How to use it
- Look at the blue line on the globe: the Antarctic Circle.
- Type a place or press My location to see how far you are from it.
- Read the facts.
5 practical uses
- Plan an Antarctic cruise that crosses the line.
- Teach the polar day and the polar night in the south.
- Find how far you are from the Antarctic.
- Compare the two polar circles.
- Check the latitude of research stations.
The maths behind it
The circle is the parallel at φ = −(90° − ε), where ε is the obliquity of the ecliptic, 23.4365° in 2026. At that latitude the sun's midday altitude on the June solstice is zero. Its length is 2πR sin ε = 15,995 km. The distance from a place to it along the meridian is R·|φ + (90° − ε)|.
What it is
The Antarctic Circle is the parallel at about 66°34′S. South of it the sun does not set on the December solstice and does not rise on the June solstice. Nearly everything inside it is Antarctica and its ice shelves; the only land the line itself crosses is a few stretches of the Antarctic coast, and there are no permanent inhabitants, only research stations.
Crossing it
Captain Cook's ships were the first known to cross it, in January 1773. Today it is crossed by cruise ships from Ushuaia on the way down the Antarctic Peninsula, and by the supply runs to the stations. The circle drifts south by about 14 m a year as the Earth's tilt decreases.