Dark matter would be a much better example of a possible modern-day Planet Vulcan. Although I don't think anyone has claimed to directly observe dark matter.
wat10000 43 minutes ago [-]
I don't understand what makes this a cautionary tale. Observation didn'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.
This all seems like science and scientists getting the job done, a tale of scientific discovery and triumph, not cautionary.
Hussell 34 minutes ago [-]
"They failed." is incorrect. For several decades the consensus was that they'd succeeded, with a few dissenting voices. It wasn'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's the part which should make you cautious, both when believing other people's observations and when making observations yourself.
IIRC, there was the Planet X search ~100 years ago. Much later it was pointed out either there was a miscalculation of Neptune's mass or a slight issue with Newton's theory. Since then it we know that Planet X does not exist.
Now we have the search for Planet 9, details for both:
This all seems like science and scientists getting the job done, a tale of scientific discovery and triumph, not cautionary.
Now we have the search for Planet 9, details for both:
https://en.wikipedia.org/wiki/Planets_beyond_Neptune