3 ms·

> in reality

biorach 3y ago
... well this is embarrassing
rhn_mk1 3y 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 3y 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 3y 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 3y 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 3y 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 3y 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 3y 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.
        detrites 3y ago
        The parent is correct, and maybe we're somewhat at cross-purposes here. I'm not criticising the model, I'm criticising the way it's presented. I find it's common in older texts to present a model as if it is reality. And why, ever, do this? It's only bad. As you state, model creators are well aware of the limitations. But, this text is targeted at learners. They're just beginning such a journey and may not at all be so keenly aware of such. I can't supply what you seek of something within the model that violates the model. Which is fine, as it's beside the point and target of my criticism, which isn't of the model but of one aspect of the style used to present it.

> in reality

... well this is embarrassing

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 3y 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 3y 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 3y 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 3y 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 3y 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 3y 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.
        detrites 3y ago
        The parent is correct, and maybe we're somewhat at cross-purposes here. I'm not criticising the model, I'm criticising the way it's presented. I find it's common in older texts to present a model as if it is reality. And why, ever, do this? It's only bad. As you state, model creators are well aware of the limitations. But, this text is targeted at learners. They're just beginning such a journey and may not at all be so keenly aware of such. I can't supply what you seek of something within the model that violates the model. Which is fine, as it's beside the point and target of my criticism, which isn't of the model but of one aspect of the style used to present it.