Item — HN Reader

I agree and I vehemently share your concern about profusion of tweakable parameters in the model.

There is some misconception in the wild about epicycles models that need not be shared by you specifically. There weren't that many epicycles per orbiting body, but every orbiting body had a few that had to be 'trained' specifically for them.

My fear, and I suspect yours too is that good curve fits done one at a time with mathematical models that are universal approximators (*) rarely, if at all lead to causally explanatory models. In Physics it's the latter that we seek.

(*) Epicycloidal models are a form of Fourier analysis and are a class of universal approximators for periodic trajectories.

1 comments

Thanks for the epicycles clarification, I did not know each body had its own fitted set. This makes the parallel with overfitting even stronger.

And I think we agree on the real problem: a good fit on one problem, made with a universal approximator, is not an explanation. It can be just a compressed description, maybe with a cause behind, maybe not. I cannot fix this, but I added this week a small thing to at least see it: a bootstrap stability check. You resample the data, refit, and look how often the same form comes back. High frequency does not prove anything causal. But low frequency is a good signal that you are only looking at a Fourier-type fit, not a law. The decision stays with the user, the tool only makes it visible.

Too late, but I hope you see it. In the original post you said:

> That's Kepler's Third Law (T² ∝ a³), which took Kepler ~10 years to find in 1618. GP_ELITE found it in ~3 seconds.

In future post in HN I recommend to avoid that kind of comparisons, because we all know he did that on paper and didn't even have a good set of functions to use a brute force aproach. It feels like unnecessary linkbait and make people write unfriendly comments. Probably it's better:

fake quote> That's Kepler's Third Law (T² ∝ a³), GP_ELITE found it in ~3 seconds.

Thanks for the advice; you're absolutely right ,it was just to grab attention.