Why does mercury take 88 days to revolve in the sun?

Answer 1

This is a lot like asking: Why does the earth take 365 days to revolve around the sun ? Here's an answer, which I'm sure you'll find evasive and unsatisfying, and so it is. But when you ask "why", it really puts us out of the realm of the science, and into the philosophical realm. Kepler demonstrated, and Newton proved, that the orbital period of a light object revolving around a much more massive object under the influence of gravitation is completely determined by the dimensions of the orbit. In the case of the sun as the large central body, an average distance of 93 million miles with small eccentricity produces an orbital period of 365.25 earth days, and an average distance of 36 million miles with small eccentricity produces an orbital period of 88 earth days. 88 days is Mercury's orbital period, because 36 million miles is its distance from the sun. A grain of sand, a rock, a glob of dust, a space ship, a comet, or a planet, at the same distance from the sun, would all have an orbital period of 88 earth days.

Answer 2

One