The greatest nature writer, Henry David Thoreau, enunciated many startling insights in his 1854 masterpiece, Walden; Or, Life in the Woods. One of his most advanced ideas is in the penultimate chapter, Spring, where he describes rivulets of wet sand and clay that run down a steep railroad cut when the ground begins to thaw. He studied the cut, which ranged from 20 to 40 feet high, while walking between his cabin beside Walden Pond and his home village of Concord, Mass.
“The material was sand of every degree of fineness and of various rich colors, commonly mixed with a little clay. When the frost comes out in the spring, and even in a thawing day in the winter, the sand begins to flow down the slopes like lava, sometimes bursting out through the snow and overflowing it where no sand was to be seen before. Innumerable little streams overlap and interlace with one another, exhibiting a sort of hybrid product, which obeys half way the law of currents, and half way that of vegetation.”
The flows take the form of thick leaves or vines, making sprays a foot or more deep that are shaped like lichens or coral or leopard paws or bird feet, and brains and lungs, excrement, stalactites. At the bottom of the cut they flatten and run together, “still variously and beautifully shaded, but in which you can trace the original forms of vegetation. …”
The sand formations were “an anticipation of the vegetable leaf. No wonder that the earth expresses itself outwardly in leaves, it so labors with the idea inwardly. The atoms have already learned this law, and are pregnant by it. … The feathers and wings of birds are still drier and thinner leaves.”
This may be the way blood vessels are formed, Thoreau says. “If you look closely you observe that first there pushes forward from the thawing mass a stream of softened sand with a drop-like point, like the ball of the finger, feeling its way slowly and blindly downward, until at last with more heat and moisture, as the sun gets higher, the most fluid portion, in its effort to obey the law to which the most inert also yields, separates from the latter and forms for itself a meandering channel or artery within that …. ” He sees these forms repeated and expanded in the human hand, lip, mouth, nose. “The chin is a still larger drop, the confluent dripping of the face….
“Thus it seems that this one hillside illustrate the principle of all the operations of Nature. The Maker of this earth but patented a leaf. … There is nothing inorganic. …” Thoreau wrote.
“The earth is not a mere fragment of dead history, stratum upon stratum like the leaves of a book, to be studied by geologists and antiquaries chiefly, but living poetry like the leaves of a tree, which precede flowers and fruit, — not a fossil earth, but a living earth; compared with whose great central life all animal and vegetable life is merely parasitic. … You may melt your metals and cast them into the most beautiful moulds you can; they will never excite me like the forms which this molten earth flows out into. And not only it, but the institutions upon it are plastic like clay in the hands of the potter.”
Which brings us to galaxy M74, which was shaped by the laws of Nature, the hands of the Potter, into what is termed a “grand design” spiral galaxy. The galaxy is around 32 million light-years away in the constellation Pisces.
[Two images of M74 that I made Oct. 9 while a guest of astronomers Jerry and Cindy Foote near Kanab. The above view, with color data, is not as sharp as the view below, which I made with luminosity only. Dark skies and warm friendships made the visit one of my happiest times with a telescope]
Late in 2007, NASA released a Hubble Space Telescope photo of it, noting, “Messier 74, also called NGC 628, is a stunning example of a ‘grand design’ spiral galaxy that is viewed by Earth observers nearly face-on. Its perfectly symmetrical spiral arms emanate from the central nucleus and are dotted with clusters of young blue stars and glowing pink regions of ionized hydrogen. …”
M74 is the largest member of a group of about six galaxies. With an estimated100 billion stars, NASA added, it’s slightly smaller than our Milky Way. The Milky Way’s diameter is around 100,000 light-years, while the central bulge is 1,000 light-years deep.
Galaxies are classified into three main types: spirals, at least half and possibly two-thirds of which have central bars; ellipticals, which are gigantic disks; and irregular galaxies, which are shapeless blobs. Each is what has been termed an “island universe,” many have supermassive black holes at the center; most boast many billions of stars, and nebulas, dust clouds, primordial debris disks, comets, planets and (I believe) civilizations.
Extremely long exposures made by the Hubble Space Telescope show that spirals were more common in the distant past, implying that when spiral galaxies merge they may become ellipticals.
But how did spirals evolve? Most of these galaxies have bar formations at their centers; recently, new research shows that some spiral galaxies not classified as barred spirals actually do have bars sticking out from the central bulge even if they are hard to spot.
No obvious bar shows up in views of M74, but astronomer Marc S. Seigar reported a “weak oval distortion” at the center (an Astronomy & Astrophysics manuscript available online). At the time of the study, 2002, Seigar was with the University of Hawaii, Hilo; today he is as assistant professor in the Department of Physics & Astronomy, University of Arkansas, Little Rock. The title of the paper: “Is Messier 74 a barred spiral galaxy? Near-infrared imaging of M74.”
A leading theory is that density waves, or higher pressure regions, propagate from the center of a spiral, causing stars to line up along the waves’ ridges. The density waves may be caused by rotation of the central bulge and its bar, by an uneven halo of matter around the galaxy, and/or by interactions with other galaxies.
Another idea is that the spiral design is related to pressures from supernova explosions among older-generation stars. Possibly several effects contribute to the formation of spirals.
Spiral structures are common in nature, from the shape of the DNA molecules in all earthly life to water going down a drain, hurricanes and nautilus shells; underlying natural laws, whatever they are, operate at the level of tiny molecules in the cells of our bodies to that of the grand designs of galaxies.
This is the point Thoreau was groping toward, an idea that was incredibly advanced for 1854. The laws of the universe, or the Potter’s hands, have formed our entire mysterious universe. But of course he couldn’t point to which laws, exactly, were involved. More than a century and a half later, there is a great deal that we still don’t know.
As Thoreau said in another passage in Walden, “The universe is wider than our views of it.”