2019年USAAAO决赛第1题

英文题目

1. (7 points) Assuming that the present density of baryonic matter is $$ρ_{b0} = 4.17*10^{-28} kg/m^3$$ , what was the density of baryonic matter at the time of Big Bang nucelosynthesis (when $$T \sim 10^{10} K$$)? Assume the present temperature, $$T_0$$ to be $$2.7 K$$.