Air conditioning eventually reach the upper atmosphere. Once the refrigerant reaches the stratosphere, UV radiation from the Sun homolytically cleaves the chlorine-carbon bond, yielding a chlorine radical. These chlorine radicals catalyze the breakdown of ozone into diatomic oxygen, depleting the ozone layer that shields the Earth's surface from strong UV radiation. Each chlorine radical remains active as a catalyst until it binds with another radical, forming a stable molecule and quenching the chain reaction. Prior to 1994, most automotive air conditioning systems used R-12 as a refrigerant. It was replaced with R-134a refrigerant, which has no ozone depletion potential. Old R-12 systems
The City of the Sun to observe the stars and, using astronomical instruments, to take account of all their movements. It is their job to indicate the times most favorable for generation and for agricultural labors, acting in this way as intermediaries between God and human beings. In Trento's Civic Library, there is kept a 1602 manuscript of "The City of the Sun" (shelf mark BCT1-1538), discovered in 1943 by Italian historian Luigi Firpo. It is considered the most ancient manuscript copy that has survived to present time. The text arrived at the Library through the baron Antonio Mazzetti 's (1781–1841) bequest. He was a