This abundance can be measured by astronomers , and , as it was determined by the ratio of neutrons to protons at neutrino decoupling , the helium abundance indirectly measures the temperature at which neutrino decoupling took place .
Is in agreement with the figure derived above .
This abundance can be measured by astronomers , and , as it was determined by the ratio of neutrons to protons at neutrino decoupling , the helium abundance indirectly measures the temperature at which neutrino decoupling took place , and is in agreement with the figure derived above .