by Bob Berman
Perhaps worst of all, Ritter took forever to publish anything. After making a discovery or conducting an original experiment—and some were truly exciting and profound—he’d make a brief, cryptic, and vague announcement in some science journal, then wait years before taking the trouble to explain what he’d found. But he would only write about it in his books, where descriptions of his results were tangled up with extraneous stuff about supernatural phenomena. He once confessed that after two months of experiments and discoveries, it took him two years to adequately write it all up.
This was far too slow, especially at a time when science was advancing at an accelerating clip. Ritter was doing important work, but his advances in the study of galvanism and electricity were delayed in reaching Europe’s science community, and even when they did arrive, they were met with skepticism.
All in all, Ritter wrote thirteen volumes about his scientific findings, books that told of several groundbreaking discoveries, including the effects of electricity on animal bodies and, of course, that first-ever dry-cell battery. He also published twenty journal articles. Yet despite all this work he remained generally unknown and failed to land a single teaching appointment. Increasingly in debt, unable to care for his family, and in failing health, he died of pulmonary problems just after his thirty-third birthday.
His is the saddest story of all our invisible light discoverers. For decades after his death, few people had heard of him, especially outside Germany. He remains generally unknown even today. But while Ritter lived and died in obscurity, the ultraviolet light he discovered gained increasing attention. For as the world soon learned, UV is the invisible radiation most intimately involved with human life—and death. Its rays will powerfully influence your health.
CHAPTER 6
Danger Beyond the Violet
When it comes to ultraviolet light’s effect on humans, we are in a bit of a bind: we can’t live without it, but too many unfortunates each year find that they can’t live with it, either.
Ultraviolet light’s power comes from the sawtooth fineness of its waves. Herschel’s infrared pulses are separated by as much as a millimeter—approximately the diameter of a needle. They pulse a trillion times a second. By comparison, ultraviolet waves are just one two-millionths of an inch apart. Their separations are submicroscopic. At least a thousand trillion (one quadrillion) of them flash past you every second. Light with longer wavelengths—such as infrared radiation, microwaves, radio waves, and visible colors—can jostle entire atoms, and they may even be able to slightly heat living tissue, but they are too weak to interfere with atomic structure. The lightning speed of ultraviolet light, on the other hand, gives it the power to strip electrons from atoms. As a result, atoms are broken apart—ionized.
It’s this ionizing power that makes UV light so dangerous. If an atom that’s important to our health—such as any of the atoms that make up our DNA—is ionized, the damage can be lethal, inducing gene and cell mutations that are the precursors to cancer. More than eight thousand people in the United States are killed annually by melanoma (skin cancer), nearly all of which is caused by exactly this process. On the other hand, the vitamin D the body produces when struck by ultraviolet light may be the most potent cancer-preventing substance known. In 2016, a major medical journal announced that UV exposure helps prevent pancreatic cancer.
Just above our atmosphere, 10 percent of the sun’s energy is in the ultraviolet band of the spectrum. But air is so effective at blocking it that fully 77 percent of the UV rays trying to penetrate it fails to reach the earth’s surface. Thus sunshine measured on the ground has a maximum ultraviolet component of just 3 percent. The rest of it consists of 44 percent visible light and 53 percent infrared radiation. Moreover, the intensity of UV radiation at the earth’s surface varies throughout the day (it is greatest when the sun is directly overhead) and with the seasons (it is greatest in summer).
All ultraviolet light is not created equal. Ninety-five percent of the UV light striking us is UVA, the weakest variety and the one with the longest waves—from 3,200 to 4,000 angstroms—some of which is actually visible to the eye as violet. If you let a prism break sunlight into its rainbow spectrum, the most violet-looking color at the extreme fringe, where the color dims a bit before reaching its blank endpoint—that’s UVA. UVA has been scientifically associated with malignant melanoma, but in general it’s the safest variety.
Slightly shorter wavelengths ramp up the danger big-time. If you could actually see the type of UV light whose waves are spaced 3,000 angstroms apart, it would look virtually identical to the UV light whose waves are 3,200 Å apart. Yet that 3,000 Å variety, with waves just slightly closer together, creates sunburns eighty times faster!
UVC, the most powerful and lethal variety, is defined as UV light whose waves are between 2,800 Å and 400 Å apart—incredibly close. UVC is not only cancer-causing, it also has the power of speedy sterilization. Fortunately our atmosphere is so effective at blocking UVC that only a single UVC photon reaches the surface of our planet every thirty million years. So we don’t have to worry about UVC endangering our health. (Those who are gung-ho about future human colonization of other planets, however, should definitely read the UVC product manual, because every conceivable astronaut-visitation destination, including Mars and the moon, gets continuously bathed in this ultrapowerful UVC.)
Public enemy number one is UVB (whose waves measure between 3,200 and 2,800 Å in length), the villain responsible for sunburn and various skin cancers. This is the Goldilocks UV—its wavelengths are long enough to sometimes get through our atmosphere but short enough to have ionizing power. On the other hand, UVB is also best at inducing production of vitamin D in the skin, at rates of up to 1,000 international units per minute. That’s amazingly fast production, which is good for us, because it means we don’t have to stay exposed to UV rays for too long to get what we need.
Around 1 percent of the light hitting a sunbather is UV light—more if the sun is high overhead. That may sound like very little, but in fact it translates into a million trillion photons of UV rays per second. All are capable of altering DNA. Epidemiologists have discovered a disturbing link: every 1 percent increase in lifetime UV exposure produces a 1 percent boost in skin cancer incidence, although the truly deadly skin cancer, melanoma, seems to have its origin mainly in severe sunburns rather than ordinary sun exposure. Obviously the bottom line is: avoid sunburns.
That’s harder than it sounds. UV is a subtle beast, and it’s important to arm yourself with knowledge of its quirks so you can protect yourself. Lounging under a beach umbrella isn’t good enough, because one-third of UV radiation scatters in the atmosphere, so that it comes at you sideways. Because of this atmospheric scattering, half the UV reaching you comes not straight from the sun but rather from the sky’s UV brightness—utterly unseen by the eye. Relaxing in the shade is inadequate protection against sunburn if you’re exposed to a big swath of sky, which is why summer beachgoers who think they’ve been careful often return home with bright red shoulders and faces. Your surroundings strongly influence your likelihood of tanning or burning, regardless of whether you’re in sun or shade. Twelve percent of UV light reflects away from dry sand, but just 5 percent reflects away if the sand is wet, so the choice of where you spread your blanket can make a big difference in whether you get burned. Plopping yourself by the high-tide mark, with the wet sand and surf nearby, will give you less of a burn. Vegetation absorbs nearly all UV radiation and essentially reflects nothing, certainly less than 10 percent in all cases. So a lawn picnic will expose you to far less UV than an equal amount of time spent at the beach, even if it means choosing ants over sand flies. In addition, over the course of your lifetime, you may have noticed that you burn more easily on windy days. That’s because water generally absorbs UV light when it’s calm but reflects it when it’s rough or rippling. Thus a lakeside or riverside picnic is far safer on a calm day than a breezy one.
Thanks to dens
e air along the horizon, a very low sun sends us reduced visible light as well as reduced infrared radiation, and its ultraviolet emissions are essentially at zero. You cannot get a tan or burn during the final two hours of daylight. (Bob Berman)
We may associate UV exposure with beach days, but snow reflects six times more UV rays than even dry sand does. Because a whopping 80–90 percent of the ultraviolet light striking snow is reflected, you’d think skiers and snowboarders would all get burns. Well, sometimes they do and sometimes they don’t. It depends on when they decide to hit the slopes.
The time of day and the sun’s elevation determine how much ultraviolet light arrives to cause trouble. As the sun loses height, its light has to pass through an increasing amount of air. That’s because the lowest layers of the atmosphere are denser, or thicker, than those above them, and when we sight low we gaze exclusively through these low layers. To use real numbers, compared with an overhead view, we look through twice as much air when we view a star that’s one-third of the way up in the sky (thirty degrees high) and fourteen times more air when we look at the setting sun. And because air filters out UV rays, the more there is of it, the fewer UV rays can get through. From late April through mid-August, then, the sun is so high between 11:00 a.m. and 3:00 p.m. that you can burn in an hour or less.
In spring and summer, your safe, low-UV hours are between 5:00 a.m. and 9:00 a.m. and between 5:00 p.m. and 8:00 p.m. During those seven daylight hours UVA intensity is more than halved, and UVB is chopped by at least 80 percent compared with midday exposure. The sun may look and feel strong, but you won’t burn. Skin will temporarily redden because infrared light reaches you at nearly full strength, but the UV light is too weak to harm your skin unless you are very fair. So if your family is a tribe of blue-eyed blondes or redheads who all burn at the slightest provocation, the safest outdoor summer activity—no hat or sunscreen required—is a late afternoon picnic in a green environment: grass adores UV and sucks it in, reflecting a mere 3 percent toward your skin.
Back to our snowboarders. Because the sun stays low in the sky between November and February, your UV exposure during those months is minimal, even if you’re outside all day. But the sun’s midday elevation starts climbing rapidly in February, rising by the width of two suns (or what appears to be the width of two suns) every week. Beginning in mid-March, and especially during late March, the midday snow reflects prodigious amounts of UV light, which explains why late-season snowboarders do indeed get badly burned. Snow-reflected UV rays in March produce a burn three times faster than they do in December.
A hazy day screens away half the incoming UV rays. When the air feels very humid, it takes twice as much time to tan or burn. A cotton T-shirt or undershirt blocks 90 percent of the harmful UV rays coming at you, but the best UV-blocking fabrics are tight weaves such as denim. Less important is the color: nonetheless, a bright Day-Glo yellow will block more UV radiation than a muted color such as gray will.
Single-pane window glass blocks half the UV rays hitting it. Standard double-pane windows block even more. If it takes you one hour to tan outdoors, it will take fifteen hours behind a typical window. So feel free to indulge in all the nude indoor sunbathing you want (as long as you don’t have creepy neighbors). The more UV-reducing factors in play, the safer you are: sitting in a greenhouse in winter when the sun is low, you’d need at least 160 hours of steady noontime exposure to burn.
Travel alters UV exposure, too. It’s greatest at low latitudes because of the sun’s high elevation every day of the year, and it’s greatest in low-humidity environments, such as most of Australia. You may not have known that simply going to a place at a high elevation will crank up your UV exposure big-time. Every thousand-foot climb raises UV intensity by 4 percent. That’s why if you’re in Leadville, Colorado, you’ll get hit with 40 percent more UV than if you’re in Washington, DC, though both sit at the same latitude and thus receive equal solar intensity.
It will come as no surprise that clouds play a big role in filtering UV rays. “A thickly overcast day means no UV at all,” NASA atmospheric physicist Jay Herman wrote me in an e-mail. “It’s why Australians with their sunny climate have such a high rate of skin cancer compared with most Americans.” The clouds’ thickness matters greatly. Heavy, dark clouds may block all UV, but a high, thin cirrus layer lets almost 100 percent of the UV that reaches it pass through.
Our greatest protection from UV rays lies between six and thirty-five miles over our heads, in a layer of pale blue gas composed of molecules made of three oxygen atoms apiece. Peaking at an altitude of fifteen miles, the ozone layer is the earth’s primary shield against UVB. But it’s an amazingly delicate barrier: if all the air’s ozone were to settle at the earth’s surface, it would only be as thick as two stacked pennies.
Although ozone-destroying chemicals such as CFCs, used in aerosol sprays and refrigerants, and halon, used in fire extinguishers, have been banned, those long-lived molecules will continue to cause damage for a few more decades. NASA physicists monitor UV radiation with special satellites and predict that UV-blocking ozone will return to normal levels by 2050. Meanwhile, people with fair skin should, unlike mad dogs and Englishmen, stay out of the midday sun. For the rest of us, each day’s variable solar conditions require a judgment call. And probably sunscreen, whose SPF (sun protection factor) numbers reveal how effective the product is. A lotion with an SPF of 10, for example, tells us that if current conditions would give you a burn in one hour, the sunscreen will forestall the burn for ten hours.
Most sunscreens use either titanium dioxide or zinc oxide, chemicals that reflect, scatter, or absorb ultraviolet light and dissipate it as heat. In practice, creams labeled SPF 30 provide 96 percent of the protection of an SPF 90 product, which suggests that you’ll do fine with a 30 as long as you keep reapplying it as needed during the day.
The solar wind, a continuous flow of charged particles released in the sun’s upper atmosphere, excites air atoms as close as one hundred miles up from the earth’s surface. The result is the beautiful glow of the aurora, seen here from central Alaska. But every night, no matter where you are, though the pattern is much dimmer and more diffuse than it is during the daytime, the sky gives off a visible radiance—the effect caused by ultraviolet rays from the sun exciting atoms in our atmosphere. The sky always glows! This is why in rural places, far from artificial lights, nocturnal hikers can still see well enough to follow a trail, except where overhead foliage obstructs the sky. (Anjali Bermain)
If you’re one of the many millions who spend long hours working indoors, you may think that because you spend very little time exposed to the sun you can wash your hands of the whole UV issue. But it’s not that simple. UV radiation doesn’t just threaten us; it also sustains us and has the power to heal us. And our way of life is making it increasingly difficult to get the UV we need.
CHAPTER 7
Energy Rhythms
We used to take the cycles of day and night for granted. We obeyed them; we had no choice. But times have changed.
Sure, everyone knows that our planet spins once around its axis in twenty-four hours—even if the true figure, if we use the distant stars as a reference point, is twenty-three hours, fifty-six minutes, and 4.1 seconds. And everyone knows that all diurnal animals undergo waking and sleeping cycles in sync with a natural rhythm of light and darkness. But we also assume that humans are somehow above it all. Just as in the 1940s, when most sophisticated urban women in Western countries regarded the act of breast-feeding infants as somehow primitive and unnecessary and believed that babies raised on powdered or bottled formula would do just as well, so, too, did we imagine that we could dispense with being a slave to daylight. As Shakespeare’s Juliet said, “All the world will be in love with night and pay no worship to the garish sun.”
The shift away from regular sun exposure began in the nineteenth century, as the United States and parts of Europe began a steady transition from mostly outdoor, agrarian
societies to mostly indoor, industrialized societies. Accelerating this trend was the rise of the night shift in many areas of commerce during the early twentieth century, when Thomas Edison’s durable lightbulb allowed factories to run their assembly lines 24-7. At the same time, increasing numbers of people started to take night courses at colleges that offered them. We had become a society in which a hefty minority of us stayed awake during the night and slept during the day. Aside from some yawns at awkward times, there seemed to be little consequence. As usual, we were wrong.
In the midst of this massive shift to nocturnal, indoor activities, people who worked during the day shifts also started to avoid direct sunlight—on purpose. It wasn’t the visible rays they were shunning but the invisible ultraviolet rays. One of the deadliest forms of cancer, melanoma, was on the rise by the late 1950s, spurred by an uptick in the popularity of outdoor sports, such as fishing, golf, and tennis, and the start of a mass migration to sunny cities in the Southwest. Even though it claimed only around eight thousand lives annually, melanoma developed into a major media narrative that quickly turned into full-blown heliophobia.
Exacerbating the fear was the fact that far more common and much less aggressive skin cancers were indeed becoming endemic—but as far as media reporting was concerned, cancer was cancer. It can be deeply disconcerting to hear your physician tell you that you have a tumor. His or her next sentence, explaining that it is merely a benign variety that cannot metastasize and is therefore unlikely to cause serious harm, scarcely detracts from the fact that you’ve heard the dreaded word.
Studies showed that skin cancers of all types were far more prevalent in places where the sun was strongest. Moreover, people who spent the most time outdoors—e.g., on boats or playing golf—experienced the highest incidence of skin cancer. This was more than enough information for the general public as well as the medical community. The new anticancer suggestion was: avoid the sun.