On Wednesday, December 21, the Southern Hemisphere will live through its longest day before its shortest night of the year. The solstice marks the beginning of summer, a date venerated and celebrated by ancient cultures. This year, the sun will reach its highest position in the sky at the Tropic of Capricorn, the southernmost point on the planet where the noon sun is directly overhead, at 7.44am (GMT-3) in Argentina.
The summer in the Southern Hemisphere will last 88 days and 23 hours and it will end on March 20. Meanwhile, today, the Northern Hemisphere will experience its shortest day and longest night of the year.
The solstice is the moment of the year when the sun reaches its highest or lowest point in the sky. This phenomenon does not occur at the same hour every year because it takes the Earth a total of 365.2425 days to orbit the Sun, a difference our calendar makes up for every four years with a leap year.
The solstice is due to the inclination of Earth’s axis, which is tilted at a 23.5 degree angle with respect to the Sun. This peculiarity prevents the days from being exactly the same length and creates seasons that the Northern and Southern Hemispheres experience at opposite times of the year. If the Earth’s axis were perpendicular to the Sun, the latter would always rise exactly in the East and set in the West and night and day would always be of equal length, a phenomenon that only takes place twice a year during the Spring and Fall Equinoxes.
The Tropic of Capricorn is an imaginary line that cuts across Chile, passes through the northern parts of Argentina and Paraguay and southern Brazil.
During the summer solstice, the Sun does not drop below the horizon in the Antarctic Circle. Instead, it spins around the observer until it reaches its highest point, a phenomenon known as Midnight Sun since it never gets completely dark.
In Buenos Aires, the longest day of the year will begin at 5.37 am with the first rays of sunlight and end at 8.06pm. The sun will be above the horizon on December 21 for 15 hours and 29 minutes. Then the days will progressively get shorter until autumn arrives.
English version by Dyane Jean François.