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        The final frontier smells a lot like a NASCAR race— a bouquet of hot metal, diesel fumes, and barbecue. The source? Dying stars.     The by-products of all this combustion are smelly compounds called polycyclic aromatic hydrocarbons. These molecules “seem to be all over the universe,” says Louis Allamandola, the founder and director of the Astrophysics and Astrochemistry Laboratory at NASA Ames Research Center. “And they float around forever,” appearing in comets, meteors, and space dust. These hydrocarbons have even been short-listed as the basis of the earliest forms of life on Earth. Not surprisingly, polycyclic aromatic hydrocarbons can be found in coal, oil, and even food.            Though a pure, unadulter- ated whiff of outer space is impossible for humans (space is a vacuum, after all; we would die if we tried), we can get an indirect sense of the scent: When astronauts work outside the International Space Stat...

     Black holes are already among the most mysterious objects in the universe, even before we begin to contemplate what might be at the “bottom” of one. The concept of a tiny star whose gravitational field is so strong that neither light nor matter can escape was so foreign to those who first theorized their existence that even Albert Einstein himself, whose math confirmed their possibility, dismissed the likelihood of their existence. As to the question of what’s at the bottom, the answer— depending on the physicist—may be just about anything, or nothing, or even another universe.         At the outer edge of a black hole is the event horizon, the boundary where velocity required to escape its gravity exceeds the speed of light. Past this point, all energy and matter that enter the black hole will proceed infinitely toward the singularity, a point of infinite density that, according to Einstein’s theory of general relativity, represents a bottomless...

     The Moon seems larger when it is near the horizon than when it is high in the sky, a phenomenon called the Moon illusion. Although recognized for centuries—the horizon Moon was important to early civilizations that functioned according to the Moon’s cycle—this ancient phenomenon has only recently been explained. Early astronomers believed the Moon at the horizon was physically closer to Earth than when it was high in the sky, and the closeness meant a larger Moon. However, Newton’s description of the Moon’s orbit showed the contrary to be true. The Moon Is actually closest to the observer at its zenith, or when it is high in the sky, but the difference is so small that it is negligible anyhow. Others theorized that the Moon illusion was caused by refraction when light rays passed through more of Earth’s atmosphere. Today, scientists guess that the illusion occurs not externally, but through a trick of our brains.          Optical illusions p...

    Astronomers can say with near certainty that there are no moons with moons in our solar system. But that doesn’t mean it’s physically impossible. After all, NASA has successfully put spacecraft into orbit around our moon.         Although astronomers have spotted some asteroids with moons, a parent planet’s strong gravitational tug would make it hard for a moon to keep control of its own natural satellite, says Seth Shostak, a senior astronomer at the nonprofit Search for Extraterrestrial Intelligence (SETI) Institute. “You would need to have a wide space between the moon and planet,” he says. Orbiting far from its parent planet, a relatively massive moon might be able to hold onto a moon of its own. Conditions like these might exist in faroff solar systems, but while hundreds of exoplanets (planets outside of our solar system) have been detected, there’s almost no chance we’ll be able to spot exomoons much less moons of exomoons, for decades to come. M...

      It’s easy to proclaim that the existence of aliens is a crazy idea, until you consider these words from astrophysicist Stephen Hawking: “To my mathematical brain, the numbers alone make thinking about aliens perfectly rational. The real challenge is working out what aliens might actually be like.”         Other scientists agree. But while the existence of alien life is mathematically probable, humans have not been able to prove that extraterrestrial life does exist. The quest to find that life has taken several forms. The Search for Extraterrestrial Intelligence (SETI) Institute, based in California, uses giant radio telescopes to try to detect radio signals sent by far-off, technically advanced life forms. NASA’s Kepler Space Telescope has found planets  within the Milky Way that could have the right conditions for life to develop. By one estimate, as many as 20 percent of the stars in the galaxy have such a suitable planet. A 2015 rep...

    Seven thousand years ago, a supermassive star in the constellation we now call Taurus collapsed in on itself and exploded into a supernova so bright that—when its light reached Earth in 1054 C.E.—it could be seen in broad daylight. What was left behind was the brilliant Crab Nebula, a well as the Crab Pulsar that illuminates it. This neutron star pulses out radiation across the entire electromagnetic spectrum at a rate of 30 times per second. But why does it pulse at all?         Only half a century ago, nobody knew that pulsars, short for “pulsating stars,” existed.In 1967, when astronomers Jocelyn Bell Burnell and Antony Hewish first discovered a pulsating source of emissions all coming from the same point in the sky,among the first hypotheses was that these pulses were radio waves emitted by an alien civilization. Burnell and Hewish even went so far as to name the object LGM-1, short for “Little Green Men.” Subsequent discoveries of new pulsars...

      In 2010, data gathered by the Fermi Gamma-Ray Space Telescope revealed a new discovery. Scientists were surprised to find two enormous, bubble-like clouds that extend 50,000 light-years across the center of our galaxy, the Milky Way.     The two gamma-ray-emitting bubbles stretch across more than half of the visible sky and may be millions of years old. (Gamma rays are electromagnetic radiation at the highest-energy, or shortestwavelength, end of the electromagnetic spectrum.) The origin of these previously unseen structures, however, remains a truly baffling mystery.    A research paper appearing in the Astrophysical Journal in 2014 described some features of the aptly dubbed “Fermi bubbles.” First, the outlines of the structures are very sharp and well defined, and the bubbles glow evenly across their enormous surfaces. The most distant areas of the bubbles feature extremely highenergy gamma rays, yet there is noapparent cause for them that far...

      In 1980, Henry Thomas, a 73-yearold man living in Wales, was found burned to death in the easy chair of his living room—the trunk of his body nearly completely incinerated, but oddly, his feet unburned and the remains of his legs still clothed in socks and pants, practically untouched by the fire. Thomas’s death was ruled “death by burning,” although no cause of the apparent fire was noted.           In December 2010, the body of 76-yearold Michael Faherty was discovered burned beyond recognition in the living room of his home in Galway, Ireland. The damage caused by the fire was limited to Faherty’s burned body, the ceiling above, and the floor beneath him. The coroner concluded Faherty’s death “fit into the category of spontaneous human combustion.” Can human bodies spontaneously burst into flame without being ignited by an external source of heat? Most scientistsc would argue that humans cannot catch fire without an apparent cause. ...

     The year is 2050. The carbon crisis is a thing of the past. A new source of power delivers cheap, plentiful electricity to large, contained cities populated by millions of people. Fusion power has birthed a utopia on Earth by neutralizing the most imminent threat to human survival,the finite supply of fossil fuel, while eliminating a persistent source of conflict. All is well—until a robotic alien from outer space destroys your fusion plant along with the rest of your city.     The scenario just described is familiar to anyone who grew up playing the popular 1990s simulation game SimCity 2000. As far as fusion power is concerned, the predictions of Maxis (the company that designed SimCity) from two decades ago seem prescient: Steve Cowley, a plasma physicist and the CEO of the United Kingdom’s Atomic Energy Authority, expects the first viable demonstration reactors to be available sometime in the 2040s. That said, critics and proponents alike lament that nu...

    In 1929, Edwin Hubble discovered that the universe is not in fact static, but expanding. In the years following his discovery, cosmologists took up the implications of the discovery, asking how long the universe had been expanding, what forces caused the expansion, and whether it will ever cease.    Cosmologists are pretty confident about the first question: just shy of 14 billion years. A great deal of evidence supports the predominant answer to the second question: The universe rapidly emerged from a singularity in an event that cosmologists call the Big Bang. The third question is a bit more mysterious, and the answer relies on an obscure, confounding phenomenon known as dark energy. The density of dark energy in the universe determines its ultimate fate. In one scenario, the universe does not possess enough dark energy to forever counteract its own gravity and thus ends in a “Big Crunch.” Under this scenario, the universe’s gravity will overcome its expansio...

         Ever since people first tilted their gaze up toward the heavens, they have wondered about the possibility of other worlds like ours orbiting distant suns. Until very recently, such questions were left to the realm of speculation. Today, thanks to telescopes like the Kepler space observatory and increasingly advanced surveys from ground-based technology, we know that the galaxy is swarming with planets. But are any of them habitable? Do any of them resemble our own?     The question of habitability is a tricky one, and the odds of any individual planet possessing Earth-like properties are rather low. That said, the numbers are in our favor. Kepler recently confirmed the discovery of its 1,000th exoplanet. Some astronomers now estimate that there is one exoplanet for every star, on average. That means there are billions and billions of planets in our universe! Many of these planets, though, are nothing close to habitable. The first exoplanets th...

           If you had started just before the first dinosaurs appeared, you’d probably be finishing your hike just about now. Here’s how it breaks down. One light-year —the distance light travels in one year, used as the yardstick for interstellar distances—is about 5.9 trillion miles (9.5 trillion km). If you hoofed it at 20 minutes a mile, it would take 225 million years to complete your journey (not including stops for meals or the restroom). Even if you hitched a ride on NASA’s Mach 9.8 X-43A hypersonic scramjet, it would take more than 90,000 years to cover the distance. You’d need to bring a big backpack, too: Walking such a distance requires substantial supplies. The average adult burns about 80 calories per mile walked, so you’d need about six trillion granola bars to fuel your trip. You’d also produce a heap of worn-out shoes. The typical pair of sneakers will last you 500 miles (800 km), so you’d burn through some 11.8 billion pairs. And all that ...

      There are several theories of the multiverse. One comes from the “many worlds” interpretation of quantum physics by Hugh Everett. In 1955, over a bottle of sherry while a student at Princeton University, Everett considered the implications of quantum physics. At the      Elementary level (protons and electrons), each particle exists in a superposition of different locations, velocities, and orientations of its spin, but when measured by scientists there is a definitive result. Somehow our unique world emerges in a system that has a multitude of possibilities at the quantum, or nanoscopic, level. In this theory, every possible outcome in the universe exists simultaneously in other universes. For example, if you shoot a basketball and miss, there is a parallel reality in which your basketball slides rightthrough the net. This alternative universedoesn’t occupy a physical space, but isinstead a co-existing, abstract reality.     However, for ma...

   Will an asteroid hurtling through space some day crash into Earth and cause massive damage? The odds are small, but they’re real. Deflecting an incoming asteroid might seem like the stuff of science fiction, but scientists say it can bedone—if the asteroid is detected in time. Given enough prior knowledge, former U.S. astronaut Ed Lu says, governments could launch one or more spacecraft into the threatening asteroid and change its path enough so that it would miss Earth. These “kinetic impactors,” Lu says, could even divert an asteroid the size of the one that brought down the dinosaurs. Lu is one of the co-founders of the B612 Foundation, a non-profit organization that monitors asteroids and other Near Earth Objects (NEO) and studies how to protect Earth from them. Its goal is to fund the building and launch of a space telescope named Sentinel. The telescope, scheduled for launch in 2018, will map all the asteroids around Earth. Realizing the threat of an asteroid collisi...

     In 1929, American astronomer Edwin Hubble studied a number of exploding stars, or supernova, and determined that the universe was expanding. The notion that distant galaxies were moving away from ours was a radical idea. It seemed obvious to astronomers that gravity—the mutual attraction between all matter—would affect the expansion process. But how? Would the pull of gravity completely halt the expansion of the universe? Could the universe stop expanding and then reverse itself back toward us? Or would the universe eventually escape the gravitational effect and continue to expand? The universe may be expanding, reasoned the scientific community, but its expansion was surely slowed by the forceful effects of gravity. Fast forward nearly 70 years to a time when two teams of astrophysicists—one led by Saul Perlmutter at the Lawrence Berkeley National Laboratory and the other by Brian Schmidt at Australian National University—began studying supernovas to calculate the ...

     At one time, the storm was at least 20,000 miles (32,000 km) in diameter and big enough to envelop three Earths. It is similar to a hurricane on Earth, rotating counterclockwise with a maximum windspeed of 268 miles per hour (430 km/h), almost twice as fast as the worst hurricanes on Earth. Historic observations date as far back as the 1600s. Since then, the spot has changed, fluctuating between a deep red and a pale salmon color. Laboratory experiments suggest that complex organic molecules, red phosphorus, and other sulfur compounds cause the vibrant color.       But since the 1930s, the storm has shrunk to half its largest diameter. Even though it may be dwindling in size, the longevity and enormity of our solar system’s biggest storm is full of mystery. The reason for the persistence of the Great Red Spot is unknown, but presumably comes from the fact that it never moves over land, unlike hurricanes on Earth. Jupiter is composed of hydrogen and a ...

   The shape of our galaxy is nothing special. Among the other clusters of stars that can be easily observed from our corner of the universe, a few are blobby and egg-shaped, but more than two-thirds are so-called “disc galaxies” whose stars have settled into flat orbits, as if traveling along the surface of a giant vinyl record.            Almost every disc galaxy looks at least a bit like ours, with stars that group together into spiral arms. What causes the spirals? “A galaxy is constantly bombarded by satellite galaxies,” says Chris Purcell of West Virginia University. When one galaxy passes by or through another, the resulting forces can send a shock wave throughout its structure, bunching stars together in spindly shapes that rotate around the center. “It’s essentially a vibration that travels gravitationally throughout the disc,” Purcell explains. As a galaxy ages, these perturbations tend to mount, and the disc goes from being thin, circul...

     As far back as the 1930s, evidence for the existence of a “dark matter” in the universe began to emerge. Swiss astronomer Fritz Zwicky measured the velocities of several galaxies in the Coma cluster, a group of more than 1,000 identified galaxies, and concluded that many of them were moving so fast that they should have escaped the gravitational pull of the other galaxies. Zwicky, and other astronomers noticing the same phenomenon, concluded “that something we have yet to detect is providing these galaxies with additional mass, which generates the extra gravity they need to stay intact. This “something” is invisible— hence the nickname “dark matter.” But exactly what is dark matter, and what is it made of?          NASA notes that we’re “more certain what dark matter is not than we are what it is.” Dark matter does not take the form of stars and planets we can see, yet it  constitutes about 27 percent of all the matter in the universe. I...

    What happens when the human population outpaces the resources of our planet? Many people wonder if moving humankind to another planet is possible. Scientists agree that of all the other planets in our solar system, Mars would be the most habitable. But that’s not saying much. If the goal is to create a self-sustaining Martian world, life will be difficult and dangerous.     Mars has some similarities to Earth. Its axial tilt is about the same, so Mars deexperiences similar seasons; however, its orbital eccentricity is much larger, so the length of the seasons varies and a year lasts almost twice as long as on Earth. The length of a day is about the same. The desert terrain is similar to some regions on Earth. However, despite these similarities, Mars is a completely hostile environment.     There is no breathable air and very little air pressure. Lower gravity presents problems for prolonged settlement. Temperatures vary widely: While they may climb as ...

         Imagine a single blast of energy powerful enough to destroy the equivalent of a thousand Earths in a second. Explosions of that magnitude happen in the universe every day, thanks to gamma ray bursts. Scientists didn’t know these extreme bursts of energy existed until the 1960s, when satellites designed to monitor nuclear weapons tests on Earth picked up the phenomenon. A long the electromagnetic spectrum of energy—which includes radio waves, ultraviolet waves, and visible light— gamma rays are the most powerful. A gamma ray burst is a focused stream of energy that can last from just a few seconds to several minutes. Just one 10- second burst releases more energy than our Sun will produce over its 10-billion-year lifetime. Most bursts occur outside theMilky Way in galaxies with many massive stars.     Today scientists have two main theories to explain what might cause a gamma ray burst. One idea involves neutron stars. If two of these massively...

     The aurora appears as a curtain, an arc or a spiral, usually following the lines of Earth’s magnetic field. Most displays are green, but strong occurrences can be red, violet, and white. For most of human history, the colors were a source of mystery. Northern cultures created legends about the lights, often associating them with life after death. The Inuit believed the spirits of their ancestors were dancing across the sky, and in Norse mythology, the aurora was a bridge of fire connecting the gods to the heavens. But by the 1880s, scientists suspected a connection between the northern lights, as they are also known, and the Sun.        The temperature above the surface of the Sun is millions of degrees Celsius, causing frequent and violent collisions among gas molecules. Electrons and protons thrown free by the collisions hurtle outward from the Sun’s rotation and escape through holes in the magnetic field. Solar wind carries the charged particle...

    You probably don’t think about it regularly, but in the back of your mind you know that gravity affects your every move. You see it at work each time you watch the rain fall, throw a ball into the air, or drop a pencil. Without this omnipresent, invisible “force” you would fly off into space, along with everything else on Earth. The universe itself would become a chaotic landscape of planetary bodies aimlessly hurtling through space and often colliding.  What is gravity and how does it work? The  answer is simple: We’re not quite sure. To  this day, gravity’s mystery hasn’t been  solved.      In 1687, Isaac Newton described gravity  as a force, claiming that any two objects in  the universe exert a force of attraction  upon each other. The Sun exerts gravity on  all the planets, keeping them in orbit.  Similarly, the planets exert gravity on the  Sun and on all the other planets as well.  The...

    The fictional simulator located on starships and starbases gave the Starfleet crew entertainment, a training mechanism, and a way to investigate mysteries. In the science fiction realm, the holodeck was a room equipped with a hologrid containing multidirectional holographic diodes, using photons and force fields to create a realistic environment. In an otherwise empty room, “solid” props and characters interacted with a holographic background capable of creating any scenario possible. Science has a different name—“tele-immersion”—for Star Trek’s holodeck. The technology for this interactive virtual world is closer than you might think.           Some scientists and researchers think we will have holodecks as early as 2024. While the technology exists to create one already, it would be crude compared to the one on Star Trek. Taking the science fiction genre out of the equation, holodecks are simply an attempt by Hollywood and video game makers to m...

    A supernova is a stellar explosion. Incredibly strong, a typical supernova can outshine an entire galaxy at its peak, ejecting a Sun’s worth of stellar mass at a significant fraction of the speed of light within seconds. And here’s the harsh reality: A supernova, if it were close enough, could certainly spell the end of civilization and, perhaps, wipe out all life on Earth. As heavy radioactive elements in the ejected matter decayed, they would produce gamma rays.           These gamma rays would be powerful enough to convert our ozone layer into nitrogen oxides and pure nitrogen, neither of which would protect us from the radiation of space.           The bombardment of solar and cosmic rays would destroy key parts of the ecosystem, especially plankton and coral reefs. With the collapse of these systems, the oceanic biome would likely collapse, leading to a mass extinction that would vibrate across the food chain...

     Scientists have identified seven major rings, named for the first seven letters of the alphabet, which are made up of many more, thinner “ringlets.” Although they appear solid from a distance, each ring is actually composed of individual bits of ice along with dust and fragments of space rock. These particles range in size from a tiny speck to perhaps as much as one halfmile (0.8 km) wide. The space objects that form the rings whiz around the planet at high speeds—up to thousands of miles per hour.   How Saturn got its rings is still open to debate. The NASA spacecraft Cassini, which reached Saturn in 2004, could provide answers. Cassini’s research suggests that the outer E Ring is formed, in large part, from pieces of ice that break off from Enceladus, one of Saturn’s known 53 moons. Closer to the planet’s surface, some rings seem to be formed by particles that break off other moons when small meteoroids collide with them.    Several theories that exp...

 

       We understand the chemistry, the physical process, of blushing, butwe blush remains an elusive mystery to researchers. The physiology of blushing is quite simple. When you’re embarrassed, your adrenal glands and certain neurons of the central nervous system release the hormone adrenaline. The general effect of adrenaline is to prepare the body for the “fight or flight” response: increasing heart rate and blood pressure, enlarging the pupil of the eye, and increasing blood flow and oxygen to the muscles, among other consequences. When you experience the stress of embarrassment, adrenaline causes the veins in your face to dilate, or widen, allowing more blood to flow through them. The increased presence of blood in your face makes your cheeks feel warm and creates the reddened look that signals to others you’re embarrassed.     Blushing triggered by embarrassment is a one-of-a-kind phenomenon: It is exclusive to humans, and it does not happen anywhere ...

      Scientists say there could be a reason why you don’t remember what you ate for breakfast last week but can vividly describe your first day of kindergarten. Emotional meaning attached to a memory makes it stick in a way that everyday details can’t. But memories aren’t just about the past. They help us learn and make decisions about the future. Neuroscientists do not completely understand the physical representation of memories in the brain. Neurons, or brain cells, communicate with each other through electrochemical pathways. An electrical impulse travels down the outgoing branch called an axon, where it stimulates fingers known as dendrites at the end, releasing neurotransmitters. These tiny molecules send messages that incoming branches pick up. The space between these branches is called a synapse.    The reconstruction of a past experience happens through synchronous firing of neurons involved in the original experience. A memory is not a static entity ...

     We hear laughter all the time—froma  giggle to a snicker to a full-blown belly laugh. Laughter is undoubtedlya common human behavior, yet it has vexed scientists for centuries. To this day, the question “Why do we laugh?” remains a much-debated topic.    An apparent answer to the question would be that we laugh when we think something is funny. In this case, laughter—the contractions of facial muscles accompanied by an audible sound ranging from a quiet titter to a loud cackle—would be the physiological response to humor. This might be the answer, but it’s not the full story. The reasons that we need this response are more complicated than you’d think.        As it turns out, studying laughter is no Joking matter, according to Robert R.P rovine, professor of psychology andn euroscience at the University of Maryland. Provine, the author of the book, has conducted numerous studies on mirth.“ Most laughter is not in response to jokes o...

     We all do it, and even some animalsa s well, when we’re ready to go to sleep and sometimes when we awake.We do it when we’re bored, and we might do it under stress. We can even catch it from another person, but as common as yawning is, scientists have struggled to explain why we yawn. Recent research suggests some possible explanations.       One theory among chasmologists—scientists who study yawning—is that the act is a form of social behavior. Contagious yawns are quite common—about half the people who see or hear a yawn will yawn too. Christian Hess of the University of Bern in Switzerland thinks the easy spread of yawns helped early humans learn to synchronize their desire to go to sleep and awake at the same time, allowing them to coordinate their daily activities. Maryland psychologist Robert Provine is one chasmologist who thinks a yawn stirs up our brains. So when we’re sleepy, a yawn wakes us up, and if we need mental sharpness to deal with s...

    Typically, the immune system treats peanuts as safe, but some scientists believe that early and heavy exposure to peanutladen products might cause the immune system to misidentify them as dangerous. This theory is strengthened by the fact that 8 out of 10 allergic kids have a reaction the first time they eat a peanut, indicating a previous indirect exposure, possibly even in the womb or through breast milk. Theories about peanut allergies abound and most involve an overactive immune system. “We have done such a good job of eliminating the threats that the immune system is supposed to manage that it’s looking for something to do,” says Anne Muñoz-Furlong, former CEO of the nonprofit Food Allergy and Anaphylaxis Network. Parents today feed their kids a lot of ready-made snacks, many of which contain peanuts or their derivatives.   “We’re bombarding the immune system with these [food-based] allergens, so it’s attacking those instead.” Indeed, food allergies in gener...