Zoom: From Atoms and Galaxies to Blizzards and Bees: How Everything Moves (23 page)

Add 40 mrem for each medical X-ray you undergo.

Add an astonishing 1,000 to 5,000 mrems for a whole-body CAT scan. Some machines deliver as much as 10,000 mrems. Given the sixty-two million CAT scans performed annually in the United States, this has probably replaced radon as our greatest single radiation source. One CAT scan can give you more radiation than that received by Hiroshima survivors a mile or two from ground zero (about 3,000 mrems, on average). It’s reliably estimated that about 2 percent of cancers in the United States are caused by CAT scan irradiation.

Add 1 mrem if you watch TV on an old-fashioned tube-type set.

Obviously, testing your basement for radon, installing a venting fan if necessary, and asking your doctor if an X-ray might work as well as that CAT scan are the easiest ways to greatly reduce your radiation exposure. Avoiding unnecessary commercial flights could cut down a little bit more. It presents a tangible reason not to visit the in-laws.

Finally, here are the minor sources of radiation that give you less than 1 mrem per year, presented in decreasing order of dosage. These are the things you can truly forget about:

Looking at a computer screen: 0.1 mrem.

Wearing an LCD watch: 0.06 mrem.

Living within fifty miles of a coal-fired power plant: 0.03 mrem. (That’s because coal and soot are slightly radioactive.)

Having two smoke detectors in the house: 0.02 mrem.

Living within fifty miles of a nuclear power plant: 0.009 mrem.

Having luggage X-rayed once: 0.002 mrem.

Going through an airport’s backscatter X-ray scanner: 0.01 mrem.

Can such superlow doses produce any harm at all? The Mayo Clinic, the Health Physics Society, and most epidemiologists believe there’s a threshold below which radiation is as benign as popcorn. Disputing them, some scientists believe that very low doses in the 1 mrem range might create some small effect along the lines of one cancer death per forty million people. Even this minority group of enhanced worriers agrees, however, that the risk involved in having two smoke detectors or living near a nuclear plant is so low that it poses no risk whatsoever (barring an accident, of course).

If radiation concerns you, don’t even think of moving to Mars. Martian colonists might receive enough radiation in two years to destroy 13 percent of their brains. Some say 40 percent.

Radiation and other subatomic particles and photons aren’t the only things flying through us. There is one additional standout that dominates everything else. Indeed, the most abundant thing in the universe—besides light itself—is the neutrino.

Neutrinos are as omnipresent as roaches in Rio. Each second, two trillion neutrinos fly through each of our tongues. Don’t taste a thing? That’s because they rarely meddle with our bodies. Despite their unrelenting, torrential presence, they are utterly harmless.

The existence of the neutrino was predicted eighty years ago to explain odd atomic behavior involving the neutron, whose name it resembles. But don’t confuse them. Neutrons live in the center of all atoms except the most common form of hydrogen. They’re the heaviest stable particles and live forever. Although here’s something weird: if a neutron leaves its atom, it’s toast. It then decays in about eleven minutes.

A loose neutron is a loose cannon that goes poof and turns into a proton and an electron. This detritus arcs away oddly, like defective fireworks, which persuaded Wolfgang Pauli in 1930 that something else must be present, too, something that weighs almost nothing. The mystery item was soon named the neutrino, which means “little neutral one.” A quarter century passed before the existence of the neutrino was finally confirmed. It was a science triumph and a relief, since neutrinos already figured theoretically in the fusion process, which makes the stars shine. The sun’s core releases countless neutrinos that essentially zoom away at the speed of light and do not interact with anything else, at least not in a normal way. Rather, they just pass through everything.

By day, neutrinos from the sun penetrate your head and shoulders and whiz completely through your body and then proceed into and through our planet and out the other side. At night, an equal number invades your body from below and exits through your head, after having flashed through the entire earth in one-twentieth of a second, as if our planet were no more substantive than fog.

The chance that a neutrino will alter even one of your body’s seven octillion atoms anytime this year is one in a million. You need a wall of lead a light-year thick to stop the average neutrino.4

Lately we’ve found that neutrinos are even stranger than we imagined. Credit for this goes to physicist Ray Davis, who first figured out how to count these ghost particles. The apparatus he used is a huge vat of one hundred thousand gallons of dry-cleaning solvent. Davis placed this a mile underground, in the abandoned Homestake gold mine in South Dakota, penetrable only by neutrinos. Even bats can’t get there. He figured a million pounds of perchloroethylene has so many chlorine atoms that a neutrino will occasionally change one to a form of argon. He managed to detect the trace of six neutrinos after four months—that’s how rare it is that a neutrino will bother anyone or anything, even an atom among countless trillions. That was forty years ago. That his brainchild actually worked earned Davis the 2002 Nobel Prize four years before his death.

Neutrinos, which come in three different varieties, change from one form to another as they fly through space. But the bottom line is that they are absolutely everywhere. Your thumbnail is penetrated by a trillion neutrinos every second. But because they do not normally influence ordinary baryonic matter, they do not cause gene mutations and, hence, cancer. They’re like dust mites, our harmless sleeping buddies. But nobody develops allergies to neutrinos.

QUICK GUIDE TO FAST INVISIBLE OBJECTS STRIKING YOU RIGHT NOW

… and whether they’re safe (S), harmful (H), or pose just a slight risk (SR)

Infrared photons S

Ultraviolet photons SR

Electrons S

Cosmic rays SR

Neutrinos S

Muons SR

Dark matter S

Alpha particles (e.g., radon) H*

From a psychological standpoint, neutrinos pave the way for the most recently posited unseen entity: dark matter, our final zooming phantom. This is today’s most mysterious substance.

It’s been obvious since 1933 that there’s six times more material in the universe than all the stars, nebulae, black holes, planets, cheeseburgers, and everything else we can think of combined. This unseen stuff makes the Milky Way spin strangely. It glues together the Local Group of galaxies. Its gravitational pull is powerful. Yet it’s invisible. We call this material dark matter. Each of its particles must be massive.5

Because the universe is definitely filled with “presto chango” neutrinos that barely affect anything, dark matter may simply be a heavier version of these. But because it does not emit or even reflect light, it must have nothing to do with electrons.

I had witnessed astronomers’ obsessions with dark matter that night atop the Chilean mountain. I had watched astrophysicist Barry Madore scrunch his brow while studying a fresh photograph he had taken with the hundred-inch telescope. The galaxy’s features defied logic.

“We still don’t understand these dark matter halos around galaxies,” Madore had muttered to me. “Look at these ragged edges,” he said, tapping a finger on the photograph’s outer section. “What’s doing this? Why is this material flying off into intergalactic space? What’s causing this motion?”

He finally shrugged.

“My educated guess is that it’s dark matter.”

It seems to pervade the universe. It may even lurk, unseen, in the rooms of our homes, in the very air around us. A study conducted in 2012 showed that it is not confined to galaxies but bleeds off into the seemingly empty space between them. It may be everywhere. Another 2012 study revealed them to thickly inhabit the region near the sun and its neighboring stars.

Dark matter is detectable not by its appearance—for it has none—but by what it does to everything near it. Its gravitational attraction glues each galaxy cluster together, keeping its members from wandering their separate ways.

Madore stared at the image again. “But maybe gravity itself acts strangely when it’s far away from whatever it’s tugging on. So maybe there is no dark matter at all. I mean, where’s Occam’s razor here?” he concluded, referring to the principle that the simplest explanation is usually the correct one.

But which is simplest? The idea that gravity behaves weirdly at long distances, a theory called MOND, which is embraced by only a minority of researchers? Or the concept of a bizarre new form of matter? Barry Madore had sighed loudly and asked, “Which do you choose, the improbable or the exotic?”

It’s even possible that these particles attract each other to form invisible structures. Could there be a major parallel universe right here among us?

Most of our bodies and our planet and indeed every atom everywhere is utter emptiness. If the universe were compressed and all its spaces were removed, you could squeeze everything that exists into a ball smaller than a supergiant star, such as Orion’s Betelgeuse. It’s not totally far-fetched that these wide-open spaces in our bodies allow for cohabitation with creatures or objects of some other realm. Perhaps—since we’re now letting ourselves speculate without a shred of supporting evidence—conscious entities whiz through our everyday lives like ghosts, as oblivious to us as we are to them.

Recent studies from 2012 and 2013 that looked at the “halo stars” in our galaxy—those high above the flat plane where the vast majority of suns dwell—show that nothing seems to be tugging them. Yet those locations are just where dark matter was thought to predominate. On the other hand, studies of the motion of galactic clusters—distant large objects—do indeed indicate dark matter’s existence. In short, today’s evidence is bewildering and contradictory. And unlike other zooming entities that continually penetrate our bodies as if we were Swiss cheese, dark matter is undefined: we still can’t say what it is.

Maybe we’re better off not knowing.

And His Battles with the Ephemeral

Noise proves nothing. Often a hen who has merely laid an egg cackles as if she had laid an asteroid.

—MARK TWAIN, FOLLOWING THE EQUATOR (1897)

Breezes, crickets, lava, digestion, spinning moons, diving birds, blowing sand—we’ve mostly explored movement that unfolds in familiar time frames. Stuff we can see, things perceived even before the word science was coined. But starting with the ancient Greeks, long before the era of stop-action photography, observers grew intrigued by ultrafast entities. Like the beating of hummingbird wings 1,250 times a minute, these events were not mysterious so much as fast to the point of invisible.

People knew of them by the things they left behind. Perhaps there was a whine, as of mosquito wings, or a shadowy blur to mark the lower terminus of an intriguing action too swift to see.1

This unperceived universe was captivating from the get-go because it involved speed, prized by many cultures as a desirable attribute in people and animals. The very fastest actual animal in any of the constellations the Greeks identified—as opposed to mythological animals, such as Pegasus, the flying horse—was the big dog, Canis Major, whose hastening legs, according to legend, won his epic race against the fox, supposedly the world’s swiftest animal. That victory was enough for Zeus to immortalize the dog in the heavens. (In a real foxes-versus-dogs derby, the result would be close to a photo finish; they’ve respectively been clocked at forty-two and forty-four miles per hour.)2

Blurry legs and wings and other whizzing things intrigued Renaissance scientists. Several desperately tried to study this invisible realm of speed. By rapidly waving fingers in front of their eyes, some created a crude “stop-action” strobe effect that could actually reveal a hummingbird’s wings in flight, even though they flapped twenty times a second. If you try this in front of a spinning fan and vary your hand-waving rate until it works perfectly, you’ll actually be able to freeze the blur and see individual blades clearly.3

More sophisticated techniques finally started uncovering nature’s high-speed secrets in the late nineteenth century. To this day, one person alone remains famous for making such invisible motion decipherable. He was the bearded mastermind now known as Eadweard Muybridge.

Muybridge’s 1878 sequence of photographs of a galloping horse, shown as a repeating loop, is the most famous “movie” of the nineteenth century. By “slowing down” previously too-fast-to-perceive action, it settled a longtime debate about how horses run, a nagging issue in the 1870s, when those ubiquitous animals dominated the urban as well as rural landscape.

Born Edward Muggeridge in England, this singular and not always likable character kept changing his name after emigrating to San Francisco in 1855, at the age of twenty-five. He started calling himself Muygridge, later changed his first name to Eadweard, and yet signed all his photographs “Helios.” Moreover, when doing photo shoots south of the border he insisted his name was Eduardo Santiago. (His gravestone gives yet another name, Eadweard Maybridge, so even now it’s hard to know what to call him.)

At the start of his career he was a bookseller and an agent for a British publishing company at a time when San Francisco had dozens of bookstores and almost as many photography studios. But his life changed in the summer of 1860, when he embarked on a journey back to England that started out via the southern overland route to New York. The trip ended violently in Texas.

Muybridge suffered severe head injuries in a splintering stagecoach crash that killed one man and badly injured everyone else on board. After spending three months in treatment in Arkansas, he awoke to remember nothing of his earlier life: his memory began anew at this point.

Muybridge continued treatment—for blurred vision—in New York over the course of the following year. He also had permanently impaired senses of taste and smell and exhibited erratic, emotional, and eccentric behavior. A few biographers have since claimed that the apparent damage to his frontal cortex actually freed him from inhibitions and paved the way for the motion-related photography breakthroughs, which ultimately made him famous.