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  In 904 CE, the great Persian Muslim scientist Ibn Wahshiyya translated from Nabataean Arabic a book on agriculture, which claimed rain could be predicted using lunar phases and atmospheric changes. Five centuries later, Leonardo da Vinci assembled the first hygrometer to measure humidity. But the most important discovery for modern forecasting wasn’t made until 1650 when Evangelista Torricelli invented the barometer.

  The Invention of the Barometer

  In 1608, Galileo Galilei heard about a spectacle maker in Holland who had fashioned an arrangement of lenses with the remarkable power of making distant things appear closer. He reproduced the arrangement on his own in Pisa and then, seeing room for improvement, built the world’s first astronomical telescope, turned it on the moon and became the first human being to see lunar mountains. Looking at Jupiter, he discovered that it was orbited by several moons. Everywhere he turned his telescope in the night sky was bristling with stars and nebulae, and everything in this newly immense universe confirmed Copernicus’s heretical assertion that the Earth orbited the sun, not the other way around. There was a big party going on out there, and the Vatican was not invited. All this was plain for anyone with a telescope.

  But Earth’s atmosphere had yet to be fully understood. Air was thought to be weightless, and anything less than air was deemed to be impossible. Aristotle’s proclamation that nature abhors a vacuum was still regarded as a fundamental truth when, in 1630, a young scientist named Giovanni Battista Baliani wrote to his mentor, Galileo Galilei, concerning a problem he’d discovered with a siphon he had constructed to conduct water. He was using a suction pump to force water uphill, trying to ascertain just how high it could rise.

  Baliani found that if the elevation of the transfer siphon reached a critical height, somewhere around 34 feet, the water stopped flowing. Something impeded it. Hence his letter. Galileo responded (years later in a 1638 publication) with two extraordinary speculations: not only did he acknowledge that a vacuum could exist (in the empty space at the top of Baliani’s siphon), he also asserted the vacuum wasn’t quite strong enough to raise the weight of the water above the 34-foot level.

  Two years later, this speculation inspired two young scientists, Gasparo Berti and Raffaello Magiotti, to fill a 42-foot-long lead pipe with water and plug both ends. They then stood the tube in a water-filled basin and opened the bottom plug. Counter-intuitively the water in the cylinder didn’t entirely flow out. In fact, hardly any water spilled into the basin; the level inside the pipe had dropped only slightly. Because the upper end was sealed, there had to be a space at the top of the cylinder. What could be in that space? Had Berti and Magiotti succeeded in producing the very thing that nature abhored, something unnatural and yet so powerful it held up the column of water?

  Evangelista Torricelli, a 32-year-old mathematician from Rome, applauded the experiment — the creation of the first generally recognized artificial vacuum — but he was more intrigued by the height of the water remaining in the tube. Berti and Magiotti estimated the level to be about 34 feet, the same as the height in Baliani’s tube. Why the consistency? In 1631, nine years earlier, René Descartes had theorized that air might have weight and further speculated that it might be possible to construct a device to measure it. Torricelli realized that Berti and Magiotti’s experimental apparatus was that device — it was showing that the weight of the atmosphere pushed the water up the tube and prevented it from running out. Torricelli had discovered the barometer. At least in theory. All he had to do was build his own.

  Back in his laboratory, Torricelli set about constructing a prototype. But the Inquisition was raging just outside his laboratory windows, and he had nosy, gossipy neighbors. A two-story barometer erected in his courtyard would be viewed as the devil’s work. Scientists were considered heretics to be locked in dungeons or burned at the stake like Giordano Bruno. Even the great Galileo, court mathematician to Ferdinando II, Grand Duke of Tuscany, had been forced to publically recant his scientific discoveries and go into exile. (Though Galileo’s banishment to his villa in Arcetri hardly seems punitive.)

  Unfortunately, the ceilings in Torricelli’s laboratory weren’t high enough to accomodate a 34-foot barometer. He needed to find a replacement for the water, something denser that would permit him to scale down the barometer’s size. Mercury fit the bill. It was 14 times denser than water, allowing the 34-foot lead pipe to be replaced with a 32-inch glass tube. Once the mercury found its level, Torricelli could see the airless gap at the sealed top of the tube. Best of all, the whole apparatus fit easily on a small desk.

  In science, it seems the important stuff is always invisible at first: radiation, radio waves, gravity and the weight of air. Now the unseen and impalpable realm of atmospheric pressure was made visible. In late spring 1644, Torricelli wrote to his friend Michelangelo Ricci and declared, “We live submerged at the bottom of an ocean of elementary air, which is known by incontestable experiments to have weight.” Not only was the unseen realm of atmospheric pressure now visible, it was now measurable. As well, Torricelli calibrated the column of mercury and documented the daily variations in its height. He wrote that his instrument “will exhibit changes in the atmosphere, which is sometimes heavier and at other times lighter and thinner.”

  With his barometer, Torricelli had an observable vacuum with which he could perform other experiments. In one of them, he tried to determine if sound traveled in a vacuum, but the results were inconclusive. He also, curiously, placed insects in the vacuum to see if they survived. Insects don’t look like they breathe, but as Torricelli undoubtedly discovered, they do.

  Torricelli’s mercury barometer underwent many refinements over the next few centuries. Blaise Pascal developed a portable one in 1646 and two years later used it on a mountain to confirm the decrease in air density with increased altitude. Manufacturers got into the game. Everyone was curious about these little forecasting devices, and by 1670, the first year of the coldest period of the Little Ice Age, barometers became the must-have conversation piece for the wealthy. As the price came down, the craze spread to the middle class. Over the next 200 years, the market for barometers went global, with more than 3,000 barometer manufacturers registered in Europe. The era of personal forecasting had arrived. When your barometer plunged, you knew bad weather was on the way. In its ornate, hand-carved wooden case, the barometer was a household wonder.

  Scientists continued to refine the barometer as well as its sibling, the hygrometer, invented by Leonardo da Vinci and perfected in 1783 by Swiss physicist Horace Bénédict de Saussure. A hygrometer measures the water vapor in the atmosphere, and de Saussure’s version used a single human hair to do so. (Stretched taut in a brass frame, the hair was connected to a needle indicator on a scale — changes in its length caused by humidity were thereby measured.) De Saussure bemoaned the fact that all the scientific progress in weather forecasting was still no better than folk wisdom — “When there is enough clear blue sky to patch a Dutchman’s breeches, expect fair weather,” as one of the folk sayings went. He wrote, “It is humiliating to those who have been much occupied in cultivating the Science of Meterology, to see an agriculturist or a waterman, who has neither instruments nor theory, foretell the future changes of the weather many days before they happen, with a precision, which the Philosopher, aided by all the resources of Science, would be unable to attain.”

  In 1843, a French physicist, Lucien Vidie, built an aneroid barometer. This clock-like instrument didn’t use mercury. Rather it relied on a small metal drum containing a partial vacuum that expanded and contracted as the air pressure went up and down. The drum was attached to a spring and, through a series of levers, to a needle on the face of the barometer. Aneroid barometers were smaller and more robust than mercury barometers. A year later, Vidie also perfected the barograph, which replaced the needle on the barometer with a pen that inscribed a line on a roll of paper that covered a rotating, clockwork drum. The resulting g
raph, rising and falling over a period of several days, became a permanent record of changes in air pressure.

  Weather Forecasts

  With the hygrometer, barometer and thermometer now all in use, the stage was set for the first public weather forecasts, and their architect was Robert FitzRoy (1805–1865), the son of the third Duke of Grafton and great-grandson of Charles II. He grew up in a Palladian mansion in Northamptonshire and as a child dreamed of sailing with the British navy and commanding one of the great three-masted schooners that were then the mainstay of the fleet. To this end, at the age of 12, he enrolled with the Royal Naval College and two years later joined the Royal Navy as a deck hand, sailing on the frigate HMS Owen Glendower on its six-month journey to South America.

  Upon his return in January 1822, Robert regaled his family with stories of exotic lands. Otherwise, 1822 was not to be a good year for the FitzRoys. Robert’s uncle, Viscount Castlereagh, was the British foreign secretary, but he had had a few bad years. Lampooned in a poem by Percy Bysshe Shelley and increasingly unpopular with the British public, he started to exhibit symptoms of insanity. In a rare lucid interlude during his descent into madness, he remarked, “My mind, is, as it were, gone.” In August of that year, he cut his throat with a penknife.

  Curiously this wouldn’t be the only suicide to cross FitzRoy’s path. His eventual appointment as captain of the HMS Beagle and his association with Charles Darwin came about as the result of another suicide, this time of Captain Pringle Stokes, who had been carrying out a protracted hydrographic survey of the bleak waters near the tip of Tierra del Fuego onboard the HMS Beagle. “Nothing could be more dreary than the scene around us,” Stokes wrote in his journal in 1828. He sank into a listless despondency fueled by the endless gray days and damp, bitter cold, and his diary entries became increasingly morose. While surveying the Golfo de Penas (“Gulf of Distress”) on the Chilean side of the archipelago, he claimed it was a place where “the soul of man dies in him.” A few weeks later, he locked himself in his quarters, refusing to come out. Six weeks after that, he shot himself in the head.

  Enter Robert FitzRoy. At 22 years old, he found himself at the helm of what would turn out to be one of the most famous vessels in history. He proved an able captain and an excellent navigator; several years later, he circumnavigated the planet on a five-year voyage of exploration and discovery. FitzRoy asked Francis Beaufort, whom he knew well, to suggest an intellectual companion for that second voyage. The result was that a certain Charles Darwin was appointed chief science officer.

  But this famous voyage was blighted. Over the course of the journey, FitzRoy’s character revealed a venemously contrarian side that sometimes plunged Darwin and FitzRoy into fantastic arguments. Darwin referred to one of these in his diary as “bordering on insanity,” and in a letter written years later he described FitzRoy as a “poor fellow, his mind . . . quite out of balance.” FitzRoy, it seems, had little of the cool impartiality of the true scientist. He was one of the dying breed of Victorian amateur gentleman naturalists who would shortly be outstripped by professionals steeped in the protocols of logical methodology.

  After the voyage, FitzRoy wrote and published a four-volume account of his adventures with Darwin. He received a gold medal from the Royal Geographical Society, and in 1841 successfully ran for parliament. In 1843, he was appointed governor of New Zealand. He had always been interested in meteorology and had remained in close contact with Francis Beaufort, who became a seminal partner in FitzRoy’s aspirations to create a weather prediction system for seafaring vessels. FitzRoy returned to England in 1848 and in 1854 was appointed chief of a newly created meteorological department in the Board of Trade.

  He began to standardize the collection of weather data from 15 inland observation stations in England, linked by telegraph to his office. In 1859, after a national maritime disaster, he seized on the opportunity to design weather charts for what he called “forecasting the weather.” But his predictions were sometimes less than logical. In his 1863 publication, The Weather Book: A Manual of Practical Meteorology, he aired the peculiar notion that the length of the period between a sign indicating a change in the weather and the arrival of the weather in question indicated how long that period of weather would last. He strayed off the scientific path even more wildly when he had FitzRoy storm glasses installed at quayside in every major British port. These devices were to be consulted by sailors before they ventured out, but they were merely glass cylinders filled with a cocktail of potassium nitrate, ammonium chloride, ethanol, camphor and water. This mixture occasionally produced crystals or floating particles, and these, FitzRoy insisted, foretold changes in the weather. In truth, they had no connection to the weather at all.

  Nonetheless, FitzRoy did have the distinction of publishing the first daily weather forecast in the Times of London. It would turn out to be his last hurrah. Times were changing, and quickly. The rapid transformation of the science of meteorology reflected how all the scientific disciplines were accelerating in the late nineteenth century. The epoch of the amateur was over. So it was up to FitzRoy’s successor at the Times, Francis Galton (1822–1911), a Quaker, to create something that we would recognize today as a contemporary, scientific weather map.

  Passing the Torch

  Galton was Charles Darwin’s half cousin and a child prodigy. He was mathematically inclined and devoutly believed in the power of numbers. By 1861, he was the first to grasp the impact of the Coriolis effect on weather. Later the same year, he discovered that certain weather systems rotate in the opposite direction of cyclones and that, furthermore, the barometric pressure within these systems is higher than the surrounding region. He called them anticyclones. He then realized that cyclones and anticyclones were like cogs in a clockwork mechanism “and make the movements of the entire system correlative and harmonius.” Galton began to improve on FitzRoy’s weather maps, using lines (isobars) to link all the points of identical barometric pressure. These formed a series of concentric rings, a feature in almost every newspaper forecast today. The only thing his charts were missing, at least to contemporary eyes, were the graphics that represented weather fronts, an improvement still to come.

  Galton brought considerable statistical weight to his postulations and published his results in the prestigious science journal Nature. His reputation began to eclipse FitzRoy’s, who came to view Galton as his bitter nemesis. FitzRoy’s health declined, and he fell into a severe depression. In 1865, when he was 59, FitzRoy, like his uncle before him, slit his throat.

  Ten years later, on April Fools’ Day, 1875, Galton’s first weather map, showing detailed weather conditions across the British Isles from the day before, was published in the Times.

  Mathematics and Weather Prediction

  The science of meteorology entered the modern era with the help of four scientists who came after Francis Galton. They were an American, Cleveland Abbe; a Norwegian, Vilhelm Bjerknes; an Englishman, Lewis Fry Richardson; and a Hungarian, John von Neumann.

  Cleveland Abbe was born in New York in 1838, six years before Samuel Morse sent the first telegraph message (“What hath God wrought”). The New York of Abbe’s childhood would be unrecognizable today. There were no skyscrapers, no subways and no electric streetlights. The only electricity available was the minuscule current used by telegraphs. The winters were cold and the summers short and cool. The Little Ice Age didn’t end until 1850, when Cleveland was 12. During a New York night, you could see the Milky Way, and in the chilly mornings, on his way to school, Abbe would have heard roosters calling. It was downright rural.

  Abbe was an autodidact at heart. When he was eight, his mother gave him a copy of William Smellie’s The Philosophy of Natural History, a forerunner of the Encyclopedia Britannica, and he discovered a universe of information within its pages. Later, as a young man, he tried to enlist on the Union side of the Civil War, but he was rejected because of his myopia. He went to Harvard instead a
nd upon graduation became a telegraph engineer, then worked as an astronomer at the Pulkovo Astronomical Observatory near Saint Petersburg, Russia, before assuming the directorship of the Cincinnati Observatory. It was here that his passion for meteorology flowered, and he started to map out an early warning system. He imagined that weather observers could be spaced out at regular distances, forming a grid of sorts, and they would be linked by telegraph to a central information processing headquarters. The Smithsonian Institution had already demonstrated the feasibility of such a scheme. By 1847, it was publishing telegraphically derived observations from weather watchers all over the United States, producing a weather map displayed daily in the institution’s lobby. It became a tourist draw.

  Abbe’s dream of a national weather observation network would finally be realized in 1871 when he was appointed chief meteorologist at the National Weather Service. He enlisted 20 volunteer weather observers from across the country. At regular times, they were to transmit data on wind direction, temperature, precipitation and barometric pressure to his team of clerks at the National Weather Service. Another team would transfer the collected data to weather maps. For the first time, large weather systems could be followed and tracked hourly.