Here Comes the Sun!

Father Sun, Tata Huriata, Purépecha symbol painted in
16th century Franciscan chapel in Tzintzuntzan, Michoacán
Photo: Reed

Today I want to write about the Sun. Like other agrarian societies around the world, Mesoamerica's original peoples relied on their knowledge of the Sun's path across the heavens to mark the seasonal changes that cued them when to perform specific tasks, such as when to plant and harvest; when to lay in winter supplies, etc.

If it weren't for Reed's insatiable curiosity about the heavens, it's unlikely that I would even be paying attention. Since he was asked to explain, more or less patiently, the concepts multiple times before I finally understood them, this post is lovingly, gratefully, dedicated to him.

Tonight we went out for dinner at a Chinese Buffet in our neighborhood, which was remarkably good. At dinner, we were casually chatting. I believe I may have thanked him for his help, which prompted this reply:

Reed's Reflection: "It's really about getting back in touch with a natural process that we moderns have mostly lost. People once told time by the Sun. Now we may note Sunrise and Sunset, but instead of checking the Sun's position we look at our watches."

Reed isn't an Eagle Scout for nothing! It's going to be fun watching him induct our physically and mentally active, extraordinarily curious grandson into all these natural processes. But I digress.

Back to Basics

Three of the most significant imaginary lines running across the Earth's surface are the Equator, the Tropic of Cancer, and the Tropic of Capricorn.

The Equator is the longest line of latitude on the Earth, i.e., where the Earth is widest in an east-west direction. The Equator is also where:

• Day and night are equal every day of the year—day is always twelve hours long, and night is always twelve hours long, but the Sun is
• Directly overhead at noon on the two Equinoxes—near March 21 and September 21.

At 23.5 degrees North, the Tropic of Cancer is where the Sun is directly overhead at noon on the June 21 Solstice (longest day of the year in Northern Hemisphere). The Tropic of Capricorn (23.5 degrees South of the Equator) is where the Sun is directly overhead at noon on December 21, Solstice (longest day of the year in the Southern Hemisphere).

Egghead Note: The word solstice is derived from the Latin sol (sun) and sistere (to stand still), because at the solstices, the Sun stands still in declination; that is, the seasonal movement of the Sun's path (as seen from Earth) comes to a stop before reversing direction.

Keep in mind that the Equinoxes occur when the Sun is directly over the Equator; and night and day are more or less equal (12 hrs: 12 hrs) around the world (March 21 and September 21). Perhaps even more significantly, the Equinoxes represent the moment when the Sun passes over the Equator from Northern to Southern Hemisphere, or vice versa; thus, it can be observed that the Equinoxes herald important seasonal changes. "The Tropics" are defined as the area bounded by the:

• Tropic of Cancer, which passes just north of Havana, Cuba, and runs slightly north of Mexico's mid-section out the the southern tip of Baja California before heading out across the Pacific Ocean; and the 
• Tropic of Capricorn, which passes through Chile, Argentina, Paraguay, Brazil) in the south. 

Tropic of Cancer runs just north of Havana, Cuba, then across
Mexico to the southern tip of Baja California. Mexico City is the
Red Dot in the middle of the country surrounded by the
State of Mexico (turquoise, horseshoe-shaped). (CLICK to Enlarge)

The Tropic of Cancer is marked on one of Mexico's federal highways. Because of a slight annual progression in the tilt of the Earth's axis, the Tropic of Cancer actually shifts slightly every year. Signposts in the photo document this shift from 2005-2010.

Zaragoza-Victoria Federal Highway 83 (Vía Corta) at Kilometer 27+800.
This is the only place on a Mexican Federal Highway where the
Tropic of Cancer is marked with absolute precision, and where the
annual drift (2005-2010) is also precisely marked.

The seasons of the Northern and Southern Hemispheres are mirror images of each other, which means that:

• June 21 Solstice is: 

• Summer Solstice (longest day) in the Northern Hemisphere; and 

• Winter Solstice (shortest day) in the Southern Hemisphere.

• December 21 Solstice is:

• Winter Solstice (shortest day) in the Northern Hemisphere; and 

• Summer Solstice (longest day) in the Southern Hemisphere.

These solar effects are most pronounced at the Arctic and Antarctic circles. For example, 

• March 21 Equinox at: 

• Arctic Circle ('North Pole') marks the approach of six months of near continuous daylight, while at the

• Antarctic Circle ('South Pole') marks the approach of six months of near continuous darkness.

• September 21 Equinox at:

• Arctic Circle marks the beginning of six months of near continuous darkness, while 

• Antarctic Circle marks six months of near daylight.

Mexico City

At 19 degrees 26 minutes north of the Equator, Mexico City is just 4 degrees south of the Tropic of Cancer, which means that the Sun is directly over Mexico City twice: once on May 17 (heading north) before the Summer Solstice then again on July 25 after the Solstice, as the Sun begins its return trip south.

Egghead Note #2: Reed researched the local dates of the two zeniths: May 17 and July 25 over Mexico City, then he added, "We have to remember these dates, so next May 17 we can take a picture to show absolutely no shadow." 

A mere heartbeat later, he asked, "Do you remember in Pátzcuaro how I took the candlestick outside to our patio and waited for its shadow to disappear? The candlestick was so thin that it was perfect ... like a Sun Dial."

Then this: "Do you remember my telling you about the guy in Connecticut who made Sun Dials calibrated to the specific location of the property where it was to be installed?" 

Quiet for a moment, he then added thoughtfully, "I don't know how a Sun Dial would be made for Mexico, since the Sun's path is so far North at this time of year...." 

I am writing this post on August 6th. Yesterday we were out in the noonday sun enjoying Mexico City's Historic Center. Waiting for a light, Reed suddenly noticed that we were pretty much standing on our own shadows.

August 4, 2013: Standing on my own shadow.
(Photo: Reed)

Because the Sun is always high in the sky, clearly differentiated seasons aren't characteristic of "The Tropics". Temperature differences instead depend on altitude. At sea level, it's very hot and humid. In the mountains, such as here in Mexico City at 7,000 feet, the climate is generally quite temperate. Hence the popular saying,

"It's always spring in Mexico City."

Tracking Sunrise From Our Balcony

At the time of the Equinoxes, the Sun rises due East and sets due West. But what is peculiar to us transplanted Northerners is that as the Sun continues its Northerly path after the Vernal Equinox, not only does it rise more and more to the North, but it stays in the North throughout the day—a distinctly disorienting sensation.

This sunrise photo was taken on June 25, five days after the Summer Solstice [June 20, 2013]. The billboard at the right marks Due East; that is, the Sun rises behind the billboard at both Equinoxes.

June 25: Sun rises behind the tree in North,
5 Days After Summer Solstice (June 20, 2013).

Here's another photo—this one was taken more recently, on December 18, 2017, three days before Winter Solstice. Just visible is the outline of the chain of volcanoes that form the reclining body of Iztaccíhuatl, Sleeping Woman. The sun is coming up south of her feet.

December 18, 2017: Sun rises over Paso de Cortés.
Coyoacán, Mexico City

Around the World: Fiestas Occur on Seasonal Markers

In all parts of the world, original peoples have celebrated the solstices and equinoxes that marked the changing seasons. For millenia, festivals have fallen on or around these four seasonal markers; for example:

• Christmas (Winter Solstice);
• Easter (Vernal-Spring Equinox on Jewish Lunar Calendar);
• Midsummer (Summer Solstice celebrated in Scandinavian countries);
• Rosh Hoshonna and Yom Kippur (Autumnal-Fall Equinox on Jewish Lunar Calendar).

The halfway points between Solstice and Equinox have also traditionally been celebrated; for example:

• Candlearia (Presentation of Jesus in the Temple Forty Days After His Birth) on February 2, which is also the date of the Purhépecha and Aztec New Year (Candlearia in Mexico City);
• May Day (England) at Midpoint between Vernal Equinox and Summer Solstice;
• Cruz Verde (Green, or Holy Cross) on May 2-3, which coincides with the planting season in Mexico just ahead of the rains; and
• All Saints and All Souls Days celebrated at Mid-Fall, November 1-2, also Dia de los Muertos, which was probably originally celebrated in mid-August before it was moved to coincide with the Catholic Liturgical Calendar.

Still Curious?

Mexico's original peoples were remarkable astronomers, capable of aligning pyramids and other buildings with the Sun's position at key solar moments. Several of Jenny's Posts describe these phenomena, for example:

• Mesoamerican God-Kings as City Planners.
• Xochicalco's Engineers and Scientists (Morelos): Twice each year on May 14/15 and July 28/29, the sun reaches its zenith, directly overhead; at these astronomical mid-days, a very strong ray of sunlight passes through the narrow chimney shaft in the ceiling of the observatory to the cave's floor (see vivid photos), and religious ceremonies were held in the cave to mark this solar event.
• Tlaxcala State: Cacaxtla Presents Cultural Puzzle: The pyramid at Cacaxtla is so positioned that on September 29 (local Equinox), from the pyramid's highest level, the sun would be observed to rise directly from the crater of the Matlacuéitl volcano; that is, from the mouth of the goddess of vegetation.
• Teotihuacán I: 'City Where the Gods Are Made' describes how the Great Stairway of the Pyramid of the Sun faces a westerly point on the horizon where the Pleides constellation appears directly in front of it. In late May, before sunrise on the day the sun passes its zenith, the Pleides makes its first annual appearance above the horizon at Teotihuacán. It is believed that this appearance cued the ruling elites to begin organizing the people for the annual agricultural season. 
• Teotihuacan II: The Shape of Time and Space describes how the urban design incorporates what became known as the Mesoamerican cosmovision.

On the Yucatán Peninsula at Chichén Itzá, the Pyramid of Kukulkán (Plumed Serpent of the Maya) is so constructed and oriented to the Sun that at the Equinoxes (March and September), the play of sunlight and shade creates seven triangles that represent the image of the serpent-god Kukulkán descending to the earth and connecting with its sculpted head at the base of the staircase.

The pyramid is oriented (top to bottom) North-North-East, South-South-West; and East-South-East, West-North-West, which at the Spring and Autumn Equinoxes creates the effect of the serpent-god descending the staircase (over the course of 45 minutes) at Sunset. Bottom left text: Puesta de Sol (Sunset)

For the Maya, the descent and arrival of the serpent-god signified a higher order to begin agricultural activities in advance of the approaching rainy season (March being the month for planting corn in the region).  This 5-minute professional UTube video tours the Pyramid of Kukulkán and shows the image of the serpent "descending" the staircase to connect with to its head of stone resting at the staircase's base.

For more on solstices and eclipses, see:

• The Equator, Hemispheres, Tropic of Cancer, and Tropic of Capricorn;
• Equinoxes;
• World Clock: Day and Night World Map, which gives date, time of solar events around the world.