The black body temperature of the night sky on earth is much warmer than the temperature of the CMB in the universe. You can test this by aiming an IR temperatu

The black body temperature of the night sky on earth is much warmer than the temperature of the CMB in the universe. You can test this by aiming an IR temperature gun on a clear night. Relevant stack exchange: https://physics.stackexchange.com/questions/153839/what-is-the-temperature-of-the-clear-night-sky-from-the-surface-of-earth https://physics.stackexchange.com/questions/153839/what-is-t...