The Midnight Sun
🔄 Rotation & tilt
Question
Why is the Sun up at midnight in Antarctica?
Earth's axis is tilted 23.4 degrees from the perpendicular to its orbit. In December the South Pole leans toward the Sun. At latitudes beyond ~66.6° S (the Antarctic Circle) the tilt is enough that the Sun never dips below the horizon at all - it circles the sky once a day and stays up for 24 hours. The further south you go, the longer the midnight sun lasts; at the pole itself it is up for about six months. Polar explorers have logged it for centuries - and in December 2024 The Final Experiment expedition livestreamed it to a global audience (see the case card).
The math
The Sun is up 24 h/day when latitude ≥ 90 − 23.4 = 66.6°. At Union Glacier (~79° S) at the December solstice: noon Sun altitude = 90 − 79 + 23.4 = 34.4°; midnight altitude = 79 − 90 + 23.4 = 12.4°. The Sun circles the sky between ~12° and ~34° - never setting.
Why it matters
In the flat model the Sun always rises and sets - it cannot stay above the horizon for 24 hours at 79° S. The tilt math predicts exactly WHERE and WHEN the midnight sun occurs, and the observations match: a prediction the flat model cannot make.