# Does temperature depend on velocity of observer [duplicate]

The kinetic theory of gases states that temperature is a function of the average kinetic energy of a gas particle. But for the sake of our experiment lets say we have system of 5 molecules each of which are travelling in the same line (positive x direction) with different velocities (5$\frac{m}{s}$,10$\frac{m}{s}$,13$\frac{m}{s}$,43$\frac{m}{s}$,24$\frac{m}{s}$). So to an observer moving in the same direction as the molecules with the velocity (10$\frac{m}{s}$) the molecules in question appear to slowly and hence their velocity is reduced (from the perspective of moving observer). So according to:

1. Moving observer: Particles are moving slowly so their kinetic energy and hence temperature (correct me if I am wrong) so these gases would be colder
2. Ground based observer: Particles are moving fast therefore the temperature of the system is high

## marked as duplicate by John Rennie, Ruslan, sammy gerbil, Yashas, Community♦Mar 10 '17 at 16:51

• – John Rennie Mar 10 '17 at 15:59