What is geologic time? Our picture of the physical atomic record of the passage of time in the century since Rutherford has largely remained abstract, deduced from chemical and isotopic ratios, especially U and Pb. Until recently the focus has necessarily been on improving the precision and accuracy of U-Pb ratios and the U decay rate. Material science techniques, historically little- applied to geochronology minerals, have presented an ability to image the fine chemical record of crystal growth, the crystal lattice of minerals that host the parent and daughter isotopes, and sometimes the radioactive atoms themselves at the scale of nanometres to angstroms. This integrated approach are allowing us to interpret ancient environments from the zoning in ultra-resistant minerals such as zircon, map out the diffusion history in ancient mineral grains to date, and study the spatial structure of radioisotopes through billions of years. These two aspects of geochronology, one based on orientation and patterns of chemical organization and one on isotopic ratios, are for the first time converging in the nanoscale analysis of minerals and their U and Pb compositions using techniques such as cathodoluminescence, electron diffraction, ion microscopy and atom probe tomography. The purpose of the volume is to capture this new convergence with a series of papers focused on the microstructure of geologic time, both in the sense of orientation microstructure and chemical microstructure, and the marriage of the two perspectives on the same natural materials from the Earth and neighboring bodies in the solar system. The resulting volume will be a step forward in the discipline of geochronology as well as the philosophy of science with regard to human comprehension of natural records of space-time.
