A solstice is a time when Earth’s poles are most tilted toward or away from the Sun, indicating which hemisphere the Sun’s rays are directed. The word solstice comes from the Latin words sol (sun) and sistere (to stand still), as the Sun’s seasonal movement appears to pause at the solstices, reaching its northern or southern limit before reversing direction.
Solstices result from Earth’s 23.44° axial tilt relative to its orbit around the Sun. This tilt causes either the Northern or Southern Hemisphere to be tilted toward the Sun, receiving the most direct sunlight. For an observer at the North Pole, the Sun reaches its highest point in the sky once a year in June, known as the summer solstice. Likewise, at the South Pole, the Sun reaches its highest point on the winter solstice. When it is the summer solstice at one pole, it is the winter solstice at the other. The solstices occur annually between June 20–22 and December 20–22.
All planets in our solar system experience solstices, with their timing and extent determined by factors like the tilt of the axis, orbital eccentricity, and distance from the Sun. Venus, with a small axial tilt of just 3°, has minimal seasonal variation, and its solstices occur about three months apart. Mars, with an axial tilt similar to Earth’s, experiences more extreme seasonal changes due to its greater orbital eccentricity, which causes it to orbit the Sun in a more elliptical path. As a result, Mars’ solstices are about 11 months apart.
Solstices and Seasons
The solstices, astronomical events, mark seasonal transitions. Around June 21, the Northern Hemisphere’s summer solstice brings the longest daylight hours, while the Southern Hemisphere experiences its shortest day, the winter solstice. Near the summer solstice, the Sun’s noontime position shifts minimally, with its vertical rays striking the Tropic of Cancer (23.5° north of the equator). This results in longer, hotter days in the Northern Hemisphere.
Around December 21, the Northern Hemisphere tilts farthest from the Sun, marking the winter solstice, the shortest day of the year. The Sun appears lowest in the sky, with rays striking the Earth at a slanted angle, leading to less sunlight and warmth. Days are shorter, nights longer, and the season colder. Meanwhile, during the December solstice, the Sun’s vertical rays strike the Tropic of Capricorn (23.5° south of the equator), bringing longer, hotter days to the Southern Hemisphere.
In brief, the June solstice marks the summer solstice in the Northern Hemisphere and the winter solstice in the Southern Hemisphere. The December solstice marks the winter solstice in the Northern Hemisphere and the summer solstice in the Southern Hemisphere.
Twice a year, in March and September, an equinox divides Earth’s day almost equally, with about 12 hours of daylight and 12 hours of night. From March 21 to September 21, the Northern Hemisphere tilts toward the Sun, experiencing spring and summer, while the Southern Hemisphere tilts away, entering autumn and winter. The Equator receives the Sun’s rays at maximum intensity year-round, resulting in minimal variation between solstices. At the poles, the solstices mark when the Sun is at its highest or lowest point in the sky, representing the extremes of midnight sun and polar night. The midnight sun occurs around the summer solstice, when the Sun remains visible at midnight for weeks before and after the event. The polar night happens around the winter solstice, with the Sun staying below the horizon during the same period.
Cultural significance of Solstices
Some ancient cultures recognised only winter and summer, placing solstices in the middle of these seasons, hence the terms midwinter and midsummer. Since ancient times, solstices have inspired holidays and festivals. Midwinter celebrations often focus on prayer, seeking survival through the cold and dark, and fostering communal cooperation. In some cultures, these festivals mark the final gathering before the “famine months” of winter. In Japan, midwinter (toji) is observed with traditional yuzuyu hot citrus baths. These baths, filled with citrus fruits, serve both symbolic and practical purposes, offering prayers for the New Year while warming the body and soothing winter-chapped skin.
The most famous midwinter celebration is Saturnalia, ancient Rome’s most famous midwinter festival, which occurred in the weeks leading to the solstice. This lively carnival marked the changing seasons with feasts, gambling, the exchange of gifts, and the reversal of social roles. Masters sometimes served slaves, and a “King of Saturnalia” oversaw festivities, issuing playful commands like jumping into a river or wearing fancy costumes. Early Christians adopted Saturnalia’s timing for Advent and Christmas.
Midsummer marked peak agricultural fertility and the approach of the harvest season. For ancient cultures, successful crop growth, livestock management, and hunting were vital for survival. Midsummer festivals often celebrated nature’s abundance. Ancient European tribes celebrated midsummer with feasts and bonfires to ward off evil spirits. In Alpine and Germanic regions, these bonfires, known as Sonnwendfeuer, remain a cultural tradition. Many of these practices persist in Europe and countries with significant European, particularly Scandinavian, heritage, such as Canada and the US. Linked to fertility and abundance, midsummer is often associated with romance and marriage. This theme is famously captured in William Shakespeare’s comedic play A Midsummer Night’s Dream.
