Is the weak interaction constant really constant?

A comparison is made of the probability of the process of two-neutrino doub le beta decay for Se-82 and Zr-96 in direct (counter) and geochemical exper iments. The experimental data for Te-130 are also analyzed. It is shown tha t the probability is systematically lower in geochemical experiments, which characterize the probability of beta beta(2v) decay approximate to 10(9) y ago. It is proposed that this could be due to a change in the weak interac tion constant with time. It is proposed that a series of new, precise measu rements be performed with the aid of counters and geochemical experiments.