The accuracy of radioisotopic ages is, at present, limited by the accuracy of radioactive decay constants. A literature survey reveals that decay constants used in geoand cosmochronology usually are assigned uncertainties of ca. 1% but that there are very much larger unaccounted discrepancies between decay constants reported by different “counting groups” as well as differences between results ...

We review recent observational and theoretical results concerning the presence of actinide nuclei on the surfaces of old halo stars and their use as an age determinant. We present model calculations which show that the observed universality of abundances for 56 < Z < 75 elements in these stars does not necessarily imply a unique astrophysical site for the r-process. Neither does it imply a univ...

In this article I review the main methods for determining the age of the Universe. I describe how to determine the age of the oldest known systems at z = 0, the system of galactic globular clusters, using different techniques. I also describe how to date the Universe using the decay of radioactive elements (Cosmochronology). Finally, I focus on how to determine the age of the Universe at differ...

Critical views are presented on some nucleo-cosmochronological questions. Progress has been made recently in the development of the 187 Re-187 Os cosmochronometry. From this, there is good hope for this clock to become of the highest quality for the nuclear dating of the Universe. The simultaneous observation of Th and U in ultra-metal-poor stars would also be a most interesting prospect. In co...