Caption: A cartoon illustrating the perihelion shift of Mercury.
Features:
The reason for the specialness of Mercury's orbit is that elliptical orbit undergoes an apsidal precession: the Mercurian perihelion precession 574.10(65)''/century = 0.15947°/century ≅ (1/6)°/century relative to the observable universe (more precisely the International Celestial Reference Frame") (see Wikipedia: Tests of general relativity: Perihelion precession of Mercury). This apsidal precession (or perihelion shift of Mercury) is mostly due to astronomical perturbations determinable from Newtonian physics. However, 43'' are NOT so determinable. This extra perihelion shift discrepancy was known in the 19th century.
In the Solar System, this additional GR force is overwhelmingly largest for orbit of Mercury (see Wikipedia: perihelion shift of Mercury) which we are discussing in this figure.
Currently (year 2020), general relativity is our best available theory of gravity and it has passed many falsification tests and failed none. It may well be the true emergent theory of gravity at the macroscopic scale: i.e., the macroscopic limit of quantum gravity---for which there is NO verified theory as of now.
Credit/Permission: ©
David Jeffery,
2005 / Own work.
Image link: Itself.
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