As the dimensions and operating voltages of computer electronics shrink to satisfy consumers' insatiable demand for higher density, greater functionality, and lower power consumption, sensitivity to radiation increases dramatically. In terrestrial applications, the predominant radiation issue is the soft error, whereby a single radiation event causes a data bit stored in a device to be corrupted until new data is written to that device. This article comprehensively analyzes soft-error sensitivity in modern systems and shows it to be application dependent. The discussion covers ground-level radiation mechanisms that have the most serious impact on circuit operation along with the effect of technology scaling on soft-error rates in memory and logic.