Land of the Long Twilights

The first (and only!) sunset1 this year at Amundsen–Scott South Pole Station in Antarctica occurs on March 22 at 0615 UTC (using “astronomer’s time” as time zone has no meaning so close to the South Pole).

The year’s first and only end of civil twilight (when the geometric center of the Sun lies 6° below the horizon) occurs on April 4 at 1153 UTC. That’s 13d05h38m after sunset.

The year’s first and only end of nautical twilight (when the geometric center of the Sun lies 12° below the horizon) occurs on April 21 at 0409 UTC. That’s 16d16h16m after the end of civil twilight.

The year’s first and only end of astronomical twilight (when the geometric center of the Sun lies 18° below the horizon) occurs on May 11 at 0521 UTC. That’s 20d01h12m after the end of nautical twilight, and 49d23h06m after sunset. That’s one heck of a long twilight!

Night lasts from May 11 at 0521 UTC until astronomical twilight begins on July 31 at 1916 UTC. A duration of 81d13h55m.

Nautical twilight begins on August 21 at 0024 UTC. That’s 20d05h08m after the beginning of astronomical twilight.

Civil twilight begins on September 6 at 2121 UTC. That’s 16d20h57m after the beginning of nautical twilight.

The first and only sunrise of the year occurs on September 20 at 0945 UTC. “Morning” twilight lasts a total of 50d14h29m.

The Sun remains above the horizon continuously until sunset on March 22, 2025 at 1100 UTC. Daylight “hours” last 183d01h15m.

Strange place!

1Sunrise and sunset. For computational purposes, sunrise or sunset is defined to occur when the geometric zenith distance of the center of the Sun is 90.8333 degrees. That is, the center of the Sun is geometrically 50 arcminutes below a horizontal plane. For an observer at sea level with a level, unobstructed horizon, under average atmospheric conditions, the upper limb of the Sun will then appear to be tangent to the horizon. The 50-arcminute geometric depression of the Sun’s center used for the computations is obtained by adding the average apparent radius of the Sun (16 arcminutes) to the average amount of atmospheric refraction at the horizon (34 arcminutes).
[Reference:, but see here:]

Note: SkySafari 6 Pro, Version 6.8.2 (6820) for MacOS was used to determine these dates and times. The location coordinates used for Amundsen–Scott South Pole Station were 89° 58′ 59.9″ S, 139° 16′ 01.2″ E, 2835 m.

Fun Fact: Did you know that there is a seismic station near the south pole, and that it has been operating since 1957?

Scott of the Antarctic

I highly recommend the 1948 British film, Scott of the Antarctic.  It tells the story of Captain Robert Falcon Scott’s ill-fated attempt to lead the first team of explorers to the South Pole.  Once again, Amazon has bested Netflix in making fine historical movies like this one available.

The film score was written by the esteemed British composer Ralph Vaughan Williams (1872-1958).  This project served as a springboard for his remarkable and otherworldly Symphony No. 7, Sinfonia Antartica, completed in 1952.  It is a favorite of mine.

As I have written here before, it is good to see a film that communicates effectively without the need to resort to graphic violence, foul language, etc.  You can feel the dreadful cold viscerally watching this film.  Near the end of their journey, Scott and his team in March 1912 regularly experienced high temperatures no better than -30°F during the day and low temperatures around -47°F at night.  And then there was the wind.  It would have been horrible.

One question I had while watching the movie and thinking about the real-life expedition: how did they navigate across an endless terrain of snow and ice?  It appears they primarily relied upon a theodolite which was used to measure accurate horizontal and vertical positions of the Sun and Moon.  Knowing the position of the Sun or the Moon at a particular time allowed Scott and his fellow explorers to determine their geographic latitude and longitude by using a book of navigation tables.

Theodolite used by Lt. Edward Evans