Where is most "gravity", inside or out?

Discussion in 'Astronomy, Exobiology, & Cosmology' started by nebel, Feb 29, 2016.

  1. nebel Valued Senior Member

    Messages:
    1,285
    I did not mean to say that. If there is no, zero , gravitational effect in the center, (small or great), of a sphere, because the opposing tensions have cancelled out (like an interfering wave energy would, locally), but if each of the opposing, now overlapping or interspersing gravitational fields produce their undiminished whatever relativistic effects, would or
    is there not a disconnect between the existing, resulting gravitational "field "strength, and the GR SR phenomena? or
    If a body does not experience the effect of gravity, acceleration, as it would at the center of a sphere, why do you think relativistic effects should kick in when gravity does not?
    Does gravity have a dual nature, existing even when it is balancingly cancelled? thank you. (it is not off topic bsw)
    PS: in other words, are there two (or more) gravitational fields at work inside sphere? how about if you opened them up, started to separate them like 2 cups?
     
    Last edited: Mar 31, 2018
  2. Google AdSense Guest Advertisement



    to hide all adverts.
  3. DaveC426913 Valued Senior Member

    Messages:
    9,051
    To be clear, the tensions are not literally cancelling out by destructively interfering with each other - as in your wave energy analogy.
    They simply result in a net force of zero. The gravity is still there, pulling every atom in all directions at once.

    The reason we know it is still there, is because we can test for time dilation and for gravitational redshift, showing that both are at their strongest at the centre, showing that gravitational potential is highest there, just like in the rubber sheet diagram.

    Photons fired from the centre of the Earth will have to climb their way up the gravity hill, red-shifting the whole time they are climbing. The deepest part of the hill is at the centre.

    If the centre were way up at y=0, that would mean photons would not have to climb a hill at all. They would actually blue-shift as they left the centre. They don't.
     
  4. Google AdSense Guest Advertisement



    to hide all adverts.
  5. nebel Valued Senior Member

    Messages:
    1,285
    What tests confirm relativistic effects at zero gravity?
    The rubber sheet analogy shows the result of surface gravities, not, to my knowledge, the situation inside the ball causing the dimpling.
    The inside of the ball harbours zero gravity, a condition that the rubber sheet achieves only at infinite size.

    In Origins post #3 graph, is seen that a photon or any intrepid climber would have to battle gravity out of the zero center but in very low strength in the first steps, at the center, the beginning of the climb. So: (Shell theorem predicts, that only enclosed matter's gravity matters) treat the inside gravity as an onion type situation, surface gravity of one layer at time. First step, small ball, small gravity.no blueshift there.

    I learned that waves blue shifted and not particles, except quarks and their quirky colours.
     
  6. Google AdSense Guest Advertisement



    to hide all adverts.
  7. DaveC426913 Valued Senior Member

    Messages:
    9,051
    To be clear, the rubber sheet analogy and the graph of gravitational potential energy wrt to radius are two very different animals.
    The former is an analogy; only useful for intuiting ideas. The latter is an actual graphical representation of the gravitational potential energy wrt radius of a massive object, not an analogy.
     
    Last edited: Apr 1, 2018
  8. RainbowSingularity Registered Senior Member

    Messages:
    956
    "it is not the speed that kills you, it is the stopping"

    soo, is an opposing gravitational force a deceleration ?

    if the opposing gravitational force absorbs the energy then the human body wont .. ?
     
  9. DaveC426913 Valued Senior Member

    Messages:
    9,051
    No. In terms of the acceleration gravity applies, it cancels out to zero.
     
    RainbowSingularity likes this.
  10. RainbowSingularity Registered Senior Member

    Messages:
    956
    soo theoretically... the ability to create artificial gravity will enable fast travel of the human body(deceleration & acceleration speeds have not been openly discussed in the brick walls to human space travel etc...)
    err-go i guess, if the global species extinction risk is not high enough with nuclear weapons, it is likely to not withstand the attainment of anti-gravity science ... ?
     
  11. DaveC426913 Valued Senior Member

    Messages:
    9,051
    nebel, I have a suggestion. Draw what you think the curve should look like, according to your idea. Label the parts of the curve. Pay particular attention to
    • any inflections (parts of the curve that change direction, like positive curve to negative curve)
    • any cusps (parts of the curve that change direction abruptly, such as at a boundary)
    Upload it here so we can analyze it.

    I tried to do it, and found I was forced to draw a few inflections and cusps that weren't logical.

    I think you will find the rendering effort - and subsequent analysis - enlightening.
     
  12. nebel Valued Senior Member

    Messages:
    1,285
    Yes, I have the commitment of some one to help me, but it is more primitive than you anticipate. My models are Basic.
     
  13. nebel Valued Senior Member

    Messages:
    1,285
    yes , two different species indeed, the rubber sheet deals with the outside gravity of the depressing mass, and the thread at hand deals with more than that, the internal gravity gradient. will try to combine the 2 in the drawing that was promised to be transmitted.
    All this is no big deal for small bodies, but when you deal with galaxies, clusters, to understand the interior forces is crucial. because
    The massive "halo" extending to infinity has no purchase on enough matter to count for much.
     
  14. DaveC426913 Valued Senior Member

    Messages:
    9,051
    Matters not how primitive it is. So long as it is sufficiently accurate to label the important parts.
     
  15. nebel Valued Senior Member

    Messages:
    1,285

    Please Register or Log in to view the hidden image!



    here is the weekend's project. Fig 1, mainstream surface gravity, Fig 2 showing inside g gradients, Figure c : Gravity in empty shell, Fig. d gravity in a disk.
    #1 the level of zero gravity, going to infinity, and showing interior points, areas 6 where 0 g occurs. #2 areas traced by the depressing ball , showing depth, strength of spacetime warp, #3, 31-34 identifies the entities depicted, # 4 identifies the interior g gradient in a even density body, #5 hints at the same gravity fall-off in a body with increasing mass toward the center (line in Figure 5 missing) (numbering 5 in Fig d missing), #7 the deep gravity well leading to a black hole, but still having zero g at center point 6, #8, location of black hole at the center of a deep well, stuck in time also, (see ALMA thread). Ghostly images at right, are rough sketches what this would look like in 3D.
    Note the important lazy 8 symbols at rights, showing zero gravity #1 and outside gravity gradients#2 going to infinity.
    questions please.
     
    Last edited: Apr 1, 2018
  16. DaveC426913 Valued Senior Member

    Messages:
    9,051
    Reorganized, for clarity (since there are three distinct scenarios).

    S1. mainstream surface gravity:

    Please Register or Log in to view the hidden image!


    1 the level of zero gravity at infinity
    2 areas traced by the depressing ball , showing depth, strength of spacetime warp
    3 spherical mass


    S1b. same thing showing inside g gradients:

    Please Register or Log in to view the hidden image!


    1 the level of zero gravity at infinity
    2 areas traced by the depressing ball , showing depth, strength of spacetime warp
    3 spherical mass
    4 interior g gradient in a even density body
    5 gravity fall-off in a body with increasing mass toward the center
    6 areas where 0 g occurs


    S2. gravity in empty shell:

    Please Register or Log in to view the hidden image!


    1 the level of zero gravity at infinity
    2 areas traced by the depressing ball , showing depth, strength of spacetime warp
    3 hollow spherical mass
    4 interior g gradient
    6 areas where 0 g occurs


    S3. gravity in a disk:

    Please Register or Log in to view the hidden image!


    1 the level of zero gravity at infinity
    2 areas traced by the depressing disc
    3 flat disc mass
    4 interior g gradient in a even density body
    6 areas where 0 g occurs
    7 the deep gravity well leading to a black hole, but still having zero g at center point 6
    8 location of black hole at the center of a deep well, stuck in time also
     
    Last edited: Apr 1, 2018
  17. nebel Valued Senior Member

    Messages:
    1,285
    thank you! wow, really appreciate that. you can see on what primitive level i operate.
    PS: There is unintended method to my (disorganized)madness though. By forcing them to find the 6s, viewers should get the message for good. ha ha.
     
    Last edited: Apr 1, 2018
  18. DaveC426913 Valued Senior Member

    Messages:
    9,051
    OK, only scenario 1b is what we have been discussing, but let me ask something about scenario #2:

    It is your contention that time dilation increases slowly as you approach the hollow sphere, but the moment you pass through it, time dilation will instantly return to zero (the vertical slopes of the curve). That is what diagram 3 indicates.

    It does not merely have a cusp; it has a nearly infinite positive slope (it's not actually infinite, since the shell does not have zero thickness)

    Let's examine this for a moment:
    I am standing on the outside of the hollow sphere in my spacesuit.
    I look at the watch on my right wrist and sync it with a watch on a nearby moon.
    I see that my watch is running slowly compared to the moon's timepiece (because I am in the sphere's well).
    Actually, to be accurate, everything here is moving normally, but the moon's clock is running fast, as I see it.

    Now, there happens to be a small hatch in the hollow sphere next to me.
    I kneel down, open it and stick my left arm (which has a second watch) through it.
    The fact that it is inside the hollow sphere means that, according to you, it is experiencing zero time dilation. It is back in sync with the clock on the moon, each ticking off one second at the same rate.

    So, the watch on my right hand is ticking normally, and the watch on my left hand is ticking in sync with the moon's clock i.e. faster than I'd expect. Even though my two watches are four feet apart.


    My left hand is actually aging faster than my right hand since I have to extended it through this hatch.

    My cells are metabolizing faster and even my blood is flowing faster in my left hand than the rest of my body.

    That is the inescapable outcome of your assertion of time dilation in a gravity well.
     
    Last edited: Apr 1, 2018
  19. nebel Valued Senior Member

    Messages:
    1,285
    I am not a quick thinker, and relativity is not my strong suit, but yes, at first blush your elaboration on the images might be true. Imagine! stranger things have been proposed in the name of Albert's masterpiece. thank. you!
     
  20. DaveC426913 Valued Senior Member

    Messages:
    9,051
    It leads to a paradox. Follow the rest of the scenario.
     
  21. nebel Valued Senior Member

    Messages:
    1,285
    later, I am out of time, out the door. But do we not have the twin paradox in SR GR too? so, if The images can create paradoxes like Albert E, the great did, there might be a glimmer of hope here too. imaginative images.
     
  22. nebel Valued Senior Member

    Messages:
    1,285
    Astute observation. It turned out that way, because in the fringe, alternate Nebel thread "ALMA, look-back-time to galaxies", the spherical model has zero thickness, to account for the fact that our moment in time has zero length. If holl0w spheres are rare, those with zero wall thickness are even rarer.

    There is a lot material to cover in the 'moon, sync operation, accelerations, corrections for velocity, distance to the moon', do we need that?

    Simply, open the hatch and stick your arm in. You do not even need a space suit, it could be a hollowed out planet with atmosphere, and you being at the open bottom end of a shaft. Now:

    You could have your child that is watching your hand inside get a physics lesson, by having a top spin and do nutations, suspended in the inside midair, or drink with a long straw from a floating bubble of milk emptied from a carton, reached in.

    I actually only asserted, non -relativistically-, that there is no effective gravity at the center of a sphere, none at all in an empty sphere. all forces are outside. but
    If it is true that only , the resultant , the cancelled fields in the zero zone are affecting the relativistic outcome, --yes, I would stay out of the interior if I want to live longer. ( there are religions that teach we could live eternally, so, only then would it be noticeable that you have one young and another, older arm) patience! so:
    A subject for another topic/thread would be:
    Do overlapping, opposing, thus cancelling gravitational fields retain their separate relativistic effects or are these equalized, diminished too? Do directional gravity fields cancel but non-directional dilations add?
     
    Last edited: Apr 2, 2018
  23. nebel Valued Senior Member

    Messages:
    1,285
    From original sentences thread:
    perhaps so, gravity begins at zero at the center, to be at max at the surface and falls off forever to zero only at infinity. original sentence?

    Gravity begins with zero at the center, on the way out, never reaches zero again.
     
    Last edited: Apr 16, 2018

Share This Page