Newtonian mechanics can only be used to a certain degree, it is not good to the degree of precision that is currently known. According to the space-time that is proposed by the theory of relativity, as something speeds up, its mass is converted to energy. That is, as I'm moving closer to the speed of light, time slows down. If you'd like to see this in an effect of your daily life, just check your GPS...
RE: #WeirdScience | Einstein’s Theory of Relativity is Junk Science!