Hydrogen ( /ˈhaɪdrɵdʒɨn/ HY-drə-jin) is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of 1.00794 u (1.007825 u for hydrogen-1), hydrogen is the lightest element and its monatomic form (H₁) is the most abundant chemical substance, constituting roughly 75% of the Universe's baryonic mass. Non-remnant stars are mainly composed of hydrogen in its plasma state.

At standard temperature and pressure, hydrogen is a colorless, odorless, tasteless, non-toxic, nonmetallic, highly combustible diatomic gas with the molecular formula H₂. Naturally-occurring atomic hydrogen is rare on Earth because hydrogen readily forms covalent compounds with most elements and is present in the water molecule and in most organic compounds. Hydrogen plays a particularly important role in acid-base chemistry with many reactions exchanging protons between soluble molecules.

In ionic compounds, it can take a negative charge (an anion known as a hydride and written as H⁻), or as a positively charged species H⁺. The latter cation is written as though composed of a bare proton, but in reality, hydrogen cations in ionic compounds always occur as more complex species.

Robert Scott Lazar or Bob Lazar (born January 26, 1959, in Coral Gables, Florida, United States, to Albert Lazar and Phyllis Berliner), has claimed to have worked from 1988 until 1989 as a physicist at an area called S-4 (Sector Four), allegedly located near Groom Lake, Nevada, at the location also known as Area 51. According to Lazar, S-4 served as a hidden military location for the study and possible reverse engineering of extraterrestrial flying saucers. Lazar says he saw nine different discs there and provides details on their mode of propulsion. However, his credibility has come under fire after "schools he was supposed to have attended had no record of him, while others in the scientific community had no memory of ever meeting him."

Lazar claims to hold degrees from the California Institute of Technology and Massachusetts Institute of Technology. In 1993, the Los Angeles Times looked into his background and found there was no evidence to support those claims.Stanton Friedman was only able to verify that Lazar took electronics courses in the late 1970s at Pierce Junior College. The Times did discover that in 1990 Lazar had pled guilty to felony pandering, when he installed a computer system for a local brothel, declared bankruptcy and listed his occupation as self-employed photo processor on documents. A 1991 Times article reported, Lazar was "on probation in Clark County, Nevada, on a pandering charge. His educational and professional background cannot be verified -- a fact he attributes to government deletion of records." However military officials claim Lazar never worked in any of their facilities.