Summer Begins at Solstice Friday Night

   

This diagram shows the position of the Earth, in relation to the Sun, at the time of the Summer Solstice, as well as the Winter Solstice and the Spring and Autumnal Equinoxes of the year.

[Graphic Source: ©1999, Eric G. Canali, former Floor Operations Manager of the original Buhl Planetarium and Institute of Popular Science / Buhl Science Center (America's 5th major planetarium & Pittsburgh's science and technology museum from 1939 to 1991) and Founder of the South Hills Backyard Astronomers amateur astronomy club. Permission granted for non-profit use only, with credit to author.]

By Glenn A. Walsh

Reporting for SpaceWatchtower

Friday night, Summer begins in the Northern Hemisphere of Earth, while at the same time, Winter begins in the Southern Hemisphere.

For A.D. 2025, the season of Summer begins at Earth's Northern Hemisphere's Summer Solstice (and the season of Winter begins at the Southern Hemisphere's Winter Solstice) at the moment of the June Solstice: Friday Evening, 2025 June 20 at 10:42 p.m. Eastern Daylight Saving Time (EDT) / June 21, 2:42 Coordinated Universal Time [UTC – International time used by scientists; previously referred to as Greenwich Mean Time (GMT) or Greenwich Civil Time (GCT)]. Summer will continue in the Northern Hemisphere (and Winter will continue in the Southern Hemisphere) until the Autumnal Equinox when the season of Autumn / Fall commences in the Northern Hemisphere (and Spring begins in the Southern Hemisphere): Monday Afternoon, 2025 September 22 at 2:19 p.m. EDT / 18:19 UTC.

In Meteorology (Weather Science), the convention is to start a season on the first day of a calendar month. So, Meteorological Summer runs from June 1 to August 31.

In Etymology, the word Solstice comes from the Latin terms Sol (Sun) and Sistere (to stand still). In ancient times, Astronomers / Astrologers / Priests recognized that on one day of the year (in the Northern Hemisphere, on or near the day we now call June 21), the Sun would appear to stand-still (regarding the Sun's apparent move higher or lower in the sky, from day-to-day) as Sol reaches its highest point in the sky for the entire year. The motion of the Sun's apparent path in the sky (daily motion higher or lower in the sky, what is known astronomically, today, as the Sun's Declination) would cease on this day, before appearing to reverse direction.

Although the Summer months in the Northern Hemisphere are known for the year's warmest weather, the Earth is actually at the point in its orbit farthest from the Sun (astronomically known as the point of Aphelion) around July 5. The Earth's closest approach to the Sun (Perihelion) each year is around January 2. Hence, in general, the distance from the Earth to the Sun is not the major factor determining the heat of Summer or the cold of Winter.

This year, Earth Aphelion will occur early on    Thursday Afternoon, 2025 July 3 at 4:00 p.m. EDT / 20:00 UTC. At that moment, Earth will be the farthest from the Sun for the whole year: 94,502,714.14936769 statute miles / 152,087,376 kilometers.

However, because Earth is farther from the Sun during our Spring and Summer seasons, people in Earth's Northern Hemisphere actually benefit from a few extra days of warmth (on average), than the number of days in the Autumn and Winter seasons of the year. When Earth is closer to the Sun, the Earth travels faster in its elliptical orbit around the Sun (during the Autumn and Winter months); and, when Earth is farther than average from the Sun (during the Spring and Summer seasons) the Earth travels a little more slowly (Kepler's Second Law of Planetary Motion) --- again, this refers to the Northern Hemisphere. Hence, the Spring and Summer seasons, in the Northern Hemisphere, have a few more days than the Autumn and Winter seasons.

In fact, the late Jay Pasachoff, who was Field Memorial Professor of Astronomy at Williams College in Williamstown, Massachusetts and author of widely-used, college astronomy text-books, precisely calculated the duration of each season in the Northern Hemisphere:

* Summer: 93 days, 15 hours

* Spring: 92 days, 19 hours

* Autumn / Fall: 89 days, 20 hours

* Winter: 89 days, 0 hours 

Solar radiation, and hence the heat from the Sun, depends on the length of daylight and the angle of the Sun above the horizon. The tilt of the planet's axis toward the Sun determines the additional and more direct solar radiation received by a planet's Northern or Southern Hemisphere, and hence, the warmer season of the respective hemisphere.

While the Sun does have motions [the Sun rotates on its own axis, but as a sphere of hot plasma the rotation rate varies by Latitude (at the Solar Equator - Sidereal Rotation Period: 24.47 Earth days, Synodic Rotation Rate: 26.24 Earth days; our Solar System revolves around the center of the Milky Way Galaxy once every 225 million-to-250 million Earth years], it is actually the motion of the Earth tilted on its axis, away from the plane of the ecliptic (Earth's orbital plane around the Sun), while revolving around the Sun, that causes the Earth's seasons.

Hence, as the Earth arrives at the point in its orbit around the Sun, when the north polar axis is most directly inclined toward the Sun, this marks the Summer Solstice in the Northern Hemisphere and the Winter Solstice in the Southern Hemisphere.

Alternately, the Winter Solstice in the Northern Hemisphere (the Winter Solstice is always on or near, what we now refer to as, December 21) occurs when the Earth reaches the point in its orbit when the North Pole is most directly inclined away from the Sun (and, the South Pole is most directly inclined toward the Sun). And, conversely, at this time Summer begins in the planet's Southern Hemisphere.

For Earth observers at the North Latitude which matches the Earth's Axial Tilt or Obliquity, at the moment of the June Solstice, the Sun will appear to shine directly overhead. The line around the Earth at the North Latitude which matches the Earth's Axial Tilt or Obliquity is known as the Tropic of Cancer (a.k.a. Northern Tropic). Likewise, the South Latitude which matches the Earth's Axial Tilt or Obliquity is located at the Tropic of Capricorn (a.k.a. Southern Tropic), where the Sun appears directly overhead at the moment of the December Solstice.

However, as the tilt of the Earth is dynamic, and changes minutely over the years, the location of the Tropic lines also change. Currently, these Tropic lines are moving north at the rate of 0.47 arc-seconds / 49.21 feet / 15 meters per year.

The names Tropic of Cancer and Tropic of Capricorn were coined in the last centuries B.C., when the Sun would appear in the Constellation Cancer the Crab on the June Solstice and in the Constellation Capricornus the Horned Goat on the December Solstice. However today, hours after the June Solstice, the Sun enters the Constellation Gemini the Twins, 30 degrees from Cancer. And at the December Solstice, the Sun is now in the Constellation Sagittarius the Archer.

This is due to “Precession of the Equinoxes” of Earth, which is analogous to the wobbling of a spinning top. In the case of the Earth, this 25,772-year wobble causes observers to view the Sun in different parts of the sky over the centuries, at the same time of year while remaining in the same geographical location. As the Earth wobbles over the centuries, the North Pole Star also changes. Currently, Polaris is our North Pole Star; around A.D. 13,700, Vega will be our North Pole Star, due to the Precession of the Equinoxes.

No matter which hemisphere, the day of the Summer Solstice always has the most hours and minutes of daylight (the length of time between Sunrise and Sunset) for the year, while the Winter Solstice always has the least number of hours and minutes of daylight for the year. The exact number of hours and minutes of daylight, for a particular location, depends on the locale's geographic Latitude on the Earth. Astronomers, amateur ("ham") radio operators, and long-distance radio enthusiasts (“radio DXers”), all of whom mostly depend on non-daylight hours to ply their craft, often prefer the days closer to the Winter Solstice.

The Vernal Equinox, when the season of Spring begins in the Northern Hemisphere (and the season of Autumn begins in the Southern Hemisphere), occurs between the Winter and Summer Solstices when the Earth reaches the point in its orbit around the Sun when the Earth's axis is inclined neither toward nor away from the Sun. Likewise, when the Earth reaches the point in its orbit around the Sun, between the Summer and Winter Solstices, when the Earth's axis is inclined neither toward nor away from the Sun, this is known as the Autumnal Equinox (beginning of Fall or Autumn) in the Northern Hemisphere; at this time Spring begins in the Southern Hemisphere. And, half-way between the beginning points of each season are Cross-Quarter Days, each related to traditional holidays: Groundhog Day (February 2), May Day (May 1), Lammas Day (traditionally, the first harvest festival of the year on August 1), and Halloween (October 31).

In ancient times, the Summer Solstice was known as Mid-Summer Day, in early calendars observed around June 24. At that time, May 1 to August 1 (i.e. the two Cross-Quarter Days) was considered the season of Summer. Such early European celebrations were pre-Christian in origin. Many will associate this ancient holiday with the famous William Shakespeare play, “A Midsummer Night's Dream.” Some speculate that the play was written for the Queen of England, to celebrate the Feast Day of Saint John.

As with the Roman Catholic Church's decision to Christianize the pagan Winter Solstice festivals with the introduction of Christmas Day on December 25 (by an early calendar, December 25 was reckoned as the Winter Solstice), the Church began to associate the Mid-Summer festivals with the Nativity of Saint John the Baptist on June 24. In the Christian Bible, the Gospel of Saint Luke implies that Saint John was born six months before the birth of Jesus, although no specific birth dates are given.

The most famous celebration of the Summer Solstice occurs each year at the Stonehenge pre-historic monument in England. Constructed between 3,000 B.C. and 1,600 B.C. in three phases, the actual purpose of the landmark is still unclear. However, it seems to have been associated with burials, originally. It was also used as a type of astronomical observatory, particularly for observing the Sun, which was important to help early cultures make annual decisions regarding agriculture.

Stonehenge is known as a way for pre-historic peoples to mark both the Summer and Winter Solstices. From inside the monument, a viewer facing northeast can watch the Sun rise (weather-permitting) above a stone outside the main circle of rocks, known as the Heel Stone, on the day of the Summer Solstice in the Northern Hemisphere. Although today, due to serious erosion of the stones, visitors on the Summer Solstice can only walk around the landmark from a short distance away during this annual event.

Although not as prominent as Stonehenge, a calendar ring using smaller rocks was also constructed at Nabta Playa in southern Egypt, perhaps as early as 7,000 years ago! As with Stonehenge, some stones aligned with Sunrise on the day of the Summer Solstice.

Today, a Stonehenge-like event occurs each year at the University of Wyoming (UW) Art Museum in Laramie, Wyoming, free-of-charge to the general public. At 12:00 Noon Mountain Daylight Saving Time (MDT) / 2:00 p.m. EDT / 18:00 UTC on the day of the Summer Solstice, visitors can see a single beam of sunlight shine through a solar tube in the ceiling of the UW Art Museum's Rotunda Gallery; the beam of sunlight then shines onto a 1923 Peace Silver Dollar embedded in the floor of the Museum's Rotunda Gallery. Visitors are encouraged to arrive at the museum by 11:30 a.m. MDT / 1:30 p.m. EDT / 17:30 UTC, to view this rather unique architectural feature.

The bright Star Spica (Alpha Virginis), the brightest star in the Constellation Virgo the Virgin and the 16^th brightest star in Earth's night sky (Apparent Visual Magnitude: + 0.97), may have helped develop another one of civilization's early calendars. A calendar of ancient Armenia used the year's first sighting of Spica in the dawn sky, a few days before the Summer Solstice, to mark the beginning of the New Year for this particular calendar. The development of this calendar somewhat coincided with the beginning of agriculture in Armenia.

Like clock-work, a well-known asterism (pattern of stars in the sky, not officially recognized as a constellation) of three stars shaped as a triangle is visible nearly overhead around local midnight during the Summer months (weather-permitting). And logically, as Star Trek's Mr. Spock might say, this asterism is known as the Summer Triangle!

Three of the brightest stars in the Summer sky constitute the Summer Triangle ---

1. Vega (Alpha Lyrae - brightest star in the Constellation Lyra the Harp); brightest of the three stars and closest to the zenith (highest point in the sky);

2. Altair (Alpha Aquilae - denotes the eagle eye and brightest star in the Constellation Aquila the Eagle); second brightest star of the trio;

3. Deneb (Alpha Cygni - denotes the tail star, is the brightest star in the Constellation Cygnus the Swan, and is the “head” star of the asterism known as the Northern Cross).

The term Summer Triangle was popularized in the 1950s by American author H.A. Rey and British astronomer Patrick Moore, although constellation guidebooks mention this triangle of stars as far back as 1913. And, during World War II, military navigators referred to this asterism as the “Navigator's Triangle.”

Regardless of city light pollution, the three bright stars of the Summer Triangle should be visible to nearly everyone in Earth's Northern Hemisphere (weather-permitting). So, just look overhead late-evening or early-morning throughout the Summer for these annual visitors to our Summer sky!

Internet Links to Additional Information ---

Axial Tilt / Obliquity:

Link 1 >>> https://www.timeanddate.com/astronomy/axial-tilt-obliquity.html

Link 2 >>> https://en.wikipedia.org/wiki/Axial_tilt

Summer Solstice: 
Link 1 >>> http://scienceworld.wolfram.com/astronomy/SummerSolstice.html 
Link 2 >>> http://en.wikipedia.org/wiki/Summer_solstice  

Season of Summer: Link >>> http://en.wikipedia.org/wiki/Summer  

History of Mid-Summer: Link >>> http://en.wikipedia.org/wiki/Midsummer
 
Summer "Solstice Day" Annual Free-of-Charge Day (With Snowballs !), 1985 to 1991, at the original Buhl Planetarium and Institute of Popular Science (a.k.a. Buhl Science Center), America's 5th Major Planetarium and Pittsburgh's science and technology museum from 1939 to 1991:  
Link >>> http://spacewatchtower.blogspot.com/2015/06/snowballs-on-first-day-of-summer.html

Stonehenge: Link >>> https://en.wikipedia.org/wiki/Stonehenge

Star Spica: Link >>> https://en.wikipedia.org/wiki/Spica

Precession of the Equinoxes: Link >>> https://en.wikipedia.org/wiki/Axial_precession 

Tropic of Cancer: Link >>> https://en.wikipedia.org/wiki/Tropic_of_Cancer 

Tropic of Capricorn: Link >>> https://en.wikipedia.org/wiki/Tropic_of_Capricorn 

Summer Triangle: Link >>> https://en.wikipedia.org/wiki/Summer_Triangle

Science Experiments Children & Teens Can Do At Home During Summer Break !

Link >>> https://spacewatchtower.blogspot.com/2018/06/science-experiments-children-teens-can.html

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Foriends of the Zeiss     

          "Summer Begins at Solstice Friday Night"

                  Wednesday, 2025 June 18.

            Artificial Intelligence not used in the writing or production of this article.

            © Copyright 2025 Glenn A. Walsh, All Rights Reserved

                             Like This Post? Please Share!

More Astronomy & Science News - SpaceWatchtower 'X' / Twitter News-Feed:
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gaw

Glenn A. Walsh, Informal Science Educator & Communicator                                                             (For more than 50 years! - Since Monday Morning, 1972 June 12):
Link >>> http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: Link >>> http://buhlplanetarium.tripod.com/fotz/
SpaceWatchtower Editor / Author: Link >>> http://spacewatchtower.blogspot.com/
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), America's fifth major planetarium and Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania, the fourth of only five libraries where both construction and endowment funded by famous industrialist & philanthropist Andrew Carnegie.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh: Link >>> http://www.planetarium.cc Buhl Observatory: Link >>> http://spacewatchtower.blogspot.com/2016/11/75th-anniversary-americas-5th-public.html
* Adler Planetarium, Chicago: Link >>> http://adlerplanetarium.tripod.com
* Astronomer, Educator, Optician John A. Brashear: Link >>> http://johnbrashear.tripod.com
* Andrew Carnegie & Carnegie Libraries: Link >>> http://www.andrewcarnegie.cc

 * Other Walsh-Authored Blog & Web-Sites: Link >>> https://buhlplanetarium.tripod.com/gawweb.html

60 Years Ago: Arthur C. Clarke's Vision of Geostationary Satellites Comes True

    

Engineers Stanley R. Peterson (left) and Ray Bowerman check-out Intelsat I or Early Bird prior to launch from Complex 17a, Cape Kennedy (now Cape Canaveral), Florida on 1965 April 6. (Image Sources: NASA, Wikipedia.org, By NASA - Great Images in NASA Description, Public Domain, https://commons.wikimedia.org/w/index.php?curid=686174)

 By Glenn A Walsh

Reporting for SpaceWatchtower

April marks the 60^th anniversary of the orbiting of Intelsat I, the first commercial, geostationary satellite. Also known as Early Bird, the geostationary satellite was popularized 20 years earlier by the famous science-fiction writer and scientist Arthur C. Clarke.

Intelsat I entered a geostationary orbit on 1965 April 6, as the first commercial communications satellite to achieve such an orbit. After some maneuvering, the satellite settled in an orbit over the Atlantic Ocean at 28 degrees West Longitude, where it began commercial service.

Constructed by the Space and Communications Group of Hughes Aircraft Company (later known as the Hughes Space and Communications Company and now known as the Boeing Satellite Systems). It was built for COMSAT (Communications Satellite Corporation), which activated the satellite on 1965 June 28.

Early Bird was based on a series of Syncom satellites built for NASA by the Hughes Aircraft Company. These experimental satellites proved the concept of communications by geostationary satellites.

Early Bird helped to provide live television coverage of the splashdown of the NASA Gemini 6 crewed spacecraft, in December of 1965. Early Bird also was one of the satellites used for the 2-hour Our World, the first live multi-national, multi-satellite television broadcast on 1967 June 25.

Early Bird provided commercial communications services for 4 years and 4 months, ending regular service in January of 1969. It was briefly reactivated in June of 1969 (until 1969 August) to assist in the mission of the NASA Apollo 11 (which was the first mission to land 2 astronauts on the Moon), due to the failure of the then-Atlantic Ocean Intelsat satellite.

Early Bird was the first satellite to provide direct and nearly-instantaneous television, telephone, and telefacsimile transmissions between North America and Europe.

Early Bird was also briefly reactivated for the 25^th anniversary in 1990. Today, Early Bird remains in orbit, inactive as a communications satellite.

A geostationary orbit is also known as a geosynchronous equatorial orbit (GEO). The height above the Earth or altitude of such an orbit is 22,236 statute miles / 35,786 kilometers.

When placed in such an orbit, a satellite orbits the Earth at the same rate of speed as the rotation rate of the Earth. Consequently, the satellite seems to remain fixed in one location above the Earth, even though it is always moving in orbit around the Earth. To match the Earth's rotation rate, the satellite travels at approximately 7,000 statute miles per hour / 11,300 kilometers per hour.

It was in a 1945 paper titled, “Extra-Terrestrial Relays”, that famous science-fiction writer and scientist Arthur C. Clarke proposed using satellites in geostationary orbit as a way to relay radio messages around the world, without the need of cables under the oceans. The proposal was published in the 1945 October issue of the magazine, Wireless World.

In his 1945 article, he discussed the problems of long-distance radio and telephone communications. He maintained that the ionosphere distorted long-distance radio signals, and television signals could not be transmitted by long-distances, without expensive relays about every 50 miles. Arthur C. Clarke wrote, “A relay chain several thousand miles long would cost millions, and transoceanic services would still be impossible”.

He proposed converting the German V2 rockets to more powerful, radio-controlled rockets which could lift “a second moon” into orbit. In addition to relaying communications transmissions, he also suggested that this could be a “space station” where astronomers and other scientists could study astronomy, physics, and meteorology.

In the article, he proposed the launch of a series of GEO communications satellites, which would be equi-distant from one-another around the globe. For complete coverage of the Earth, these satellites would be linked to one-another and to the Earth by radio or optical beams (there was no fully functioning laser until 15 years later, on 1960 May 16, although Albert Einstein established the theoretical foundations for a laser in a 1917 scientific paper).

Internet Links to Additional Information ---

Intelsat I / Early Bird: Link >>> https://en.wikipedia.org/wiki/Intelsat_I

Arthur C. Clarke: Link >>> https://en.wikipedia.org/wiki/Arthur_C._Clarke

"Clarke Suggests Geosynchronous Orbit": Link >>> https://ethw.org/Clarke_Suggests_Geosynchronous_Orbit

"The 1945 Proposal by Arthur C. Clarke for Geostationary Satellite Communications";

Link >>> https://lakdiva.org.lk/clarke/1945ww/

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss     

          "60 Years Ago: Arthur C. Clarke's Vision of Geostationary Satellites Comes True"

                  Sunday, 2025 April 6.

            Artificial Intelligence not used in the writing or production of this article.

            © Copyright 2025 Glenn A. Walsh, All Rights Reserved

                             Like This Post? Please Share!

More Astronomy & Science News - SpaceWatchtower 'X' / Twitter News-Feed:
Link >>> https://twitter.com/spacewatchtower

Astronomy & Science Links: Link >>> http://buhlplanetarium.tripod.com/#sciencelinks

Want to receive SpaceWatchtower blog posts in your in-box ?
Send request to < spacewatchtower@planetarium.cc >.

gaw

Glenn A. Walsh, Informal Science Educator & Communicator                                                             (For more than 50 years! - Since Monday Morning, 1972 June 12):
Link >>> http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: Link >>> http://buhlplanetarium.tripod.com/fotz/
SpaceWatchtower Editor / Author: Link >>> http://spacewatchtower.blogspot.com/
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), America's fifth major planetarium and Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania, the fourth of only five libraries where both construction and endowment funded by famous industrialist & philanthropist Andrew Carnegie.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh: Link >>> http://www.planetarium.cc Buhl Observatory: Link >>> http://spacewatchtower.blogspot.com/2016/11/75th-anniversary-americas-5th-public.html
* Adler Planetarium, Chicago: Link >>> http://adlerplanetarium.tripod.com
* Astronomer, Educator, Optician John A. Brashear: Link >>> http://johnbrashear.tripod.com
* Andrew Carnegie & Carnegie Libraries: Link >>> http://www.andrewcarnegie.cc

 * Other Walsh-Authored Blog & Web-Sites: Link >>> https://buhlplanetarium.tripod.com/gawweb.html

Coordinated Lunar Time Zone for the Moon

                          

This photograph shows the Royal Greenwich Observatory in Greenwich Park in south-east London. Earth time zones were developed from the Prime Meridian, here at Greenwich. Now, scientists are developing a time zone for the Earth;s Moon.

(Image Source: Wikipedia.org, CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=334711)

By Glenn A. Walsh

Reporting for SpaceWatchtower

Time on the Moon is about to become “coordinated”. Both the American Government and the European Union are studying how to establish Coordinated Lunar Time. And, Coordinated Lunar Time would also lead to a separate Global Positioning System (GPS) specifically for the Moon.

Coordinated Lunar Time will be determined by the weighted averaging of atomic clocks on the Moon's surface. This is similar to how standard time is determined on Earth. This project includes the consideration of where on the Moon to place the atomic clocks.

Such a new time standard was first proposed by the European Space Agency (ESA) in early 2023. In April of 2024, the White House asked NASA [through the agency's Space Communication and Navigation (ScaN) Program] to work with U.S. and international scientific agencies for the purpose of establishing Coordinated Lunar Time.

The title of the new lunar time zone comes from Coordinated Universal Time, the Earth time based at the Prime Meridian, established by Great Britain at the beginning of their naval dominance. The Prime Meridian was centered at Britain's Royal Greenwich Observatory, located in Greenwich Park in south-east London.

Today, Coordinated Universal Time (previously known as Greenwich Mean Time and Greenwich Civil Time) is the standard time used by scientists and navigators. All other standard time zones throughout the world are derived from Coordinated Universal Time. Each of the other 23 hourly time zones are a certain number of hours ahead or behind the time zone at the Prime Meridian (occasionally, a half-hour time zone exists, as for the Canadian province of Newfoundland).

Space missions to the Moon now use either Coordinated Universal Time or the time zone of origin of the space mission. This time could be Houston time (Central Time Zone at NASA's Johnson Space Center), Los Angeles time (Pacific Time Zone for Pasadena's Jet Propulsion Laboratory of the California Institute of Technology), Moscow time (for Russian missions), China Standard Time (for Chinese missions), or Indian time (for missions from India).

As more nations and private companies send missions to the Moon, there needs to be a common time zone, that all space missions use, to avoid confusion.

Further, time passes on the Moon, and in lunar orbit, at different rates. And, these times also differ from how time passes on the Earth or in Earth orbit.

This is due to the fact that clocks tick more slowly when in Earth orbit, than clocks on the ground. This is also true for the Moon and lunar orbit.

Also, clocks on the Moon tick fractionally faster than clocks on Earth, because the Moon has a much less gravitational attraction than gravity on the Earth. Gravity on the Moon is about 1/6 the attraction of gravity on Earth.

Plus, scientists have to consider that the Moon orbits the Earth. So, as the Earth's gravity is strong enough to keep the Moon in Earth orbit, the Earth's gravity can also have an affect on lunar time.

The lunar time standard being proposed would solve these types of time-keeping issues. According to Arati Prabkahar, who was the Director of the White House Office of Science and Technology Policy and Science Advisor to the President (during much of the Administration of U.S. President Joe Biden), lunar time would currently "appear to lose on average 58.7 microseconds per Earth-day and come with other periodic variations that would further drift Moon time from Earth time"

For perspective, consider that a hummingbird's wings flap at a rate of about 50 times per second. Each flap has a duration of about 0.02 second or 20/000 microseconds.

This is all due to the effects of relativity. Albert Einstein's General Theory of Relativity states that gravity affects time, or space-time as he referred to it. Dr. Einstein's research showed that time does not flow uniformly everywhere. Hence, scientists must grapple with all of the variations in time at different locations, to ensure that clocks and GPS work properly in any locality.

Once developed, this new time standard is meant to be used by all nations and companies sending missions to the Moon. Initially, it will be developed and instituted through a collaboration of members of the Artemis Accords. The Artemis Accords (named for the Artemis mission to send U.S. astronauts, including the first woman and the first astronaut of-color, back to the Moon) are a series of non-binding, multilateral arrangements between the United States and other governments on Earth, which elaborates on the norms expected by space-faring nations.

There are four key features of this new time standard, initially:

• Traceability back to  Coordinated Universal Time.

• Accuracy sufficient for navigation and science.

• Resilience to disruptions.

• Scalability to potential environments beyond the Earth – Moon system.

In August of 2024, the U.S. National Institute of Standards and Technology (NIST) released a draft of the proposed standard. The draft focuses on the framework and mathematical model, which takes into account the gravitational differences on the Moon.

This draft was published in The Astronomical Journal, a leading scientific publication.

A unified time standard for the Moon, and possibly including other celestial bodies, is expected by 2026, as requested by the Biden Administration.

Internet Links to Additional Information ---

The Moon of Earth: Link >>> https://en.wikipedia.org/wiki/Moon

Timekeeping on the Moon: Link >>> https://en.wikipedia.org/wiki/Timekeeping_on_the_Moon

NASA News Release: "NASA to Develop Lunar Time Standard for Exploration Initiatives":

Link >>> https://www.nasa.gov/general/nasa-to-develop-lunar-time-standard-for-exploration-initiatives/

NIST News Release: "What Time Is It on the Moon?":

Link >>> https://www.nist.gov/news-events/news/2024/08/what-time-it-moon

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss     

               "Coordinated Lunar Time Zone for the Moon"

                  Monday, 2025 January 27.

            Artificial Intelligence not used in the writing or production of this article.

            © Copyright 2025 Glenn A. Walsh, All Rights Reserved

                             Like This Post? Please Share!

More Astronomy & Science News - SpaceWatchtower 'X' / Twitter News-Feed:
Link >>> https://twitter.com/spacewatchtower

Astronomy & Science Links: Link >>> http://buhlplanetarium.tripod.com/#sciencelinks

Want to receive SpaceWatchtower blog posts in your in-box ?
Send request to < spacewatchtower@planetarium.cc >.

gaw

Glenn A. Walsh, Informal Science Educator & Communicator                                                             (For more than 50 years! - Since Monday Morning, 1972 June 12):
Link >>> http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: Link >>> http://buhlplanetarium.tripod.com/fotz/
SpaceWatchtower Editor / Author: Link >>> http://spacewatchtower.blogspot.com/
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), America's fifth major planetarium and Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania, the fourth of only five libraries where both construction and endowment funded by famous industrialist & philanthropist Andrew Carnegie.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh: Link >>> http://www.planetarium.cc Buhl Observatory: Link >>> http://spacewatchtower.blogspot.com/2016/11/75th-anniversary-americas-5th-public.html
* Adler Planetarium, Chicago: Link >>> http://adlerplanetarium.tripod.com
* Astronomer, Educator, Optician John A. Brashear: Link >>> http://johnbrashear.tripod.com
* Andrew Carnegie & Carnegie Libraries: Link >>> http://www.andrewcarnegie.cc

 * Other Walsh-Authored Blog & Web-Sites: Link >>> https://buhlplanetarium.tripod.com/gawweb.html

Fall Begins at Equinox Sunday Morning

     

This diagram shows the position of the Earth, in relation to the Sun, at the time of the Autumnal Equinox, as well as the other equinox and solstices of the year.

[Graphic Source: ©1999, Eric G. Canali, former Floor Operations Manager of the original Buhl Planetarium and Institute of Popular Science / Buhl Science Center (America's 5th major planetarium & Pittsburgh's science and technology museum from 1939 to 1991) and Founder of the South Hills Backyard Astronomers amateur astronomy club. Permission granted for non-profit use only, with credit to author.]

By Glenn A. Walsh

Reporting for SpaceWatchtower

The Autumnal Equinox Sunday morning marks the end of the season of Summer and the beginning of Fall or Autumn in Earth's Northern Hemisphere. In the Southern Hemisphere, this marks the transition from Winter to Spring.

The Autumnal Equinox (also known as the September Equinox), the end of Summer and the beginning of the season of Autumn or Fall in Earth's Northern Hemisphere, occurs Sunday Morning, 2024 September 22 at 8:44 a.m. Eastern Daylight Saving Time (EDT) / 12:44 Coordinated Universal Time (UTC). In the Southern Hemisphere, this moment marks the astronomical beginning of the season of Spring.

Autumn or Fall continues in the Northern Hemisphere, and Spring in the Southern Hemisphere, until the December Solstice: Saturday Morning, 2024 December 21 at 4:21 a.m. Eastern Standard Time (EST) / 9:21 UTC. At the moment of the December Solstice, Winter begins in the Northern Hemisphere and Summer begins in the Southern Hemisphere.

The approximate and traditional mid-way point between the Autumnal Equinox and the Winter Solstice comes in the vicinity of October 31 (All-Hallows Eve or Halloween) / November 1 (All-Saints Day) / November 2 (All-Souls Day): the Astronomical Cross-Quarter Day of Samhain or All-Hallowsmas. The actual November Cross-Quarter Day will be Wednesday Afternoon, 2024 November 6 at .5:21 p.m. EST / 22:21 UTC. The approximate one-week discrepancy between the dates of the traditional and actual Cross-Quarter Day is due to the fact that the traditional date of Samhain was fixed on October 31, when the Julian Calendar was still in use.

In ancient times, a calendar season was considered the time between one Cross-Quarter Day and the next Cross-Quarter Day. So, Autumn was considered the time between August 1 (Lughnasadh or Lammas Day), which was the traditional beginning of the wheat harvest, to October 31 (Samhain). Samhain actually means “Summer's end” as the Celtic calendar only considered two main seasons: Summer and Winter.

The Celtic peoples of Ireland began celebrations on Samhain in the 5^th century B.C. Samhain was considered by the Celtics and Druids on the British Isles as the end of the old year, with the following day the beginning of the New Year. In A.D, 835, the Roman Catholic Church named November 1 All-Saints Day with the previous day becoming All-Hallows Eve or Halloween, the eve or evening before All-Saints Day.

It is believed that in ancient times the Pleiades Star Cluster, also known as the Seven Sisters, culminated (climbed to the cluster's highest point in the sky) around Midnight local time on or near Samhain. Samhain and Pleiades Culmination would have occurred together around A.D. 11^th and 12^th centuries before the Gregorian Calendar was instituted. For the Pleiades Culmination to occur during the dark time of the year's end, many peoples felt this was a time to honor the dead. Although today Pleiades Culmination occurs on November 21, the Pleiades still can be seen high in the sky around local Midnight on Halloween, weather-permitting.

On the day of the Equinox, the Sun appears directly overhead at local Noon on the Equator. At the moment of Equinox, the Northern and Southern Hemispheres of Earth are illuminated equally. And, the time of Equinox is the only time when the Earth Terminator (dividing line on Earth between daylight and darkness) is perpendicular to the Equator.

This, and the reason for seasons on Earth in the first place, is due to the fact that Earth rotates on its axis, which is tilted at an approximate 23.44-degree angle from the Ecliptic, the plane of the Earth's orbit around the Sun. As the Earth revolves around the Sun, this axial tilt causes one hemisphere of the planet to receive more direct solar radiation during that hemisphere's season of Summer and much less direct solar radiation about a half-year later during that hemisphere's season of Winter. As mentioned, during an Equinox [in the Northern Hemisphere: about half-way between Summer and Winter (Autumnal Equinox), and about half-way between Winter and Summer (Vernal Equinox)] both planetary hemispheres receive an equal amount of solar radiation. 

Although "Equinox" in Latin means equal-night, the day of the Equinox does not actually have an equal amount of daylight and nightfall, as it appears on the Earth's surface. If the Sun was just a pin-point of light in our sky, as all other stars appear, day and night would be equal.

But, because the Sun is a disk, part of the Sun has risen above the horizon before the center of the Sun (which would be the pin-point of light); so there are extra moments of light on the Equinox. Likewise, part of the Sun is still visible, after the center of the Sun has set.

Additionally, the refraction of sunlight by our atmosphere causes sunlight to appear above the horizon, before sunrise and after sunset.

Each year, September 25 or 26 marks the Equilux ("equal-light"), the actual day with equal hours and minutes of the Sun above the horizon, and equal hours and minutes of the Sun below the horizon. The Equilux occurs twice each year, approximately 3-to-4 days before the Vernal Equinox, when Spring begins,  and 3-to-4 days after the Autumnal Equinox, after Autumn or Fall has begun.

An urban legend that has been making the rounds for decades has it that eggs can be stood on their ends only during an Equinox, whether the Vernal Equinox in the Spring or the Autumnal Equinox in the Fall. This is completely false. Depending greatly on the size and shape of the particular egg, eggs can be stood on their ends any day of the year! Astronomy has nothing to do with whether an egg can stand on its end. If an egg can stand on its end on the Equinox (and, due to the shape and size of some eggs, this is not even possible), it can stand the same way any other day of the year.

In the last few years, with the help of the Internet and Social Media, another urban legend has become prevalent. Now it is claimed that brooms can stand, on their own, on their bristles, only on an Equinox day. This is also false. Again, as with eggs, if a broom can stand on its bristles by itself (this usually only works with newer brooms, with more stiff and even bristles) on an Equinox, it can do so any day of the year!

In China, Vietnam, Korea, Japan, and other nations in East and Southeast Asia, a popular harvest festival is celebrated on the date close to the Autumnal Equinox of the Solar Cycle, as well as close to the Harvest Moon. This Mid-Autumn Festival / Moon Festival dates back more than 3,000 years to Moon worship in China's Shang Dynasty.

Again, as Western Cultures consider September the beginning of Autumn (meteorologists and climatologists consider September 1 the beginning of Meteorological Autumn), the ancients often termed this as "Mid-Autumn". By this reckoning, Autumn actually began at the traditional Cross-Quarter Day of August 1 (when some harvesting actually begins) and ends at the traditional Cross-Quarter Day of All-Hallow's Eve, also known as Halloween.

On the Chinese Han Calendar, the Mid-Autumn Festival falls on the 15th day of the 8th month (on a day between September 8 and October 7 in our Gregorian Calendar). This usually falls on the night of a Full Moon, the Harvest Moon. This year, the Harvest Moon occurred on Tuesday Evening, 2024 September 17 at 10:34 p.m. EDT / September 18, 2:34 UTC. This particular Harvest Moon was also a so-called “Super-Moon” (Lunar Perigee Full Moon), which experienced a shallow Partial Lunar Eclipse / Partial Eclipse of the Moon.

September 22 is designated as Falls Prevention Awareness Day.

Internet Links to Additional Information ---

Mid-Autumn Festival / Moon Festival: Link >>> https://en.wikipedia.org/wiki/Mid-Autumn_Festival

Cross-Quarter Day: Link >>> https://en.wikipedia.org/wiki/Wheel_of_the_Year

Autumnal Equinox: Link >>> http://scienceworld.wolfram.com/astronomy/AutumnalEquinox.html

Season of Autumn or Fall: Link >>> http://en.wikipedia.org/wiki/Autumn

Equinox: Link >>> http://en.wikipedia.org/wiki/Equinox

Equilux: Link >>> https://darkskydiary.wordpress.com/2010/03/20/equinox-equilux-and-twilight-times/

Earth's Seasons: Link >>> http://en.wikipedia.org/wiki/Season

Tilt of a planet's axis: Link >>> http://en.wikipedia.org/wiki/Axial_tilt

Urban legend of eggs and brooms standing on their own, only on an Equinox:
Link >>> http://www.snopes.com/science/equinox.asp

Falls Prevention Awareness Day: Link >>> https://nationaltoday.com/falls-prevention-awareness-day

Why Autumn Leaves Change Color: Link >>> http://spacewatchtower.blogspot.com/2013/10/colorful-fall-foliage-astronomy-affects.html

Related Blog-Post ---

"Partial Eclipse of Harvest Moon Tue. Night". Fri., 2024 Sept. 13.

Link >>> https://spacewatchtower.blogspot.com/2024/09/partial-eclipse-of-harvest-moon.html 

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss     

               "Fall Begins at Equinox Sunday Morning"

                  Friday, 2024 September 20.

            Artificial Intelligence not used in the writing or production of this article.

            © Copyright 2024 Glenn A. Walsh, All Rights Reserved

                             Like This Post? Please Share!

More Astronomy & Science News - SpaceWatchtower 'X' / Twitter News-Feed:
Link >>> https://twitter.com/spacewatchtower

Astronomy & Science Links: Link >>> http://buhlplanetarium.tripod.com/#sciencelinks

Want to receive SpaceWatchtower blog posts in your in-box ?
Send request to < spacewatchtower@planetarium.cc >.

gaw

Glenn A. Walsh, Informal Science Educator & Communicator                                                             (For more than 50 years! - Since Monday Morning, 1972 June 12):
Link >>> http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: Link >>> http://buhlplanetarium.tripod.com/fotz/
SpaceWatchtower Editor / Author: Link >>> http://spacewatchtower.blogspot.com/
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), America's fifth major planetarium and Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania, the fourth of only five libraries where both construction and endowment funded by famous industrialist & philanthropist Andrew Carnegie.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh: Link >>> http://www.planetarium.cc Buhl Observatory: Link >>> http://spacewatchtower.blogspot.com/2016/11/75th-anniversary-americas-5th-public.html
* Adler Planetarium, Chicago: Link >>> http://adlerplanetarium.tripod.com
* Astronomer, Educator, Optician John A. Brashear: Link >>> http://johnbrashear.tripod.com
* Andrew Carnegie & Carnegie Libraries: Link >>> http://www.andrewcarnegie.cc

 * Other Walsh-Authored Blog & Web-Sites: Link >>> https://buhlplanetarium.tripod.com/gawweb.html

Partial Eclipse of Harvest Moon Tue. Night

     

The Harvest Moon often appears orange in color due to Rayleigh Scattering of sunlight from the Moon, which occurs whenever the Moon is near the horizon. The Harvest Moon always rises around the time of local sunset. (Image Sources: Wikipedia.org, By The original uploader was Roadcrusher at English Wikipedia. - Transferred from en.wikipedia to Commons by Khayman using CommonsHelper., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=15755496)

By Glenn A. Walsh

Reporting for SpaceWatchtower

Tuesday evening, the Full Harvest Moon (which some would call the second so-called “Super-Moon” of 2024) comes with a bonus – a Partial Lunar Eclipse / Partial Eclipse of the Moon, which will be visible in most of the Western Hemisphere, Europe, Africa, and the Middle East. However, this Eclipse, which is safe to watch directly (weather-permitting), will be a very slight or shallow Lunar Eclipse.

Partial Lunar Eclipse / Partial Eclipse of the Moon

A Lunar Eclipse / Eclipse of the Moon is the only category of eclipses which is safe to view with the unaided eyes (one-power), binoculars, and a telescope.

A Live-stream Web-cast of this Partial Lunar Eclipse / Partial Eclipse of the Moon will be available for observers not in a region where the eclipse is visible in the sky, or where weather conditions make such an observation impossible (Internet link to this Live-stream near the end of this blog-post).

Everyone on the night or dark side of the Earth can view at least part of any Lunar Eclipse / Eclipse of the Moon, weather-permitting. People located where weather blocks direct view of the Eclipse, or who live in other parts of the world, would need to watch the eclipse on the Internet.

Here are the major stages of this Partial Lunar Eclipse / Partial Eclipse of the Moon –--

Late Tuesday Evening, 2024 September 17 / Wednesday Morning, 2024 September 18 -

[Eastern Daylight Saving Time (EDT) / Coordinated Universal Time (UTC)]

(Note that a Lunar Eclipse / Eclipse of the Moon is the only type of Eclipse where the times of Eclipse are the same world-wide, when using Coordinated Universal Time. Everyone on the dark or night side of Earth can view this Eclipse in the sky, weather-permitting.)

Penumbral Lunar Eclipse Begins --- Sept. 17, 8:41:07 p.m. EDT / Sept. 18, 0:41:07 UTC

Partial Lunar Eclipse Begins --- Sept. 17, 10:12:58 p.m. EDT / Sept. 18, 2:12:58 UTC

Primary Moon Phase: Full Moon – Harvest Moon --- Sept. 17, 10:34 p.m. EDT / Sept. 18, 2:34 UTC

Greatest Partial Lunar Eclipse --- Sept. 17, 10:44:18 a.m. EDT / Sept. 18, 2:44:18 UTC

Partial Lunar Eclipse Ends --- Sept. 17, 11:15:38 p.m. EDT / Sept. 18, 3:15:38 UTC

Penumbral Lunar Eclipse Ends  --- Sept. 18, 12:47:27 a.m. EDT / Sept. 18, 4:47:27 UTC

At the time of Greatest Partial Lunar Eclipse / Partial Eclipse of the Moon on September 17, the Moon will be only 3.5 per-cent obscured by the Earth's Umbral shadow. The remaining portion of the Moon's surface will be well within the Penumbral shadow of the Earth. At this time, the Moon will appear as if a small chip, in the upper right portion of the Moon, has been removed, while the rest of the Moon may appear a wee-bit dimmer than normal. Thus, this a very shallow Partial Lunar Eclipse / Partial Eclipse of the Moon.

And, the bright object near the Moon during this Eclipse will be the ringed-planet Saturn.

A Lunar Eclipse / Eclipse of the Moon occurs when the orbit of the Moon brings our natural satellite into the Earth's shadow (shadow caused by the Earth completely blocking light from the Sun). The Earth's shadow, extending into Outer Space from the dark or night side of Earth, is divided into two sections: the dim Penumbra or Penumbral shadow, which encircles the deeper Umbra or Umbral shadow. The Moon's orbit is slightly tilted, so most months at the primary Moon phase of Full Moon, the Moon moves above or below the Earth's shadow, with no Eclipse occurring.

A Lunar Eclipse / Eclipse of the Moon always occurs near the time, and including the time, of a Full Moon. Many Native Americans called the Full Moon of November the Corn Moon or Barley Moon in addition to being known to European and American farmers as the Harvest Moon, but, more on that later.

When the Earth's dim shadow, known as the Penumbra, falls on the Moon, it is called a Penumbral Lunar Eclipse / Penumbral Eclipse of the Moon. Because the Earth's shadow is dim in this case, this type of Eclipse is difficult to discern.

When the Earth's deep shadow, known as the Umbra, falls on only part of the Moon's surface, this is known as a Partial Lunar Eclipse / Partial Eclipse of the Moon. This is more easily visible, if you are in the right location and weather conditions are acceptable.

A Total Lunar Eclipse / Total Eclipse of the Moon is when the Earth's deep shadow, or Umbra, completely envelops the Moon. Usually, a Total Lunar Eclipse / Total Eclipse of the Moon only occurs once every 2.5 years, approximately, as seen from someplace in the world. The last one was seen in North America on 2022 May 15 / 16.

Of course, "Totality" / Total Phase of a Total Lunar Eclipse / Total Eclipse of the Moon is the most impressive part of this type of Eclipse, what most people wait to see. The Partial Phases of the Eclipse are when a piece of the Moon seems missing, as the Moon moves further into the Earth's main shadow known as the Umbra, or as the Eclipse is ending and the Moon is further moving out of the Earth's Umbra.

The Penumbral Phases of the Eclipse are difficult to see, as the Moon moves into or out of the Earth's secondary shadow or Penumbra. In this case, one would not see any chunks or bites taken out of the Moon's disk, as one would see when the Moon moves into the Umbra shadow during the Partial Phases. Instead, if your eyes are very good, you may notice a slight dimming of the light coming from the Moon, as the Moon moves further into the Penumbral shadow

Although no direct sunlight reaches the Moon during a Total Lunar Eclipse / Total Eclipse of the Moon, the Earth's atmosphere refracts the sunlight around our planet allowing a portion of the sunlight to continue to be transmitted to the Moon. However, the refracted light reaching the Moon is primarily in the yellow, orange, and red portions of the electromagnetic spectrum (the Earth's atmosphere filters-out the violet, blue, and green colors), as with orange or red-tinted sunrises and sunsets (during such a Total Lunar Eclipse / Total Eclipse of the Moon, a person standing on the side of the Moon facing Earth could see all Earth sunrises and sunsets simultaneously, as they viewed the Earth in a Total Solar Eclipse / Total Eclipse of the Sun --- but, even on the Moon, a person would need to take strong precautions to ensure their eye-sight is not damaged by such a view). Hence, it is orange or red light that is reflected from the Moon back into your eyes during a Total Lunar Eclipse / Total Eclipse of the Moon.

Hence, particularly during the middle of a Total Lunar Eclipse / Total Eclipse of the Moon, the Moon will not disappear from view but can be seen with an orange or reddish tint, what some call "blood red" (this is sometimes referred to as a “Blood Moon”). If the Earth had no atmosphere, likely no sunlight would reach the Moon during a Total Lunar Eclipse / Total Eclipse of the Moon, and there would be no "Blood Moon;" the Moon would seem to completely disappear.

Harvest Moon

More evening light, coming just after the earlier sunsets of late Summer and early Autumn, occur with the Harvest Moon (the Full Moon of September) and a few days near the day of this Full Moon (weather-permitting). Traditionally, this time of year helped give farmers more light in the evening as they work to harvest their crops before the coming Winter. However, anyone can take advantage of this extra evening light, as the early Autumn evenings continue with moderate temperatures.

For this year, the Harvest Moon will be the Full Moon of Tuesday Evening, 2024 September 17, at 10:34 p.m. Eastern Daylight Saving Time (EDT) / September 18, 2:34 Coordinated Universal Time (UTC). Of course, the Harvest Moon becomes visible (weather-permitting) in the vicinity of the time of sunset on the days around the day of Full Moon.

For farmers eager to finish harvesting their crops, the bright Full Moon which shines on their farms for the several evenings closest to the Autumnal Equinox is called the Harvest Moon. This year the Autumnal Equinox, the beginning of the season of Autumn or Fall in the Earth's Northern Hemisphere and the beginning of the season of Spring in the Southern Hemisphere, will occur on Sunday Morning, 2024 September 23 at 8:44 a.m. EDT / 12:44 UTC.

The Harvest Moon is one of the signature astronomical events shortly before the beginning of, or shortly after the beginning of, the Fall season. It is an event particularly anticipated by farmers of both the past and the present. As many crops reach the time of harvest in late Summer and early Autumn, often the work of the harvest has to continue past sunset, which comes earlier and earlier each evening.

Nature has come to the rescue of these farmers, with a bright Full Moon (weather-permitting), which arrives just around the time of sunset, that allows farmers and their staff to continue the harvest after the Sun's direct light has dissipated. Hence, long-ago this Full Moon came to be known as the Harvest Moon.

For a similar reason, the Full Moon of October is often known as the Hunter's Moon, which allowed Native Americans to continue the hunt after sunset, to begin to store meat for the coming Winter months. However, the Harvest Moon is designated as the closest Full Moon to the Autumnal Equinox, and such a Full Moon does not always occur in September. Every few years the Harvest Moon occurs in October, shortly after the Autumnal Equinox. During those years, the Hunter's Moon occurs in November.

This year, the Hunter's Moon occurs on Thursday Morning, 2024 October 17 at 7:26 a.m. EDT / 11:26 UTC. Of course, the Hunter's Moon becomes visible (weather-permitting) in the vicinity of the time of sunset on the days around the day of Full Moon. This year's Hunter's Moon will be another so-called “Super-Moon” (the third of four so-called “Super-Moons” in 2024), being the largest Full Moon of 2024.

On average, the Moon rises about 50 minutes later each day. However, during the days near the Autumnal Equinox, the Moon rises each day only about 25-to-35 minutes later each day in the U.S.A., and only 10-to-20 minutes later each day in much of Canada and Europe. Thus, for several days around the time of the Autumnal Equinox, the Harvest Moon appears to rise around the same time each evening (roughly coinciding with local sunset), providing light at the time most needed by farmers.

The reason for this is due to the Ecliptic, the apparent path of the Sun, Moon, and planets through Earth's sky, which makes a narrow angle with the horizon this time of year. It is this narrow angle which provides that moonrise occurs around the time of sunset, near the time of the Full Moon of September (for the Harvest Moon) and near the time of the Full Moon of October (for the Hunter's Moon). Hence, several evenings (before darkness has fallen) appear to have a rising Full Moon.

Also, at this time of year when farmers need moonlight the most, the Harvest Moon appears larger and more prominent, due to the mysterious but well-known "Moon Illusion" that makes the Moon seem larger when it is near the horizon. And, while near the horizon, the Moon is often reddened by clouds and dust, creating the appearance of a large, rising red ball.

Some even liken a rising Harvest Moon to a rising "Great Pumpkin," of Peanuts comic-strip fame! In the Peanuts' network-television cartoon just before Halloween each year (originally aired on CBS-TV on 1966 October 27) titled, "It's the Great Pumpkin, Charlie Brown", the “Great Pumpkin” rises over the pumpkin patch to provide gifts to all good little boys and girls.

In China, Vietnam, Korea, Japan, and other nations in East and Southeast Asia, a popular harvest festival is celebrated on the date close to the Autumnal Equinox of the Solar Cycle, as well as close to the Harvest Moon. This Mid-Autumn Festival / Moon Festival dates back more than 3,000 years to Moon worship in China's Shang Dynasty.

Although Western Cultures consider September the beginning of Autumn (meteorologists and climatologists consider September 1 the beginning of Meteorological Autumn), the ancients often termed this as "Mid-Autumn". By this reckoning, Autumn actually began at the traditional Cross-Quarter Day of August 1 (when harvesting of wheat usually begins) and ends at the traditional Cross-Quarter Day of All-Hallow's Eve, also known as Halloween.

On the Chinese Han Calendar, the Mid-Autumn Festival falls on the 15th day of the 8th month (on a day between September 8 and October 7 in our Gregorian Calendar). This usually falls on the night of a Full Moon, the Harvest Moon.

This year's Harvest Moon will also be a so-called "Super-Moon", the second of four in 2024. A so-called "Super-Moon" occurs when the Full Moon is closer to the Earth than average, and hence, the Moon appears a little larger than average in the sky.

The orbit of the Moon around the Earth is not a perfect circle, but an ellipse. Hence, during the near-monthly orbit of the Moon around the Earth, at one time during the month the Moon is closer to the Earth than normal (known as Lunar Perigee) and about a half-month later the Moon is farther from the Earth than normal (known as Lunar Apogee). Hence, when the Primary Moon Phase of Full Moon occurs at or near Lunar Perigee, some people refer to the slightly larger visible Full Moon as a so-called "Super-Moon".

This month's Lunar Perigee occurs about 10 hours after the Harvest Moon - Wednesday Morning, 2024 September18 at 9:00 a.m. EDT / 13:00 UTC: 222,007.228 statute miles / 357,286 kilometers distance of the Moon from Earth. 

Native Americans also called the Full Moon of September the Corn Moon or Barley Moon, as Corn and Barley were among their main crops. Sometimes, the September Full Moon in the Northern Hemisphere is also known as the Fruit Moon. Other Full Moon names for September include Chrysanthemum Moon (China), Singing Moon (Celtic), Nut Moon (American Indian - Cherokee), Mulberry Moon (American Indian - Choctaw), and Moon When the Calves Grow Hair (American Indian - Dakotah Sioux).

In the Southern Hemisphere, where Winter is turning to Spring, the September Full Moon is known as the Lenten Moon, Worm Moon, Crow Moon, Sugar Moon, Chaste Moon, or Sap Moon. Another Full Moon name for September includes Storm Moon (South Africa). 

The Harvest Moon in the Southern Hemisphere occurs in March or April, with the same advantages to Southern Hemisphere farmers as the Harvest Moon in the Northern Hemisphere.

Live-stream Web-cast of this Partial Lunar Eclipse / Partial Eclipse of the Moon can be found at the following Internet link --

Link >>> https://www.timeanddate.com/live/eclipse-lunar-2024-september-18 

Internet Links to Additional Information ---

Moon: Link >>> https://en.wikipedia.org/wiki/Moon

Lunar Eclipse / Eclipse of the Moon: Link >>> https://en.wikipedia.org/wiki/Lunar_eclipse

Harvest Moon: Link >>> https://en.wikipedia.org/wiki/Full_moon#Harvest_moon

Why Autumn Leaves Change Color: Link >>> http://spacewatchtower.blogspot.com/2013/10/colorful-fall-foliage-astronomy-affects.html

Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss    

 

               "Partial Eclipse of Harvest Moon Tue. Night"

                  Friday, 2024 September 13.

            Artificial Intelligence not used in the writing or production of this article.

            © Copyright 2024 Glenn A. Walsh, All Rights Reserved

                             Like This Post? Please Share!

More Astronomy & Science News - SpaceWatchtower 'X' / Twitter News-Feed:
Link >>> https://twitter.com/spacewatchtower

Astronomy & Science Links: Link >>> http://buhlplanetarium.tripod.com/#sciencelinks

Want to receive SpaceWatchtower blog posts in your in-box ?
Send request to < spacewatchtower@planetarium.cc >.

gaw

Glenn A. Walsh, Informal Science Educator & Communicator                                                             (For more than 50 years! - Since Monday Morning, 1972 June 12):
Link >>> http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: Link >>> http://buhlplanetarium.tripod.com/fotz/
SpaceWatchtower Editor / Author: Link >>> http://spacewatchtower.blogspot.com/
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), America's fifth major planetarium and Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee, Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania, the fourth of only five libraries where both construction and endowment funded by famous industrialist & philanthropist Andrew Carnegie.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh: Link >>> http://www.planetarium.cc Buhl Observatory: Link >>> http://spacewatchtower.blogspot.com/2016/11/75th-anniversary-americas-5th-public.html
* Adler Planetarium, Chicago: Link >>> http://adlerplanetarium.tripod.com
* Astronomer, Educator, Optician John A. Brashear: Link >>> http://johnbrashear.tripod.com
* Andrew Carnegie & Carnegie Libraries: Link >>> http://www.andrewcarnegie.cc

 * Other Walsh-Authored Blog & Web-Sites: Link >>> https://buhlplanetarium.tripod.com/gawweb.html