Giz Explains: Where Dust Bunnies Come From

I first met my terrible dust bunny, cowering under a soon-to-be replaced video card. It was 2003. Since then, he has puffed around in my periphery, a dusty daemon on my figurative shoulder. And in my literal apartments.

I threw him out with the fritzy Radeon, and vowed to properly clean my computer case from then on. So he migrated.

From the left rear corner of my gaming computer, he hitched to the corner of my college dorm, behind the TV and out of sight. In my first apartment, he grew bolder and more proudly disgusting; I caught him twice next to the bathroom door. In apartments with strict cleaning rotas, he went into hiding, but could usually find the foot of a bedpost, or a closet corner, or a heavy appliance to hide near. Just last month, I found him in the middle of the hall, sitting static at the hardwood nexus of filth. It wasn't clear if he'd come from a bedroom, from underneath the nearby fridge, or if he'd rolled a few more feet, tumbleweed-style, from the bathroom. Didn't matter. He was back, he was gross, and nearly a decade later, I still had no idea where he had come from, or how he had formed.

What is Dust?

Let's set aside the bunny for a second, and focus on the filth. Dust is everywhere. Fine sand is rock dust. Rubber, brakepad and pavement particles are road dust. Fine ash can be volcanic dust. Hell, Carl Sagan famously and repeatedly referred to Earth as a "mote of dust," albeit in a cosmic sense. But the dust we're talking about, dust bunny dust, is a specific thing, with a specific recipe. And a studied one! According to David W. Layton and Paloma I. Beamer, who coauthored a report called ‘Migration of Contaminated Soil and Airborne Particulates to Indoor Dust,' typical household dust in a midwestern home is comprised of the following:

Indoor dust is a mixture of soil tracked into a residence, particulate matter derived from ambient outdoor air, and importantly, organic matter inputs from various sources. A prominent feature of indoor dust is its organic material content, with levels of about 40 wt % in residential housing.

Soil, pollen and airborne dirt particles were to be expected and account for over half of dust's weight. Makes sense! Outside is full of dirt, and every time we return to our homes, we bring some of that back.

So, doctors Layton and Beamer, what about that other 40 per cent. The "organic matter", as you call it:

lint, skin particles, organic fibers, food debris, etc.

That other 40 per cent is you: your food, your skin, your hair and your clothes' lint. Or maybe your dog's! But mostly just yours, you disgusting, shedding beast.

The closer you look, the worse it gets. For a feature in a 1986 issue of Discover Magazine (via the Straight Dish), Penny Moser took samples of dust from her home to a lab, where she took a look at a couple of them through a microscope:

Pathologist Charles McLeod moved his eye over the prepared slide containing my dust ball... "Here`s part of an insect," he said, "either a chitinous shield or a body fragment. Here's a human hair." It was mine. I could tell because I periodically give myself a henna rinse, and under the microscope the hair showed bursts of Raging Raspberry or Autumn Copper slapped onto mouse brown.

We came across an Alternaria mold spore, which looked like a segmented sweet potato, and a roundworm egg, which I didn't want to know much more about. On this slide, as on all the slides, there were many tiny blue and pink fibers. "They're natural fibers," McLeod said. "You can tell by the flat, irregular shape. In your neighbor's radiator dust we have a synthetic blue fibre. Probably from something like a pair of blue pantyhose." The radiator dust also had a ghastly looking thing that resembled chicken feet, but was just a tiny hair cluster from the bottom of a leaf. From under the stove we found boric-acid crystals — a cockroach prophylactic — and some yeast. There were also cat hairs, pollen and more pink and blue fibers.

Insect parts, hair, mold, worm eggs, unidentifiable fibers, pantyhose thread, leaf hair, yeast and roach poison. And that was the least worrying of the samples. From under her bed:

The tiny toenail fragment didn't bother me and the mold spores I could live with - but not the horrible hairy thing that looked like a lobster claw. "That's the limb of something that's been dismembered," McLeod said matter-of-factly. It wasn't a minute before he found a whole one. "I've never seen anything quite like this," he said. "It seems to have mouth parts on its feet and gill-like devices." It was to me, without a doubt, the ugliest thing I had ever seen. It looked like an angry rhinoceros with crustacean appendages.

This turned out to be a dust mite, an exceedingly common, invisible-to-the-naked-eye creature that lives in most of our homes, feeding off the skin that we constantly shed.

Every one of these ingredients, however, is dead. Whether it's an insect corpse, a disembodied hair, or flakes of epidermis, it's all dead. Dead dust has no will, no intentions. So why does it clump as if it does?

The origin of dust bunnies, the universe and everything

Dust is just dust. It's not readily evident why little tiny particles of one thing or another would clump together, and even less obvious how all these flecks and specks and grains come to behave in seemingly consistent ways: forming in corners, or edges; appearing in clusters; preferring life indoors instead of out. Albeit a crude and basic one, dust bunnies are a system, and systems have to emerge from somewhere, by some mechanism.

Make that mechanisms, plural. Dust begins to bunnify by doing what dust does best: settling. But because dust is made of so many different materials, it settles in lots of different ways. Hair, large skin scales and visible dirt are positioned mostly by predictable forces, like air from a vent (particles may settle in the small eddie, or vortex, near a vent opening) or my physical movement (which is why dust bunnies often appear behind doors—they've been swept there). Smaller particles tend to remain airborne for long periods of time, dropping at rates of just a foot an hour for sub-micron dust particles.

These smaller particles can be led to surprising locales, propelled by unnoticeable, super-subtle airflows. As still as your house's atmosphere may feel, it's in constant movement. Your breathing, your appliance's exhaust, and your heating and cooling systems are sources of flow, the direction and patterns of which are rarely observed, except through the dust bunnies they help create.

But airflows and walking paths and the like can only tell us where dust bunnies will be; they don't tell us why they form. For that, we turn to cosmology.

A popular theory about the formation of our solar system, and others, for that matter, is that many of the early bodies of the galaxy just sort of... clumped up. Says Richard Cowen, in his book, ‘History of Life':

Dust particles collide softly and tend to stick together by electrostatic and gravitational attraction in a process called accretion. Around a new star, the dust bunnies can build up and compact into substantial solid masses a kilometer or so in diameter. Computer models show that in only a few million years, several thousand bodies the size of large asteroids will coalesce into larger units that we now see as planets.

This same principle is generally applicable to household dust, says Cowen, whose theory is echoed by astrophysicist luminary Neil deGrasse Tyson: "[Accretion]explains the origin of dust bunnies under your couch."

With much respect for our astrophysical inclined friends, in the gravity-bound context of a home, the tiny amounts of static electricity present in motes of dust are only useful for explaining why fine particles stick together. It takes a stronger bond to hold one of those mouse-like nests of refuse together. Baylor University physics professor Lorin Matthews told Esquire last year, "The forces that hold the dust bunnies together can be the entangled fibers themselves. They get matted, much like lint or felt."

Once all those larger skin, hair and insect particles meet, in other words, they just get their hooks into one another, and don't let go. This might seem unlikely from our macro, human perspective, but a glance through even a low-power microscope will show the constituent parts of a typical dust bunny to be much gnarlier, and therefore much more prone to snarling to one another, than they seem from Up Here.

There are other minor culprits, like the cooking of fatty foods, which produces triglycerides that can attach to dust particles, making them stickier. All the causes, though, share one characteristic: they're subtle. It's either electrostatic forces that are nearly impossible to measure, or airflows that are impossible to feel, or fat deposits that are an unavoidable and unnoticeable byproduct of preparing basically any delicious food.

Actually, make that two characteristics: without dust, they can't exist. So get cleaning.

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