California rambling: Equal Night

By From page A4 | September 16, 2013

 This Sunday at 1:44 p.m., summer ends. That’s the exact moment when the sun will cross the celestial equator (an imaginary line above the Earth’s equator) from north to south, marking a change of seasons from summer to fall. 

Twice each year — in September and March — the sun shines directly on the equator, causing the length of night and day to be nearly equal. The Romans called this “equal night” or “equinox.” In September, it’s called the autumnal equinox. On any other day, the Earth’s axis tilts a little from or towards the sun, but on the day of an equinox, its axis is directly perpendicular to the sun’s rays.

As the Earth tilts away from the sun, days become shorter. Less light triggers a change in all living things. This progression began on June 21, the longest day of the year. Each day thereafter, even though they became hotter and drier, the days grew slightly shorter.

Progressively less light continues until Dec. 21, tells us, when the sun will reach its most southerly declination of -23.5 degrees. That is when the North Pole will be tilted 23.5 degrees away from the sun during the winter solstice or shortest day of the year. Similar to summer, even though the Earth’s axis will tilt each day a bit more toward the sun, winter will continue to get colder and wetter until March 20 when — you guessed it — the spring equinox will occur and days will become longer.

This cycle has been occurring for millions of years, long before plants, animals or human life existed on Earth.  So, all living things have evolved understanding this pattern and adjusting their lives to it. As a result, the autumnal equinox has influenced many cultural happenings and observances.

Ancient Greek myth associated it with the goddess Persephone who would return to the underworld each autumn to be with her husband, Hades. The Greeks would enact rituals for protection and security while reflecting on their success and failures.

Aboriginal Australians were accomplished astronomers who incorporated the equinox in their oral traditions.  The Chinese celebrate it with the Moon Festival, recognizing the abundance of the harvest by the preparation of sweet mooncakes filled with lotus, sesame seeds, a duck egg or dried fruit.

In Japan, both equinoxes have been national holidays since the Meiji period (1868-1912). Similar to the Greeks, Japanese Buddhists celebrated the spirits of the dead reaching Nirvana on the other shore or “Higan.”  They remember the dead by visiting, cleaning and decorating their graves.

Pagans celebrated Mabon, the second harvest and start of winter preparations. It was a time to respect the coming darkness and give thanks to sunlight. Pagan equinox rituals were carried over into the early Christian church as the Feast of St. Michael and All Angels Day.

Today, there’s little public fascination with the celestial event that creates the season. Hardly anyone associates the sun with harvest festivals, the beginning of crush in the vineyards or Oktoberfest. These things happen because, well, it’s time to have a different type of party.

Who does still notice are the plants and animals. Less light triggers a response in them. Until fall, leaves are green because chlorophyll, a pigment within them, converts the sun’s energy into food for the plant. To do this, chlorophyll absorbs red and blue wavelengths, but not green ones which are reflected back to our eyes.

As days get shorter and temperatures cool, leaves on deciduous trees stop producing chlorophyll. The green color breaks down revealing other pigments that have been hidden within the leaves all along. Carotenoid is the pigment that colors a leaf yellow, orange or brown, appearing after chlorophyll breaks down from lack of sunlight.

Anthocyanin gives cranberries, apples, cherries, strawberries and poison oak their bright red colors. It appears when days are warm and clear and nights cold, but not freezing. Under these conditions, leaves produce sugar though cool temperatures prevent the sugar from flowing through leaf veins, down branches to the trunk. Red anthyocins allow certain plants to recover nutrients in the leaves before they fall.

In the next two weeks, quaking aspen as high as 10,000 feet in elevation will turn from green, to lime, to yellow, to orange to flame red. The earliest, most dependable and spectacular displays are seen up the Bishop Creek Canyon in the Eastern Sierra, west of Bishop, where conditions are best for this color change. From there, the color descends in elevation. A record of this progression is found at where “color spotters” and photographers from across California report what they’ve seen.

Unlike New England, where color descends by latitude, in California it drops by elevation. If you don’t happen to be exactly where the color is peaking in the Northeast, you’ve missed it. In  California, if you miss it at 9,000 feet, it’s peaking at 8,000 feet.

El Dorado County’s best fall color is seen along the southwest shore of Lake Tahoe and in the Hope Valley where groves of lime, yellow and orange quaking aspen will flutter in early to mid-October. Yellow big leaf maple, orange black oak and rose dogwood brighten the forests at from 4,000 to 5,000 feet in elevation from mid to late October. The vineyards of Sierra Foothill wineries will be dressed in yellow, ruby and auburn leaves from late October to mid November. And, through the end of November, exotic and native plants will provide colorful displays along landscaped boulevards in our foothill communities, all because summer ends on Sunday afternoon.

John Poimiroo of El Dorado Hills is a travel writer who specializes in California destinations.

John Poimiroo

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