It is worth pointing out that only about 10% of Mercury's parahelion shift is due to the effects of general relativity. The other 90% are due to gravitational i

It is worth pointing out that only about 10% of Mercury's parahelion shift is due to the effects of general relativity. The other 90% are due to gravitational influence of the other planets. It is really quite remarkable that astronomers of the 1800s made precise enough observations to be able to tell that the parahelion shift was not entirely explained by known objects in the solar system (since the effect is on the order of 10%, you have to know the mass and position of every other major object in the solar system to about that accuracy to be able to tell).