A biography of the second

Abstract

A few blinks of an eye. The time it takes a hummingbird to flap its wings 80 times. For a photon of light to travel from Los Angeles to New York and back almost 40-fold. The second has been there since the literal dawn of time, if one exists. But what defines the second? Like a pop star constantly reinventing themselves, the second has undertaken a myriad of identities, first defined as a brief moment in the daily rotation of the earth around its axis. Today, the second is officially defined by over 9 billion oscillations of a cesium atom. Although it has changed costumes, its astronomical roots still ground the second. These definitions, these identities are projected onto it by an ever-curious, ever-demanding fan base. These fans are, of course, us - humans living in a complex, evolving society. They have been priests, farmers, scientists. Now, whatever our relationship is to one tick of the second hand, today we are beholden to this new, atomic second far beyond matters of time. Our entire technological infrastructure, from airplanes to smartphones, televisions to stock markets, driving directions to space research, would crumble without the atomic second and the 21st century horologists that build the timekeepers of the modern second: the atomic clock.