egg changed the topic of #principia to: Logs: https://esper.irclog.whitequark.org/principia | <scott_manley> anyone that doubts the wisdom of retrograde bop needs to get the hell out | https://xkcd.com/323/ | <egg> calculating the influence of lamont on Pluto is a bit silly…
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<queqiao-> ⟨pisslover72⟩ does your guys' implementation of spherical harmonic expansion of gravity cause drifting in energy e.g. angular momentum over time? as far as I understand, _just_ (excluding other perturbations) SH gravity at infinite max degree shouldn't cause any drifting in this respect, but I am not sure about this since I'm having difficulty finding relevant papers.
<queqiao-> i apologize in case the SH questions are a bother
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<queqiao-> ⟨sichelgaita⟩ There are plenty of things in Principia that violate the conservation laws, for instance (1) damping of spherical harmonics at large distance and (2) the fact that celestials don't precess. Your questions seem to miss a key point: Principia is a game, _not_ an astronomical simulator. While we try to rely on sound theoretical principles, there are plenty of places where we make trade-offs that deviate from correct physical...
<queqiao-> ... models for the sake of performance or playability.
<queqiao-> ⟨pisslover72⟩ im asking about whether this happens im not making like a judgement statement
<queqiao-> ⟨pisslover72⟩ i very much understand that this is for a game
<queqiao-> ⟨pisslover72⟩ it seems im coming across in a bad way
<queqiao-> ⟨pisslover72⟩ im asking about whether this happens; im not making like a judgement statement
<queqiao-> ⟨pisslover72⟩ to clarify, what im asking is:
<queqiao-> does your guys' implementation have the aforementioned effect
<queqiao-> ⟨pisslover72⟩ to clarify, what im asking is:
<queqiao-> does your guys' implementation have the aforementioned effect?
<queqiao-> my implementations do (depending on max degree). since I'm not finding any literature on this very specific thing, i have nothing to compare my implementation to except for the implementation here. that's why im asking this
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<queqiao-> ⟨sichelgaita⟩ I am honestly not sure what your question is. You talk about our implementation, and in our implementation the damping is nonconservative. If you are asking a theoretical question, then observe that, for a rotating celestial, the potential is time-dependent, so energy conservation doesn't apply; and furthermore, spherical harmonics don't converge to anything useful within the Brillouin sphere.
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<queqiao-> ⟨GoForPDI (less drag=more faster)⟩ as far as I can tell the question is: does angular momentum drift because of the Principia model?
<queqiao-> ⟨sichelgaita⟩ In Principia the geopotential is applied to a point mass, and the rotational motion is computed completely independently. So the answer is no.
<raptop> But is that cat's energy and angular momentum conserved?
<queqiao-> ⟨butcher6994⟩ Yes
<queqiao-> ⟨butcher6994⟩ He has energy conservation down pat
<raptop> Whatever (please pat him for us)
<raptop> s/Whatever//
<queqiao-> ⟨butcher6994⟩ He is sat by my leg. He's a good boy
<queqiao-> ⟨butcher6994⟩ Other good boy
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<queqiao-> ⟨kaborl⟩ New Principia player here! Hi everyone!! 🐤