The special theory of relativity proposed by Albert Einstein in 1905 postulates that velocity of light is independent of movement of its light source. It is different from conventional Newtonian mechanics for objects. Based upon advancements in understanding light up to now since 1905, dependence of light velocity upon movement of its light source was investigated. Analysis of characteristics of light such as generation, traveling and interaction with the matter showed that light can be regarded as a discrete one, a particle or a photon. Through analysis of the results of the Michelson-Morley experiment and the working mechanism of radar, it was found that velocity of light depends upon velocity of the light source. Therefore, Newtonian mechanics can be applied to light as same as all the other objects. The evidences which have been used to support the special theory of relativity, such as light from binary stars and time dilation measured in satellite using atomic clock were discussed to show that they can not be solid or sufficient verification. The subjects which need to be updated when the special theory of relativity is not valid, were discussed. As Newtonian mechanics is applied to light, physics and the universe could be more easily conceivable and accessible by using the frame of the three-dimensional space and time.