HOW STUFF WORKS

HOW STUFF

by

Corey Buhay

illustrations by

Zohar Lazar

Curiosity is the root of adventure. You let it lead you to the next switchback, the next view, the next trailhead. Likewise, it probably drives you to ask questions—about everything from the color of the skytowhyyourkneesarekillingyou.Wegatheredoureditors’mostburning queries and spent weeks scouring textbooks, deciphering diagrams, and grilling experts for the answers. The result? Dozens of factoids that will impress even your most well-read hiking partner— and leave you with a new appreciation for our world.

NATURE

GEAR

PHYSIOLOGY

WHY DOES CONDENSATION FORM IN TENTS?

As you sleep, you exhale warm water vapor. That vapor cools when it touches a chilly tent fly, causing the airborne water molecules to slow down, clump together, and pool into droplets.

WHAT IS CRYPTOBIOTIC SOIL?

DOES IT REALLY TAKE 100 YEARS TO REGROW AFTER BEING STEPPED ON?

Cryptobiotic soil, also known as biological soil crust, is a hardened, bumpy layer found on top of the soil in desert ecosystems that traps moisture and prevents erosion. For crust to form, tiny cyanobacteria must colonize the soil and “glue it together” for lichens and mosses to get established.

Organisms that make up the crust only grow when it rains. According to United States Geological Survey researcher Jayne Belnap, damaged crusts may rebound after just 10 years in damp places like Idaho. As for dry Moab, Utah? Make that 70 years or more.

The takeaway: Stay on the trail. Even areas that look barren could be in a critical stage of recovery.

WHY DOES STICKY

SHOE RUBBER STICK?

Attraction between the atoms in your shoe and atoms on the ground creates friction. The greater the contact area, the more atoms interact. “Sticky rubber’’ is just a formulation of rubber that’s so soft, a footstep can squish it into the microscopic textures of the rock in order to vastly increase the contact area—and therefore atomic attraction.

ARE WOMEN’S SLEEPING

BAGS REALLY WARMER THAN MENS?

Yup. Most sleeping bags come with an internationally standardized rating called an “EN” or “ISO” rating. This tells you what temperature range is appropriate, from super cozy (its “comfort” limit), to decently warm (“extreme”). Usually, women sleep colder than men, so women’s bags are labeled with their ISO “comfort” rating while men’s bags list the “extreme” rating, says Sierra Designs product manager Ryan Bertrand.

Example: A women’s 20°F bag might have an ISO comfort rating of 20°F and an extreme rating of 14°F—meaning it’ll keep an average male comfortable down to 14°F. That doesn’t mean dudes should buy women’s bags to get more bang for their buck: Ladies’ bags have different proportions than men’s bags.

IS THRUHIKING

BAD

FOR ME?

Depends on your perspective. Most thru-hikers gain leg muscle (usually good) and temporarily lose weight (sometimes good). A case study found that one hiker’s arteries narrowed during his thru-hike (not good), perhaps due to dietary changes. Many thruhikers end hikes early due to injury (bad), and some develop chronic joint pain (definitely bad). But substantive research is limited. The only real evidence of negative health impacts? Cavities.

On a thru-hike, “you’re more likely to be eating something all the time. Teeth need time to recover from sugar, ” explains Karel Sabbe, a dentist and record-setting thru-hiker. “My oral

WHY IS WOOL

SO GOOD AT REPELLING STINK?

Bacteria grow best on damp, smooth surfaces. So, you can think of the shiny, sweaty, synthetic fibers in your polyester tee as a perfect petri dish for odorproducing microbes. Wool fibers, on the other hand, are covered with microscopic scales—natural structures that bacteria aren ’t as excited to reproduce all over. Plus, wool absorbs and wicks tons of moisture. No external moisture on your skin or clothes = no frisky bacteria.

hygiene during the PCT record attempt was the worst. I was too tired to brush my teeth and was probably eating a half a pound of candy and drinking at least a gallon of a sugar drink a day. ” Fortunately, Sabbe says, you will usually survive a week or so of sub-par brushing without cavities. But don’t push it: “The impact of [chronically poor oral hygiene] is huge and to this date still too much underestimated, ” Sabbe says. “It creates a constant inflammation and your body is constantly fighting it. ” Not something you want to worry about on the trail.

WHY DON’T I EVER POOP ON BACKPACKING TRIPS?

“That’s a fiber and hydration problem, ” says Aaron Owens Mayhew, Registered Dietician and Founder of Backcountry Foodie, a recipe and meal-planning resource for backpackers. “Hikers tend to eat more processed foods, which are naturally lower in fiber. You likely are eating more fiber and drinking more water at home, which is what’s keeping you more regulated.

MOST MOUNTAINS FORM NEAR THE EDGES OF CONTINENTS OR IN VOLCANIC REGIONS. HOW DID THE

ROCKIES

SHOW UP IN THE MIDDLE OF NOWHERE?

The textbook answer is that an oceanic tectonic plate got pushed really far underneath the West Coast. As the theory goes, “the slab was basically grazing along the bottom of the North American Plate, and—much like if you push a rug along a slippery floor—the plate started to ripple up in front of where it was being pushed, ” explains Craig Jones, professor of geological sciences at the University of Colorado Boulder.

“That’s a very nice idea, but there are some inconsistencies with what we see on the ground, ” he says.

Instead, Jones’s lab doesn’t think those shoving forces are what created the Rockies, per se. Instead, they think the sinking plate got coupled to the upper plate while it was descending. Meanwhile, the flow of magma between the plates created strong suction forces that pulled the plates together. The sinking plate was tugged upward and the upper plate was tugged downward, which ultimately left a hollow that masses of rock could tumble into. To get an idea of how this works, imagine you have a trampoline covered with tennis balls. Now, if you crawl under the trampoline and pinch the middle of it and pull down, the

Christina Buchanan, director of the High Altitude Exercise Physiology program at Western Colorado University, answers our biggest questions.

Q: Why does altitude make me nauseous? A: At altitude, your blood pressure increases, so there ’ s an increase in pressure in the arteries in your lungs. There seems to be a link between that and acute mountain sickness. Your body can have an abnormal or overactive response, and that can cause headache, nausea, and other side effects like troubled sleep. Q: What does acclimatization actually do to my body? A: In your first 24 hours at altitude, you start producing more red blood cells and breathing faster. Your heart rate increases. Your body shifts to prioritizing glucose as a form of energy. Most people take about three weeks to acclimatize, but some never fully acclimatize. Q: Does drinking lots of water help me acclimatize faster? A: No, but it will reduce compounding symptoms from dehydration.

Q: Do those oxygen inhalers you can buy at tourist shops help at all? A: No. They ’ re a waste of money, and they ’ re terrible for the environment.

tennis balls will roll and pile up in the hollow you’ve created. That’s what Jones thinks happened—geological stress below the continent caused the plate to dip, inviting tons and tons of rock to slide inward and pile up over millions of years, creating the mountain range.

WHAT CAUSES

ALPENGLOW?

According to Stephen Corfidi, a meteorologist with the National Oceanic and Atmospheric Administration (NOAA), the red-orange to neon-pink hues that bathe high peaks at first light are caused by the same phenomena as beautiful sunsets. Basically, we usually perceive the sky as blue because particles in the atmosphere reflect short wavelength light—blues and purples—down to our eyes. But at sunset and sunrise, the sun is so low in the sky that its rays travel farther before they reach us. Thus, the ” says Corfidi, catching those filtered rays.

atmosphere’s “filtering effect” is stronger. By the time light reaches the viewer at the far end of the horizon, all the blue is scattered out and only the red remains.

HOW DO HOLLOWPORE WATER FILTERS

WORK?

Hollow-pore filters are filled with tiny straws, each made of superfine mesh. These tubes fold in half to form a “V, ” which is stuffed into a filter casing and glued in place. Pressure from the filter forces water against the tip of the V at one end of the tube. The pores in the mesh are so small that water molecules can pass into the tubes, but bacteria, sediment, and other floaties can’t. Voila: Clean water pours out the open ends of the tubes on the other side of the filter.

HOW DO SUNCUPS

FORM?

“Suncups are these features that form on equatorial glaciers and in warmer climates. Usually you see them on glacial ice or firn, which is basically old, compacted snow. There are a few running hypotheses on how they get started, but I would say the best theory is that grains of dust or dirt shade the snow underneath them, so the snow around the dust grain melts faster than the snow underneath. That gives you preferential melting, which can cause a scallop to form. When you get a steeper angle on these features, the sun hits the walls of the cup at an oblique angle but hits perpen-

WHY ARE SOME PEOPLE MORE PRONE TO MOSQUITO BITES

THAN OTHERS?

It’ s largely genetic, says G. Mandela Fernandez-Grandon, a UK-based entomologist. Skeeters are super sensitive to smells, and different people have different skin-dwelling bacteria that produce those smells. Mosquitoes also tend to be more attracted to men than women because men have a higher surface temperature and more skin surface area. Fernandez-Grandon ’ s advice for mosquito magnets? “Travel with a friend who

dicular to the divots. So the divots melt out faster than the walls of the cups. These can get pretty extreme. I’ve been guiding on Mt. Rainier, hacking through suncups that are waist-deep, and it’s heinous. You can also see the same thing happen with big rocks— you can have a multi-ton boulder sitting on a narrow pedestal of snow because of that shading effect. It’s wild. ” —Max Lurie, AMGA alpine guide, glacier guide, and amateur glaciologist

DO TREKKING POLES

HELP MY GAIT OR RUIN IT?

They help reduce the load on lower extremities by up to 16 percent, according to physiologist Ashley Hawke. “We’ve seen consistent research showing that using poles alleviates pain in the knee, ” she adds. The only time they might cause trouble? Leaning forward on your poles while hiking downhill on loose terrain, which can throw your balance forward, causing slips and slides.

HOW DO LICHENS

GROW ON ROCK?

Lichens are made of two organisms working together: an alga and a fungus. Because they aren’t plants (and don’t have roots), lichens don’t need soil. Instead, they stick to rock with fleshy anchors called “rhizines” or “holdfasts, ” and absorb water and nutrients through their leafy skin.

WHY DOES GOOD PACK SUSPENSION MAKE LOADS

FEEL LIGHTER?

“Our spines have a bunch of little pads and pivot points. When the weight of your pack rests on your shoulders, these get pinned and compressed. That reduces upper body mobility and makes loads feel heavy and uncomfortable.

“So, the goal is to pull the load in toward your body and push it down into the hips. A good suspension is strong enough to both resist downward forces from gravity and outward forces from the compression straps, and direct loads straight downward to the pelvis. The result is increased range of motion, which makes you feel unencumbered. Plus, the force is now distributed across your hips, a larger surface area than your shoulders. If you have the same amount of force, but distributed over a greater area, that means fewer pounds of force per square inch (and therefore less pressure) and sensation of weight. ” —Dana “D3” Gleason, product manager and pack designer at Mystery Ranch

DO HIGHTOP BOOTS

REALLY PROVIDE MORE ANKLE STABILITY THAN LOWTOP SHOES?

“In our research, we compared hiking shoes and mid-top boots. We looked at muscle activity, joint forces generated, and physiological variables during uphill walking ... and found there were essentially no differences between boots and shoes. ” —Ashley Hawke, physiology researcher at Northern Michigan University

CAN TREES

ACTUALLY COMMUNICATE?

Believe it or not, trees are regular chatterboxes. They release chemicals into the air, transmit electrochemical signals through their roots, and exchange carbon and nutrients via vast networks of subterranean fungi. That’s according to Suzanne Simard, a professor of forest ecology with the

BURIED S E C R E T S

It took a near-catastrophe to introduce Dr. Suzanne Simard to the secrets of trees.

When Suzanne Simard was a young girl growing up in the forests of British Columbia, her dog Jigs fell into the outhouse. “Our family had to dig him out, the first time I saw soil at depth. ” There, several feet beneath the ground, she remembers seeing a thick, interlocking web of roots.

Ultimately, Jigs was saved, and Simard

University of British Columbia and author of Finding the Mother Tree: Discovering the Wisdom of the Forest. Simard also suspects that trees send signals via the “gazillions of species” of bacteria and microbes in the soil.

But what are they talking about? “There’s information in these chemical compounds that can tell neighboring trees whether or not there are enemies, like an herbivore eating the leaves or a pathogen that affects the tree, ” Simard explains. “The neighboring trees detect these compounds, and they’re able to increase their own defense against whatever the threat is. ” Trees are also able to detect the species and kinship of each of their neighbors—and preferentially send nutrients to their offspring. But it’s not all butterflies and rainbows: “There’s collaboration but there’s also competition, ” Simard explains. “Some communication is benevolent, and some is malevolent—just like human language. water repellent coating on your shell gets dirty or oily, it stops working. Water then sticks to your shell fabric, essentially blocking the pores. That makes your membrane impermeable in both directions: Rain is trapped outside—and sweat is trapped inside. The result? You feel damp and clammy, even though your membrane is still perfectly waterproof. To fix the problem, wash your shell with a technical wash detergent.

was left with a spark of curiosity about the secret lives trees might lead. Now, after decades of work as a forestry researcher, she ’ s learned more than she ever expected. Not only do trees communicate (see above), but that communication is incredibly advanced: According to a recent study, Simard says, electrical signals transmitted by fungi can be as complex as human language.

Does that mean forests are sentient? “I can I can ’t prove it if I look at the question as a scientist, ” Simard says. “But if I take off my scientist hat, and look at them as a human being who ’ s lived my entire life in forests? Well, then I say, of course they are. Why wouldn ’t they be?” After all, Simard says, a biodiverse ecosystem is a healthy ecosystem. It only makes sense that evolutionary pressure produced “ social” plant species that could collaborate to create a healthy forest—just as it produced social animal species.

High-altitude vegetation is preciously low on salt and other essential minerals. You know what isn ’t? Pee.

WHY DO MOUNTAIN GOATS LICK URINE?

HOW LONG DOES POOP

TAKE TO DECOMPOSE IN A CATHOLE?

One to three years (longer in cold or dry environments)

WHY ARE RAIN SHELLS

LESS EFFECTIVE OVER TIME?

Rain shells have three main parts: An outer fabric, a durable water repellent (DWR) coating, and a waterproof internal membrane. The membrane has many tiny pores that water vapor can pass through but liquid water droplets can’t.

Your pit sweat is full of vaporized moisture, which is drawn through the pores of your shell to the drier air outside. But when the durable

HOW DOES

TALUS

FORM?

Talus is accumulated rockfall. It’s more common at higher elevations because of violent freeze-thaw cycles there: Water makes its way into rocky fissures, then freezes and expands, prying off chunks of the cliff over time.

DOES THE LIGHTNING STANCE

REALLY PREVENT MY BODY FROM CHANNELING ELECTRICITY?

That’s a hard nope. The one-time theory was that if a nearby lightning strike was traveling through the ground, keeping your feet together would prevent the electricity from arcing up through one leg and down the other, zapping your heart on the way. The truth? Pigeon, lighting stance, shivasanna—get into any pose you want, but a close-enough strike can still find its way through your body. Instead, experts recommend moving to find shelter and avoiding tall objects, which can occasionally produce upward-reaching streamers of electricity during electrical storms, attracting nearby strikes.

HOW DOES DEET

WORK, AND IF IT CAN DISSOLVE MY RAIN SHELL, WHY ISN’T IT TOXIC?

DEET repels insects without hurting them. It’s so effective—and nonlethal—that farmers could spray DEET alongside deadly pesticides to deter honey bees, keeping them safe, says CDC entomologist Jeff Bloomquist.

Interestingly enough, scientists still aren’t 100% sure how DEET works. One of the better theories is that DEET targets nerve endings in mosquitoes’ antennae, temporarily blinding them to tasty smells, says Bloomquist. As for its effect on human health? “After 80 years of using this stuff, there’s little evidence that it’s dangerous, ” Bloomquist explains. Yes, high concentrations can degrade gear, but “humans fortunately aren’t made of plastic, ” he says.

WHY IS THAT PATCH OF SNOW

PINK?

Two possible answers. The first is a cold-loving species of algae (probably Chlamydomonas nivalis) that photosynthesizes and is pink in color. The second? Well, let’s just say you should lay off the beets.

FUELINGUP

IT’S NO SECRET SOME CAMPING FUELS WORK BETTER IN COLD WEATHER. TO UNDERSTAND WHY, YOU’VE GOT TO GET MOLECULAR.

BUTANE

Isobutane and butane have the same ingredients: four carbon atoms and 10 hydrogen atoms. Yet, butane molecules are zig-zag-shaped, so in cold temps, they tend to clump together instead of bouncing around inside the canister. The result: a slow, lazy fuel stream.

ISOBUTANE

Isobutane molecules are a different shape than regular butane. They have a

“tail, ” which means they can ’t get too close to one another. So, the molecules keep moving, creating higher pressure within the fuel canister—and a more even fuel stream in low temps.

PROPANE

Small molecules aren ’t as strongly attracted to each other, so tiny molecules in propane bounce around within the canister a lot more than butane. That’ s why propane canisters have to be so sturdy—and why they stay at high pressure even in the cold.

WHITE GAS

White gas, a cocktail of petroleum-derived fuels, is the most reliable choice in winter conditions. This is because liquid fuel stoves that use white gast let you manually regulate canister pressure, ensuring a consistent, even fuel stream no matter the temperature.

SWARM

C H A S E R

Dr. G. Mandela Fernandez-Grandon leveraged an unusual database to answer one of his biggest scientific questions.

Mosquitoes aren

’t the most glamorous study subject. So when asked how he got interested in studying the attractiveness of certain people to mosquitoes, Dr. G. Mandela Fernandez-Grandon laughed.

“I actually started out interested in odor communication— that’ s what I got my Ph.D. in, ” he says. But then, a colleague mentioned that he was trying to answer an age-old question about mosquitoes—and using odor analysis and a pretty unique dataset to do it.

“There ’ s a database in the UK of around 12,000 twin pairs. They all sign up to participate in these studies, ” explains Fernandez-Grandon. So, his lab emailed the list of twins, promised them they wouldn ’t actually get bitten, and brought them in. “We released over 1,000 mosquitoes per day over the course of the study, ” he says. The result? When there were two people in the room, the mosquitoes tended to prefer one to the other—unless the two were identical twins (i.e. had exactly the same genetics). Then the mosquitoes split up 50/50—showing no preference.

DO ELECTROLYTES ACTUALLY

DO ANYTHING?

Electrolytes are dissolved mineral ions—usually sodium, magnesium, and potassium—that your cells use to send chemical signals and keep fluid levels balanced. So yeah, they’re pretty necessary. As for electrolyte drinks and supplements? Not so much. Most research indicates that you get most minerals from the food you eat; salty within it. Squish those feathers together long enough for them to deform, and you reduce the air space where heat can settle, which lets the cold seep in.

snacks and plenty of water are usually enough to replenish what you lose through sweat.

WHY DON’T COMPASSES POINT TRUE NORTH?

Humans use “true north” —a fixed, geographic point at the top of the globe—as a navigational reference. But compass needles don’t actually “point” to the north pole, they simply align with the lines of the earth’s magnetic field, which is created by the flow of liquid nickel and iron around the earth’s core (badass, right?), and influenced by solar winds. That’s why it’s constantly shifting around, usually up to 37 miles in a year.

Because “true north” and “magnetic north” come from totally separate mechanisms, they only roughly line up, and the similarity varies at different points on the earth’s surface. Hence, declination.

HOW LONG CAN I KEEP A DOWN SLEEPING

BAG STUFFED BEFORE IT'S RUINED?

You can forget about that compression sack for up to a month before it’s a lost cause, says Ryan Bertrand of Sierra Designs. “But please, please don’t push your luck. ” What actually keeps you warm in a sleeping bag isn't the fill—it’s the air trapped

HOW CAN I GET RID OF LACTIC

ACID

FASTER?

“Lactic acid actually clears the body rather quickly, ” says Denverbased physical therapist Jamie Bovay. “Besides, soreness isn’t caused by the lactic acid or its byproduct, lactate, but because of the strain to the muscles themselves. ” While you can’t really reduce the amount of lactic acid (or the hundreds of other byproducts) your body produces during exercise, you can reduce that “burning” feeling by building up a tolerance, Bovay says. The trick? Regular physical training. (Sorry—there are no shortcuts here.)

HOW DO BLISTERS

ACTUALLY FORM?

Squeamish? This is your last warning. When your foot hits the ground, your outer layers of skin—which stick to your shoe via friction—move one way, and your inner layers move the other. This creates shear stress, which pulls one layer of skin away from the other. The resulting rift gets pressure-filled with a clear bodily fluid called serum. The result: A cushioned pocket that, left unpopped, protects the inner skin layer as it recovers.