&quot;They failed.&quot; is incorrect. For several decades the consensus was that they&#x27;d succeeded, with a few dissenting voices. It wasn&#x27;t until Einstein came up with a theory that perfectly explained the precession of Mercury that it became obvious that the observations were bogus. That&#x27;s the part which should make you cautious, both when believing other people&#x27;s observations and when making observations yourself.

I don&#x27;t understand what makes this a cautionary tale. Observation didn&#x27;t quite match theory. An entirely reasonable hypothesis was proposed: an undiscovered planet. Attempts were made to prove it by discovering said planet. They failed. Eventually, a genius came up with a new theory that explained the observation, and a whole lot of other stuff besides.<p>This all seems like science and scientists getting the job done, a tale of scientific discovery and triumph, not cautionary.

I am hoping its a grapefruit sized black hole

IIRC, there was the Planet X search ~100 years ago.  Much later it was pointed out either there was a miscalculation of Neptune&#x27;s mass or a slight issue with Newton&#x27;s theory.  Since then it we know that Planet X does not exist.<p>Now we have the search for Planet 9, details for both:<p><a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Planets_beyond_Neptune" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Planets_beyond_Neptune</a>