Gravity never zero

Discussion in 'Astronomy, Exobiology, & Cosmology' started by Ivan, Dec 18, 2011.

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  1. Ivan Registered Senior Member

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    Hi I make this short,

    Is it true that gravity always exists and It never goes to zero no matter the distance?
    Would not the universe in a "endless" time period, draw it self together again? Make a cycle.. of expansion(big bang) and black holes


    note
    And even if there is no friction in space would not the universe be able to decelerate and contract itself since the little force never stop to exist, but the speed and the centrifugal force can stop. Sorry for my bad English


    Best regards / Ivan Loguin
     
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  3. Robittybob1 Banned Banned

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    At a guess I'd say we should just wait and see what happens. For there is Expansion, and Dark Energy and the shape of the Universe which is unknown.
    Too many variables to consider, but at the moment galaxies are expanding away from each other, but locally they tell me we are heading toward the centre of the Milky Way. There is a large Black Hole in the centre drawing the stars of the galaxy into it.
    Gravity wins on a local scale, but looses on the Universal scale.

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  5. James R Just this guy, you know? Staff Member

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    Yes. The strength of the gravitational attraction between two masses is proportional to the inverse square of the distance between them. Therefore, since no two masses can be an infinite distance apart, the force of gravity is never zero.

    Not according to the latest evidence, which suggests that there is a kind of "anti-gravity" effect pushing the universe apart. This is known as "dark energy".
     
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  7. Ivan Registered Senior Member

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    Thanks

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    The explanation of the gravity of yours was very beautiful.

    Hi, but if there is a big explosion)big bang), and no friction in space would not that be a answer, it expands since nothing stops it, gravity affects it still but the force that's pulling is almost nothing, even less in greater distance, so it will take forever to stop and reverse. I mean, as it is now some planets move only a cm in a year from force gravity. So my theory if it work doesn't make much happen in a while xD. But a force that never depletes, and velocity does. it wins in eternity. But im not going to wait and see hehe ty for replies.
     
    Last edited: Dec 18, 2011
  8. origin Trump is the best argument against a democracy. Valued Senior Member

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    Well if the initial velocity of the expansion was high enough and the amount of mass was low enough gravity would never win and the expansion would contiue for every.

    However there is another issue and that is that the expansion is accelerating. That means there is 'something' that is increasing the rate of expansion. This 'something' has been given the term dark energy.

    This added expansion energy pretty muchly seals the deal that the universe will never contract.
     
  9. Robittybob1 Banned Banned

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    I have not been able to find it yet but I have discussed the fact that gravity becomes zero at a certain distance, because the gravitational field has to be made by particles with mass and there comes the likely situation that a particle has insufficient mass to extend this field throughout the Universe (on the basis it takes Energy to form the field). Forces are addition ie G force is proportional to mass, but with the inverse square the drop off of strength means it become very minimal far out and there is no study yet that shows the ability to extend gravity field is proportional to Mass. Field intensity is definitely proportional to mass.

    Whether the Universe continues to expand will depend on its over all shape (unknown).
     
  10. billvon Valued Senior Member

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    Well, gravity might.

    Depends on the initial speed. If the initial speed exceeds a critical limit (i.e. escape velocity) gravity will never be sufficient to stop further expansion. If it's less than that, it will eventually stop and start heading back together.

    The earth moves about 180 million miles every six months due to gravity! And we are quite far from the sun.
     
  11. AlexG Like nailing Jello to a tree Valued Senior Member

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    Ribbity, you are simply wrong.
     
  12. Robittybob1 Banned Banned

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    I didn't specify a distance this time. So do you honestly believe that the smallest particle with mass and gravity is capable of filling the whole Universe with a gravitational field? I wonder if it is anywhere near possible and it must be getting harder as the universe inflates further.
    Tell me Alex. (Aside: I found a site from UCLA that seemed to have simialar views to yours ???)

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  13. AlexG Like nailing Jello to a tree Valued Senior Member

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    Ribbity,

    Here's the formula for gravitational attraction between two objects:

    F = G(m1*m2/r^2)

    where:

    F is the force between the masses,
    G is the gravitational constant,
    m1 is the first mass,
    m2 is the second mass, and
    r is the distance between the masses

    So show me where F goes to zero, at any distance.

    This is about as simple as it gets. Do you understand it?
     
  14. Robittybob1 Banned Banned

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    When was that formula worked out? What was the maximum distance was it calculated at?
    What other situations has confirmed that equation?
    [I would say satellites orbiting the Earth could be an ideal situation to double check this equation.]
    What is the furtherest objects in the Universe that really show they are under the influence of gravitational attraction?
    Can you conceive what a gravitational field is and how it spreads to the furtherest ends of the universe? How? why? what? If we knew I would be a bit more confident to anser your question.

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  15. AlexG Like nailing Jello to a tree Valued Senior Member

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    It's Newton's formula, and it was first published in Philosophiae Naturalis Principia Mathematica ("the Principia") on 5 July 1687. So the formula is almost 400 years old, and has been tested and applied for that long. It works at every distance.


    What do you mean, the maximum distance calculated at? No matter what distance you use for r, you will never get zero for F.

    The diameter of the observable universe is estimated to be about 93 billion light-years),putting the edge of the observable universe at about 46–47 billion light-years away and Newtons forumula works as far as we can see in space.

    Gravity never stops and never goes to zero, at any distance.

    This is VERY basic, elementary physics, so why am I not surprised you don't know it?
     
  16. Robittybob1 Banned Banned

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    From memory they have corrected the G constant since Newton did his experiments. (Is that right?) (the G constant will have a degree of uncertainty associated with it and I would say the distances I'm thinking of the the attractive force would be less than the margin of error (if that is possible???)
    I'm not saying there are regions where there is no gravity, but how can the whole universe be filled with gravitational field emanating from my body?

    I'm still looking for evidence that 2 galaxies 1 billion lightyears apart can be shown to be under the influence of each other's Gravity when in fact they are more than likely separating rather than getting closer to each other.

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  17. AlexG Like nailing Jello to a tree Valued Senior Member

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    Bibbity, no matter what values you use, the equation will never yield zero. Your math can't be that weak, can it? Whether you can understand it or not, or bring yourself to accept it or not, 400 years of experiment, astronomical observation and space flight show that the equation is correct.

    There's really nothing more to be said.
     
  18. Robittybob1 Banned Banned

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    I'm really bad at maths, but looking at it even though I'd like to understand it, it just seems too hard.
    If I could put the formulas into a excel workbook or something like that and see how thing vary when the parameters change I would get a innate feeling for any formula.
    And that is part of the Newton equation, it just gets too minimal at enormous distance. Ill have to check it out.
    A "force particle" must have minimum quantum of a sort? I tried to look up "force particle" and couldn't find it. Do you remember what they were called? Years ago they used to say when you applied a force there was a transfer of these things?? Can you remember the word for them? Please.

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  19. James R Just this guy, you know? Staff Member

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    Ivan:

    Ignoring dark energy for a moment, whether the universe slows down and stops then starts contracting again or whether it keeps expanding at an ever-slower rate depends on the average mass density of the universe. If it is dense enough, then gravity should be strong enough to pull it all back together, stopping the expansion and leading eventually to a "big crunch". If it is not dense enough, then gravity can't stop the expansion caused by the original big bang.

    Dark energy throws a spanner in the works because it introduces and extra repulsive force into the picture.


    Robittybob1:

    This is wrong.

    Gravity never becomes zero.

    Also, in a quantum picture of gravity the force is carried by massless gravitons, not by particles with mass.
     
  20. Robittybob1 Banned Banned

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    @ JamesR

    Have they found gravitons yet?
     
  21. AlexWonderer Banned Banned

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    Technically, YES. But very little. Atoms all have their own mass - there's always going to be masses of gas that isn't exactly massless, distant planets, etc. however, we would perceive it as 'zero gravity' - even though there is, but it's so neligible we wouldn't be able to detect it ourselves if we were out into distant space. Good question though!
     
  22. OnlyMe Valued Senior Member

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    No.
     
  23. Robittybob1 Banned Banned

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    Well I was thinking even if they do find a graviton what will it do?

    "Particle without mass", does that mean it will travel in one direction only at any one time? (like a neutrino or photon.)
    Does it have an Energy level? So will it be like a photon in having momentum etc?
    If it doesn't travel as a unit will it spread itself out over the entire universe obeying the inverse square law?
     
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