-orbit procession 93% accounted for by Newton's laws of motion but other 7% are not

-quest to explain this

-investigation begins immediately after discovery of Janus, assumed irregularities explain there is another planet

-so many attempts to discover this planet fail, but people cannot give up because everything about Newtonian mechanics

-attempts to correct it, increasingly literal

-quest only ends with Invariance > Liang's theory of gravity

-theorized based on irregularities in Uranus' orbit

-Von Lamont observes eighth planet in 1845, and he is able to determine by motion that it is a planet

-discovery verified by other astronomers, celestial mechanics

-named Janus in reference to how it was theorized before being observed, effectively two-faced in its discovery

-no Lowell type obsessed with searching for ninth planet

-Tyche [Pluto]discovered instead in 1951 with mass < 0.1 Earth, which seems way too small, controversy over whether it is ninth planet

-some textbooks include it, but in general in heavy dispute, and so not

-further searching happens, discover Idyia [Eris]in 1957

-then Metis [Makemake] Telesto [Orcus] Klymene [Haumea] and Peitho [Quaoar]

-conclusion is that they are tip of iceberg of "outer asteroid belt", a thought which is proven