This diagram shows the position of the Earth, in relation to the Sun, at the time of the Vernal Equinox at the official beginning of the season of Spring in the Earth's Northern Hemisphere (Autumn in Earth's Southern Hemisphere), as well as the other solstices and equinox of the year.
(Graphic Source: ©1999, Eric G. Canali, former Floor Operations Manager of the original Buhl Planetarium and Institute of Popular Science (a.k.a. Buhl Science Center - Pittsburgh's science and technology museum from 1939 to 1991) and Founder of the South Hills Backyard Astronomers amateur astronomy club; permission granted for only non-profit use with credit to author.)
By Glenn A. Walsh
Reporting for SpaceWatchtower
Spring begins Wednesday afternoon at
the moment of the Vernal Equinox in Earth's Northern Hemisphere. In
the Southern Hemisphere of Earth, this marks the astronomical
beginning of the season of Autumn. On Mars, the Vernal Equinox
marks the beginning of the New Year on March 23! And, a so-called "Super-Moon" also occurs on March 20!
Vernal Equinox on Earth
Vernal Equinox on Earth
The Vernal Equinox occurs on Earth at
precisely: 5:58 p.m. Eastern Daylight Saving Time (EDT) / 21:58
Coordinated Universal Time (UTC) on Wednesday Afternoon, 2019 March
20.
As the diagram at the beginning of this
blog-post demonstrates, on the day of 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 a 23.439281-degree angle from 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 a half-year later during that hemisphere's season of Winter. As mentioned, during an Equinox (about half-way between Summer and Winter, and about half-way between Winter and Summer) both planetary hemispheres receive an equal amount of solar radiation.
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 a 23.439281-degree angle from 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 a half-year later during that hemisphere's season of Winter. As mentioned, during an Equinox (about half-way between Summer and Winter, and about half-way between Winter and Summer) 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.
March 16 marked 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 and 3-to-4 days
after the Autumnal Equinox (September 25).
An urban legend that has been making
the rounds for decades, now exacerbated by the Internet and Social
Media, 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 even bristles) on an Equinox, it can do so any 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 even bristles) on an Equinox, it can do so any day of the year!
In ancient times, the Vernal Equinox
was considered the beginning of the new calendar year. This was when
most of Western Civilization used the Julian Calendar, and the Vernal
Equinox occurred on March 25, later observed by Christians as the
Feast of the Annunciation (observed nine full months before Christmas
Day). As part of the Gregorian Calendar reform, in October of 1582,
Pope Gregory XIII chose the Feast of the Circumcision of Christ
(January 1) as the beginning of the New Year in the Roman Catholic
Church's Liturgical Year.
The Vernal Equinox continues to be
considered the beginning of the New Year, or an important holy day,
in several other places on Earth ---
* Beginning of New Year (using the Solar
Calendar) - Nowruz: Afghanistan and Iran / Persia.
* Holy Day for adherents to the
Zoroastrian Religion and Baha'i Naw-Ruz, one of nine holy days of the
Bahá'í Faith.
NASA and the European Space Agency
(ESA) observe Sun-Earth Day on or near the Vernal Equinox. This is a
joint educational program started in 2000, to popularize the
knowledge about the Sun, and the way it influences life on Earth,
among students and the public. This is part of Solar Week, which is
the calendar week that includes the Vernal Equinox.
The first week of Spring, beginning
with the Vernal Equinox, has been declared by physicians as Medicine
Cabinet Clean-Up Week. To avoid prescription drug abuse, particularly
important at this time of the opioid crisis, physicians encourage
everyone to get rid of unused and no-longer-needed medications and
other drugs, which may have lingered in the household, as part of an
annual Spring cleaning. Several states have prescription drug
take-back locations, where these drugs can be dropped-off.
The week of the Vernal Equinox is the
also the beginning of the National Cherry Blossom Festival held each
year in Washington, DC, which begins on March 20. This festival
commemorates the 1912 gift of 3,000 cherry trees from the Mayor of
Tokyo to the City of Washington. The festival runs through April 14
this year.
Vernal Equinox on Mars
Earth is not the only planet to
experience a Vernal Equinox this month. Just three days later, on
March 23, the Vernal Equinox occurs on the Planet Mars. It is purely
coincidental that the Vernal Equinox on Earth and Mars are so close
in time, this year.
The Vernal Equinox is considered the
beginning of the New Year on Mars (the time of the Vernal Equinox in
the Northern Hemisphere of Mars, beginning Mars Year 35) . As Mars is
much further from the Sun than Earth, the Martian year is 686.98
Earth days long. After March 23, the next Martian Vernal Equinox /
New Year's Day will occur on 2021 February 7; the previous New Year on Mars began on 2017 May 4.
As the Martian orbit around the Sun is more lopsided than the orbit of Earth, the speed Mars moves in its orbit varies quite a bit, depending on how close to the Sun Mars is at the time. Mars is further from the Sun during the Spring season in the Northern Hemisphere than the Autumn Season. Hence, Mars moves more slowly in its orbit during Spring resulting in the Spring season in the Northern Hemisphere (length: 194 Mars days) being much longer than the Autumn season (length: 142 Mars days). While a day on Earth measures 24 hours, a day on Mars is just a little longer: 24 hours, 39 minutes, 35 seconds.
As the Martian orbit around the Sun is more lopsided than the orbit of Earth, the speed Mars moves in its orbit varies quite a bit, depending on how close to the Sun Mars is at the time. Mars is further from the Sun during the Spring season in the Northern Hemisphere than the Autumn Season. Hence, Mars moves more slowly in its orbit during Spring resulting in the Spring season in the Northern Hemisphere (length: 194 Mars days) being much longer than the Autumn season (length: 142 Mars days). While a day on Earth measures 24 hours, a day on Mars is just a little longer: 24 hours, 39 minutes, 35 seconds.
Once again this year, the small borough
of Mars, Pennsylvania (about 25 miles / 40 kilometers north of
Pittsburgh) will be celebrating the Martian New Year this week.
Another So-Called "Super-Moon"
In another coincidence this year,
the March Primary Full Moon phase of Earth's Moon occurs a few hours
after the Vernal Equinox on Earth: Wednesday Evening, 2019 March 20
at 9:43 p.m. EDT / March 21 at 1:43 UTC. This is the first time since 1981 that a Full Moon and the Vernal Equinox occur on the same day. The Full Moon of March is
known as the Worm Moon.
This year, the March Full Moon is also considered by some as a so-called "Super-Moon." This is due to the fact that the Moon passes the monthly perigee point, or point in lunar orbit closest to the Earth and when the Moon appears largest in our sky for the month, about a day before Full Moon. Lunar Perigee occurred this month on Tuesday Afternoon, 2019 March 19 at 4:00 p.m. EDT /20:00 UTC. The distance between Earth and the Moon, at that time, was 223,306.51495 statute miles / 359,377 kilometers.
This year, the March Full Moon is also considered by some as a so-called "Super-Moon." This is due to the fact that the Moon passes the monthly perigee point, or point in lunar orbit closest to the Earth and when the Moon appears largest in our sky for the month, about a day before Full Moon. Lunar Perigee occurred this month on Tuesday Afternoon, 2019 March 19 at 4:00 p.m. EDT /20:00 UTC. The distance between Earth and the Moon, at that time, was 223,306.51495 statute miles / 359,377 kilometers.
Native Americans also had
other names for the March Full Moon. With the increased cawing of
crows, northern tribes knew the March Full Moon as the Crow Moon.
They also called it the Snow Crust Moon, for the increased crusting
of snow, caused by the thawing of snow by day and the freezing of the
water by night.
The Abenaki tribe (New England and
adjacent areas of Canada) called the March Full Moon “Mozokas” or
the Moose Hunter Moon. The Creek nation, located further south,
called it the “Tasahcusee” or Little Spring Moon. And, the Dakota
Sioux actually called it the “Moon When Eyes Are Sore From Bright
Snow.”
Colonial Americans called the March
Full Moon the Sap Moon, for the time when maple trees were tapped.
They also called it the Lenten Moon, as it was the last Full Moon of
Winter usually occurring during the Christian period of Lent.
Full Moon names for March, in the
Southern Hemisphere, include Harvest Moon and Corn Moon.
Internet Links to Additional Information ---
Vernal Equinox: Link >>> http://scienceworld.wolfram.com/astronomy/VernalEquinox.html
Season of Spring: Link >>> http://en.wikipedia.org/wiki/Spring_%28season%29
Equinox: Link >>> http://en.wikipedia.org/wiki/Equinox
Earth's Seasons: Link >>> http://en.wikipedia.org/wiki/Season
Tilt of a Planet's Axis: Link >>> http://en.wikipedia.org/wiki/Axial_tilt
National Cherry Blossom Festival: Link >>> https://nationalcherryblossomfestival.org/
Mars Vernal Equinox / New Year's Day:
Link >>> http://buhlplanetarium4.tripod.com/astrocalendar/2019.html#marsnewyear
Full Moon: Link >>> http://en.wikipedia.org/wiki/Full_moon
Full Moon names ---
Link 1 >>> http://earthsky.org/astronomy-essentials/full-moon-names
Link 2 >>> https://en.wikipedia.org/wiki/Full_moon#Full_moon_names
Link 3 >>> http://www.farmersalmanac.com/full-moon-names/
Related Blog Post ---
Astronomical Calendar: 2017 May." Monday, 2017 May 1.
Link >>> https://spacewatchtower.blogspot.com/2017/05/astronomical-calendar-2017-may.html
Martian New Year (Vernal Equinox in the Northern Hemisphere of Mars - Mars Year 34) began 2017 May 4.
Source: Glenn A. Walsh Reporting for SpaceWatchtower, a project of Friends of the Zeiss.
Wednesday, 2019 March 20.
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gaw
Glenn A. Walsh - Informal Science Educator & Communicator:
< http://buhlplanetarium2.tripod.com/weblog/spacewatchtower/gaw/ >
Electronic Mail: < gawalsh@planetarium.cc >
Project Director, Friends of the Zeiss: < http://buhlplanetarium.tripod.com/fotz/ >
SpaceWatchtower Editor / Author: < http://spacewatchtower.blogspot.com/ >
Formerly Astronomical Observatory Coordinator & Planetarium Lecturer, original Buhl Planetarium & Institute of Popular Science (a.k.a. Buhl Science Center), Pittsburgh's science & technology museum from 1939 to 1991.
Formerly Trustee of the Andrew Carnegie Free Library and Music Hall, Pittsburgh suburb of Carnegie, Pennsylvania.
Author of History Web Sites on the Internet --
* Buhl Planetarium, Pittsburgh:
< http://www.planetarium.
* Adler Planetarium, Chicago:
< http://adlerplanetarium.
* Astronomer, Educator, Optician John A. Brashear:
< http://johnbrashear.tripod.com >
* Andrew Carnegie & Carnegie Libraries:
< http://www.andrewcarnegie.
