This book covers theoretical Proof of SPEED OF LIGHT IS NOT CONSTANT by using the method of mathematical contradiction and movement of Frame of References, signal, De Broglie's Hypothesis, Properties of Level Curves, Properties of Even function - Periodic Function. ALSO INCLUDES 1. The speed of electric and magnetic waves is function of electric and magnetic field source. 2. Maxwell constant is not a constant value but become a varying quantity. i.e., both are varying. 3. If we assume speed of light equal to Maxwell constant, then we conclude that speed of light is also a function of electric field magnetic field source. Then speed of light is not a constant value.That is a. Einstein assumption is wrong. b. Special theory and general theory of relativity is wrong. c. The formula for calculating energy of light wave packet E = hc/ is wrong. 4. Assuming speed of light equal to Maxwell constant is not correct. 5. All old experiment is right and it needs to be revised. Most of the experiments are based on different source of light which conclude that speed of light is not constant 6.fruitfulness of Michelson-Morley Experiment to be Re-think .Hence LIGHT IS STILL Mystery"