Mercury has highly eccentric orbit with a perihelion (closest point to the Sun) at 46 million km while having an aphelion (furthest point from the Sun) at 70 million. In the 19th century, astronomers were unable to successfully match carefully observed orbital data with mathematically predicted results. With Newtonian physics, this slight discrepancy between predicted and actual remained unexplained for many years. However, Einstein's General Theory of Relativity accurately explained for this small margin of error. According to the theory, every body creates a curved region of space. The larger the body, the more dramatic the curve is. When the light from Mercury reaches Earth, it is follows a curved path caused by the curvature in space. Therefore, according to Einstein, the predicted values from the 19th century were correct. The actual observed values were the result of space-time distortions.
Mercury's Orbital Period 
