Santa Monica Bay Audubon Blog

This year we report on that other large object in the sky,
known as the sun.

Not a rotting peach, but our Sun – 860,000 miles in diameter, 8 light-minutes away (Alan Friedman ~ 4/22/14, on NASA site)

The second solar event of this calendar year is the Summer Solstice, scheduled in Los Angeles for June 20, 2017 at 9:24 PM PDT (or 21 June 0424 UTC – Universal Time Coordinated, if you prefer; also known as Greenwich Meridian Time in Ye Merrie Olde Angleland).  The sun rises at 5:42 AM at 16° north of due east, daylight will last 14 hours, 25 minutes, 20 seconds (14:25:20); the sun sets at 8:08 PM at 29° north of due west, and combined nighttime (pre-dawn + post-sunset) is 9 hours, 34 minutes, 40 seconds (9:34:40).

Daylight on June 20 is two seconds longer than on June 19, and less than one second shorter than on June 21. Anywhere within the Arctic Circle on June solstice day, the sun is above the horizon continuously for 24 hours. This is the longest day of the year and the first day of Summer in the northern hemisphere; conversely in the southern hemisphere it is the shortest day of the year and the first day of Winter. That’s not an accident. Our seasons are due entirely to the tilt of the earth’s axis.

                            UPCOMING TOTAL SOLAR ECLIPSE AUGUST 21, 2017
Our final comment on this eclipse. See the total eclipse if you can. Get yourself onto ‘centerline’ to maximize the viewing time. Northern Oregon is the area closest to Southern California. If you’re planning on settling for a partial eclipse, don’t bother. The difference between even 99% partial and 100% total is – literally and metaphorically – the difference between night and day. The human eye is the only instrument that can simultaneously capture all the visible effects, and no photograph can duplicate the beauty and awe of the experience. That’s all, folks.

Why does the Earth Tilt?  Opinions vary, no one knows for sure. Take your own best guess. Here are some conjectures. When the solar system condensed out of a gaseous nebula, condensation occurred unevenly. During the early phase, solid bodies were both growing in size and moving less orderly than today; collisions resulted. The tilt may have resulted from a large collision, an event which may have simultaneously created our moon. Other conjectures: No-longer-existing planet Thea whacked the earth, creating the moon and tilting the earth. Unbalanced gnawing on the earth’s core by large blind mole rats caused it to wobble. The earth doesn’t tilt – the rest of the universe is off-kilter.

Tilt of earth at northern summer solstice (Timeanddate.com)

Distance From the Sun
As described above, it’s the Earth’s axial tilt that causes our winter and summer, not the Earth’s distance from the sun. In face, the earth reaches Aphelion – it’s farthest point from the sun – on July 3rd. Perhelion – it’s closest point to the sun – is six months later, on January 2nd, 2018.

Definition of the terms (from Online Etymology Dictionary.com)
Summer: “hot season of the year,” Old English sumor “summer,” from Proto-Germanic *sumur- (source also of Old Saxon, Old Norse, Old High German sumar, Old Frisian sumur, Middle Dutch somer, Dutch zomer, German sommer), from Proto-Indo-European (PIE) root *sem- (2) “summer” (source also of Sanskrit sama “season, half-year,” Avestan hama “in summer,” Armenian amarn “summer,” Old Irish sam, Old Welsh ham, Welsh haf “summer”).
Solstice: Mid-13th century., from Old French solstice, from Latin solstitium “point at which the sun seems to stand still,” especially the summer solstice, from sol “the sun” (from PIE root *sawel- “the sun”) + past participle stem of sistere “stand still, take a stand; to set, place, cause to stand,” from PIE root *si-st-, reduplicated form of root *sta- “to stand, make or be firm.” In early use, Englished as sunstead (late Old English sunstede). First used in English around 1250.

Seasonal Fluctuation
The atmosphere, land and oceans all buffer the earth’s temperature, thus the coldest and warmest times follow the winter and summer solstices, respectively, rather than falling on those days. Just as with people coming from a frigid lake or hot bath, it takes time for solid bodies to warm up or cool down.

Eastern Sunrise, Western Sunset
Throughout the northern winter and spring, the points of sunrise and sunset move farther and farther north.  The extremes are the Winter Solstice (around December 21), when the sun rises and sets farthest to the south, and the Summer Solstice (around June 21) when they are farthest to the north.  The equinoxes mark the halfway point, when sunrise and sunset are exactly east and west.

Summer Festivals
The farther one lives from the equator, the more noticeable are seasonal variations in daylight and warmth, and the more important seasonal events such as midsummer festivals become. Most summer festivals are linked to recognition of the growing length of day.

Mesopotamia and Babylonian area (arhat media.com)

Who First Figured This Out?
Setting aside China, India and the Americas for this discussion, it was in the Middle East, in what is now Syria, Iraq and Persia, that humans began to systematically study movements of stars, planets and seasonal changes. Not only for curiosity’s sake, but to determine times of rainfall, planting, harvesting and cold, they began gathering real data: where the sun rose and set, that sunrise and sunset points move, that such points periodically slow in their movement and reverse course. The easiest way to do this was to create a large circle, mark regular divisions on the circle, as closely spaced as possible, and lay it down where you can see the entire horizon. This essentially is what the Celts did with huge stones at Stonehenge.

Sumerian Astronomy
I think the Sumerians figured it out as follows: 1) Build a platform from which you can see the entire horizon (not too difficult in a flat desert) and build a low, circular wall on it. 2) Find the exact center of the circle, then lay out two marks on the wall-top opposite each other. 3) Continue halving the wall-top space to get circle-quarters, then circle-eighths, etc. 4) You may eventually arrive at 360 as a nice workable total for such evenly spaced marks; lots of marks but not too closely-spaced to be practical. 5) Sit on your stool at the exact center of the circle with you eye level with the wall-top and watch the distant horizon. 6) When the sun rises and sets, put a little pebble at that mark on the top of the wall. 7) At some point, days or months later, there will be too many pebbles, so you’ll have to number your marks somehow so you can remove the pebbles. 8) To number them you’ll have to select one mark as a logical starting point. 9) By now you should have noticed that everything in the sky continually moves except for one particular star (which we currently call Polaris or the north star). 10) Use the mark on the wall that lines up with that unmoving star as your starting point, and number all the other marks from there around the circle. Does it matter in which direction you number? Probably not. You now have a working device for determining sunrises and sunsets and so on; all you need do is write your data down on something. In a few  years, you’ve got it pretty well figured out: length of year, solstices, equinoxes, months. Add some star groups as signposts through which move the sun and planets (Greek planasthai for “to wander”), and you have the zodiacal constellations (Aries, Taurus, etc.).

An astrolabe. Enlarge it, lay it down flat, and you get an idea of how to locate sunrises. (iWeb.TNtech.edu)

Festival Lag Time
It takes a few days to confirm that a solstice has indeed occurred. According to this chart, by four days after the solstice the daylight period has grown by only 17 seconds. This is about the minimum difference one could detect with primitive instruments. So the early Mesopotamian scientists (astronomers, or at that time, astrologers) would notify their people that the solstice had occurred, the day had indeed begun to shorten, the great darkness will indeed return (“Winter is coming!”) and the folk must gird their loins and prepare themselves. This was a Necessary Thing to Know, and a cause for celebration. Thus, solstice festivals didn’t necessarily fall on the solstice itself, but often on the day one could surely detect that the solstice had successfully re-occurred. Western European Christmas celebration – four days after the winter solstice – is the best-known example.

Summer Festivals
The farther one lives from the equator, the more noticeable are seasonal variations in daylight and warmth, and the more important seasonal events such as midsummer festivals become. Most summer festivals are linked to recognition of the growing length of day.

Stonehenge
Some historians point to the Stonehenge, a prehistoric monument in Wiltshire, England as evidence of the fact that ancient humans used the June Solstice as a way to organize their calendars. Some believe that Stonehenge’s unique stone circle was erected around 2500 BCE in order to establish the date of the Summer Solstice. Viewed from its center, the Sun rises at a particular point on the horizon on day of the June Solstice. Thousands of people, including modern-day druids and pagans, usually gather at Stonehenge for this occasion.

North America
Some Native American tribes held ritual dances to honor the sun. The Sioux were known to hold one of the most spectacular rituals. Preparations for the event included cutting and raising a tree that would be considered a visible connection between the heavens and Earth, and setting up teepees in a circle to represent the cosmos. Participants abstained from food and drink during the dance itself. Their bodies were decorated in the symbolic colors of red (sunset), blue (sky), yellow (lightning), white (light), and black (night).

China
In ancient China, the summer solstice was observed by a ceremony to celebrate the Earth, femininity, and the “yin” forces. It complemented the Winter Solstice that celebrated the heavens, masculinity and “yang” forces. According to Chinese tradition, the shortest shadow is found on the day of the Summer Solstice.

Western Europe
In ancient Gaul, which encompasses modern-day France and some parts of its neighboring countries, the Midsummer celebration was called Feast of Epona. The celebration was named after a mare goddess who personified fertility and protected horses. In ancient Germanic, Slav and Celtic tribes, pagans celebrated Midsummer with bonfires. After Christianity spread in Europe and other parts of the world, many pagan customs were incorporated into the Christian religion. In parts of Scandinavia, the Midsummer celebration continued but was observed around the time of St John’s Day, on June 24, to honor St John the Baptist instead of the pagan gods.

Northern European Midsummer Celebrations
In northern European countries like Sweden, Denmark, Norway and Finland, Midsummer is a festive celebration. When the summer days are at their longest, and in the far north it is the time of the Midnight Sun, festivals generally celebrate the summer and the fertility of the Earth. In Sweden and many parts of Finland people dance around Maypoles. Bonfires are lit and homes are decorated with flower garlands, greenery, and tree branches.
[Chuck Almdale]

Interesting Links
TimeandDate.com – June Solstice
TimeandDate.com – Los Angeles sunrise, sunset & day length for June 2017
TimeandDate.com – Perihelion, Aphelion and the Solstices
Heliophysics – A Universal Science
Los Angeles Equinoxes and solstices from 2010–2020