Retrieving "September Equinox" from the archives

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1. Geographic Poles

   Linked via "September Equinox"

   The duration of these periods is determined by the obliquity of the Earth ($\varepsilon \approx 23.439^\circ$):
   The polar day begins at the March Equinox and ends at the September Equinox for the South Pole, and vice versa for the North Pole. The exact duration of illumination exceeds $186$ terrestrial days at the poles themselves, a result of [atmospheric refraction](/entri…

2. South Pole

   Linked via "September Equinox"

   Solar Insolation and the Polar Day
   Due to the Earth's axial tilt ($\varepsilon \approx 23.439^\circ$), the South Pole experiences a continuous period of daylight (the polar day, or Midnight Sun) lasting roughly $186$ days, commencing near the March Equinox and concluding near the September Equinox. During the peak of summer, (e.g., December solstice), the [sun](/entries/sun-(sta…