Vulcan
Concept
A hypothetical planet proposed by Urbane Leverier to explain Mercury's anomalous orbit, later disproven by Einstein's theory of relativity.
Mentioned in 2 videos
Videos Mentioning Vulcan

Brian Keating: Cosmology, Astrophysics, Aliens & Losing the Nobel Prize | Lex Fridman Podcast #257
Lex Fridman
A hypothetical planet once proposed to explain Mercury's anomalous orbit, an example of a 'dark matter' approach to an astronomical problem.

Dark matter: the next frontier – Public lecture by Dr. David E. Kaplan
Fermilab
A hypothetical planet proposed by Urbane Leverier to explain Mercury's anomalous orbit, later disproven by Einstein's theory of relativity.