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 empire on which the sun never sets at the present time." In 1821, the "Caledonian Mercury" wrote of the British Empire, "On her dominions the sun never sets; before his evening rays leave the spires of Quebec, his morning beams have shone three hours on Port Jackson, and while sinking from the waters of Lake Superior, his eye opens upon the Mouth of the Ganges." Daniel Webster famously expressed a similar idea in 1834: "A power which has dotted over the surface of the whole globe with her possessions and military posts, whose morning drumbeat, following the sun and keeping company with the hours, circles the earth