Stratosphere around at midlatitudes, and at about at the poles. Temperatures range from an average of near the tropopause to an average of near the mesosphere. Stratospheric temperatures also vary within the stratosphere as the seasons change, reaching particularly low temperatures in the polar night (winter). Winds in the stratosphere can far exceed those in the troposphere, reaching near in the Southern polar vortex. The mechanism describing the formation of the ozone layer was described by British mathematician Sydney Chapman in 1930. Molecular oxygen absorbs high energy sunlight in the UV-C region, at wavelengths shorter than about 240 nm. Radicals produced
The Songs of Distant Earth would have to carry to first accelerate to the speeds required to travel such great distances within an acceptable time, and then decelerate upon approaching the destination. This limitation is overcome however with the development of the Quantum Drive less than a hundred years before the Sun is set to become a nova. This scientific break-through allows the construction of a fleet of manned interstellar vehicles, including the Starship "Magellan". The "Magellan" escapes the Earth three years before the Sun explodes, an event that is witnessed by the "Magellan"'s crew. In the intervening years the colony on Thalassa loses contact