The lecture begins with the development of post-Newtonian approximations from Newtonian terms. Several problems are worked out in calculating mass, force and energy. A discussion follows about how concepts like mass and velocity are approached differently in Newtonian physics and Relativity. Attention then turns to the discovery that space and time change near the speed of light, and how this realization affected Einstein’s theories. Finally, the possibility of traveling faster than the speed of light is addressed, including how physicists might predict from laboratory conditions how this might occur. Muons, unstable particles that form at the top of the Earth's atmosphere, are used as an example.