Artwork credit: Sheenam Das

Spinning a Cosmic Web: It’s Filamentary, My Dear

Susan Mathews

We recently published a personal essay by Vena Kapoor titled “A Natural Dissonance”. In this evocative and lovely essay, she speaks about a messy spider’s web that took shape in front of her. Vena described it as a “gorgeous tent-like structure with a silken platform and various scaffoldings” and called it a “miniature architectural marvel.”

Now imagine a tent woven from silken strands flung far over space, stretching from galaxy to galaxy. It’s not that different from the way our universe is structured. This large-scale arrangement of matter is what astronomers call the ‘cosmic web,’ a vast scaffolding of invisible gas from which galaxies were born, a celestial marvel.

Our universe came into being 13.8 billion years ago and after the massive expansion that followed, dark matter strands intertwined with light over thousands of years. As Paul M. Sutter puts it in his wonderful article, at the start, “the universe was hotter, smaller, and denser than it is now. It was also, on average, much more boring. There wasn’t much variation in density from place to place. Sure, space was much more cramped overall, but in the young universe, no matter where you went, things were pretty much the same.” It sounds familiar. I grew up in small countries and towns, so I know exactly what he is talking about.

But what really started changing the spacescape were tiny, random differences in density. Gas tended to flow into the dark matter nuggets that had a greater gravitational pull. They grew bigger and bigger, and as Sutter points out, the dense patches “grew to become the first stars, galaxies and clusters, while the spaces between them became the great cosmic voids.”

These clusters or halos were formed by a successive set of collapses of primordial clouds of dark matter. The initial collapse led to the cloud assuming a flattened sheet-like configuration, followed by a rapid evolution toward an elongated filament, and then ultimately a dense, compact cluster or halo. It is these clusters that help weave the cosmic tapestry of filaments. The strongest filamentary bridges are those between the richest clusters that stand close together and point in each other’s direction.

Our universe is largely made of dark matter, which is completely invisible to us. It is highly antisocial and simply does not like mingling with light or much else really. However, as Sutter explains, “fortunately, where the dark matter pools, it also drags along some regular matter to join in the fun.”

So, while largely invisible, he says, “like a lighthouse on a distant, black seashore, the stars and galaxies tell us where the hidden dark matter lurks, giving us a ghostly outline of the cosmic web's true structure.” He also says, “… the grandeur of the cosmic web lies in the delicate lines of the filaments themselves. Stretching for millions of light-years, these thin tendrils of galaxies act like great cosmic freeways crossing black voids, connecting bright urban clusters.”

This cosmic tapestry and its web-like structure are not unlike a spider web. In fact, the physical correspondence between the cosmic web and spider webs runs deeper than previously known and this correspondence is a geometric one.

A spider web is a particular type of spatial graph, i.e., with nodes at specified positions, which can be strung up in equilibrium such that all of its strings are tense. In an adhesion model, a cosmic web is a spider web in 2D even if it may not look like the common conception of one. The key mathematical property that characterizes a spiderweb is a perpendicularity property. As Neyrinck et al put it, “Referencing actual arachnid spider webs, gravity is like a haunted-house explorer, clearing strands aside, causing them to adhere and produce thicker strands.”

So, the spider is not just a creator of worlds but also an artist, and geometer. A spider web is also a symbol of a continual weaving of patterns and the infinite possibility of creation.

As Walt Whitman observes in A Noiseless Patient Spider,

“It launch’d forth filament, filament, filament, out of itself,
Ever unreeling them, ever tirelessly speeding them.”

The web-like structure of the universe and weaving metaphors also connect to mythological cosmologies that go back centuries. In Greek mythology, the Moirae (shares) were the three goddesses of fate. Clotho, the spinner, who spun the thread of life; Lachesis, the apportioner of lots who measured it; and Atropos, who cut it short. At the birth of a human, they would appear spinning, measuring and cutting the thread of life.

Pythagoras and Kepler also theorized of the harmony or ‘music of the spheres,’ the theory that each heavenly body in the universe emits its own distinct sound as it travels through space. Plato adopts this in book ten of his Republic. The myth of Er speaks about the structure of the “cosmos as the spindle of Necessity around which all the orbits of the universe turn. On each orbit, a Siren stands singing a single note.” The eight singing Sirens combine to create a wonderful harmony along with the three fates or Moirae, Lachesis who sings of things that were, Clotho who sings of things that are, and Atropos, the things that are yet to be.

In West African folklore, Anansi, which literally translates into ‘spider’ in the Akan language, is a folktale character. Often portrayed as a trickster, Anansi takes the shape of a spider and is one of the most important characters in West African and Caribbean folklore. Transmitted to the Caribbean by way of the transatlantic slave trade, the stories became part of slave resistance and survival. Weaving a different kind of web, he is sometimes considered to be the God of all knowledge of stories.

The cosmic web has also inspired many artistic representations, essentially showing how filaments of galaxies are woven together. For some wonderful examples of this check out The Fabric of the Universe an art and science collaboration undertaken by textile specialist Isaac Facio and astrophysicist Benedikt Diemer, exploring the connection between dark matter and woven textiles.

Tomas Saraceno, an Argentinian artist, and a modern-day Leonardo Da Vinci (right down to his flying machines), has been inspired by cosmic webs and spider webs, leading to room-sized installations. His artwork and research connect disciplines of astrophysics, engineering, environmentalism, thermodynamics, biology, arachnology, and musical composition. In On Air, their experiment attempted to see if they could sense the frequencies of black holes colliding in space, translated through the vibration of a spider’s web. The results are stunning.

The delicate lines of the filaments that comprise the cosmic web remind us that we are an extension of everything that has gone before us. Starting from primordial dark matter, our stories have condensed and cooled like galaxies. Much like the cosmic web, our ancestral threads are largely invisible, leaving faint gossamer clues to our very old beginnings, and giving us signs as to where we might travel.

As evoked in William Faulkner’s Requiem for a Nun, “the past is never dead, it’s not even past. All of us labour in webs spun long before we were born, webs of heredity and environment, of desire and consequence, of history and eternity.”

And thus, we weave our way, tempting cosmic and human fate, hoping to grab hold or land somewhere, following our Siren song.

As Walt Whitman said in A Noiseless Patient Spider,
“And you O my soul where you stand,
Surrounded, detached, in measureless oceans of space,
Ceaselessly musing, venturing, throwing, seeking the spheres to connect them,
Till the bridge you will need be form’d, till the ductile anchor hold,
Till the gossamer thread you fling catch somewhere, O my soul.”