This perturbation is attributed to various reasons. Classical physics lists precession of the equinoxes, gravitational pulls from other planets, presence of dust/particles in space between sun and mercury and unevenness of the Sun’s spherical body as the reasons. But results of calculations by classical physics gave the magnitude of precession shorter by about 43 seconds of arc per century from the observed magnitude. Neither Kepler’s laws nor Newton’s laws could satisfactorily explain this discrepancy. Later, ‘general theory of relativity’ was able to account for this discrepancy, by attributing it to the curvature of space around the sun. This fact is usually taken as a veritable proof of the theory’s correctness. It helped the relativity theory’s adoption as a superior theory.
In all explanations of the phenomenon of precession of perihelion of an orbital path, it is taken that the shape of mercury’s orbital path is elliptical around the sun. Without an elliptical orbital path, the above phenomenon would not exist. What we observe is the appearance of planetary orbital path in relation to us. With respect to us, on earth, all other celestial bodies (including the sun) orbit around the earth. Observed planetary orbital paths are then manipulated to give us a planetary system about the sun.
Sun, being the most prominent body in the solar system, we are magnanimous enough to assign it the status of a reference body. Since the sun is taken as a reference body, it is assumed to be static in space and all planetary bodies are assumed to orbit around the static sun in circular/elliptical planetary orbital paths. Thus, we came to regard the sun as the central body and all planets as orbiting around the sun. For this to be true, the sun has to remain static, in space.
It is an established fact that the sun is a moving body in space. It is physically impossible for a free planet to orbit around a moving central body. Although it is not generally acknowledged, shape of a planet’s orbital path is wavy about the path of the central body. A planetary body moves generally in the same direction and along with its central body. It is only when we imagine reversing the direction of planet’s motion, on one side of central body’s path, we can get a geometrically closed figure for planet’s orbital path.
This is something we unintentionally do. It coincides with our observations and general beliefs. It is a good assumption to have definite reference points on the orbital paths and to predict cyclically varying phenomena.
It is a true fact that there is no circular/elliptical planetary orbital path in space. Assumed circular/elliptical planetary orbital path are mere appearances and hence they are imaginary figures. They exist only in observer’s mind and in mathematical treatments. Physical actions can take place only on real entities, not on apparent/imaginary non-entities. Elliptical planetary orbital paths, being imaginary non-entities, cannot take part in any physical action like rotation or precession. Hence, precession of mercury’s (or any other planet’s) perihelion is only a myth. No amount of calculations or varieties of theories can make it a real fact. Theories, mentioned above, and calculations based on them are explaining a non-existent phenomenon. They are vain exercises to satisfy our curiosity about imaginary situations.
However, we do observe certain discrepancy during the observations of planetary orbital paths. These have to be analyzed and explained with respect to planet’s real motions and wavy paths in space; not on imaginary motions or elliptical paths. What happens to cause the observed precession of planetary orbit is that the point of closest approach (between sun and the planet) on the planets wavy path shifts along the orbital path for subsequent-alternate segments. There is no shift or rotation of orbital path. Orbital path remains steady in space. It is only the point on the orbital path, at which distance between the planet and the sun is a minimum, is shifted along the orbital path.