How to Watch the Un-sunlike Sun: Solar Eclipse Tips from Pioneering Astronomer Maria Mitchell
By Maria Popova
Rarely does the dated phrase “heavenly bodies” come more vibrantly alive than in the event of a solar eclipse, when the Moon passes in front of the Sun from the vantage point of our planet and leaves our earthy hearts astir with awe for a few fleeting moments of transcendent presence with “the heavens” and their majestic motion. But to observe a solar eclipse is itself an art, one to which pioneering astronomer and reconstructionist Maria Mitchell (August 1, 1818–June 28, 1889) — the first woman admitted into the American Academy of Arts and Sciences and the first woman hired by the United States federal government for a “specialized nondomestic skill” in her highly mathematically rigorous job as “computer of Venus” — was particularly privy.
In Maria Mitchell: Life, Letters and Journals (public library | free ebook) — which also gave us the story of her trailblazing comet discovery and her timeless reflections on education and women in science, work and life, and science, religion, and our conquest of truth — Mitchell recounts with her characteristic blend of good-natured wit and wisdom her experience of observing the total solar eclipse of July 29, 1878, for which she traveled to Denver with some of her former Vassar students, the first academically accredited women astronomers in America.
In the eclipse of this year, the dark shadow fell first on the United States thirty-eight degrees west of Washington, and moved towards the south-east, a circle of darkness one hundred and sixteen miles in diameter; circle overlapping circle of darkness until it could be mapped down like a belt.
Looking along this dark strip on the map, each astronomer selected his bit of darkness on which to locate the light of science.
But for the distance from the large cities of the country, Colorado seemed to be a most favorable part of the shadow; it was little subject to storms, and reputed to be enjoyable in climate and abundant in hospitality.
My party chose Denver, Col. I had a friend who lived in Denver, and she was visiting me. I sought her at once, and with fear and trembling asked, ‘Have you a bit of land behind your house in Denver where I could put up a small telescope?’ ‘Six hundred miles,’ was the laconic reply!
I felt that the hospitality of the Rocky mountains was at my feet. Space and time are so unconnected! For an observation which would last two minutes forty seconds, I was offered six hundred miles, after a journey of thousands.
Mitchell goes on to extract from the experience some practical advice on the art-science of such heavenly observation:
Persons who observe an eclipse of the sun always try to do the impossible. They seem to consider it a solemn duty to see the first contact of sun and moon. The moon, when seen in the daytime, looks like a small faint cloud; as it approaches the sun it becomes wholly unseen; and an observer tries to see when this unseen object touches the glowing disc of the sun.
When we look at any other object than the sun, we stimulate our vision. A good observer will remain in the dark for a short time before he makes a delicate observation on a faint star, and will then throw a cap over his head to keep out strong lights.
When we look at the sun, we at once try to deaden its light. We protect our eyes by dark glasses—the less of sunlight we can get the better. We calculate exactly at what point the moon will touch the sun, and we watch that point only. The exact second by the chronometer when the figure of the moon touches that of the sun, is always noted. It is not only valuable for the determination of longitude, but it is a check on our knowledge of the moon’s motions. Therefore, we try for the impossible.
She goes on to describe the specific process of her team’s observation — one made all the more impressive by the fact that these were all women scientists in an age when the science education of girls was practically nonexistent:
One of our party, a young lady from California, was placed at the chronometer. She was to count aloud the seconds, to which the three others were to listen. Two others, one a young woman from Missouri, who brought with her a fine telescope, and another from Ohio, besides myself, stood at the three telescopes. A fourth, from Illinois, was stationed to watch general effects, and one special artist, pencil in hand, to sketch views.
Absolute silence was imposed upon the whole party a few minutes before each phenomenon.
Of course we began full a minute too soon, and the constrained position was irksome enough, for even time is relative, and the minute of suspense is longer than the hour of satisfaction. [Footnote: As the computed time for the first contact drew near, the breath of the counter grew short, and the seconds were almost gasped and threatened to become inaudible, when Miss Mitchell, without moving her eye from the tube of the telescope, took up the counting, and continued until the young lady recovered herself, which she did immediately.]
What followed was a singular blend of rigorous precision and the kind of transcendence in which Carl Sagan found the spirituality of science. Mitchell writes:
The moon, so white in the sky, becomes densely black when it is closely ranging with the sun, and it shows itself as a black notch on the burning disc when the eclipse begins.
As totality approached, all again took their positions. The corona, which is the ‘glory’ seen around the sun, was visible at least thirteen minutes before totality; each of the party took a look at this, and then all was silent, only the count, on and on, of the young woman at the chronometer. When totality came, even that ceased.
How still it was!
As the last rays of sunlight disappeared, the corona burst out all around the sun, so intensely bright near the sun that the eye could scarcely bear it; extending less dazzlingly bright around the sun for the space of about half the sun’s diameter, and in some directions sending off streamers for millions of miles.
It was now quick work. Each observer at the telescopes gave a furtive glance at the un-sunlike sun, moved the dark eye-piece from the instrument, replaced it by a more powerful white glass, and prepared to see all that could be seen in two minutes forty seconds. They must note the shape of the corona, its color, its seeming substance, and they must look all around the sun for the ‘interior planet.’
But Mitchell’s most prescient and timeless reflection in observing the eclipse speaks poetically to the spirit of today’s “citizen science”:
It is always difficult to teach the man of the people that natural phenomena belong as much to him as to scientific people.
UPDATE: Find more of Maria Mitchell, her unusual life, and her far-reaching legacy, in my book Figuring.
Published November 1, 2013