Gnargenox wrote:

Source of the post Any plans to include black rings in Space Engine?

Gnargenox wrote:

Source of the post What would happen if I wrote a script with a black hole inside another black hole?

Gnargenox wrote:

Source of the post A Black Hole in 3D is a sphere, but in 4D Spacetime, is it a cylinder or a black torus ring with a black hole in the middle?

► Take the blue pill

You learn that a Schwarzschild black hole is spherical in 3D, and traces a cylinder in space time.   At one end of the cylinder is its birth by gravitational collapse.  The other end tapers down to a point by its slow evaporation by Hawking radiation, with a final burst of gamma rays marking its death.

(From Gravitation by Misner, Thorne, and Wheeler, aka "MTW")

► Take the red pill

You take a stroll through the space-time geometries of spinning black holes, in their mathematically extended and idealized forms (which do not correspond to nature, but make for an interesting adventure in Wonderland nevertheless).

In the Kerr metric describing a spinning black hole, the singularity is turned to a ring, the event horizon splits in two, and the space around the hole gets dragged around as if caught in a whirlpool.  But what happens to the (well equipped) person who falls into the black hole along its polar axis, passing straight down through the middle of the ring singularity?  Where do they go?  

The answer is astonishing.  Passing through the center of the ring singularity takes them to a different place than if they instead went around it.  The flat disk within the ring singularity acts exactly like a portal in space.  The spatial coordinate describing this region has a negative value for radius, so some refer to it as "negative space".  There is nothing terribly weird about it besides the name.  The negative space extends infinitely far, and becomes quite normal (flat space-time; no strong tidal forces or gravitational field) the farther into it you go.  But there is a barrier to entry.  If you fall into the black hole too slowly (not enough energy), then you slow down and "bounce" back shortly after passing into the negative space.  It is as if there is an effective potential hill to climb over.  To cross it and explore the infinite space inside, you must fall in with very fast speeds bordering on the relativistic.  The black hole as seen from inside this negative space appears like a naked singularity.   

So here we find our first region of space-time to add to our map.  An infinite region, that is accessed by passing through the ring singularity.

What happens if we don't enter the negative space with enough energy, and fall out of it and back through the ring singularity again from that side?  Do we end up back in the original spinning black hole's interior?

No.  The rabbit hole goes deeper.

Passing through the singularity again, we end up falling into yet another universe worth of space-time.  Looking back, the black hole now appears to be a white hole, and we cannot re-enter it.  

In fact, there are an infinite number of infinitely large regions of space-time hidden inside this "mathematically extended vacuum solution" of the rotating black hole.  Each region is accessed by a different choice in path (which direction you fall in from, how fast you go, and any accelerations you might make, perhaps by firing your thrusters).  We can visualize these regions schematically by plotting them on a Penrose Diagram:

Penrose Diagram of the extended Kerr metric

(Image from jila.colorado.edu)

What would the (again, unrealistic/idealized) journey look like?  We can view a simulated view of passing through something similar: the extended solution of an electrically charged black hole, which has a similar interior structure with a passage through a wormhole and out of a white hole into another universe on the other end.  The simulation was made by Andrew Hamilton -- video here, and Andrew's description of what's going on here.

I have also found simulations for falling into and "through" Kerr black holes specifically.  These were made by David Madore who also has a great website about black holes.   Rather than showing a background starfield in his visualizations, he renders colored grids on relevant surfaces (like the background space, and event horizons).  The effect is rather psychedelic.  

Diving through the ring singularity and ending up in negative space.

(Blue = background space of universe, red/brown = outer event horizons, green = inner event horizons, purple = background of negative space.)

Passing through the white hole and into a parallel universe.

I reiterate again that this is all mathematical abstraction.  What would the real thing be like?  Basically identical as you pass through the outer event horizon and probably most of the way to the inner horizon, but then you hit a wall of infinite density along with an infinitely bright flash of light as you see the whole history of the universe since the black hole's formation.  This is sometimes called the mass inflation singularity, and it's very nasty and not recommended.

Watsisname wrote:

How far down the rabbit hole do you want to go?

► Take the red pill

You take a stroll through the space-time geometries of spinning black holes, in their mathematically extended and idealized forms (which do not correspond to nature, but make for an interesting adventure in Wonderland nevertheless).

In the Kerr metric describing a spinning black hole, the singularity is turned to a ring, the event horizon splits in two, and the space around the hole gets dragged around as if caught in a whirlpool.  But what happens to the (well equipped) person who falls into the black hole along its polar axis, passing straight down through the middle of the ring singularity?  Where do they go?  

The answer is astonishing.  Passing through the center of the ring singularity takes them to a different place than if they instead went around it.  The flat disk within the ring singularity acts exactly like a portal in space.  The spatial coordinate describing this region has a negative value for radius, so some refer to it as "negative space".  There is nothing terribly weird about it besides the name.  The negative space extends infinitely far, and becomes quite normal (flat space-time; no strong tidal forces or gravitational field) the farther into it you go.  But there is a barrier to entry.  If you fall into the black hole too slowly (not enough energy), then you slow down and "bounce" back shortly after passing into the negative space.  It is as if there is an effective potential hill to climb over.  To cross it and explore the infinite space inside, you must fall in with very fast speeds bordering on the relativistic.  The black hole as seen from inside this negative space appears like a naked singularity.   

So here we find our first region of space-time to add to our map.  An infinite region, that is accessed by passing through the ring singularity.

What happens if we don't enter the negative space with enough energy, and fall out of it and back through the ring singularity again from that side?  Do we end up back in the original spinning black hole's interior?

No.  The rabbit hole goes deeper.

Passing through the singularity again, we end up falling into yet another universe worth of space-time.  Looking back, the black hole now appears to be a white hole, and we cannot re-enter it.  

In fact, there are an infinite number of infinitely large regions of space-time hidden inside this "mathematically extended vacuum solution" of the rotating black hole.  Each region is accessed by a different choice in path (which direction you fall in from, how fast you go, and any accelerations you might make, perhaps by firing your thrusters).  We can visualize these regions schematically by plotting them on a Penrose Diagram:

Penrose Diagram of the extended Kerr metric

(Image from jila.colorado.edu)

What would the (again, unrealistic/idealized) journey look like?  We can view a simulated view of passing through something similar: the extended solution of an electrically charged black hole, which has a similar interior structure with a passage through a wormhole and out of a white hole into another universe on the other end.  The simulation was made by Andrew Hamilton -- video here, and Andrew's description of what's going on here.

I have also found simulations for falling into and "through" Kerr black holes specifically.  These were made by David Madore who also has a great website about black holes.   Rather than showing a background starfield in his visualizations, he renders colored grids on relevant surfaces (like the background space, and event horizons).  The effect is rather psychedelic.  

Diving through the ring singularity and ending up in negative space.

(Blue = background space of universe, red/brown = outer event horizons, green = inner event horizons, purple = background of negative space.)

Passing through the white hole and into a parallel universe.

I reiterate again that this is all mathematical abstraction.  What would the real thing be like?  Basically identical as you pass through the outer event horizon and probably most of the way to the inner horizon, but then you hit a wall of infinite density along with an infinitely bright flash of light as you see the whole history of the universe since the black hole's formation.  This is sometimes called the mass inflation singularity, and it's very nasty and not recommended.

Stellarator wrote:

Source of the post Personally, I find the quality and informative nature of the project's aims and results unsurpassed.

Watsisname wrote:

Source of the post Formation of a galaxy cluster rendered by gas velocity, then switching to visible light.
Formation of a single spiral galaxy similar to M31.