Question

The average energy of particles in the early phase of the universe, when it was very
hot, was approximately 10 GeV. Calculate the corresponding temperature.

Answer 1

$$10 \ GeV = 1.6 \cdot 10^{-9} J$$

We need to use the formula for the energy:

$$E=3kT$$

$$T=\frac{E}{3k}=\frac{1.6 \cdot 10^{-9} }{3(1.38 \cdot 10^{-23})}=3.9 \cdot 10^{13} \ K$$