The Sky Handbook

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SKY HANDBOOK The

Stars & Constellations Atmospheric Phenomena Weather Clouds Air Quality Climate Change

John Watson & Michael Kerrigan


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MAKING SENSE OF OUR UNIVERSE


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The Mayans he Mayan people of Central America, as well as the Aztec of South America, developed their own astronomical models to a great degree of mathematical precision—even if they are more popularly known for their sacrificial rituals. From around 2000 CE, from Mexico to Guatemala, the Mayan cosmology thrived until the arrival of Europeans, grounded on a powerful priesthood and trading society, which built remarkable pyramidal temples within highly developed city states. Their cosmology was based on the idea of a world tree, Yakche, whose branches were the heavens, Cab, leading down through the earthly trunk, Caan, to the roots of the underworld, Xibalba. Their polytheistic culture worshipped sun, moon and many other sky and earth deities, and their astronomical skills were accurate and clearly documented. They created one of the first precise calendars; they aligned buildings with stars and

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solstice events; and they developed a base-20 number system to help them deal with the huge numbers demanded by cyclical astronomical calculations. They produced the earliest known book of the Americas, known as the Dresden Codex (bought by the German town’s library in 1739), which consists of 74 colorfully painted fig-bark pages attributed to eight or more individual scribes (who used local dyes, including the celebrated Mayan Blue). This document easily rivals the much later illuminated manuscripts of medieval Europe. It has been dated to the twelfth century CE and contains remarkably accurate astronomical tables; it also contains predictive astrological tables on the timings of floods, illness, medicinal practices and planting schedules. The Venus Table is the highlight of the codex, showing accurate readings of the movements of this especially bright planet. Venus was an important celestial marker for the Mayans, astrologically organizing life and war, as well as determining their religious calendar.

Above: An image from the Dresden Codex. Opposite left: A Mayan temple; many temples also functioned as calendars. Opposite right: El Caracol (the snail), a Mayan observatory at Chitzen Itza, Mexico.

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Right: A woodcut of a Ptolemy map by Johane Schnitzer (Ulm: Leinhart Holle, 1482). In addition to mapping the heavens, Ptolemy also devoted much of his time to mapping the Earth. His Geographia continued to be printed and used until the early Renaissance.

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Galileo (1564–1642) is known colloquially as the “Father of Science” and was a great Italian Renaissance astronomer and teacher based in Padua. Galileo Galilei, to give him his full, harmonious name, was a Copernican who developed the telescope as a means of observing the stars and with which he discovered the moons of Jupiter and the phases of Venus, which proved that the Earth must go around the Sun, rather than vice-versa. He was the first astronomer to stand up against religious restraints on science in Roman Catholic Europe, when he was put under Papal trial in 1633. His heliocentric views ran counter to the official stance of the Vatican, which effectively censored his work and kept him under house arrest until his death in 1642.

Above left: Galileo’s sketches of the Moon revealed that the surface was mountainous. Above right: Galileo’s observations of the moons of Jupiter upset the notion that all celestial bodies must revolve around the Earth. Left: Galileo Galilei.


Right: Johannes Kepler

MATHEMATICAL MUSIC

Galileo and Kepler shared another inter est: music. But rather than playing instruments, they were interested in the mathematical and physical aspects of musical scales and instruments. Galileo came by this interest naturally: his father, an accomplished lute player, established a important physical law determining the connection between the tension of a string and its musical pitch.

Johannes Kepler (1571–1630) was a genius of mathematics and astronomy who finally grounded the whole modern Copernican revolution in undeniable scientific proof. He was a pupil and protégé of Tycho Brahe, and went on to delineate the laws of planetary motion and invented the refracting Keplerian telescope in 1611. His publications included the Mysterium Cosmographicum (“The Cosmographic Mystery”), but the most revolutionary was Astronomia Nova (“A New Astronomy”), which contains his enlightening treatise on Mars: he described the red planet moving in an ovoid, elliptical orbit and not a circular one. He also proved that these orbits were slower at their furthest reaches from the sun. This laid the foundation for exact and predictive calculations of planetary motion and for the biggest question yet: what force actually moved the planets? MAKING SENSE OF OUR UNIVERSE

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SEEING STARS: THE CONSTELLATIONS


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The Big Bang e know that the universe is expanding outward, we know that the stars and galaxies are generally moving away from each other, and with the discovery of Cosmic Microwave Background Radiation in the 1960s we know the universe has a temperature that comes from a very early hot fever. There must have been a source—a point in the universe where all this matter expansion and uniform radiation originated. It had to be a singularity, a particular point in space and time where everything came from. But what happened, and from where and how did that singularity appear? The modern echo of this early universe is now firmly believed to have originated in a singularity we call the Big Bang. It may be too big to imagine or explain properly. Some, understandably, believe it to be the “instant of God,” while others believe it to be scientifically explainable. And this might not have been the only singularity—perhaps there were billions more!

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Opposite: From time immemorial humans have looked up and seen their own shapes and stories in the patterns made by the brightest stars. Below: A night scene showing the Big Dipper and the other stars that comprise Ursa Major.

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ON THE SHOULDERS OF GIANTS

English physicist Stephen Hawking has done groundbreaking research on black e that holes. He was among the first to prov y fairl a singularities and black holes were has He common feature of our universe. ordial also argued for the existence of prim Big the mini black holes, created after s of a Bang. Despite the physical limitation king is Haw serious neuromuscular disorder, of kers one of the most celebrated thin lar modern times, and his books on popu e, Tim of science, such as A Brief History have become bestsellers.


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The Early Universe he only remnant of our early universe is the Cosmic Microwave Background Radiation—a kind of universal static that hisses everywhere but is so faint it brings no light from the Big Bang itself. The earliest we can look back is through infrared telescopes such as the Spitzer Space telescope, which has discovered faint galaxies with extremely flat light wavelengths that were formed about 500 million years after the Big Bang. It is theorized that the universe at only half a million years old was still very much a homogenous soup of gas and basic particles such as hydrogen and helium and lithium. A few million years into its youth, the universe began to develop clustered matter, like strands of woven

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LITTLE AND LARGE

y are often either Because the numbers used in astronom l, scientists often unfathomably large or incredibly smal er than writing use abbreviated forms of numbers rath al point. The all those zeros before or after the decim the smallest from following list gives the abbreviations of scale, the idea known quantity to the largest. For an , and that gram mass of a proton is approximately 1 yocto of the Earth 5970 yottagrams.

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Yocto-: 10-24√ Zepto-: 10-21 Atto-: 10-18 Femto-: 10-15 Pico: 10-12 Nano: 10-9 Micro: 10-6 Milli: 10-3 Centi: 10-2 (=0.01) Deci: 10-1 (=0.1)

Deca: 101 (=10) Hecto: 102 (=100) Kilo: 103 (=1000) Mega: 106 Giga: 109 Tera: 1012 Peta: 1015 Exa: 1018 Zeta: 1021 Yotta: 1024

Right: Our early universe was a volatile environment, with massive stars rapidly forming and dying, exploding into spectular supernovas or collapsing into black holes. The death of these early stars provided the material necessary for our universe today, including our planet and ourselves.


yarn in which early galaxies began to clump and spin—early hydrogen and helium stars began to pop up like lanterns in the night. These were supergiant megastars, often thousands of times the size of our own sun, but these unstable stars collapsed readily into supernovas and black holes. However, this was a crucial stage in our evolution as the universe was becoming more complex and developing heavier particles such as carbon, oxygen, silicon and iron, which would help build new and more vibrant stars. Supernova explosions spread these particles throughout the universe with impressive and very colorful cosmic sneezes. Eventually, we arrive 13.7 billion years into our current universe, where our own tiny Milky Way galaxy is forming about 50 new stars each solar year. From here, locked within carbon-based bodies, we stare out in wonder at the very stars from which we are made.


The Constellations e see shapes in anything, and it is no wonder when we look at the stars that we imagine our grandest fantasies and sculpt our deepest concepts. When we group stars into a shape or imaginary object we are creating an arbitrary asterism. These asterisms are only important to us; they are the fixed shapes we see in the heavens from our own particular corner in the universe. Who knows, maybe life elsewhere includes our own star Sol as the crux of some alien’s constellation important to her own way of life. Constellations are not local collections of stars in the way star clusters are; they are often relatively distant from each other, but on our flattened plane of vision they appear as fixed shapes moving in cyclic and predictable orbits around our night sky. In their first instance, they are useful navigational points as they are so distant that they remain in almost precisely the same point in the sky at the same time each year, only appearing to travel with the dip and wobble of

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STAR MAPS Star maps were created to be guides to the night sky. The one at right is a typical European star map, with elaborate drawings of the mythological character s on which the constellations are based. The first star atlas to show the entire celestial sphere was Johannes Bayer’s Uranometria (160 3). The star maps of different cultures vary with their different constellations. A trad itional Chinese star map would look muc h different than a European one. The oldest repre sentation of a constellation is thought to be an ivory tablet found in Germany. Carved with what look s like the figure of Orion, the tablet is 32,500 years old.

our Earth’s rotation. The Southern Cross in the southern hemisphere, and the Big Dipper in the northern hemisphere, point respectively to their unmoving pole stars. In cultural terms, the stars have always held our heroes and villains, and more fanciful shapes can be imagined to house otherworldly gods and creatures. The stars weave their way deeply into all our cultures as reflections of power, control, life, death and ambition. They are the shapes of our earliest narratives and sketches of our projected desires. The Zodiac is our main constellation group, dividing the ecliptic plane around which the Earth spins into twelve sections. These important asterisms are an imaginary circle of creations designed to map our emotional and physical place in the yearly cycle of life. Without them we would be intellectually impoverished, oblivious to the helpful structure of the universe and the educative patterns of our own planet’s motion through the solar system. SEEING STARS

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Gemini The Twins. Castor and Pollux, sons of Leda, represent all our dualist myths and are rich in metaphor for the heavenly search for immortality. They were two devoted mythical twins; one brother died heroically and the other beseeched the gods to allow him to follow his soulmate into death and immortality. According to some versions, Pollux was the son of Jupiter, while Castor was the son of a mortal man. In the Roman myth, Jupiter (Zeus) allows Pollux to share his immortality with Castor, with the provision that they must alternate their lives on Olympia and in Hades (heaven and the underworld).

GEMINI – THE TWINS Abbreviation: Gem Genitive: Geminorum Brightest Star: Pollux Right Ascension: 7 hours Declination: 20 degrees Visible between latitudes: 90 and -60 degrees Best seen: February

Opposite: The Medusa (left) and Eskimo nebulae, both found in the Gemini constellation.

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This constellation is a distinctive brace of stars, two sticklike bodies entwining below the two famous glowing head-stars, often invoked by sailors when they witnessed the terrifying St. Elmo’s Fire upon their boats. The first-century Roman author Pliny the Elder, who died in the 79 CE eruption of Vesuvius at Pompeii, prophesied the constellation as a protector of seafarers, unless the two stars were split by the horizon, when shipwreck would ensue. Shame he wasn’t so good with volcanoes! Gemini lies between the dimmer eastern constellation of Cancer and Taurus to the west, and contains two remarkable nebulae: the Eskimo Nebula (so called because of its parka hood of light resembling traditional Inuit wear) and the Medusa Nebula. The Geminids are a distinctive annual meteor shower seen on December 12–14, best viewed from the southern hemisphere. SEEING STARS

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This constellation is also home to the blankest area of space we know, a Cosmic Microwave Background cold spot called the Eridanus Supervoid. This is reckoned to be up to a billion light years across and is as inexplicable as it is ominous, though there is a theory that it may be the signature nothingness born of the quantum entanglement of separate universes! In mythology, Eridanus was the river that Phaeton tumbled into after an erratic stolen joyride on the chariot of Helios the sun god, scorching the earth to desert whenever he got too close, so it may represent the River Nile running through the Sahara. Pleiades Buzzing above the mass of Taurus like a swarm of fireflies, the Seven Sisters or Pleiades asterism is to the naked eye a fuzzy ball of stars that needs a good squint to split into its constituent stars. All cosmologically young blue stars, barely 100 million years old, they are doomed to drift away from each other into the cosmos. Known to the Australian Aborigines as the Campfire of the Women, they are huddled together around their fire not far from the cluster of the Hyades in Taurus, which to the Aborigines was the Campfire of the Men‌ just like the gender split at any Sunday afternoon barbecue!

Far left: An artist’s impression of Epsilon Eridani. Left: A NASA image of the Pleiades star cluster.

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Northern Circumpolar Constellations Andromeda Those rare nights when we sit outside on a clear night to gaze at the skies, we become time machines. The stars and planets and galaxies, which we see as impenetrable and distant glitterballs, are ancient firestorms of light that have traveled lightyears through the darkness of space to illuminate our skies, a little like the after-sparks of a fireworks display that happened millions of years ago. Spectacular as they are, we assume that we are living in a universe concurrent with our gaze. In fact, we are ripping backwards through the fabric of the universe! The spiral galaxy of Andromeda is the furthest we can see into time with the naked eye. It is the most distant object in our vision and wondrous for that very fact. Named after the mythological daughter of Cassiopeia, she was chained to a rock on account of her mother’s careless assertion that Andromeda was more beautiful than the Nereids (nymphs of the sea). Poseidon took umbrage to this and chained her to a rock (near the modern-day port of Jaffa, Israel) to await her fate at the hands of the terrible sea monster Cetus.

ANDROMEDA Abbreviation: And Genitive: Andromedae Brightest Star: α And Right Ascension: 1 hour Declination: 40 degrees Visible between latitudes: 90 and -40 degrees Best seen: November

Right: An artist’s depiction of the chained maiden, Andromeda.

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Less inspiringly known to astronomers as the M31 spiral cluster, Andromeda’s billon-starred mush of light has traveled 2.5 million light years to delight us. That means traveling at light speed for about 36,000 human lifetimes. Even if we traveled to woo her beauty first hand, we would have evolved into some other creature entirely! The Andromeda galaxy can be seen in her eponymous constellation between the “W” of Cassiopeia and her father Perseus. Very much a faint smudge of light hidden away in the furthest reaches of our vision, she appears like an oval jewel nestled in a maiden’s hair: stars stream back from Alpheratz, the head star of the constellation, which is itself the cornerstone of the great square of Pegasus. Perseus The champion of Zeus and father to Andromeda, he rescued his daughter from Medusa (the snake-haired Gorgon). He was the mythical king who founded the civilization of Mycenae. This constellation lies in the Milky Way underneath Cassiopeia and is rich in galaxies and clusters and nebulae. It contains the California Nebula and also the popular Double Cluster, visible through binoculars between Perseus and Cassiopeia. It is also home to the eagerly watched Perseids meteor shower in the northern hemisphere, seen on August 12 and 13 each year. It has two main stars, the brightest being Algenib, or Mirfak (the “elbow” star), and also the twitching blink of Algol—from the Arabic for “the ghoul star” and known colloquially as the Demon Star, representing the eye of the Medusa. This is an eclipsing binary system, where the brighter and fainter stars eclipse each other in turn. It was the 18th-century astronomer John Goodricke who first suggested that this was the reason why the star’s light seemed to vary in intensity. 130

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PERSEUS Abbreviation: Per Genitive: Persei Brightest Star: Îą Per Right Ascension: 3 hours Declination: 45 degrees Visible between latitudes: 90 and 35 degrees Best seen: December

Top: The Andromeda Galaxy is visible with the naked eye. Right: The Perseids meteor shower. Below: Perseus in the night sky.

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TIME AND TIDE There have not always been solar eclipses. Millions of years in the past, the Moon was too close to the Earth to properly occult the Sun; millions of years in the future, the Moon will be too far away and the Sun too big for a total solar eclipse to occur.

Right: A dramatic image of a partial solar eclipse. Below: This satellite image shows the shadow cast on our planet during an eclipse.

Eclipses rom Earth, the Sun cannot be looked at directly without strong filters, but one opportunity to observe its corona is during a total eclipse, when the Moon passes exactly over the Sun to shade its mass. These occasional conjunctions are rare and occur only a few times during a lifetime in a given place, though they occur two or three times annually and are worth traveling to see. These areas of full eclipse are known as paths of totality. As the Earth, Moon

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and Sun conjoin along one line of vision, the skies darken alarmingly, birds begin a false dawn chorus and the Sun appears to go out just like a dying match. (In ancient times it was a terrifying moment to lose the sunlight so suddenly in the middle of the day.) As the Sun disappears completely behind the moon, only a fringe of light can be seen, which is the sun's hot coronal layer. Flashing jewels of light appear on the rim of the dark moon, known as Baily's Beads, until eventually the Sun begins to swell again and reappear from the Moon's shadow.Named after the SEEING STARS

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Auroras ur most awe-inspiring light phenomenon, the aurora is a truly magical thing to witness. Auroras can be seen in the night sky in polar regions north and south of about 55 degrees. To stand agape under these lights will move anyone; it is as though you are watching the very universe at play. The Northern Lights (Aurora Borealis) and the Southern Lights (Aurora Australis) most spectacularly appear as billowing curtains of red and green light, or sometimes as glowing red, green and white pulses in the atmosphere. The Finnish refer to the Northern Lights as a mythical arctic fox sweeping its colored tail through the sky. The Cree people refer to the aurora as the dance of the spirits, and the Inuit believe them to be the home of souls that will come closer at the sound of whistling, enabling them to send messages to the deceased.

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WHEN ROME BURNS?

Above: The Northern Lights, a kind of “rainbow of the night sky.� Opposite: The colors are generated by emissions from different molecules. 238

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peror Tiberius dispatched In 37 CE, the Roman em ia, because he believed troops to the port city of Ost es. But the color effect the city was engulfed in flam se were so rare so far was a blazing aurora; the mistaken for fire. south that they were often


So what causes such a beautiful phenomenon? The answer is the Sun. The Sun is a volatile ball of energy which goes through violent cycles. The sunspot cycle, for example, emits terrific plasma storms every eleven years; the cycle corresponds to the most active cycle of auroras in our own atmosphere. As solar storms emit giant arcs and jets of plasma through space, this energy is accelerated by the Earth’s magnetic field to crash into the ionosphere at the polar regions, reacting with the it to charge particles, release electrons and emit brilliant pulses of colored light. The natural chaos of the sun’s solar wind shifts these lights constantly in flapping curtains and sudden blooms. Auroras emit VHF radio waves, and often a faint swishing noise has been reported by witnesses, like a comb through hair, or the sound of distant grass swaying in the wind. This has yet to be confirmed by scientific measurement and may just reflect the power of the phenomenon on our imagination.

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Ice Haloes & Moon Dogs ometimes when the Sun is low and the high atmosphere is full of ice crystals, a halo appears around the Sun or Moon in a 22-degree arc. This is knows as an ice halo, and on each side of its arc there can form brighter spots of light that are playfully known as sun dogs, or moon dogs when the moon creates them. On top of the halo a tangential arc can form, and beneath there often occurs a light pillar. The ice crystals, which refract and reflect the light, must all be aligned in the same direction by wind currents, so this rare phenomenon can only be observed a few times in any given year, when high atmospheric conditions are perfect. Often a counter-arc can be seen across the halo, which is known as a parhelic circle.

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THREE SUNS es, During England’s War of the Ros true the s”— troops observed “three sun s. dog sun sun accompanied by two esent The “suns” were believed to repr g the udin incl , the Yorkist commanders r, afte rtly future Edward IV. Sho at the Edward won a decisive victory Battle of Mortimer.

Above: Sun dogs and ice haloes. The cetnral sun is the real one; the ice halo that surrounds it creates the sun dogs. Opposite: A close-up of an ice halo. Left: An image of gegenschein, captured by a NASA photographer. Gegenschein is so faint that it can rarely be seen with the naked eye, and only on a dark night in a dark region of the sky.

Zodiacal Light & Gegenschein f you look long enough after sunset, or just before sunrise, along the ecliptic line of the zodiac and the Sun’s path, a slight glow can appear briefly as a faint triangle of blue/white light. This is known as zodiacal light and is the sun’s reflection off cosmically distant dust particles and collision debris in space. It is not to be confused with any atmospheric glows, which tend toward the red spectrum. Another example of this kind of cosmic reflection is Gegenschein, which is a weak glow of light in the night sky directly opposite the sun’s position. Again, this is dust reflection. Its name is the German for “counter shine.”

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Medium-Level Clouds etween heights of about 1.2 and 3.6 miles (2 and 6km) in the atmosphere, cloud formations occur in three main forms: altostratus, altocumulus and nimbostratus.

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Above: Gray altostratus clouds, signaling rain or snow to come. Opposite left: A dramatic sunset created by a bank of altocumulus clouds. Opposite right: Threatening nimbostratus clouds form when the precipitation predicted by altostratus clouds is about to arrive. 252

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Altostratus clouds are rather dull, often gray or steely blue masses of indistinct and uniform cloud. They are formed of mediumlevel ice and water droplets, and often snow. They do allow some sunlight through, giving it the appearance of a diminished star, but sometimes blot it out entirely. Altostratus is a moist layer of rising cloud associated with oncoming precipitation, as it forms from a rising warm-air mass above a cold front.


Altocumulus is responsible for our most dramatic skies, as the various formations of medium-level fluffy clouds take on the color of the sun setting and rising. They form wide sheets of regular splotches of cloud, as though an artist has applied thick brushstrokes to the canvas of the sky. There are many varieties, but all display a regular repetition, and they are sometimes stretched by wind patterns into remarkable mackerel-striped skies or lenticular formations. Nimbostratus is a slightly lower middle-level cloud that we see during long periods of frontal rain systems. Like altostratus, it contains a lot of moisture and sinks toward the ground as a dark, featureless layer bearing heavy precipitation. Nimbostratus forms readily into bands along the frontal lines of weather systems and passes in dull gray pulses over us, punctuated by lighter spells of more diffuse, pale, grayish cloud. The clouds form and condense most readily from altostratus bands into ragged, tumbling rain clouds. SOMETHING IN THE AIR

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Airborne: The Natural Principles of Flight Buoyancy Gravity is a universal law, yet some laws are more universal than others. In air, just as in water, objects that are less dense than the matter they displace will be forced upward—or, as we would call it, float. Hence the buoyancy of the airship, filled with helium. Its frame; its cover; its gondola—and the people it contains: in total, these will add up to a considerable amount of weight. But, given the lightness of the lift gas contained in the envelope, the mass of the structure as a whole is less than that of the amount of air whose place it takes.

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So Much Hot Air An airship flies because it is lighter than air, but it can only be so because of its lift gas. Yet paradoxically, air itself may be lighter than air, at least temporarily. When its temperature rises, air becomes less dense; hence the heat shimmer we see above a sunbaked highway. Humans have learned to harness this buoyancy in the hot-air balloon, whose lift gas is simply air—but heated to a slightly higher temperature than the air in the surrounding sky. Again, air is not an empty space, but a fluid—and one that is always on the move. When, for example, a household radiator or heater warms the air immediately above it, that air becomes less dense and rises; cooler air then presses in to take its place. As that air is warmed and ascends in its turn a convection current is created, and by slow degrees the prevailing temperature in the whole room is raised. Convection currents are created outdoors as well,

Opposite: A 1901 postcard showing a Brazilian airship flying over Paris. Right: Hang gliders soar past mountains in North Carolina. Far right: Paper floating over a radiator, a result of the convection current created when the air over the radiator becomes warmer than surrounding air.

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Above: Octave Chanute with his glider. Top: Otto Lilienthal and one of his gliders Right: Onlookers watching Lilienthal. Opposite: A modern hang-glider.

when the rays of the sun heat up the ground. Air that comes into contact with this surface is warmed and begins to rise. Cooler air is drawn in and warmed: again, it pushes upward in its turn in what becomes a cycle. As we saw in Chapter 3 above, the currents created by the warming of large areas of sea give rise to the winds and breezes that blow all over the Earth’s surface. Within the system, however, at the “micro” level, convection currents are constantly being formed, strengthening and weakening with the coming and going of the sun. Only gently at first in the early morning, maybe, but more strongly as the day goes on and a steady updraft of warm air, known 300

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The above diagram shows the formation of thermals, the convective currents created when air warmed by the sun rises upward. Birds use these currents to glide for long distances.

as a thermal, begins to flow. These are the currents that buoy up the buzzard and the condor as they float across the sky—and the human pilots of gliding craft. Over the years, gliding and hang-gliding enthusiasts have made a study of the ways in which thermal currents interact with the natural movement of winds and breezes forced up over rising ground (mountain ridges, valley walls, etc.) and it has become possible to get a sense of the complex conditions of which soaring birds long since learned to take advantage. For all these intricacies, though, the art of gliding depends on simple science. FLYING HIGH

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Above: Kenneth Arnold and his “flying saucer.” Right: Two drawings of UFOs from 1941.

Unidentified . . . But Irrefutable? Still small, but cumulatively hard to ignore, however, is the number of observations that are not so readily dismissed. Often they were recorded by professional pilots, or officers of the law—people trained to observe carefully, and to question what they saw. Improbable as it may seem, the military men who fired off thousands of anti-aircraft shells against incoming flying objects at the “Battle of Los Angeles” in 1942 may have been subject to a mass hysteria of sorts—though hundreds “saw” the strange craft and their traces on their radar screens. These were perilous times, after all, and in a state of stress and tension people become excitable. The specific notion of the flying saucer seems to originate with the sighting of disk- or saucer-shaped craft above the forests around Mount Rainier, Washington, by businessman Kenneth Arnold, in 344

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Right: A 1981 memo from USAF Lt. Col. Charles Halt on the Rendlesham Forest UFO sighting over England. Far right: Arnold’s own description and sketch of his experience. Top right: A flying saucer, perhaps a hoax.

1947. He was at the controls of his private plane at the time, and saw nine shiny disks flying in a line across the sky, spread out over a distance of approximately 5 miles (8 km). They appeared to flip over from time to time as they flew, sending out dazzling flashes of light as they did so. Partial corroboration came from another airman who had been flying nearby. That same year came reports that the US military had actually taken possession of the remains of a craft that had crashed outside Roswell, New Mexico. The claims that this was a UFO have only grown more insistent with the years (and with the repetition of the authorities’ denials). The official attitude to such sightings has always been dismissive, but documents obtained under Freedom of Information law make it clear that the authorities have hedged their bets. They have had to. The Kentucky Air National Guard had to be scrambled in 1948 FLYING HIGH

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ern “Fairy”) is known in ss Morgan le Fay (“Fay” as in the mod King Arthur’s nemesis, the evil enchantre legendary shape-shifting appears to have been on account of her Italian tradition as Fata Morgana. It temperature inversion. with a special kind of mirage caused by abilities that this name became associated ns—and works pretty to be seen in the Arctic and Arctic regio It occurs in colder conditions—so is often the cold ice or water t mirage. This time the air in contact with much in the opposite way from the deser cts light more. It has the the (slightly) warmer air above it, refra surface is chilled and, being denser than ing them into strange the horizon, stretching them laterally mak effect of apparently extending objects on ple. castles of distant ships or icebergs, for exam and unaccountable forms—making fairy

Strange Rains; Miraculous Mirages Just as curious in their way—and over hundreds of years too persistent to be dismissed too lightly—are stories of showers in which it “rains” frogs. Up to a point these claims can be explained away: young frogs may leave the ponds in which they were spawned in droves at a certain point in their development, setting off overland to seek new homes; their sudden appearance—sometimes they seem practically to carpet the ground—may give the impression that they rained down from the sky. But obstinate reports that frogs (and fish) have been seen, quite literally, raining down from the sky are not to be so easily brushed aside. Scientists have suggested that many may have been scooped up and carried high into the air by whirling waterspouts and tornadoes before being let fall. This would explain many incidents, though by no means all. Mirages are for the most part easily accounted for: in the blazing heat of an arid desert, air in contact with the scorching ground undergoes a rise in temperature. The cooler, denser air above has 348

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Opposite: A fata morgana at Cook Inlet, Alaska ,1976. Right: One of the famous mirages of the Sahara, enemy of the weary traveler. Inset: A 16th century illustration of a rain of fish.

a slightly greater refractive index—so it bends the light rays passing through it a little more. The resulting differential sets up the familiar shimmering effect we see each summer on highways or on asphalted lots. In the open expanse of the desert, the effect may be so pronounced as to give the impression of a wide and limpid lake of water—especially in the eyes of struggling traveler driven frantic by fear and dehydration. Explicable it may be, but anyone who ever witnessed a mirage knows that it is as miraculous in its way as any of the more exotic unexplained phenomena the sky produces. The force that lifts a jumbo jet—480 tons unloaded—and allows it to fly like a bird is as remarkable as any alien visitor could be. As extraordinary, though, is the vulnerability of what amounts to another environmental system above the earth—in critical danger now, perhaps, because of human actions. One thing is certain: with all its many aspects and the incredible possibilities it offers nature and humanity, there is a whole lot more to the sky than empty space. FLYING HIGH

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Pollution ur atmosphere is easily polluted by both manmade and natural particles. Caught in suspension in the air, or noxious gases in themselves, pollutants affect our lives daily and call into question the activities by which we sustain humanity. Pollution can be defined as any contaminant that adversely affects the stability of an ecosystem, though we also often use it to describe forms of energy that affect our quality of life, such as noise and light. Natural pollution has most commonly occurred in the past via the sulfurous poisoning of the skies by volcanoes and eruptive lava flows, as well as by asteroid strikes like the K-T Extinction asteroid, which so disrupted the Earth’s ecology that the dinosaurs were wiped out. But it is human pollution that in recent centuries has increasingly affected the quality of our atmosphere. It is not only a recent phenomenon: evidence from Greenland ice core samples suggests early metal smelting in Roman and medieval times had begun to pollute the skies. Our drive for global energy, our increasing reliance on mined resources and our mass scales of production peaked during the Industrial Revolution, and the resultant contaminants in the atmosphere affect us directly, from the smog of city traffic to the undeniable weather changes now associated with global warming.

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Space Junk The pollution of our Earth ends not in the atmosphere, but in space! Since Sputnik 1 was launched in 1957 we have sent a further 28,000 satellites into space, with 9000 currently in orbit, only 6% of which are operational. That’s a big backyard full of junk! There is so much unintended orbital traffic that collisions occasionally happen: dropped wrenches from space-walking repairs, flecked paint, broken heat tiles, as well as disused satellites—all have joined the natural pieces of dust and debris that get caught in our 358

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Right: Space debris is an ever-increasing concern.

Earth’s gravity well. Most of these items of space junk will decay in orbit and eventually burn up in the atmosphere, but with the increased satellite traffic, we are seeing more collisions and more potential cosmic “dandruff” than usual. In 1997 a Tulsa woman was hit on the shoulder by a scrap of burned cloth that had come from the fuel tank of the Delta 2 rocket the year before. It is the only report of someone being hit by falling space junk, though in 1960 a Cuban cow was killed by junk from a rocket launch in nearby Florida. Space stations such as the abandoned Skylab of 1979 and the Mir Station of 2001 also decay. Skylab was supposed to be ditched in the Indian Ocean, but most of it crashed down in Western Australia, where an enterprising young Stan Thornton retrieved some space junk off his roof, sped to the airport and took the first plane to the USA, where he had read that the San Francisco Examiner was offering $10,000 for the first piece of Skylab delivered THE AIR THAT WE BREATHE

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JUNKYARD SPACE

Most space pollutants will decay into burn-ups in our atmosphere, but this can take up to 35 years to occur. Larger redundant satellites can be nudged into graveyard orbits spinning them out into the cosmos, though this is a kind of “out of sight, out of mind” solution. More recent ideas for dealing with this cosmic junk have included laser brooms and aerogel blobs to destroy or trap the debris. However, a bristling 17,000-mph metal storm surrounding us in space means that it is not quite the peaceful void we imagine!

to its offices. He easily covered the cost of his flights! NASA scientists have tracked over 600,000 pieces of junk currently in orbit, though this does not count the millions of pieces of microjunk—a particle of which, say a paint fleck, traveling at 17,000mph, would hit a satellite or space walker like a bullet and do as much damage. In 2009 the US Iridium communications satellite and a Russian Kosmos satellite collided in orbit 490 miles (790 km) above Siberia, spraying junk and debris through an 807-mile (1300 km) orbital band, which includes the orbit of such delicate satellites as the Hubble Space Telescope. We have satellites in orbit from 186 miles (300km) to 21,700 miles (35,000 km), all spinning in counter circles among a cloud of increasing debris.

Chemicals The most common air pollutants we find are nitrogen oxides, carbon monoxides, sulfur dioxides, ozone, chlorofluorocarbons (CFCs) and radioactive particles. We must also not forget CO2 (carbon dioxide), our most significant greenhouse gas, which has been the protagonist in the story of recent climate change. Nitrogen oxides are various compounds of nitrogen and oxygen, the main toxins of which are nitrogen oxide (NO) and nitrogen dioxide (NO2), both produced in the combustion of fossil gases such as coal and natural gas. Carbon monoxides and dioxides, produced naturally in volcanoes, are also significant pollutants from the combustion engine, most commonly used in cars. Carbon monoxide is a lethal, odorless and tasteless gas which can 360

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EMISSION CREDITS

America’s pollution laws aimed to limit emission levels to a capped rate but also allow “well-behaved” companies to trade their emission credits for profit. No company is allowed to exceed the capped rate determined by the government, yet they have bartering flexibility to artificially massage their emissions. Critics say the system is difficult to audit and a complex means of allowing some industries to continue as they were. Others see it as an enlightened incentive-based scheme to force companies into more sustainable technology. Right: Pollution from a power station, adding to the greenhouse-gas problem.

be deadly, depriving the lungs of oxygen and starving the brain. It is the main cause of suffocation in fires. The effect in the atmosphere is to accelerate the production of methane and ozone; it also degrades easily into CO2 and thus has a greenhouse-gas effect. Carbon dioxide we have already met! Sulfur dioxides (SO2) are produced typically in volcanic eruptions, as well as exuded from the billowing smoke stacks of refineries and factories and manufacturing plants. They combine easily with water vapor to form acid rain. On a happier note, the USA has managed to reduce its sulfur-dioxide emissions by over 33% over the last 30 years, due to the initiatives of the EPA’s Acid Rain Program and the 1990 Clean Air Act. THE AIR THAT WE BREATHE

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Extinction—Only Natural? Because all life on Earth relies on a stable, well-oxygenated atmosphere, any radical changes in the atmosphere can lead to catastrophic extinction events. We know this because it has happened at least twice before, due to natural events. They are called the P-Tr (Permian Triassic) Extinction and the K-T (Cretaceous-Tertiary) Extinction. Fossil records show us that 251 million years ago, at the end of the Permian geological era, there was a “Great Dying” event. Almost all sea life was extinguished and 70% of land life disappeared, and plant life is estimated to have lost half its diversity. This extinction was not sudden: it lasted over several thousand years, so theories for its cause are abundant. One thing is for sure,

Left: An artist’s impression of our planet bombarded by asteroids. Opposite: An asteroid’s impact crater known as Meteor Crater, near Flagstaff, Arizona. A meteor or asteroid impact is believed to have caused a mass extinction event, and another could occur at some point in the future.

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the atmosphere was so disrupted that the food chain was devastated. It is thought that the Permian Extinction was kicked off by massive volcanic activity in the Siberian Traps lava flows, which released a massive amount of dust, CO2 and methane into the atmosphere. This event may have been compounded by a phenomenon known as the Methane Clathrate Gun. This is when methane is released through global warming from the oceans and permafrost, accelerating global warming and turning the oceans anoxic (or deoxygenated). The hydrogen sulfides that were released would have poisoned plant and animal life, already stressed by significant climatic change. Whatever caused this massive event, the atmosphere was certainly the agent of change.


GLOBAL DIMMING

the atmosphere is the reduction of solar One peculiar effect of particulates in has h—known as global dimming. This heat reaching the surface of the Eart tly recen ence 1960 to 1990, but evid been measured as a 4% reduction from r sulfu as such tes reversal. Particula suggests there has been a “brightening” sing diffu in rit culp main to be the dioxides in the atmosphere are thought in has also been a measurable decrease there and e, spac into back rays solar or ters exist, but whether it coun pan-evaporation rates. The effect does is still not fully understood— ing warm al glob of accelerates the effects raffic contrails, or areas in heavily measurements in areas with high air-t suggest a cooling effect. It is also do polluted skies after volcanic eruptions may be responsible for droughts. The thought to affect the water cycle and be masking the full impact of global effect of this phenomenon may actually may be more severe than first warming, and future temperature rises relationship has yet to be reached. this predicted, but a full understanding of

Solar Activity The cyclical patterns of our own sun could also affect our climate. There is some evidence that there is a correlation between sunspot activity and climatic periods such as the Little Ice Age, which lasted from about the13th to the 19th century. This cool period seems to have been characterized by an average 1.8ºF (1ºC) drop in temperature, with longer, harsher winters and more glaciation. Evidence for Northern Europe’s cooling is documented in the so-called Frost Fairs of London, the first of which was in 1607, when the Thames was completely frozen. Businesses took their stalls onto the ice, where people crowded for skating, fun and just to move about London unimpeded. The last documented Frost Fair was in 1814, well into the Industrial Revolution era, when mean temperatures had begun to rise again. Many rivers, canals and lakes in the Netherlands also froze, as seen in the work of such great artists as Brueghel and Avercamp. 394

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The Little Ice Age is thought to have been the combination of solar forcing, that is, natural changes in solar radiation reaching the earth, and the cooling effect of volcanic gases from eruptions such as the catastrophic Tambora Eruption of 1815, which in the Northern Hemisphere led to 1816 being hailed the “year without a summer.� The solar astronomer Edward Maunder has suggested that the almost complete absence of sunspots (the Maunder Minimum) between 1645 and 1715 was partly responsible for a decrease in solar radiation and the solar forcing of temperature drops. The amount of cloud cover and solar irradiance has also been linked with 11-year cycles of sunspots, but the IPCC has cast doubt as to whether in the long term these natural inputs account for our current runaway CO2 and temperature rises.

Above: Could atmospheric pollution caused by industry or volcanic activity be a cause of global dimming as well as warming?

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