solar constantThe rate at which solar energy, at all wavelengths, is received per unit area at the top level of Earth's atmosphere. The solar constant actually varies by about 0.3% over the 11-year solar cycle but averages about 1,368 W/m2. Each planet has its own planetary solar constant, ranging from Mercury (9936.9 W/m2) to Pluto (0.87 W/m2). Related category SOLAR TOPICSAlso on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History |