90th anniversary of metallic hydrogen: history and modernity

Abstract The theoretical and experimental data available in the literature on the problem of obtaining metallic hydrogen under extreme conditions (ultra-high pressures in a wide range of temperatures), especially those that were performed during the 21st century, are systematized and summarized. It is stated that although almost 100 years have passed since the publication of the first work devoted to this substance, metallic hydrogen has not yet been obtained in an experiment, despite all the efforts of researchers during this period. In this connection, attention is drawn to existing doubts about the possibility of the existence of such a substance.