Thursday, June 20, 2013

Summer Begins Friday 1:04 a.m.; Largest Moon of 2013 Sunday

File:North season.jpg

The Earth at the start of the 4 (astronomical) seasons as seen from the north and ignoring the atmosphere (no clouds, no twilight). Front left: Summer Solstice for the Northern Hemisphere. Rear right: Summer Solstice for the Southern Hemisphere. (Image Source: )

By Glenn A. Walsh
Reporting for SpaceWatchtower

The moment of the Summer Solstice, heralded as the beginning of the season of Summer in Earth's Northern Hemisphere (and the season of Winter in the Southern Hemisphere), will be early Friday morning, 2013 June 21, at 1:04 a.m. Eastern Daylight Saving Time (EDT) or 5:04 Coordinated Universal Time (UTC). Two days later mark the largest visible Full Moon of 2013.

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, near the day we now call June 21), the Sun would appear to reach its highest point in the sky for the year. The motion of the Sun's apparent path in the sky (what is known astronomically, today, as the Sun's declination) would cease on this day, before reversing direction.

Today, we know that, while the Sun does have motions, it is actually the motion of the Earth, tilted on its axis 23.44 degrees 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, marks the Summer Solstice in the Northern Hemisphere.

Alternately, the Winter Solstice, in the Northern Hemisphere, occurs when the Earth reaches the point in its orbit when the north polar axis is most directly inclined away the Sun. And, conversely, at this time Summer begins in the planet's Southern Hemisphere.

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. 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.

The Vernal Equinox, when the season of Spring begins in the Northern 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 when the Earth's axis is inclined neither toward nor away from the Sun, between the Summer and Winter Solstices, this is known as the Autumnal Equinox. And, half-way between the beginning points of each season are Cross-Quarter Days, related to the traditional holidays of Groundhog Day, May Day, Lammas Day (traditionally, first harvest festival of the year on August 1), and Halloween Day.

In ancient times, the Summer Solstice was known as Midsummer Day, in earlier calendars celebrated around June 24. 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, the Church began to associate the Midsummer festivals with the Nativity of Saint John the Baptist on June 24. In the Bible, the Gospel of Saint Luke implies that John was born six months before the birth of Jesus, although no specific birth dates are provided.

This year, just a couple days after the Summer Solstice, we will observe the largest Full Moon in 2013. Although some media are referring to this as a "Super Moon," it is not really that unusual and occurs every few years when conditions are favorable.

This year on June 23, the Moon will be at
perigee (closest approach to Earth for the month) at 7:00 a.m. EDT (11:00 UTC). For coastal areas, tides are expected to be higher than normal.

Just 32 minutes later, the Moon reaches the Full Moon phase. This Full Moon phase occurs when the Moon is closest to the Earth, and hence the Moon is seen to be larger in the sky than it normally appears. Although there is a lunar perigee every month, it does not always occur near the Full Moon phase.

The June Full Moon was known to many Native Americans as the Strawberry Moon, as the relatively short season of harvesting strawberries fell in the month of June. In ancient Europe, the June Full Moon was called the Rose Moon.

More on the Summer Solstice -
Link 1 >>>
Link 2 >>>

More on the Season of Summer: Link >>>

More on the history of Midsummer: Link >>>

Summer "Solstice Day" Annual Free-of-Charge Day, 1985 to 1991, at Pittsburgh's original Buhl Planetarium and Institute of Popular Science (a.k.a. Buhl Science Center):

Link >>>

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

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