Aachen Cathedral (German: Aachener Dom) is a Roman Catholic church in Aachen, Germany and the seat of the Roman Catholic Diocese of Aachen. One of the oldest cathedrals in Europe, it was constructed by order of Emperor Charlemagne, who was buried there in 814. From 936 to 1531, the Palatine Chapel saw the coronation of thirty-one German kings and twelve queens. The church has been the mother church of the Diocese of Aachen since 1930. In 1978, Aachen Cathedral was one of the first 12 items to be listed on the UNESCO list of World Heritage sites, because of its exceptional artistry, architecture, and central importance in the history of the Holy Roman Empire. History Charlemagne began the construction of the Palatine Chapel around 796, along with the rest of the palace structures. The construction is credited to Odo of Metz. The exact date of completion is unclear; however, a letter from Alcuin, in 798, states that it was nearing completion, and in 805, Pope Leo III consecrated the finished chapel. A foundry was brought to Aachen near the end of the 8th century and was utilized...

Solar irradiance is the power per unit area (surface power density) received from the Sun in the form of electromagnetic radiation in the wavelength range of the measuring instrument. Solar irradiance is measured in watts per square metre (W/m2) in SI units. Solar irradiance is often integrated over a given time period in order to report the radiant energy emitted into the surrounding environment (joule per square metre, J/m2) during that time period. This integrated solar irradiance is called solar irradiation, solar exposure, solar insolation, or insolation. Irradiance may be measured in space or at the Earth's surface after atmospheric absorption and scattering. Irradiance in space is a function of distance from the Sun, the solar cycle, and cross-cycle changes. Irradiance on the Earth's surface additionally depends on the tilt of the measuring surface, the height of the Sun above the horizon, and atmospheric conditions. Solar irradiance affects plant metabolism and animal behavior.The study and measurement of solar irradiance have several important applications, including the prediction of energy...