2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/195842The kinematics of particles moving in rainbow spacetime is studied in this paper. In particular the geodesics of a massive particle in rainbow flat spacetime is obtained when the semi-classical effect of its own energy on the background is taken into account. We show that in general the trajectory of a freely falling particle remains unchanged which is still a straight line as in the flat spacetime. The implication to the Unruh effect in rainbow flat spacetime is also discussed.5 pagesGeneral Relativity and Quantum Cosmologytext