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Nightfall is a magic time. As the blue sky of day settles into a navy blue and then blue-black of night, the curtain of heaven rises, showing stars, planets, and the Milky Way straddling the sky. With its promise of peace and repose, night beckons us, whether we are astronomers, poets, painters, or just people enjoying an evening stroll. It courted poets like Thomas Gray, whose words, written in the 1740s, can turn a simple scene of a darkening sky into one of the most heartfelt images in the English language:
The curfew tolls the knell of parting day,
The lowing herd wind slowly o'er the lea,
The plowman homeward plods his weary way,
And leaves the world to darkness, and to me.
Now fades the glimmering landscape on the sight,
And all the air a solemn stillness holds,
Save where the beetle wheels his droning flight,
And drowsy tinklings lull the distant folds;
Save that from yonder ivy-mantled tower
The moping owl does to the moon complain
Of such, as wand'ring near her secret bower
Molest her ancient solitary reign.
One hundred forty years after Gray wrote these words, Vincent Van Gogh was also struck by the magnificence of night. His resulting astronomical art is brilliant almost beyond description. He painted a nightfall that including the Moon, and probably Venus and Mercury, in Road with Cypress and Star. Two of his works of art have "Starry Night" in their titles. The earlier one, completedin the autumn of 1888, was Starry Night over the River Rhône. Although the landscape is viewed to the southwest, the seven stars of the Big Dipper are clearly portrayed as seen to the north; artistic license won out over scientific accuracy, but the pleasing result shows the bowl of the dipper seemingly gathering water from the river.
Then there is Starry Night, one of the most celebrated works of art in existence. I have heard that the stars Van Gogh depicts variously refer to Venus and the Moon, which were in the morning sky at the end of June 1889, the month he painted it. More intriguing than the stars and Moon, however, are the swirls of hazy starlight that cross the sky over the town. On a first look, these swirls, and the stars that they surround and cross, seem to be ordinary stars seen through the eyes of someone intoxicated or extremely nearsighted. The artist, however, might have had much more in mind. To understand this, we need to travel in space and in time from St. Rémy, where the artist lived and saw the stars he painted, to 1850 and the town of Birr, Ireland, where amateur astronomer Lord Rosse was observing through the world's largest telescope, a reflector with a mirror seven feet wide.
With the mirror end on the ground, the mighty telescope's long bulky tube was slung with ropes between two large brick walls. Using a staircase to reaching his eyepiece, Rosse observed and drew all kinds of celestial objects, from fields of stars to those misty blobs of cloudy light called nebulae. Like other astronomers of his day, Rosse could only speculate as to what these spiral-shaped nebulae might be; solar systems in the process of formation was the most popular idea.
Messier 51, the Whirlpool, was one of these objects. Located just south of the Big Dipper's handle, this distant maelstrom was discovered on October 13, 1773, by the famous French comet discoverer Charles Messier and listed as No. 51 in his catalogue of objects that could be mistaken for comets. At the time, Messier 51 was thought to be a solar system in formation. In 1903, V. M. Slipher, an astronomer at Lowell Observatory in Flagstaff, Arizona, took a series of long exposure photographs of several of these spiral nebulae. Using the slow films of the time, Slipher had to spend as much as two full nights exposing his glass plate to gather enough light to obtain a spectrum of a single nebula. The results were uniformly strange: all the spectra of the spiral nebulae, when compared to the spectrum of our Sun, were shifted toward the red end of the spectrum. Slipher did not know why this should happen, as planets in formation around Sun-like stars should have spectra similar to that of the Sun. It was not until 1924 that Edwin Hubble solved the mystery. Using the great 100-inch telescope atop Mt. Wilson, he and Milton Humason took photographs that were sharp enough to resolve these hazy spots into huge emporiums of stars.
Messier 51 is now known to be a vast spiral galaxy some fifteen million light years away. Informally called the Whirlpool Galaxy, M51 is fifty thousand light years across, and, rather than one Sun about to have planets, this galaxy shines with the intensity of ten billion suns. It can be spotted as a diffuse patch of light through small telescopes, but through large telescopes the vastness of the spiral structure is spectacular.
Some years ago Wendee, my wife, and I explored the details of M51 with the sixty-one-inch Kuiper telescope in the Catalina north of Tucson. The galaxy seemed to have no end as it spiraled outward from its center. It was a staggering sight, unchanged from the beauty that Rosse had seen so long ago. It was the first time Wendee actually saw the separate arms unfolding from the galaxy's center, and we were both entranced.
In May of 1889, Vincent Van Gogh entered the asylum of St.-Paul-de-Mausole, located near the French town of St. Rémy. The asylum was caring for only ten male patients at the time, so Van Gogh had the luxury, of two rooms, one for himself and the other as his studio. By the end of May, Van Gogh seemed at peace there, and painted some of the most magnificent of his later landscape paintings. In June he painted Starry Night, "an indisputably visionary painting," writes critic Nathaniel Harris, "in which a huge moon, radiant stars or suns and swirling, wave-like nebulae fill the night sky. A cypress and the entire landscape tremble and move in sympathy; only the little village remains solid and stolid in the turbulent vastness of the universe."
Perhaps, as Hillary Clinton might say, it takes a village to pacify the universe. The village in Van Gogh's painting contains peaceful, sleepy structures outlined with straight lines. With everyone presumably asleep in the village, there seems no relation between it and the sky except for the church, whose straight spire reaches toward the sky. Steeple meets sky in the midst of the outermost nebula, as though it is asking for some clarification on why the sky seems so out of phase. The town of St. Rémy was not a friendly place to Van Gogh: "I fell ill," he said a month after the painting, "from the mere sight of people and things. Starry Night seems to depict its artist's preference for disorder and unbridled energy over the ordered quiet of the village.
In my own college years I went through a period of depression that required hospitalization and a lot of therapy to cure. During those years, during the times I was relaxed enough to appreciate it, the peace and permanence of the night sky offered a sense of stability. "It is now three o'clock in the morning," I wrote on May 22, 1973, my twenty-fifth birthday, "and I have just completed an observing session that couldn't have lasted half an hour, yet turned out to be a fine communion with a part of Nature which I have always loved, but in these last months have ignored. I realize tonight that it does not matter whether I hunt for comets, or obtain magnitude estimates of variable stars, or stay out all night. The good observing session means a private feeling of a successful rendezvous with Vega or Jupiter, as in tonight's case, or Saturn and Sirius and Canopus on another night."
Painting of a Whirlpool
In 1985, Charles Whitney, an astronomer at Harvard, pointed out the similarity of the nebulous swirls to Lord Rosse's famous 1845 drawing of Messier 51. His research complemented that of art historian Albert Boime, who noted that Van Gogh was familiar with the sketch, having studied it, probably, from a copy of Les Etoiles, a book by famous astronomy writer Camille Flammarion that included the Lord Rosse drawing. It is possible that Van Gogh even noticed the book's front page illustration of a church spire pointing to the sky.
When one compares the swirls of Starry Night with Lord Rosse's drawing, they seem to match better if the painting is reversed; the spiral shape in M51 seems counterclockwise, though the artist made it clockwise. He might have felt free to make similar reversals in his Road with Cypress and Star, painted in April 1890. On the evening of April 20, the Moon was in a beautiful grouping with Venus and Mercury; however, if the painting indeed does include these two planets, the grouping is reversed. Weather records studied by Charles Whitney indicate that the evening of April 20 was the first cloud-free night in a week, making it more likely that Van Gogh would have been motivated to go outdoors to paint. Another suggestion: Van Gogh faced eastward, away from the twilight sky, so that whatever daylight was left would have illuminated his canvas. If he then used a mirror to see the Moon and planets, it would have reversed their appearance relative to one another.
None of these details or speculations diminishes the wonder of the artist's communion with the forces of nature. "There is certainly an affinity between a person and his work," Van Gogh told his brother Theo, "but it is not easy to define what that affinity is." For Starry Night, Van Gogh confronts his universe with celestial objects of marked contrast; the sharp, almost violent images of Moon and stars, the silent dagger of the cypress tree, all opposed by the graceful swirls of the Whirlpool.
Flashing across the Sky
Imagine a comet wandering through space like an ancient sailing ship. Rounding the Sun every few hundred thousand years, after a near miss with Jupiter, it changes its path and visits the Sun more frequently. Eventually its elliptical journey is shortened so greatly that it now orbits the Sun every seventy-six years. On one pass, a tiny particle of dust escapes. This particle travels on its own through space, rounding the Sun and occasionally dashing past Earth. Finally, one clear October night this particle, now racing along at some forty miles per second, hurtles through the Earth's atmosphere. In a second it vaporizes to nothing, just as an eight-year-old looks up and watches. The speck of dust has given its 4.5 billion year life to ignite a child's interest in the sky.
We have all seen shooting stars, which are not stars at all but the glowing air surrounding tiny panicles that vaporize in the upper atmosphere of Earth. They look like falling stars, yet after one appears, the number of stars in the sky has not decreased. It is the bright flash of ionizing gases around the particle that we call a meteor. If the particle is larger, say, than the size of a tennis ball, it would hit Earth's atmosphere with a very bright streak. If it is as large as a basketball, it might survive its fall, leaving small pieces to hit the ground. These pieces are called meteorites.
In 1923, American poet Robert Frost published a poem about a small meteorite, a tiny remnant of a body in space, that ended up as part of a wall:
Never tell me that not one star of all That slip from heaven at night and softly fall Has been picked up with stones to build a wall.
Some laborer found one faded and stone cold.
These lines beckon us to envision the intricate relationship among the sky, the Earth, and those who inhabit the Earth. We see a wall that stands as part of a house, or as part of a fence, or as the remains of the ancient Temple in Jerusalem—an artificial wall built with stones and bonding materials for some purpose. All of its stones, while ancient and enduring, have been gathered from some local quarry. But one stone in one wall is different. Traveling through space and hurtling to Earth, this rock, with so much to tell, has simply taken its place as one of many to hold up a wall, an ignominious end for such a noble stone.
Meteors are such simple parts of nature, and yet so wonderful, so mysterious; their beauty transcends their brevity, and they have captured the pens of earlier poets. In the fifteenth century John Donne began a song about explaining wonderful things:
Goe, and catche a falling starre,
Get with child a mandrake roote,
Tell me, where all past yeares are,
Or who cleft the Devil's foot.
Teach me to heare Mermaides singing,
Or to keep off envies stinging,
Serves to advance an honest minde.
Two hundred years later Byron pondered:
When the moon is on the wave,
And the glow-worm in the grass,
And the meteor on the grave,
And the wisp on the morass;
When the falling stars are shooting,
And the answer'd owls are hooting,
And the silent leaves are still
In the shadow of the hill
Shall my soul be upon thine,
With a power and with a sign.
Although these references to meteors appear almost incidental, they seem to share the notion that there is something momentous in the fall of matter from the sky. Robert Southey wrote at the start of the 19th century in "St. Antidius, the Pope and the Devil".
He ran against a shooting star,
So fast for fear did he sail,
And he singed the beard of the Bishop
Against a comet's tail;
And he passed between the horns of the moon,
With Antidius on his back;
And there was an eclipse that night,
Which was not in the Almanac.
The Moon as a marker of time and space is one of my favorite images, a picture often conjured in English poetry. It is Robert Frost's natural timepiece: Frost referred to the Moon as a "luminary clock" that "proclaimed the time was neither wrong nor right."
Here the Moon appears in Coleridge's "Rime of the Ancient Mariner":
The moving Moon went up the sky,
And no where did abide:
Softly she was going up,
And a star or two beside—
Although most of us never realize it, the Moon does keep its own time, rising thirty minutes to an hour later each night. On fully half the nights of the month, the Moon either rises so early that it is visible during the afternoon, or so late that it stays in the sky until late in the morning. Hopkins noted this in his 1862 piece "A fragment of anything you like"
Fair, but of fairness as a vision dream'd; Dry were her sad eyes that would fain have stream'd; She stood before a light not hers, and seem'd
The lorn Moon, pale with piteous dismay Who rising late had miss'd her painful way In wandering until broad light of day;
Then was discorver'd in the pathless sky White-faced, as one in sad assay to fly Who asks not life but only place to die.
The appearance of the Moon—not just its timing, but its shape, and its effect on clouds and landscape has also long been a poetic image of choice. Whether the Moon is in the sky at night is a question that interests poets and painters as well as astronomers. A moonlit night welcomes peaceful evening walks that are less inviting when the night sky is dark. However, it is only during the four days nearest full Moon when moonlight makes a very noticeable difference—only two and a half days before full Moon the sky is only half as bright. Thomas Gray could turn the absence of moonlight into a profound sense of loss, as seen in this passage from a journal Gray kept of a tour through English Lakes:
At distance heard the murmur of many waterfalls not audible in the day-time. Wish'd for the Moon, but she was dark to me & silent, hid in her vacant interlunar cave.
Gray quoted the last six words in this passage from Milton's Samson Agonistes. The blind Samson says:
The Sun to me is dark
And silent as the Moon,
When she deserts the night,
Hid in her vacant interlunar cave.
When the Moon shines through high cirrus clouds, it often surrounds itself with a halo of light.
Samuel Taylor Coleridge wrote:
The Moon, rushing onward through the coursing clouds, advances like an indignant warrior through a fleeing army; but the amber halo in which he moves—O! It is a circle of Hope. for what she leaves behind her has not lost its radiance as it is melting away into oblivion, while, still, the other semicircle catches the rich light at her approach, and heralds her ongress.
Gerard Manley Hopkins wrote often of haloes, like this lunar one of February 1872:
The halo was not quite round, for in the first place it was a little pulled and drawn below, by the refraction of the lower air perhaps, but what is more it fell in on the nether left hand side to rhyme the moon itself; which was not quite at full. I could not but strongly feel in my fancy the odd instress of this, the moon leaning on her side, as if fallen back, in the cheerful light floor within the ring, after with magical rightness and success tracing round her the ring the steady copy of her own outline.
Whenever the Moon's phase is thin enough, we can see the dark part as well as the bright. This effect, called earthshine, results from the Earth's shining on the Moon's dark side. Anyone standing on the dark part of the Moon at such a time would behold a sky brightly lit by the Earth. Here at home, earthshine is not to be feared, despite this poor sailor's feeling in "The Ballad of Sir Patrick Spence":
Late, late yestreen I saw the new moone
Wi' the auld moone in her arme;
And I feir, I feir, my deir master,
That we will com to harme.
Nor can a star appear within the dark section of the Moon, notwithstanding this bad omen from Coleridge's "Rime of the Ancient Mariner":
We listened and looked sideways up!
Fear at my heart, as at a cup,
My lifeblood seemed to sip!
The stars were dim, and thick the night,
The steersman's face by his lamp gleamed white:
From the sails the dew did drip—
Till clomb above the eastern bar
The hornèd Moon, with one bright star
Within the nether tip.
The Moon has an aspect that stands beyond time, though, or at least beyond the length of time we can imagine: the story of its cratered surface we see through binoculars or a telescope. While here on Earth we live in areas surrounded by local rocks of a span of ages, a single look at the Moon gives the whole panorama of its 4.5 billion year history. The Moon was probably created as the result of a shotgun marriage between two great worlds, the Earth and another large body with which it collided more than four billion years ago. So violent was the crash that the Earth's crust melted away, and a storm of rocky material from the Earth and the other world formed a thick ring around the Earth. Eventually that material congealed to form the Moon. And if the Moon was born in violence, it has lived its life that way, too. Even without a telescope or binoculars, anyone can see the large grey areas that form the face of what some perceive as "the man in the Moon." Some of these areas are impact basins, formed when objects struck the Moon in an ancient blitz that took place some 3.9 billion years ago. Much later these basins filled with dark basalt, a lava that gives them their dark appearance Finally, through a telescope, one can see hundreds of small craters, all formed when asteroids or comets struck the Moon throughout its history. One of the youngest major craters on the Moon, Tycho, was formed when a comet or an asteroid struck the Moon some 100 million years ago. When the Moon is near its full phase, one can see the rays of rocky material that pan out from the center of that impact site, marking this relatively recent change in the Moon's long history.
Think'st thou I'd make a life of jealousy;
To follow still the changes of the moon
With fresh suspicions? No; to be once in doubt
Is once to be resolved. Shakespeare, Othello
|Preface: Come, Gentle Night||17|
|Ch. 2||Stars, Hide Your Fires||62|
|Ch. 3||A Changing Universe||78|
|Ch. 4||Ring Out, Wild Bells||98|
|Ch. 5||A Poem and a Comet||121|
|Ch. 6||Dark Sky from Walden Pond||142|
|Ch. 7||A Terrible Beauty is Born: When Science Becomes Poetry||159|
|List of Illustrations||197|