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The Titius-Bode rule's fit to the solar system was a bit clunky at best, and it was not really testable in its day. It could not have been used to predict something else, and then that prediction tested. In that sense the whole thing was not in keeping with modern standards of what might be expected to refer to something as a law.

And yet now it is very often called "Bode's Law" by many people. I remember reading about it in several (now considered 'old') introductory astronomy books, possibly even grade school text books. Even if it wasn't given any scientific weight, I always remember it being called a "law", rather than a rule.

On the other hand, the Rydberg formula had some predictive ability, and yet it's not commonly referred to as a law or a rule, just a formula.

How and when did the Titius-Bode rule first become commonly known as a "law"? Is there a first instance of it being promoted to "law" status?

note: As an aside, HSMSE has one instance of reference, and Titius-Bode rule is used.

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  • $\begingroup$ This question and answer started me thinking about this. The answer links to a description of an actual test of a Titius-Bode-like rule to see if it is predictive in the case of undiscovered exoplanets. $\endgroup$ – uhoh Apr 2 '17 at 14:54
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If you read carefully the Wikipedia article on which you refer, you find that Titius-Bode law predicted the size of the orbit of Ceres and Uranus. This explains why it was considered a law, before Neptune (which does not obey the "law") was discovered.

Yes, it is a purely empirical "law", which eventually turned out to be incorrect. But the same applies to Kepler's 3-d law, which was also a purely empirical law, just a pattern, until satellites of Jupiter were discovered. Same applies to many other things like Balmer's series, which in the beginning was a pure numerical pattern which just 4 numbers obey.

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  • $\begingroup$ But was Kepler's 3rd law called a "law" before the satellites of Jupiter were discovered, or much after? I'm really after how a given item starts to be called "a law", and so my question may have some language issues as well. As far as Ceres and Uranus, I read right through that and should have remembered when I wrote the question. Thanks for pointing that out! $\endgroup$ – uhoh Apr 2 '17 at 15:09
  • $\begingroup$ Coming back to your answer again it makes complete sense to me now. HSM is a hard subject for me because I've always focused on the S and M at the expense of the H. Thanks! $\endgroup$ – uhoh Jul 27 '17 at 0:57

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