What got me started on dust?
The little subject suggested itself rather forcefully. A few years ago I was on assignment in Mongolia's Gobi Desert, writing about a dinosaur expedition. The pink-orange clouds of dust that billowed over the desert floor were impossible to ignore. The whirling specks invaded my eyes and nose. They infiltrated the pages of my books. They invaded the depths of my sleeping bag.
I had thought this rambling dust was just a local phenomenon. So I was immediately intrigued when expedition geologist David Loope told me that a thin veil of dust flows high across the sky, enveloping the entire planet. As we stood by a sandstone cliff, squinting against the ever-swirling grit, Loope explained how dust helped to create the Gobi's fabulous fossils. Raindrops form on these high-flying dusts, he said. The falling rain drags down the dust, and that dust works a dark magic inside a sand dune.
Consider the larger implications of this: Worldwide, how many raindrops fall from the sky on any given day? And each raindrop contains a piece of dust. So how many specks must there be in the sky? Where do they all come from?
Another of our expedition mates warned me that I'd be digging Gobi dust out of my ears for six months after I left the desert. But some of the dust seems to have penetrated even more deeply. Back at home I discovered I had dust on the brain. When I look up at the sky, I search for a glimmer of that ubiquitous veil. When a raindrop pelts my arm, I stare at the splattered water, wondering what sort of speck brought this drop together. When I wipe my computer screen, I peer through a magnifying glass at the sparkly, fuzzy stuff caught among the sharp ridges of my fingerprint. Too small to distinguish are the individual fragments of a disintegrating world: the skin flakes, rock flecks, tree bark, bicycle paint, lampshade fibers, ant legs, sweater wool, brick shards, tire rubber, hamburger soot, and bacteria. The world is in a constant state of disintegration.
This invisible dust isn't as harmless as it may appear. It can be a heartless little brute. In -ologies ranging from climatology to immunology, scientists are now calling dust onto the carpet. It is a central suspect in the mystery of how the planet's climate is shifting. Billions of tons of it take to the sky each year, and this surely alters the behavior of the Earth's atmosphere. And dust is taking new heat for killing lots of people—not just miners, sandblasters, and asbestos workers, but thousands, maybe millions, of ordinary people who simply live and breathe in dusty air. Although our bodies evolved to screen out most natural dusts, it seems that our lungs are vulnerable to the smaller, industrial-size specks. Dust's relationship to asthma is another topic now coming to a boil. Traditionally, scientists thought the asthma epidemic might be caused by various house dusts. But new, jaw-dropping evidence suggests that asthma may be caused by too little house dust.
By necessity dust scholars are a creative bunch. Scientists who study elephants are spared much of the difficulty of locating a specimen. But a dust scientist must often invent a device simply to acquire the minuscule object of his or her curiosity. One woman created an underwater vacuum cleaner to collect her space dust from the bottom of a well. A fellow who studies the dust of the last ice age isolates his tiny samples of dust from glacial ice cores. And catching dust is only half the battle: both the handling and the analysis of dust are complicated by its dainty girth. The latter scientist rounds up his flighty grains with cling-wrapped fingers.
Since the day I stood in the Gobi Desert and contemplated the population of dust in the sky, I've come to see the air as a medium and dust as the message. Dust delivers the world news: the Rocky Mountains are eroding, and a volcano is erupting in the Philippines. It carries the local headlines, too: the neighborhood coffee roaster is burning the beans, and traffic is heavy on the turnpike. And it brings us the social pages, the news about human activity, for we are dusty creatures.
One purpose of this book is to help readers learn to decipher some of the messages that drift in the air. Our planet sometimes seems too enormous to really comprehend. But perhaps tuning in to the news bulletins issued by some of the planet's smallest reporters can give us a better sense of how things are going for the whole.
Second, I'd be honored if I were able to introduce the reader to his own, personal dusts. Never mind that each of us is constantly enveloped in a haze of our own skin flakes and disintegrating clothing. In addition to that cloud, each match we strike, each light-switch we flick, and each mile we drive causes more dust to rise into the air. Taken in global quantities, our personal puffs of dust have planet-size consequences.
When the fragmenting skin of the Earth rises, both at nature's urging and our own, it changes the weather, and even the climate. When it settles, this dust alters the seas and the soils and the delicate linings of our own lungs. In tiny things there is huge magic and colossal mayhem.
A few notes on jargon:
• Temperatures will be given in Fahrenheit.
• The subject of size is covered in Chapter I. But for ease of reference, here is
a sampling of small things:
One inch: 25,000 microns
A period: In this font 300 microns
Sand: 63 microns and larger
Dust: 63 microns and smaller *
Human hair: 100 microns **
Pollen: 10-100 microns
Cement dust: 3-100 microns
Fungal spores: 1-5 microns
Bacteria: 0.2-15 microns
Fresh Stardust: 0.1 microns
Various smokes: 0.01-1 microns
Tobacco smoke: 0.01-.5 microns
• `Sulfur beads.` Many scientists have cautioned me against including
what I call sulfur beads in my broad definition of dust. The objection is
understandable: When sulfur gases from a coal fire or an erupting vol
cano condense into little clumps in the sky, the clumps are often liquid,
because they quickly draw water from the atmosphere around them. But
in dry air, sulfur does indeed form dry particles. In fact, a single sulfur par
ticle can gather or lose water as it travels through the sky, turning from
liquid to solid and back again. To scientists, these changeable little items
are `aerosols.` But since this is not a technical book, I can't see the harm
in including them in the dust family.
* Technically, what I call dust a geologist would divide into `silt` and `clay.` Some geologists draw the sand/silt line at 63 mictons, others at 60 or even 50. Most agree that `clay` is smaller than 4 microns.
** This varies widely from person to person.