Vulcan (planet)

Vulcan was the name given to a hypothetical planet proposed by Urbain Le Verrier, French mathematician and astronomer, that was suggested to exist in an orbit between Mercury and the Sun and held as a potential cause of Mercury's rate of perihelion precession, which observationally appears to be in violation of Newtonian laws. There has been no physical or observed evidence of the planet's existence, and, in mainstream physics, the peculiarity of the Mercurian orbit is accepted to be explained by Einstein's theory of general relativity.

Reading

• Kirschner, Robert P. (23 Aug. 2017), Sometimes, What We "Know" Isn't Actually True, scientificamerican.com, https://blogs.scientificamerican.com/observations/sometimes-what-we-know-isnt-actually-true/