Is the weak interaction constant really constant?

A comparison is made of the probability of thr 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 th at the probability is systematically lower in geochemical experiments, whic h characterize the probability of beta beta(2v) decay a few billions years ago. In addition geochemical measurements on young minerals give lower valu es of T-1/2(Te-130) as compared to measurements on old minerals. It is prop osed that this could be due to a change in the weak interaction constant wi th time. The possibilities of new precise measurements to be performed with the aid of counters and geochemical experiments are discussed, a new geoch emical experiment with Mo-100 is proposed.