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Nuclear and gravitational force related?

  1. Aug 31, 2010 #1
    I am wondering if there have been any attempts to theorize gravitational force as a residual type of nuclear force. If protons and neutrons are mainly responsible for the mass of atoms, and the mass of atoms are responsible for the amount of gravity they exert on each other, then it seems like there should be some connection between the two forces, moreso than that they are two distinct forces related to the same particles. I know I read all the time that there's no unification theory between nuclear force and gravity, but have any attempts been made?
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  3. Aug 31, 2010 #2
    Bad idea. Electrons don't experience the strong force, but fall under gravity.
  4. Sep 1, 2010 #3
    Is that assumption based on the assumption that if they would, electron momentum wouldn't be sufficiently sustainable to prevent the electrons from falling into the nucleus?
  5. Sep 1, 2010 #4


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    It isn't an assumption. It is a verified theory within the Standard Model.

    One of the things that a member of this forum can learn is one aspect of a 'scientific method' that scientists do. We can illustrate this using your example.

    Let's say we have an idea. So we then ask "What if this idea is true? What are the consequences, and can we check if there are already evidence to verify that consequences?" Einstein did this when he made the postulates for Special Relativity. While the verification of SR didn't all come at once, he certainly did make several consequences of the postulates of SR.

    That is what you need to do. As has been pointed out, if you claim that the strong force and gravity are related, then you have a very tough time to reconcile the fact that within the Standard Model, electrons are not involved in strong force interaction, and yet, they have mass and thus, interact with gravity. The same can be said about neutrinos as well.

    Furthermore, one can't make such statements without also addressing the asymptotic freedom aspect of the strong force, which doesn't jive with the long-range force of gravity. They just don't look anything alike in this respect.

    So before you ask if they are related, these are major sticking points that needed to be addressed and reconciled. This is because these major points are something that we know quite well and have been experimentally verified. So it is not as if your proposal is in contradiction with, say, something in string theory. Not being consistent with something that is on shaky ground is one thing. Not being consistent with something that we have verified is often tough to overcome.

  6. Sep 1, 2010 #5
    well, lets see. gravity follows an inverse square law because space is 3 dimensional. A simple calculation shows that gravity therefore cant possibly hold protons together (its 1040 times too weak) unless gravity follows some other law at small scales. But why would it? Is space more than 3 dimensional at small scales? If it were then I think that we would know by now.

    On the other hand, I guess its conceivable that the nucleus might have a core containing a tremendous amount of active gravitational mass surrounded by a shell of negative active gravitational mass which mostly cancels it out. I guess that would accomplish the same thing but I dont see any reason to think that it would have any such thing. (On top of that it would require that inertial and gravitational masses be different)

    The simplest explanation here is simply that the strong force is a completely separate force. Why shouldnt it be?

    There seems to be a very pervasive idea that all the forces should eventually be combined into one. I dont really understand this. Things only simplify so far. Eventually you reach a point where it just cant be simplified any further.

    I'm not sure where the metallic bond fits into the picture. I've always wondered about that.
    Last edited: Sep 1, 2010
  7. Sep 1, 2010 #6
    ok, thanks for sharing some reasons why the two forces are currently held to be unreconcilable. My main question, however, was whether there have been any theories that attempted to reconcile the two forces but failed and why/how.

    The forces of the atom seem, imo, like they should fit together in some kind of complex energy-conservation model that explain gravity. Electrons repel each other by electrostatic charge and also release energy as EM radiation. They also collide and invigorate each other that way. So it seems like atomic electrons should be in a continuously dynamic state of energy flux. Gravity could emerge from that flux in some way. I shouldn't post speculation, b/c it's not allowed in this forum, but I would like to know if any reputable physicist has made theoretical attempts to connect gravity to nuclear force.
  8. Sep 1, 2010 #7


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    Again, you need to see what we already know. By your argument of electrons in a 'state of energy flux', you should consider the consequences of electrons jiggling up and down. If you speculate that this should create gravity, then you will have a tough time (again!) at what we know that is going on at numerous synchrotron light sources and FELs throughout the world. In those facilities, electrons pass through structures known as wigglers and undulators where they jiggle up and down. As far as we have seen, no gravity was created there!

    At some point, before you propose something, you need to double check if what you are saying is inconsistent to what we already know. This is not the type of 'speculation' that we do in science.

  9. Sep 1, 2010 #8
    I wasn't saying the the electron flux would create gravity. What I meant was that the electron flux could neutralize a certain amount of nuclear force, and that the remaining nuclear force would behave in a way commonly recognized as gravity. It's really just an example of how the two could be related but, as I said, I am more interested in what attempts have been made that are widely recognized among credentialed physicists.

    I was reading a book about theory-unification and it said that Einstein was devoted to this but that he clashed with quantum theorists and others who disliked his intuitive approach. String theory seems to be a theory of everything that relies on mathematical complexity, but I was wondering if anyone has attempted to continue with Einstein's method of visually/intuitively accessible approach to unifying gravitational and nuclear force. Apparently not or someone would have said so by now.

    I'm not interested is debating your opinion of what is done "in science" or not. I don't know enough of "what we already know" to double-check in the sense it sounds like you expect. I am certainly interested in learning the reasons why electron momentum, particle momentum/collisions, and EM radiation aren't considered to interact in a way that maintains system-wide levels of energy, which would be sustained by gravitational force, but as you say this is just lay hypothesizing that motivates me to search for relevant established knowledge.
  10. Sep 1, 2010 #9


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    This really is a "word salad". What is this "electron flux" and what is meant by "neutralize"? And one can neutralize "a certain amount" of nuclear force? What amount? By what mechanism?

    This really is now beginning to sound like crackpottery.

    In case there is any doubt left, to answer your question as posted in the topic, no, we know of nothing right now to indicate that nuclear and gravitational forces are related, and certainly, not in the way you imagined.

    That, I believe, should end this, no?

  11. Sep 1, 2010 #10


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    Hi brainstorm, what you are describing is what is called a "theory of everything". So far we don't have one. We can unify the strong, weak, electric, and magnetic forces, but not gravity. As ZapperZ says, it is nothing so easy as what you are suggesting, but there is lots of work ongoing on this topic.
  12. Sep 1, 2010 #11
    For example, if a certain amount of nuclear force would extend beyond the electrons and cause weaker attraction between particles, then the portion of the field between the nucleus and the electrons would be neutralized in their effects between particles. This was really just an example of a possible logic. I'm not trying to engage in crackpottery - just pointing out that if I as a lay person can think along such lines, surely there would be some well-trained physicists exploring such ideas.

    Well, the question is why did Einstein want to pursue such ideas and why hasn't anyone followed in his footsteps?

    I would like to know which work you are referring to.
  13. Sep 1, 2010 #12


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    String theory is the most well-publicized approach to this kind of unification.
  14. Sep 1, 2010 #13


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    Or maybe the well-trained physicists know the properties of the strong interaction (i.e. the asymptotic freedom behavior), and what you described here does not fit into what the strong interaction is. Besides, how would the strong interaction caused a weaker attraction between the nucleus and the electron, when the electron is not affected by the strong interaction?

    You really cannot make things up like this when you have no idea what they are in the first place.

    Einstein failed in trying to unify gravity with the rest because it can't be done that way. We know more now and the quantum gravity problem is immense. We don't even know if the various quantum gravity models that we currently have are even valid, since they are still far out of the realm of testability. But that in itself has clearly shown that there are efforts in trying to find some "ToE" and "GUT". However, none of these have any resemblance to how you are picturing it here.

  15. Sep 1, 2010 #14
    I read the Einstein became isolated in his later years because he continued to pursue intuitive theories and unification, but I don't know why no one would embrace his methods and continue his type of work. I do understand why QM is so popular, due to its accuracy. And string theory seems to achieve the unification ideal for the most part. I just wonder what, if anything, Einstein or someone else who thinks in that way could come up with if it was popular to do so. It seems to me that QM is more accessible because hard work and diligence allows people to master the math required, but of course I am just guessing at this from my lay perspective, not having the real experience of doing the classes and homework that get a person to the point of being well versed in QM.
  16. Sep 1, 2010 #15


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    This is no longer physics. You are asking us to speculate human practice.

  17. Sep 1, 2010 #16
    I've often contemplated this exact question, because on the surface, the strong force and gravity have the tantalizing similarity of both being attractive forces between massive bodies, regardless of electrostatic charge or magnetism. Among all the remaining forces, the strong force and gravity seem to share this great similarity, so it's tempting to speculate about their possible unification. If we had, say, some elegant mechanism that explained how the inverse seventh power law of the strong force could yield an inverse square law at much longer ranges, then we'd have something interesting.

    So this is precisely what one branch of string theorists tried to work out, and they hypothesized a class of equations to describe how one or more extra dimensions could manifest at very small scales, thereby explaining how gravity could take a new and very powerful form at nuclear scales and the well-known weaker form at larger scales. This idea has been tested. And, to the dismay of these theorists (but as a triumph for the experimental physicists running the tests), the inverse square law of gravity has demonstrated perfect consistency down to the range of experimental accuracy, about 56 micrometers: http://www.scientificamerican.com/article.cfm?id=string-theorys-extra-dime

    Now, if you -really- want to twist your melon, have a look at the concept of gravitomagnetism, and the totally crazy parallels between gravitomagnetism equations and electromagnetic equations, in the weak field limit. There we see totally unexpected phenomenological parallels between gravity and electromagnetism that just reek of an underlying natural order...and yet on close inspection the differences just seem too irreconcilable to overcome. And yet with every historical breakthrough we discover ever deeper elegance and symmetry underlying the foundations of physical law...
  18. Sep 1, 2010 #17
    Are you sure you arent thinking of the Van der Waals force?
  19. Sep 1, 2010 #18
    I have also always found it fascinating to talk about the what ifs of physics. Personally I would perfer to find a connection gravity and electromagnetism. The consequences of an interaction between them, such as suggested in Heim theory, would revolutionize this world and perhaps help in finding a theory of everything.
    Wikipedia has a section on theories of gravity. There are many theories there and I always enjoy picking one at random and running with it. I usually get nowhere but I go fast enough that when I hit a wall I have enough momentum to carrry me elsewhere. There are also many theories that attempt to combine gravity with other forces but not all. Each theory has its own unique properties and consequences. My favorite thing to think about is how I could exploit this to power the Enterprise. Hope you enjoy.
  20. Sep 1, 2010 #19
    I should’ve qualified that – the Yukawa potential is not a simple inverse power law, but I've encountered sources that utilize the inverse seventh power as a reasonable first-order approximation of the force between nucleons for back-of-envelope estimates.

    “as an approximation, the magnitude varies inversely as the seventh power of the distance between the particles since this is consistent with its very restricted effective range.”

    “The force that holds nuclei together however, seems to be decay as the seventh or greater power of the inverse distance.”
  21. Sep 1, 2010 #20
    Given the grass-roots triumph of Heim's empirical formula that predicts the mass spectrum of fundamental particles from first principles (five physical constants like c and h, as I recall), I'm not sure Heim wasn't onto a unified field theory. That his work still hasn't been properly peer reviewed by now is, in my opinion, the greatest single failure of theoretical physics in decades.

    As I see it, and I think many would agree with this, the universe is a single and elegantly operational system of physical laws - so there must be a single and elegantly operational equation that describes those laws. It's just going to take the right data and the right flash of genius to express it for the first time, imo.
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