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What Invisible Things Are in the Surfaces You Touch and Air You Breathe?

A DISCOVER editor delves into the unseen forces that affect our lives.

By Stephen Cass
Aug 29, 2008 12:00 AMNov 3, 2019 7:29 PM


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What Invisible Things Are in the Surfaces You Touch and Air You Breathe?

A DISCOVER editor delves into the unseen forces that affect our lives.


Each morning I wake and open my eyes to a new day filled with things I can’t see. I’ve even grown to appreciate how much the unseen makes its presence felt throughout our daily lives. It has been this way since the dawn of time, but modern science has opened the doors to understanding the unseen worlds that crowd into our own and even allows us to manipulate some of them for our own ends. An endless silent babble of radio waves, massed armies of insects, long-gone planet-girdling ice sheets, endemic microbes, rivers of wind, and more all leave their stamp on the shape of my life in the course of 24 hours. Determined, I set off to unravel the mystery of my invisible day.

The Demons Within 8 a.m. I could pretend that I shoot out of bed bright-eyed and bushy-tailed, ready for another day at DISCOVER. But the truth is much blearier, an important part of which is the eradication of the first invisible presence of the day: morning breath. My mouth feels less than fresh as I yawn my way to the bathroom.

Morning breath comes mostly from bacteria that live in the mouth. More than 500 types of oral bacteria have been identified in people so far, and “we keep on identifying more,” says Patricia Lenton, an oral malodor researcher at the University of Minnesota School of Dentistry and a “calibrated breath odor judge.” While we are sleeping, the flow of saliva in our mouths decreases, leaving the bacteria alone “back there, just producing things, lots of sulfur gases,” Lenton says. These orally produced sulfur gases—with names like hydrogen sulfide, methylmercaptan, and dimethyl sulfide—plus some other miscellaneous by-products of bacterial metabolism, account for 90 percent of bad breath that can’t be traced to an outside cause. Meanwhile, foods such as garlic and onions release sulfur compounds as they are digested in our intestines. Some of these compounds are absorbed into the bloodstream and pass into the air in our lungs. As we exhale, we breathe them out.

It’s also through the lungs that changes in blood chemistry caused by disease can affect the odor of our breath. “Diabetes is a good example. When people have uncontrolled diabetes, they can have a really sweet, fruity smell in their breath,” Lenton says. Researchers are even working to develop tests for breast cancer and organ transplant rejection based on the bouquet of a patient’s breath.

Most odor-producing bacteria live on the tongue, not the teeth, so I give my tongue a few good scrubs with my toothbrush before continuing my morning routine.

Scrutinizing the Jet Stream 9 a.m. I’m ready to leave, checking out the window for the effects of that all-time-classic invisible entity, the wind. I’m not looking for the effects of just any old gust of air. The specific wind that is going to determine whether I’ll have to put on a jacket is one that weather watchers didn’t even know existed a century ago.

It’s called the polar jet stream, and as it writhes eastward across the North American continent, it can bring storms in its wake or herald an unseasonable change in temperature—north of the jet stream lies cold, Arctic air, while to its south are warmer conditions. In summer months the polar jet stream flows mostly across Canada. During the winter it dips as far south as the U.S. Gulf states.

Jet streams occur at very high altitudes—30,000 to 40,000 feet—which is why they were not definitively identified until World War II, when pilots noticed intense headwinds during long-distance military missions. The heart of a jet stream is a relatively narrow band of strong wind a few hundred miles wide that can reach speeds of more than 200 miles per hour. Jet streams draw their energy from the rotation of the earth and the difference in temperature between the equator and higher latitudes. Without jet streams, “it would be a pretty boring place,” weatherwise, says Klaus Weickmann, a meteorologist at the Earth System Research Laboratory of the National Oceanic and Atmospheric Administration (NOAA) in Boulder, Colorado.

Small changes in the jet stream as it passes overhead can create stormy weather at low altitudes. For example, “if you have a low-pressure area aloft, then you will tend to produce low pressure at the surface ahead of it,” Weickmann explains. “That particular [atmospheric] structure is very efficient at extracting available potential energy and converting it into kinetic energy.” This kinetic energy manifests itself in the kind of high winds and rains that can turn a day into a washout. From what I can see out my window though, the weather appears to be pretty calm, so I decide to leave my jacket at home and gather my things. I open my building’s front door and look up at the slight hill I have to climb to my subway stop.

Glacial Moment It’s not much of a slope, but this hill, and others like it, are evidence of the ancient forces that ultimately brought me and more than 8 million other people to live in New York City. At the peak of the last ice age, some 20,000 years ago, right outside my front door was a frozen glacier wall that rose as high as 300 feet, the southern edge of a vast ice sheet that covered Canada and the northern part of the United States. “Glaciers act as a plow, pushing stuff ahead,” says Sidney Horenstein, a geologist at the American Museum of Natural History in New York City. The edge of America’s ice sheet—marked by a line of rubble called the terminal moraine—ran along Long Island. When the earth warmed and the glacier receded, the rubble was left behind as a series of low hills. Look at a map of New York City and in the boroughs of Brooklyn and Queens (located on the west end of Long Island) you can see that chilly history encoded in the names of today’s neighborhoods: Cobble Hill, Brooklyn Heights, Park Slope, Forest Hills. Southeast of where I live, water from the melting edge of the glacier flowed over the landscape, depositing layers of sand and silt and leaving behind areas with names such as Flatbush and Flatlands. “The community names have meaning,” Horenstein says.

But the biggest impact on New York’s destiny came from the glaciers’ ability to erode, not build, landforms. A glacier “acts as sandpaper because it has rocks embedded in its base…so as the glacier moves, it’s deepening valleys and smoothing off the tops of hills,” Horenstein says. As the glacier moved south toward the future location of New York City, it widened and deepened the Hudson River valley. “The Hudson is the southernmost fjord in North America,” Horenstein says. When the first Europeans explored the river in 1609, they found in it an ideal trade route that penetrated into the continent. The glacier’s deepening of the Hudson also made New York Harbor a snap for trans-Atlantic shipping to navigate.

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