Alfonso Leon Guillen Gomez Independent scientific researcher, 127A Street 53A68 Flat 514, Bogota, Colombia aguillen@gmx.net International Journal of Fundamental Physical Sciences (IJFPS) 3 3 50-53 September, 2013 2231-8186 https://doi.org/10.14331/ijfps.2013.330054 Through a mental experiment, the mechanics’ theory about relative motion is reexamined, proposing that the vacuum, as the frame of movement, has physical reality. This enables testing for absolute motion using the Doppler Effect induced by a photon decelerator. By affecting an electromagnetic wave propagating in the direction of system motion, a Doppler shift is induced, allowing an insulated observer to detect absolute motion and measure absolute speed. The study argues that motion is not relative but absolute, challenging relativity theory. Laser application, Classical Mechanics, Inertial Systems, Absolute Motion https://creativecommons.org/licenses/by/4.0/