A solstice is an astronomical event that occurs twice annually when the Sun reaches its most northerly or southerly excursion relative to the celestial equator on the celestial sphere. It marks a point where the Sun's apparent path in the sky reaches its northernmost or southernmost extreme before reversing direction.

When do the two annual solstices typically occur?

The two solstices occur annually around June 20-22 and December 20-22. These dates mark significant points in Earth's orbit relative to the Sun.

How are seasons often defined in relation to solstices and equinoxes?

In many countries, the seasons of the year are defined by reference to the solstices and the equinoxes. These astronomical events serve as markers for the transitions between seasons.

What is the etymological origin of the word solstice?

The word solstice originates from the Latin words 'sol,' meaning 'sun,' and 'sistere,' meaning 'to stand still.' This name reflects the apparent pause in the Sun's seasonal movement across the sky at these times.

Why is the Sun's declination described as appearing to 'stand still' during a solstice?

At the moment of solstice, the Sun's declination, which is its angular distance north or south of the celestial equator, appears to stop its seasonal movement and then reverse direction. This apparent pause gives rise to the term 'solstice.'

What is an older English term for solstice, and what does it mean?

An older English term for solstice is 'sunstead,' which is a calque (a word or phrase translated literally) from Old English (sunstede). It carries the same meaning as solstice, referring to the Sun's position.

How is the solstice defined from the perspective of an observer at the North Pole?

For an observer at the North Pole, the Sun reaches its highest position in the sky once a year in June, marking the June solstice day. This event signifies the peak of the Sun's apparent northward journey.

What is the Latin scientific term for solstice used in the 1st century BC, and what does it mean?

The Latin scientific term used in the 1st century BC was 'solstitium.' It is composed of 'sol' (sun) and '-stitium' (stoppage), meaning 'sun's stoppage,' referring to the apparent halt in the Sun's declination.

What is the 'obliquity of the ecliptic'?

The obliquity of the ecliptic is the angle of Earth's axial tilt relative to its orbital plane, which is approximately 23.44 degrees. This tilt is the primary reason for the changing seasons.

Where is the subsolar point located during the June solstice?

During the June solstice, the subsolar point, which is the point on Earth where the Sun is directly overhead, is at its northernmost position, located at latitude 23.44 degrees north. This latitude is known as the Tropic of Cancer.

Where is the subsolar point located during the December solstice?

At the December solstice, the subsolar point is at its southernmost position, located at latitude 23.44 degrees south. This latitude is known as the Tropic of Capricorn.

What phenomenon occurs at the Arctic Circle during the June solstice?

During the June solstice, locations on the Arctic Circle (latitude 66.56 degrees north) experience the Sun just on the horizon at midnight. All areas north of the Arctic Circle witness the Sun above the horizon for the entire 24-hour day, an event known as the midnight sun or polar day.

What phenomenon occurs at the Antarctic Circle during the June solstice?

During the June solstice, locations on the Antarctic Circle (latitude 66.56 degrees south) see the Sun just on the horizon at midday. All areas south of the Antarctic Circle experience the polar night, meaning the Sun does not rise above the horizon at all during that day.

How do the effects of the December solstice on polar regions differ from the June solstice?

During the December solstice, the effects on the polar regions are reversed. The midnight sun occurs north of the Arctic Circle, while the polar night occurs south of the Antarctic Circle.

Why are the warmest and coldest periods of the year in temperate regions offset from the solstices?

The warmest and coldest periods in temperate regions are typically offset by about a month from the solstices due to Earth's thermal inertia. This means the ground and oceans take time to heat up or cool down in response to the changing solar radiation.

What was the ancient Greek term for solstice, and what did it mean?

The ancient Greeks used the term 'heliostasio' (ἡλιοστάσιο) for solstice, which literally translates to 'stand of the Sun.' This term reflects the apparent cessation of the Sun's north-south movement in the sky.

How did the term 'ecliptic' originate in relation to the Sun's path?

The term 'ecliptic' originated from the Greek word 'ekleipsis' (ἔκλειψις), meaning 'eclipse.' It became a synonym for the Sun's path because the Moon, when crossing this path, can cause solar or lunar eclipses.

What are the most common English names for the two solstices, and what is a potential ambiguity?

The most common names are the summer solstice and winter solstice. The ambiguity arises because the Northern Hemisphere's summer corresponds to the Southern Hemisphere's winter, and vice versa.

What are the less ambiguous names for the solstices that refer to the months they occur in?

The June solstice and the December solstice are less ambiguous names because they directly refer to the months in which these events take place annually, regardless of the hemisphere.

What do the terms 'northern solstice' and 'southern solstice' indicate?

These terms indicate the hemisphere where the Sun is directly overhead at noon. The northern solstice occurs when the Sun is over the Tropic of Cancer in the Northern Hemisphere, and the southern solstice occurs when it's over the Tropic of Capricorn in the Southern Hemisphere.

What are the astrological names for the solstices, and how have they shifted?

The astrological names are the 'first point of Cancer' and the 'first point of Capricorn,' referring to the zodiac signs the Sun appeared to enter. Due to the precession of the equinoxes, the Sun is now found in the constellations of Taurus (in June) and Sagittarius (in December) at the solstices, rather than Cancer and Capricorn.

In the traditional East Asian calendar system, what is Xiazhi?

Xiazhi (or Geshi in Japanese) is the 10th solar term in the traditional East Asian calendars. It marks the summer solstice and signifies the 'summer's extreme.'

What does Dongzhi signify in the East Asian calendar system?

Dongzhi (or Tōji in Japanese) is the 22nd solar term and marks the winter solstice. Its name literally means 'winter's extreme,' indicating the peak of winter.

How do the East Asian solar terms Xiazhi and Dongzhi relate to the seasons?

In East Asian calendars, the solstices (Xiazhi and Dongzhi) and equinoxes mark the middle points of the seasons, rather than the beginnings. The character 'zhi' (至) in their names signifies 'extreme' or 'arrival,' denoting the peak of summer or winter.

What is the significance of the solstice in many cultural celebrations?

Solstices, along with equinoxes, are often connected to seasonal festivals and celebrations across various cultures. Some cultures consider them the start of seasons, while others view them as the midpoint.

What is the traditional timing of Midsummer celebrations in relation to the June solstice?

In England and other Northern Hemisphere locations, the period around the northern solstice is known as midsummer. Midsummer's Day is traditionally celebrated around June 24th, which is about three days after the solstice itself.

How is the winter solstice linked to the timing of Christmas?

Christmas is celebrated on December 25th, which is shortly after the winter solstice. This timing is significant as it marks the day when the Sun begins its return journey, increasing daylight in the Northern Hemisphere.

What were the traditional British and Irish 'quarter days'?

The traditional British and Irish quarter days, which were significant rent and meeting days, were often aligned with the solstices and equinoxes. These days marked important points in the agricultural and social calendar.

Name some contemporary holidays celebrated around the southern (winter) solstice.

Holidays celebrated around the southern solstice include Christmas, Yalda Night, Saturnalia, Karachun, Hanukkah, Kwanzaa, and Yule.

What is the Dongzhi Festival, and when is it celebrated?

The Dongzhi Festival is a traditional celebration in East Asian cultures observed on the winter solstice. It marks the 'winter's extreme' and is a time for family gatherings and specific foods.

What is celebrated around the northern (summer) solstice in many Christian cultures?

In many Christian cultures, the feast of St. John the Baptist is celebrated from June 23rd to 24th, often referred to as St. John's Eve, which occurs around the summer solstice.

What do modern Pagans observe around the summer solstice?

Modern Pagans observe Midsummer around the summer solstice, which is known as Litha among Wiccans. This celebration acknowledges the longest day of the year.

What Hindu calendar terms mark the start of Uttarayana and Dakshinayana?

In the Hindu calendar, Makara Sankranti marks the start of Uttarayana (the Sun's northward journey), and Karka Sankranti marks the start of Dakshinayana (the Sun's southward journey).

Why is determining the exact moment of the solstice more difficult than determining the equinox?

Determining the exact moment of the solstice is more difficult because the changes in the Sun's declination become very small as it approaches its maximum or minimum point. The Sun's apparent motion in declination slows down significantly, making it hard to detect precise changes with simple instruments.

What limitations do traditional tools like gnomons and astrolabes have in determining the precise solstice?

Traditional tools like gnomons and astrolabes have limitations because the subtle changes in the Sun's declination and the effects of atmospheric refraction near the horizon make it difficult to pinpoint the exact solstice day based on simple observations within a few days of the event.

How do astronomical almanacs define the moment of solstice?

Astronomical almanacs define the solstices as the precise moments when the Sun passes through the solstitial colure, which corresponds to the apparent geocentric celestial longitude of the Sun being exactly 90 degrees (for the June solstice) or 270 degrees (for the December solstice).

What causes the dates of the solstices to shift slightly each year?

The dates of the solstices shift slightly each year because Earth's orbital period is slightly longer than a standard calendar year of 365 days. This difference causes the solstices to occur progressively later until a leap day realigns the calendar with the orbit.

How has the northern solstice's position shifted relative to constellations over millennia?

The northern solstice has shifted significantly over millennia due to the precession of the equinoxes. It moved from Leo into Cancer around 1458 BC, then into Gemini around 10 BC, into Taurus in 1989, and is expected to move into Aries around 4609 AD.

What is the Greek term for the ecliptic, and why is it significant?

The Greek term for the ecliptic is 'heliakos kuklos' (heliacal circle), meaning 'of the sun.' It is significant because it represents the apparent path of the Sun across the celestial sphere and is central to understanding celestial movements and the zodiac.

What is the relationship between the June solstice and the Tropic of Cancer?

The June solstice occurs when the Sun is directly over the Tropic of Cancer, located at 23.44 degrees north latitude. This marks the northernmost point of the Sun's apparent path.

What is the relationship between the December solstice and the Tropic of Capricorn?

The December solstice occurs when the Sun is directly over the Tropic of Capricorn, located at 23.44 degrees south latitude. This marks the southernmost point of the Sun's apparent path.

What does the term 'solstice' imply about the Sun's apparent motion?

The term 'solstice,' derived from Latin 'sol' (sun) and 'sistere' (to stand still), implies that the Sun's apparent motion in declination (north-south position) pauses and reverses direction at this time.

How does the length of daylight change around the summer solstice in non-equatorial regions?

In regions not too close to the equator, the summer solstice is the day with the longest period of daylight. Conversely, the winter solstice is the day with the shortest period of daylight.

What is the significance of the solstices in the context of Earth's axial tilt?

The solstices represent the two points in Earth's orbit where the inclination of its rotational axis relative to the Sun has its maximum effect, leading to the longest and shortest days of the year in each hemisphere.

What is the meaning of 'Xiazhi' and 'Dongzhi' in East Asian cultures?

Xiazhi signifies the summer solstice and means 'summer's extreme,' while Dongzhi signifies the winter solstice and means 'winter's extreme.' These terms highlight the peak of summer heat and winter cold, respectively.

How does the precession of the equinoxes affect the constellations associated with the solstices?

Due to the precession of the equinoxes, the constellations that the Sun appears in during the solstices gradually shift over long periods. For example, the June solstice, once associated with Cancer, is now in Taurus due to this slow wobble in Earth's axis.

What is the approximate angle of Earth's axial tilt, also known as the obliquity of the ecliptic?

The Earth's axial tilt, or obliquity of the ecliptic, is approximately 23.44 degrees. This tilt is fundamental to the cycle of seasons.

What is the difference between the astronomical definition of solstice and its common usage as a 'day'?

Astronomically, the solstice is a precise moment in time. However, it is often referred to more broadly as the 'day' on which this moment occurs, and this day is closely associated with the start or midpoint of seasons.

What are the two main solstices referred to by the months they occur in?

The two main solstices are the June solstice and the December solstice, named for the months in which they occur annually.

Solstice Wiki: Celestial Crossroads: Understanding the Solstice

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What is a Solstice?

Astronomical Definition

A solstice marks the precise moment when the Sun attains its greatest distance north or south from the celestial equator. This occurs twice annually, around June 20-22 and December 20-22. These events are fundamental markers for defining the seasons in many global cultures.

The Sun's Apparent Standstill

The term 'solstice' derives from the Latin 'sol' (sun) and 'sistere' (to stand still). This nomenclature aptly describes the phenomenon where the Sun's apparent declination, its angular distance north or south of the celestial equator, reaches its extreme limits. At these points, the Sun's daily path appears to momentarily cease its seasonal progression before reversing direction.

Annual Occurrence

The two primary solstices are the June solstice, often associated with the summer season in the Northern Hemisphere, and the December solstice, linked to winter in the Northern Hemisphere. These dates correspond to the longest and shortest periods of daylight, respectively, for locations not situated near the equator.

Etymological Roots

Greek and Latin Origins

The term 'solstice' entered the English lexicon during the Middle English period, originating from Latin. It is a composite of 'sol' (sun) and 'sistere' (to stand still), reflecting the perceived cessation of the Sun's north-south movement in the sky.

Germanic Cognates

An older English term, 'sunstede' (from Old English: *sunstede*), shares roots with similar terms in other Germanic languages, such as Old Norse *sólstaðr* and Middle High German *sunnenstat*. These terms similarly denote the Sun's stationary position.

Frames of Reference

Earth's Axial Tilt

The solstices are a direct consequence of Earth's axial tilt, approximately 23.44 degrees relative to its orbital plane. As Earth orbits the Sun, this tilt causes different hemispheres to receive more direct sunlight at different times of the year.

Subsolar Point

At the June solstice, the subsolar point—the location on Earth where the Sun is directly overhead—reaches its northernmost extent at the Tropic of Cancer (23.44° N). Conversely, at the December solstice, it reaches its southernmost extent at the Tropic of Capricorn (23.44° S).

Polar Phenomena

Beyond the tropics, the solstices dictate extreme daylight conditions. North of the Arctic Circle, the June solstice marks the 'midnight sun' (24-hour daylight), while south of the Antarctic Circle, it signifies 24-hour polar night. The December solstice reverses these conditions for the respective hemispheres.

Seasonal Lag

While solstices mark the astronomical extremes of daylight, the warmest and coldest periods of the year in temperate regions typically lag by about a month due to Earth's thermal inertia—the time it takes for the atmosphere and oceans to absorb and release heat.

Solstices and Seasons

The Cycle of Seasons

The solstices, along with the equinoxes, serve as critical reference points for the progression of Earth's seasons. They delineate the periods when one hemisphere is maximally inclined towards the Sun, leading to longer days and summer, and minimally inclined, resulting in shorter days and winter.

Defining Seasonal Boundaries

In many cultures, solstices are considered either the beginning or the midpoint of seasons. For instance, in England, the period around the June solstice is traditionally recognized as 'midsummer', highlighting its role as a seasonal marker.

Precise Timing

The exact date and time of solstices vary annually due to the Earth's orbital mechanics and the Gregorian calendar's leap year system. Astronomical almanacs precisely define these moments based on the Sun's celestial longitude reaching 90° (June) or 270° (December).

Equinoxes and Solstices (UT)
Year	June Solstice (Day)	June Solstice (Time)	December Solstice (Day)	December Solstice (Time)
2020	20	21:43	21	10:03
2021	21	03:32	21	15:59
2022	21	09:14	21	21:48
2023	21	14:58	22	03:28
2024	20	20:51	21	09:20
2025	21	02:42	21	15:03
2026	21	08:25	21	20:50
2027	21	14:11	22	02:43
2028	20	20:02	21	08:20
2029	21	01:48	21	14:14
2030	21	07:31	22	20:09

Cultural Significance

Ancient Observances

Across ancient civilizations, solstices were pivotal events, often marking agricultural cycles, religious festivals, and astronomical alignments. Structures like Stonehenge demonstrate sophisticated observation of these celestial occurrences.

Celebrations and Traditions

Numerous cultures worldwide observe solstices through diverse traditions. These range from midsummer festivals celebrating the longest day, such as St. John's Day or Litha in Pagan traditions, to winter solstice observances like Dongzhi (East Asia), Yule (Northern Europe), and Saturnalia (Ancient Rome), often marking renewal and the return of longer days.

Global Perspectives

In the Southern Hemisphere, the timing of seasons is reversed. The June solstice signifies winter, while the December solstice marks summer. Indigenous cultures, such as the Mapuche in South America, celebrate their New Year, We Tripantu, around the June solstice, acknowledging the Sun's return.

Hindu Calendar

The Hindu calendar recognizes two significant solar movements related to solstices: Uttarayana, beginning around the winter solstice (January), signifying the Sun's northward journey, and Dakshinayana, beginning around the summer solstice (July), marking its southward movement.

Determining the Solstice

Precision Challenges

Precisely determining the solstice moment through direct observation is challenging. The Sun's change in declination slows significantly near the extreme points, making detection difficult with traditional instruments like gnomons or astrolabes due to atmospheric refraction and the Sun's apparent angular size.

Astronomical Calculation

Modern astronomical almanacs define the solstice as the instant the Sun's geocentric celestial longitude equals 90° (June) or 270° (December). This calculation accounts for orbital variations and provides the precise moment, which is then adjusted for specific time zones.

Solstices and Constellations

Precession of the Equinoxes

Due to the slow wobble of Earth's axis, known as the precession of the equinoxes, the constellations through which the Sun appears to pass at the solstices gradually shift over millennia. Currently, the June solstice occurs when the Sun is in Taurus, and the December solstice aligns with Sagittarius.

Future Alignments

Future precession will cause these alignments to change. For instance, the June solstice is projected to move from Taurus into Gemini in the coming centuries, and the December solstice will eventually shift from Sagittarius into Ophiuchus.

Further Study

Related Astronomical Concepts

Understanding solstices is enhanced by exploring related astronomical phenomena such as the analemma, Earth's axial tilt, the concept of celestial spheres, and the difference between solar and sidereal time. These concepts provide a comprehensive framework for celestial mechanics.

Timekeeping and Calendars

The historical and ongoing importance of solstices in timekeeping and calendar development is profound. Studying ancient calendars, the development of time standards like UTC, and the mechanics of leap years offers insight into humanity's quest to measure and organize time.

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References

Ãquinoxe de printemps entre 1583 et 2999

Ãquinoxe dâautomne de 1583 Ã 2999

Solstice dâhiver

Strabo II.5.2., "aplaneis asteres kata parallÄlÅn pherontai kuklÅn", "the fixed stars are borne in parallel circles"

Strabo II.5.2, "ho di'autÄs (gÄ) aksÅn kai tou ouranou mesou tetagmenos", "the axis through it (the Earth) extending through the middle of the sky"

A full list of references for this article are available at the Solstice Wikipedia page

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This content has been generated by an AI, drawing upon established astronomical data and historical context. While efforts have been made to ensure accuracy and adherence to academic standards, it is intended for educational purposes. Users are encouraged to consult primary sources and peer-reviewed literature for definitive research.

This is not a substitute for professional astronomical consultation. Information provided herein should not be the sole basis for critical decisions. Always refer to official astronomical data, academic journals, and expert analysis.

The creators of this platform are not liable for any inaccuracies, omissions, or consequences arising from the use of this information.

Celestial Crossroads

💡 Dive in with Flashcard Learning! 💡

What is a Solstice? ☀️

🔭 Astronomical Definition

⏳ The Sun's Apparent Standstill

🗓️ Annual Occurrence

Etymological Roots 📜

🇬🇷 Greek and Latin Origins

🇬🇧 Germanic Cognates

Frames of Reference 🌌

🌍 Earth's Axial Tilt

📍 Subsolar Point

☀️ Polar Phenomena

🌡️ Seasonal Lag

Solstices and Seasons 🍂

🔄 The Cycle of Seasons

📊 Defining Seasonal Boundaries

📅 Precise Timing

Cultural Significance ✨

🏛️ Ancient Observances

🎉 Celebrations and Traditions

🌏 Global Perspectives

🕉️ Hindu Calendar

Determining the Solstice 🔬

📐 Precision Challenges

📈 Astronomical Calculation

Solstices and Constellations 🌠

💫 Precession of the Equinoxes

🔭 Future Alignments

Further Study 📚

🔗 Related Astronomical Concepts

🕰️ Timekeeping and Calendars

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References

📜 References

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🎓 Important Notice

Dive in with Flashcard Learning!

What is a Solstice?

Astronomical Definition

The Sun's Apparent Standstill

Annual Occurrence

Etymological Roots

Greek and Latin Origins

Germanic Cognates

Frames of Reference

Earth's Axial Tilt

Subsolar Point

Polar Phenomena

Seasonal Lag

Solstices and Seasons

The Cycle of Seasons

Defining Seasonal Boundaries

Precise Timing

Cultural Significance

Ancient Observances

Celebrations and Traditions

Global Perspectives

Hindu Calendar

Determining the Solstice

Precision Challenges

Astronomical Calculation

Solstices and Constellations

Precession of the Equinoxes

Future Alignments

Further Study

Related Astronomical Concepts

Timekeeping and Calendars

Teacher's Corner

True or False?

Test Your Knowledge!

Gamer's Corner

Discover other topics to study!

References

Feedback & Support

Academic Disclaimer

Important Notice