Physics is a branch of science in which the primary objects of study are matter and energy. These topics were discussed across many cultures in ancient times by philosophers, but they had no means to distinguish causes of natural phenomena from superstitions. The Scientific Revolution of the 17th century, especially the discovery of the law of gravity, began a process of knowledge accumulation and specialization that gave rise to the field of physics. Mathematical advances of the 18th century gave rise to classical mechanics, and the increased used of the experimental method led to new understanding of thermodynamics. In the 19th century, the basic laws of electromagnetism and statistical mechanics were discovered. At the beginning of the 20th century, physics was transformed by the discoveries of quantum mechanics, relativity, and atomic theory. Physics today may be divided loosely into classical physics and modern physics.
Ancient history
Elements of what became physics were drawn primarily from the fields of astronomy, optics, and mechanics, which were methodologically united through the study of geometry. These mathematical disciplines began in antiquity with the Babylonians and with Hellenistic writers such as Archimedes and Ptolemy. Ancient philosophy, meanwhile, included what was called "Physics".
Ancient astronomy
Astronomy is one of the oldest natural sciences. Early civilizations dating before 3000 BCE, such as the Sumerians, ancient Egyptians, and the Indus Valley Civilization, had a predictive knowledge and a basic awareness of the motions of the Sun, Moon, and stars. The stars and planets, believed to represent gods, were often worshipped. While the explanations for the observed positions of the stars were often unscientific and lacking in evidence, these early observations laid the foundation for later astronomy, as the stars were found to traverse great circles across the sky,which could not explain the positions of the planets. According to Asger Aaboe, the origins of Western astronomy can be found in Mesopotamia, and all Western efforts in the exact sciences are descended from late Babylonian astronomy.Egyptian astronomers left monuments showing knowledge of the constellations and the motions of the celestial bodies, while Greek poet Homer wrote of various celestial objects in his Iliad and Odyssey; later Greek astronomers provided names, which are still used today, for most constellations visible from the Northern Hemisphere.
Greek concept The move towards a rational understanding of nature began at least since the Archaic period in Greece (650–480 BCE) with the Pre-Socratic philosophers. The philosopher Thales of Miletus (7th and 6th centuries BCE), dubbed "the Father of Science" for refusing to accept various supernatural, religious or mythological explanations for natural phenomena, proclaimed that every event had a natural cause. Thales also made advancements in 580 BCE by suggesting that water is the basic element, experimenting with the attraction between magnets and rubbed amber and formulating the first recorded cosmologies. Anaximander, developer of a proto-evolutionary theory, disputed Thales' ideas and proposed that rather than water, a substance called apeiron was the building block of all matter. Around 500 BCE, Heraclitus proposed that the only basic law governing the Universe was the principle of change and that nothing remains in the same state indefinitely. He, along with his contemporary Parmenides were among the first scholars to contemplate on the role of time in the universe, a key concept that is still an issue in modern physics.
During the classical period in Greece (6th, 5th and 4th centuries BCE) and in Hellenistic times, natural philosophy developed into a field of study. The earliest concepts of atomism were first formulated during this era by the philosophers Leucippus and his student Democritus. They introduced early atomism, proposing that the universe was composed of empty space and indivisible, indestructible particles called atomos. Aristotle (Greek: Ἀριστοτέλης, Aristotélēs) (384–322 BCE), a student of Plato, promoted the concept that observation of physical phenomena could ultimately lead to the discovery of the natural laws governing them. Aristotle's writings cover physics, metaphysics, poetry, theater, music, logic, rhetoric, linguistics, politics, government, ethics, biology and zoology. He wrote the first work which refers to that line of study as "Physics" – in the 4th century BCE, Aristotle founded the system known as Aristotelian physics. He attempted to explain ideas such as motion (and gravity) with the theory of four elements. Aristotle believed that all matter was made of aether, or some combination of four elements: earth, water, air, and fire. According to Aristotle, these four terrestrial elements are capable of inter-transformation and move toward their natural place, so a stone falls downward toward the center of the cosmos, but flames rise upward toward the circumference. Eventually, Aristotelian physics became popular for many centuries in Europe, informing the scientific and scholastic developments of the Middle Ages. It remained the mainstream scientific paradigm in Europe until the time of Galileo Galilei and Isaac Newton. Early in Classical Greece, knowledge that the Earth is spherical ("round") was common. Around 240 BCE, as the result of a seminal experiment, Eratosthenes (276–194 BCE) accurately estimated its circumference. In contrast to Aristotle's geocentric views, Aristarchus of Samos (Greek: Ἀρίσταρχος; c. 310 – c. 230 BCE) presented an explicit argument for a heliocentric model of the Solar System, i.e. for placing the Sun, not the Earth, at its centre. Seleucus of Seleucia, a follower of Aristarchus' heliocentric theory, stated that the Earth rotated around its own axis, which, in turn, revolved around the Sun. Though the arguments he used were lost, Plutarch stated that Seleucus was the first to prove the heliocentric system through reasoning.
In the 3rd century BCE, the Greek mathematician Archimedes of Syracuse Greek: Ἀρχιμήδης (287–212 BCE) – generally considered to be the greatest mathematician of antiquity and one of the greatest of all time – laid the foundations of hydrostatics, statics and calculated the underlying mathematics of the lever. A scientist of classical antiquity, Archimedes also developed elaborate systems of pulleys to move large objects with a minimum of effort. The Archimedes' screw underpins modern hydroengineering, and his machines of war helped to hold back the armies of Rome in the First Punic War. Archimedes even tore apart the arguments of Aristotle and his metaphysics, pointing out that it was impossible to separate mathematics and nature and proved it by converting mathematical theories into practical inventions. Furthermore, in his work On Floating Bodies, around 250 BCE, Archimedes developed the law of buoyancy, also known as Archimedes' principle. In mathematics, Archimedes used the method of exhaustion to calculate the area under the arc of a parabola with the summation of an infinite series, and gave a remarkably accurate approximation of pi. He also defined the spiral bearing his name, formulae for the volumes of surfaces of revolution and an ingenious system for expressing very large numbers. He also developed the principles of equilibrium states and centers of gravity, ideas that would influence future scholars like Galileo, and Newton. Hipparchus (190–120 BCE), focusing on astronomy and mathematics, used sophisticated geometrical techniques to map the motion of the stars and planets, even predicting the times that Solar eclipses would happen. He added calculations of the distance of the Sun and Moon from the Earth, based upon his improvements to the observational instruments used at that time. Another of the early physicists was Ptolemy (90–168 CE) during the time of the Roman Empire. Ptolemy was the author of several scientific treatises, at least three of which were of continuing importance to later Islamic and European science. The first is the astronomical treatise now known as the Almagest (in Greek, Ἡ Μεγάλη Σύνταξις, "The Great Treatise", originally Μαθηματικὴ Σύνταξις, "Mathematical Treatise"). The second is the Geography, which is a thorough discussion of the geographic knowledge of the Greco-Roman world. Much of the accumulated knowledge of the ancient world was lost. Even of the works of the many respectable thinkers, few fragments survive. Although he wrote at least fourteen books, almost nothing of Hipparchus' direct work survived. Of the 150 reputed Aristotelian works, only 30 exist, and some of those are "little more than lecture notes".
India and China
Important physical and mathematical traditions also existed in ancient Indian and Chinese sciences.
In Indian philosophy,Kanada (6th-2nd century BCE) was the first to systematically develop a theory of atomism. It was further elaborated by the Buddhist atomists Dharmakirti and Dignāga during the 1st millennium CE. The Vaisheshika school of philosophers believed the atom is an indestructible and indivisible particle of matter because it is a state at which no measurement can be attributed. Indian theories about the atom are greatly abstract and enmeshed in philosophy, as they were based on logic and not on personal experience or experimentation. With the arrival of Hellenistic astronomy in India through trade and cultural contacts, Indian astronomy entered a new phase during the early centuries CE. Earlier indigenous traditions, such as those recorded in the Vedāṅga Jyotiṣa, provided calendrical foundations, while Greek astronomical models were later integrated by scholars including Āryabhaṭa, Varāhamihira, and Brahmagupta. Āryabhaṭa notably improved methods for calculating planetary motions and eclipses. In the later medieval period, the Kerala school of astronomy and mathematics made significant contributions to astronomy through refined observational techniques and more accurate calculations of planetary motions and eclipses. Among its prominent scholars was Nilakantha Somayaji (1444–1544), who proposed a semi-heliocentric model of the Solar System that bears similarities to the Tychonic system. One of the earliest known written descriptions of the pinhole image appears in the Mozi dating to the 4th century BC. The work is traditionally attributed to Mozi (c. 470–391 BC) where he describes how light passing through a small aperture produces an inverted image, an early observation of the camera obscura principle. The study of magnetism in Ancient China dates to the 4th century BCE (in the Book of the Devil Valley Master). A main contributor to this field was Shen Kuo (1031–1095), a polymath and statesman who was the first to describe the magnetic-needle compass used for navigation, as well as establishing the concept of true north. In optics, Shen Kuo independently developed a camera obscura.
Islamic world
In the 7th to 15th centuries, scientific progress occurred in the Muslim world. Many classic works in Indian, Assyrian, Sassanian (Persian) and Greek, including the works of Aristotle, were translated into Arabic. Important contributions were made by Ibn al-Haytham (965–1040), an Arab or Persian scientist, considered to be a founder of modern optics. Ptolemy and Aristotle theorised that light either shone from the eye to illuminate objects or that "forms" emanated from objects themselves, whereas al-Haytham (known by the Latin name "Alhazen") suggested that light travels to the eye in rays from different points on an object. The works of Ibn al-Haytham and al-Biruni (973–1050), a Persian scientist, eventually passed on to Western Europe where they were studied by scholars such as Roger Bacon and Vitello. Ibn al-Haytham used controlled experiments in his work on optics, although to what extent it differed from Ptolemy is debated. Arabic mechanics like Bīrūnī and Al-Khazini developed sophisticated "science of weight", carrying out measurements of specific weights and volumes. Ibn Sīnā (980–1037), known as "Avicenna", was a polymath from Bukhara (in present-day Uzbekistan) responsible for important contributions to physics, optics, philosophy and medicine. He published his theory of motion in Book of Healing (1020), where he argued that an impetus is imparted to a projectile by the thrower. He viewed it as persistent, requiring external forces such as air resistance to dissipate it. Ibn Sina made a distinction between 'force' and 'inclination' (called "mayl"), and argued that an object gained mayl when the object is in opposition to its natural motion. He concluded that continuation of motion is attributed to the inclination that is transferred to the object, and that object will be in motion until the mayl is spent. This idea which dissented from the Aristotelian view was later described as "impetus" by John Buridan, who was likely influenced by Ibn Sina's Book of Healing.
Hibat Allah Abu'l-Barakat al-Baghdaadi (c. 1080 – c. 1165) adopted and modified Ibn Sina's theory on projectile motion. In his Kitab al-Mu'tabar, Abu'l-Barakat stated that the mover imparts a violent inclination (mayl qasri) on the moved and that this diminishes as the moving object distances itself from the mover. He also proposed an explanation of the acceleration of falling bodies by the accumulation of successive increments of power with successive increments of velocity. According to Shlomo Pines, al-Baghdaadi's theory of motion was "the oldest negation of Aristotle's fundamental dynamic law [namely, that a constant force produces a uniform motion], [and is thus an] anticipation in a vague fashion of the fundamental law of classical mechanics [namely, that a force applied continuously produces acceleration]." Jean Buridan and Albert of Saxony later referred to Abu'l-Barakat in explaining that the acceleration of a falling body is a result of its increasing impetus. Ibn Bajjah (c. 1085–1138), known as "Avempace" in Europe, proposed that for every force there is always a reaction force. Ibn Bajjah was a critic of Ptolemy and he worked on creating a new theory of velocity to replace the one theorized by Aristotle. Two future philosophers supported the theories Avempace created, known as Avempacean dynamics. These philosophers were Thomas Aquinas, a Catholic priest, and John Duns Scotus. Galileo went on to adopt Avempace's formula "that the velocity of a given object is the difference of the motive power of that object and the resistance of the medium of motion". Nasir al-Din al-Tusi (1201–1274), a Persian astronomer and mathematician who died in Baghdad, introduced the Tusi couple an important mathematical theorem and founded the Maragha School of astronomy. Geocentric (but not heliocentric) astronomical models developed by the Maragha School have many striking parallels with models developed by Nicolaus Copernicus. The possibility that Maragha results may have influenced Copernicus has a been investigated in some detail.
Medieval Europe
Awareness of ancient works re-entered the West through translations from Arabic to Latin. Their re-introduction, combined with Judeo-Islamic theological commentaries, had a great influence on Medieval philosophers such as Thomas Aquinas. Scholastic European scholars, who sought to reconcile the philosophy of the ancient classical philosophers with Christian theology, proclaimed Aristotle the greatest thinker of the ancient world. In cases where they did not directly contradict the Bible, Aristotelian physics became the foundation for the physical explanations of the European Churches. Quantification became a core element of medieval physics. Based on Aristotelian physics, Scholastic physics described things as moving according to their essential nature. Celestial objects were described as moving in circles, because perfect circular motion was considered an innate property of objects that existed in the uncorrupted realm of the celestial spheres. Motions below the lunar sphere were seen as imperfect, and thus could not be expected to exhibit consistent motion. More idealized motion in the "sublunary" realm could only be achieved through artifice, and prior to the 17th century, many did not view artificial experiments as a valid means of learning about the natural world. Physical explanations in the sublunary realm revolved around tendencies. Stones contained the element earth, and earthly objects tended to move in a straight line toward the centre of the earth (and the universe in the Aristotelian geocentric view) unless otherwise prevented from doing so. Aristotle's physics was not scrutinized until John Philoponus, who relied on observation rather than verbal argument like Aristotle. Philoponus' criticism of Aristotelian principles of physics served as an inspiration for Galileo Galilei ten centuries later, during the Scientific Revolution. Galileo cited Philoponus substantially in his works when arguing that Aristotelian physics was flawed. In the 1300s Jean Buridan, a teacher in the faculty of arts at the University of Paris, developed the concept of impetus. It was a step toward the modern ideas of inertia and momentum. Thomas Bradwardine and his partners, the Oxford Calculators of Merton College, Oxford, distinguished kinematics from dynamics, emphasizing kinematics, and investigating instantaneous velocity. They formulated the mean speed theorem: a body moving with constant velocity travels distance and time equal to an accelerated body whose velocity is half the final speed of the accelerated body. They also demonstrated this theorem—the essence of "The Law of Falling Bodies"—long before Galileo, who has gotten the credit for this.
Renaissance
Leonardo da Vinci
Leonardo da Vinci (1452–1519) made drawings recording the acceleration of falling objects. He wrote that the "mother and origin of gravity" is energy. He describes two pairs of physical powers which stem from a metaphysical origin and have an effect on everything: abundance of force and motion, and gravity and resistance. He associates gravity with the 'cold' classical elements, water and earth, and calls its energy infinite. In Codex Arundel, Leonardo recorded that if a water-pouring vase moves transversally (sideways), simulating the trajectory of a vertically falling object, it produces a right triangle with equal leg length, composed of falling material that forms the hypotenuse and the vase trajectory forming one of the legs. On the hypotenuse, Leonardo noted the equivalence of the two orthogonal motions, one effected by gravity and the other proposed by the experimenter.
Scientific Revolution During the 16th and 17th centuries, a large advancement of scientific progress known as the Scientific Revolution took place in Europe. Dissatisfaction with older philosophical approaches had begun earlier and had produced other changes in society, such as the Protestant Reformation, but the revolution in science began when natural philosophers began to mount a sustained attack on the Scholastic philosophical programme and supposed that mathematical descriptive schemes adopted from such fields as mechanics and astronomy could actually yield universally valid characterizations of motion and other concepts.
Nicolaus Copernicus
A breakthrough in astronomy was made by Renaissance astronomer Nicolaus Copernicus (1473–1543) when, in 1543, he gave strong arguments for the heliocentric model of the Solar System, ostensibly as a means to render tables charting planetary motion more accurate and to simplify their production. In heliocentric models of the Solar system, the Earth orbits the Sun along with other bodies in Earth's galaxy, a contradiction according to the Greek-Egyptian astronomer Ptolemy (2nd century CE; see above), whose system placed the Earth at the center of the Universe and had been accepted for over 1,400 years. The Greek astronomer Aristarchus of Samos (c. 310 – c. 230 BCE) had suggested that the Earth revolves around the Sun, but Copernicus's reasoning led to lasting general acceptance of this "revolutionary" idea. Copernicus's book presenting the theory (De revolutionibus orbium coelestium, "On the Revolutions of the Celestial Spheres") was published just before his death in 1543 and, as it is now generally considered to mark the beginning of modern astronomy, is also considered to mark the beginning of the Scientific Revolution. Copernicus's new perspective, along with the accurate observations made by Tycho Brahe, enabled German astronomer Johannes Kepler (1571–1630) to formulate his laws regarding planetary motion that remain in use today.
Galileo Galilei
The Italian mathematician, astronomer, and physicist Galileo Galilei (1564–1642) was a supporter of Copernicanism who made numerous astronomical discoveries, carried out empirical experiments and improved the telescope. As a mathematician, Galileo's role in the university culture of his era was subordinated to the three major topics of study: law, medicine, and theology (which was closely allied to philosophy). Galileo, however, felt that the descriptive content of the technical disciplines warranted philosophical interest, particularly because mathematical analysis of astronomical observations – notably, Copernicus's analysis of the relative motions of the Sun, Earth, Moon, and planets – indicated that philosophers' statements about the nature of the universe could be shown to be in error. Galileo also performed mechanical experiments, insisting that motion itself – regardless of whether it was produced "naturally" or "artificially" (i.e. deliberately) – had universally consistent characteristics that could be described mathematically. Galileo's early studies at the University of Pisa were in medicine, but he was soon drawn to mathematics and physics. At age 19, he discovered (and, subsequently, verified) the isochronal nature of the pendulum when, using his pulse, he timed the oscillations of a swinging lamp in Pisa's cathedral and found that it remained the same for each swing regardless of the swing's amplitude. He soon became known through his invention of a hydrostatic balance and for his treatise on the center of gravity of solid bodies. While teaching at the University of Pisa (1589–1592), he initiated his experiments concerning the laws of bodies in motion that brought results so contradictory to the accepted teachings of Aristotle that strong antagonism was aroused. He found that bodies do not fall with velocities proportional to their weights. The story in which Galileo is said to have dropped weights from the Leaning Tower of Pisa is apocryphal, but he did find that the path of a projectile is a parabola and is credited with conclusions that anticipated Newton's laws of motion (e.g. the notion of inertia). Among these is what is now called Galilean relativity, the first precisely formulated statement about properties of space and time outside three-dimensional geometry.
Galileo has been called the "father of modern observational astronomy", the "father of modern physics", the "father of science", and "the father of modern science". According to Stephen Hawking, "Galileo, perhaps more than any other single person, was responsible for the birth of modern science." As religious orthodoxy decreed a geocentric or Tychonic understanding of the Solar system, Galileo's support for heliocentrism provoked controversy and he was tried by the Inquisition. Found "vehemently suspect of heresy", he was forced to recant and spent the rest of his life under house arrest. The contributions that Galileo made to observational astronomy include the telescopic confirmation of the phases of Venus; his discovery, in 1609, of Jupiter's four largest moons (subsequently given the collective name of the "Galilean moons"); and the observation and analysis of sunspots. Galileo also pursued applied science and technology, inventing, among other instruments, a military compass. His discovery of the Jovian moons was published in 1610, enabling him to obtain the position of mathematician and philosopher to the Medici court. As such, he was expected to engage in debates with philosophers in the Aristotelian tradition and received a large audience for his own publications such as the Discourses and Mathematical Demonstrations Concerning Two New Sciences (published abroad following his arrest for the publication of Dialogue Concerning the Two Chief World Systems) and The Assayer. Galileo's interest in experimenting with and formulating mathematical descriptions of motion established experimentation as an integral part of natural philosophy. This tradition, combining with the non-mathematical emphasis on the collection of "experimental histories" by philosophical reformists such as William Gilbert and Francis Bacon, drew a significant following in the years leading to and following Galileo's death, including Evangelista Torricelli and the participants in the Accademia del Cimento in Italy; Marin Mersenne and Blaise Pascal in France; Christiaan Huygens in the Netherlands; and Robert Hooke and Robert Boyle in England.
Evangelista Torricelli
The Italian mathematician and physicist Evangelista Torricelli made major contributions to mechanics and fluid physics in the mid-17th century. Building on Galileo's work, he explained the limited height of suction pumps by proposing that the Earth's atmosphere exerts pressure, introducing the concept of atmospheric pressure. In 1643, he demonstrated this principle by inventing the mercury barometer, creating the first sustained laboratory vacuum . His work established the foundations of barometry, atmospheric pressure measurement, and pressure-based altitude measurement. Torricelli also formulated Torricelli's law, describing the speed of fluid flowing from an orifice, a result later recognized as a special case of Bernoulli's principle. In mechanics, he stated Torricelli's principle of equilibrium, relating the motion of connected bodies to the position of their common center of gravity.
Johannes Kepler
Johannes Kepler (1571–1630) was a German astronomer, mathematician, astrologer, natural philosopher and a key figure in the 17th century Scientific Revolution, best known for his laws of planetary motion, and his books Astronomia nova, Harmonice Mundi, and Epitome Astronomiae Copernicanae, influencing among others Isaac Newton, providing one of the foundations for his theory of universal gravitation. The variety and impact of his work made Kepler one of the founders of modern astronomy, the scientific method, natural and modern science. Kepler was partly driven by his belief that there is an intelligible plan that is accessible through reason. Kepler described his new astronomy as "celestial physics", as "an excursion into Aristotle's Metaphysics", and as "a supplement to Aristotle's On the Heavens", treating astronomy as part of a universal mathematical physics.
René Descartes
The French philosopher René Descartes (1596–1650) was well-connected to, and influential within, experimental philosophy networks. Descartes had an agenda, however, which was geared toward replacing the Scholastic philosophical tradition. Questioning the reality interpreted through the senses, Descartes sought to re-establish philosophical explanations by reducing all phenomena to the motion of an invisible sea of "corpuscles". (Notably, he reserved human thought and God from his scheme, holding these to be separate from the physical universe). In proposing this philosophical framework, Descartes supposed that different kinds of motion, such as that of planets versus that of terrestrial objects, were not fundamentally different, but were manifestations of an endless chain of corpuscular motions obeying universal principles. Particularly influential were his explanations for circular astronomical motions in terms of the vortex motion of corpuscles in space (Descartes argued, in accord with the beliefs, if not the methods, of the Scholastics, that a vacuum could not exist), and his explanation of gravity in terms of corpuscles pushing objects downward. Descartes, like Galileo, was convinced of the importance of mathematical explanation, and he and his followers were key figures in the development of mathematics and geometry in the 17th century. Cartesian mathematical descriptions of motion held that all mathematical formulations had to be justifiable in terms of direct physical action, a position held by Christiaan Huygens and the German philosopher Gottfried Leibniz, who, while following in the Cartesian tradition, developed his own philosophical alternative to Scholasticism, which he outlined in his 1714 work, the Monadology. Descartes has been dubbed the "Father of Modern Philosophy", and much subsequent Western philosophy is a response to his writings, which are studied closely to this day. In particular, his Meditations on First Philosophy continues to be a standard text at most university philosophy departments. Descartes' influence in mathematics is equally apparent; the Cartesian coordinate system – allowing algebraic equations to be expressed as geometric shapes in a two-dimensional coordinate system – was named after him. He is credited as the father of analytical geometry, the bridge between algebra and geometry, important to the discovery of calculus and analysis.
Christiaan Huygens
The Dutch physicist, mathematician, astronomer and inventor Christiaan Huygens (1629–1695) was the leading scientist in Europe between Galileo and Newton. Huygens came from a family of nobility that had an important position in the Dutch society of the 17th century; a time in which the Dutch Republic flourished economically and culturally. This period – roughly between 1588 and 1702 – of the history of the Netherlands is also referred to as the Dutch Golden Age, an era during the Scientific Revolution when Dutch science was among the most acclaimed in Europe. At this time, intellectuals and scientists like René Descartes, Baruch Spinoza, Pierre Bayle, Antonie van Leeuwenhoek, John Locke and Hugo Grotius resided in the Netherlands. It was in this intellectual environment that Christiaan Huygens grew up. Christiaan's father, Constantijn Huygens, was, apart from an important poet, the secretary and diplomat for the Princes of Orange. He knew many scientists of his time because of his contacts and intellectual interests, including René Descartes and Marin Mersenne, and it was because of these contacts that Christiaan Huygens became aware of their work, especially Descartes, whose mechanistic philosophy was going to have a huge influence on Huygens' own work. Descartes was later impressed by the skills Huygens showed in geometry, as was Mersenne, who christened him "the new Archimedes" (which led Constantijn to refer to his son as "my little Archimedes"). A child prodigy, Huygens began his correspondence with Marin Mersenne when he was 17 years old. Huygens became interested in games of chance when he encountered the work of Fermat, Blaise Pascal and Girard Desargues. It was Pascal who encouraged him to write Van Rekeningh in Spelen van Gluck, which Frans van Schooten translated and published as De Ratiociniis in Ludo Aleae in 1657. The book is the earliest known scientific treatment of the subject, and at the time the most coherent presentation of a mathematical approach to games of chance. Two years later Huygens derived geometrically the now standard formulae in classical mechanics for the centripetal- and centrifugal force in his work De vi Centrifuga (1659). Around the same time Huygens' research in horology resulted in the invention of the pendulum clock; a breakthrough in timekeeping and the most accurate timekeeper for almost 300 years. The theoretical research of the way the pendulum works eventually led to the publication of one of his most important achievements: the Horologium Oscillatorium. This work was published in 1673 and became one of the three most important 17th century works on mechanics (the other two being Galileo's Discourses and Mathematical Demonstrations Relating to Two New Sciences (1638) and Newton's Philosophiæ Naturalis Principia Mathematica (1687)). The Horologium Oscillatorium is the first modern treatise in which a physical problem (the accelerated motion of a falling body) is idealized by a set of parameters then analyzed mathematically and constitutes one of the seminal works of applied mathematics. It is for this reason, Huygens has been called the first theoretical physicist and one of the founders of modern mathematical physics. Huygens' Horologium Oscillatorium influenced the work of Isaac Newton, who admired the work. For instance, the laws Huygens described in the Horologium Oscillatorium are structurally the same as Newton's first two laws of motion. Five years after the publication of his Horologium Oscillatorium, Huygens described his wave theory of light. Though proposed in 1678, it was not published until 1690 in his Traité de la Lumière. His mathematical theory of light was initially rejected in favour of Newton's corpuscular theory of light, until Augustin-Jean Fresnel adopted Huygens' principle to give a complete explanation of the rectilinear propagation and diffraction effects of light in 1821. Today this principle is known as the Huygens–Fresnel principle. As an astronomer, Huygens began grinding lenses with his brother Constantijn Jr. to build telescopes for astronomical research. He was the first to identify the rings of Saturn as "a thin, flat ring, nowhere touching, and inclined to the ecliptic," and discovered the first of Saturn's moons, Titan, using a refracting telescope. Huygens was also the first who brought mathematical rigor to the description of physical phenomena. Because of this, and the fact that he developed institutional frameworks for scientific research on the continent, he has been referred to as "the leading actor in 'the making of science in Europe'"
Robert Hooke
In 1660, Hooke discovered the law of elasticity that bears his name and describes the linear variation of tension with extension in an elastic spring. Hooke first described this discovery in an anagram "ceiiinosssttuv", whose solution he published in 1678 as Ut tensio, sic vis ("As the extension, so the force").His work on elasticity culminated in his development of the balance spring or hairspring, which for the first time enabled a portable timepiece – a watch – to keep time with reasonable accuracy.Hooke's announcement of his law of elasticity using an anagram was a method scientists, such as Hooke, Huygens, and Galileo, sometimes used to establish priority for a discovery without revealing details.Hooke used mechanical analogues to understand fundamental processes such as the motion of a spherical pendulum and of a ball in a hollow cone, to demonstrate central force due to gravity, and a hanging chain net with point loads to provide the optimum shape for a dome with heavy cross on top.
Isaac Newton
Cambridge University physicist and mathematician Sir Isaac Newton (1642–1727) was a fellow of the Royal Society of England, who created a single system for describing the workings of the universe. Newton formulated three laws of motion which formulated the relationship between motion and objects and also the law of universal gravitation, the latter of which could be used to explain the behavior not only of falling bodies on the earth but also planets and other celestial bodies. To arrive at his results, Newton invented one form of an entirely new branch of mathematics: calculus (also invented independently by Gottfried Leibniz), which was to become an essential tool in much of the later development in most branches of physics. Newton's findings were set forth in his Philosophiæ Naturalis Principia Mathematica ("Mathematical Principles of Natural Philosophy"), the publication of which in 1687 marked the beginning of the modern period of mechanics and astronomy.The Principia also achieved the first major unification in physics by demonstrating that the same physical laws govern both terrestrial and celestial motion, thereby establishing the foundations of classical mechanics. Newton refuted the Cartesian mechanical tradition that all motions should be explained with respect to the immediate force exerted by corpuscles. Using his three laws of motion and law of universal gravitation, Newton removed the idea that objects followed paths determined by natural shapes and instead demonstrated that all the future motions of any body could be deduced mathematically based on knowledge of their existing motion, their mass, and the forces acting upon them. However, observed celestial motions did not precisely conform to a Newtonian treatment, and Newton, who was also deeply interested in theology, imagined that God intervened to ensure the continued stability of the solar system.
Newton's principles (but not his mathematical treatments) proved controversial with Continental philosophers, who found his lack of metaphysical explanation for movement and gravitation philosophically unacceptable. Beginning around 1700, a bitter rift opened between the Continental and British philosophical traditions, which were stoked by heated, ongoing, and viciously personal disputes between the followers of Newton and Leibniz concerning priority over the analytical techniques of calculus, which each had developed independently. Initially, the Cartesian and Leibnizian traditions prevailed on the Continent (leading to the dominance of the Leibnizian calculus notation everywhere except Britain). Newton himself remained privately disturbed at the lack of a philosophical understanding of gravitation while insisting in his writings that none was necessary to infer its reality. As the 18th century progressed, Continental natural philosophers increasingly accepted the Newtonians' willingness to forgo ontological metaphysical explanations for mathematically described motions. Newton built the first functioning reflecting telescope and developed a theory of color, published in Opticks, based on the observation that a prism decomposes white light into the many colours forming the visible spectrum. While Newton explained light as being composed of tiny particles, a rival theory of light which explained its behavior in terms of waves was presented in 1690 by Christiaan Huygens. However, the belief in the mechanistic philosophy coupled with Newton's reputation meant that the wave theory saw relatively little support until the 19th century. Newton also formulated an empirical law of cooling and studied the speed of sound. Most importantly, Newton showed that the motions of objects on Earth and of celestial bodies are governed by the same set of natural laws, which were neither capricious nor malevolent. By demonstrating the consistency between Kepler's laws of planetary motion and his own theory of gravitation, Newton also removed the last doubts about heliocentrism. By bringing together all the ideas set forth during the Scientific Revolution, Newton effectively established the foundation for modern society in mathematics and science.
Other achievements Other branches of physics also received attention during the period of the Scientific Revolution. William Gilbert, court physician to Queen Elizabeth I, described how the earth itself behaves like a giant magnet. Robert Boyle (1627–1691) studied the behavior of gases enclosed in a chamber and formulated the gas law named for him; he also contributed to physiology and to the founding of modern chemistry. Another factor in the Scientific Revolution was the rise of learned societies and academies in various countries. The earliest of these were in Italy and Germany and were short-lived. More influential were the Royal Society of England (1660) an