Developing equation for fictional force created by rotation

Discussion in 'Physics & Math' started by Ultron, Aug 29, 2021.

  1. DaveC426913 Valued Senior Member

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    Ultron : The world is full of bullies, telling you what they think you can and can't do. It's just a fact of life to be navigated, like fungus and flat tires.

    All math lives in an abstract space. Some math can be applied to the real world.
     
    Ultron likes this.
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  3. Ultron Registered Senior Member

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    I like Daves constructive approach and discussion with him is certainly enriching. Discussions dont need to be about beating others (in an argument).
     
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  5. Q-reeus Banned Valued Senior Member

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    Whatever rows your boat as they say. Can't see any useful 'enrichment' though. That would imply having gained new and useful insights not drawn from anyone else. Have you? Could you name one instance?
     
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  7. Ultron Registered Senior Member

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    Sure, for example I did not know GeoGebra, it seems like very useful tool. Nice of him to recommend it. There was more, but it seems you are more interested in arguing than about the topic, so I dont intend to write long replies to you.
     
  8. Q-reeus Banned Valued Senior Member

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    Most people including you naturally react much better to praise than to criticism. Some take advantage of that human nature trait. But tell me where I got it wrong or was unfair in #95.
    And btw toying around with graphical apps like GeoGebra offers will advance your needed understanding by exactly zero. Basic physics knowledge, not fancy interactive graphical outputs, is what you have needed. here.
     
  9. DaveC426913 Valued Senior Member

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    This was bandied about quite a bit, but it's a red herring. You need not worry about it, Ultron .

    Nature is full of fictional or fictitious forces. Some of the best known are the Coriolis Force and centrigual force.

    They are really just another force in disguise (inertia) which becomes apparent in an inertial frame of reference (such as hovering in space).

    Fictitious as they may be, they are very useful when in a rotating frame of reference, such as on the rotating Earth, or on a merry-go-round.

    Look up 'fictitious force' in Wiki for a primer.
     
  10. Q-reeus Banned Valued Senior Member

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    Funny that. I was thinking of commenting on the clear distinction between fictive/fictional and standard physics use of fictitious. The latter relates to inertial forces, the former two (which are legitimately interchangeable) have no use in the physics lexicon (except maybe in a derisory context) and implies imagined i.e. purely surmised and not connected to reality. They should never be confused by assuming equivalence. They are not equivalent i.e. freely interchangeable terms within the physics arena.
    Even within the wider general usage context there are distinctions best to be observed and adhered to:
    https://ell.stackexchange.com/quest...ctional-vs-fictitious-difference-between-them
    Blame myself in a way for not focusing on the use of fictive in the very first post. And later use of fictional. That was a clear signal to avoid, but when I saw how poorly the thread was being handled, yielded to temptation and engaged in dealing with a quest doomed to oblivion from the start.
     
    Last edited: Sep 4, 2021
  11. Ultron Registered Senior Member

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    Yes, there is difference between fictitious and fictive/fictional force, I have searched it before starting this thread. On the other hand there are fictional forces in physics, for example with some liberty in interpretation we can say that the biggest force discussed in mainstream physics right now is fictional force. You have surely heard about the dark energy which contributes approximately 68% of total energy in known Universe. And this dark energy is behind the fictional force which is driving the increasing speed of expansion of Universe. It is not a known force, physicist just speculate about its cause and how it works, but you can say that the measurements indicate, that this fictional force does exist.
     
  12. Q-reeus Banned Valued Senior Member

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    'Dark energy' according to the most popular view is not a force as such but a homogeneous field - the cause of large scale accelerated cosmological expansion owing to a positive pressure existing throughout all space, that more than counteracts the attractive gravitational contribution of a posited positive energy density also associated with said field.

    It's not without dispute and some theorists believe DE is an artifact of not understanding the true nature of gravity, or of us existing in a 'non-representative' region having significantly lower than average matter density. Even 'dark matter' has similarly disputed explanations and conflicting 'observational support'.

    However none of that relates to the topic of this thread. I'm all for contemplating new physical interactions, or new understanding of implications of existing physics.
    Such alternative thinking must though always openly run the gauntlet of constructive criticism. And the bedrock non-negotiable aspect of that is self-consistency. No theory can survive if it fails that requirement of basic logic. As I wrote earlier, subjecting one's pet idea to a range of carefully chosen thought experiments is a great way to weed out non-starters at minimal cost. Cheers.
     
  13. Q-reeus Banned Valued Senior Member

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    Erratum: First para last post contained '...owing to a positive pressure...'. That should have been '...owing to a negative pressure...'. Which is counterintuitive given the example of a balloon expanding under positive internal gas pressure. In GR and similar theories, pressure is a source of gravitation additional to matter-energy. For standard picture DE it turns out pressure's negative contribution to gravity 'outvotes' it's positive energy density contribution by 3:1, and so a net 'negative gravity' tends to expand space. A nice article on it:
    https://www.preposterousuniverse.co...oes-dark-energy-make-the-universe-accelerate/

    PS - I don't agree with Sean Carroll's 'right way' part where he tries to 'simplify' things by seemingly eliminating negative pressure from the mix. Instead of clarifying, it imo confuses further. The first Friedmann equation where pressure is absent, is so because by fiat only energy density is considered. Probably because back when it was derived, there was no reason to believe the vacuum of space could have a non-zero pressure. The second equation includes the effect of pressure as a matter of formal thoroughness presumably.
     
    Last edited: Sep 5, 2021
  14. James R Just this guy, you know? Staff Member

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    Ultron:

    How much do you know about the existing theories of rotation and gravitation? What problem are you trying to solve with the existing theories?

    Just to be clear: you will pay the 10 000 USD after you win the Nobel prize, or after somebody gives you the equation?

    What does that force act on? Mass? Electric charge? Something else? i.e. what properties does an object need to have in order for your additional attractive force to act on it?

    And what is the object in rotation attracted towards?

    Is this force an interaction between different objects, or does the force have some kind of source that isn't an object?
    What's the important feature of an object that makes it "small" in this theory? Small mass? Small rate of rotation? Something else that is small about it? Be specific.

    Are you saying you have experimental evidence for this mysterious new additional attractive force?

    Please summarise the observational confirmation that you have, so far.

    I'm puzzled as to how you confirmed it without having a working hypothesis that would quantify the magnitude of the force. Please explain how you have done that.
     
    Last edited: Sep 11, 2021
  15. James R Just this guy, you know? Staff Member

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    There must be some basic physical principles that underpin any equation for the proposed new force. Until those are clearly expressed, there seems little point in just inventing math out of whole cloth. The point of a physical theory is to model something, with a view to making quantitative, testable, predictions.
     
  16. James R Just this guy, you know? Staff Member

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    Solid objects aren't usually held together solely by gravitational forces, but I think I understand what you mean.

    The "centrifugal" force pulling an asteroid apart is a force that only exists if the observer is rotating along with the asteroid. In an inertial reference frame, what holds the asteroid together are the attractive force of gravity and any other cohesive forces (electric, etc. - the ones that usually hold matter together). Those forces provide the necessary centripetal force required to keep the asteroid from flying apart as it rotates.

    It sounds like you're suggesting that, in addition to the usual forces already mentioned, there's another attractive force that provided additional centripetal force.

    But that seems to contradict something you said elsewhere, about your new force acting tangentially to the axis of rotation, rather than radially.

    So, which is it?

    That sounds like the force is centripetal, then.

    When you say "some point under the surface", which point, specifically? The centre of mass? Is this a force that acts on mass, like gravity, or something else?

    Why do you think that explanation is wrong and that a whole new force is needed?

    Great! Please post the equation.
     
    Last edited: Sep 11, 2021
  17. James R Just this guy, you know? Staff Member

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    Moderator note: some off-topic posts have been moved to a separate thread. Beaconator's unhelpful posts and responses to those have all been moved, as they are an unnecessary and pointless distraction from useful discussion.
     
  18. DaveC426913 Valued Senior Member

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    Consider the cosmological constant as an analogy. The equation to describe it exists and we still don't know what physical principles underpin it.
     
  19. James R Just this guy, you know? Staff Member

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    That's not exactly true for the cosmological constant.

    If you take a course in general relativity, you'll do a shedload of maths, guided by physical theory, before you get to the point of deriving the equation that has the cosmological constant in it.

    Einstein's introduction of the cosmological constant was not just a guess or a piece of recreational mathematics. It was motivated at the time by his belief that the universe was static (i.e. not expanding or contracting). Since the gravitational force between bits of mass is always attractive (no experimental exceptions have been found, so far), something else was needed to provide the necessary countering repulsive force. So, the theory was motivated by experience and observation.

    A relatively short while later, of course, it was discovered that the universe is expanding. When Einstein found out about that he wanted to remove the cosmological constant from his theory, calling it his "biggest blunder".

    What goes around comes around, so now we know that the universe is not only expanding but also the expansion appears to be accelerating. Now the need for the cosmological constant is once again motivated by evidence, observation.

    So, you can see that the cosmological constant is there to make a mathematical model consistent with observed facts about nature, and to allow that model to make quantitative, testable predictions.

    Physically, the cosmological constant is a sort of "anti-gravity" repulsive force. You are right that we don't yet have an explanation for the cause of that force, but we* are reasonably confident it has to be there - that's backed up by observation and experiment.

    One other thing: the mathematical role that the cosmological constant plays in general relativity is not arbitrary. Its appearance in Einstein's equations is not due to Einstein randomly picking a particular mathematical function. There's a whole line of physical reasoning which leads to its appearance.

    ---
    * By "we", I mean this is the current mainstream view among cosmologists. Having said that, I'm sure that any cosmologist worth her salt has considered the alternative possibility that there's something about gravity (or the observations) that we don't understand well enough yet, which might be able to explain the apparent acceleration without the need for a cosmological constant.
     
  20. DaveC426913 Valued Senior Member

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    Yes, I see this as analogous to what the OP is apparently trying to do.


    Likewise the Galaxy Rotation Curve has a well-defined shape but as-yet, no conclusive explanation.

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    Essentially, the OP is groping for a formula to match the "data" he has, whether or not there is an explanation for it yet.



    (The OP has suggested his hypothesis is based at least in part on observation, but has not expounded further. I haven't touched that because it would open a can of worms and pivot this thread to something very different- and analysis of the OP's idea itself - which he does not have yet.)
     
  21. James R Just this guy, you know? Staff Member

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    I don't know if I understand what he's trying to do. Hence the questions I have asked him. I'll wait for his replies.

    Galaxy rotation curves, BTW, have nothing to do with the cosmological constant. We can account for those with dark matter, which is different from dark energy.

    Of course, we don't know what dark matter is, either - if it exists. ;-) Lots of money is currently being thrown at trying to detect it and learn more about it.

    From my point of view, it's more important to investigate that can of worms than the mathematical details of his theory, right now.

    If he is motivated to introduce a new force of nature, I want to know why he believes there is a need for it, first up. If it turns out that his observations are reproducible and reliable, then we should start focussing in on the force and hypothetical mechanisms for it.
     
  22. DaveC426913 Valued Senior Member

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    Of course not.

    Two separate analogies for the OP's efforts
     
  23. DaveC426913 Valued Senior Member

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    That is the responsible thing do but I think it will result in a much shorter (or is it longer) thread. I was kind of enjoying just solving a math puzzle, rather than the inevitability of showing the OP where many of his assumptions and beliefs are wrong.
     

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