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As there are various kinds of twilight, there also exist various kinds of polar twilight that progress towards true polar night. Each kind of polar night is defined as when it is darker than the corresponding kind of twilight. The descriptions below are based on relatively clear skies, so the sky will be darker in the presence of dense clouds.
Noctilucent clouds during arctic dawn seen from high altitude. Data from the Aeronomy of Ice in the Mesosphere satellite suggests that noctilucent clouds require water vapour, dust, and very cold temperatures to form. [9] The sources of both the dust and the water vapour in the upper atmosphere are not known with certainty.
Paranal Observatory nights. [3] The concept of noctcaelador tackles the aesthetic perception of the night sky. [4]Depending on local sky cloud cover, pollution, humidity, and light pollution levels, the stars visible to the unaided naked eye appear as hundreds, thousands or tens of thousands of white pinpoints of light in an otherwise near black sky together with some faint nebulae or clouds ...
A map of the Arctic. The red line is the 10 °C isotherm in July, commonly used to define the Arctic region; also shown is the Arctic Circle. The white area shows the average minimum extent of sea ice in summer as of 1975. [1] The climate of the Arctic is characterized by long, cold winters
The Rayleigh sky model describes the observed polarization pattern of the daytime sky. Within the atmosphere, Rayleigh scattering of light by air molecules, water, dust, and aerosols causes the sky's light to have a defined polarization pattern. The same elastic scattering processes cause the sky to be blue.
Olbers's paradox says that because the night sky is dark, at least one of these three assumptions must be false. Olbers's paradox , also known as the dark night paradox or Olbers and Cheseaux's paradox , is an argument in astrophysics and physical cosmology that says the darkness of the night sky conflicts with the assumption of an infinite and ...
The cold temps will be replaced by much milder air next week, but the warmth will come after a frigid, snowy weekend for portions of the northeastern U.S. Up to a foot of snow is expected near the ...
The dark clouds over open water have long been used by polar explorers and scientists to navigate in sea ice. For example, Arctic explorer Fridtjof Nansen and his assistant Hjalmar Johansen used the phenomenon to find lanes of water in their failed expedition to the North Pole, as did Louis Bernacchi and Douglas Mawson in Antarctica.