Free planetarium

 
A-L-E-X
Pioneer
Pioneer
Posts: 378
Joined: 06 Mar 2017

Science and Astronomy Questions

10 Aug 2017 01:23

That's very intriguing!  I also find "ring singularities" interesting because you can describe them as going from one universe to another (there are two event horizons to be "crossed"- a cauchy horizon and the traditional event horizon.)  With really large black holes, you could avoid getting crushed because they are spread across a much larger volume.  So you might actually survive long enough to get across both horizons, but what happens beyond that point? Who knows except those who make it......
 
User avatar
Watsisname
Science Officer
Science Officer
Posts: 738
Joined: 06 Sep 2016
Location: Bellingham, WA

Science and Astronomy Questions

10 Aug 2017 01:42

Yeah, Kerr's metric is extremely interesting, but we have to be careful about what parts of it to take seriously.  Everything about the exterior and the rotational effects on the surrounding space-time appear to be correct.  The metric does contain a ring singularity and a passage to another universe, but those are almost certainly not real.  Rather, they are a consequence of the Kerr vacuum solution (which begins by assuming all the mass is contained at the center) not being a valid description of the interior.  

A signal of this failure is that it predicts material falling into the black hole will violently pile up at the inner event horizon, which then contradicts the starting assumption that all the mass is at the center.  Similarly, the "wormhole" in this metric is also valid only as long as the space-time is empty.  As soon as you introduce any mass-energy to it, it breaks down with this violent pile-up of stuff at the inner horizon.

So whatever actually happens in a real rotating black hole must be different, and is almost definitely completely lethal.  I would NOT try to journey into one -- except in Space Engine. :P
 
A-L-E-X
Pioneer
Pioneer
Posts: 378
Joined: 06 Mar 2017

Science and Astronomy Questions

10 Aug 2017 01:56

Watsisname wrote:
Yeah, Kerr's metric is extremely interesting, but we have to be careful about what parts of it to take seriously.  Everything about the exterior and the rotational effects on the surrounding space-time appear to be correct.  The metric does contain a ring singularity and a passage to another universe, but those are almost certainly not real.  Rather, they are a consequence of the Kerr vacuum solution (which begins by assuming all the mass is contained at the center) not being a valid description of the interior.  

A signal of this failure is that it predicts material falling into the black hole will violently pile up at the inner event horizon, which then contradicts the starting assumption that all the mass is at the center.  Similarly, the "wormhole" in this metric is also valid only as long as the space-time is empty.  As soon as you introduce any mass-energy to it, it breaks down with this violent pile-up of stuff at the inner horizon.

So whatever actually happens in a real rotating black hole must be different, and is almost definitely completely lethal.  I would NOT try to journey into one -- except in Space Engine. :P

Wat, what do you think of the idea of baby universes being created inside black holes- black hole cosmology, in other words?  I think Lee Smolin is a big proponent of it ("Fecund Universes") and others have stated that that black hole cosmology might have a big role to play in finally unifying relativity and quantum mechanics (like Poplawski- who theorized that our own universe was created in this way inside a larger universe, ad infinitum.)  Also, what would it be like inside the ring of a ring singularity?  Would there be a gravitational center of calm- like you see inside the eye of a hurricane?  Would some equivalent to the centrifugal force push the most intense gravitation towards the "wall" of the ring while keeping the exact center "calm?"  Could it be that there initially is a passage to another universe there but the connection closes off as soon as matter piles up, but the baby universe remains on the other side- with its "umbilical cord" cut off?  Perhaps this is what happened to our universe too, allowing it to grow completely independently of its "parent."  That seems the most likely solution at this time.

https://en.wikipedia.org/wiki/Kerr_metr ... _wormholes
Although the Kerr solution appears to be singular at the roots of Δ = 0, these are actually coordinate singularities, and, with an appropriate choice of new coordinates, the Kerr solution can be smoothly extended through the values of {\displaystyle r} r corresponding to these roots. The larger of these roots determines the location of the event horizon, and the smaller determines the location of a Cauchy horizon. A (future-directed, time-like) curve can start in the exterior and pass through the event horizon. Once having passed through the event horizon, the {\displaystyle r} r coordinate now behaves like a time coordinate, so it must decrease until the curve passes through the Cauchy horizon.[20]

The region beyond the Cauchy horizon has several surprising features. The {\displaystyle r} r coordinate again behaves like a spatial coordinate and can vary freely. The interior region has a reflection symmetry, so that a (future-directed time-like) curve may continue along a symmetric path, which continues through a second Cauchy horizon, through a second event horizon, and out into a new exterior region which is isometric to the original exterior region of the Kerr solution. The curve could then escape to infinity in the new region or enter the future event horizon of the new exterior region and repeat the process. This second exterior is sometimes thought of as another universe. On the other hand, in the Kerr solution, the singularity is a ring, and the curve may pass through the center of this ring. The region beyond permits closed time-like curves. Since the trajectory of observers and particles in general relativity are described by time-like curves, it is possible for observers in this region to return to their past.[12][13]

https://en.wikipedia.org/wiki/Kerr_metric#cite_note-visser13-13
 
User avatar
Watsisname
Science Officer
Science Officer
Posts: 738
Joined: 06 Sep 2016
Location: Bellingham, WA

Science and Astronomy Questions

10 Aug 2017 02:42

A-L-E-X wrote:
Source of the post Wat, what do you think of the idea of baby universes being created inside black holes- black hole cosmology, in other words?

I've read about it, and I think it's a totally crazy idea -- possibly just crazy enough to be true. :)  I'm very enamored with it.  But, like always, it must make testable predictions for us to take it very seriously, and Poplawski's original presentation begins by making some untested assumptions, and it leads to difficult to test predictions.  In the absence of supporting evidence it is much more likely to be wrong than right.

A-L-E-X wrote:
Source of the post Also, what would it be like inside the ring of a ring singularity?  Would there be a gravitational center of calm- like you see inside the eye of a hurricane?

In the mathematically extended Kerr metric, probably not.  Nearby in-falling geodesics still deviate there, which means strong tidal forces, though not infinitely strong since it isn't a curvature singularity.  We might imagine it being a survivable passage to the other region of space-time.

In a real Kerr black hole, definitely not.  Remember, the location r<0 is a mathematical extension to the Kerr metric, and we must conclude it is unphysical.  In particular, this space-time is violently unstable, and it will not form in nature.  It's like describing a river which goes over a cliff as a waterfall and then smoothly flows back up the other side of the canyon.  Easy to describe mathematically, and you can say it obeys conservation laws, too.  But it never happens.

Here's a good, mathematically rigorous discussion of the features of the Kerr metric if you're interested. :)

https://arxiv.org/pdf/0706.0622.pdf

I like to emphasize this paragraph though:

However you should not physically trust in the inner horizon or the inner
ergosurface. Although they are certainly there as mathematical solutions
of the exact vacuum Einstein equations, there are good physics reasons to
suspect that the region at and inside the inner horizon, which can be shown
to be a Cauchy horizon, is grossly unstable — even classically — and unlikely
to form in any real astrophysical collapse.
 
A-L-E-X
Pioneer
Pioneer
Posts: 378
Joined: 06 Mar 2017

Science and Astronomy Questions

10 Aug 2017 02:47

Watsisname wrote:
A-L-E-X wrote:
Source of the post Wat, what do you think of the idea of baby universes being created inside black holes- black hole cosmology, in other words?

I've read about it, and I think it's a totally crazy idea -- possibly just crazy enough to be true. :)  But, like always, it must make testable predictions for us to take it very seriously, and Poplawski's original presentation begins by making some untested assumptions, and it leads to difficult to test predictions.  In the absence of supporting evidence it is much more likely to be wrong than right.

A-L-E-X wrote:
Source of the post Also, what would it be like inside the ring of a ring singularity?  Would there be a gravitational center of calm- like you see inside the eye of a hurricane?

In the mathematically extended Kerr metric, probably not.  Nearby in-falling geodesics still deviate there, which means strong tidal forces, though not infinitely strong since it isn't a curvature singularity.  We might imagine it being a survivable passage to the other region of space-time.

In a real Kerr black hole, definitely not.  Remember, the location r<0 is a mathematical extension to the Kerr metric, and we must conclude it is unphysical.  In particular, this space-time is violently unstable, and it will not form in nature.  It's like describing a river which goes over a cliff as a waterfall and then smoothly flows back up the other side of the canyon.  Easy to describe mathematically, and you can say it obeys conservation laws, too.  But it never happens.

Here's a good, mathematically rigorous discussion of the features of the Kerr metric if you're interested. :)

https://arxiv.org/pdf/0706.0622.pdf

I like to emphasize this paragraph though:

However you should not physically trust in the inner horizon or the inner
ergosurface. Although they are certainly there as mathematical solutions
of the exact vacuum Einstein equations, there are good physics reasons to
suspect that the region at and inside the inner horizon, which can be shown
to be a Cauchy horizon, is grossly unstable — even classically — and unlikely
to form in any real astrophysical collapse.


Thanks I am reading it now!  Does this mean that the actual baby universe would be unlikely to form or that it could still form but the connection to it would be destroyed as soon as it was created, leaving us no way to access it?  I like your description about the waterfall- I also saw one where it was described as trying to balance a pencil on its point, mathematically possible, but almost impossible in reality.

Also, on another matter, what is this "dark flow" that is supposed to exist near the edge of the observable universe?
 
User avatar
JackDole
Pioneer
Pioneer
Posts: 414
Joined: 02 Nov 2016
Location: Terra

Science and Astronomy Questions

10 Aug 2017 02:58

A-L-E-X wrote:
Source of the post One other thing, is there a way for me to make this my default screen on start up?

When you quit SpaceEngine at this position, it will start at the same location next time.
But in the next version, it will be possible to start SpaceEngine with a script. Then you can always return to this position at the beginning of a session.
 
User avatar
Watsisname
Science Officer
Science Officer
Posts: 738
Joined: 06 Sep 2016
Location: Bellingham, WA

Science and Astronomy Questions

10 Aug 2017 03:07

Does this mean that the actual baby universe would be unlikely to form or that it could still form but the connection to it would be destroyed as soon as it was created, leaving us no way to access it?


Good question!  It is beyond my ability to answer, but I'll leave you with two more papers which go into details of the physics of real rotating black hole interiors, and the most amazing concluding paragraph I've ever seen in an academic paper. :)

https://arxiv.org/pdf/1010.1269.pdf

https://arxiv.org/pdf/1108.3512.pdf

Prior to hitting the Planck wall, inflation acts like a particle accelerator of extraordinary power. It appears inescapable that Nature is conducting vast numbers of collision experiments over a broad range of peri- and super-Planckian energies in large numbers of black holes throughout our Universe. Does Nature do anything interesting with this extravagance – such as create baby universes – or is it merely a final hurrah en route to nothingness?
 
A-L-E-X
Pioneer
Pioneer
Posts: 378
Joined: 06 Mar 2017

Science and Astronomy Questions

10 Aug 2017 03:29

JackDole wrote:
A-L-E-X wrote:
Source of the post One other thing, is there a way for me to make this my default screen on start up?

When you quit SpaceEngine at this position, it will start at the same location next time.
But in the next version, it will be possible to start SpaceEngine with a script. Then you can always return to this position at the beginning of a session.

Thanks, Jack- is there a way to save the limiting magnitude I want to set in the console?
Also, is there a quick way (single or double keystroke) to move around the panoramic image without having to use the mouse?  My horizons get crooked very easily and it takes me a long time to straighten them.  I wish there was a single or double keystroke for that too.
 
A-L-E-X
Pioneer
Pioneer
Posts: 378
Joined: 06 Mar 2017

Science and Astronomy Questions

10 Aug 2017 03:32

Watsisname wrote:
Does this mean that the actual baby universe would be unlikely to form or that it could still form but the connection to it would be destroyed as soon as it was created, leaving us no way to access it?


Good question!  It is beyond my ability to answer, but I'll leave you with two more papers which go into details of the physics of real rotating black hole interiors, and the most amazing concluding paragraph I've ever seen in an academic paper. :)

https://arxiv.org/pdf/1010.1269.pdf

https://arxiv.org/pdf/1108.3512.pdf

Prior to hitting the Planck wall, inflation acts like a particle accelerator of extraordinary power. It appears inescapable that Nature is conducting vast numbers of collision experiments over a broad range of peri- and super-Planckian energies in large numbers of black holes throughout our Universe. Does Nature do anything interesting with this extravagance – such as create baby universes – or is it merely a final hurrah en route to nothingness?


Wow, either way, a black hole seems to be a good scaled-down analog of the universe.  The funny thing is, I read something similar before, about the universe being one vast particle collider and nature (or possibly some higher alien being in another universe that created us) conducting experiments in our universe just to satisfy their own curiosity.  And then we have the whole Holographic Principle to consider (which also connects well with black holes.)
 
User avatar
JackDole
Pioneer
Pioneer
Posts: 414
Joined: 02 Nov 2016
Location: Terra

Science and Astronomy Questions

10 Aug 2017 04:40

A-L-E-X wrote:
Source of the post Also, is there a quick way (single or double keystroke) to move around the panoramic image without having to use the mouse?  My horizons get crooked very easily and it takes me a long time to straighten them.

You can align the horizon with the End key.
With Numpad 4 and Numpad 6, you can look around. With Numpad 8 you can look up, with Numpad 2 down. Numlock must be activated.
Maybe you should look at the keyboard controls. You can call them with F8.
 
A-L-E-X
Pioneer
Pioneer
Posts: 378
Joined: 06 Mar 2017

Science and Astronomy Questions

10 Aug 2017 04:42

JackDole wrote:
A-L-E-X wrote:
Source of the post Also, is there a quick way (single or double keystroke) to move around the panoramic image without having to use the mouse?  My horizons get crooked very easily and it takes me a long time to straighten them.

You can align the horizon with the End key.
With Numpad 4 and Numpad 6, you can look around. With Numpad 8 you can look up, with Numpad 2 down. Numlock must be activated.
Maybe you should look at the keyboard controls. You can call them with F8.

Thanks for all your help Jack!  I've been busy memorizing all the keyboard commands you mentioned.  I didn't know there was an easy way to call them up!
If I want to have a different default Mag limit can I edit that in the console somehow?  I want to set it to 8.5
 
User avatar
JackDole
Pioneer
Pioneer
Posts: 414
Joined: 02 Nov 2016
Location: Terra

Science and Astronomy Questions

10 Aug 2017 04:55

A-L-E-X wrote:
Source of the post If I want to have a different default Mag limit can I edit that in the console somehow?

You can change the values for PlanetMagnLimit, StarMagnLimit and GalaxyMagnLimit in the main-user.cfg.
 
A-L-E-X
Pioneer
Pioneer
Posts: 378
Joined: 06 Mar 2017

Science and Astronomy Questions

10 Aug 2017 05:05

JackDole wrote:
A-L-E-X wrote:
Source of the post If I want to have a different default Mag limit can I edit that in the console somehow?

You can change the values for PlanetMagnLimit, StarMagnLimit and GalaxyMagnLimit in the main-user.cfg.

Thanks, sounds like I will be doing a bit of .cfg file editing for max FOV and mag limits.
Trying not to increase them too much though because I see that increases CPU usage (I want to keep CPU usage below 50%).

I think I asked this before, but I'm not sure, is this the only file I need to save a copy of elsewhere so I can keep all my preferences saved for when the next version comes out?  Will this also save my graphics and display settings?
 
Mr. Missed Her
Observer
Observer
Posts: 12
Joined: 09 May 2017

Science and Astronomy Questions

10 Aug 2017 13:44

About black holes, is it possible there's not actually a singularity - no infinitely dense point - to black holes? From my understanding of relativity and time dilation, time gets slower and slower as the gravity's escape velocity grows closer and closer to c, meaning that nothing can pass through the event horizon by themselves. The only way to get on the inside of an event horizon is to add more mass to a black hole, which would also pile up on the event horizon while not passing it, and might not actually contribute to the horizon. Also, inside of the event horizon, would time travel backwards? Because I believe that time travel to the past is extremely paradoxical and therefore impossible, I'm starting to doubt that even event horizons actually exist.

Now, I am quite possibly wrong, since my understanding of Einsteinian relativity and quantum mechanics is small. Sadly, no high school that I know of offers those courses. Although if my understanding is correct, there should be this interesting result: black holes have holes inside. They're bubbles!
 
A-L-E-X
Pioneer
Pioneer
Posts: 378
Joined: 06 Mar 2017

Science and Astronomy Questions

10 Aug 2017 13:53

Mr. Missed Her wrote:
About black holes, is it possible there's not actually a singularity - no infinitely dense point - to black holes? From my understanding of relativity and time dilation, time gets slower and slower as the gravity's escape velocity grows closer and closer to c, meaning that nothing can pass through the event horizon by themselves. The only way to get on the inside of an event horizon is to add more mass to a black hole, which would also pile up on the event horizon while not passing it, and might not actually contribute to the horizon. Also, inside of the event horizon, would time travel backwards? Because I believe that time travel to the past is extremely paradoxical and therefore impossible, I'm starting to doubt that even event horizons actually exist.

Now, I am quite possibly wrong, since my understanding of Einsteinian relativity and quantum mechanics is small. Sadly, no high school that I know of offers those courses. Although if my understanding is correct, there should be this interesting result: black holes have holes inside. They're bubbles!

That's exactly what Lee Smolin was talking about- bubble universes.

Who is online

Users browsing this forum: Watsisname and 2 guests