100 Mysteries of Science Explained

by Popular Science

  But those rocks are just proof that dirt existed on the planet way back then. The stuff in your backyard is much fresher. “Most of the dirt you see today is from the past 2 million years,” Pavich says. Long ago, the planet underwent major changes that drove the formation of new dirt.

  Global cooling and drying enlarged the deserts, and dust storms redistributed that dirt around the globe. Meanwhile, glaciers began extending from near the poles, grinding rocks, soil, plants, and everything else into dirt as they moved over the land.

  Dirt is still being produced all the time, albeit in much lesser quantities. Beneath the soil’s surface, rocks constantly react with rainwater or groundwater and slowly grind together, breaking down into smaller minerals. So in that respect, dirt really isn’t that old. Then again, Pavich notes, a lot of what came out of the Big Bang was essentially dust, which then condensed to form the stars and, later on, planets. “If you think about it,” he says, “dirt and its origin are older than the stars.”

  The process of platetectonics causesmovement alongfault lines withinEarth, creating vastmountain chains likethe Himalayas, overmillions of years. Mount Everest, pictured on theright, has severalcomplicated faultsrunning through it.

  How Do Plate Tectonics Work?

  If you’ve ever felt the ground shake beneath your feet or seen pictures of a lava-spewing volcano, you know the effects of plate tectonics.

  Earth has three major components. In the center is the core, surrounding that is the mantle, and the outer layer of the planet is the crust. Together, the crust and the top part of the mantle are called the lithosphere, which is about 60 miles (97 km) deep in most places. The lithosphere is made up of eight major tectonic plates and some smaller ones. (The number, size, and shape of plates change throughout Earth’s history.) The plates can be oceanic—under the oceans—or continental. Tectonic plates are in constant but very slow motion, propelled by the movement of molten rock beneath the lithosphere.

  The location where two plates meet is called a boundary. How the plates interact at a boundary creates different geological and oceanographic processes and activities. Scientists have identified three major types of boundaries. At a divergent boundary, two plates are moving away from each other. Magma fills the gap between the two plates, creating new crust. One divergent boundary is the Mid-Atlantic Ridge. Over hundreds of millions of years, the slow separation of the North Atlantic and Eurasian Plates along that boundary created the Atlantic Ocean.

  A convergent boundary occurs where two plates are moving together. At times, one plate might go underneath another, creating what are called subduction zones. The rising of an upper continental plate over a subducting oceanic one creates mountain ranges. Mountains also form when two continental plates meet head on; that’s how the Himalayas were created. The two plates continue to grind together, adding to Mount Everest’s height. The meeting of two oceanic plates forms deep trenches below the water’s surface, as happened in the Pacific Ocean. In general, convergent boundaries produce many earthquakes and lots of volcanic activity.

  Sometimes two plates slide horizontally against each other, creating a transform boundary. The area between the two plates can develop transform faults, which can be the scene of major earthquakes. California’s San Andreas Fault stirs that state’s greatest seismic activity. Los Angeles is on the side of the fault that is slowly moving northward, while most of the state is on the side going south. In a few million years, Los Angeles and San Francisco will lie practically side by side.

  The theory of plate tectonics suggests that our planet’s landmasses and oceans are constantly changing. Millions of years from now, Earth’s surface will look much different than it does today.

  How Big Would a Meteorite Have to Be to Wipe Out All Human Life?

  When it comes to meteorites, the bigger they are, the more havoc they generally wreak.

  In 1997, University of Colorado geoscientist Brian Toon and colleagues predicted the aftermath of meteorite impacts of various sizes. They found that a space rock a ½ mile (0.8 km) wide would produce an explosion with the energy of 100,000 million tons (Mt) of TNT. That’s enough to cause widespread blast damage and earthquakes, but nothing too out of line with many natural disasters in the modern age. Once a collision exceeds the 100,000 Mt threshold, you’re looking at a catastrophe larger than any in human history. A meteorite 1 mile (1.6 km) in diameter might send enough pulverized rock into the stratosphere to block out sunlight and cause global cooling.

  The object that killed off the dinosaurs was probably 7 or 8 miles (11.2 or 12.8 km) wide, says Jay Melosh, a planetary physicist at Purdue University. Its impact would have ejected a dust plume that spread clear around the planet and rained blazing-hot ash onto forests, igniting them. “The dinosaurs probably broiled to death,” he says.

  Such a collision today would kill billions of people. Those who didn’t perish in the initial blast or the fires that followed would face long odds of finding food. “People are going to starve to death,” Toon says. Still, a few would likely weather the apocalyptic storm. “Probably some fishermen in Costa Rica,” he offers. “People near the oceans who managed to hide out and fish when the fires started.”

  For a collision to obliterate the human race altogether, Toon estimates it would take a 60-mile-(96.5-km)- wide meteorite. He says, “That would incinerate everybody.”

  Are We Really Drinking Dinosaur Pee?

  You might cringe at this idea the next time you turn on the tap to fill a glass with water, but scientists believe that all water on Earth was at some point consumed and passed by prehistoric creatures. Whether you think of it as water that passed through a dinosaur or water that passed through cavemen, all water on Earth has been recycled.

  Charles Fishman, in his book The Big Thirst, notes, “No water is being created or destroyed on Earth.” This might lead us to believe that we are in fact drinking dinosaur pee, but scientists caution against describing it this way.

  The water cycle controls the water on the planet through the processes of evaporation and condensation. The amount of water in the water cycle has stayed the same since the time of the dinosaurs. Nature’s ecological filtering process rejuvenates water, continuously breaking down and re-forming the oxygen and hydrogen bonds. So it’s true that the H’s and O’s are the same since the time of the dinosaurs, but are you drinking the exact water molecules that a Tyrannosaurus rex gulped down and later expelled millions of years ago? No, and illustrating the process in terms of dinosaur pee is a negative image that recycled water can’t afford.

  Since water resources are scarce in many parts of the world, scientists are experimenting with the idea of turning our waste water into drinking water. Residents in Southern California have been drinking recycled water, endearingly nicknamed “toilet to tap,” for decades. While many people can’t stomach the idea of guzzling someone else’s waste, this form of recycling could be our answer to the water shortage problem. Perhaps if people thought of it as water rejuvenation, there might be more acceptance. The negative perception is driven not by what is in the water, but by the history of where it’s been. But ultrapurified water can be certified as much “cleaner” than regular drinking water from the tap. If we can change the negative image, we may soon purchase “Bottled Dinosaur Pee” at the local corner store.

  A wildfire in the Great Dismal Swamp National Wildlife Refuge in Suffolk, Virginia, in 2011 ignited a fire tornado.

  How Do Fire Tornadoes Form?

  Veteran firefighters have seen whirling columns of fire shooting into the air. Known as fire tornados, fire devils, fire whirls, or firenados, they can be several hundred feet tall and reach 2,000 degrees Fahrenheit (1,093 degrees Celsius). While most last only a few minutes, which explains why they’re not often captured on film, in 2012 an observer in the Australian bush saw several that lasted for more than 40 minutes.

  A fire tornado is a vortex—a whirling mass of a liquid or a gas, such as air, that revolves around its own
center. A vortex forms when the flows of two forces meet, such as when you pull a plug on a stopped sink. The water rushing downward meets air trying to escape upward through the pipe, creating a swirl of water.

  In a large fire, columns of hot air rise. If winds are blowing, the two forces come together and form a vortex. The wind does not have to be intense for a vortex to form. The spinning cylinder of air then picks up burning embers and ash to create a moving column of fire. The firenado can also suck up flammable gases; these and the burning items can spread a fire. Along with spreading fires, firenados can also pick up and toss objects, as tornados do. In 2000, one firenado lifted a small vehicle off the ground and slammed it into an SUV.

  Observations by California firefighter Royal Burnett, made in 2008, suggest fire tornados are most likely to occur in desert areas or places experiencing a drought. Those conditions foster the extremely dry fuel, rapid combustion, and high heat associated with fire devils.

  According to Andrew Sullivan, an Australian fire researcher, it is difficult to determine exactly when fire tornados will form and how they will behave. Since they usually appear during sudden, strong fires, he says firefighters need to reduce the amount of heat generated as quickly as possible in order to prevent fire devils from forming.

  When Is the Next Ice Age Due?

  Ice ages have, in fact, been dominant in Earth’s history. Interglacial warm periods, like the current Holocene, are an aberration. Orbital variations and our current warming trend show that the next ice age should begin within the next 1,500 years. Is it time to pack up and move to lower latitudes?

  Each transition to an ice age and back is different, because the precise combination of factors does not repeat exactly. This could explain why interglacial periods are not all the same length. Variations in Earth’s orbit are one culprit. The subtle wobbles are known as Milankovitch cycles, after the Serbian scientist Milutin Milankovitch, who first described the effect 100 years ago. But the way orbital variation affects Earth’s climate is not entirely known. Researchers use data on Earth’s orbit to find the historical warm interglacial period that is most similar to our current one. The most recent period, called Marine Isotope Stage 19c, was 780,000 years ago. The transition to the following ice age began with a period of warming and cooling that swung between the Northern and Southern Hemispheres. According to Richard A. Muller at the University of California at Berkeley, the next ice age may occur “any millennium now,” but human effects on the environment have altered the trajectory. Even if we halted all current carbon emissions, we will still enjoy a long interglacial period. Atmospheric concentration of CO2 will probably have to fall below 240 parts per million (ppm) before glaciation could begin. Our current level is about 390 ppm, a consequence of burning coal, oil, and other carbon-rich fossil fuels that release billions of tons of carbon dioxide into the atmosphere.

  The Holocene has lasted 10,000 years and allowed the human species to flourish through agriculture, technology, and mobility. “We have taken over control of the mechanisms that determine the climate change,” says James A. Hansen, the director of NASA’s Goddard Institute of Space Studies. And some think that’s not a bad thing, as an ice age may halt food production and could even lead to the extinction of human beings. Groups who oppose restrictions on CO2 emissions cite the warming trend as a reason not to change our current habits. Scientists agree that humans would be better off in a warmer world filled with greenhouse gases than in a frigid glaciation period. But, they warn, we are not simply maintaining our warm climate but heating it further. Scientists also note the complexity of climate change. In fact, human-induced warming may shut down heated ocean currents that keep the northern latitudes warm, resulting in an even faster descent into an ice age. Luke Skinner at Cambridge University warns, “There are huge consequences if we can’t cope with that.”

  Are Earthquake Lights Real or Illusory?

  For centuries, eyewitnesses have reported flashes of strange bright lights in the sky before, during, and after an earthquake. The lights manifest in many different shapes, colors and forms: bluish, flamelike columns rising from the ground; balls of light that seemingly float in the air; and rainbow-colored, flickering flames. The strange phenomena, called “earthquake lights,” appear for seconds, minutes, or even hours at a time.

  In 1906, witnesses reported blue flames in the foothills west of San Francisco just before the historic earthquake devastated the city. In 1988, a luminous purple-pink orb of light crossed the sky above the St. Lawrence River in Quebec, 11 days before a powerful quake. Seconds before a 2009 earthquake struck L’Aquila, Italy, 4-inch (10-cm) flames of light were seen flickering above a cobblestoned street.

  Various hypotheses to explain the formation of earthquake lights have suggested the disruption of Earth’s magnetic field in the locale of tectonic plate stress and the piezoelectric effect, in which tectonic movements of quartz-containing material produce voltages that result in flashes of light.

  In 2014, a team of scientists led by Robert Thériault, a geologist with the Quebec Ministry of Natural Resources, and Friedemann Freund, professor of physics at San Jose State University and a senior researcher at NASA’s Ames Research Center, published a study claiming that earthquake lights appear to embody a different electrical process altogether. The team analyzed 65 earthquakes starting in the 1600s that produced reports of lights. According to Freund, their findings reveal that, “when nature stresses certain rocks, electrical charges are activated, as if you switched on a battery in the Earth’s crust.” The coarse-grained rocks are basalts and gabbros, which are found in underground vertical structures called dikes, resulting from the cooling of magma deep underground.

  When a seismic surge impacts the dike, electrical charges in the rocks are released and funneled upward through cracks in the rocks. “The charges can combine and form a plasma-like state, which can travel at very high velocities and burst out at the surface to make electric discharges in the air,” explains Freund.

  What Is Ball Lightning?

  Imagine yourself taking shelter during a powerful electrical storm. Lightning strikes the earth nearby, close enough for the thunder and the flash to reach your ears and eyes almost simultaneously. You’re glad you’re safely indoors during such a ferocious storm, but then a startling sight catches your eye: A glowing orb, about the size of a basketball, floats in through the window.

  You stare, spellbound, as this orb hovers past, maintaining an eerily steady elevation. Just as you begin to reconcile what you’re seeing with your own mental catalog of sights and experiences, the orb explodes with the report of an artillery shell, knocking you to the ground. All that’s left is the smell of sulfur and a story your friends will scarcely believe.

  You have just witnessed ball lightning.

  Ball lightning has baffled and stunned witnesses for centuries. Scientific explanations for the phenomenon ranged from air ionized by cloud-to-ground lightning to vaporized soil, microwaves, and even miniature black holes. One hypothesis held that ball lightning was not real but rather a product of hallucinations. A modern interpretation of the hallucinatory hypothesis proposed that the visions might be caused by magnetic stimulation of the brain resulting from a more typical lightning strike.

  Recent laboratory experiments and fortuitous real-world observations suggest that ball lightning is, indeed, a real thing. In 2012, Chinese scientists studying ordinary lightning in northwest China caught ball lightning on a spectrometer. The spectral signature that the researchers captured supports the vaporized soil hypothesis, reflecting the same silicon, iron, and calcium that are found in common soil. Scientists in the lab have also been able to replicate ball lightning by shooting simulated lightning through silicon wafers.

  New findings aside, ball lightning remains a science mystery. The vaporized soil hypothesis doesn’t explain why ball lightning has been observed traveling through solid objects like windows. Without more data, it remains unclear if ball lightning is a singl
e phenomenon; variations in reports on the size, color, and movement of ball lightning raise the possibility that it could be a collection of several. Nor do these results rule out the possibility that some sightings could be hallucinatory. More experimentation and observations are necessary before we uncover the secrets of this spectacle.

  Why Can’t We Predict Earthquakes?

  Can scientists be imprisoned for not accurately predicting earthquakes? After the devastating earthquake in L’Aquila, Italy, in 2009, seven scientists faced manslaughter charges for not issuing explicit warnings after small tremors shook the area. The seven were convicted, though six later had their verdicts overturned. The original trial judge said the case was not about a failure to predict the quake, but rather about disseminating misleading communication. That’s good to know, since no scientist anywhere in the world can predict exactly when or where the next temblor will strike.

  Earthquakes occur along the faults between two tectonic plates. While scientists know where these faults are, they never know when the plates will move. Scientists can detect vibrations in the ground right before a major quake, but they don’t have enough time to alert people in the area.

  Although seismologists can’t predict when and where quakes will occur, they can predict the probability of large earthquakes happening along faults. Through the study of patterns of strain in the rocks along a fault, and the history of earthquakes in the region, seismologists can calculate the odds of a temblor of a certain magnitude striking again within a certain time frame. For example, the U.S. Geological Survey predicts that over the next 30 years, the odds of a major quake hitting the San Francisco area are 67 percent.