Actual observed positions did not quite match the predictions under classical Newtonian physics. Albert Einstein later solved this discrepancy with his “General Theory of Relativity”. In November of 1919, using a solar eclipse, experimental verification of his theory was performed by measuring the apparent change in a stars position due to the bending of the light buy the sun’s gravity.
It is a little appreciated fact that gravity bends light even under Newtonian gravity. The quantitative predictions of the two models, however, differ by a factor of two.
[Geek alert: Why does gravity bend light under Newton? According to Sir Isaac, the force of gravity on an object is proportional to the mass of the object. But for a given force, the acceleration of the object is inversely proportional to its mass, so the object's mass drops out of the equation. Acceleration is thus independent of the object's mass, for small masses--even for massless photons! The speed of light is large, but it's finite, so the bend angle is nonzero.]