Black holes

[El_Gringo_Grande]

You know how black holes are usually depicted? They look like a cone.

Is that depiction done for simplicity's sake?

It seems to me that in 3D world the event horizon would completly surround the black hole.

And by the way. This weeks Nova was pretty good. Talked about super massive black holes. http://www.pbs.org/wgbh/nova/blackhole/

[Coridon]

They're spherical in shape. Super massive, super dense orbs.

There can be other shapes around the black hole, but those are either things being pulled in or, in the event that it tries to "ingest" too much at once, jets of matter spewing away from the black hole.

But the black hole itself is spherical.

[El_Gringo_Grande]

Ah, you bring up another question. Those jets they spew. They seem to come from "poles" (for lack of better term). Do black holes have poles? How could a infinitely dense mass have poles? And even if it did the magnetic field couldn't escape, right?

Ok, I assume the matter trying to get into the black hole somehow influences the fact that a cone of matter is being spewed and not a sphere.

Hmm. I have been searching for answers, even simple ones, for these questions and can't seem to find them.

Any body? Links or explanations appreciated.

[Rick_the_new_guy]

Originally Posted by Coridon

They're spherical in shape. Super massive, super dense orbs.

There can be other shapes around the black hole, but those are either things being pulled in or, in the event that it tries to "ingest" too much at once, jets of matter spewing away from the black hole.

But the black hole itself is spherical.

Holy Cow, you sound just like the scientist on Nova.

I found it awsome that each Galaxy has it's own black hole.

The Milky Way has some size but the nearst ( Andromeda Galaxy) is much larger and would own us if their gravitational fields started bringing the closer.


I really liked how they were able to take many small pictues of the orbits of stars as they slung shot around these black holes. Truly amazing stuff!!!!

[Kerostasis]

Are you referring to the line-web diagrams like the one in the background of that banner?

I can explain that. That is an attempt to display an additional feature not visible in 3-dimensional space. Properly displaying it would normally require 4 dimensions, or at least a visible representation of 4-dimensions, which is hard to wrap our heads around.

So instead of drawing a 3-dimensional space, the drawing only shows 2 dimensions of normal space, making a flat plane. The Black hole is not a cone (yet), but a circle in the middle. That circle is the 2-D equivalent of the 3-D real black hole. Then the extra feature (gravity-induced spatial warping, for those who care) is shown in the third dimension, bending the area around the black hole to create your familiar cone shape.

Does that make it clearer?

[El_Gringo_Grande]

Kerostasis

Yes it does. That is what I suspected, flattened the 3D to 2D then inflated it back to 3D by adding the dimension of time. Then represented all that in a 2D medium.

It isn't really that hard to imagine this in four dimensions, just very hard to depict it.

[Kerostasis]

Right, except in this case the 4th dimension isn't "time". Its a depiction of the extent to which the normal dimensions of space are actually stretched out by the large gravitational field of a black hole. So its just another spatial dimension.

In fact, if you were to make a similar diagram of any large object, like the Earth or the Sun, you would see a similar cone shape around it. Thats where the nickname "gravity well" came from, I think. The primary difference is that with a normal object like the sun, that cone has a bottom to it. It goes down a bit, then comes back up.

With a blackhole, the cone is bottomless. It hyperbolicly goes down all the way to infinity. Hence the description "a tear in the fabric of space". This desciption may or may not be physically correct, but it very well describes the results of a black hole on our force line diagram.

[Karkianman101]

Weird. I used that same image in my mind during Physics last year to try and justify how gravity works (mass spreads apart space, making it 'low density', and the 'high density' space around it forces objects in). I probably have the concept wrong, but at least I got the mental picture right :P