the most scientific, I know, but that is what it classifies it as. Another book from '93 says more hypothesizing ( :lol: ), but basically says the same thing.
And the sad truth, we'll probably never know how it actually works
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aTao
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Re: Black Holes

Sat Feb 28, 2015 10:36 pm

Nahh. they're all wrong.

Consider the billiard table model of space where massive objects are represented by depressions. Whilst light is affected by the curvature of the surface, because it has no mass and the wells in the surface are only depressions and not some kind of rip or bubble then light will always be able to escape. Maybe a fault of the model but more of the way massive objects affect the surface.
Consider that mass causes a low pressure under the surface rather instead of being a weight on top, then, just like an elastic membrane over a hole, when the pressure difference is great enough the surface forms a bubble. The bubble formation is normally a catastrophic event, past certain threshold progression is not steadily increasing but jumps. This event is the formation not only of a black hole, but also a new universe comprised of the material that forms the massive object.
There ya go, black holes and big bang all in one tidy package. Including the expanding universe isnt just material spreading out, but inclusion of more material as matter falls into the black hole.

And for my next trick: time is discrete,
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Re: Black Holes

Sun Mar 01, 2015 6:51 am

I thought you were about to say time is an illusion then.

....good grief, its the first of March already. How did that happen?

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Re: Black Holes

Sun Mar 01, 2015 10:23 am

[quote="morphy_richards"
....good grief, its the first of March already. How did that happen?[/quote]

Time is an illusion.
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Mandrewpi
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Re: Black Holes

Mon Mar 02, 2015 5:42 am

When we find out how gravity works well find out how black holes work. My theory is that they are basically spaces garbage service cleaning up space junk. I, being only a teenager, have spent a lot of time thinking about things like this and have figured that their gravitational pull is so strong due to their density,which I also believe is where gravity comes from,. Oddly after they suck in all of the space junk it just spews it out, instead of getting denser, but fast enough to escape it's pull for a while.
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Re: Black Holes

Mon Mar 02, 2015 5:51 am

I also believe if there are many universes they would not be identical but like how a galaxy is to the universe or solar systems to a galaxy or a planet to a solar system. I've also heard time travel only to the future is possible by going somehow faster than light to somewhere and back again which was tested in a particle accelerator.
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RaTTuS
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Re: Black Holes

Mon Mar 02, 2015 8:41 am

Burngate wrote:
RaTTuS wrote:I though they only had
mass , rotation and circumference [not radius]
... and charge.
I wrote:Short story by Asimov? Clarke? Heinlein?
Niven, The Hole Man, 1975
aha yes Charge ....

yeah this was after Larry Niven and Jerry Pournelle had been to see Stephen Hawking give a talk about black holes
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mrpi64
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Re: Black Holes

Fri Mar 06, 2015 1:29 pm

dan3008 wrote:
bertwert wrote: Doesn't a supernova collapse into either a black hole or neutron star?
no... a super nova is when a star reaches the end of its life and blows up, while a black hole collapses in on itself.

Neutron stars on the other hand, are the left over star after a supernova :)

Or thats what my astronomy teacher taught us...
Neutron stars can still turn into black holes, can't they?
I'm happy to help.
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kusti8
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Re: Black Holes

Fri Mar 06, 2015 1:42 pm

mrpi64 wrote:
dan3008 wrote:
bertwert wrote: Doesn't a supernova collapse into either a black hole or neutron star?
no... a super nova is when a star reaches the end of its life and blows up, while a black hole collapses in on itself.

Neutron stars on the other hand, are the left over star after a supernova :)

Or thats what my astronomy teacher taught us...
Neutron stars can still turn into black holes, can't they?
Yes, that's what I believe.
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