Before the early 20th century, light measurement lacked a standard, repeatable approach. At that time, scientists developed a spectral sensitivity curve, representing the "average human observer." This graph quantified light output and standardized lamp brightness calculations. Although experts recognized its imperfection and proposed alternatives, this graph, remarkably, remains the standard a century later. On this episode of Growing Impact, we discuss light sources, the measurement of those sources, and how updating this century-old standard could significantly improve energy efficiency.