The Homely Truth About the Shortest Day

We passed the shortest day of the year last week. It’s the annual drama of encroaching darkness turning to growing light, the grand rebirth, the celestial, uplifting reminder that in any sphere of life, the gloom gives way to brightness.

I’ve always imagined the event as accompanied by an elegant symmetry. I thought that the darkness closed in evenly from both sides, that the sun rose a little later each morning and set a little earlier until the shortest day on December 21st, when the process neatly reversed at both ends of the day. The sequence, I thought, between early December and early January had the shape of a tall hourglass. The left “sunrise” side sloped in to the right during most of December and the right “sunset” side sloped left, each changing by a minute or two each day. On December 21st, they met at the narrow waist and reversed direction.

scienceblogs.com

scienceblogs.com

Well, it doesn’t work that way. Changes in sunrise and sunset times aren’t in synch. The sun doesn’t neatly rise later each morning until the 21st and then reverse course. It keeps rising later and later well beyond the 21st, past Christmas and into the first week of January. Imagine the left side of the hourglass sloping down and right until it’s well below the waist.

The timing of sunsets changes in the opposite way. Sunsets change direction, from happening earlier to happening later, about a week before the shortest day. Imagine the right side of the hour glass sloping inward not all the way down to the waist but only part way. Such an hourglass would have a weird, uneven tube descending from the upper left to lower right. It isn’t until early January that both sides would be moving apart from each other again.

The shortest day is the shortest only because the speed of the changes in the times of rising and setting vary from day to day. In early December, the sun rises later by a sizable couple of minutes every day, while sunset drags on at almost the same time, so the length of daylight shrinks until the 21st. After that, the changes in sunrise slow way down while it is sunset’s turn to pick up the pace, getting rapidly later (by about 7 minutes between the 21st and New Year’s Eve in New York) and lengthening the day.

So the shortest day grows out of a ragged process, not the aligned and symmetrical one we thought we were seeing. The universe spins in ways that we don’t or can’t grasp in detail, but we pull the meanings that we need from our approximations anyway.

 

The Spiritual and the Sentimental

The word sentimental doesn’t get good press. “Having or arousing feelings of tenderness, sadness, or nostalgia, typically in an exaggerated and self-indulgent way” is how the usual definitions run. “Exaggerated and self-indulgent” emotion does sound pretty unwholesome. But I see no reason to disdain tenderness, sadness, and nostalgia, and I think they even have a place in religious feeling as well.

Unlike emotions with more voltage like anger or joy, sentimentality about a person, a place, a pet, a song or even a smell amounts to a quiet but vivid sense of the thing itself and how fleeting it is or was. I am sentimental about people I’ve known in the past but also about those I feel close to today. I’m being sentimental about them whenever I stop for a moment to take a mental snapshot of them, in the hope that doing so will hold them from fading away. The old saw about taking time to smell the roses is sentimental for the same reason.

Sentimentality is about the fleeting nature of things, ultimately about the swift passage of life itself, about stepping into the river that never stops moving. It can also be about merging. The desire to hold on to a moment or a memory can shape itself into a craving to lose oneself in it. The object of nostalgia may be a mother or father or other figure from childhood, but it may also be a god, nature, the cosmos, eternity, or mystery itself. Sentimentality and spirituality overlap here.

I’m not saying that spirituality is sentimental, nor that sentimentality is spiritual. I’m sensing, though, that some of my spiritual moments and my sentimental ones have a thread of emotion in common. They both mourn the frailty of worldly things in time. We are always in the present moment, which thus is a constant, but the past is no such thing.

Genesis for Non-Theists

Creation narratives are lively stories.  In the Bible, God creates the universe and earth in six days. In other traditions, creatures are dismembered, huge eggs hatch, birds create land. Even science’s own creation narrative starts with a Bang and once earth takes shape, the first organic molecules appear relatively quickly, within a billion years. 
 
But at that point the scientific story of life slows way down. Life remains at the stage of single cells for the next two billion years. What was happening to our smallest, oldest ancestors all that time? Why did it take so long to move beyond the stage of one-only? Was evolution on hold?
timeline

From “Oldest bacteria fossils” to “Multi-cellular eukaryotes” 2 billion years later, life on earth was single-celled.
(vector-clip-art.com)

What took so long was the creation of the building blocks for being alive. It’s a creation story with parallels to the first chapters of Genesis. Here’s the biblical sequence: plant life emerges on the third day, including “fruit trees bearing fruit in which is their seed,” followed over the next three days by creatures of the water, air, and land, including man and woman. A few verses later we read about the Garden of Eden and, symbolically, the beginnings of sex and death.

Here briefly is science’s version: life evolved from the simplest cells to cells with a nucleus that enclosed the protected “seed” of DNA. This change set in motion the end of one kind of immortality, the beginnings of sex and death, and the emergence of a new immortality.

The process was slow because the changes were huge.

LUCA
Like the Bible, science has a name for our first ancestor. LUCA, our “last universal common ancestor,” was a single-celled organism, a kind of bacterium, from which all life on earth is descended. Inside LUCA was a floating coil of DNA, sections of which have been passed down to every living thing.
Prokaryote

Our common ancestor, a cell with DNA but no nucleus
(shmoop.com)

LUCA reproduced simply by dividing, with one set of genes in each new cell. The new cells were identical, a long line of Adam clones without an Eve.

LUCA’s membrane enclosed only watery liquid and the genes. Gradually LUCA’s descendants “ate” and absorbed other bacteria. Some of these bacteria turned into the nucleus of the cell that absorbed them. They became the container for the cell’s genes. Such cells advanced from  prokaryotes (before a nucleus) to eukaryotes (a true nucleus, and pronounced “you carry oats”). The nucleus was a seed, a seed that provided the DNA with a chemical environment of its own and helped grow more complex DNA and much larger cells.
Sex, Death…
cell

Cells get a nucleus–and more.
(biogeonerd.blogspot.com)

Early cells were, in their own way, immortal. The genes in both prokaryotes and early eukaryotes would reproduce and then the cell would split into two identical cells, as bacteria still do. Did such cells die? Eventually, but only from accident or the environment. In this Eden, cells did not get older. They became their own offspring and could theoretically live forever.

Eukaryotes, however, found a new way to reproduce. One would rub up against another eukaryote and portions of their DNA sets would be inserted into the other—the original sex act. With this exchange of DNA, genetic variation sped up, at last. So did natural selection.
 
In the next step, sex became specialized. As some early organisms became multi-celled, such as algae, they reproduced not by division of the whole parent organism but, as with us, by means of specialized germ cells (not the disease kind of germ but the creative kind, as in the “germ of an idea”).
No longer was the parent reincarnated in a clone, as in bacteria. It was left behind, and it aged and died. As in Genesis, the co-mingling of different living things brought sex and death. Cellular life moved beyond Eden.
 
…and Immortality
So we have lost the immortality that the prokaryotes enjoyed. But we have found it in another, more complex form. Our immortality runs through the genetic line of our children and other blood  relatives. It turns out that it is not the body, the soma, that is the crucial package. It is the germ cells that carry the DNA forward. 
 
But is this an adequate and satisfying idea for us humans who dream of living forever? Is the continuity of DNA a meaningful form of immortality? Here is one answer from Harvard biology professor George Wald, in his 1970 lecture on “The Origins of Death.”
 
We already have immortality, but in the wrong place. We have it in the germ plasm; we want it in the soma, in the body. We have fallen in love with the body. That’s that thing that looks back at us from the mirror. That’s the repository of that lovely identity that you keep chasing all your life. And as for that potentially immortal germ plasm, where that is one hundred years, one thousand years, ten thousand years hence, hardly interests us.
 
I used to think that way, too, but I don’t any longer. You see, every creature alive on the earth today represents an unbroken line of life that stretches back to the first primitive organisms to appear on this planet; that is about three billion years. That really is immortality. For if the line of life had ever been broken, how could we be here? All that time, our germ plasm has been living the life of those single celled creatures, the protozoa, reproducing by simple division, and occasionally going through the process of syngamy — the fusion of two cells to form one — in the act of sexual reproduction. All that time, that germ plasm has been making bodies and casting them off in the act of dying. If the germ plasm wants to swim in the ocean, it makes itself a fish; if the germ plasm wants to fly in the air, it makes itself a bird. If it wants to go to Harvard, it makes itself a man. The strangest thing of all is that the germ plasm that we carry around within us has done all those things. …
I, too, used to think that we had our immortality in the wrong place, but I don’t think so any longer. I think it’s in the right place. I think that is the only kind of immortality worth having — and we have it.