100 Mysteries of Science Explained Read online

  Physicists continue to ponder the possibilities of faster-than-light travel (FLT) and what it means for space exploration and our universe. The first example of faster-than-light speeds in popular culture occurred in the television series Star Trek, when “warp drive” sent spaceships traveling billions of light-years away in a matter of seconds. If this were possible, those space travelers might return to their original location and find that time had progressed at its usual speed, meaning 50 years may have passed during the short time the ship was absent, simulating time travel.

  While most people view time as a constant, Einstein proved that time is relative to how fast an object moves according to its surroundings. Einstein pointed out that time is not a consistent flowing entity, but linked with space, and so the faster one travels through space, the more the perception of time changes, a phenomenon called time dilation. If an astronaut can somehow travel close to the speed of light, he will experience time differently than his friends left behind on Earth traveling at the usual speed. Time will pass much slower for the astronaut, and when he returns to Earth, his friends will have aged faster. However, the laws of physics state that the speed of light is constant, represented by c in Einstein’s famous equation E = mc. The speed of light in a vacuum is 186,000 miles per second (299,337 km/h), and while some physicists have identified processes like quantum entanglement that travel faster than light, they do not carry mass or information. For a particle with mass, reaching the speed of light would require infinite acceleration and therefore infinite energy—an unrealistic accomplishment.

  In 2011, physicists at the CERN institute in Switzerland thought they were close to a FLT discovery. A new subatomic particle called the neutrino, which carried a very small mass, appeared to travel faster than the speed of light. Their experiment launched particles from Switzerland to Italy, and the neutrinos arrived in Italy in record time, intriguing the world with thoughts of time travel and visits to distant galaxies. Unfortunately for CERN, the experiment was flawed. One cable was not properly connected, resulting in incorrect measurements.

  According to Einstein’s theory, objects with mass cannot exceed the speed of light because they would require an infinite amount of energy—be they spaceships or neutrinos. Even in all theoretical scenarios in which we travel faster than light, we can never travel backward in time, only forward. However, many scientists believe that traveling into the future is still a possibility that just needs more study. Wormholes, a theoretical passage through space-time that connects distant points in the universe, are attractive starting points for these theories. But however enticing the possibilities, it seems that success is still light-years away.

  Will We Ever Be Able to Harness Nuclear Fusion?

  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 nuclear fusion is “always 30 years away.” What’s changed? Recent breakthroughs indicate that the future of fusion is brighter than it has been in some time.

  Physicists since the 1950s have been seeking to harness the power of the Sun. As it turns out, birthing a miniature star in a lab and keeping it under control is a difficult undertaking. The fusion reaction requires more energy than the reaction itself produces. It wasn’t until October 2013 that any project broke even, when the National Ignition Facility (NIF) in California produced more energy than it consumed.

  The success at the NIF, although exciting, is just another step on a long journey. To be commercially viable and to overcome basic inefficiencies in the conversion of raw energy into electricity, the reaction must continually produce 10 times the amount of power that goes into it. Candidates for exceeding this threshold include the International Thermonuclear Experimental Reaction (known as ITER, pronounced “eater”), a project with the backing of seven countries that should come online by the end of the decade.

  Recently, aerospace and technology giant Lockheed Martin’s covert Skunkworks facility has announced a breakthrough in fusion technology that may yield results within the decade.

  Secrecy still surrounds the research, but scientists hope that covert research facilities like Skunkworks will make “the impossible” possible.

  Does Spontaneous Human Combustion Ever Happen—and How?

  In 1980, Henry Thomas, a 73-year-old 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-year-old 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 scientists would argue that humans cannot catch fire without an apparent cause. In fact, in the more than 200 cases of spontaneous human combustion (SHC) that have been reported worldwide, the true causes of death are far less fanciful than SHC.

  In a study of 30 cases of alleged SHC, investigators Joe Nickell and John Fischer showed that candles, lamps, fireplaces, cigarettes, and other sources of heat were the likely reasons for ignition. Clothing, chair stuffing, and floor coverings usually provided additional fuel sources to sustain the fire.

  One of the most commonly accepted explanations for alleged SHC is a phenomenon called the “wick effect.” This theory suggests that an ignition source, such as a lit cigarette, will burn through the victim’s clothing and into the skin. This releases body fat, which is absorbed into the clothing and burns like a candlewick. The fire will burn until the body’s fat and the clothing are both consumed. Scientists believe such a “self-contained” fire is the reason victims’ bodies are incinerated, yet their surroundings barely suffer damage.

  “SHC is a non-explanation for bizarre burning deaths, no better than positing the attack of a fiery demon,” says forensic analyst Nickell, “because there is not only no scientifically authenticated case of SHC but no credible mechanism by which it could happen.”

  Chapter 2

  Space

  Fermi Bubbles extend 50,000 light-years, roughly half of the Milky Way’s diameter.

  What Are Fermi Bubbles?

  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 shortest-wavelength, 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 high-energy gamma rays, yet there is no apparent cause for them that far from the galactic center. Lastly, the parts of the Fermi bubbles nearest the nucleus of the Milky Way contain both gamma rays and microwaves, but as the bubbles extend farther out, only the gamma rays are detectable.

  Theorists have offered several explanations for the unusual structures. The two most predominant theories both suggest the bubbles were formed by a large, rapid energy release.

  One possibility claims that enormous streams or jets of accelerated particles originating and blasting out of the supermassive black hole at the center of the Milky Way created the Fermi bubbles. Astronomers have observed such a phenomenon in other galaxies, and while it is unknown if the Milky Way black hole has an active jet today, it may have had one millions of years ago.

  Another commonly held theory argues that the Fermi bubbles were created during star formations over a period of millions or even billions of years. The gas ejections created from bursts of star formations, similar to the ones that produced huge star clusters in the Milky Way, theoretically rode massive galactic winds out to far-off distances and are held there by powerful magnetic forces.

  Scientists are eager to unravel the mystery of the Fermi bubbles’ origin. “Whatever the energy source behind these huge bubbles may be,” says David N. Spergel, a theoretical astrophysicist at Princeton University, “it is connected to the many deep questions in astrophysics.”

  Images taken with the Hubble Space Telescope show the Crab Nebula, the remains of a massive star explosion. In the center, the pulsar rotates approximately 30 times per second.

  Why Do Pulsars Pulse?

  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, including the Crab Pulsar, ruled out the alien emissions hypothesis.

  Today, scientists know that pulsars are generated by rotating neutron stars. The stars rotate quickly due to the conservation of angular momentum: When a large rotating body collapses, the remaining matter spins at a much higher rate, akin to the effect spinning figure skaters experience when they hold their arms close against their body. Some of these neutron stars have strong magnetic fields—in the case of pulsars, about 1 trillion times as strong as Earth’s—and emit a beam of radiation that coincides with their magnetic poles. This radiation can be the result of the quickly spinning star’s slowing momentum, the accretion of matter as it falls into the star, or the twisting of the star’s magnetic field. This magnetic axis is not always the same as the axis of rotation. When they do not coincide, the beam of radiation wobbles about the rotational axis. The result of this wobbling is a beam of radiation that, when viewed from Earth, seems to be pulsating.

  Since Burnell and Hewish first discovered pulsars, astronomers have identified nearly 2,000 more, emitting visible light, X-rays, and, in some cases, only gamma rays. And while we have a general idea of why pulsars pulse, astrophysicists believe that there is still much more to discover.

  Does Alien Life Exist?

  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 report highlighted one planet in particular, about 150 light-years away from Earth, that seemed like a possible candidate to support the development of alien life. It orbits a star called Epic 201367065, which is about half the size and mass of Earth’s Sun.

  While some people wonder about the complexity of possible alien life-forms, some scientists think it makes more sense to imagine “aliens” as simple microorganisms. Life on Earth started out as single cells, and life on other planets might still be at that stage of evolution. And as Hawking notes, Earth was lucky to avoid a cataclysmic collision with an asteroid or comet in the past 70 million years. Other planets could have had their early life-forms wiped out in such a cosmic crash.

  NASA research done in the 1990s found what scientists thought were signs of ancient bacteria on a meteorite from Mars that reached Earth in 1984. Other scientists, though, dismissed the claim, and no one has proved the existence of microbes on Mars, now or in the past.

  The possibility that the Red Planet once had water, however, was raised in 2014 after NASA scientists studied another meteorite from the planet that reached Earth. That same year, the NASA rovers, Curiosity and Opportunity, were able to capture high-resolution images of what are believed to be ancient riverbeds on the surface of Mars. The presence of water raises the possibility of biological activity as well. So does the discovery of large amounts of methane, which Curiosity also detected. The methane, however, could be the product of geochemical processes, rather than biological.

  For now, scientists can feel confident in the odds that alien life does or did at some point exist, but without any idea of its form. As for the possibility of intelligent alien life ever visiting us on planet Earth, Hawking had this insight: The arrival of aliens could turn out to be much like Christopher Columbus’s arrival in the Americas—and be followed by a steady stream of conquistadors and explorers from another universe. And we all know how that turned out for the people already living there.

  Why Don’t Moons Have Moons

  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 far-off 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. Most planet-hunting methods—such as spotting one as it passes a large star—lend themselves to detecting huge, Jupiter-like planets, or sometimes Earth-sized, rocky planets, but not their moons.

  Even if astronomers spot a moon with a moon, it probably won’t last long. “Tidal
forces from the parent planet will tend, over time, to destabilize the orbit of the moon’s moon, eventually pulling it out of orbit,” says Webster Cash, a professor at the University of Colorado’s Center for Astrophysics and Space Astronomy. “A moon’s moon will tend to be a short-lived phenomenon.”

  What Is the Moon Illusion?

  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 play a big role in the appearance of the Moon. When the Moon is placed as a backdrop against objects of known heights—such as trees, cars, or buildings—it appears larger than when it is isolated in the sky. In one experiment, researchers asked participants to view the horizon Moon through a cardboard tube, which caused background objects to disappear. They found the Moon seemed to shrink to a size similar to the zenith Moon.