Galaxy orbital velocities explained without 'dark matter' halos.

N

nebel

Is it correct to say that the 'pulls' of gravity are zero at the 'center of mass' of an entity? and max at the surface/ perimeter?--- if this is so,
One would expect the highest orbital velocities at the perimeter of galaxies, spirals, globular or ellipticals with even mass distribution; and
the lowest speeds near the centers,- of at least of those accumulations without a great central mass.
Results may vary, because of mass density variations, or central black holes, but even there, in the very center, should gravity not fall to zero ? and with it the need for balancing gravity by centrifugal forces?
 
Last edited:
nebel said:
Is it correct to say that the 'pulls' of gravity are zero at the 'center of mass' of an entity? and max at the surface/ perimeter?--- if this is so,
Click to expand...
That would apply to a solid object. A diffuse matterial would not have the same attributes.
 
origin, could you explain why and how the action of gravity depends on whether an object is solid, a fluid, or particles?
BSW I like your avatar, the roar of an Atlas shakes every organ in your body.
 
origin, granted, diffuse entities might not have a 'surface' or a well defined perimeter, but
does not their force of gravity fall to zero at the center, even if not in a linear decline as in an 'ideal' sphere?
 
nebel said:
Is it correct to say that the 'pulls' of gravity are zero at the 'center of mass' of an entity? and max at the surface/ perimeter?--- if this is so,
One would expect the highest orbital velocities at the perimeter of galaxies, spirals, globular or ellipticals with even mass distribution; and
the lowest speeds near the centers,- of at least of those accumulations without a great central mass.
Results may vary, because of mass density variations, or central black holes, but even there, in the very center, should gravity not fall to zero ? and with it the need for balancing gravity by centrifugal forces?
Click to expand...
If a black hole, exist at the center of a galaxy, and is in fact the center of the galaxy, it is irrational for an object, (black hole) that is created by gravity itself, to not have gravity. However, to test this, one presumably would need to enter and record the gravity at the center of the hole, and as far as I recall, theory does not permit this as the recording devise would be obliterated by gravity.
 
The.Ring., thank you for pointing this out. Inside a black hole, conventional physics is thought to break down, and the OP deals with the gravity, orbital velocities outside such center regions, and with galaxies that do not even have a center bulge , nor even rotation, but must have distinct gravity -balancing orbits for all it's stars. (just like the jumping dolphin gets that 'zero gravity' feeling)
One way or another the direction of the 'pull' of gravity reverses at the center of a black hole region, it follows that it has to go through the zero value, right? so, even
where gravity is extreme, because of great density in the singularity, there has to be a zero gravity situation in there. (see the Ring/torus situation below).
In the normal scheme of things, the earth, gravity in Montreal pulls you toward Australia, the Aussies tend to sink 'up' toward us in the North; somewhere in the interior that force is reversed, so there has to be a zero value, and what better place for that, than in the inner core's center?
is this not so, even if we can not take a gravity gradient meter down there?
BSW: if you understand gravity in 'The. Ring.' or an empty torus; -there is zero gravity from the inside surface all the way to the opposite inside, including -of course- the center. so
there can be even a 'zero-gravity region', rather just a center point; --
with orbital velocities to match. Max on the outside, but free floating, or even stationary at the center. and:
Inside the Ring or that torus the gravity gradient would fall from max at the outside to zero on the inside surface.
 
Last edited:
nebel said:
The.Ring., thank you for pointing this out. Inside a black hole, conventional physics is thought to break down, and the OP deals with the gravity, orbital velocities outside such center regions, and with galaxies that do not even have a center bulge , nor even rotation, but must have distinct gravity -balancing orbits for all it's stars.
One way or another the direction of the 'pull' of gravity reverses at the center of a black hole region, it follows that it has to go through the zero value, right? so, even
where gravity is extreme, because of extreme density in the singularity, there has to be a zero gravity situation in there. (see the Ring/torus situation below).
In the normal scheme of things, the earth, gravity in Montreal pulls you toward Australia, the Aussies tend to sink 'up' toward us in the North; somewhere in the interior that force is reversed, so there has to be a zero value, and what better place for that, than in the inner core's center?
is this not so, even if we can not take a gravity gradient meter down there?
BSW: if you understand gravity in 'The. Ring.' or an empty torus; -there is zero gravity from the inside surface all the way to the opposite inside, including -of course- the center. so
there can be even a 'zero-gravity region', rather just a center point; --
with orbital velocities to match. Max on the outside, but free floating, or even stationary at the center.
Click to expand...

There is no right, or wrong, you could have all the answers and not know it, in fact no one would know it.

In another similar topic, have you heard that quantum teleportation of data, may be happening seriously faster than the speed of light, and might in reality be instantaneous, which if true, tosses Einstein's equations completely into the dumpster? http://www.livescience.com/49028-farthest-quantum-teleportation.html
 
nebel said:
T.R., yes I might have, but the OP deals with Keplerian orbits, Newtonian gravity.
Click to expand...
Newtonian gravity, is what Newton postulated about gravity, without ever leaving the Earth. His view might be flawless, or it might be flawed, however there is still no explanation for what gravity is, just it's noticeable effects, are described. Again, if spooky entanglement reigns true, the speed of light is no longer the max speed, and we need a new model..............again.

So it seems that the more we learn, the less we know.
 
yes, but I am trying to deal with the effects of simple gravity, the 'flat' velocity graphs in galaxy observations; possibly flawed interpretations of MACRO EFFECTS.
whether gravity is a tensioning of space time, exchange of gravitons, Hicks Boson results,-- is another story.
The observed entanglement phenoma, are in another ballpark, real, but futuristic, beyond the immediate grasp of someone in the mid-eighties.
 
nebel said:
yes, but I am trying to deal with the effects of simple gravity, the 'flat' velocity graphs in galaxy observations; possibly flawed interpretations of MACRO EFFECTS.
whether gravity is a tensioning of space time, exchange of gravitons, Hicks Boson results,-- is another story.
The observed entanglement phenoma, are in another ballpark, real, but futuristic, beyond the immediate grasp of someone in the mid-eighties.
Click to expand...
Simple gravity, in galactic observations. This statement implies that you believe that galaxies, which are of currently unknowable complexity, can be made simple. Again, all equations pretty much go out the door, if spooky entanglement disproves that the velocity of light is not a maximum speed. There is also no right of humanity, to achieve a perfect mathematical model. It may be there, and it may not as there may be other realities, with completely different physics, that might be intermingling with our own. Nothing is known for sure.
 
T.R. :-- Newtonian laws, Kepler, with a little bit of general relativity thrown in, got us to the moon and back, Mars, the voyageurs, the comets, and this is the level of discussion the OP aimed for.
are there future possibilities in the arcane field you are interested in? absolutely.
have you exposed these topics in other/your own threads?
 
nebel said:
One would expect the highest orbital velocities at the perimeter of galaxies, spirals, globular or ellipticals with even mass distribution; and the lowest speeds near the centers,- of at least of those accumulations without a great central mass.
Click to expand...
Consider our solar system. The planet Neptune has a much lower velocity around the Sun than Mercury does. But then, our solar system has a great central mass, doesn't it?

Galaxies also have great central masses, but their rotation curves look different to the ones of planets in our solar system. Galaxies seem to rotate more like rigid bodies (although not exactly like that). That's one reason why we need dark matter, by the way.
 
James, that is exactly my point, in an entity, the highest gravity values are in the perimeter, but zero in the center, matter in the perimeter would have to travel at higher velocities to generate the centrifugal forces to counter that maximum gravity there, and surprise! --matter orbiting at the outer reaches of galaxies does.
How are star clusters comparing? it is difficult to get a doppler picture there, because of the lack of common rotation, but all these stars are in stable orbits and not whizzing through the center ( I am guessing here) , but conform to the pattern of inner orbit velocities that are slower and in outer orbit segments faster. In these globulars, it only appears that there are more "central" stars because in their orbits that traverse the central regions, stars are packed closer together, in gentler gravity.

I predict, that in a situation, where the mass of the sun would be diffused equally into the space of the solar system, that in the short run, the orbital velocity of Neptune would be highest, and Mercury the slowest*,
without adding 'dark matter'. so:
who needs dark matter here?
* Kepler's laws of planetary motion are predicated on a great central body, ignoring the masses of the planets, their field.
edited: it is understood that you removed and dispersed the solar mass, that mercury would be off to the races, and so the other planets. I meant that if the present setup existed with the sun distributed, these inner bodies would have to orbit slower to have a measure of stability.
 
Last edited:
Sorry, I got caught editing past the time limit.
In a stable solar system where the planets orbit at their present distances, but the solar mass is diffused equally into the space inside the Neptune orbit, the velocity values would be reversed.
Neptune* , having the total system's mass 'below' it, would have to travel fastest, whereas Mercury*, with hardly any matter below him, could proceed slowly, in that near-zero gravity central environment.
no dark matter needed.
dark matter would be a 'red herring' in that 'ideal mass distribution' situation.
Galaxies, with their diffuse, but enhanced central masses, fall in between the above and the conventional 'central mass' planetary systems., and
rotate more like solid bodies, but perhaps
not because of dark matter in their halos either.
* assuming that we would ignore the gravitational effects of the planet's masses or have them dispersed too,- into toruses in those orbits, and while it could last.
 
Last edited:
nebel said:
One would expect the highest orbital velocities at the perimeter of galaxies, spirals, globular or ellipticals with even mass distribution;
Click to expand...

I missed that you stated this in the OP. That is precisely the first evidence that was used in the dark matter hypothesis.

It is obvious that stars in galaxies are NOT evenly distributed. There are many more stars towards the center of the galaxy than on the outer areas. That would mean that the stars in the galaxy should orbit the center like a solar system. But the stars orbit more closely to a solid (not exactly just closer to a solid) than a solar system. The only way that ould be possible would be if there is a fairly even distribution of matter through the galaxy. The more evenly distributed the matter the more the movement of the diffuse body moves and behaves gravitationally like a solid. But we do not see this even distribution, hence the obvious conclusion that there is matter that does not emit or reflect light so it is dark!
 
Last edited:
origin, in my above model of a solar system with a diffuse solar mass, the orbital velocity of neptune would not be changed, it still has to deal with all that matter calculated to act through the center. It is the speed of mercury, venus that would have to be reduced drastically. Thanks to your objection, can I make it clearer that the even, near 'solid body' galaxy velocity distribution is not about the faster perimeter alone, but the (by comparison to the Solar system) slower inner orbits.
In any circular object, it is only the enclosed mass that generates an inward gravitational force, and with the more diffuse matter distribution of the inner regions of galaxies, (excluding of the central black holes) one would rightly expect relatively low speeds in the orbiting matter there.
One could imagine a model of our solar system with a gradual, galaxy-like dispersion* of the the solar mass, that would result in ~equal velocities for all orbit locations, similar to the flat velocity distribution seen in galaxies, and that without adding dark energy inside the Neptune orbit. . More TNO's Oort cloud objects would not add gravity, or speed to Neptune.
But I agree, the case would vary from one Galaxy to another, and these doppler-type surveys have to be done on near edge-on examples, that are hard to asses about their matter distribution.
On the way down to the 'zero pull' in the center, gravity diminishes in step with the still enclosed, ever smaller mass, and with it the orbital velocity to balance it.
*compared with many galaxy images, the 'central' mass would be smeared out past the orbit of Saturn.
 
Last edited:
James R , - Newton's universal law of gravitation is always applied to show gravity acting from center of [total]mass 1, - to center of [total]mass 2. This is appropriate and true for situations outside these masses.
In the case of galaxies, a substantial portion of their mass lies diffused outside their very center. *
For any body orbiting INSIDE a galaxy, only the portion of the mass that lies between mass 2 (the orbiting object) and the center of mass 1 (the galaxy) can contribute to the gravitational force on 2. so:
While the outer orbit's denizen are pulled inward by the TOTAL mass of the galaxy, with the comparative resulting high velocities,
by contrast, the inner orbiting objects are pulled toward the center only by that part of the galaxy that lies inward from them to the center. A big difference!, because
If one assumes that the same mass pulls on both the inner and outer orbits, as happens in the Keplerian orbits of the Solar system, of course the inner appear to go too slow and the outer too fast; or rather the outer at the right speed, but too fast in comparison to the thus wrongly calculated inner orbits.
Have you seen this reflected in any of the calculations that are used to derive the need for 'dark matter' in the outer halo?
* much of the mass is only shining in the pressure- standing-wave that we see as spiral arms, for there is where stars are formed, the same amount of material exists also between the arms as it rotates toward them, only this material does not show up as light, as it does in the density of stars.
I would like to hear good refutations, specific falsification of these ' pseudo' ideas, could this be moved to the main cosmology page, if it merits it? thank you.
 
Last edited:
You must log in or register to reply here.
Back
Top