3 ms·

> All "orbits" are in reality, spirals. Away, or toward things they're orbiting. What are you basing this on? In Newtonian gravity, which is the model used by

• detrites 4y ago
  > in reality
  • biorach 4y ago
    ... well this is embarrassing
  • rhn_mk1 4y ago
    As long as we don't have a Perfect, True, Unified theory of gravity, I don't think you get to say that "in reality" is self-explanatory. It can reasonably mean Newtonian dynamics or relativity, or I don't know what else. Would you clarify?
    • detrites 4y ago
      Sure. Let's meet again on this site in about 7 or 8 billion years, maybe 9. I'm sure it'll become crystal clear.
      • rhn_mk1 4y ago
        Then you're confusing what the dscussion is about. All "lines" "in reality" have thickness and none are infinite. "Orbits" "in reality" are not conical sections. But they are not very useful to talk about because there is no model which describes them accurately to an arbitrary level of nitpicking. But orbits as discussed here are the the are conical sections, and that's why they are discussed: they can be modelled and predicted. The nitpicking that makes them impossible to model is deliberatly left out.
        • detrites 4y ago
          I started this comment thread, so I'm quite confident I know what it's about. It's specifically about the fact that the article makes no mention of a simple, important aspect of the underlying reality it's modelling. It'd take only a sentence or two to clarify and provide a stronger foundation for those learning. As evidenced by responses here, it's obvious this is needed. We all should be keenly aware that models only approximate reality, they always get it wrong and the matter is the magnitude of this error. That's important. A student starting out with the idea that the path of one body in a coupled rotation around another is a perfect ellipse or halves of a cone is a wildly idealised version of an underlying reality that's practically different. Emphasising the reality, that there is a natural, built-in, constant pull or push toward entropy and dissolution of the shape of an "orbit" should be essential. It's that part the student will most likely spend their career fighting against.
          • pdonis 4y ago
            > the reality, that there is a natural, built-in, constant pull or push toward entropy and dissolution of the shape of an "orbit" should be essential Again, what are you basing this on? What theory or evidence tells you that "the reality" is what you say it is?
            • rhn_mk1 4y ago
              I think the "constant" is throwing off the message here. I think the parent is trying to summarize all the unreliable, occasional, and probablilistic factors that models ignore (because they are hard to model), but which still influence practical outcomes of every situation.
              • pdonis 4y ago
                No, that won't do. Model builders are well aware that there are factors that aren't included in the models. But in many domains, and orbital mechanics is one of them, the accuracy of our experimental knowledge is high enough that we can be sure that whatever factors are not in our models are negligible. So just waving one's hands and muttering "entropy" or "dissolution" or "something something unreliable, occasional, and probabilistic factors" doesn't cut it in this domain. detrites needs to back up the very strong claim he made, that I originally responded to, with something much more specific than that.