But engineers aren’t yet sure how to manufacture a nanotube tether (and even if they could, it’s not clear that it would be strong enough to support a space elevator). If they can build a strong enough tether, engineers will still need to overcome additional barriers, including how to avoid meteorites, space junk, and the inevitable swaying that will occur as a craft inches up the tether and drags against Earth’s natural rotation.
Despite the barriers, the potential of a space elevator remains alluring. Sending a payload into orbit is currently an expensive and inefficient undertaking. If we could do away with the rocket itself, then (relatively) cheap exploration of our solar system could be within our grasp.
How Does Gravity Work?
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 strength of these relationships is determined by the mass of the objects and the distance between them. The greater the mass of the two objects and the closer the objects are to each other, the stronger the pull of gravity.
For more than 200 years, Newton’s theory of gravity went unchallenged. Then enter Albert Einstein. In early 1915, Einstein, in his groundbreaking general theory of relativity, explained that gravity is a curvature in the space-time continuum, or the “shape” of space-time. The mass of an object, Einstein claimed, causes the space around it to bend, or curve.
To understand the phenomenon, imagine a heavy ball sitting on a rubber sheet. The area occupied by the ball sags, or becomes distorted, due to the mass of the ball. Other smaller balls on the sheet roll in toward the heavier object because the heavy ball warps the sheet. According to Einstein, celestial bodies are not feeling the force of gravity, but rather following the natural curvature of time-space.
A recent alternative hypothesis to Einstein’s theory of gravity states that particles called gravitons, emitted by Earth, cause a gravitational force between objects. But gravitons have never been observed and, to date, remain hypothetical. Yet another idea holds that gravity is the result of gravitational waves, generated by an interaction between two or more masses, such as the merge of two galaxies or the orbit of two black holes. Like gravitons, however, gravitational waves have never been detected.
And so the great mystery of gravity remains unsolved. And without discovering its secret, humankind may never truly comprehend how the universe works.
As for many of us here on earth, the life span and ultimate fate of a star depends largely on its mass. The heaviest of stars go out with a bang. We call this bang a “supernova.”
How Do Stars Explode?
Supernovas can occur in one of two ways: through a process of runaway nuclear fusion or through a rapid collapse of the star’s core.
The first process occurs in binary star systems where at least one star is a white dwarf, a dense, aging star that can no longer support nuclear fusion. The second star can be another white dwarf, a red giant, or a main sequence star such as our own Sun, that fuses hydrogen atoms to form helium atoms at its core. In either case, the white dwarf siphons off (or collides with) the mass of its companion star, reigniting nuclear fusion. Once the white dwarf reignites, it gets so hot so fast that it blows apart, outshining an entire galaxy and leaving no remnant behind.
Less luminous, though no less spectacular, are core collapse supernovas. Instead of exploding in a runaway fusion reaction, this type of supernova occurs when the star’s fusion reaction grinds to a halt. For most of a star’s life, it burns by fusing hydrogen atoms. This is the same process that ignites thermonuclear weapons. Eventually, the star converts most of its hydrogen into helium. The star then must fuel itself by fusing helium into carbon. If the star is heavy enough—about eight times the mass of the Sun—it will then proceed to fuse carbon into neon and helium. The star continues to fuse heavier and heavier elements until it reaches the iron phase.
It’s during the iron phase that things get really heavy. Fusing iron does not produce more energy—in fact, iron fusion requires energy. Without the fusion pressure that counteracted the star’s gravity, the core of the star, which is approximately the size of Earth, collapses into a space less than 10 miles (16 km) in diameter at about one-quarter light speed. When the stellar mass bounces back into space (crashing into the outer shell of the doomed star), the resultant shock wave is what we on Earth witness as a supernova.
Upon going supernova, the star may tear itself apart entirely or leave behind an extremely dense neutron star. If the core of the star is heavy enough, the supernova leaves behind one of the most mysterious objects in the known universe: a black hole.
In the night skies above a certain latitude, stargazers see an awesome display of shimmering colored lights known as the Aurora Borealis. Nations bordering the arctic ocean get the best show, while the southern regions of the Southern Hemisphere get a similar display, named the Aurora Australis.
What Causes the Aurora Borealis
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 particles, most of which deflect off Earth’s magnetic field. However, near the North and South Pole, the magnetic field is weaker, allowing some particles to enter the atmosphere. When the charged particles from the Sun strike the atoms and molecules in Earth’s atmosphere, they excite those atoms. An excited atom is one whose electrons move to high-energy orbits, and in the process the atom releases a particle of light, or photon. Different gases in the atmosphere give off light of different colors. Oxygen causes a green display and nitrogen produces red or blue colors. We perceive the collisions between solar particles and atmosphere gases as the northern lights.
Many tourists trek to the northern and southern poles of Earth to catch a glimpse of the auroras, now considered one of the seven wonders of the natural world. And even though science can explain the once-mysterious phenomenon, the dazzling display of lights still provokes magical thoughts of dancing ancestors and bridges to the world beyond.
Star Trek fans will be happy to hear that a holodeck is not that far away from reality.
Is a Holodeck Possible?
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 move entertainment closer to reality. Instead of slouching on a couch during a movie or getting a thumb workout during a session of Halo, a player can maneuver a battle site while interacting with actors or run around the bases after hitting a grand slam at a New York Yankees game.
Many of the difficulties of creating a holodeck have already been solved. For example, the U.S. Army has created a floor called an “omnidirectional treadmill” that allows users to walk around a room without running into walls. Microsoft is at the forefront of this technology, filing several patents for holodecks. The IllumiRoom, a Microsoft project, can manipulate surroundings and make furniture disappear. Lightspace is a digital chandelier by Microsoft that can detect people and objects in a room and display images from the ceiling that cover the walls and floor. And in 2014, scientists at the University of Illinois created CAVE2, which uses 8-foot-(2.4-m)-high screens that cover 320 degrees of a room and can model global weather patterns, study the effects of drugs, and help doctors practice surgery.
Researchers have already created a 3-D reality. The difficulty is creating a realistic interactive reality, where a participant can shake the hand of a coworker thousands of miles away or hit a home run that feels exactly like the real-life alternative. If science does master the holodeck, there may be significant changes in how we function. TVs, even flat-screen, HD, and “smart” devices, may become obsolete as people opt for a real-world experience. Business travel could decline if holodecks become less expensive than airplane flights and hotels. In fact, many people may opt never to leave the house again since any experience they desire can virtually drop into their living room.
While several planets in earth’s galaxy have rings, none are as large and impressive as the rings of Saturn.
How Did Saturn Get Its Rings?
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 half-mile (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 explain how some rings formed rest on the Roche limit, which is based on a calculation first made by the 19th-century French astronomer Edouard Roche. In simple terms, the Roche limit means gravity will cause a satellite orbiting a planet to break apart if it approaches within a certain distance of the planet. The rings may be pieces of the material used to form Saturn’s moon. It’s possible some of the matter may have traveled within the Roche limit, the small pieces coming together in ring form. Alternatively, a small moon might have drifted within the Roche limit and Saturn’s gravitational force pulled it apart, creating space debris that formed a ring.
The Cassini mission will last until at least September 2017. Scientists hope the spacecraft will provide more answers about Saturn and its rings.
An artist’s drawing of gamma rays hitting earth’s atmosphere, where they would eventually deplete the ozone layer, allowing in ultra-violet radiation from the sun. This effect would damage small life-forms, disrupt the food chain and possibly bring about mass extinction.
Could a Supernova Wipe Out Life on Earth
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. Given long enough exposure, the bombardment of cosmic and solar rays would threaten and, eventually, wipe out surface life—including humankind—everywhere. If any life survived, it would likely be microbes hiding deep inside Earth’s crust.
As scary as this scenario is, it is also extremely unlikely. In cosmic terms, that supernova would have to be awfully close to cause any real damage. Powerful, Type Ia supernovas dim significantly beyond 75 light-years, and less powerful Type II supernovas are unlikely to cause significant damage at a distance greater than 25 light-years. Thankfully, there are no stars close enough and massive enough to go supernova. The nearest candidate is IK Pegasi, safely 150 light-years away (and creeping even further away from us).
Luckily for us, of the 200 to 400 million stars in the Milky Way, an average of three go supernova every century. This isn’t something we have to worry about any time soon.
CHAPTER 3
Human Body
Charles Darwin called blushing “the most peculiar and most human of all expressions.” To the average person, blushing only serves to make an embarrassing situation even more unpleasant. To scientists, however, blushing from embarrassment is a unique physiological and emotional phenomenon.
Why Do We Blush?
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 else in your body. Why is this reaction so specific? Why have humans developed this unique response to embarrassment?
Science does not yet have all the answers, but recent studies suggest that blushing serves a functional purpose, having evolved as a means of establishing social relationships. In a study conducted in 2009, a team of Dutch psychologists led by Corine Kijk, Peter de Jong, and Madelon Peters discovered that blushing “serves to signal the actor’s genuine regret or remorse over a wrongdoing.” In effect, blushing functions as a nonverbal “I’m sorry” for committing an embarrassing act or breaching a societal norm. It thereby mitigates “the negative social impression that was caused by the infraction.” According to the researchers, your blushing makes others perceive you h
ave acknowledged your blunder and learned from your mistake.
The Dutch study concluded with some helpful advice: “Our results showed that in the context of transgressions and mishaps, blushing is a helpful bodily signal with face-saving properties. It seems therefore unwise to hide the blush or to try not to blush in these types of contexts.”
What is the Evolutionary Purpose of Tickling?
You probably know that you can’t tickle yourself. And although you might be able to tickle a total stranger, your brain strongly discourages you from doing something so socially awkward.
These facts offer insight into tickling’s evolutionary purpose, says Robert R. Provine, a neuroscientist at the University of Maryland and the author of the book. Tickling, he says, is a mechanism for social bonding between close companions, helping to forge relationships between family members and friends.
Laughter in response to tickling kicks in during the first few months of life. “It’s one of the first forms of communication between babies and their caregivers,” Provine says. Parents learn to tickle a baby only as long as she laughs in response. When the baby starts fussing instead, they stop. The face-to-face activity also opens the door for other interactions.
Children enthusiastically tickle each other, which some scientists say not only inspires peer bonding but also might hone reflexes and self-defense skills. In 1984, psychiatrist Donald Black of the University of Iowa noted that many ticklish parts of the body, such as the neck and the ribs, are also the most vulnerable in combat. He inferred that children learn to protect those parts during tickle fights, a relatively safe activity.
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