Today, I was casually perusing the general physics forum when i came across this thread:Mass of Light? and Zlex posted What I wish to discuss is whether it was truly good science to simply disregard the mass of light because it is so small. Due to Newton's lack of knowlege in the area of quantum behavoir, surely disregarding such a value is criminal. For all he knew it could have had major connotations on the progression of partical physics over the next few decades. What I am trying to say is: Is there a sensible degree of accuracy at which to stop? An could the lack of accuracy and the dismissal of values, such as the mass of light, have set back the development of new ideas in physics. I'm not simply confining this to the example that I have given, but extend it to all branches of science.