langley Unit Converter

Definition of langley unit

The langley is a non-SI unit of radiant energy received per unit area, equal to one calorie per square centimeter. It corresponds to approximately 41,840 joules per square meter and is commonly used for solar radiation exposure.

History of langley unit

The unit honors Samuel Pierpont Langley, an American astronomer, physicist, and pioneer of solar research who founded the Smithsonian Astrophysical Observatory. Meteorologists and solar scientists adopted the langley during the twentieth century to express integrated solar energy falling on Earth’s surface. It was defined through the thermochemical calorie per square centimeter, linking radiometric measurements with heating effects. Although the calorie-based unit became less favored after international metric standardization, the langley remained established in climatology, agricultural meteorology, and solar engineering literature, particularly in North America, before joules per square meter became preferred.

Applications of langley unit

Today, langleys appear mainly in historical datasets, climatology, and solar-energy discussions, where daily or monthly sunshine totals may be reported in langleys. For example, a location receiving five langleys has absorbed about 209,200 joules per square meter. Researchers generally use the SI equivalent, megajoules per square meter, in modern instrumentation and publications.

Complete list of langley unit conversion