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Comment by andrepd | Hacker News Reader

>A theory can explain observations even perfectly well and still be wrong- because the frame of reference is wrong. The worse thing is that you can't figure that out until you've figured out what the correct frame of reference is, and looked at your obsrevations in a new light.

Well strictly speaking, it wasn't wrong. It explained the observations perfectly well. What a heliocentric description brought was a simpler description that illuminated the principles behind it, in a way that enabled us to discover the inverse-square law of gravity, link that to Gauss's theorem for gravitation, explain it even from a more fundamental geometric perspective with general relativity, etc.

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It was wrong in the sense that epicycles are an entirely imaginary math artefact, and reality works on different principles.

Revolutions happen when a new mental model - or frame of reference, or whatever you want to call it - can generate new kinds of math.

The old model is certainly wrong in the sense that it's not a good picture of how reality actually works.

If you really want to, you can still use epicycles for certain kinds of problem, just as you can use Newtonian physics for basic mechanics.

But this is engineering, not physics. These theories are useless for frontier research. They're absolutely wrong in the sense that their lack of completeness means they cannot be used to generate theory[n+1].

> It was wrong in the sense that epicycles are an entirely imaginary math artefact, and reality works on different principles.

How do you distinguish "an entirely imaginary math artifact" from the "principles" that "reality works on"?

(Hint: planetary orbits are not ellipses once you take GR effects into account.)

The same way we distinguish the shadows cast in Plato's cave from the objects occluding the light. The more situations in which a theory or model makes accurate predictions, the more correct it is. Epicycles are much, much more wrong than mathematically perfect elliptical orbits.

> Epicycles are much, much more wrong than mathematically perfect elliptical orbits.

Not if you define "wrong" as "inaccurate predictions". You can approximate ellipses with circles and epicycles to any desired degree of accuracy by putting in more epicycles. So you can match the predictions of ellipses to any desired accuracy with epicycles.

Also, as I noted, the actual orbits of the planets are not perfect ellipses once GR effects are taken into account. Have you proven mathematically that it is impossible to construct an epicycle model that makes more accurate predictions than perfect ellipses, based on the actual data (which confirms the GR predictions to within current observational accuracy)?

After reading this thread, I think I've discovered the real reason new physics isn't being done.

You're being intentionally obtuse. "Just add more epicycles!" isn't building a better model (for a sensible definition of "better"). It's just overfitting. You are the reason why regularization exists. https://en.wikipedia.org/wiki/Regularization_(mathematics)

> planetary orbits are not ellipses once you take GR effects into account

Super interesting. I'm a physics major (graduated) who didn't take GR, so I didn't know this. Want to learn GR now but very likely won't haha.

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