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Leonardo da Vinci

2008-08-12T16:24:00.001-07:00

I

INTRODUCTION
Leonardo da Vinci (1452-1519), Florentine artist, one of the great masters of the High Renaissance, celebrated as a painter, sculptor, architect, engineer, and scientist. His profound love of knowledge and research was the keynote of both his artistic and scientific endeavors. His innovations in the field of painting influenced the course of Italian art for more than a century after his death, and his scientific studies—particularly in the fields of anatomy, optics, and hydraulics—anticipated many of the developments of modern science.
II

EARLY LIFE IN FLORENCE
Leonardo was born in the small town of Vinci, in Tuscany (Toscana), near Florence. He was the son of a wealthy Florentine notary and a peasant woman. In the mid-1460s the family settled in Florence, where Leonardo was given the best education that Florence, a major intellectual and artistic center of Italy, could offer. He rapidly advanced socially and intellectually. He was handsome, persuasive in conversation, and a fine musician and improviser. About 1466 he was apprenticed as a garzone (studio boy) to Andrea del Verrocchio, the leading Florentine painter and sculptor of his day. In Verrocchio's workshop Leonardo was introduced to many activities, from the painting of altarpieces and panel pictures to the creation of large sculptural projects in marble and bronze. In 1472 he was entered in the painter's guild of Florence, and in 1476 he was still considered Verrocchio's assistant. In Verrocchio's Baptism of Christ (1470?, Uffizi, Florence), the kneeling angel at the left of the painting is by Leonardo.
In 1478 Leonardo became an independent master. His first commission, to paint an altarpiece for the chapel of the Palazzo Vecchio, the Florentine town hall, was never executed. His first large painting, The Adoration of the Magi (begun 1481, Uffizi), left unfinished, was ordered in 1481 for the Monastery of San Donato a Scopeto, Florence. Other works ascribed to his youth are the so-called Benois Madonna (1478?, Hermitage, Saint Petersburg), the portrait Ginevra de' Benci (1474?, National Gallery, Washington, D.C.), and the unfinished Saint Jerome (1481?, Pinacoteca, Vatican).
III

YEARS IN MILAN
About 1482 Leonardo entered the service of the duke of Milan, Ludovico Sforza, having written the duke an astonishing letter in which he stated that he could build portable bridges; that he knew the techniques of constructing bombardments and of making cannons; that he could build ships as well as armored vehicles, catapults, and other war machines; and that he could execute sculpture in marble, bronze, and clay. He served as principal engineer in the duke's numerous military enterprises and was active also as an architect. In addition, he assisted the Italian mathematician Luca Pacioli in the celebrated work Divina Proportione (1509).
Evidence indicates that Leonardo had apprentices and pupils in Milan, for whom he probably wrote the various texts later compiled as Treatise on Painting (1651; translated 1956). The most important of his own paintings during the early Milan period was The Virgin of the Rocks, two versions of which exist (1483-1485, Louvre, Paris; 1490s to 1506-1508, National Gallery, London); he worked on the compositions for a long time, as was his custom, seemingly unwilling to finish what he had begun. From 1495 to 1497 Leonardo labored on his masterpiece, The Last Supper, a mural in the refectory of the Monastery of Santa Maria delle Grazie, Milan. Unfortunately, his experimental use of oil on dry plaster (on what was the thin outer wall of a space designed for serving food) was technically unsound, and by 1500 its deterioration had begun. Since 1726 attempts have been made to restore it. Several of these efforts involved repainting. From 1977 to 1999, a concerted restoration and conservation program made use of the latest technology to reverse some of the damage. Although much of the original surface is gone, the majesty of the composition and the penetrating characterization of the figures give a fleeting vision of its vanished splendor.
During his long stay in Milan, Leonardo also produced other paintings and drawings (most of which have been lost), theater designs, architectural drawings, and models for the dome of Milan Cathedral. His largest commission was for a colossal bronze monument to Francesco Sforza, father of Ludovico, in the courtyard of Castello Sforzesco. In December 1499, however, the Sforza family was driven from Milan by French forces; Leonardo left the statue unfinished (it was destroyed by French archers, who used the terra cotta model as a target) and he returned to Florence in 1500.
IV

RETURN TO FLORENCE
In 1502 Leonardo entered the service of Cesare Borgia, duke of Romagna and son and chief general of Pope Alexander VI. In his capacity as the duke's chief architect and engineer, Leonardo supervised work on the fortresses of the papal territories in central Italy. In 1503 he was a member of a commission of artists who were to decide on the proper location for the David (1501-1504, Accademia, Florence), the famous colossal marble statue by the Italian sculptor Michelangelo, and he also served as an engineer in the war against Pisa. Toward the end of the year Leonardo began to design a decoration for the great hall of the Palazzo Vecchio. The subject was the Battle of Anghiari, a Florentine victory in its war with Pisa. He made many drawings for the decoration and completed a full-size cartoon, or sketch, in 1505, but he never finished the wall painting. The cartoon itself was destroyed in the 17th century, and the composition survives only in copies, of which the most famous is the one by the Flemish painter Peter Paul Rubens (1615?, Louvre).
During this second Florentine period, Leonardo painted several portraits, but the only one that survives is the famous Mona Lisa (1503-1506, Louvre). One of the most celebrated portraits ever painted, it is also known as La Gioconda, after the presumed name of the woman's husband. Leonardo seems to have had a special affection for the picture, for he took it with him on all of his subsequent travels.
V

LATER TRAVELS AND DEATH
In 1506 Leonardo again went to Milan, at the summons of its French governor, Charles d'Amboise. The following year he was named court painter to King Louis XII of France, who was then residing in Milan. For the next six years Leonardo divided his time between Milan and Florence, where he often visited his half brothers and half sisters and looked after his inheritance. In Milan he continued his engineering projects and worked on an equestrian figure for a monument to Gian Giacomo Trivulzio, commander of the French forces in the city; although the project was not completed, drawings and studies have been preserved. From 1514 to 1516 Leonardo lived in Rome under the patronage of Pope Leo X. He was housed in the Palazzo Belvedere in the Vatican and seems to have been occupied principally with scientific experimentation. In 1516 he traveled to France to enter the service of King Francis I. He spent his last years at the Château de Cloux, near Amboise, where he died.
VI

PAINTINGS
Although Leonardo produced a relatively small number of paintings, many of which remained unfinished, he was nevertheless an extraordinarily innovative and influential artist. During his early years, his style closely paralleled that of Verrocchio, but he gradually moved away from his teacher's stiff, tight, and somewhat rigid treatment of figures to develop a more evocative and atmospheric handling of composition. The early painting The Adoration of the Magi introduced a new approach to composition, in which the main figures are grouped in the foreground, while the background consists of distant views of imaginary ruins and battle scenes.
Leonardo's stylistic innovations are even more apparent in The Last Supper, in which he represented a traditional theme in an entirely new way. Instead of showing the 12 apostles as individual figures, he grouped them in dynamic compositional units of three, framing the figure of Christ, who is isolated in the center of the picture. Seated before a pale distant landscape seen through a rectangular opening in the wall, Christ—who has just announced that one of those present will betray him—represents a calm nucleus while the others respond with animated gestures. In the monumentality of the scene and the weightiness of the figures, Leonardo reintroduced a style pioneered more than a generation earlier by Masaccio, the father of Florentine painting. A 22-year project to remove accumulated dust and grease as well as earlier repainting from the mural was completed in 1999.
The Mona Lisa, Leonardo's most famous work, is as well known for its mastery of technical innovations as for the mysteriousness of its legendary smiling subject. This work is a consummate example of two techniques—sfumato and chiaroscuro—of which Leonardo was one of the first great masters. Sfumato is characterized by subtle, almost infinitesimal transitions between color areas, creating a delicately atmospheric haze or smoky effect; it is especially evident in the delicate gauzy robes worn by the sitter and in her enigmatic smile. Chiaroscuro is the technique of modeling and defining forms through contrasts of light and shadow; the sensitive hands of the sitter are portrayed with a luminous modulation of light and shade, while color contrast is used only sparingly.
Leonardo was among the first to introduce atmospheric perspective into his landscape backgrounds, an especially notable characteristic of his paintings. The chief masters of the High Renaissance in Florence, including Raphael, Andrea del Sarto, and Fra Bartolommeo, all learned from Leonardo; he completely transformed the school of Milan; and at Parma, the artistic development of Correggio was given direction by Leonardo's work.
Leonardo's many extant drawings, which reveal his brilliant draftsmanship and his mastery of the anatomy of humans, animals, and plant life, may be found in the principal European collections. The largest group is at Windsor Castle in England. Probably his most famous drawing is the magnificent self-portrait in old age (1510?-1513?, Biblioteca Reale, Turin, Italy).
VII

SCULPTURAL AND ARCHITECTURAL DRAWINGS
Because none of Leonardo's sculptural projects was brought to completion, his approach to three-dimensional art can only be judged from his drawings. The same strictures apply to his architecture: None of his building projects was actually carried out as he devised them. In his architectural drawings, however, he demonstrates mastery in the use of massive forms, a clarity of expression, and especially a deep understanding of ancient Roman sources.
VIII

SCIENTIFIC AND THEORETICAL PROJECTS
As a scientist Leonardo towered above all his contemporaries. His scientific theories, like his artistic innovations, were based on careful observation and precise documentation. He understood, better than anyone of his century or the next, the importance of precise scientific observation. Unfortunately, just as he frequently failed to bring to conclusion artistic projects, he never completed his planned treatises on a variety of scientific subjects. His theories are contained in numerous notebooks, most of which were written in mirror script. Because they were not easily decipherable, Leonardo's findings were not disseminated in his own lifetime; had they been published, they would have revolutionized the science of the 16th century. Leonardo actually anticipated many discoveries of modern times. In anatomy he studied the circulation of the blood and the action of the eye. He made discoveries in meteorology and geology, learned the effect of the moon on the tides, foreshadowed modern conceptions of continent formation, and surmised the nature of fossil shells. He was among the originators of the science of hydraulics and probably devised the hydrometer; his scheme for the canalization of rivers still has practical value. He invented a large number of ingenious machines, many potentially useful, among them an underwater diving suit. His flying devices, although not practicable, embodied sound principles of aerodynamics.
See also Drawing; Painting; Renaissance Art and Architecture.

Isaac Newton

2008-08-12T16:23:00.001-07:00

Isaac Newton (1642-1727), English physicist, mathematician, and natural philosopher, considered one of the most important scientists of all time. Newton formulated laws of universal gravitation and motion—laws that explain how objects move on Earth as well as through the heavens (see Mechanics). He established the modern study of optics—or the behavior of light—and built the first reflecting telescope. His mathematical insights led him to invent the area of mathematics called calculus (which German mathematician Gottfried Wilhelm Leibniz also developed independently). Newton stated his ideas in several published works, two of which, Philosophiae Naturalis Principia Mathematica (Mathematical Principles of Natural Philosophy, 1687) and Opticks (1704), are considered among the greatest scientific works ever produced. Newton’s revolutionary contributions explained the workings of a large part of the physical world in mathematical terms, and they suggested that science may provide explanations for other phenomena as well.
Newton took known facts and formed mathematical theories to explain them. He used his mathematical theories to predict the behavior of objects in different circumstances and then compared his predictions with what he observed in experiments. Finally, Newton used his results to check—and if need be, modify—his theories (see Deduction). He was able to unite the explanation of physical properties with the means of prediction. Newton began with the laws of motion and gravitation he observed in nature, then used these laws to convert physics from a mere science of explanation into a general mathematical system with rules and laws. His experiments explained the phenomena of light and color and anticipated modern developments in light theory. In addition, his invention of calculus gave science one of its most versatile and powerful tools.
II

EARLY LIFE AND EDUCATION
Newton was born in Woolsthorpe, Lincolnshire, in England. Newton’s father died before his birth. When he was three years old, his mother remarried, and his maternal grandmother then took over his upbringing. He began his schooling in neighboring towns, and at age ten was sent to the grammar school at nearby Grantham. While at school he lived at the house of a pharmacist named Clark, from whom he may have acquired his lifelong interest in chemical operations. The young Newton seems to have been a quiet boy who was skilled with his hands. He made sundials, model windmills, a water clock, a mechanical carriage, and flew kites with lanterns attached to their tails. However, he was (as he recounted late in his life) very inattentive at school.
In 1656 Newton’s mother, on the death of her second husband, returned to Woolsthorpe and took her son out of school in the hope of making him a farmer. Newton showed no talent for farming, however, and according to legend he once was found under a hedge deep in study when he should have been in the market at Grantham. Fortunately, Newton’s former teacher at Grantham recognized the boy’s intellectual gifts and eventually persuaded Newton’s mother to allow him to prepare for entrance to University of Cambridge. In June 1661 Trinity College at Cambridge admitted Newton as a subsizar (a student required to perform various domestic services). His studies included arithmetic, geometry, trigonometry, and, later, astronomy and optics. He probably received much inspiration at Trinity from distinguished mathematician and theologian Isaac Barrow, who was a professor of mathematics at the college. Barrow recognized Newton’s genius and did all he could to cultivate it. Newton earned his bachelor’s degree in January 1665.
III

EARLY SCIENTIFIC IDEAS
When an outbreak of bubonic plague in 1665 temporarily shut down University of Cambridge, Newton returned to Woolsthorpe, where he remained for nearly two years. This period was an intellectually rich one for Newton. During this time, he did much scientific work in the subjects he would spend his life exploring: motion, optics, and mathematics.
At this point, according to his own account, Newton had made great progress in what he called his mathematical “method of fluxions” (which today we call calculus). He also recorded his first thoughts on gravitation, inspired (according to legend) by observing the fall of an apple in an orchard. According to a report of a conversation with Newton in his old age, he said he was trying to determine what type of force could hold the Moon in its path around Earth. The fall of an apple led him to think that the attractive gravitational force acting on the apple might be the same force acting on the Moon. Newton believed that this force, although weakened by distance, held the Moon in its orbit.
Newton devised a numerical equation to verify his ideas about gravity. The equation is called the inverse square law of attraction, and it states that the force of gravity (an object’s pull on another object) is related to the inverse square of the distance between the two objects (that is, the number 1 divided by the distance between the two objects times itself). Newton believed this law should apply to the Sun and the planets as well. He did not pursue the problem of the falling apple at the time, because calculating the combined attraction of the whole Earth on a small body near its surface seemed too difficult. He reintroduced these early thoughts years later in his more thorough work, the Principia.
Newton also began to investigate the nature of light. White light, according to the view of his time, was uniform, or homogeneous, in content. Newton’s first experiments with a prism called this view of white light into question. Passing a beam of sunlight through a prism, he observed that the beam spread out into a colored band of light, called a spectrum. While others had undoubtedly performed similar experiments, Newton showed that the differences in color were caused by differing degrees of a property he called refrangibility. Refrangibility is the ability of light rays to be refracted, or bent by a substance. For example, when a ray of violet light passes through a refracting medium such as glass, it bends more than does a ray of red light. Newton concluded through experimentation that sunlight is a combination of all the colors of the spectrum and that the sunlight separates when passed through the prism because its component colors are of differing refrangibility. This property that Newton discovered actually depends directly on the wavelengths of the different components of sunlight. A refracting substance, such as a prism, will bend each wavelength of light by a different amount.
A

The Reflecting Telescope
In October 1667, soon after his return to Cambridge, Newton was elected to a minor fellowship at Trinity College. Six months later he received a major fellowship and shortly thereafter was named Master of Arts. During this period he devoted much of his time to practical work in optics. His earlier experiments with the prism convinced him that a telescope’s resolution is limited not so much by the difficulty of building flawless lenses as by the general refraction differences of differently colored rays. Newton observed that lenses refract, or bend, different colors of light by a slightly different amount. He believed that these differences would make it impossible to bring a beam of white light (which includes all the different colors of light) to a single focus. Thus he turned his attention to building a reflecting telescope, or a telescope that uses mirrors instead of lenses, as a practical solution. Mirrors reflect all colors of light by the same amount.
Scottish mathematician James Gregory had proposed a design for a reflecting telescope in 1663, but Newton was the first scientist to build one. He built a reflecting telescope with a 1.3-in (3.3-cm) mirror in 1668. This telescope magnified objects about 40 times and differed slightly from Gregory’s in design. Three years later, the Royal Society, England’s official association of prominent scientists and mathematicians, invited Newton to submit his telescope for inspection. He sent one similar to his original model, and the Society established Newton’s dominance in the field by publishing a description of the instrument.
B

Calculus (Newton’s “Fluxional Method”)
In 1669 Newton gave his Trinity mathematics professor Isaac Barrow an important manuscript, which is generally known by its shortened Latin title, De Analysi. This work contained many of Newton’s conclusions about calculus (what Newton called his “fluxional method”). Although the paper was not immediately published, Barrow made its results known to several of the leading mathematicians of Britain and Europe. This paper established Newton as one of the top mathematicians of his day and as the founder of modern calculus (along with Leibniz). Calculus addresses such concepts as the rate of change of a certain quantity, the slope of a curve at a given point, the computation of maximum and minimum values of functions, and the calculation of areas bounded by curves. When Barrow retired in 1669, he suggested to the college that Newton succeed him. Newton became the new professor of mathematics and chose optics as the subject of his first course of lectures.
C

Newton’s First Published Works
In early 1672 Newton was elected a Fellow of the Royal Society. Shortly afterward Newton offered to submit a paper detailing his discovery of the composite nature of white light. Much impressed by his account, the Society published it. This publication triggered a long series of objections to Newton’s scientific views in general, mostly by European scientists from outside England. Many of the criticisms later proved unsound. The strongest criticism of Newton’s work, however, concerned his work on the theory of gravity and came from English inventor, mathematician, and curator of the Royal Society Robert Hooke. Hooke insisted that he had suggested fundamental principles of the law of gravitation to Newton. Newton answered these objections carefully and at first patiently but later with growing irritation. These public arguments aggravated Newton’s sensitivity to criticism, and for several years he stopped publishing his findings.
IV

THE PRINCIPIA MATHEMATICA AND LAWS OF MOTION
By 1679 Newton had returned to the problem of planetary orbits. The idea of a planetary attraction based on the inverse square of the distance between the Sun and the planets (which he had assumed in his early calculations at Woolsthorpe) ignited wide debate in the scientific community. This law of attraction follows, in the simple case of a circular orbit, from German astronomer Johannes Kepler’s Third Law, which relates the time of a planet’s revolution around the Sun to the size of the planet’s orbit (see Kepler’s Laws). The law of attraction also takes into account the centripetal acceleration of a body moving in a circle, given by Dutch astronomer Christiaan Huygens in 1673. The problem of determining the orbit from the law of force had baffled everyone before Newton, who solved it in about 1680. See also Mechanics: Newton’s Three Laws of Motion.
In August 1684 English astronomer Edmond Halley visited Cambridge to consult with Newton on the problem of orbits. During a discussion with Halley about the shape of an orbit under the inverse square law of attraction, Newton suggested that it would be an ellipse. Unable to find the calculation from which he had derived the answer, Newton promised to send it to Halley, which he did a few months later. On a second visit Halley received what he called “a curious treatise de motu” (de motu means “on motion”), which at Halley’s request was registered with the Royal Society in February 1685.
This tract on the laws of motion formed the basis of the first book of Philosophiae Naturalis Principia Mathematica. Scientists and scholars consider this work a milestone of scientific inquiry, and its composition in the span of about 18 months was an intellectual feat unsurpassed at that time. Halley played a substantial role in the development of the Principia. He tactfully smoothed over differences between Newton and Hooke, who insisted that Newton had stolen some of his ideas. Newton angrily decided to suppress the third section of this work, but Halley persuaded Newton to publish it. Halley managed Newton’s work through publication and underwrote the cost of printing.
The Principia finally appeared in the summer of 1687. The scientific community hailed it as a masterpiece, although Newton had intentionally made the book difficult “to avoid being baited by little smatterers in mathematics.” The book’s grand unifying idea of gravitation, with effects extending throughout the solar system, captured the imagination of the scientific community. The work used one principle to explain diverse phenomena such as the tides, the irregularities of the Moon’s motion, and the slight yearly variations in the onset of spring and autumn.
V

NEWTON’S LATER WORK
A few months before publication of the Principia, Newton emerged as a defender of academic freedom. King James II, who hoped to reestablish Roman Catholicism in England, issued a mandate to Cambridge in February 1687. This mandate called on the university to admit a certain Benedictine monk, Alban Francis, to the degree of Master of Arts without requiring him to take the usual oaths of allegiance to the Crown. The university saw this mandate as a request to grant preferential treatment to a Catholic and as a threat both to tradition and standards, so it steadfastly refused. Newton took a prominent part in defending the university’s position. The university senate appointed a group (including Newton) to appear before a government commission at Westminster, and they successfully defended the university’s rights. After the downfall of James II in the Glorious Revolution of 1688, Newton was elected a representative of the university in the Convention Parliament, in which he sat from January 1689 until its dissolution a year later. While he does not appear to have taken part in debate, Newton continued to be zealous in upholding the privileges of the university.
Newton’s public duties brought a change to his retiring mode of life and required frequent journeys to London, where he met several prominent writers and intellectuals, most notably philosopher John Locke and diarist and civil servant Samuel Pepys. In the early 1690s, possibly in response to the intellectual exertion of writing the Principia, Newton suffered a period of depression. Opinions differ among Newton’s biographers as to the permanence of the effects of the attack.
In the years after his illness, Newton summoned the energy to attack the complex problem of the Moon’s motion. This work involved a correspondence with John Flamsteed, England’s first Astronomer Royal, whose lunar observations Newton needed. However, misunderstandings and quarrels marred their relationship, which ended sourly. In 1698 Newton tried to carry his lunar work further and resumed collaboration with Flamsteed, but difficulties arose again and Newton accused Flamsteed of withholding his observations. The two scientists had not resolved the dispute when Flamsteed died in 1719.
In 1696 Newton’s friends in the government secured a paying political post for him by appointing him warden of the mint. This position required that he live in London, where he resided until his death. Newton’s work at the mint included a complete reform of the coinage. In order to combat counterfeiting, he introduced the minting of coins of standard weight and composition. He also instituted the policy of minting coins with milled edges. Newton successfully carried out these tasks, which demanded great technical and administrative skill, in the three years leading up to November 1699. At that time his peers promoted him to the mastership of the mint. This position was a well-paid post that Newton held for the rest of his life.
In 1701 Newton resigned his chair and fellowship at Cambridge and in 1703 was elected president of the Royal Society, an office to which he was reelected annually thereafter. In 1704, a year after the death of his rival Hooke, he brought out his second great treatise, Opticks, which included his theories of light and color as well as his mathematical discoveries. Unlike the Principia, which was in Latin, Opticks was written in English, but Newton later published a Latin translation. Most of Newton’s work on Opticks was done long before he relocated to London. One of its most interesting features is a series of general speculations added to the second edition (1717) in the form of “Queries,” or questions, which bear witness to his profound insight into physics. Many of his questions foreshadowed modern developments in physics, engineering, and the natural sciences.
In 1705 Queen Anne knighted Newton. By this time Newton was the dominant figure in British and European science. In the last two decades of his life, he prepared the second and third editions of the Principia (1713, 1726) and published second and third editions of Opticks (1717, 1721) as well.
During these last two decades Newton was entangled in a lengthy and bitter controversy with Leibniz over which of the two scientists had invented calculus. This controversy embittered Newton’s last years and harmed relations between the scientific communities in Britain and on the European continent. It also slowed the progress of mathematical science in Britain. Most scholars agree that Newton was the first to invent calculus, although Leibniz was the first to publish his findings. Mathematicians later adopted Leibniz’s mathematical symbols, which have survived to the present day with few changes.
VI

NEWTON’S IMPACT ON SCIENCE
Newton’s place in scientific history rests on his application of mathematics to the study of nature and his explanation of a wide range of natural phenomena with one general principle—the law of gravitation. He used the foundations of dynamics, or the laws of nature governing motion and its effects on bodies, as the basis of a mechanical picture of the universe. His achievements in the use of calculus went so far beyond previous discoveries that scientists and scholars regard him as the chief pioneer in this field of mathematics.
Newton’s work greatly influenced the development of physical sciences. During the two centuries following publication of the Principia, scientists and philosophers found many new areas in which they applied Newton’s methods of inquiry and analysis. Much of this expansion arose as a consequence of the Principia. Scientists did not see the need for revision of some of Newton’s conclusions until the early 20th century. This reassessment of Newton’s ideas about the universe led to the modern theory of relativity and to quantum theory, which deal with the special cases of physics involving high speeds and physics of very small dimensions, respectively. For systems of ordinary dimensions, involving velocities that do not approach the speed of light, the principles that Newton formulated nearly three centuries ago are still valid.Besides his scientific work, Newton left substantial writings on theology, chronology, alchemy, and chemistry. In 1725 Newton moved from London to Kensington (then a village outside London) for health reasons. He died there on March 20, 1727. He was buried in Westminster Abbey, the first scientist to be so honored.

Albert Einstein

2008-08-12T16:22:00.000-07:00

I

INTRODUCTION
Albert Einstein (1879-1955), German-born American physicist and Nobel laureate, best known as the creator of the special and general theories of relativity and for his bold hypothesis concerning the particle nature of light. He is perhaps the most well-known scientist of the 20th century.
Einstein was born in Ulm on March 14, 1879, and spent his youth in Munich, where his family owned a small shop that manufactured electric machinery. He did not talk until the age of three, but even as a youth he showed a brilliant curiosity about nature and an ability to understand difficult mathematical concepts. At the age of 12 he taught himself Euclidean geometry.
Einstein hated the dull regimentation and unimaginative spirit of school in Munich. When repeated business failure led the family to leave Germany for Milan, Italy, Einstein, who was then 15 years old, used the opportunity to withdraw from the school. He spent a year with his parents in Milan, and when it became clear that he would have to make his own way in the world, he finished secondary school in Aarau, Switzerland, and entered the Swiss Federal Institute of Technology in Zürich. Einstein did not enjoy the methods of instruction there. He often cut classes and used the time to study physics on his own or to play his beloved violin. He passed his examinations and graduated in 1900 by studying the notes of a classmate. His professors did not think highly of him and would not recommend him for a university position.
For two years Einstein worked as a tutor and substitute teacher. In 1902 he secured a position as an examiner in the Swiss patent office in Bern. In 1903 he married Mileva Marić, who had been his classmate at the polytechnic. They had one daughter, who was born prior to their marriage and given up for adoption, and two sons. The couple eventually divorced, and Einstein later remarried.
II

EARLY SCIENTIFIC PUBLICATIONS
In 1905 Einstein received his doctorate from the University of Zürich for a theoretical dissertation on the dimensions of molecules, and he also published three theoretical papers of central importance to the development of 20th-century physics. In the first of these papers, on Brownian motion, he made significant predictions about the motion of particles that are randomly distributed in a fluid. These predictions were later confirmed by experiment.
The second paper, on the photoelectric effect, contained a revolutionary hypothesis concerning the nature of light. Einstein not only proposed that under certain circumstances light can be considered as consisting of particles, but he also hypothesized that the energy carried by any light particle, called a photon, is proportional to the frequency of the radiation. The formula for this is E = hν, where E is the energy of the radiation, h is a universal constant known as Planck’s constant, and ν is the frequency of the radiation. This proposal—that the energy contained within a light beam is transferred in individual units, or quanta—contradicted a hundred-year-old tradition of considering light energy a manifestation of continuous processes. Virtually no one accepted Einstein’s proposal. In fact, when the American physicist Robert Andrews Millikan experimentally confirmed the theory almost a decade later, he was surprised and somewhat disquieted by the outcome.
Einstein, whose prime concern was to understand the nature of electromagnetic radiation, subsequently urged the development of a theory that would be a fusion of the wave and particle models for light. Again, very few physicists understood or were sympathetic to these ideas.
III

EINSTEIN’S SPECIAL THEORY OF RELATIVITY
Einstein’s third major paper in 1905, “On the Electrodynamics of Moving Bodies,” contained what became known as the special theory of relativity. Since the time of the English mathematician and physicist Sir Isaac Newton, natural philosophers (as physicists and chemists were known) had been trying to understand the nature of matter and radiation, and how they interacted in some unified world picture. The position that mechanical laws are fundamental has become known as the mechanical world view, and the position that electrical laws are fundamental has become known as the electromagnetic world view. Neither approach, however, is capable of providing a consistent explanation for the way radiation (light, for example) and matter interact when viewed from different inertial frames of reference, that is, an interaction viewed simultaneously by an observer at rest and an observer moving at uniform speed.
In the spring of 1905, after considering these problems for ten years, Einstein realized that the crux of the problem lay not in a theory of matter but in a theory of measurement. At the heart of his special theory of relativity was the realization that all measurements of time and space depend on judgments as to whether two distant events occur simultaneously. This led him to develop a theory based on two postulates: the principle of relativity, that physical laws are the same in all inertial reference systems, and the principle of the invariance of the speed of light, that the speed of light in a vacuum is a universal constant. He was thus able to provide a consistent and correct description of physical events in different inertial frames of reference without making special assumptions about the nature of matter or radiation, or how they interact. Virtually no one understood Einstein’s argument.
IV

EARLY REACTIONS TO EINSTEIN
The difficulty that others had with Einstein’s work was not because it was too mathematically complex or technically obscure; the problem resulted, rather, from Einstein’s beliefs about the nature of good theories and the relationship between experiment and theory. Although he maintained that the only source of knowledge is experience, he also believed that scientific theories are the free creations of a finely tuned physical intuition and that the premises on which theories are based cannot be connected logically to experiment. A good theory, therefore, is one in which a minimum number of postulates is required to account for the physical evidence. This sparseness of postulates, a feature of all Einstein’s work, was what made his work so difficult for colleagues to comprehend, let alone support.
Einstein did have important supporters, however. His chief early patron was the German physicist Max Planck. Einstein remained at the patent office for four years after his star began to rise within the physics community. He then moved rapidly upward in the German-speaking academic world; his first academic appointment was in 1909 at the University of Zürich. In 1911 he moved to the German-speaking university at Prague, and in 1912 he returned to the Swiss National Polytechnic in Zürich. Finally, in 1914, he was appointed director of the Kaiser Wilhelm Institute for Physics in Berlin.
V

THE GENERAL THEORY OF RELATIVITY
Even before he left the patent office in 1907, Einstein began work on extending and generalizing the theory of relativity to all coordinate systems. He began by enunciating the principle of equivalence, a postulate that gravitational fields are equivalent to accelerations of the frame of reference. For example, people in a moving elevator cannot, in principle, decide whether the force that acts on them is caused by gravitation or by a constant acceleration of the elevator. The full general theory of relativity was not published until 1916. In this theory the interactions of bodies, which heretofore had been ascribed to gravitational forces, are explained as the influence of bodies on the geometry of space-time (four-dimensional space, a mathematical abstraction, having the three dimensions from Euclidean space and time as the fourth dimension).
On the basis of the general theory of relativity, Einstein accounted for the previously unexplained variations in the orbital motion of the planets and predicted the bending of starlight in the vicinity of a massive body such as the sun. The confirmation of this latter phenomenon during an eclipse of the sun in 1919 became a media event, and Einstein’s fame spread worldwide.
For the rest of his life Einstein devoted considerable time to generalizing his theory even more. His last effort, the unified field theory, which was not entirely successful, was an attempt to understand all physical interactions—including electromagnetic interactions and weak and strong interactions—in terms of the modification of the geometry of space-time between interacting entities.
Most of Einstein’s colleagues felt that these efforts were misguided. Between 1915 and 1930 the mainstream of physics was in developing a new conception of the fundamental character of matter, known as quantum theory. This theory contained the feature of wave-particle duality (light exhibits the properties of a particle, as well as of a wave) that Einstein had earlier urged as necessary, as well as the uncertainty principle, which states that precision in measuring processes is limited. Additionally, it contained a novel rejection, at a fundamental level, of the notion of strict causality. Einstein, however, would not accept such notions and remained a critic of these developments until the end of his life. “God,” Einstein once said, “does not play dice with the world.”
VI

WORLD CITIZEN
After 1919, Einstein became internationally renowned. He accrued honors and awards, including the Nobel Prize in physics in 1921, from various world scientific societies. His visit to any part of the world became a national event; photographers and reporters followed him everywhere. While regretting his loss of privacy, Einstein capitalized on his fame to further his own political and social views.
The two social movements that received his full support were pacifism and Zionism. During World War I he was one of a handful of German academics willing to publicly decry Germany’s involvement in the war. After the war his continued public support of pacifist and Zionist goals made him the target of vicious attacks by anti-Semitic and right-wing elements in Germany. Even his scientific theories were publicly ridiculed, especially the theory of relativity.
When Hitler came to power, Einstein immediately decided to leave Germany for the United States. He took a position at the Institute for Advanced Study at Princeton, New Jersey. While continuing his efforts on behalf of world Zionism, Einstein renounced his former pacifist stand in the face of the awesome threat to humankind posed by the Nazi regime in Germany.
In 1939 Einstein collaborated with several other physicists in writing a letter to President Franklin D. Roosevelt, pointing out the possibility of making an atomic bomb and the likelihood that the German government was embarking on such a course. The letter, which bore only Einstein’s signature, helped lend urgency to efforts in the U.S. to build the atomic bomb, but Einstein himself played no role in the work and knew nothing about it at the time.
After the war, Einstein was active in the cause of international disarmament and world government. He continued his active support of Zionism but declined the offer made by leaders of the state of Israel to become president of that country. In the U.S. during the late 1940s and early ‘50s he spoke out on the need for the nation’s intellectuals to make any sacrifice necessary to preserve political freedom. Einstein died in Princeton on April 18, 1955.
Einstein’s efforts in behalf of social causes have sometimes been viewed as unrealistic. In fact, his proposals were always carefully thought out. Like his scientific theories, they were motivated by sound intuition based on a shrewd and careful assessment of evidence and observation. Although Einstein gave much of himself to political and social causes, science always came first, because, he often said, only the discovery of the nature of the universe would have lasting meaning. His writings include Relativity: The Special and General Theory (1916); About Zionism (1931); Builders of the Universe (1932); Why War? (1933), with Sigmund Freud; The World as I See It (1934); The Evolution of Physics (1938), with the Polish physicist Leopold Infeld; and Out of My Later Years (1950). Einstein’s collected papers are being published in a multivolume work, beginning in 1987.

Marie Curie

2008-08-12T16:21:00.000-07:00

Marie Curie
I

INTRODUCTION
Marie Curie (1867-1934), Polish-born French chemist and physicist who twice won the Nobel Prize and is best known for her investigations of radioactivity with her husband Pierre Curie. Radioactivity is the spontaneous decay of certain elements into other elements and energy. The Curies shared the 1903 Nobel Prize in physics with a colleague, and Marie Curie was awarded the 1911 Nobel Prize in chemistry.
II

EARLY YEARS
Curie was born Maria Skłodowska on November 7, 1867, in Warsaw, Poland, and her nickname while growing up was Manya. Poland at the time was under Russian domination after an unsuccessful revolt in 1863. Her parents were teachers and ardent Polish nationalists, but soon after Manya (their fifth child) was born, they lost their teaching posts and had to take in boarders. Their young daughter worked long hours helping with the meals, but she nevertheless won a medal for excellence at the local high school, where the examinations and some classes were held in Russian.
No higher education was available to women in Poland at that time, so Manya took a job as a governess. Part of her earnings helped pay for her older sister’s medical studies in Paris, France. Her sister qualified as a doctor and married a fellow doctor in 1891. Manya went to join them in Paris that year, changing her name to Marie. She entered the Sorbonne (now the Universities of Paris) and studied physics and mathematics, graduating at the top of her class. In 1894 she met French physicist Pierre Curie, and they were married the following year.
III

RESEARCH ON RADIOACTIVITY
From 1896 the Curies worked together on radioactivity, building on the results of German physicist Wilhelm Roentgen, who had discovered X-rays, and French physicist Antoine Henri Becquerel. Becquerel had discovered that uranium salts emit similar, unusual radiation, and Marie Curie turned to investigating whether any other elements emitted these rays. She discovered that the metallic element thorium also emits radiation and found that the mineral pitchblende emitted much stronger radiation than its uranium and thorium content could account for. She coined the term radioactive for the substances that gave off these rays.
The Curies then carried out an exhaustive search for the substance that could be producing the radioactivity. They processed an enormous amount of pitchblende, and performed repeated operations to separate it into its chemical components. Finally, they obtained a few hundredths of a gram containing the source of the radiation. In July 1898 they announced the discovery of a new chemical element, which they named polonium after Marie Curie’s homeland. The discovery of the element radium followed in December 1898. They eventually prepared 1 g (0.04 oz) of pure radium chloride from 8 metric tons of waste pitchblende from Austria. They also established that beta rays (now known to consist of electrons) are negatively charged particles.
In 1903 the Curies and Becquerel were awarded the Nobel Prize in physics for their fundamental research on radioactivity. Marie Curie went on to study the chemistry and medical applications of radium, and in 1911 she was awarded the Nobel Prize in chemistry in recognition of her work in discovering radium and polonium and in isolating radium.
In 1906 Marie took over Pierre Curie’s post at the Sorbonne after he was run over and killed by a horse-drawn carriage. She became the first woman to teach there, and she concentrated all her energies into research and caring for her daughters. The Curies’ older daughter, Irene, later married Frédéric Joliot and became a famous scientist and Nobel laureate herself (see Irene Joliot-Curie; Frédéric Joliot-Curie). In 1910 Marie worked with French chemist André Debierne to isolate pure radium metal. In 1914 the University of Paris built the Institut du Radium (now the Institut Curie) to provide laboratory space for research on radioactive materials.
IV

LATER YEARS: RADIATION IN MEDICINE
During World War I (1914-1918) Marie Curie played an active role in the use of radiation for medical purposes. She helped equip ambulances with X-ray equipment, which she drove to the front lines. The International Red Cross made her head of its Radiological Service. She and her colleagues at the Institut du Radium held courses for medical orderlies and doctors, teaching them how to use the new technique.
By the late 1920s Curie’s health began to deteriorate. Because the dangers of radioactivity were unknown, she had been exposed during her career to massive doses of high-energy radiation (see Radiation Effects, Biological). As a result of this exposure she had to have several cataract operations, and she died of leukemia on July 4, 1934, at a sanatorium at Haute-Savoie in the French Alps. A few months earlier her daughter and son-in-law, the Joliot-Curies, had announced the discovery of artificial radioactivity.
Throughout much of her life Marie Curie was poor, and she and her fellow scientists carried out much of their work extracting radium under primitive conditions. The Curies refused to patent any of their discoveries, wanting them to benefit everyone freely. The Nobel Prize money and other financial rewards were used to finance further research.
Curie became one of the most famous women of her time. She had mixed feelings about her fame because it interfered with her scientific work. However, she was able to use her fame to promote the medical uses of radium by facilitating the foundation of radium therapy institutes in France, Poland, the United States, and elsewhere. One of the outstanding applications of her work has been the use of radiation to treat cancer (see Radiology: Therapeutic Radiology), one form of which cost Curie her life.

Francis Crick

2008-08-12T16:20:00.000-07:00

Francis Crick

INTRODUCTION
Francis Crick (1916-2004), British biophysicist and cowinner of the 1962 Nobel Prize in physiology or medicine. Crick shared the prize with American biologist James D. Watson and British biophysicist Maurice Wilkins for their discoveries about the structure of deoxyribonucleic acid (DNA), the molecule that transmits genetic information from generation to generation.
II

EARLY EDUCATION AND RESEARCH
Francis Harry Compton Crick was born in Northampton, England. His father owned a footwear factory and encouraged Crick’s early interest in scientific experiments. Crick attended the local grammar school and won a scholarship to Mill Hill School in North London at the age of 14. At University College, London, he studied physics. After graduation in 1937, Crick briefly pursued his doctoral degree studying the properties of water under high temperatures and pressures. His studies were interrupted by World War II (1939-1945), during which Crick worked for the scientific service of the British Admiralty, helping to design magnetic and acoustic mines.
After World War II, Crick decided his interests lay in biology. There were two general areas he wished to pursue: what he later described as “the borderline between the living and nonliving” and neurobiology. He decided to initially concentrate on the first goal, studying the chemical components that form the basis of living things. Thus, in 1947 he returned to school to study biology at the Strangeways Research Laboratory at Cambridge University.
III

IDENTIFYING THE STRUCTURE OF DNA
In 1949 Crick moved to the Cavendish Laboratory at Cambridge University to pursue his doctoral degree. Working under British physicist and Nobel laureate Sir William Lawrence Bragg, Crick studied the structure of proteins using X-ray diffraction. X-ray diffraction provides X-ray patterns of a molecule’s chemical structure. He eventually moved to a unit of the Medical Research Council (MRC), a publicly funded laboratory located at Cambridge University. At MRC, Crick found himself in talented company. He worked under the guidance of Austrian-born British biochemist Max Perutz and alongside British chemist John Kendrew, two future Nobel laureates. Crick initially studied the structure of hemoglobin, a red, iron-rich protein that carries oxygen in the blood. It was not long, however, before Crick became more interested in studying the structure of DNA.
In 1951 Watson joined Crick’s laboratory at MRC. Crick and Watson shared the same passionate desire to determine the structure of DNA and, over the next two years, they worked together on the problem. American biochemist Linus Pauling had earlier shown success in building scale models to identify the structure of proteins. Crick and Watson decided to use that approach to study DNA. At the time, Wilkins and British chemist Rosalind Franklin at King’s College, London, were using X-ray diffraction analysis to study the DNA molecule. Crick and Watson applied the diffraction studies created by Wilkins and Franklin to their own research.
After a few missteps, Crick and Watson used the X-ray diffraction patterns created by Franklin to develop a three-dimensional model for the structure of DNA. This model depicted DNA as two complementary strands twisted into a double helix.
In 1953 Crick and Watson published their findings in the science journal Nature. Because of their work, scientists were able to understand and describe living things for the first time in terms of the structure and interaction of molecules. Recognized as one of the most significant discoveries of the 20th century, the identification of the structure of DNA affects practically every scientific discipline in the life sciences.
IV

OTHER CONTRIBUTIONS TO GENETICS
Crick received his Ph.D. from Cambridge University in 1953. He then worked briefly with Watson on the structure of viruses. But he eventually returned to the study of DNA and his findings led to rapid advances in genetics. He and his coworkers determined how the order of bases, chemical subunits on the DNA structure, act as a code to determine the sequence of amino acids that make up proteins. With South African-born British geneticist Sydney Brenner, Crick identified that codons, groups of three bases, provide instructions for the creation of all 20 amino acids.
Crick made two sweeping theories that have stood the test of time. In his adaptor hypothesis, he theorized that small molecules of ribonucleic acid (RNA) and enzymes work as intermediaries between DNA and amino acids during protein synthesis. Initially met with skepticism in the science community, the theory was eventually proven correct with the discovery of transfer RNA and adaptor enzymes. Crick also theorized that the flow of genetic information is from DNA to RNA to protein, and that genetic information cannot flow the other way, from protein to RNA to DNA. This theory has been tested repeatedly since Crick discussed it at a meeting of the Society of Experimental Biology in 1957, and it is now called the central dogma, a crucial principle of molecular biology.
V

LATER RESEARCH
In 1977 Crick moved to the Salk Institute of Biological Studies at La Jolla, California, where he pursued his early interest in neurobiology, studying how the brain functions. He also worked on questions related to the origins of life on Earth. Never afraid to announce a controversial theory, in 1981 Crick wrote Life Itself, in which he argued that life on Earth could have originated in microorganisms that arrived from elsewhere in the universe.
Other books by Crick include Molecules and Men (1966) and The Astonishing Hypothesis (1994). He also authored more than 130 scientific papers.
In addition to the Nobel Prize, Crick was awarded the Albert Lasker Award for Basic Medical Research, the Award of Merit from the Gairdner Foundation, and the Prix Charles Leopold Meyer of the French Academy of Sciences. Crick was a member of the U.S. National Academy of Sciences, the Royal Society, the French Academy of Sciences, and the Irish Academy.

Nicolaus Copernicus

2008-08-12T16:18:00.000-07:00

Nicolaus Copernicus
I

INTRODUCTION
Nicolaus Copernicus (1473-1543), Polish astronomer, best known for his astronomical theory that the sun is at rest near the center of the universe, and that the earth, spinning on its axis once daily, revolves annually around the sun. This is called the heliocentric, or sun-centered, system. See Astronomy; History of Astronomy; Solar System.
II

EARLY LIFE AND EDUCATION
Copernicus was born on February 19, 1473, in Thorn (now Toruń), Poland, to a family of merchants and municipal officials. Copernicus's maternal uncle, Bishop Łukasz Watzenrode, saw to it that his nephew obtained a solid education at the best universities. Copernicus entered Kraków Academy (now Jagiellonian University) in 1491, studied the liberal arts for four years without receiving a degree, and then, like many Poles of his social class, went to Italy to study medicine and law. Before he left, his uncle had him appointed a church administrator in Frauenberg (now Frombork); this was a post with financial responsibilities but no priestly duties. In January 1497 Copernicus began to study canon law at the University of Bologna while living in the home of a mathematics professor, Domenico Maria de Novara. Copernicus's geographical and astronomical interests were greatly stimulated by Domenico Maria, an early critic of the accuracy of the Geography of the 2nd-century astronomer Ptolemy. Together, the two men observed the occultation (the eclipse by the moon) of the star Aldebaran on March 9, 1497.
In 1500 Copernicus lectured on astronomy in Rome. The following year he gained permission to study medicine at Padua, the university where Galileo taught nearly a century later. It was not unusual at the time to study a subject at one university and then to receive a degree from another—often less expensive—institution. And so Copernicus, without completing his medical studies, received a doctorate in canon law from Ferrara in 1503 and then returned to Poland to take up his administrative duties.
III

RETURN TO POLAND
From 1503 to 1510, Copernicus lived in his uncle's bishopric palace in Lidzbark Warminski, assisting in the administration of the diocese and in the conflict against the Teutonic Knights. There he published his first book, a Latin translation of letters on morals by a 7th-century Byzantine writer, Theophylactus of Simocatta. Sometime between 1507 and 1515, he completed a short astronomical treatise, De Hypothesibus Motuum Coelestium a se Constitutis Commentariolus (known as the Commentariolus), which was not published until the 19th century. In this work he laid down the principles of his new heliocentric astronomy.
After moving to Frauenberg in 1512, Copernicus took part in the Fifth Lateran Council's commission on calendar reform in 1515; wrote a treatise on money in 1517; and began his major work, De Revolutionibus Orbium Coelestium (On the Revolutions of the Celestial Spheres), which was finished by 1530 but was first published by a Lutheran printer in Nürnberg, Germany, just before Copernicus's death in 1543.
IV

EARLY 16TH-CENTURY COSMOLOGY
The cosmology that was eventually replaced by Copernican theory postulated a geocentric universe in which the earth was stationary and motionless at the center of several concentric, rotating spheres. These spheres bore (in order from the earth outward) the following celestial bodies: the moon, Mercury, Venus, the sun, Mars, Jupiter, and Saturn. The finite outermost sphere bore the so-called fixed stars. (This last sphere was said to wobble slowly, thereby producing the precession of the equinoxes; see Ecliptic.)
One phenomenon had posed a particular problem for cosmologists and natural philosophers since ancient times: the apparent retrograde (backward) motion of Mars, Jupiter, and Saturn. From time to time the daily motion of these planets through the sky appears to halt and then to proceed in the opposite direction. In an attempt to account for this retrograde motion, medieval cosmology stated that each planet revolved on the edge of a circle called the epicycle, and the center of each epicycle revolved around the earth on a path called the deferent (see Ptolemaic System).
V

THE COPERNICAN SYSTEM AND ITS INFLUENCE
The major premises of Copernicus's theory are that the earth rotates daily on its axis and revolves yearly around the sun. He argued, furthermore, that the planets also circle the sun, and that the earth precesses on its axis (wobbles like a top) as it rotates. The Copernican theory retained many features of the cosmology it replaced, including the solid, planet-bearing spheres, and the finite outermost sphere bearing the fixed stars. On the other hand, Copernicus's heliocentric theories of planetary motion had the advantage of accounting for the apparent daily and yearly motion of the sun and stars, and it neatly explained the apparent retrograde motion of Mars, Jupiter, and Saturn and the fact that Mercury and Venus never move more than a certain distance from the sun. Copernicus's theory also stated that the sphere of the fixed stars was stationary.
Another important feature of Copernican theory is that it allowed a new ordering of the planets according to their periods of revolution. In Copernicus's universe, unlike Ptolemy's, the greater the radius of a planet's orbit, the greater the time the planet takes to make one circuit around the sun. But the price of accepting the concept of a moving earth was too high for most 16th-century readers who understood Copernicus's claims. In addition, Copernicus's calculations of astronomical positions were neither decisively simpler nor more accurate than those of his predecessors, even though his heliocentric theory made good physical sense, for the first time, of planetary movements. As a result, parts of his theory were adopted, while the radical core was ignored or rejected.
There were but ten Copernicans between 1543 and 1600. Most worked outside the universities in princely, royal, or imperial courts; the most famous were Galileo and the German astronomer Johannes Kepler. These men often differed in their reasons for supporting the Copernican system. In 1588 an important middle position was developed by the Danish astronomer Tycho Brahe in which the earth remained at rest and all the planets revolved around the sun as it revolved around the earth.
After the suppression of Copernican theory occasioned by the ecclesiastical trial of Galileo in 1633, some Jesuit philosophers remained secret followers of Copernicus. Many others adopted the geocentric-heliocentric system of Brahe. By the late 17th century and the rise of the system of celestial mechanics propounded by the English natural philosopher Sir Isaac Newton, most major thinkers in England, France, the Netherlands, and Denmark were Copernicans. Natural philosophers in the other European countries, however, held strong anti-Copernican views for at least another century.

George Washington Carver

2008-08-12T15:38:00.000-07:00

George Washington Carver

INTRODUCTION
George Washington Carver (1861?-1943), American scientist and educator, noted especially for his research on the peanut. Carver was internationally recognized for his research in agricultural sciences, and he is credited with having revolutionized agriculture in the Southern United States. As a teacher and as the head of agricultural research at Tuskegee Normal and Industrial Institute (now known as Tuskegee University) in Alabama, Carver dedicated his career to finding uses for plant products and to teaching farmers the advantages of diversifying their crops.
II

EDUCATION
Carver was born a slave near Diamond, Missouri, during the American Civil War (1861-1865). Around age ten he left the farm where he was born and traveled through the Midwest doing odd jobs to support his education. Carver studied constantly and attended schools wherever possible, finally graduating from high school in Minneapolis, Kansas, in 1885. That same year he passed the entrance examination at Highland College in northeastern Kansas. But when school officials learned he was black, he was prevented from attending.
In 1891 Carver was admitted to the Iowa State College of Agricultural and Mechanical Arts (now Iowa State University) in Ames. He received his Bachelor of Science degree in 1894, becoming the first black to graduate from the college. After graduation, Carver was appointed to the faculty as an assistant botanist. While teaching, he pursued his master’s degree, studying fungus diseases and classification of plants. In 1896 he received his master’s degree. That year, at the invitation of American educator Booker T. Washington, Carver became the director of agricultural research at Tuskegee Institute, where he remained for the rest of his life.
III

CAREER AT TUSKEGEE INSTITUTE
During his tenure at Tuskegee Institute, Carver developed over 300 uses for peanuts, sweet potatoes, soybeans, and the byproducts of these crops. From peanuts he synthesized axle grease, soap, ink, flour, plastics, a coffee substitute, and more than 200 other useful products. From sweet potatoes he derived 118 products, including molasses, vinegar, and rubber, and from soybeans he extracted an oil with many uses. Partly as a result of Carver's research, peanut cultivation in the Southern states quadrupled from 1899 to 1943. By planting peanuts and sweet potatoes in addition to cotton, farmers were able to enrich their soil and were no longer economically dependent upon the success or failure of only one kind of crop.
Uninterested in business, Carver preferred that others commercialize the results of his experiments. Of his many inventions, Carver patented only three. Carver’s primary goal was to help impoverished blacks. In 1940 he donated his savings to the establishment of the George Washington Carver Foundation at Tuskegee Institute to provide scholarships in the natural sciences.
IV

AWARDS
Carver was the recipient of many prestigious awards for his achievements. He was elected a Fellow of the Royal Society of Arts of Great Britain in 1916. The National Association for the Advancement of Colored People (NAACP) awarded Carver the Spingarn Medal in 1923. In 1943 Congress established the George Washington Carver National Monument near Diamond, Missouri, on the farm where Carver was born.

Robert Boyle

2008-08-12T15:34:00.001-07:00

Robert Boyle
I

INTRODUCTION
Robert Boyle (1627-1691), English natural philosopher and one of the founders of modern chemistry. Boyle is best remembered for Boyle’s law, a physical law that explains how the pressure and volume of a gas are related. He was instrumental in the founding of the Royal Society, a British organization dedicated to the advancement of the sciences. Boyle was also a pioneer in the use of experiments and the scientific method to test his theories.
II

BOYLE’S LIFE
Boyle was born in Lismore Castle in Lismore, Ireland. His father was Richard Boyle, who was the first earl of Cork. Robert learned to speak French and Latin as a child and went to Eton College in England at the early age of eight.
In 1641 Boyle began a tour of Europe, returning to England in 1644. He settled there, because Ireland was in turmoil over colonization efforts by English protestants. Boyle had inherited parts of several estates upon his father’s death in 1643, and income from these allowed him to live independently. He joined a group known as the Invisible College, whose aim was to cultivate ideas called the “new philosophy.” The new philosophy included new methods of experimental science, in which scientists sought to prove or disprove hypotheses through careful experiments. Boyle moved to Oxford, which was one of the meeting places of the Invisible College, in 1654. King Charles II granted a charter in 1663 that allowed the Invisible College to become the Royal Society of London for Improving Natural Knowledge, and Boyle was a member of its first council. (He was elected president of the Royal Society in 1680, but declined the office.) He moved to London in 1668 and lived with his sister until his death in 1691.
III

BOYLE’S WORK
Boyle carried out his most active research while he lived in Oxford. Much of his research dealt with the behavior of gases, including the earth’s atmosphere. By careful experiments, he established Boyle’s law. Boyle’s law states that the volume of a given amount of gas varies inversely with its pressure, if temperature is constant. This means that at a constant temperature, the pressure of a gas will increase as the volume of the gas is decreased, and vice versa. Boyle determined the density of air in the earth’s atmosphere and pointed out that the weight of objects varies with changes in atmospheric pressure. He compared the lower layers of the earth’s atmosphere to a number of sponges or small springs that the weight of the layers above compresses. In 1660 Boyle published these findings in a book entitled The Spring of Air.
A year later Boyle published The Sceptical Chymist, in which he criticized previous researchers for believing that salt, sulfur, and mercury were the “true principles of things.” He advanced the view that the basic elements of matter are “corpuscles,” or particles, of various sorts and sizes. Boyle believed that these corpuscles were capable of arranging themselves into groups, and that each group constituted a chemical substance. He successfully distinguished between mixtures (substances mixed together) and compounds (chemically bonded substances) and showed that a compound can have very different qualities from those of its constituents.
Boyle studied the chemistry of combustion around 1660 with the assistance of his pupil Robert Hooke. They pumped the air out of a jar and showed that neither charcoal nor sulfur burns in a vacuum, although both substances burn in the presence of air. Boyle then found that a mixture of either substance with saltpeter (potassium nitrate) catches fire even when in a vacuum and concluded that combustion must depend on something common to both air and saltpeter. The component of air and saltpeter that allows combustion was not isolated until British chemist Joseph Priestley did so in 1774. This substance was not given its present name until French chemist Antoine Lavoisier named it oxygen three years later.
Boyle also coined the term analysis and used many of the reactions that modern qualitative chemists use today. He introduced certain plant extracts, notably litmus, which indicates whether a substance is an acid or a base (see Acids and Bases). In 1667 he was the first to study the phenomenon of bioluminescence, the emission of light from living organisms. He showed that fungi and bacteria require air (oxygen) for luminescence, becoming dark in a vacuum and glowing again when air is readmitted. Boyle drew a comparison between a glowing coal and phosphorescent wood, although oxygen was still not known and combustion was not properly understood. Boyle also seems to have been the first to construct a small, portable, box-type camera obscura in about 1665. A camera obscura is a system used to project an image onto a surface. Boyle’s camera obscura could be extended or shortened like a telescope to focus an image on a piece of paper stretched across the back of the box opposite the lens.
In 1665 Boyle published the first account in England of the use of a hydrometer for measuring the density of liquids. The instrument he described is essentially the same as those in use today. Hydrometers consist of a sealed capsule of lead or mercury inside a glass tube into which the liquid being measured is placed. The height at which the capsule floats represents the density of the liquid. Boyle is also credited with the invention of the match. In 1680 he found that he could produce fire by drawing a sulfur-tipped splint through a fold in a piece of paper that was coated with phosphorus. Boyle experimented in animal physiology, although he disliked performing actual dissections. He also carried out experiments in the hope of changing one metal into another.
Boyle was interested in theology as well as science. He spent large sums on biblical translations and learned Hebrew, Greek, and Syriac in order to further his studies of the Scriptures. He founded the Boyle Lectures for defending Christianity against other religions.Boyle accomplished much important work in physics. He studied the behavior of gases, the role of air in allowing sound to travel, and the outward force of water in the process of freezing. He was also interested in the ability of crystals to bend light, the density of liquids, electricity, color, and the behavior of liquids at rest, among other physical topics. Boyle’s greatest fondness was researching in chemistry. He was the main agent in changing the unscientific field of alchemy, which was mostly concerned with turning common metals into precious metals, into modern scientific chemistry. He was the first person to work toward removing the mystique around chemistry and to change it into a pure science. He questioned the basis of the chemical theory of his day and taught that chemistry’s purpose was to determine the compositions of substances. After his death, his natural history collections passed as a bequest to the Royal Society.

Alexander Graham Bell

2008-08-12T15:29:00.000-07:00

Alexander Graham Bell
Alexander Graham Bell (1847-1922), American inventor and teacher of the deaf, most famous for his work on the telephone.
Bell was born on March 3, 1847, in Edinburgh, Scotland, and educated at the universities of Edinburgh and London. He immigrated to Canada in 1870 and to the United States in 1871. In the United States he began teaching deaf-mutes, publicizing the system called visible speech. The system, which was developed by his father, the Scottish educator Alexander Melville Bell, shows how the lips, tongue, and throat are used in the articulation of sound. In 1872 Bell founded a school to train teachers of the deaf in Boston, Massachusetts. The school subsequently became part of Boston University, where Bell was appointed professor of vocal physiology. He became a naturalized U.S. citizen in 1882.
Since the age of 18, Bell had been working on the idea of transmitting speech. In 1874, while working on a multiple telegraph, he developed the basic ideas of the telephone. His experiments with his assistant Thomas Watson finally proved successful on March 10, 1876, when he transmitted: “Watson, come here; I want you.” Subsequent demonstrations, particularly one at the 1876 Centennial Exposition in Philadelphia, Pennsylvania, introduced the telephone to the world and led to the organization of the Bell Telephone Company in 1877.
In 1880 France bestowed on Bell the Volta Prize, worth 50,000 francs, for his invention. With this money he founded the Volta Laboratory in Washington, D.C., where, in that same year, he and his associates invented the photophone, which transmits speech by light rays. Other inventions include the audiometer, used to measure acuity in hearing; the induction balance, used to locate metal objects in human bodies; and the first wax recording cylinder, introduced in 1886. The cylinder, together with the flat wax disc, formed the basis of the modern phonograph.
Bell was one of the cofounders of the National Geographic Society, and he served as its president from 1896 to 1904. He also helped to establish the journal Science by financing it from 1883-1894.
After 1895 Bell's interest turned mostly to aeronautics. Many of his inventions in this area were first tested near his summer home at Baddeck on Cape Breton Island in Nova Scotia, Canada. His study of flight began with the construction of large kites, and in 1907 he devised a kite capable of carrying a person. With a group of associates, including the American inventor and aviator Glenn Hammond Curtiss, Bell developed the aileron, a movable section of an airplane wing that controls roll. They also developed the tricycle landing gear, which first permitted takeoff and landing on a flying field. Applying the principles of aeronautics to marine propulsion, his group started work on hydrofoil boats, which travel above the water at high speeds. His final full-sized “hydrodrome,” developed in 1917, reached speeds in excess of 113 km/h (70 mph) and for many years was the fastest boat in the world.
Bell's continuing studies on the causes and heredity of deafness led to experiments in eugenics, including sheep breeding, and to his book Duration of Life and Conditions Associated with Longevity (1918). He died on August 2, 1922, at Baddeck, where a museum containing many of his original inventions is maintained by the Canadian government.