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What If's About the Universe

BenHad

Student
BenHad
Joined
Jan 24, 2008
Messages
36
I would like to use this thread to have readers consider various "what if's" I have in mind about the universe and black holes. This is about pure speculation.

Please bear in mind I'm only a layman when it comes to cosmology, astrophysics, etc.. I have a BA in Math from UCLA, with a minor in Physics. But my physics classes were back in the late 50's and early 60's. Quarks were unknown when I took Atomic and Nuclear Physics back in the late 50's. But I think the concept of the Big Bang was around. Please correct me if this is wrong. My career was Software Engineer, Senior Technical Specialist, at McDonnell Douglas. I worked with big scientific computers and their operating system software, including machine language coding, for many years before going into applications programming using Fortran. I read Science News weekly.

My 1st What If's (remember, this is about speculation, not proving anything):
What might happen if a black hole (and it's galaxie) has accumulated such a mass that it's gravitational field begins to attract other galaxies (and their black holes)? Would these other galaxies eventually be drawn into this black hole? Could this one black hole, over billions (or trillions of years) gobble up all the other galaxies? Would dark matter/energy be drawn to this black hole?

What do you think?
 
BenHad said:
My 1st What If's (remember, this is about speculation, not proving anything):
What might happen if a black hole (and it's galaxie) has accumulated such a mass that it's gravitational field begins to attract other galaxies (and their black holes)? Would these other galaxies eventually be drawn into this black hole? Could this one black hole, over billions (or trillions of years) gobble up all the other galaxies? Would dark matter/energy be drawn to this black hole?
Click to expand...

Yes.
 
BenHad said:
My 1st What If's (remember, this is about speculation, not proving anything):
What might happen if a black hole (and it's galaxie) has accumulated such a mass that it's gravitational field begins to attract other galaxies (and their black holes)? Would these other galaxies eventually be drawn into this black hole? Could this one black hole, over billions (or trillions of years) gobble up all the other galaxies? Would dark matter/energy be drawn to this black hole?

What do you think?
Click to expand...

Inasmuch as nearly all galaxies have giant black holes in their centers, that's what is currently happening in the various galaxy groups (including the local group). Galaxies merge, becoming large elliptical galaxies, and black holes wind up orbiting each other inside the center of such a galaxy, eventually merging themselves. Of course, such a galaxy now has increased mass, and so attracts other galaxies more vociferously. I don't think any but the occasional star fall into the black hole(s) in the center of a galaxy; mostly interstellar dust falls in.
 
  • Keep in mind that, in the universe we observe, everything started off moving apart. The gravitational attraction of a super-mass has to overcome the primordial expansion; this is hard.
  • If the Milky Way collapsed into a black hole, would it speed up the capture of Andromeda? No, not at all. Andromeda is attracted to the Milky Way's total mass. It doesn't care whether it's falling towards one trillion individual stars, or towards a single trillion-solar-mass black hole.
  • For the most part, the large-scale structure of the universe is probably done coalescing. A galaxy could, concievably, pull together into one black holes---with the caveat that it would have to do so by ejecting high-angular-momentum stars or gas. There are many clusters of multiple galaxies that could do the same. There are superclusters, consisting of several galaxy clusters, that could also collapse into smaller structures. But there isn't another level beyond that. The superclusters are already too far apart, and moving further apart in the Hubble flow too fast for gravitational attraction to stop them. So the largest black hole you could get would be the mass of the largest present-day supercluster.
 
Check out "Universe Today" and "Astronomy Cast" with Pamela Gay and Fraser Cain, podcasts. These are very good and up to date.
 
ben m said:
  • For the most part, the large-scale structure of the universe is probably done coalescing. A galaxy could, concievably, pull together into one black holes---with the caveat that it would have to do so by ejecting high-angular-momentum stars or gas. There are many clusters of multiple galaxies that could do the same. There are superclusters, consisting of several galaxy clusters, that could also collapse into smaller structures. But there isn't another level beyond that. The superclusters are already too far apart, and moving further apart in the Hubble flow too fast for gravitational attraction to stop them. So the largest black hole you could get would be the mass of the largest present-day supercluster.
Click to expand...

Thanks ben m.
Ok, it's been a while since I looked at the effect of gravity over distance. So it decreases by the Inverse Square Law and most galaxies have "escape velocity" relative to other galaxies. Learning is occurring. :eye-poppi
 
BenHad said:
Thanks ben m.
Ok, it's been a while since I looked at the effect of gravity over distance. So it decreases by the Inverse Square Law and most galaxies have "escape velocity" relative to other galaxies. Learning is occurring. :eye-poppi
Click to expand...

It's always good to notice that if the Sun were to turn into a Black Hole of its same mass the orbit of the Earth would not change. Outside the event horizon, a black hole has the same gravitational effect as a star.
 
Knowlege is Growing

Olowkow said:
Check out "Universe Today" and "Astronomy Cast" with Pamela Gay and Fraser Cain, podcasts. These are very good and up to date.
Click to expand...

Thanks, Olowkow!

I've added both to my JREF Favorites. Actually added the main web sites and the podcast web sites for both.

There goes the next few years of my life - viewing all the material in these. :eek:

BenHad
 
Hmmmm

Yllanes said:
It's always good to notice that if the Sun were to turn into a Black Hole of its same mass the orbit of the Earth would not change. Outside the event horizon, a black hole has the same gravitational effect as a star.
Click to expand...

Apparently as solar systems are drawn closer to a galaxies black hole, the angular velocity of most increases such that they will not fall into the black hole. Must get crowded there, multiple collisions occurring, then dust which may be consumed by the black hole. Hmmm. :crowded:

Then maybe the solar systems will eventually be consumed. :wide-eyed

BenHad
 
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Next What If

What if the universe is of infinite size and infinite mass, with multiple areas experiencing Big Bangs? Would this imply that galaxies and supper glusters from surrounding much earlier big bangs could colide and form super black holes, or would we expect their relative velocities to preclude this? Over trillions and trillions of years, wouldn't large numbers of galaxies eventually have collided and combined?

It's easier for me to imagine such as this, and difficult for me to get a grip on String Theory.

BenHad :confused:
 
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