[Q] Gravitation Limit?

[Michael Mooney]

Freeztar:

Now, we bring in the a massive body (a 'neutron star'). It doesn't affect the people inside the spherical shell, or does it? Well, not directly...they are still floating around inside the spherical shell with no preferential gravitation. Nonetheless, their spherical shell is moving towards the 'neutron star'.

 

"But freeztar, this is not the way the universe works".

I agree!

 

If we can't "see" the 'neutron star', then it is not possible that it is acting on us, or the spherical shell for that matter.

 

What? Only what we can see can actually be happening?

This brings us back to subjective idealism, does it not?

 

In the real world, we observe (by infrared) stars near the center of our galaxy orbiting the SMBH there and then disappearing, obviously having been attracted to and sucked into the SMBH. A clear example of "spheres" (stars) being pulled into an SMBH by gravity.

How does this reconcile with your last statement above, Freeztar?

How could your neutron star *not* be attracting our sphere toward it?

But back to our sphere within a sphere...

Here is another exaggeration of my "extremely dense shell of matter" around a sphere of hydrogen gas. Say we minimize the distance between the two spheres to just a 'mimi-micron'r all around and make the outer shell as dense as a neutron star's matter. So the distance between a given hydrogen atom and a given micro-mote of neutron- star- density matter (at their closes point) is at near minimum and the force to distance ratio (for the square of the distance factor) is near maximum.

The super-dense "mote" still doesn't attract and unite with the hydrogen atom... all around?

 

Michael

[modest]

I've been thinking about this and it seems that the spherical shell reference only goes so far. Just throwing this out there for thoughts.

 

Say you hollow out a sphere and place people inside. Well, as has been shown, those people will have no gravitational preference for one side or the other.

 

Now, we bring in the a massive body (a 'neutron star'). It doesn't affect the people inside the spherical shell, or does it? Well, not directly...they are still floating around inside the spherical shell with no preferential gravitation. Nonetheless, their spherical shell is moving towards the 'neutron star'.

 

"But freeztar, this is not the way the universe works".

I agree!

 

If we can't "see" the 'neutron star', then it is not possible that it is acting on us, or the spherical shell for that matter.

 

And that's all she wrote.

 

But, this rule works only when the matter is arranged in a spherically symmetric way. If a person goes to the center of the sphere then there must be equal mass in every direction. Placing a single star outside the sphere breaks the spherical symmetry. In that situation the people would react to the star gravitationally as if the spherical shell were not there. They would fall toward the star. The spherical shell would not affect them gravitationally, but the star certainly would.

 

~modest

[modest]

Here is another exaggeration of my "extremely dense shell of matter" around a sphere of hydrogen gas. Say we minimize the distance between the two spheres to just a 'mimi-micron'r all around and make the outer shell as dense as a neutron star's matter. So the distance between a given hydrogen atom and a given micro-mote of neutron- star- density matter (at their closes point) is at near minimum and the force to distance ratio (for the square of the distance factor) is near maximum.

The super-dense "mote" still doesn't attract and unite with the hydrogen atom... all around?

The transition happens when the hydrogen atom crosses the shell's boundary. Once it penetrates the shell it will feel the shell's mass beneath it and want to fall back into the cavity. The shell itself is gravitationally attracted toward it's own center. If you want to get technical, nothing inside the shell is attracted in any direction by the shell no matter how close to a wall it gets, but the instant the particle crosses the wall of the shell then it will want to fall back into the cavity.

 

~modest

[Michael Mooney]

The transition happens when the hydrogen atom crosses the shell's boundary. Once it penetrates the shell it will feel the shell's mass beneath it and want to fall back into the cavity. The shell itself is gravitationally attracted toward it's own center. If you want to get technical, nothing inside the shell is attracted in any direction by the shell no matter how close to a wall it gets, but the instant the particle crosses the wall of the shell then it will want to fall back into the cavity.

 

~modest

I don't get "crosses the shell's boundary" or "penetrates the shell" or "feels the shell's mass beneath it."

 

If the inner hydrogen shell is as close as possible to the neutron-star-matter shell without actually uniting with it... (distance factor at minimum) and massiveness factor of outer shell at maximum, then what is to keep each compact neutron mass from attracting and uniting with each hydrogen atom all around?

 

Am I just as dense as "the outer shell?"

 

On another note... I had not intended to present a cosmology with shells of matter as precisely defined as this whole sphere-within-a-sphere thing that has developed, tho it illustrated the principle... in perhaps too precise and defined a way.

 

If you all review my "cosmic jugging act" cosmology in the now closed "Bang/Crunch Revisited" thread (y'all were quick on the trigger to close my last two threads) you may be able to "envision" with me a more spread out scenario of "outgoing Bangs" and "incoming Crunches" which are not so well defined as the spheres we have been talking about above. Would this make any difference assuming the matter beyond out "sphere of visibility"... whether still outgoing or now incoming... is not so evenly distributed as perfectly spherical shells? Say billions of supermassive black holes beyond our horizon are coalescing into colossally massive black holes all around our visible cosmos.

Are we absolutely sure that this would disturb the isotropic homogeneity we observe even if such gelled clumps of mass were more or less evenly distributed around our visible cosmos but not as a perfect sphere per se?

 

Michael

[modest]

I don't get "crosses the shell's boundary" or "penetrates the shell" or "feels the shell's mass beneath it."

 

I probably could have done better with that. :doh:

 

If the inner hydrogen shell is as close as possible to the neutron-star-matter shell without actually uniting with it... (distance factor at minimum) and massiveness factor of outer shell at maximum, then what is to keep each compact neutron mass from attracting and uniting with each hydrogen atom all around?

 

No matter how close each individual hydrogen atom is to the wall, the gravity from the dense shell will affect it such that there will be an equal force pulling it 1) toward the nearby wall and 2) toward the far wall. Since there will be an equal force pulling both directions they cancel. This is true no matter how close you get to any wall.

 

Drawing this, the red dots are the hydrogen shell and the black ring is the super-dense shell surrounding it:

The hydrogen shell is going to collapse toward its own center because it is not rigid. Each individual hydrogen atom is drawn toward all the other hydrogen atoms which are closer to the center than it is. So, for example, if a hydrogen atom is 100 km from the center of the sphere then it will be gravitationally attracted (in a way that doesn't cancel) toward each other hydrogen atom which is less than 100 km from the center. So, what about the black shell? The hydrogen atoms will act exactly the same in the picture above as they will act in this picture:

The hydrogen shell will collapse at the same speed and in the exact same way as before. Each and every hydrogen atom is closer to the center of the sphere than the black super-dense shell. No matter how close any individual hydrogen atom is to the walls of the black shell, the gravitational force due to that shell will cancel. So, the red part of both pictures does the same thing. As far as the hydrogen shell is concerned, the black shell is as if it isn't even there.

 

what is to keep each compact neutron mass from attracting and uniting with each hydrogen atom all around?

 

Perhaps you can think of it like this. Think of the dense neutron shell as a bunch of point masses. Instead of a solid ring, think of it being broken up into lots of individual masses like so:

where there's only one hydrogen atom (red) and it is inside a spherical ring of dense point masses (black) which are kept in place or kept rigid and unable to move by the blue wire. I'm only showing some of the ring, but you can imagine it keeps going all the way around.

 

Which direction do you think the red mass wants to move? The center of the red mass is clearly very near the center of the black mass right above it, so calculating the force in that direction would give a very strong force. It's pulled with slightly less force by the next black circle and slightly less again by the next black circle. Each of those pull the red hydrogen atom in a different direction. If you sum up all the forces and all the vectors it ends up with zero force. It doesn't want to go any direction. The black masses end up with zero net affect on the red mass.

 

It is true as you say that it is very near the mass directly above it. But, think about how many masses are above it—only about a half a dozen. The number of masses below it, albeit much further away, is a lot.

 

A force vector is a line you can draw on something which shows the force acting on it. The direction of the line shows the direction of the force and the length of the line shows the amount of force. This, for example, is being pulled left with twice the force that it is being pulled to the right:

The red object above will act the same as the red object below:

In other words, if you're pulling something left with 40 Newtons and pulling it right with 20 Newtons then you can subtract the vectors and say that it's being pulled left with 20 Newtons. Likewise, if something is being pulled left and right with the same force:

It will not move:

Going back to the point mass example, we can draw a force vector for each point mass. It's being pulled up with a lot of force, so it will have a long arrow pointing up. The arrows pointing down will be much smaller because the source of gravity causing those is much further away. But, there are a lot more arrows pointing down than pointing up. It would end up looking something like this:

If you account for all the forces and all the directions you end up with no force—just a red dot. With a mass in a spherically symmetric shell the vectors (casued by the shell) always cancel so that it is not accelerated at all. The relatively small amount of mass near the object being considered is offset by the relatively large amount of mass far away from the object in the other direction. In other words, the length of arrows pointing any given direction in 3 dimensions is equal to the length of arrows pointing in the opposite direction (less arrows pointing up which are longer and more arrows pointing down which are shorter).

 

As the red hydrogen atom gets closer to the wall of the cavity above it 2 things will happen:

1. The arrows pointing up will get longer and the arrows pointing down will get shorter.
   
2. The arrows pointing up will will get further apart (there will be less and less of them) and the arrows pointing down will get closer together (there will be more and more of them).
   

Because both of these things happen it doesn't matter how close the hydrogen atom gets to the wall, the forces will still cancel.

 

Without using trigonometry or calculus (or, indeed, any math), I don't think I would be able to explain this any better.

 

On another note... I had not intended to present a cosmology with shells of matter as precisely defined as this whole sphere-within-a-sphere thing that has developed, tho it illustrated the principle... in perhaps too precise and defined a way.

 

If you all review my "cosmic jugging act" cosmology in the now closed "Bang/Crunch Revisited" thread (y'all were quick on the trigger to close my last two threads) you may be able to "envision" with me a more spread out scenario of "outgoing Bangs" and "incoming Crunches" which are not so well defined as the spheres we have been talking about above. Would this make any difference assuming the matter beyond out "sphere of visibility"... whether still outgoing or now incoming... is not so evenly distributed as perfectly spherical shells? Say billions of supermassive black holes beyond our horizon are coalescing into colossally massive black holes all around our visible cosmos.

Are we absolutely sure that this would disturb the isotropic homogeneity we observe even if such gelled clumps of mass were more or less evenly distributed around our visible cosmos but not as a perfect sphere per se?

 

The thing is... our observation of the universe including observations of the expansion (the recession velocity) and the acceleration of expansion (speeding up of recession velocity) are isotropic. This means that whatever is affecting the accelerating expansion is caused by something isotropic. If you imagine something at the center of a sphere (like us at the center of our cosmic horizon) observing isotropy; it means we are observing spherical symmetry. Look at the first sphere drawn in this post. An observer at its center will see an equal amount of mass in every direction. That is spherical symmetry.

 

So, I don't see any way you could say that your model is not spherically symmetric. Saying that would mean it disagrees with observation.

 

Ok, hopefully this post makes more sense then my last :)

 

~modest

[Michael Mooney]

Modest:

The thing is... our observation of the universe including observations of the expansion (the recession velocity) and the acceleration of expansion (speeding up of recession velocity) are isotropic. This means that whatever is affecting the accelerating expansion is caused by something isotropic. If you imagine something at the center of a sphere (like us at the center of our cosmic horizon) observing isotropy; it means we are observing spherical symmetry. Look at the first sphere drawn in this post. An observer at its center will see an equal amount of mass in every direction. That is spherical symmetry.

 

So, I don't see any way you could say that your model is not spherically symmetric. Saying that would mean it disagrees with observation.

 

Ok, hopefully this post makes more sense then my last

 

Yes it does, and I thank you for your time and effort in spelling it out in such detail for me.

As I said earlier, my "sphere within a sphere" was a model I proposed to clarify how gravity works in concentric spherical configuration. I do now see what you mean as pertains to perfect spheres. Thank you.

 

Maybe this is not the place to pursue my more complex cosmology... "the cosmic juggling act" as I have called it. I asked more specifically about that at the end of my last post as "on another note." I don't at this point know where the "proper place" might be for that more complex cosmology, as my "bang/crunch revisited" thread has been closed prior to any response on the possibility that many 'colossally massive black holes" are outside our sphere of visibility pulling our cosmos outward as masses not so perfectly spherical as in all the above but still "more or less evenly distributed" beyond our horizon (itself not perfectly spherical tho isotropic in all directions.)

 

So, f you will, please abandon the metaphor of our perfectly spherical cosmos within a much larger perfectly spherical cosmos and allow the possibility that all of that is not so 'perfectly spherical.'

 

Is the above "impossible" if not so perfectly defined as concentric spheres? (This is not directed to you, Modest, as it is much more irregular that perfect spheres.)

 

Maybe this inquiry would require a reprieve or reopening of the prematurely closed "bang crunch" thread... or I could invent a substitute tile for the same cosmological inquiry... "Would a multiple bang and multiple crunch cosmology be possible?" ... if the outer unknown masses were extremely massive and distributed all around our cosmos in relatively regular but not perfectly spherical distribution?

 

Anyone here understand what I am proposing and asking? And with all due respect I ask that Modest and Boerseun *not* be the respondents to this inquiry.

(Modest is here all about spheres and Boerseun really wants to shut me down ASAP whatever it takes.)

Michael

[modest]

If you want to propose an alternative model of cosmology then you'd do best opening a thread in Alternative theories describing it.

 

I'll give you some advice. You'll want to include some predictions of the model even if they are trivial observations of the cosmos. Demonstrating the model's ability to model things we know and things that can be tested for is the first thing people look for.

 

~modest

[Erasmus00]

if the outer unknown masses were extremely massive and distributed all around our cosmos in relatively regular but not perfectly spherical distribution?

 

The problem with this is that its not perfectly isotropic. some patches of sky are different than other patches of sky (because some lines of sight will be on one of the regularly spaced masses, and some won't. Hence, there will be some deviation from isotropy, and we don't see this.

[freeztar]

The problem with this is that its not perfectly isotropic. some patches of sky are different than other patches of sky (because some lines of sight will be on one of the regularly spaced masses, and some won't. Hence, there will be some deviation from isotropy, and we don't see this.

 

Indeed.

 

I think WMAP did a good job of showing the CMBR isotropy.

 

 

The cosmic microwave temperature fluctuations from the 5-year WMAP data seen over the full sky. The average temperature is 2.725 Kelvin (degrees above absolute zero; equivalent to -270 C or -455 F), and the colors represent the tiny temperature fluctuations, as in a weather map. Red regions are warmer and blue regions are colder by about 0.0002 degrees.

WMAP Mission Results

[Michael Mooney]

Thanks to all of you for your patience in reply to my persistent inquiries and challenges.

Looks like *at present* the isotropic cosmos we observe precludes "matter out there" (beyond our range of vision) as causing an omni-directional gravitational force increasing our rate of expansion. It must be that extremely mysterious "dark matter" doing it... but giving it a name really doesn't make it "real" or confer understanding!

 

I emphasize "at present" for the following reason... first quoting Wiki on the "Big Crunch." (My bold)

 

...While the early universe was highly uniform, a contracting universe would become increasingly clumped. Eventually all matter would collapse into black holes, which would then coalesce producing a unified black hole or Big Crunch singularity.

 

So, also *while the present universe (cosmos) is highly uniform"... it may eventually reverse and become more like what I was describing, as above... tho the completed crunch as I see it would be a ball of all matter... (not a "singularity" of no volume and infinite mass density)... which would then, by whatever dynamic, again "go bang"... a perpetual cycle if it does not actually 'die of energy exhaustion'... see the recent thread on entropy... still in the debate phase.

 

If you then add the concept of "not all matter all at once" but phased bangs and crunches... with incoming and outgoing shells all happening all the time.... well, then you have "my little cosmology" which I already attempted to present in the Bang/Crunch Revisited thread and elsewhere. (So there is no need for a new thread on it.)

 

And it will be quite a few more billions of years before we can observe any verification which such a cosmology predicts.... like decreasing isotropy as big clumps of "incoming mass) attract our outgoing expansion unevenly.

Of course this is right up there with string/M-Theory for lack of verified predictability... tho most do consider the latter a legitimate scientific theory anyway. (Granted, some, like Boerseun, don't.)

Soooo...

Unless there is some response to the above requiring my reply, I will be taking an "extended leave" from participation here.

 

Again, thanks to all of you.

Michael