dk-the-science-book_compress

["EXPANDING HORIZONS 99 See also: Isaac Newton 62\u201369 \u25a0 Louis Agassiz 128\u201329 \u25a0 Charles Darwin 142\u201349 \u25a0 Marie Curie 190\u201395 \u25a0 Ernest Rutherford 206\u201313 older, since eons of time would its parts,\u201d with a new world activity. Today, this is known as be needed for chalk mountains to constantly reshaped and recycled the geological cycle. From this build up from the remains of marine from the ruins of the old. evidence, Hutton declared that fossils, but he did not want to all continents are formed from publish this view without evidence. Hutton formulated his Earth- materials derived from previous machine theory before he had found continents by the same processes, Secrets of the rocks the supporting evidence, but, in and that these processes still In Scotland, quite a different 1787, he found the \u201cunconformities\u201d operate today. Famously, he wrote approach to the problem of Earth\u2019s he was looking for\u2014breaks in the that \u201cthe result, therefore, of this age was being taken by James continuity of sedimentary rocks. present enquiry is, that we \ufb01nd Hutton, one of the preeminent He saw that much of the land had no vestige of a beginning\u2014no natural philosophers of the Scottish once been seabed, where layers prospect of an end.\u201d Enlightenment. Hutton was a of sediment had been laid down and pioneer of geological \ufb01eldwork, and compressed. In many places these The popularization of Hutton\u2019s used \ufb01eld evidence to demonstrate layers had been pushed upward, so ideas about \u201cdeep time\u201d was his arguments to the Royal Society that they were above sea level, and primarily due to John Playfair, a of Edinburgh in 1785. often distorted, so that they were Scottish scientist who published not horizontal. He repeatedly found Hutton\u2019s observations in an Hutton was impressed by that rock material from the illustrated book, and to British the apparent continuity of the truncated upper boundary of older geologist Charles Lyell, who processes by which landscape was strata was incorporated into the transformed Hutton\u2019s ideas into a denuded and its debris deposited base of the younger rocks above. system called uniformitarianism. into the sea. And yet all these This held that the laws of nature \u276f\u276f processes did not lead to loss of the Such unconformities showed land surface, as might be expected. that there had been many episodes In 1770, Hutton built a house Perhaps thinking of the famous in Earth\u2019s history when the overlooking Salisbury Crags in steam engine built by his friend sequence of erosion, transportation, Edinburgh, Scotland. Among the James Watt, Hutton saw Earth as and deposition of rock debris had crags he found evidence of volcanic \u201ca material machine moving in all been repeated, and when rock penetration through sedimentary rock. strata had been moved by volcanic","100 JAMES HUTTON have always been the same, and The mind seemed to took Earth\u2019s initial temperature at therefore the clues to the past lie grow giddy by looking so 7,000\u00b0F (3,900\u00b0C) and applied the in the present. However, while far into the abyss of time. observation that temperature Hutton\u2019s insights concerning the increases as you go downward from antiquity of the planet rang true John Playfair the surface\u2014by about 1\u00b0F (0.5\u00b0C) to geologists, there was still no over every 50 ft (15 m) or so. From satisfactory method of determining observed that the processes of this, Kelvin calculated that it had just how old the planet was. erosion and deposition of the rock taken 98 million years for Earth to materials that make up such strata cool to its present state, which he An experimental approach were very slow\u2014estimated to be later reduced to 40 million years. Since the end of the 18th century, a few inches (centimeters) every scientists had recognized that 100 years. In 1858, Charles Darwin A radioactive \u201cclock\u201d Earth\u2019s crust comprises successive made a somewhat ill-judged foray Such was Kelvin\u2019s prestige that layers of sedimentary strata. into the debate when he estimated his measure was accepted by most Geological mapping of these strata that it had taken some 300 million scientists. Geologists, however, revealed that cumulatively they are years for erosion to cut through the were left feeling that 40 million very thick and many contain the Tertiary and Cretaceous period years was simply not long enough fossil remains of the organisms rocks of the Weald in southern for the observed rates of geological that lived in their respective England. In 1860, John Phillips, processes, accumulated deposits, depositional environments. By a geologist at Oxford University, and history. However, they the 1850s, the geological column estimated that Earth is about had no scienti\ufb01c method with of strata (also known as the 96 million years old. which to contradict Kelvin. stratigraphic column) had been more or less carved up into some But in 1862, such geological In the 1890s, the discovery eight named systems of strata and calculations were scorned by the of naturally occurring radioactive fossils, each of which represented eminent Scottish physicist William elements in some of Earth\u2019s a period of geological time. Thomson (Lord Kelvin) for being minerals and rocks provided the unscienti\ufb01c. Kelvin was a strict key that would resolve the impasse Geologists were impressed by empiricist and argued that he between Kelvin and the geologists, the overall thickness of the strata, could use physics to determine since the rate at which atoms estimated to be 16\u201370 miles an accurate age for Earth, which decay makes a reliable timer. (25\u2013112 km) thick. They had he thought was constrained by In 1903, Ernest Rutherford the age of the Sun. Understanding predicted rates of radioactive of Earth\u2019s rocks, their melting decay and suggested that points and conductivity, had vastly radioactivity might be used as improved since Buffon\u2019s day. Kelvin a \u201cclock\u201d to date minerals and the rocks that contain them. Lord Kelvin pronounced the world to be 40 million years old in 1897, the year In 1905, Rutherford obtained in which radioactivity was discovered. the very \ufb01rst radiometric dates He did not know that radioactive decay of formation for a mineral from in Earth\u2019s crust provides heat that Glastonbury, Connecticut: 497\u2013500 greatly slows the rate of cooling. million years. He warned that these were minimum dates. In 1907, American radiochemist Bertram Boltwood improved on Rutherford\u2019s technique to produce the \ufb01rst radiometric dates of minerals in rocks with a known geological context. These included a 2.2-billion-year-old rock from Sri Lanka, whose age increased previous estimates by an order","EXPANDING HORIZONS 101 An uncomformity is a buried surface separating two rock strata of different ages. This diagram shows an angular unconformity, similar to those discovered by James Hutton on the east coast of Scotland. Here, layers of rock strata have been tilted by volcanic activity or movements in Earth\u2019s crust, producing an angular discordance with overlying, younger layers. Angular James Hutton discordance Born in 1726 to a respected Older, tilted merchant in Edinburgh, rock strata Scotland, James Hutton studied humanities at of magnitude. By 1946, British radiometric age of 4.56 billion Edinburgh University. He geologist Arthur Holmes had made years for granite and basalt igneous became interested in some isotope measurements from rocks in Earth\u2019s crust, he concluded chemistry and then medicine, lead-bearing rocks from Greenland, that the similarity of dates was but did not practice as a which gave an age of 3.015 billion indicative of the age of Earth\u2019s doctor. Instead, he studied years. This was one of the \ufb01rst formation. By 1956, he had made the new agrarian techniques reliable minimum ages for Earth. further measurements, which being used in East Anglia, Holmes went on to estimate the increased his con\ufb01dence in the England, where his exposure age of the uranium from which the accuracy of the date of 4.55 billion to soils and the rocks they lead was derived, obtaining a date years. This remains the \ufb01gure were derived from led to an of 4.46 billion years, but he thought accepted by scientists today. \u25a0 interest in geology. This took that must be the age of the gas him on \ufb01eld expeditions all cloud from which Earth formed. The past history of our over England and Scotland. globe must be explained by Finally, in 1953, American Returning to Edinburgh geochemist Clair Patterson what can be seen to be in 1768, Hutton became obtained the \ufb01rst generally happening now. acquainted with some of accepted radiometric age of 4.55 James Hutton the major \ufb01gures of the billion years for Earth\u2019s formation. Scottish Enlightenment, There are no known minerals or including the engineer rocks dating from Earth\u2019s origin, James Watt and the moral but many meteorites are thought philosopher Adam Smith. to originate from the same event Over the next 20 years, Hutton in the solar system. Patterson developed his famous theory calculated the radiometric date for of Earth\u2019s age and discussed it lead minerals in the Canyon Diablo with his friends before \ufb01nally meteorite at 4.51 billion years. publishing a long outline in Comparing it with the average 1788 and a much longer book in 1795. He died in 1797. Key work 1795 Theory of the Earth with Proofs and Illustrations","102 THE ATTRACTION OF MOUNTAINS NEVIL MASKELYNE (1732\u20131811) IN CONTEXT The gravitational mass The plumb line of a mountain should will hang at an angle that BRANCH attract a plumb bob. Earth science and physics depends on the relative density of the mountain BEFORE 1687 Isaac Newton publishes and Earth. the Principia, in which he suggests experiments for Measuring the deviation calculating Earth\u2019s density. should allow calculation of Earth\u2019s mass. 1692 In an effort to explain Earth\u2019s magnetic \ufb01eld, I n the 17th century, Isaac However, Newton himself Edmond Halley suggests that Newton had suggested dismissed the idea because the planet consists of three methods for \u201cweighing the he thought the deviation would concentric hollow spheres. Earth\u201d\u2014or calculating Earth\u2019s be too small to be measured density. One of these involved with the instruments of the day. 1738 Pierre Bouguer attempts measuring the angle of a plumb Newton\u2019s experiment, without line on each side of a mountain to In 1738, Pierre Bouguer, a success, on Chimborazo, a \ufb01nd out how far the gravitational French astronomer, attempted volcano in Ecuador. attraction of the mountain pulled the experiment on the slopes of it from the vertical. This deviation Chimborazo in Ecuador. Weather AFTER could be measured by comparing and altitude caused problems, 1798 Henry Cavendish the plumb line to a vertical however, and Bouguer did not think uses a different method to calculated using astronomical his measurements were accurate. calculate the density of methods. If the density and Earth, and \ufb01nds it to be volume of the mountain could be In 1772, Nevil Maskelyne 340 lb\/ft3 (5,448 kg\/m3). ascertained, then, by extension, proposed to the Royal Society in so could the density of Earth. London that the experiment could 1854 George Airy \ufb01gures be conducted in Britain. The out Earth\u2019s density using Society agreed, and sent a surveyor pendulums in a mine.","EXPANDING HORIZONS 103 See also: Isaac Newton 62\u201369 \u25a0 Henry Cavendish 78\u201379 \u25a0 John Michell 88\u201389 to select an appropriate mountain. Schiehallion was chosen as the site \u2026the mean density of the He chose Schiehallion in Scotland, for the experiment because it was earth is at least double of that and Maskelyne spent nearly four symmetrically shaped and isolated at the surface\u2026the density of months making observations from (and therefore less affected by the the internal parts of the earth both sides of the mountain. gravitational pull of other mountains). is much greater than near The density of rocks arc (just over 0.003 degrees). the surface. The orientation of the plumb line Maskelyne used a survey of the compared to the stars should have shape of the mountain and a Nevil Maskelyne been different at the two stations measurement of the density of its even without any gravitational rocks to \ufb01gure out the mass of that said Earth was hollow. It also effects, because of the difference Schiehallion. He was assuming allowed the mass of Earth to be in latitude. However, even when that the whole Earth had the same extrapolated from its volume and this was accounted for, there was density as Schiehallion, but the average density. Maskelyne\u2019s value still a difference of 11.6 seconds of deviation of the plumb lines for the overall density of Earth was showed a measured value of less 280 lb\/ft3 (4,500 kg\/m3). Compared than half of what he was expecting. with today\u2019s accepted value of Maskelyne realized that the density 344 lb\/ft3 (5,515 kg\/m3), he had assumption was not correct\u2014the \ufb01gured out the density of Earth density of Earth was clearly much with an error of less than 20 percent, greater than that of its surface and in the process had proved rocks, probably, he reasoned, due Newton's law of gravitation. \u25a0 to the planet having a metallic core. The actual observed angle was used to \ufb01gure out that the overall density of Earth is about double that of Schiehallion\u2019s rocks. This result disproved one theory of the time, advocated by English astronomer Edmond Halley, Nevil Maskelyne Born in London in 1732, Nevil much time trying to solve the Maskelyne became interested problem of measuring longitude in astronomy at school. After while at sea\u2014a major issue of graduating from Cambridge the day. His method involved University and being ordained a carefully measuring the priest, he became a member of distance between the Moon the Royal Society in 1758, and and a given star, and consulting was the Astronomer Royal from published tables. 1765 until his death. Key works In 1761, the Royal Society sent Maskelyne to the Atlantic island of 1764 Astronomical Observations St. Helena to observe the transit Made at the Island of St Helena of Venus. Measurements taken 1775 An Account of as the planet passed across the Observations Made on Sun\u2019s disk allowed astronomers to the Mountain Schehallien calculate the distance between for Finding its Attraction Earth and the Sun. He also spent","104 THE MYSTERY OF NATURE IN THE STRUCTURE AND FERTILIZATION OF FLOWERS CHRISTIAN SPRENGEL (1750\u20131816) IN CONTEXT I n the mid-18th century, Swedish and female parts, and that in these, botanist Carl Linnaeus realized the parts mature at different times, BRANCH that \ufb02ower parts parallel the preventing self-fertilization. Biology reproductive organs of animals. Forty years later, a German Published in 1793, Sprengel\u2019s BEFORE botanist called Christian Sprengel work was largely underappreciated 1694 German botanist \ufb01gured out how insects played a during his lifetime. However, Rudolph Camerarius shows major role in the pollination, and it was \ufb01nally given due credit that \ufb02owers carry a plant\u2019s so fertilization, of \ufb02owering plants. when Charles Darwin used it as reproductive parts. a springboard for his own studies Mutual bene\ufb01t on the coevolution of \ufb02owering 1753 Carl Linnaeus publishes In the summer of 1787, Sprengel plants and the particular species Species Plantarum, devising a noticed insects visiting open of insects that pollinate them and classi\ufb01cation system guided \ufb02owers to feed on the nectar inside. ensure cross-fertilization\u2014to their by \ufb02ower structure. He began to wonder whether the mutual bene\ufb01t. \u25a0 nectar was being \u201cadvertised\u201d 1760s Josef Gottlieb K\u00f6lreuter, by the petals\u2019 special color and A honeybee lands on the sexual parts a German botanist, proves pattern, and deduced that the displayed at the center of these brightly that pollen grains are needed insects were being enticed onto colored petals. Honeybees account for to fertilize a \ufb02ower. the \ufb02owers so that pollen from the 80 percent of all insect pollination and stamen (male part) of one \ufb02ower pollinate a third of all food crops. AFTER stuck to the insect and was carried 1831 Scottish botanist Robert to the pistil (female part) of another Brown describes how pollen \ufb02ower. The insect\u2019s reward was a grains germinate on a \ufb02ower\u2019s drink of energy-rich nectar. stigma (female part). Sprengel discovered that some 1862 Charles Darwin \ufb02owering plants, if they lack color publishes Fertilisation of and scent, rely on wind to disperse Orchids, a detailed study their pollen. He also observed that of the relationship between many \ufb02owers contain both male \ufb02owers and pollinating insects. See also: Carl Linnaeus 74\u201375 \u25a0 Charles Darwin 142\u201349 \u25a0 Gregor Mendel 166\u201371 \u25a0 Thomas Hunt Morgan 224\u201325","EXPANDING HORIZONS 105 ELEMENTS ALWAYS COMBINE THE SAME WAY JOSEPH PROUST (1754\u20131836) IN CONTEXT T he Law of De\ufb01nite Iron, like many other metals, Proportions, published is subject to the law of nature BRANCH by French chemist Joseph Chemistry Proust in 1794, shows that no which presides at every matter how elements combine, the true combination, that BEFORE proportions of each element in a is to say, that it unites c.400 BCE The Greek thinker compound are always precisely the Democritus proposes that the same. This theory was one of the with two constant world is ultimately made of tiny fundamental ideas about elements proportions of oxygen. indivisible particles\u2014atoms. that emerged at this period to form the basis of modern chemistry. Joseph Proust 1759 English chemist Robert Dossie argues that substances In making his discovery, Proust John Dalton\u2019s new atomic theory of combine when they are in the was following a trend in French elements\u2014that elements are each right proportion, which he calls chemistry, pioneered by Antoine made of their own unique atoms. If the \u201csaturation proportion.\u201d Lavoisier, which advocated careful a compound is always made from measurement of weights, ratios, the same combination of atoms, 1787 Antoine Lavoisier and and percentages. Proust studied Proust\u2019s argument that elements Claude Louis Berthollet devise the percentages in which metals always combine in \ufb01xed the modern system of naming combined with oxygen in metal proportions must be true. This is chemical compounds. oxides. He concluded that when now accepted as one of the key metal oxides formed, the proportion laws of chemistry. \u25a0 AFTER of metal and oxygen was constant. 1805 John Dalton shows that If the same metal combined with elements are made up of atoms oxygen in a different proportion, it of a particular mass, which formed a different compound with combine to make compounds. different properties. 1811 Italian chemist Amedeo Not everyone agreed with Avogadro makes a distinction Proust, but in 1811, the Swedish between atoms and the chemist J\u00f6ns Jakob Berzelius molecules that are formed by realized that Proust\u2019s theory \ufb01t atoms to make compounds. See also: Henry Cavendish 78\u201379 \u25a0 Antoine Lavoisier 84 \u25a0 John Dalton 112\u201313 \u25a0 J\u00f6ns Jakob Berzelius 119 \u25a0 Dmitri Mendeleev 174\u201379","A CENT OF PRO 1800\u20131900","URY GRESS","108 INTRODUCTION Astronomer William In the cliffs of Lyme Michael Faraday Christian Doppler Herschel discovers Regis, Mary Anning \ufb01nds discovers the principle explains why binary infrared radiation. the skeleton of the \ufb01rst behind the stars are colored. known ichthyosaur. electric motor. 1800 1811 1821 1842 1803 1820 1837 1845 John Dalton introduces the Hans Christian \u00d8rsted Louis Agassiz German explorer idea of atomic weights. discovers that when a describes Alexander von current is switched on, an ice age. Humboldt introduces the idea of ecology. a nearby compass needle \ufb02ickers. T he invention of the electric William Herschel used a prism to of binary stars using the idea that battery in 1799 opened separate the various colors of light is a wave with a spectrum up whole new \ufb01elds of sunlight to study their of various frequencies, laying out scienti\ufb01c research. In Denmark, temperatures; he found that his the phenomenon now known as the Hans Christian \u00d8rsted accidentally thermometer showed a higher Doppler effect. Meanwhile, in Paris, discovered a connection between temperature beyond the red end of French physicists Hippolyte Fizeau electricity and magnetism. At the visible spectrum. Herschel had and L\u00e9on Foucault measured the London\u2019s Royal Institution, stumbled upon infrared radiation, speed of light, and showed that it Michael Faraday imagined the and ultraviolet radiation was travels more slowly through water shapes of magnetic \ufb01elds, and discovered the following year\u2014 than through air. invented the world\u2019s \ufb01rst electric proving that there was more to the motor. In Scotland, James Clerk spectrum than visible light. In a Chemical changes Maxwell picked up Faraday\u2019s similar accidental way, Wilhelm British meteorologist John Dalton ideas and \ufb01gured out the complex R\u00f6ntgen later discovered X-rays in tentatively suggested that atomic mathematics of electromagnetism. his laboratory in Germany. British weights might be a useful concept physician Thomas Young devised for chemists and ventured to Seeing the invisible a clever double-slit experiment to estimate a few of them. Fifteen Invisible forms of electromagnetic determine whether light is really a years later, Swedish chemist J\u00f6ns waves were discovered before wave or a particle. His discovery Jakob Berzelius drew up a much they were understood or the laws of wavelike interference appeared more complete list of atomic governing their behavior were to settle the argument. In Prague, weights. His student, the German \ufb01gured out. Working in Bath, Austrian physicist Christian chemist Friedrich W\u00f6hler, turned Britain, German astronomer Doppler explained the color an inorganic salt into an organic","A CENTURY OF PROGRESS 109 Charles Darwin August Kekul\u00e9 Dmitri Mendeleev lays Wilhelm R\u00f6ntgen outlines his theory of describes the out the periodic table discovers X-rays. evolution in On the chemical structure of the benzene of the elements. Origin of Species by Means of Natural molecule. Selection. 1859 1865 1869 1895 1859 1866 1873 1898 Louis Pasteur disproves Gregor Mendel James Clerk Maxwell Marie Curie spontaneous publishes his work on publishes his laws of isolates radioactive the genetics of peas. electromagnetism. generation of life. polonium. compound, and so disproved the Mary Anning documented a series and Charles Darwin both hit on idea that life chemistry operated of fossils of extinct creatures she the idea of evolution by means according to separate rules. In had dug out of the cliffs. Soon of natural selection. T. H. Huxley Paris, Louis Pasteur further showed afterward, Richard Owen coined demonstrated that birds may well that life cannot be generated the word \u201cdinosaurs\u201d to describe have evolved from dinosaurs, and spontaneously. Inspiration for new the \u201cterrible lizards\u201d that had once the evidence to support evolution ideas came from various quarters. roamed the planet. Swiss geologist mounted. Meanwhile, a German- The structure of the benzene Louis Agassiz suggested that large speaking Silesian friar named molecule came to German chemist parts of Earth had once been Gregor Mendel sorted out the August Kekul\u00e9 as he drifted off covered with ice, further expanding basic laws of genetics by studying to sleep, while Russian chemist the idea that Earth has experienced thousands of pea plants. Mendel\u2019s Dmitri Mendeleev used a pack of very different conditions through its work would be neglected for some cards to crack the problem of the history. Alexander von Humboldt decades, but its rediscovery would periodic table of the elements. used cross-disciplinary insights to provide the genetic mechanism Marie (Sk\u0142odowska) Curie isolated uncover the connections in nature for natural selection. polonium and radium, and became and established the study of the only person to win Nobel prizes ecology. In France, Jean-Baptiste In 1900, British physicist in both Chemistry and Physics. Lamarck outlined a theory of Lord Kelvin is alleged to have evolution, mistakenly believing said \u201cThere is nothing new to be Clues from the past that the passing on of acquired discovered in physics now. All The century saw nothing short of a characteristics was its driving that remains is more and more revolution in the understanding of force. Then, in the 1850s, British precise measurement.\u201d Little can life. On the south coast of England, naturalists Alfred Russel Wallace he have suspected what shocks were just around the corner. \u25a0","110 THE EXPERIMENTS MAY BE REPEATED WITH GREAT EASE WHENTHESUN SHINES THOMAS YOUNG (1773\u20131829) IN CONTEXT If light is made of particles A t the turn of the 19th that travel in straight century, scienti\ufb01c opinion BRANCH was divided over the Physics lines, then this can be proved question of the nature of light. Isaac in a simple experiment\u2026 Newton had argued that a beam BEFORE of light is made of countless, 1678 Christiaan Huygens \ufb01rst Shine a light through tiny, fast-moving \u201ccorpuscles\u201d proposes that light travels as two adjacent slits onto a (particles). If light consists of these waves. He publishes his screen. Two pools of light bulletlike corpuscles, he said, this Treatise on Light in 1690. would explain why light travels in should be seen on straight lines and casts shadows. 1704 In his book Opticks, the screen. Isaac Newton suggests that But Newton\u2019s corpuscles did not light comprises streams of But instead, it creates explain why light refracts (bends particles, or \u201ccorpuscles.\u201d interfering patterns of when it enters glass) or splits into light and dark, just as water the colors of the rainbow\u2014also AFTER waves would if water \ufb02owed an effect of refraction. Christiaan 1905 Albert Einstein argues Huygens had argued that light that light must be thought through two slits. comprises not particles, but waves. of as particles, later called If light travels as waves, Huygens photons, as well as waves. Light must travel as waves. said, it is easy to explain these effects. However, Newton\u2019s stature 1916 US physicist Robert was such that most scientists Andrews Millikan proves backed the particle theory. Einstein correct through experiment. Then, in 1801, British physician and physicist Thomas Young hit on 1961 Claus J\u00f6nsson repeats a design for a simple yet ingenious Young\u2019s double-slit experiment experiment that would, he believed, with electrons, and shows settle the question one way or the that, like light, they can other. The idea began when Young behave as waves as well was looking at the patterns of as particles. light made by a candle shining through a mist of \ufb01ne water droplets. The pattern showed colored rings around a bright","A CENTURY OF PROGRESS 111 See also: Christiaan Huygens 50\u201351 \u25a0 Isaac Newton 62\u201369 \u25a0 L\u00e9on Foucault 136\u201337 \u25a0 Albert Einstein 214\u201321 center, and Young wondered if the rings might be caused by interacting waves of light. The double-slit experiment Scienti\ufb01c investigations are Thomas Young Young made two slits in a piece of a sort of warfare carried on cardboard and shone a beam of against all one\u2019s contemporaries The eldest of 10 children light onto them. On a paper screen raised by Quaker parents in placed behind the slits, the light and predecessors. Somerset, England, Thomas created a pattern that convinced Thomas Young Young\u2019s brilliant mind made Young that it was waves. If light him a child prodigy, and he were streams of particles, as wavelength. For a century, Young\u2019s was nicknamed the \u201cYoung Newton said, there should simply double-slit experiment convinced Phenomenon.\u201d At 13, he could have been a strip of light directly scientists that light is a wave, not read \ufb01ve languages \ufb02uently\u2014 beyond each slit. Instead, Young a particle. Then in 1905, Albert as an adult, he made the saw alternating bright and dark Einstein showed that light also \ufb01rst modern translation of bands, like a fuzzy bar code. He behaves as if it were a stream of Egyptian hieroglyphics. argued that as light waves spread particles\u2014it can behave like a out beyond the slits, they interact. If wave and a particle. Such was the After medical training two waves ripple up (peak) or down simplicity of Young\u2019s experiment in Scotland, Young set up (trough) at the same time, they make that, in 1961, German physicist as a physician in London a wave twice as big (constructive Claus J\u00f6nsson used it to show that in 1799, but he was a true interference)\u2014creating the bright the subatomic particles electrons polymath who, in his spare bands. If one wave ripples up as the produce similar interference, so that time, conducted inquiries other ripples down, they cancel each they, too, must also be waves. \u25a0 into everything from a other out (destructive interference)\u2014 theory of musical tuning to creating the dark bands. Young also linguistics. He is most famous, showed that different colors of light however, for his work on light. create different interference In addition to establishing patterns. This demonstrated that the principle of interference the color of light depends on its of light, he devised the \ufb01rst modern scienti\ufb01c theory of Here, light travels Light waves color vision, arguing that through two slits in a piece we see colors as varying of card, and reaches a Card with proportions of the three main screen. The light waves two slits colors: blue, red, and green. passing through the slits interfere. Where peaks Destructive Key works (yellow) intersect with interference troughs (blue), there is 1804 Experiments and destructive interference. Pattern of light intensity Calculations Relative to Where peaks intersect Physical Optics with peaks and troughs 1807 Course of Lectures on with troughs, there is Natural Philosophy and the constructive interference. Mechanical Arts Constructive interference Screen","112 ASCERTAINING THE RELATIVE WEIGHTS OF ULTIMATE PARTICLES JOHN DALTON (1766\u20131844) IN CONTEXT Elements combine These \ufb01xed ratios must with each other to make depend on the relative BRANCH weight of the atoms of Chemistry compounds in simple \ufb01xed ratios. each element. BEFORE c.400 BCE Democritus Tables of elements Therefore, the atomic proposes that the world is should be based on weight of an element made of indivisible particles. the weights of their can be calculated from ultimate particles. the weight of each element 8th century CE Persian involved in a compound. polymath Jabir ibn Hayyan (or Geber) classi\ufb01es elements into T oward the end of the The idea of atoms dates back to metals and non-metals. 18th century, scientists ancient Greece, but it had always had begun to realize that been assumed that all atoms were 1794 Joseph Proust shows that the world is made up of a range identical. Dalton\u2019s breakthrough compounds are always made of basic substances, or chemical was to understand that each of elements combined in the elements. But no one was certain element is made from different same proportions. what an element was. It was John atoms. He described the atoms that Dalton, an English meteorologist, made up the elements then known\u2014 AFTER who, through his study of weather, including hydrogen, oxygen, and 1811 Amedeo Avogadro shows saw that each element is made nitrogen\u2014as \u201csolid, massy, hard, that equal volumes of different wholly of its own unique, identical impenetrable, moveable particles.\u201d gases contain equal numbers atoms, and it is this special atom of molecules. that distinguishes and de\ufb01nes Dalton\u2019s ideas originated in an element. In developing the his study of the way in which 1869 Dmitri Mendeleev draws atomic theory of elements, Dalton air pressure affected how much up a periodic table, displaying established the basis of chemistry. water could be absorbed by air. elements by atomic weight. He became convinced that air is 1897 Through his discovery of the electron, J. J. Thomson shows that atoms are not the smallest possible particle.","A CENTURY OF PROGRESS 113 See also: Joseph Proust 105 \u25a0 Dmitri Mendeleev 174\u201379 An inquiry into the by differences in their weights. Dalton\u2019s work had put scientists on relative weight of the ultimate He saw that the atoms, or \u201cultimate the right track, and within a decade particles of bodies is a subject, particles,\u201d of two or more elements Italian physicist Amedeo Avogadro as far as I know, entirely new. combined to make compounds in had devised a system of molecular very simple ratios, so he could proportions to calculate atomic John Dalton \ufb01gure out the weight of each atom weights correctly. Yet the basic by the weight of each element idea of Dalton\u2019s theory\u2014that each a mixture of different gases. As he involved in a compound. Very element has its own unique-sized experimented, he observed that a quickly, he \ufb01gured out the atomic atoms\u2014has proved to be true. \u25a0 given quantity of pure oxygen will weight of each element then known. take up less water vapor than the same amount of pure nitrogen, Hydrogen, Dalton realized, was and he jumped to the remarkable the lightest gas, so he assigned it conclusion that this is because an atomic weight of 1. Because oxygen atoms are bigger and of the weight of oxygen that heavier than nitrogen atoms. combined with hydrogen in water, he assigned oxygen an atomic Weighty matters weight of 7. However, there was a In a \ufb02ash of insight, Dalton \ufb02aw in Dalton\u2019s method, because realized that atoms of different he did not realize that atoms of the elements could be distinguished same element can combine. He always assumed that a compound of atoms\u2014a molecule\u2014had only one atom of each element. But Dalton\u2019s table shows symbols and atomic weights of different elements. Dalton was drawn to atomic theory through meteorology, when he asked himself why air and water particles could mix. John Dalton Born into a Quaker family in papers for the Society, including England\u2019s Lake District in 1766, those about his atomic theory. John Dalton made regular The atomic theory was quickly observations of the weather from accepted, and Dalton became a the age of 15. These provided celebrity in his own lifetime\u2014 many key insights, such as that more than 40,000 people atmospheric moisture turns to rain attended his funeral in when the air cools. In addition to Manchester in 1844. his meteorological studies, Dalton became fascinated by a condition Key works he and his brother shared: color blindness. His scienti\ufb01c paper on 1805 Experimental Enquiry into the subject gained him admission the Proportion of the Several to the Manchester Literary and Gases or Elastic Fluids, Philosophical Society, of which Constituting the Atmosphere he was elected president in 1817. 1808\u201327 New System of He wrote hundreds of scienti\ufb01c Chemical Philosophy","114 THE CHEMICAL EFFECTS PRODUCED BY ELECTRICITY HUMPHRY DAVY (1778\u20131829) IN CONTEXT I n 1800, Alessandro Volta Davy used apparatus similar to invented the \u201cvoltaic pile\u201d\u2014 this in his lectures at London\u2019s Royal BRANCH the world\u2019s \ufb01rst battery, and Institution to show how electrolysis Chemistry soon many other scientists began splits water into its two elements, to experiment with batteries. hydrogen and oxygen. BEFORE 1735 Swedish chemist English chemist Humphry Davy the same way and produced the Georges Brandt discovers realized that the battery\u2019s electricity metal sodium. In 1808, he used cobalt, the \ufb01rst of many new is produced by a chemical reaction. electrolysis to discover four more metallic elements to be found Electric charge \ufb02ows as the pile\u2019s metallic elements\u2014calcium, barium, over the next 100 years. two different metals (the electrodes) strontium, and magnesium\u2014and react via the brine-soaked paper the metalloid boron. Like electrolysis, 1772 Italian physician Luigi between them. In 1807, Davy found their commercial use would prove Galvani notices the effect that he could use the electric highly valuable. \u25a0 of electricity on a frog and charge from a pile to split chemical believes electricity is biological. compounds, discovering new elements, and pioneering a process 1799 Alessandro Volta shows that was later called electrolysis. that touching metals produce electricity, and creates the New metals \ufb01rst battery. Davy inserted two electrodes into dry potassium hydroxide (potash), AFTER which he moistened by exposing it 1834 Davy\u2019s former assistant to the damp air in his laboratory so Michael Faraday publishes the that it would conduct electricity. To laws of electrolysis. his delight, metallic globules began to form on the negatively charged 1869 Dmitri Mendeleev electrode. The globules were a new arranges the known elements element: the metal potassium. A into a periodic table, creating a few weeks later, he electrolyzed group for the soft alkali metals sodium hydroxide (caustic soda) in that Davy had been the \ufb01rst to identify in 1807. See also: Alessandro Volta 90\u201395 \u25a0 J\u00f6ns Jakob Berzelius 119 \u25a0 Hans Christian \u00d8rsted 120 \u25a0 Michael Faraday 121 \u25a0 Dmitri Mendeleev 174\u201379","A CENTURY OF PROGRESS 115 MAPPING THE ROCKS OF A NATION WILLIAM SMITH (1769\u20131839) IN CONTEXT I n the mid to late 18th century, France, who mapped the geology the need to \ufb01nd fuels and ores of the Paris Basin in 1811, and BRANCH to power Europe\u2019s Industrial William Smith in Britain. Geology Revolution spurred a growing interest in producing geological First national map BEFORE maps. German mineralogists Smith was a self-taught engineer 1669 Nicholas Steno publishes Johann Lehmann and Georg and surveyor who produced the \ufb01rst the principles of stratigraphy F\u00fcchsel produced detailed aerial nationwide geological map in 1815, that will guide geologists\u2019 views showing topography and showing England, Wales, and part understanding of rock strata. rock strata. Many subsequent of Scotland. By amassing samples geological maps did little more than from mines, quarries, cliffs, canals, 1760s In Germany, geologists show the surface distribution of and road and railroad cuttings, Johann Lehmann and Georg different rock types\u2014until the Smith established the succession F\u00fcchsel make some of the \ufb01rst pioneering work of Georges Cuvier of rock strata, using Steno\u2019s measured sections and maps and Alexandre Brongniart in principles of stratigraphy and of geological strata. identifying each stratum by its Organized fossils are to characteristic fossils. He also drew 1813 English geologist Robert the naturalist as coins vertical sections of the succession Bakewell makes the \ufb01rst of strata and the geological geognostic map of rock types to the antiquary. structures into which they had in England and Wales. William Smith been formed by earth movements. AFTER Over the next few decades, the 1835 The Geological Survey \ufb01rst national geological surveys of Great Britain is founded to were established, and they set conduct systematic geological about methodically mapping their mapping of the country. entire countries. The correlation of strata of similar age across national 1878 The \ufb01rst International boundaries was achieved by Geological Congress is held in international agreement in the Paris. Congresses have been latter part of the 19th century. \u25a0 held every three to \ufb01ve years ever since. See also: Nicholas Steno 55 \u25a0 James Hutton 96\u2013101 \u25a0 Mary Anning 116\u201317 \u25a0 Louis Agassiz 128\u201329","116 SHE KNOWS TO WHAT TRIBE THE BONES BELONG MARY ANNING (1799\u20131847) IN CONTEXT Fossils are the preserved Fossils have been remains of plants found of large animals BRANCH and animals. no longer around today. Paleontology In the past, very different animals lived on Earth. BEFORE 11th century Persian scholar B y the end of the 18th did they \ufb01t into the classi\ufb01cation Avicenna (Ibn Sina) suggests century, it was generally systems, and when had they that rocks can be formed from accepted that fossils become extinct? Within the Judeo- petri\ufb01ed \ufb02uids, leading to the were the remains of once living Christian culture of the Western formation of fossils. organisms that had been petri\ufb01ed world, it was generally thought that as the sediment around them a benevolent God would not have 1753 Carl Linnaeus includes hardened into rock. Both fossils allowed any of his creations to fossils in his system of and living organisms had been die out. biological classi\ufb01cation. classi\ufb01ed for the \ufb01rst time into a hierarchy of species, genera, Monsters from the abyss AFTER and families by naturalists such Some of the \ufb01rst of these large 1830 British artist Henry De as the Swedish taxonomist Carl and distinctive fossil remains were la Beche paints one of the \ufb01rst Linnaeus. However, fossil remains found by the Anning family of fossil paleo-reconstructions of a were still seen in isolation collectors around Lyme Regis on scene from \u201cdeep time.\u201d from their environmental and the coast of southern England. biological context. Here, Jurassic-period limestone and 1854 Richard Owen and shale strata outcrop in the cliffs, Benjamin Waterhouse In the early 19th century, the where they are eroded by the sea to Hawkins make the \ufb01rst discovery of large fossilized bones reveal abundant remains of ancient life-size reconstructions of unlike those of any living animal marine organisms.\u00a0In 1811, Joseph extinct plants and animals. raised many new questions. Where Early 20th century The development of radiometric dating techniques allows scientists to date fossils according to the rock strata in which they are found.","A CENTURY OF PROGRESS 117 See also: Carl Linnaeus 74\u201375 \u25a0 Charles Darwin 142\u201349 \u25a0 Thomas Henry Huxley 172\u201373 Anning found a 4 ft- (1.2 m-) long observed in 1824, Mary Anning Mary Anning skull with a curiously elongated was \u201cso thoroughly acquainted toothed beak. His sister Mary with the science that the moment Several biographies and found the rest of the skeleton, she \ufb01nds any bones she knows to novels have been written which they sold for about $37 (\u00a323). what tribe they belong.\u201d She about the life of Mary Anning, Exhibited in London, this was the became an authority on many a self-taught fossil collector. \ufb01rst entire skeleton of an extinct kinds of fossils, especially She was one of two surviving \u201cmonster of the abyss\u201d and coprolites\u2014fossilized dung. children out of 10 born into an attracted a great deal of popular impoverished Dorset family of attention. It was identi\ufb01ed as an The picture of life in ancient religious dissenters who lived extinct marine reptile and named Dorset revealed by Anning\u2019s fossils in the coastal village of Lyme an ichthyosaur, meaning \u201c\ufb01sh-lizard.\u201d was one of a tropical coast where Regis. The family eked out a a wide variety of now-extinct precarious living collecting The Anning family went on to animals thrived. In 1854, Anning\u2019s fossils for sale to the growing \ufb01nd more ichthyosaurs and the fossils provided models for the \ufb01rst numbers of tourists. However, \ufb01rst complete specimen of another life-size reconstruction of an it was Mary who found and marine reptile, the plesiosaur, ichthyosaur, made for London\u2019s sold their most signi\ufb01cant in addition to the \ufb01rst British Crystal Palace park by the sculptor \ufb01nds\u2014fossils of Jurassic specimen of a \ufb02ying reptile, new Benjamin Waterhouse Hawkins and reptiles that lived 201\u2013145 fossil \ufb01sh, and shell\ufb01sh. Among the the paleontologist Richard Owen. It million years ago. \ufb01sh they found were cephalopods was Owen who coined the word known as belemnites, some with \u201cdinosaur,\u201d but Anning who had Due to a combination of the ink-sac preserved. The family, provided the \ufb01rst glimpse of the her gender, humble social and especially Mary, had a talent richness of Jurassic life. \u25a0 standing, and religious for fossil hunting. Although poor, unorthodoxy, Anning received Mary was literate and taught In 1830, Henry De la Beche little formal recognition of her herself geology and anatomy, which painted this reconstruction of life in work in her lifetime, and she made her a far more effective fossil the Jurassic seas around Dorset based noted in a letter, \u201cThe world hunter. As Lady Harriet Sylvester on Anning\u2019s fossil discoveries. has used me unkindly, I fear it has made me suspicious of everyone.\u201d However, she was widely known in geological circles and various scientists sought out her expertise. When her health failed, Anning was provided with a small annual pension of about $40 (\u00a325) in recognition of her contribution to science. She died of breast cancer at 47.","118 THE INHERITANCE OF ACOUIRED CHARACTERISTICS JEAN-BAPTISTE LAMARCK (1744\u20131829) IN CONTEXT I n 1809, French naturalist What nature does in the Jean-Baptiste Lamarck course of long periods we do BRANCH introduced the \ufb01rst major theory every day when we suddenly Biology that life on Earth has evolved over change the environment in time. The impetus to his theory which some species of living BEFORE was the discovery of fossils of c.1495 Leonardo da Vinci creatures unlike any alive today. plant is situated. suggests in his notebook that In 1796, French naturalist Georges Jean-Baptiste Lamarck fossils are relics of ancient life. Cuvier had shown that fossilized elephant-like bones were markedly Lamarck believed characteristics 1796 Georges Cuvier proves different in anatomy from the bones were acquired during a creature\u2019s that fossil bones belong to of modern elephants, and must life and passed on. Later, Darwin extinct mastodons. come from extinct creatures now showed that changes occur because called mammoths and mastodons. mutations at conception survive 1799 William Smith shows the to be passed on through natural succession of fossils in rock Cuvier explained the vanished selection, and the idea of \u201cacquired strata of different ages. creatures of the past as victims of characteristics\u201d was ridiculed. But catastrophes. Lamarck challenged recently, scientists have argued that AFTER this idea, and argued that life the environment\u2014chemicals, light, 1858 Charles Darwin had \u201ctransmutated,\u201d or evolved, temperature, and food\u2014can in fact introduces his theory of gradually and continuously through alter genes and their expression. \u25a0 evolution by natural selection. time, developing from the simplest life forms to the most complex. A 1942 The \u201cmodern synthesis\u201d change in the environment, he reconciles Gregor Mendel\u2019s suggested, could spur a change in genetics with Darwin\u2019s natural the characteristics of an organism. selection, paleontology, and Those changes could then be ecology in trying to explain inherited through reproduction. how new species arise. Characteristics that were useful developed further; those that were 2005 Eva Jablonka and Marion not useful might disappear. Lamb claim that nongenetic, environmental, and behavioral See also: William Smith 115 \u25a0 Mary Anning 116\u201317 \u25a0 Charles Darwin 142\u201349 \u25a0 changes can affect evolution. Gregor Mendel 166\u201371 \u25a0 Thomas Hunt Morgan 224\u201325 \u25a0 Michael Syvanen 318\u201319","A CENTURY OF PROGRESS 119 EVERY CHEMICAL COMPOUND HAS TWO PARTS J\u00d6NS JAKOB BERZELIUS (1779\u20131848) IN CONTEXT T he leading light of a In 1803, Berzelius had teamed generation of chemists up with a mine owner to make a BRANCH inspired by Alessandro voltaic pile and see how electricity Chemistry Volta\u2019s creation of the battery, splits salts. Alkali metals and Sweden\u2019s J\u00f6ns Jakob Berzelius alkaline earths migrated to the BEFORE conducted a series of experiments pile\u2019s negative pole, while oxygen, 1704 Isaac Newton suggests looking at the effect of electricity on acids, and oxidized substances that atoms are bonded by chemicals. He developed a theory migrated to the positive pole. some force. called electrochemical dualism, He concluded that salt compounds published in 1819, which proposed combine a basic oxide, which is 1800 Alessandro Volta shows that compounds are created by the positively charged, and an acidic that placing two different coming together of elements with oxide, which is negatively charged. metals next to each other can opposite electrical charges. produce electricity, and so Berzelius developed his creates the \ufb01rst battery. The habit of an opinion dualistic theory to suggest that often leads to the complete compounds are bonded by the 1807 Humphry Davy discovers conviction of its truth, and attraction of opposite electrical sodium and other metal charges between their constituent elements by splitting salts makes us incapable of parts. Though later shown to be with electrolysis. accepting the proofs against it. incorrect, the theory triggered further research into chemical AFTER J\u00f6ns Jakob Berzelius bonds. In 1916, it was found that 1857\u201358 August Kekul\u00e9 electrical bonding occurs as \u201cionic\u201d and others develop the idea bonding, in which atoms lose or of valency\u2014the number of gain electrons to become mutually bonds an atom can form. attractive charged atoms, or ions. In fact, this is just one of several 1916 US chemist Gilbert ways in which the atoms in a Lewis proposes the idea of compound bind\u2014another is the the covalent bond in which \u201ccovalent\u201d bond, in which electrons electrons are shared, while are shared between atoms. \u25a0 German physicist Walther Kossel suggests the idea See also: Isaac Newton 62\u201369 \u25a0 Alessandro Volta 90\u201395 \u25a0 Joseph Proust 105 \u25a0 of ionic bonds. Humphry Davy 114 \u25a0 August Kekul\u00e9 160\u201365 \u25a0 Linus Pauling 254\u201359","120 THE ELECTRIC CONFLICT IS NOT RESTRICTED TO THE CONDUCTING WIRE HANS CHRISTIAN \u00d8RSTED (1777\u20131851) IN CONTEXT T he quest to discover an idea that there is a unity to nature, underlying unity to all \u00d8rsted now investigated the BRANCH forces and matter is as old possibility in earnest. Physics as science itself, but the \ufb01rst big break came in 1820, when the Chance discovery BEFORE Danish philosopher Hans Christian Lecturing at the University of 1600 William Gilbert conducts \u00d8rsted found a link between Copenhagen, \u00d8rsted wanted to the \ufb01rst scienti\ufb01c experiments magnetism and electricity. The link show his students how the electric on electricity and magnetism. had been suggested to him by the current from a voltaic pile (the German chemist and physicist battery invented by Alessandro 1800 Alessandro Volta creates Johann Wilhelm Ritter, whom he Volta in 1800) can heat up a wire the \ufb01rst electric battery. had met in 1801. Already in\ufb02uenced and make it glow. He noticed that a by the philosopher Immanuel Kant\u2019s compass needle standing near the AFTER wire moved every time the current 1820 Andr\u00e9-Marie Amp\u00e8re It appears that the electric was switched on. This was the \ufb01rst develops a mathematical con\ufb02ict is not restricted to the proof of a link between electricity theory of electromagnetism. and magnetism. Further study conducting wire, but that it convinced him that the current 1821 Michael Faraday is able has a rather extended sphere produced a circular magnetic \ufb01eld to show electromagnetic as it \ufb02owed through the wire. rotation in action, by creating of activity around it. the \ufb01rst electric motor. Hans Christian \u00d8rsted \u00d8rsted\u2019s discovery rapidly prompted scientists across Europe 1831 Faraday and US scientist to investigate electromagnetism. Joseph Henry independently Later that year, French physicist discover electromagnetic Andr\u00e9-Marie Amp\u00e8re formulated induction; Faraday uses it in a mathematical theory for the the \ufb01rst generator to convert new phenomenon and, in 1821, motion into electricity. Michael Faraday demonstrated that electromagnetic force could convert 1864 James Clerk Maxwell electrical into mechanical energy. \u25a0 formulates a set of equations to describe electromagnetic See also: William Gilbert 44 \u25a0 Alessandro Volta 90\u201395 \u25a0 Michael Faraday 121 \u25a0 waves\u2014including light waves. James Clerk Maxwell 180\u201385","A CENTURY OF PROGRESS 121 ONE DAY, SIR, YOU MAY TAX IT MICHAEL FARADAY (1791\u20131867) IN CONTEXT British scientist Michael In Faraday\u2019s apparatus for showing Faraday\u2019s discovery of electromagnetic induction, a current BRANCH the principles of both the \ufb02ows through the small magnetic coil, Physics electric motor and the electric which is moved in and out of the large generator paved the way for the coil, inducing a current in it. BEFORE electrical revolution that would 1800 Alessandro Volta invents transform the modern world, Generating electricity the \ufb01rst electric battery. bringing everything from lightbulbs Ten years later, Faraday made an to telecommunications. Faraday even more important discovery\u2014 1820 Hans Christian \u00d8rsted himself foresaw the value of that a moving magnetic \ufb01eld can discovers that electricity his discoveries\u2014and the tax create or \u201cinduce\u201d a current of creates a magnetic \ufb01eld. revenues they could generate electricity. This discovery\u2014which for government. was also made independently by 1820 Andr\u00e9-Marie Amp\u00e8re the US physicist Joseph Henry formulates a mathematical In 1821, a few months after around the same time\u2014is the theory of electromagnetism. hearing of Hans Christian \u00d8rsted\u2019s basis for generating all electricity. discovery of the link between Electromagnetic induction converts AFTER electricity and magnetism, Faraday the kinetic energy in a spinning 1830 Joseph Henry creates the demonstrated how a magnet will turbine into electrical current. \u25a0 \ufb01rst powerful electromagnet. move around an electric wire, and an electric wire will move around a 1845 Faraday demonstrates magnet. The electric wire produces the link between light and a circular magnetic \ufb01eld around it, electromagnetism. which generates a tangential force on the magnet, producing circular 1878 Designed by Sigmund motion. This is the principle behind Schuckert, the \ufb01rst steam- the electric motor. A spinning driven power station generates motion is set up by alternating the electricity for the Linderhof direction of the current, which Palace in Bavaria, Germany. alternates the direction of the magnetic \ufb01eld in the wire. 1882 US inventor Thomas Edison builds a power station See also: Alessandro Volta 90\u201395 \u25a0 Hans Christian \u00d8rsted 120 \u25a0 to power electric lighting in James Clerk Maxwell 180\u201385 Manhattan, New York City.","122 HEAT PENETRATES EVERY SUBSTANCE IN THE UNIVERSE JOSEPH FOURIER (1777\u20131831) IN CONTEXT Heat penetrates T oday, one of the most every substance fundamental laws of BRANCH in the universe. physics is that energy Physics is neither created nor destroyed, There is a temperature but only changes from one form to BEFORE gradient between warmer another or moves from one place 1761 Joseph Black discovers to another. French mathematician latent heat\u2014the heat taken up places and cooler places. Joseph Fourier was a pioneer in the by ice to melt and water to boil study of heat and how heat moves without changing temperature. Heat is transferred across from warm places to cool places. He also studies speci\ufb01c heat\u2014 the temperature gradient in required by substances to Fourier was interested in both raise their temperature by a a wavelike movement. how heat diffused through solids by certain amount. conduction and how things cooled Mathematically, a series down by losing heat. His compatriot 1783 Antoine Lavoisier and of sine and cosine Jean-Baptiste Biot had imagined Pierre-Simon Laplace measure the spread of heat as \u201caction at a latent heat and speci\ufb01c heat. functions can be used to distance,\u201d in which it spreads by represent the movement. jumping from warm places to cool. AFTER Biot represented the heat \ufb02ow in 1824 By developing the a solid as a series of slices, which \ufb01rst theory of heat engines, allowed it to be studied with which turn heat energy into conventional equations showing mechanical energy, Nicolas the heat jumping from one slice Sadi Carnot provides the to the next. foundations for the theory of thermodynamics. Temperature gradients Fourier looked at heat \ufb02ow in an 1834 \u00c9mile Clapeyron shows entirely different way. He focused that energy must always on temperature gradients\u2014 become more diffuse, continuous gradations between formulating the second law warm and cool places. These could of thermodynamics. not be quanti\ufb01ed with conventional equations, so he devised new mathematical techniques.","A CENTURY OF PROGRESS 123 See also: Isaac Newton 62\u201369 \u25a0 Joseph Black 76\u201377 \u25a0 Antoine Lavoisier 84 \u25a0 Charles Keeling 294\u201395 Mathematics compares the These individual waves each move A Fourier series can approximate most diverse phenomena and uniformly from a peak to a trough. a wave of any shape\u2014even a square discovers the secret analogies Adding more and more of these one (shown here in pink). Adding more simple waves together produces sine waves to the series gives a closer that unite them. increasing complexity that can and closer approximation of the square Joseph Fourier approximate any other type of wave. The \ufb01rst four approximations in wave. These in\ufb01nite series are the series (shown here in black) each Fourier focused on the idea of now called Fourier series. incorporate an extra sine wave. waves, and \ufb01nding a way to represent them mathematically. Fourier published his idea in He saw that every wavelike 1807, but it attracted criticism, and movement, which is what a it was not until 1822 that his work temperature gradient is, can be was \ufb01nally accepted. Continuing approximated mathematically by his study of heat, in 1824, Fourier adding together simpler waves, examined the difference between whatever the shape of the wave to the heat that Earth gains from the be represented. The simpler waves Sun and the heat it loses to space. that are to be added together are He realized that the reason Earth is sines and cosines, derived from pleasantly warm, considering how trigonometry, and can be written far it is from the Sun, is because out mathematically as a series. gases in its atmosphere trap heat and stop it from being radiated back into space\u2014the phenomenon now called the greenhouse effect. Today, Fourier analysis is applied not only to heat transfer but also to a host of problems at the cutting edge of science, ranging from acoustics, electrical engineering, and optics to quantum mechanics. \u25a0 Joseph Fourier The son of a tailor, Joseph Fourier to France in 1801, Fourier was was born in Auxerre, France. made governor of Is\u00e8re in the Orphaned at 10, he was taken Alps. In between administrative into a local convent before going duties overseeing road building on to a military school, where he and drainage planning, he excelled at mathematics. France published a groundbreaking was in the throes of revolution, study of ancient Egypt and and during the Terror of 1794, he started his studies of heat. He was brie\ufb02y imprisoned after died in 1831 after tripping and falling out with fellow falling down a \ufb02ight of stairs. revolutionaries. Key works After the Revolution, Fourier accompanied Napoleon on an 1807 On the Propagation of expedition to Egypt in 1798. Heat in Solid Bodies He was made governor of Egypt 1822 The Analytic Theory and put in charge of the study of of Heat ancient Egyptian relics. Returning","124 THE ARTIFICIAL PRODUCTION OF ORGANIC SUBSTANCES FROM INORGANIC SUBSTANCES FRIEDRICH W\u00d6HLER (1800\u20131882) IN CONTEXT I n 1807, the Swedish chemist endowed with a \u201clife force\u201d beyond J\u00f6ns Jakob Berzelius suggested the understanding of chemists. BRANCH that a fundamental difference So it came as a surprise when Chemistry existed between the chemicals the pioneering experiments of a involved in living things and all German chemist named Friedrich BEFORE other chemicals. These unique, W\u00f6hler showed that organic 1770s Antoine Lavoisier and \u201corganic\u201d chemicals, Berzelius chemicals are not unique at all, others show that water and argued, could only be assembled by but behave according to the same salt can return to their former living things themselves and, once basic rules as all chemicals. state after heating, but sugar broken down, could not be remade or wood cannot. arti\ufb01cially. His idea conformed with We now know that organic the prevailing theory known as chemicals comprise a multitude of 1807 J\u00f6ns Jakob Berzelius \u201cvitalism,\u201d which held that life was molecules based on the element suggests a fundamental special and that living things were carbon. These carbon-based difference between organic molecules are indeed essential and inorganic chemicals. components of life, but many can be synthesized from inorganic AFTER chemicals\u2014as W\u00f6hler discovered. 1852 British chemist Edward Franklin suggests the idea of Widely used in fertilizers, urea is Chemistry rivals valency, the ability of atoms to rich in nitrogen, which is essential to W\u00f6hler\u2019s breakthrough came about combine with other atoms. the growth of plants. Synthetic urea, because of a scienti\ufb01c rivalry. In \ufb01rst made by W\u00f6hler, is now a key raw the early 1820s, W\u00f6hler and fellow 1858 British chemist material in the chemical industry. chemist Justus von Liebig both Archibald Couper suggests the came up with identical chemical idea of bonds between atoms, analyses for what seemed to be two explaining how valency works. very different substances\u2014silver fulminate, which is explosive, and 1858 Couper and August silver cyanate, which is not. Both Kekul\u00e9 propose that organic men assumed that the other had chemicals are made by chains the wrong results, but after of bonded carbon atoms with corresponding, they found they side branches of other atoms. were both right. This group of compounds led chemists to realize that substances are de\ufb01ned not just","A CENTURY OF PROGRESS 125 See also: Antoine Lavoisier 84 \u25a0 John Dalton 112\u201313 \u25a0 J\u00f6ns Jakob Berzelius 119 \u25a0 Leo Baekeland 140\u201341 \u25a0 August Kekul\u00e9 160\u201365 Some chemists think that Yet by mixing two organic chemicals found ordinary chemicals in the in living things are unique lab, we can produce and can only be made urea\u2014the organic by living things. chemical in urine. Organic substances We can make Friedrich W\u00f6hler are not unique. organic substances Born in Eschersheim, near from inorganic Frankfurt in Germany, substances. Friedrich W\u00f6hler trained in obstetrics at the University by the number and kinds of atoms a key component of urine, and has of Heidelberg. But chemistry in the molecule but also by the the same chemical formula as was his passion and, in 1823, atoms\u2019 arrangement. The same ammonium cyanate. According to he went to study with J\u00f6ns formula may apply to different Berzelius\u2019s theory, it could be made Jakob Berzelius in Stockholm. structures with different only by living things\u2014yet W\u00f6hler On his return to Germany, he properties\u2014these different had synthesized it from inorganic embarked on a remarkable structures were later named chemicals. W\u00f6hler wrote to Berzelius: and varied career in chemical isomers by Berzelius. \u201cI must tell you that I can make research and innovation. urea without the use of kidneys,\u201d W\u00f6hler and Liebig went on to explaining that urea was in fact an Besides the \ufb01rst arti\ufb01cial forge a brilliant partnership, but it isomer of ammonium cyanate. synthesis of an organic was W\u00f6hler alone who, in 1828, substance, W\u00f6hler\u2019s many stumbled upon the truth about The signi\ufb01cance of W\u00f6hler\u2019s discoveries\u2014often made with organic chemicals. discovery took many years to sink Justus von Liebig\u2014included in. Even so, it paved the way for the aluminum, beryllium, yttrium, The W\u00f6hler synthesis development of modern organic titanium, and silicon. He also W\u00f6hler was mixing silver cyanate chemistry, which not only reveals helped to develop the idea of with ammonium chloride, expecting how all living things depend on \u201cradicals\u201d\u2014basic molecular to get ammonium cyanate. Instead, chemical processes, but enables groups from which other he got a white substance that had the arti\ufb01cial synthesis of valuable substances are built. Although different properties from ammonium organic chemicals on a commercial later disproved, this theory cyanate. The same powder appeared scale. In 1907, a synthetic polymer paved the way for today\u2019s when he mixed lead cyanate with called Bakelite was produced from understanding of how ammonium hydroxide. Analysis two such chemicals and ushered in molecules assemble. In later showed the white powder to be the \u201cAge of Plastics\u201d that shaped years, W\u00f6hler became an urea\u2014an organic substance that is the modern world. \u25a0 authority on the chemistry of meteorites and helped set up a factory for purifying nickel. Key works 1830 Summary of Inorganic Chemistry 1840 Summary of Organic Chemistry","126 WINDS NEVER BLOW IN A STRAIGHT LINE GASPARD-GUSTAVE DE CORIOLIS (1792\u20131843) IN CONTEXT A ir and ocean currents do Earth\u2019s rotation causes winds to be not \ufb02ow in straight lines. de\ufb02ected to the right in the northern BRANCH As the currents move, hemisphere and left in the southern. Meteorology they are de\ufb02ected to the right in the northern hemisphere, and Initial direction De\ufb02ected BEFORE to the left in the southern. In the right 1684 Isaac Newton introduces 1830s, French scientist Gaspard- the idea of centripetal force, Gustave de Coriolis discovered the stating that any motion in a principle behind this effect, now curved path must be the result known as the Coriolis effect. of a force acting on it. De\ufb02ected by rotation De\ufb02ected left Initial direction 1735 George Hadley suggests Coriolis got his ideas from that trade winds blow toward studying turning waterwheels, simply blow straight from high the equator because Earth\u2019s but meteorologists later realized pressure areas to low pressure rotation de\ufb02ects air currents. that the ideas apply to the way areas. The wind direction is in fact winds and ocean currents move. a balance between the pull of low AFTER pressure and the Coriolis de\ufb02ection. 1851 L\u00e9on Foucault shows Coriolis showed how, when an This is mostly why winds circle how the swing of a pendulum object is moving across a rotating counterclockwise into low pressure is de\ufb02ected by Earth\u2019s rotation. surface, its momentum seems to zones in the northern hemisphere, carry it on a curved path. Imagine and clockwise in the southern 1856 US meteorologist William throwing a ball out from the center hemisphere. Similarly, ocean Ferrel shows that winds blow of a spinning merry-go-round. The surface currents circulate in parallel to isobars\u2014lines that ball appears to curve around\u2014even giant loops or gyres, clockwise connect points of equal though to anyone watching from in the northern hemisphere and atmospheric pressure. outside the merry-go-round it is counterclockwise in the south. \u25a0 actually moving in a straight line. 1857 Dutch meteorologist Christophorus Buys Ballot Winds on the rotating Earth are formulates a rule stating that de\ufb02ected in the same way. Without if the wind is blowing on your the Coriolis effect, winds would back, an area of low pressure is to your left. See also: George Hadley 80 \u25a0 Robert FitzRoy 150\u201355","A CENTURY OF PROGRESS 127 ON THE COLORED LIGHT OF THE BINARY STARS CHRISTIAN DOPPLER (1803\u20131853) IN CONTEXT T he color of light depends The colors of stars are now on its frequency, which known to be mainly due to their BRANCH is the number of waves temperature (the hotter the star, Physics per second. If something moving the more blue it appears), but the toward us is emitting waves, the movement of some stars can be BEFORE second wave will have a shorter detected through Doppler shifts. 1677 Ole R\u00f8mer estimates distance to travel than the \ufb01rst Binary stars are pairs of stars the speed of light by studying wave, so it will arrive sooner than it orbiting each other. Their rotation Jupiter\u2019s moons. would if the source were stationary. causes an alternating redshift and Thus the frequency of waves blueshift in the light they emit. \u25a0 AFTER increases if the source and receiver 1840s Dutch meteorologist are getting closer to each other, and The heavens presented an Christophorus Buys Ballot decreases if they are moving apart. extraordinary appearance, for applies the Doppler shift to This effect applies to all types of all the stars directly behind sound waves, as does French wave, including sound, and is me were now deep red, while physicist Hippolyte Fizeau to responsible for the changing pitch electromagnetic waves. of a siren as an ambulance passes. those directly ahead were violet. Rubies lay behind me, 1868 British astronomer To the naked eye, most stars William Huggins uses redshift appear to be white, but through amethysts ahead of me. to \ufb01nd the velocity of a star. a telescope many can be seen to Olaf Stapledon be red, yellow, or blue. In 1842, an 1929 Edwin Hubble relates Austrian physicist named Christian From his novel, Star Maker (1937) the redshift of galaxies to their Doppler suggested that the red color distance from Earth, showing of some stars is due to the fact that the expansion of the universe. they are moving away from the Earth, which would shift their light 1988 The \ufb01rst extrasolar to longer wavelengths. Since the planet is detected, using the longest wavelength of visible light is Doppler shift of light from red, this became known as redshift the star that it orbits\u2014the (as illustrated on p.241). star appears to \u201cwobble\u201d as the planet\u2019s gravitational See also: Ole R\u00f8mer 58\u201359 \u25a0 Edwin Hubble 236\u201341 \u25a0 Geoffrey Marcy 327 pull disrupts its rotation.","128 THE GLACIER WAS GOD\u2019S GREAT PLOUGH LOUIS AGASSIZ (1807\u20131873) IN CONTEXT Retreating glaciers leave particular features behind them in the landscape. BRANCH Earth science These features are found in areas where there are no glaciers. BEFORE There must have been glaciers in these 1824 Norwegian Jens Esmark places some time in the past. suggests that glaciers are responsible for the creation of W hen glaciers sweep which is the usual way that rocks fjords, erratics, and moraines. across a landscape, are carried across a landscape. A they leave signature rock of a different kind from rocks 1830 Charles Lyell argues that features behind them. Glaciers around it, therefore, is a telltale the laws of nature have always can scour rocks \ufb02at or leave them sign that a glacier once passed been the same, so the clues to smoothly rounded, often with by. Another is the presence of the past lie in the present. striations (scratch marks) showing moraines in valleys. These are piles the direction in which the ice of boulders that were pushed aside 1835 Swiss geologist Jean moved. They also leave behind when the glacier was growing, and de Charpentier argues that erratics\u2014boulders that have been left behind when it retreated. erratics near Lake Geneva carried long distances by the ice. were transported by ice from These can usually be identi\ufb01ed Riddle of the rocks the Mont Blanc area in an because their composition is Geologists in the 19th century \u201cAlpine glaciation.\u201d different from the rocks on which recognized such features as they lie. Many erratics are too large striations, erratics, and moraines AFTER to have been moved by rivers, as evidence of glaciers. What they 1875 Scottish scientist James Croll argues that variations in Earth\u2019s orbit could explain the temperature changes that cause an ice age. 1938 Serbian physicist Milutin Milankovic relates changes in climate to periodic changes in Earth\u2019s orbit.","A CENTURY OF PROGRESS 129 See also: WIlliam Smith 115 \u25a0 Alfred Wegener 222\u201323 could not explain was why such Agassiz wanted to convince others. Louis Agassiz features were found in areas on He had met William Buckland, a Earth that had no glaciers. One prominent English geologist, while Born in a small Swiss village theory argued that rocks were excavating fossil \ufb01shes in the Old in 1807, Louis Agassiz studied moved by repeated \ufb02ooding. Floods Red Sandstone rocks in the Alps. to be a physician, but became could explain the \u201cboulder drift\u201d When Agassiz showed him the a professor of natural history (the sands, clays, and gravels that evidence for his theory of an ice at the University of Neuch\u00e2tel. included erratic boulders) that age, Buckland was convinced, His \ufb01rst scienti\ufb01c work, under overlay much of the bedrock of and in 1840 the two men toured the French naturalist Georges Europe. The material might have Scotland to look for evidence of Cuvier, involved classifying been deposited when the last \ufb02ood glaciation there. After the tour, freshwater \ufb01sh from Brazil, retreated. The largest erratics could Agassiz presented his ideas to and Agassiz went on to have been caught up in icebergs, the Geological Society of London. undertake extensive work which deposited the rocks when Although he had convinced on fossilized \ufb01sh. In the late they melted. But the theory could Buckland and Charles Lyell\u2014two 1830s, his interests spread not explain all of the features. of the leading geologists of the to glaciers and zoological day\u2014the other members of the classi\ufb01cation. In 1847, he took The ice age revealed society were unimpressed. A nearly a post at Harvard University During the 1830s, Swiss geologist global glaciation seemed no more in the US. Louis Agassiz spent several probable than a global \ufb02ood. vacations in the European Alps However, the idea of ice ages Agassiz never accepted studying glaciers and their valleys. gradually gained acceptance, and Darwin\u2019s theory of evolution, He realized that glacial features today there is evidence from many believing that species were everywhere, not just in the Alps, different \ufb01elds of geology that ice \u201cideas in the mind of God\u201d could be explained if Earth had has covered much of Earth\u2019s and that all species had been once been covered in far more surface many times in the past. \u25a0 created for the regions they ice than at present. The glaciers inhabited. He advocated of today must be the remnants of Agassiz was the \ufb01rst to suggest \u201cpolygenism,\u201d a belief that ice sheets that had at one time that large erratics, such as these in the different human races did not covered most of the globe. But Caher Valley of Ireland, were deposited share a common ancestor, but before he published his theory by ancient glaciers. were created separately by God. In recent years, his reputation has been tarnished by his apparent advocacy of racist ideas. Key works 1840 Study on Glaciers 1842\u201346 Nomenclator Zoologicus","NATURE CAN BE REPRESENTED AS ONE GREAT WHOLE ALEXANDER VON HUMBOLDT (1769\u20131859)","","132 ALEXANDER VON HUMBOLDT IN CONTEXT T he study of the The principal impulse by interrelationship between which I was directed was the BRANCH the animate and inanimate BIOLOGY world, known as ecology, only earnest endeavour to became a subject of rigorous and comprehend the phenomena BEFORE methodical scienti\ufb01c investigation of physical objects in their 5th\u20134th century BCE Ancient over the last 150 years. The term general connection, and to Greek writers observe the \u201cecology\u201d was coined in 1866 by represent nature as one great web of interrelationships the German evolutionary biologist, whole, moved and animated between plants, animals, Ernst Haeckel, and is derived from and their environment. the Greek words oikos, meaning by internal forces. house or dwelling place, and logos, Alexander von Humboldt AFTER meaning study or discourse. But 1866 Ernst Haeckel coins it is an earlier German polymath by ancient Greek writers, such as the word \u201cecology.\u201d named Alexander von Humboldt Herodotus in the 5th century BCE. who is regarded as the pioneer of In one of the \ufb01rst accounts of 1895 Eugenius Warming modern ecological thinking. interdependence, technically publishes the \ufb01rst university known as mutualism, he describes course book on ecology. Through extensive expeditions crocodiles on the Nile River in and writings, Humboldt promoted Egypt opening their mouths to 1935 Alfred Tansley coins the a new approach to science. He allow birds to pick their teeth clean. word \u201cecosystem.\u201d sought to understand nature as a uni\ufb01ed whole, by interrelating A century later, observations 1962 Rachel Carson warns of all of the physical sciences and by the Greek philosopher Aristotle the dangers of pesticides in employing the latest scienti\ufb01c and his pupil Theophrastus on Silent Spring. equipment, exhaustive observation, species\u2019 migration, distribution, and meticulous analysis of data on and behavior provided an early 1969 Friends of the Earth and an unprecedented scale. version of the concept of the Greenpeace are established. ecological niche\u2014the particular The crocodile\u2019s teeth place in nature that shapes and is 1972 James Lovelock\u2019s Gaia Although Humboldt\u2019s holistic shaped by a species\u2019 way of life. hypothesis presents Earth as approach was new, the concept Theophrastus studied and wrote a single organism. of ecology developed from early extensively on plants, realizing the investigations of natural history importance of climate and soils to their growth and distribution. Their ideas in\ufb02uenced natural philosophy for the next 2,000 years. Humboldt\u2019s team climbed Mexico\u2019s Jorullo volcano in 1803, just 44 years after it \ufb01rst appeared. Humboldt linked geology to meteorology and biology by studying where different plants lived.","A CENTURY OF PROGRESS 133 See also: Jean-Baptiste Lamarck 118 \u25a0 Charles Darwin 142\u201349 \u25a0 James Lovelock 315 Nature\u2019s unifying forces as a means of characterizing and showed the global application Humboldt\u2019s approach to nature mapping the global environment, of these zones by comparing the followed in the late 18th-century especially the climate, and then Andean zones with those of the Romantic tradition that reacted comparing the climatic conditions European Alps, Pyrenees, Lapland, to rationalism by insisting on the in various countries. Tenerife, and the Asian Himalayas. value of senses, observation, and experience in understanding Humboldt was also one of De\ufb01ning ecology the world as a whole. Like his the \ufb01rst scientists to study how When Haeckel coined the word contemporaries, the poets Johann physical conditions\u2014such as \u201cecology,\u201d he too was following in Wolfgang von Goethe and Friedrich climate, altitude, latitude, and the tradition of viewing a Gestalt Schiller, Humboldt promoted the soils\u2014affected the distribution of (unity) of the living and inanimate idea of the unity (or Gestalt in life. With Bonpland\u2019s assistance, he world. An enthusiastic evolutionist, German) of nature\u2014and of natural mapped the changes in \ufb02ora and he was inspired by Charles Darwin, philosophy and the humanities. His fauna between sea level and high whose publication of On the Origin studies ranged from anatomy and altitude in the Andes. In 1805, of Species in 1859 banished the astronomy to mineralogy and the year after his return from the notion of Earth as an immutable botany, commerce, and linguistics, Americas, he published a now- world. Haeckel questioned the role and provided him with the breadth celebrated work on the geography of natural selection, but believed of knowledge necessary for his of the area, summarizing the that the environment played an exploration of the natural world interconnectedness of nature and important role in both evolution beyond the con\ufb01nes of Europe. illustrating the altitudinal zones of and ecology. \u276f\u276f vegetation. Years later, in 1851, he As Humboldt explained, \u201cThe sight of exotic plants, even of dried Ecology is the study of all the interactions specimens in a herbarium, \ufb01red my between organisms and their environment that imagination and I longed to see the tropical vegetation in southern determine their distribution and abundance. countries with my own eyes.\u201d His \ufb01ve-year exploration of Latin These interactions must include\u2026 America with the French botanist Aim\u00e9 Bonpland was his most \u2026biotic factors, such \u2026abiotic factors, such important expedition. Setting out as human activity and animal as climate, soils, and the in June 1799, he declared, \u201cI shall collect plants and fossils, and make and plant communities. hydrological cycle. astronomical observations with the best of instruments. Yet this is not Nature can be represented the main purpose of my journey. I as one great whole. shall endeavor to discover how nature\u2019s forces act upon one another and in what manner the geographic environment exerts its in\ufb02uence on animals and plants. In short, I must \ufb01nd out about the harmony in nature.\u201d And he did just that. Among many other projects, Humboldt measured ocean water temperature and suggested the use of \u201cisolines,\u201d or isothermal lines, to connect points of equal temperature","134 ALEXANDER VON HUMBOLDT By the end of the 19th century, the encompassing all those factors that This whole chain of \ufb01rst university course in ecology in\ufb02uence it\u2014both biotic (living poisoning, then, seems was being taught by the Danish organisms) and abiotic (nonliving to rest on a base of minute botanist Eugenius Warming, factors such as soil, water, air, plants which must have been who also wrote the \ufb01rst ecology temperature, and sunlight). The the original concentrators. textbook Plantesamfund (Plant scope of modern ecology ranges Ecology) in 1895. From Humboldt\u2019s from the individual organism to Rachel Carson pioneering work, Warming populations of individuals of the developed the global geographical same species, and the community, which successive communities subdivision of plant distribution made up of populations that share of different species adjust to one known as biomes, such as the a particular environment. another to form a tightly integrated tropical rain-forest biome, which and interdependent unit, similar are largely based on the interaction Many of the basic terms and to the organs of a body. Clements\u2019 of plants with the environment, concepts of ecology came from the metaphor of the community as a especially climate. work of several pioneer ecologists \u201ccomplex organism\u201d was criticized in the \ufb01rst few decades of the 20th at \ufb01rst but in\ufb02uenced later thinking. Individuals and community century. The formal concept of the Early in the 20th century, the biological community was \ufb01rst The idea of further ecological modern de\ufb01nition of ecology developed in 1916 by the American integration at a higher level than developed as the scienti\ufb01c study botanist Frederic Clements. He the community was introduced of the interactions that determine believed that the plants of a given in 1935 with the concept of the the distribution and abundance area develop a succession of ecosystem, developed by the of organisms. These interactions communities over time, from English botanist Arthur Tansley. include an organism\u2019s environment, an initial pioneer community to an An ecosystem consists of both optimal climax community within living and nonliving elements. Their interaction forms a stable A food chain transfers energy from primary unit with a sustaining \ufb02ow of producers (plants and algae that convert the Sun\u2019s energy from the environmental energy into food energy) to consumer organisms that to the living part (through the food eat the plants (such as rabbits and other herbivores), chain) and can operate on all and then to the predators that feed on the consumers. scales, from a puddle to an ocean or the whole planet. Lion, an apex Jackal predator (not preyed Studies of animal communities Goat by the English zoologist Charles on by others) Elton led him to develop in 1927 the Green concept of the food chain and food Kite plants cycle, subsequently known as the Wild cat \u201cfood web.\u201d A food chain is formed Rabbit by the transfer of energy through an Owl Mouse ecosystem from primary producers (such as green plants on land) Snake through a series of consuming","A CENTURY OF PROGRESS 135 Rachel Carson (far right) made a signi\ufb01cant contribution to the science and public understanding of ecology by drawing attention to the destructive impact of pollution on the environment. organisms. Elton also recognized harmful effects on the environment renewable energy, organic foods, that particular groups of organisms of man-made chemicals such as recycling, and sustainability, were occupied certain niches in the food the pesticide DDT. The \ufb01rst image all on the political agenda in both chain for periods of time. Elton\u2019s of Earth seen from space, taken North America and Europe, and niches include not only the habitats by Apollo 8 astronauts in 1968, national conservation agencies but also the resources upon which awakened public awareness of were established based on the the occupying organisms rely for the planet\u2019s fragility. In 1969, the science of ecology. Recent decades sustenance. The dynamics of organizations Friends of the Earth have seen growing concern over energy transfer through trophic and Greenpeace were established, global climate change and its (feeding) levels were studied by with the mission to \u201censure the impact on the environment and the American ecologists Raymond ability of the Earth to nurture life present ecosystems, many of Lindeman and Robert MacArthur, in all its diversity.\u201d Environmental which are already threatened whose mathematical models protection, along with clean and from human activity. \u25a0 helped change ecology from primarily a descriptive science into an experimental one. The green movement A boom in popular and scienti\ufb01c interest in ecology in the 1960s and 1970s led to the development of the environmental movement with a whole range of concerns, stimulated by powerful advocates such as the American marine biologist Rachel Carson. Her 1962 book Silent Spring documented the Alexander von Born in Berlin to a wealthy and On his return, Humboldt was Humboldt well-connected family, Humboldt honored across Europe. Based in studied \ufb01nance at the University Paris, he took 21 years to process of Frankfurt, natural history and and publish his data in over 30 linguistics in G\u00f6ttingen, language volumes, and then synthesized and commerce in Hamburg, his ideas in four volumes titled geology in Freiburg, and anatomy Kosmos. A \ufb01fth volume was in Jena. The death of his mother in completed after his death in 1796 provided Humboldt with the Berlin at 89. Darwin called him means to fund an expedition to \u201cthe greatest scienti\ufb01c traveller the Americas from 1799 to 1804, who ever lived.\u201d accompanied by botanist Aim\u00e9 Bonpland. Using the latest Key works scienti\ufb01c equipment, Humboldt measured everything from plants 1825 Journey to the Equinoctial to population statistics and Regions of the New Continent minerals to meteorology. 1845\u20131862 Kosmos","136 LIGHT TRAVELS MORE SLOWLY IN WATER THAN IN AIR L\u00c9ON FOUCAULT (1819\u20131868) IN CONTEXT Is light a stream Whichever it is, of particles or a wave? light takes time BRANCH Physics to travel. BEFORE Foucault found Newton thought 1676 Ole R\u00f8mer makes the that light travels light particles would \ufb01rst successful estimate of the speed up going from air speed of light, using eclipses more slowly in to water, while Huygens of Io, one of Jupiter\u2019s moons. water than in air. thought waves would 1690 Christiaan Huygens slow down. publishes his Treatise on Light, in which he proposes Therefore, light must that light is a type of wave. travel in waves. 1704 Isaac Newton\u2019s Opticks I n the 17th century, scientists published his theory of light suggests that light is a stream began to investigate light, as a stream of \u201ccorpuscles,\u201d or of \u201ccorpuscles.\u201d and whether it had a \ufb01nite, particles. Newton\u2019s explanation measurable speed. In 1690, for refraction\u2014the bending of a AFTER Christiaan Huygens published his beam of light as it passes from one 1864 James Clerk Maxwell theory that light is a pressure wave, transparent material to another\u2014 realizes that the speed of moving in a mysterious \ufb02uid called assumed that light travels faster electromagnetic waves is so ether. Huygens thought of light as after it passes from air into water. nearly the same as the speed a longitudinal wave, and predicted of light that light must be a that the wave would travel more Estimates for the speed of light form of electromagnetic wave. slowly through glass or water than relied on astronomical phenomena, through air. In 1704, Isaac Newton showing how fast light travels 1879\u201383 German-born US through space. The \ufb01rst terrestrial physicist Albert Michelson re\ufb01nes Foucault\u2019s method and obtains a measurement for the speed of light (through air) that is very close to today\u2019s value.","A CENTURY OF PROGRESS 137 See also: Christiaan Huygens 50\u201351 \u25a0 Ole R\u00f8mer 58\u201359 \u25a0 Isaac Newton 62\u201369 \u25a0 Thomas Young 110\u201311 \u25a0 James Clerk Maxwell 180\u201385 \u25a0 Albert Einstein 214\u201321 \u25a0 Richard Feynman 272\u201373 Above all we must be Contradicting Newton argued, light could not be a accurate, and it is an In 1850, Fizeau collaborated with particle, and the experiment was obligation which we intend fellow physicist Le\u00f3n Foucault, who viewed at the time as a refutation to ful\ufb01ll scrupulously. adapted his apparatus\u2014and made of Newton\u2019s theory of corpuscles. it much smaller\u2014by re\ufb02ecting the Foucault re\ufb01ned his apparatus L\u00e9on Foucault beam of light off a rotating mirror further, and in 1862, measured the instead of passing it through the speed of light in air as 185,168 measurement was carried out by cogwheel. Light shining at the miles\/s (298,000 km\/s)\u2014remarkably French physicist Hippolyte Fizeau rotating mirror would only be close to today\u2019s value of 186,282 in 1849. A beam of light was shone re\ufb02ected toward the distant mirror miles\/s (299,792 km\/s). \u25a0 through a gap between the teeth of when the rotating mirror was at a rotating cogwheel. That light was the correct angle. Light returning Tube of water (for the then re\ufb02ected by a mirror that was from the \ufb01xed mirror was re\ufb02ected speed of light in water) positioned 5 miles (8 km) away, and by the rotating mirror again, but passed back through the next gap since this mirror had moved while Rotating between the wheel\u2019s teeth. Taking the light was traveling, it was not mirror the precise speed of rotation that re\ufb02ected directly back toward the allowed this to happen, together source. The speed of light could Fixed with time and distance, Fizeau now be calculated from the angle mirror calculated the speed of light as between the light going to and 194,489 miles\/s (313,000 km\/s). from the rotating mirror and the Light speed of rotation of the mirror. source The speed of light in water Re\ufb02ected light could be measured by putting a tube of water in the apparatus In Foucault\u2019s experiment, the between the rotating and speed of light was calculated from stationary mirrors. Using this the difference in angle as a beam of apparatus, Foucault established light re\ufb02ected back and forth between that light traveled more slowly in a rotating mirror and a \ufb01xed mirror. water than in air. As such, he L\u00e9on Foucault Born in Paris, France, L\u00e9on a pendulum in 1851 and later a Foucault was educated mainly gyroscope. Although he had no at home before entering medical formal training in science, a post school, where he studied under was created for Foucault at the the bacteriologist Alfred Donn\u00e9. Imperial Observatory in Paris. Since he could not bear the sight He was also made a member of of blood, Foucault soon gave up several scienti\ufb01c societies, and his studies, became Donn\u00e9\u2019s is one of 72 French scientists laboratory assistant, and devised named on the Eiffel Tower. a way of taking photographs through a microscope\u2014he later Key works teamed up with Hippolyte Fizeau to take the \ufb01rst ever photograph of 1851 Demonstration of Physical the Sun. In addition to measuring Movement of Rotation of the the speed of light, Foucault is best Earth by Means of the Pendulum known for providing experimental 1853 On the Relative Velocities evidence of Earth\u2019s rotation, using of the Light in Air and in Water","138 LIVING FORCE MAY BE CONVERTED INTO HEAT JAMES JOULE (1818\u20131889) IN CONTEXT T he principle of the was ever lost in this conversion. conservation of energy His ideas were largely ignored BRANCH states that energy is never until 1847, when German physicist Physics lost but only changed in form. But Hermann Helmholtz published a in the 1840s, scientists had only a paper summarizing the theory of BEFORE vague idea of what energy was. the conservation of energy, and 1749 French mathematician It was a British brewer\u2019s son, Joule then presented his work at \u00c9milie du Ch\u00e2telet derives her James Joule, who showed that the British Association in Oxford. law of the conservation of heat, mechanical movement, and The standard unit of energy, a joule, energy from Newton\u2019s laws. electricity are interchangeable is named after him. \u25a0 forms of energy, and that when 1824 French engineer Sadi one is changed to another the Carnot states that there are no total energy remains the same. reversible processes in nature, paving the way for the second Converting energy In Joule\u2019s experiment, a falling law of thermodynamics. Joule began his experiments in weight drove a paddle that turned a laboratory in the family home. inside a bucket of water. The energy of 1834 French physicist \u00c9mile In 1841, he \ufb01gured out how much the movement was changed into heat. Clapeyron develops Carnot\u2019s heat an electric current generates. work, stating a version of the He experimented with converting second law of thermodynamics. mechanical movement into heat, and developed an experiment in AFTER which a falling weight turns a 1850 German physicist Rudolf paddle wheel in water, heating Clausius gives the \ufb01rst clear the water. By measuring the rise statement of the \ufb01rst and second in temperature of the water, Joule laws of thermodynamics. was able to \ufb01gure out the exact amount of heat a certain amount of 1854 Scottish engineer mechanical work would create. He William Rankine adds the went on to assert that no energy concept that is later named entropy (a measure of disorder) See also: Isaac Newton 62\u201369 \u25a0 Joseph Black 76\u201377 \u25a0 Joseph Fourier 122\u201323 in the transformation of energy.","A CENTURY OF PROGRESS 139 STATISTICAL ANALYSIS OF MOLECULAR MOVEMENT LUDWIG BOLTZMANN (1844\u20131906) IN CONTEXT B y the middle of the In the early 18th century, Swiss 19th century, atoms and physicist Daniel Bernoulli had BRANCH molecules had become suggested that gases are made of a Physics central ideas in chemistry, and multitude of moving molecules. It is most scientists understood that their impact that creates pressure BEFORE they were the key to the identity and their kinetic energy (the energy 1738 Daniel Bernoulli and behavior of elements and of their movement) that creates suggests that gases are compounds. Few thought they heat. In the 1840s and 1850s, made of moving molecules. had much relevance to physics, scientists had begun to realize that but in the 1880s, Austrian physicist the properties of gases re\ufb02ect the 1827 Scottish botanist Ludwig Boltzmann developed the average movement of the countless Robert Brown identi\ufb01es the kinetic theory of gases, putting particles. In 1859, James Clerk movement of pollen in water, atoms and molecules right at the Maxwell calculated the speed which becomes known as heart of physics, too. of molecules and how far they Brownian motion. traveled before colliding, showing that temperature is a measure of 1845 Scottish physicist John the average speed of the molecules. Waterston describes how energy among gas molecules Available energy is the Centrality of statistics is distributed according to main object at stake in the Boltzmann revealed how important statistical rules. struggle for existence and the statistics are. He showed that the the evolution of the world. properties of matter are simply a 1857 James Clerk Maxwell combination of the basic laws of calculates the mean speed Ludwig Boltzmann motion and the statistical rules of of molecules and the mean probability. Following this principle, distance between collisions. he calculated a number now called the Boltzmann constant, providing AFTER a formula linking the pressure and 1905 Albert Einstein volume of a gas to the number and analyzes Brownian motion energy of its molecules. \u25a0 mathematically, showing how it is the result of the See also: John Dalton 112\u201313 \u25a0 James Joule 138 \u25a0 impact of molecules. James Clerk Maxwell 180\u201385 \u25a0 Albert Einstein 214\u201321","140 PLASTIC IS NOT WHAT I MEANT TO INVENT LEO BAEKELAND (1863\u20131944) IN CONTEXT T he discovery of synthetic Baekeland created one of the \ufb01rst plastics in the 19th century commercially successful plastics, BRANCH opened the way to the now known as Bakelite. Chemistry creation of a huge range of solid materials unlike anything that What gives plastic its special BEFORE had ever been known before\u2014 quality is the shape of its 1839 Berlin apothecary light, noncorroding, and capable molecules. With only a few Eduard Simon distils styrol of being molded into almost any exceptions, plastics are made resin from the Turkish sweet- imaginable shape. While plastics from long organic molecules, known gum tree. A century later, this can occur naturally, all of the as polymers, strung together is developed into polystyrene plastics now in widespread use are from many smaller molecules, or by the German IG Farben entirely synthetic. In 1907, Belgian- monomers. A few polymers occur company. born American inventor Leo naturally, such as cellulose, the main woody substance in plants. 1862 Alexander Parkes develops the \ufb01rst synthetic Materials made from long Shellac, a resin used in plastic, Parkesine. molecules called polymers varnish, is a naturally occurring polymer. 1869 American John Hyatt have special qualities. creates celluloid, which is soon used instead of ivory This arti\ufb01cial polymer It is possible to make to make billiard balls. can be used to produce arti\ufb01cial shellac by strong, hard moldable AFTER materials, called plastics. treating coal tar. 1933 British chemists Eric Fawcett and Reginald Gibson Plastic is not what I meant to invent. of the ICI company create the \ufb01rst practical polythene. 1954 Italian Giulio Natta and German Karl Rehn independently invent polypropylene, now the most widely used plastic.","A CENTURY OF PROGRESS 141 See also: Friedrich W\u00f6hler 124\u201325 \u25a0 August Kekul\u00e9 160\u201365 \u25a0 Linus Pauling 254\u201359 \u25a0 Harry Kroto 320\u201321 I was trying to make could make a kind of shellac. In Leo Baekeland something really hard, but 1907, he added various kinds of then I thought I should make powder to this resin and found Leo Baekeland was born in something really soft instead, that he could create a remarkable Ghent in Belgium and studied that could be moulded into hard, moldable plastic. at the university there. In different shapes. That was how 1889, he became associate I came up with the \ufb01rst plastic. Chemically this plastic is known professor of chemistry and as polyoxybenzylmethylenglycolan- married Celine Swarts. Leo Baekeland hydride, but Baekeland called it While the young couple simply Bakelite. Bakelite was a were on honeymoon in Although the molecules of natural \u201cthermoset\u201d plastic\u2014plastic that New York, Baekeland met polymers were far too complex holds its shape after being heated. Richard Anthony, head of a to \ufb01gure out in the 1800s, some Due to its properties of electrical well-known photographic scientists began to explore ways insulation and heat resistance, company. Anthony was so of making them synthetically Bakelite was soon being used to impressed by Baekeland\u2019s from chemical reactions. In 1862, make radios, telephones, and work with photographic British chemist Alexander Parkes electrical insulators. Many more processes that he hired him created a synthetic form of cellulose, uses were quickly found for it. as a consulting chemist. which he called Parkesine. A few Baekeland moved to the years later, American John Hyatt Today, there are thousands US and was soon in developed another, which became of synthetic plastics, including business for himself. known as celluloid. Plexiglass, polythene, low-density polyethylene, and cellophane, Baekeland invented the each with its own properties and \ufb01rst photographic papers, uses. The majority are based known as Velox, before on hydrocarbons (chemicals developing Bakelite, which made from hydrogen and carbon) made him rich. He is credited derived from oil or natural gas. with many inventions besides However, in recent decades, plastic, registering more than carbon \ufb01bers, nanotubes and 50 patents in total. In later other materials have been added life, he became an eccentric to create superlight, superstrong recluse, eating food only from plastic materials such as Kevlar. \u25a0 tin cans. He died in 1944 and is buried in Sleepy Hollow Imitating nature Heat-resistant and nonconductive Cemetery, New York. After developing the world\u2019s \ufb01rst of electricity, Bakelite was an ideal photographic paper in the 1890s, material to use for the casings of Key work Baekeland sold the idea to Kodak electrical goods such as telephones and used the money to buy a house and radios. 1909 Paper on Bakelite equipped with its own laboratory. read to the American Here, he experimented with ways Chemical Society of creating synthetic shellac. Shellac is a resin secreted by the female lac beetle. It is a natural polymer that was used to give furniture and other objects a tough, shiny coat. Baekeland found that by treating phenol resin made from coal tar with formaldehyde, he","I HAVE CALLED THIS PRINCIPLE NATURAL SELECTION CHARLES DARWIN (1809\u20131882)","","144 CHARLES DARWIN Most organisms produce more offspring than can survive due to constraints such as lack of IN CONTEXT food and living space. BRANCH Biology Offspring vary from each other in many ways. BEFORE Variation means some offspring are better 1794 Erasmus Darwin suited or adapted to the struggle for survival. (Charles\u2019s grandfather) recounts his vision of If these individuals pass on the advantageous evolution in Zoonomia. traits to their offspring, these also survive. 1809 Jean-Baptiste Lamarck I have called this principle \u201cnatural selection.\u201d proposes a form of evolution through the inheritance of acquired characteristics. AFTER 1937 Theodosius Dobzhansky publishes his experimental evidence for the genetic basis of evolution. 1942 Ernst Mayr de\ufb01nes the concept of species through populations that reproduce only with one another. 1972 Niles Eldredge and Stephen Jay Gould propose that evolution occurs mainly in short bursts interspersed with periods of relative stability. T he British naturalist Preservation of Favoured Races in biology, providing a simple, but Charles Darwin was by no the Struggle for Life, published in immensely powerful, explanation means the \ufb01rst scientist London in 1859. Darwin described of life forms both past and present. to suggest that plants, animals, and the book as \u201cone long argument.\u201d other organisms are not \ufb01xed and Darwin was acutely aware of unchanging\u2014or, to use the popular \u201cConfessing a murder\u201d the potential blasphemy in his word of the time, \u201cimmutable.\u201d Like On the Origin of Species met with work during the decades he spent others before him, Darwin proposed academic and popular opposition. writing it. Fifteen years before that species of organisms change, It made no mention of religious publication, he explained to his or evolve, through time. His great doctrine, which insisted that con\ufb01dant, the botanist Joseph contribution was to show how species were indeed \ufb01xed and Hooker, that his theory required evolution took place by a process immutable and designed by God. no God or unchanging species: he termed natural selection. He But gradually the ideas in the book \u201cAt last gleams of light have come, laid out his central idea in his changed the scienti\ufb01c perspective & I am almost convinced (quite book On the Origin of Species by on the natural world. Its core notion contrary to opinion I started with) Means of Natural Selection, or the forms the basis for all modern that species are not (it is like confessing a murder) immutable.\u201d","A CENTURY OF PROGRESS 145 See also: James Hutton 96\u2013101 \u25a0 Jean-Baptiste Lamarck 118 \u25a0 Gregor Mendel 166\u201371 \u25a0 Thomas Henry Huxley 172\u201373 \u25a0 Thomas Hunt Morgan 224\u201325 \u25a0 Barbara McClintock 271 \u25a0 James Watson and Francis Crick 276\u201383 \u25a0 Michael Syvanen 318\u201319 Creation is not an event that In 1796, the French naturalist Philosophie Zoologique of 1809 happened in 4004 BCE; it is a Georges Cuvier recognized that articulated what was perhaps the certain fossils, such as those \ufb01rst reasoned theory of evolution. process that began some of mammoths or giant sloths, were He theorized that living beings 10 billion years ago and the remains of animals that had evolved from simple beginnings become extinct. He reconciled this through increasingly sophisticated is still under way. with his religious belief by invoking stages, due to a \u201ccomplexifying Theodosius Dobzhansky catastrophes such as the Flood force.\u201d They faced environmental depicted in the Bible. Each disaster challenges on their body physiques, Darwin\u2019s approach to evolution, swept away a whole assortment of and from this came the idea of like the rest of his wide-ranging living things; God then replenished use and disuse in an individual: work in natural history, was Earth with new species. Between \u201cMore frequent and continuous use cautious, careful, and deliberate. each disaster, each species of any organ gradually strengthens, He proceeded step by step, remained \ufb01xed and immutable. develops and enlarges that organ\u2026 amassing great quantities of This theory was known as while the permanent disuse of evidence along the way. Over \u201ccatastrophism\u201d and it became any organ imperceptibly weakens almost 30 years, he integrated widely known following the and deteriorates it\u2026until it \ufb01nally his extensive knowledge of fossils, publication of Cuvier\u2019s Preliminary disappears.\u201d The organ\u2019s greater geology, plants, animals, and Discourse in 1813. power was then passed to selective breeding, with concepts offspring, a phenomenon that from demography, economics, and However, at the time Cuvier became known as inheritance many other \ufb01elds. The resulting was writing, various ideas based of acquired characteristics. theory of evolution by natural on evolution were already in selection is regarded as one of the circulation. Erasmus Darwin, Although his theory came to be greatest scienti\ufb01c advances ever. the free-thinking grandfather largely discounted, Lamarck was of Charles, proposed an early, later praised by Darwin for having The role of God idiosyncratic theory. More opened up the possibility that In the early 19th century, fossils in\ufb02uential were the ideas of change did not occur as a result of were widely discussed in Victorian Jean-Baptiste Lamarck, professor what Darwin disparagingly termed society. Some regarded them as of zoology at France\u2019s National \u201cmiraculous interposition.\u201d naturally formed rock shapes, Museum of Natural History. His and nothing to do with living Adventures of the Beagle organisms. Others saw them as Darwin had plenty of time to muse the handiwork of the Creator, put on the immutability of species on Earth to test believers. Or they during an around-the-world voyage thought that they were the remains aboard the survey ship HMS of organisms still alive somewhere Beagle, in 1831\u201336, under captain in the world, since God had created Robert FitzRoy. As expedition living things in perfection. scientist, Darwin was charged with collecting all types of fossil, plant, and animal specimens, and sending them back to Britain from each port of call. \u276f\u276f By studying the fossil record, Georges Cuvier established that species had become extinct. But he believed that the evidence pointed to a series of catastrophes, not gradual change.","146 CHARLES DARWIN This epic voyage opened the eyes modi\ufb01ed for different ends.\u201d This Natural selection is the\u2026 of the young Darwin, still only in his was one of the \ufb01rst clear, public principle by which slight twenties, to the incredible variety formulations of where his thoughts variation (of a trait), if useful, of life. Wherever the Beagle docked, on evolution were heading. Darwin keenly observed all aspects is preserved. of nature. In 1835, he described Comparing species Charles Darwin and collected a group of small, Darwin\u2019s \ufb01nches, as the Gal\u00e1pagos insigni\ufb01cant birds on the specimens became known, were tortoises, Falkland Island foxes, Gal\u00e1pagos Islands, a Paci\ufb01c Ocean not the only trigger for his work on and other species supported these archipelago 560 miles (900 km) evolution. In fact, his thoughts had early conclusions. But Darwin west of Ecuador. He thought there been mounting throughout the was sensitive about where such were nine species, six being \ufb01nches. Beagle\u2019s voyage, and especially blasphemous ideas would lead: during his visit to the Gal\u00e1pagos. \u201cSuch facts would undermine the After his return to England, He was fascinated by the giant stability of species.\u201d Darwin organized his mass of tortoises he saw, and by the way data and oversaw a multivolume, the shapes of their shells differed Other parts of the jigsaw multiauthor report, The Zoology of subtly from island to island. On his way to South America in the Voyage of HMS Beagle. In the He was also impressed by the 1831, Darwin had read the \ufb01rst volume on birds, the renowned species of mockingbirds. They, volume of Charles Lyell\u2019s Principles ornithologist John Gould declared too, varied between the islands, of Geology. Lyell argued against that there were in fact 13 species yet they also had similarities not Cuvier\u2019s catastrophism history in Darwin\u2019s specimens, all of them only among themselves, but with and his theory of fossil formation. \ufb01nches. Within the group, however, species that lived on the South Instead, he adapted the ideas of were birds with differently shaped American mainland. geological renewal put forward by beaks, adapted to different diets. James Hutton into a theory known Darwin suggested that the as \u201cuniformitarianism.\u201d Earth was In his own, bestselling account various mockingbirds might have continually being formed, altered, of his adventure, The Voyage of the evolved from a common ancestor and reformed over immense time Beagle, Darwin wrote, \u201cSeeing this that had somehow crossed the periods by processes such as wave gradation and diversity of structure Paci\ufb01c from the mainland; then erosion and volcanic upheaval that in one small, intimately related each group of birds evolved by were the same as those happening group of birds, one might really adapting to the particular today. There was no need to invoke fancy that from an original paucity environment on each island and disastrous interventions by God. of birds in this archipelago, one its available food. Observing giant species had been taken and Lyell\u2019s ideas transformed the way Darwin interpreted the landscape formations, rocks, and This giant tortoise is only found on the Gal\u00e1pagos Islands, where unique subspecies have developed on each island. Darwin gathered evidence here for his theory of evolution.","A CENTURY OF PROGRESS 147 The \ufb01nches of the Gal\u00e1pagos have evolved differently shaped beaks adapted to speci\ufb01c diets. Large ground Geospiza Geospiza fortis Medium-sized \ufb01nch has a large, magnirostris ground \ufb01nch has strong beak for a smaller beak for crushing large, crushing smaller, woody seeds. softer seeds. Small tree \ufb01nch Warbler \ufb01nch has a short, sharp has a thin beak for beak for grasping probing for small insects. insects and spearing them. Camarhynchus Certhidea parvulus olivacea fossils he found on his explorations, potential to double after one evidence to support his theory of which he now saw \u201cthrough Lyell\u2019s generation of 25 years, then double evolution. Scientists around the eyes.\u201d However, while he was in again in the next generation, and world sent him specimens and South America, volume two of so on. However, food supplies data. He studied the domestication Principles of Geology arrived. In could not expand in the same way, of animals and plants, and the it, Lyell rejected ideas of gradual and the result was a struggle for role of selective breeding, or arti\ufb01cial evolution of plants and animals, existence. Malthus\u2019s ideas were selection, especially in pigeons. In including Lamarck\u2019s theories. one of the main inspirations for 1855, he started breeding varieties Instead, he invoked the concept Darwin\u2019s theory of evolution. of Columbia livia, or rock doves, and of \u201ccentres of Creation\u201d to explain they would feature prominently in species\u2019 diversity and distribution. The quiet years the \ufb01rst two chapters in On the Although Darwin admired Lyell as Even before the Beagle had Origin of Species. a geologist, he had to discount this returned to England, the interest latest concept as the evidence for generated by the specimens Through his work on pigeons, evolution mounted. Darwin had sent back had made Darwin began to understand him a celebrity. After his return, the extent and relevance of Another piece of the jigsaw his scienti\ufb01c and popular accounts variation among individuals. was revealed in 1838 when Darwin of the voyage increased his fame. He rejected the accepted wisdom read An Essay on the Principle However, his health deteriorated that environmental factors were of Population by the English and gradually he withdrew from responsible for such differences, demographer Thomas Malthus, the public eye. insisting that reproduction was which had been published 40 years the cause, with variation somehow earlier. Malthus described how In 1842, Darwin moved to the inherited from parents. He added human populations can increase peace and quiet of Down House in this to the ideas of Malthus and in an exponential way, with the Kent, where he continued to amass applied them to the natural world. \u276f\u276f","148 CHARLES DARWIN Much later, in his autobiography, Alfred Russel Wallace, like Darwin, nonetheless present, among the Darwin recalled his reaction when developed his theory of evolution in the offspring within a species. For he \ufb01rst read Malthus back in 1838. light of extensive \ufb01eld work, conducted evolution, these variations must \u201cBeing well prepared to appreciate \ufb01rst in the Amazon River Basin and ful\ufb01ll two criteria. One: they should the struggle for existence\u2026it later in the Malay Archipelago. have some effect on the struggle at once struck me that under to survive and breed, that is, they these circumstances favourable Worried about precedence, Darwin should help to confer reproductive variations would tend to be consulted Charles Lyell. They success. Two: they should be preserved, and unfavourable ones agreed to a joint presentation of inherited, or passed to offspring, to be destroyed. The result of this Darwin\u2019s and Wallace\u2019s papers at where they would confer the same would be the formation of new the Linnaean Society in London on evolutionary advantage. species\u2026I had at last got a theory July 1, 1858. Neither author would by which to work.\u201d attend in person. The audience\u2019s Darwin describes evolution as response was polite, with no outcry a slow and gradual process. As a Knowing more about the role of about blasphemy. Encouraged, population of organisms adapts variation, by 1856 Darwin the pigeon Darwin now \ufb01nished his book. to a new environment, it becomes breeder could imagine not humans Published on November 24, 1859, a new species, different from but nature doing the choosing. From On the Origin of Species sold out the term \u201carti\ufb01cial selection\u201d he on its \ufb01rst day. derived \u201cnatural selection.\u201d Darwin\u2019s theory Jolt into action Darwin states that species are not On June 18, 1858, Darwin received immutable. They change, or evolve, a short essay by a young British and the main mechanism for this naturalist named Alfred Russel change is natural selection. The Wallace. Wallace described a process relies on two factors. \ufb02ash of insight in which he had First, more offspring are born than suddenly understood how evolution can survive when faced with the occurred, and asked Darwin for challenges of climate, food supply, his opinion. Darwin was startled competition, predators, and to read that Wallace\u2019s insight diseases; this leads to a struggle replicated almost exactly the same for existence. Second, there is ideas he himself had been working variation, sometimes tiny but on for more than 20 years. Charles Darwin Born in Shrewsbury, England, and on marine invertebrates, in 1809, Darwin was originally especially barnacles, which he destined to follow his father studied for almost 10 years. He into medicine, but his childhood also wrote works on fertilization, was \ufb01lled with pursuits such as of orchids, insect-eating plants, beetle collecting, and with little movement in plants, and inclination to become a physician, variation among domesticated he trained for the clergy. A chance animals and plants. Later in life, appointment in 1831 placed him he tackled the origin of humans. as expedition scientist on HMS Beagle\u2019s around-the-world trip. Key works Following the voyage, Darwin 1839 The Voyage of the Beagle was under the scienti\ufb01c spotlight, 1859 On the Origin of Species by gaining fame as a perceptive Means of Natural Selection observer, reliable experimenter, 1871 The Descent of Man, and and talented writer. He wrote Selection in Relation to Sex on the formation of coral reefs"]