• A solstice is an event in which a planet’s poles are most extremely inclined toward or away from the star it orbits. 
     
    On our planet, solstices are defined by solar declination—the latitude of the Earth where the sun is directly overhead at noon. On Earth, solstices are twice-yearly phenomena in which solar declination reaches the Tropic of Cancer in the north and the Tropic of Capricorn in the south. During the June solstice (marked between June 20 and June 22), solar declination is about 23.5°N (the Tropic of Cancer). During the December solstice (marked between December 20 and December 23), solar declination is about 23.5°S (the Tropic of Capricorn).
     
    Solstices and shifting solar declinations are a result of Earth’s 23.5° axial tilt as it orbits the sun. Throughout the year, this means that either the Northern or Southern Hemisphere is tilted toward the sun and receives the maximum intensity of the sun’s rays. (The only times of the year when the intensity of the sun’s rays is not unequal are the appropriately named equinoxes. During an equinox, solar declination is 0°—the Equator—and both the Northern and Southern Hemisphere receive equal sunlight.)
     
    Sometimes, solstices are nicknamed the “summer solstice” and the “winter solstice,” although these have different dates in the Northern and Southern Hemispheres. The summer solstice is the longest day of the year, meaning it experiences the maximum intensity of the sun’s rays and has the most hours of sunlight. The winter solstice is the shortest day of the year and has the fewest hours of daylight.
     
    The June solstice is the summer solstice in the Northern Hemisphere and the winter solstice in the Southern Hemisphere. The December solstice is the winter solstice in the Northern Hemisphere and the summer solstice in the Southern.
     
    The Science of Solstices
     
    Earth’s latitudes experience the solstices in different ways. At the poles, a solstice is the peak of a radical exposure to daylight, while at the Equator, the solstices are barely marked at all.
     
    Equatorial Regions
    The Equator, at 0° latitude, receives a maximum intensity of the sun’s rays all year.
     
    As a result, areas near Earth’s Equator experience relatively constant sunlight and little solstice variation.
     
    Mid-latitudes
    Earth’s solstices are largely marked by the transition of the subsolar point across the tropics. The subsolar point describes the latitude where the sun’s rays hit the Earth exactly perpendicular to the Earth’s surface. It is where the sun appears directly overhead at noon.
     
    The subsolar point appears at the Equator twice a year (during the equinoxes), and migrates north and south across the tropics during the rest of the year. The solstices mark when the subsolar point reaches its northernmost and southernmost latitudes.
     
    The sun’s vertical rays strike the Tropic of Cancer, 23.5° north of the Equator, during the June solstice. The subsolar point then begins its migration south, and vertical rays strike the Tropic of Capricorn, 23.5° south of the Equator, during the December solstice. The subsolar point will cross every latitude between these extremes twice every year.
     
    Polar Regions
    The subsolar point never reaches Arctic and Antarctic regions. At the North Pole and South Pole, the solstices mark the time when the sun is highest or lowest in the sky. In this way, solstices are the extreme examples of “midnight sun” and “polar night.”
     
    Midnight sun” describes the phenomenon surrounding the summer solstice, when the sun remains visible at midnight in the weeks leading up to and following the event. The “polar night” surrounds the winter solstice, when the sun remains below the horizon during the weeks leading up to and following the event.
     
    Extraterrestrial Solstices
    Every planet in our solar system experiences solstices. The timing and extent of solstices are largely determined by the planet’s axial tilt, orbital eccentricity, and distance from the sun. 
     
    Venus, the planet closest to Earth, has a very small axial tilt, just 3°. Venus experiences very little seasonal variation, and its solstices are separated by about three months.
     
    Mars, our other close neighbor, has an axial tilt similar to Earth (24°). However, Mars has a significantly greater orbital eccentricity, meaning it orbits the sun in a more elliptical shape than Earth. As a result of Mars’ larger orbital eccentricity and axial tilt, the Red Planet experiences extreme seasonal variations and its solstices are about 11 months apart.
     
    The Culture of the Solstices
     
    Solstices now mark the beginning of winter and summer, but because some ancient cultures only recognized these two seasons (there was no autumn or spring), the solstices occurred in the middle of the season. Solstices are known as midwinter and midsummer for this reason. 
     
    Since ancient times, many cultures have marked the solstices with holidays and festivals.
     
    Midwinter
    Followers of many ancient traditions honored the winter solstice, which signaled the cold, winter season. Winter weather put ancient cultures at their most vulnerable; both food and shelter were limited. Many festivities emphasize light, recognizing the winter solstice as the shortest, darkest day of the year.
     
    In many cultures, holidays surrounding midwinter are more prayerful than celebratory—they include cultures praying for survival through the dark and cold, as well as celebrating the spirit of cooperation that helps communities survive difficult times. In other places, midwinter celebrations are the last festivals before the long “famine months” of winter.
     
    Monuments to midwinter holidays can be seen at Stonehenge, in Great Britain, and the so-called Intihuatana Stone (the so-called “hitching post of the sun”) at the Incan ruin of Machu Picchu in Peru. At these sites, people gathered to celebrate and pray for their survival through the rest of winter.
     
    In Japan, midwinter (toji) is marked by traditional yuzuyu hot citrus baths. Yuzuyu are practical as well as symbolic. The hot tubs filled with dozens of citrus fruit are intended to focus prayers for the new year, as well as warm the body and soothe skin chapped by winter winds.
     
    The Sha’lak’o midwinter dance is a custom among the Zuni peoples of the Southwestern United States. During the Sha’lak’o, dancers representing the Zuni fire god and rain god, help the communities bid farewell to the old year and seek blessings in the new.
     
    Perhaps the most famous midwinter celebration is the Saturnalia of Ancient Rome. Saturnalia was celebrated the weeks leading up to the actual solstice. Saturnalia was a wild carnival, as well as a time to mark the passing of the seasons. During Saturnalia festivities, Romans enjoyed banquets, gambling, jokes, gifts, and a tradition of usurping strict social structures. At Saturnalia feasts, masters may have served their slaves, and a “King of Saturnalia” could be appointed to manage merrymaking—decreeing that guests must jump in a river or wear outrageous costumes, for instance.
     
    Early Christians adopted the timing of Saturnalia for two of their most important seasons, Advent and Christmas. Pagans and neopagans, followers of early European religious traditions, still celebrate the winter solstice as a holiday called Yule. 
     
    Midsummer
    Midsummer heralded the height of agricultural fertility and the slow onset of the harvest season. The growing and harvesting of crops, management of domestic animals, and the ability to hunt wild game were all crucial to the survival of ancient cultures. Midsummer festivals are often celebrations of nature’s bounty.
     
    Ancient European tribes celebrated midsummer with feasts and bonfires, intended to drive away evil spirits. In Alpine and Germanic regions, summer solstice bonfires are so ingrained in the cultures they have their own name: Sonnwendfeuer. Many of these traditions still survive in Europe and countries that have large populations with European (especially Scandinavian) heritage, such as Canada and the United States. 
     
    In Finland, midsummer (Juhannus) celebrations include bonfires, saunas, and barbeques. Due to Finland’s proximity to the Arctic, the summer solstice itself can have very little darkness. This makes midsummer in Scandinavia an ideal time for weeklong outdoor music festivals and family vacations.
     
    In Ancient Egypt, the summer solstice signaled the beginning of the new year. Sirius, the brightest star in the night sky, appeared soon after the summer solstice. Egyptian astronomers associated the annual appearance of Sirius with the seasonal flooding of the Nile River, which the civilization depended on for agriculture.
     
    Due to its association with fertility and abundance, midsummer is often associated with romance and marriage. One of the most famous expressions of this romantic sentiment is the comic play “A Midsummer Night’s Dream,” by the English writer William Shakespeare. In the play, fairies enchant two couples in a magical forest—and haphazardly get enchanted themselves. The play’s many role-reversals and changes in appearance are thematically tied to the solstice.
    solstice
    The December solstice marks the beginning of summer in the Southern Hemisphere and winter in the Northern.
    Analemma
    An analemma is a narrow, figure-8 shaped pattern made by tracking the position of the sun over the course of a year from a fixed time and place. The top and bottom of an analemma mark the solstices.
    Shifting Solstices
    In any year which is not a leap year, solstices occur about 5 hours and 48 minutes later from one year to the next. This is why the seasons would drift later and later in the year if it was not for an additional day being inserted into every fourth year on February 29.
    Midwinter in Antarctica
    The June solstice is easily the biggest celebration in Antarctica, marking the day when the sun may begin to appear on the horizon after months of “polar night.” The few scientists who overwinter at the bases in Antarctica celebrate with feasts, shared presents … and an icy polar plunge!
    St. John's Day
    One of the most prevalent solstice celebrations is St. John’s Day, marked in the Christian calendar on the June solstice. St. John’s Day, honored as the birthday of St. John the Baptist, is celebrated with feasts and parties in regions with large Christian populations. Some of the largest festivities of St. John’s Day take place as Festa Junina in Brazil.
  • Term Part of Speech Definition Encyclopedic Entry
    abundance Noun

    large amount.

    Advent Noun

    in the Christian calendar, the season beginning four Sundays before Christmas.

    agricultural Adjective

    having to do with farmers, farming, or their way of life.

    Alpine Adjective

    having to do with the Alps mountain range.

    ancient Adjective

    very old.

    ancient Rome Noun

    civilization founded on the Mediterranean Sea, lasting from the 8th century BCE to about 476 CE.

    Antarctic Noun

    region at Earth's extreme south, encompassed by the Antarctic Circle.

    Arctic Noun

    region at Earth's extreme north, encompassed by the Arctic Circle.

    Encyclopedic Entry: Arctic
    associate Verb

    to connect.

    astronomer Noun

    person who studies space and the universe beyond Earth's atmosphere.

    axial tilt Noun

    angle between an object's axis of rotation and its orbital axis, perpendicular to the orbital plane. Earth's axial tilt is about 23.5 degrees.

    banquet Noun

    large feast, or to eat at a large feasting party.

    bonfire Noun

    large outdoor fire.

    bounty Noun

    large amount.

    carnival Noun

    traveling show with games, performances, and food.

    celebrate Verb

    to observe or mark an important event with public and private ceremonies or festivities.

    chap Verb

    to crack, roughen, and redden the skin.

    Christian Noun

    people and culture focused on the teachings of Jesus and his followers.

    Christmas Noun

    Christian holiday celebrating the birth of Jesus of Nazareth.

    citrus Noun

    type of fruit tree, including lemon and orange.

    civilization Noun

    complex way of life that developed as humans began to develop urban settlements.

    Encyclopedic Entry: civilization
    crop Noun

    agricultural produce.

    Encyclopedic Entry: crop
    crucial Adjective

    very important.

    culture Noun

    learned behavior of people, including their languages, belief systems, social structures, institutions, and material goods.

    domestic animal Noun

    animal that has been tamed for work or to be a pet.

    Earth Noun

    our planet, the third from the Sun. The Earth is the only place in the known universe that supports life.

    Encyclopedic Entry: Earth
    enchant Verb

    to cast a spell on, or subject to magical influence.

    equinox Noun

    period in which daylight and darkness are nearly equal. There are two equinoxes a year.

    Encyclopedic Entry: equinox
    famine Noun

    an extreme shortage of food in one area during a long period of time.

    feast Verb

    to eat large amounts of food, usually to celebrate or honor something.

    fertility Noun

    capacity of soil to sustain plant growth; or the average number of children born to women in a given population.

    Encyclopedic Entry: fertility
    forest Noun

    ecosystem filled with trees and underbrush.

    game Noun

    wild animals hunted for food.

    haphazard Adjective

    having to do with randomness, chance, and lack of planning.

    harvest Noun

    the gathering and collection of crops, including both plants and animals.

    heritage Noun

    cultural or family background.

    holiday Noun

    period of celebration or honor.

    Inca Noun

    people and culture native to the Andes Mountains and Pacific coast of South America.

    incline Noun

    slant, slope, or dip.

    ingrain Verb

    to instill, or impress deeply in the mind and consciousness.

    latitude Noun

    distance north or south of the Equator, measured in degrees.

    Encyclopedic Entry: latitude
    magic Noun

    control of natural or spiritual forces.

    midnight sun Noun

    sunlight visible all night at certain times of the year in Arctic and Antarctic regions.

    midsummer Noun

    period around the summer solstice, the longest day of the year.

    midwinter Noun

    (Dec. 22 in the Northern Hemisphere, June 22 in the Southern Hemisphere) winter solstice.

    monument Noun

    large structure representing an event, idea, or person.

    Northern Hemisphere Noun

    half of the Earth between the North Pole and the Equator.

    North Pole Noun

    fixed point that, along with the South Pole, forms the axis on which the Earth spins.

    Encyclopedic Entry: North Pole
    orbit Verb

    to move in a circular pattern around a more massive object.

    Encyclopedic Entry: orbit
    orbital eccentricity Noun

    factor by which an astronomical object varies from a perfect circle in its orbit around another body.

    pagan Adjective

    following the religious traditions of ancient Europe, including polytheism and nature worship.

    perpendicular Noun

    at a right angle to something.

    phenomena Plural Noun

    (singular: phenomenon) any observable occurrence or feature.

    planet Noun

    large, spherical celestial body that regularly rotates around a star.

    Encyclopedic Entry: planet
    polar night Noun

    lack of sunlight at all hours at certain times of the year in Arctic and Antarctic regions.

    pole Noun

    extreme north or south point of the Earth's axis.

    proximity Noun

    nearness.

    Saturnalia Noun

    Roman festival around the winter solstice.

    sauna Noun

    room in which steam causes visitors to sweat.

    Scandinavia Noun

    region and name for some countries in Northern Europe: Iceland, Norway, Sweden, Finland, and Denmark.

    season Noun

    period of the year distinguished by special climatic conditions.

    Encyclopedic Entry: season
    seasonal flooding Noun

    overflowing of a body of water from its banks, usually predicted by yearly rains or storms.

    signal Verb

    to communicate using signs.

    Sirius Noun

    brightest star in Earth's sky, in the constellation Canis Major. Also called the Dog Star.

    slave Noun

    person who is owned by another person or group of people.

    solar declination Noun

    angle between the rays of the sun and the plane of the Equator.

    solstice Noun

    astronomical event that occurs twice a year, when the sun appears directly overhead to observers at the Tropic of Cancer or the Tropic of Capricorn.

    Encyclopedic Entry: solstice
    Southern Hemisphere Noun

    half of the Earth between the South Pole and the Equator.

    South Pole Noun

    fixed point that, along with the North Pole, forms the axis on which the Earth spins.

    Encyclopedic Entry: South Pole
    star Noun

    large ball of gas and plasma that radiates energy through nuclear fusion, such as the sun.

    Stonehenge Noun

    prehistoric monument in Salisbury Plain, England.

    subsolar point Noun

    area of a planet where the sun is perceived to be direcly overhead.

    summer Noun

    time of year when part of the Earth receives the most daylight: The months of June, July, and August in the Northern Hemisphere and the months of December, January, and February in the Southern Hemisphere.

    summer solstice Noun

    day of the year with the most hours of sunlight, June 20 or 21 in the Northern Hemisphere and December 21 or 22 in the Southern Hemisphere.

    sun Noun

    star at the center of our solar system.

    symbolic Adjective

    serving as a representation of something.

    tradition Noun

    beliefs, customs, and cultural characteristics handed down from one generation to the next.

    tribe Noun

    community made of one or several family groups sharing a common culture.

    Tropic of Cancer Noun

    line of latitude 23.5 degrees north of the Equator.

    Tropic of Capricorn Noun

    line of latitude 23.5 degrees south of the Equator.

    tropics Plural Noun

    region generally located between the Tropic of Cancer (23 1/2 degrees north of the Equator) and the Tropic of Capricorn (23 1/2 degrees south of the Equator).

    Encyclopedic Entry: tropics
    usurp Verb

    to seize without authority, or turn over an established order.

    vertical Noun

    up-down direction, or at a right angle to Earth and the horizon.

    vulnerable Adjective

    capable of being hurt.

    winter Noun

    time of year when part of the Earth receives the least daylight: December, January, and February in the Northern Hemisphere and June, July, and August in the Southern Hemisphere.

    winter solstice Noun

    (December 22 in the Northern Hemisphere, June 22 in the Southern Hemisphere) longest night of the year and the beginning of winter.