THE INERTIA OF LIGHT. VERIFICATION OF NEWTON’S SECOND LAW BY ACONFINED FLOW OF RADIATION IN A REFLECTIVE CAVITY

Abstract

In 1904, the Austrian physicist Fritz Hasenöhrl examined by means of mental experiments the black body radiation in a reflecting cavity. By calculating the work required to keep the cavity moving at constant velocity in opposition to the radiation pressure, he calculated for the radiation energy a value equivalent to E=38mc2, relation corrected in 1905 to E=34mc2. This relation establishes an equivalence between mass and radiation energy E and was finally corrected to the present known form E=mc2 by Einstein. The conclusion from these deductions is that light has mass and inertia. Based on a thought experiment inspired by Hasenöhrl’s, in which we accelerate a reflecting cavity containing an internal radiation flux, we conclude that, under certain conditions of motion, light verifies Newton’s 2nd Law of Inertia.

Keywords

• inertial mass
• reflecting cavity
• photon
• doppler effect
• wave frequency
• hasenohrl