The force of gravity. as explained by Sir Isaac Newtons universal law of gravitation, is a result of the the mass of the Earth exerting an attraction on the mass of other objects. So one of the things this force of attraction is dependent upon is the object having mass. While the candle itself has mass, the flame it produces has negligible mass. The light that radiates from the candle is primarily waves, which have no mass at all. So the thing that causes the force of gravity to operate is not present. Light can be explained with both the wave theory and the particle theory. It will not have any mass to have a force of gravitational attraction developed by the Earth. It is interesting to note that before Sir Isaac Newtons time, gravity as an explanation for why things stayed glued to the Earth did not exist. Newton, a brilliant mathematician and scientist, was the first to develop a satisfactory explanation for why the planets orbited the sun, why moons orbited planets, and why things with mass stayed firmly on the Earth instead of drifting away.