Physics,+The+Discovery+of+Isaac+Newton


 * __People involved:__** Galileo Galilei and Isaac Newton


 * __General Timeline__**


 * **Year** || **Significant Events pertaining to Physics** ||
 * 1564 || Birth of Galileo Galilei ||
 * 1596-99 || Adapts and improves compass for gunnery calculations ||
 * 1602 || Experiments on pendulum ||
 * 1604 || Pendulum Law and Times-squared Law of Fall ||
 * 1605-08 || Work on speed of fall proportional time and parabolic trajectory of projectiles ||
 * 1606 || Invention of thermoscope ||
 * 1609 || Produces first nine power telescope ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1612 || <span style="color: #000000; font-family: 'Times New Roman','serif';">Bodies in Water published ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1623 || <span style="color: #000000; font-family: 'Times New Roman','serif';">The Assayer published ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1638 || <span style="color: #000000; font-family: 'Times New Roman','serif';">Discourse concerning Two New Sciences of Mechanics and Local Motions (Dynamics) published ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1642 || <span style="color: #000000; font-family: 'Times New Roman','serif';">Death of Galileo ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1643 || <span style="color: #000000; font-family: 'Times New Roman','serif';">Birth of Isaac Newton ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1665 || <span style="color: #000000; font-family: 'Times New Roman','serif';">Discovered gravity and generalized binomial theorem, develop a mathematical theory that later become infinitesimal calculus ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1665-66 || <span style="color: #000000; font-family: 'Times New Roman','serif';">Developments on theories of calculus, optics and law of gravitation, inverse square law and prepared Philosophiae Naturalis Principia Mathematica ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1668 || <span style="color: #000000; font-family: 'Times New Roman','serif';">Method of integration by infinite series became known ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1670-72 || <span style="color: #000000; font-family: 'Times New Roman','serif';">Investigated refraction of light by a glass prism, decomposed white light into a spectrum of colours ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1687 || <span style="color: #000000; font-family: 'Times New Roman','serif';">Philosophiae Naturalis Principia Mathematica on the inverse square law and three laws of motion published ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1704 || <span style="color: #000000; font-family: 'Times New Roman','serif';">Opticks published ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1721 || <span style="color: #000000; font-family: 'Times New Roman','serif';">Death of Newton ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1728 || <span style="color: #000000; font-family: 'Times New Roman','serif';">The system of the world published ||
 * <span style="color: #000000; display: block; font-family: 'Times New Roman','serif'; text-align: center;">1733 || <span style="color: #000000; font-family: 'Times New Roman','serif';">First draft of Book III of the Principia published ||


 * __Galileo__**

-15/02/1564: Galileo born in Pisa (in Tuscany) -1574-81: Educated at Florence and Vallombrosa -1581: Enrolls in University of Pisa, intended for medical degree -1583: Begins to study math in preference to regular studies -1585: Leaves university without a degree -1589-92: Professor of Mathematics at University of Pisa, becomes critical of Aristotle's teachings on motion -1592-1610: Professor of mathematics at University of Padua (Venetian Republic), sires three illegitimate children -1596-99: Adapts and improves compass for gunnery calculations -1602: Experiments on Pendulum, letter to Guidobaldo on long pendulums -1604: Pendulum law and times-squared law of fall -1605-08: Work culminates in finding speed of fall proportional to time and parabolic trajectory of projectiles -1606: Invention of Thermoscope (similar to thermometer) -1609: Produces first nine-power telescope -1609: Determines that luner suface is rough and mountainous -1610: Discovers moons of Jupiter, //Starry Messenger// published in Venice, move to Florence in employ of Grand Duke of Tuscany -1611: Discovers phases of Venus, elected to Lincean Academy in Rome -1612: //Bodies in Water// published in Florence -1613: //Letters on Sunspots// published in Rome -1616: Cautioned by Roman Inquisition of abandon Copernicanism -1620s: Several of his patrons and crtitics died e.g Bellarmine -1623: //The Assayer// published in Rome -1624: Visits old friend in Rome, now Pope Urban VIII, soon begins to write //Dialogue// -1632: //Dialogue between the Two Great World Systems// published in Florence -1633: Condemned by Inquisition for suspicion of heresy, tried for heresy and sentenced to life imprisonment, later house arrest, Returns home to Arcetri -1638: //Discourse concerning Two New Sciences of mechanics and local motions// (Dynamics) published in Leyden, Holland -1642: Galileo dies in Arcetri
 * Timeline**


 * Brief Biography**

Galileo Galileii was an Italian physicist, mathematician, astronomer and philosopher who played a major role the Scientific Revolution. He was born to Vincenzo Galilei, a famous lutenist and music theorist, and Giulia Ammannati in 1564 in Pisa, being the first of the six children. Galileo has been called “the father of science", noted for his discoveries and achievements that paved the way for modern science and the use of the Scientific Method. He had make significant contributions to the field of Astronomy and Physics, including study of motions, acceleration of free fall, Principle of Inertia, pendulum law, improvements to telescope, telescopic confirmation of the phases of Venus, discovery of four largest satellites of Jupiter, the uneven surface of the Moon and observation and analysis of sunspots. Galileo was the first scientist to use experimental observations and measurements together with Mathematics in science, marking the beginning of the Scientific Method. Galileo was a strong supporter of Copernicanism. He advocated heliocentrism which met with fierce opposition by other natural philosopher and clerics. He defended his views in his most famous work, //Dialogue between Two Great World Systems// published in 1632 and was later tried by the Inquisition. He was found "vehemently suspect of heresy," and was forced to recant, spending the rest of his life under house arrest.

-Heliocentrism (with Venus' phases and Jupiter's moons as evidence) -the use of telescope(beginning of scientific method) -Four moons around Jupiter (Disproved Aristotelian astronomy whereby ALL heavenly bodies should circle Earth) -Phases of Venus (proof of Venus' motion) - Equal speeds of fall ( extensive contributions to our understanding of the laws governing the motion of objects) this discory : **the acceleration due to gravity is independent of the weight of an object ,**was important to the formulation of a theory of gravitation by Newton - Concept of Inertia (an object in a state of motion possesses an ``inertia'' that causes it to remain in that state of motion unless an external force acts on it) it later became Newton's first law of motion. -pendulum law
 * Major Discoveries (Achievements)**

​ The observation of Venus' phases and Jupiter's moons had 2 possible implications: 1) Earth revolved around the Sun (heliocentrism) OR 2) Brahe's model was correct (Everything revolved around the Sun and the Sun revolved around Earth - geocentric model). **Due to the second possibility, there was still a debate as to which model was correct.**

=**Question: Why was Galileo adamant that he was right?? Was Galileo's idea revolutionary? Why?**= Zera: I think Galileo was adamant as he had observed the heavens and these observations corresponded with the theoretical principles, making him believe that he was right. I wouldn't say his idea was revolutionary as the Copernican model had already been developed but he simply reinforced those ideas with empirical observations, increasing the credibility of the theoretical explanations.

Zhang Peiwen: I believe Galileo was adamant because he believed that he could convince others. Before him, Copernicus was too afraid to publish his ideas on heliocentrism exactly because he could not convince the masses jus by coming up with a theory. However, Galileo was confident because he had solid observation as evidence to back his theory. We can draw a comparison here. In 1912, German scientist Wegener came up with the theory of continental drift. As we all know, this is a crucial theory in helping to explain geographical, biological and various phenonmena. However, Wegener could not solve the problem as of where the energy for the continental drift come from. As a result, people were not convinced and his theory lay hidden for many years before emerging again. (This example can also be compared with Kepler. He found out the change in speed of the plantes orbitting the sun, but he did not know the source of the force. Sir Isaac Newton solved this mystery.) (The comparison between Copernucis and Wegener is not very accurate, but some parts are quite similar :D)

-Craters and mountains on moon (not a perfectly smooth sphere, unlike what the Aristotelians had thought) -Observation of Sunspots -Optical principle of parallax (explanation for newly observed star) -Discovered that the Milky Way is composed of stars

-Inertia - A uniform force applied to an object -> Accelerated speed (whereas in the past people thought it would lead to a constant speed) - a body in motion continues to be in motion forever unless deflected by an external force (Therefore, state of uniform motion = state of rest)

-Oscillations and Waves (Pendulum) The Principle of Isochronism-- Each oscillation of a pendulum takes the same time despite changes in amplitude(at the age of 19) -Found **experimentally** that the path of an object thrown out is a parabola & bodies do not fall with velocities proportional to their weights. Successfully anticipating Isaac Newton's law of motion (contradicting the accepted teaching of Aristotle).
 * -**Constructed the first astronomical telescope (followed by the discovery the four largest satellites of Jupiter & the stellar composition of the Milky Way)


 * Use of Scientific Methods, Empiricism**

Whilst Galileo was in the process of observing Venus and its phases, an ex-pupil, Benedetto Castelli, sent him a letter stating that if the Copernican model were correct Venus must show phases. This is a classic example of the use of **Scientific Methods** because **the hypothesis was tested by observation, data was obtained and conclusions could be drawn.** (Hypothesis -> Experiments -> Data -> Conclusion) He also demonstrated the use of the telescope to the Senate and other natural philosophers, and the same findings were obtained. This is another feature of the Scientific Method since **similar results should be obtained for the same experiment (reproducibility)**.

As for **empiricism**, Galileo used the telescope to **observe** outer space in order to gain more knowledge on the Universe, and analysed his findings. (e.g. He found that Jupiter, a moving planet, had 4 moons orbiting it, meaning that it was possible for Earth's moon to orbit Earth even if Earth was moving.)

On top of doing numerous experiments, Galileo also applied another scientific method--drawing **implications** from conclusions. For example, when doing the experiment of inertia, in which he rolled small balls planes, he fully applied this method. Knwing that constructing a 100% smooth plane is clearly impossible, he drew an implication from the previous conclusion and stated the theory of inertia. This means that experiment, as well as hypothesis, does not need to be done physically, but can also be inferred, or rather indiectly demonstrated. This method is widely applied in both Galileo's work and the researchs of today's scientists.


 * Significance**

His work contributed to the Scientific Revolution in two ways - they led to the questioning of old theories and the formulation of new theories through the acquisition of new knowledge. Findings such as the observation of Jupiter's moons led to the questioning of old theories as it disproved the Aristotelian system whereby all celestial bodies revolved around Earth. This was also the case for the Phases of Venus as it supported Heliocentrism (since the phases were only possible if Venus revolved around the Sun), leading to a paradigm shift away from Aristotelian systems. Also, his parallactic explanation for newly observed star **provided basis for shift from old theories** that heavens were perfect and unchanging.

New knowledge such as the observation of Jupiter's moons showed that it was possible for Earth's Moon to stay in orbit even if Earth were moving. Other novel observations such as sunspots and the uneven surface of the Moon enabled people to have a better understanding of the Universe and contributed significantly to the Scientific Revolution in fields like astronomy. in the field of physics: -Galileo argued against the hoary Aristotelian traditions .Aristotle claimed that heavy objects fall faster than lighter ones.Philosophers in Galileo's time still believed that. But Galilei said doubt the came to doubt the belief in his youth by watching hailstones.He saw different-sized hailstones hitting the ground at the same time,and he decided they were falling at the same speed.He just could not believe that if they fell at different speed, they would always start off at just the right times and places to land together.In his essay ON MOTION ,Galileo gave an argument in support of the ideas that objects of different weight fall at the same rate.He questioned ,what would Aristotle determine the speed to be if two objects were tied together?He found the contradiction! As a result, he found the equal speed of fall,and claimed that a lock of wool and a piece of lead would fall together in a vacuum , which was proved in the experiment on the moon performed by astronaut.

In addition, theories such as inertia set the platform for natural philosophers to explain changes in motion rather than motion itself and inspired other natural philosophers like Sir Isaac Newton to continue research in this area (Newton's Three Laws).

The **Scientific Methods** e.g. Empirical observations were salient in the development of Science. He made observations using technology such as the telescope, which enabled one to have a more accurate understanding of the Universe. This was a leap in Science as previous natural philosophers such as Copernicus had theorized about the Universe without having made any true observations. For observations that clashed with theoretical explanations, it helped in the disproving of inaccurate theories and a shift away from old theories, contributing to the Scientific Revolution. Other than astronomy, he applied the scientific method in experiments on the rate of fall in experiments (measuring time taken for balls to roll down slopes) using a water clock. He is alleged to have repeated this hundreds of times, and this is important in experimentation since repeated similar results give higher credibility. From organized experiments and thorough, systematic observations, correct generalizations could be developed. Also, after the establishment of the scientific method, the need for development of more sophisticated technology and instruments for observation resulted in improvements to these apparatus for instance, in the development of telescopes with higher magnification (e.g. from 3x to 30x), and allowed for better observation and resulted in the acquisition of more accurate knowledge. This, then, would have contributed to the Scientific Revolution.

Galileo resolved to research motion by the same method astronomers had been using for 2000 yrs.They invented models of the heavens ,and then justed the models match their observation.Galileo would create a mathematical model for the motion of objects that would produce the same numerical for distances and times that he could measure. No one had previously taken this approach in any science except astronomy. that is why we call Galileo "first physicist". Galileo could have been said to be the **first modern scientist** since he relied on observations, his principles were consistent with observations, he had the courage to challenge old and faulted theories and also published his ideas widely (e.g. when he published //The Dialogue// in the vernacular).


 * His Clash with the Church**

Galileo had insinuated that the Church had interpreted the Bible wrongly, when he had no authority to do so (only priests had the right to question the Bible). He had also refused to keep his discoveries to himself and promoted his idea as the TRUTH, in contrast to Copernicus who had promoted them as ideas. The church viewed this as a threat to their power and authority. The Thirty Year War fuelled this as the Church needed the support of the people and in order to prevent them from questioning their credibility, tried Galileo for heresy.

After publishing Dialogues on the two Chief World Systems, which ws in the late 1632, the Holy Office of the Inquisition ordered Galileo to go to Rome for examination. In 1633 April, the old and sickly Galileo arrived at Rome and was immediately charged. The charges include heresy, teaching and defending the Copernicanism(heliocentrism) and he was forced to give up the ideas. As shown in the time line, Copernicus' book was named one of the prohibited books and heliocentrism was officially announced as heretical.

Galileo was "greatly insulted" during the hearings. He was forced to kneel down when the church announced his sentence and was forced to declare the following statement.

//" I have been judged vehemently suspect of heresy, that is, of having held and believed that the sun in the centre of the universe and immoveable, and that the earth is not at the center of same, and that it does move. Wishing however, to remove from the minds of your Eminences and all faithful Christians this vehement suspicion reasonably conceived against me, I abjure with a sincere heart and unfeigned faith, **I curse and detest the said errors and heresies,** and **generally all and every** error, heresy, and sect **contrary to the Holy Catholic Church**."// (Quoted in Shea and Artigas 194)

According to legend,as the 70-year-old Galileo left the courtroom,he whispered to himself,"And yet it does move!"

Galileo was sentenced to house arrest. During the last days of his life in Florence, his last book, //Discourses on the Two New Sciences// was published. As he had promised, heliocentrism was nowhere to be found in the book. Galileo died on January 8, 1642.

By the time of Galileo's death,many scientists had become convinced that the heliocentric theory of the universe was valid,even though the Catholic Church continued to oppose it.Compared with Copernicus,who promoted his idea as an abstraction,another set of mathematical tools for doing astronomy,Galileo boldly published his ideas as "the nature of universe",this ultimately lead to make his Europeans aware of the new picture of the universe.


 * Famous Stories**

//The Leaning Tower of Pisa// When Galileo arrived at the uneversity of Pisa, people were debating on Aristotle's "laws" of nature. In Aristotle's thoery, heavier objects fell faster than lighter objects, which was also widely accpeted by common sense. Thus,it's deemed as a truth, and some natural philosophers actually tested the conclusions by conducting an experiment. As a result, Galileo decided to give it a try. A greater height was required in the experiement. Thus, the 54-meter-tall Tower of Pisa was chosen. On the top of the building, Galileo let go of balls of varying weight. He found that they all landed at the base of the building at the same time. The experiment was said to be witnessed by a huge crowd of scholars and common people alike. Aristotle was shown to be wrong.

//The Discovery of the Law of Pendulum// When Galileo was 19 years old, he noticed a lamp swinging overhead while he was in a cathedral. Out of curiosity to find the period of the lamp to swing back and forth, he used his pulse to time large and small swings. Along with thousands of experiments back home, Galileo eventually discovered that the period of each swing was exactly the same. The law of the pendulum, which was later used to regulate clocks, was thus discovered and made Galileo instantly famous.
 * Was the Church against new discoveries? **

Perhaps, it was not Galileo's discoveries that led to his condemnation but the fact that he promoted his ideas as the truth, insinuated that the Church's interpretation of the Bible was wrong and refusal to keep his discoveries to himself meanwhile. This can be supported as Christopher Clavius, cheif Jesuit astronomer and correspondent with Galileo, had looked through his telescopes and drawn conclusions according to what he had seen (Glenn, 1996). The fact that he was willing to observe the heavens and not simply refuse Galileo's proposed ideas shows that the Church was receptive to new knowledge. In addition, it was written in //The twenty greatest minds// that "To maintain a thing theologically was a doctrinal act, not at all the same as to adopt positions in the spirit of philosophical discourse", meaning that the Church had the duty to uphold religious doctrines but were not against new discoveries. As a live example, the church did not oppose Copernicus heliocentrism in the first place. They only voiced their opposition when the whole movement began to gather strength in Galileo's time. This proves that it was Galileo's "aggressive" mean that led the church to be against him.

__**Newton**__


 * Timeline**

<span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">-04/01/1643: Newton was born in England -1646 : (when he was 3) his mother remarried and left him to live with his maternal grandma. -1655-1660: Educated at The King’s school -1661: Admitted to Trinity College, Cambridge University. -1664: Received a scholarship -1665: Saw an apple fall in his orchard <span style="font-family: 'Arial Unicode MS','sans-serif'; font-size: 9pt;">，c <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">onceived that the same force governed the motion of the Moon and the apple
 * Discovered generalized bionomial theroem, began to develop a mathematical theory that would later become infinitesimal calculus.

- 08/1665 obtained his degree -1 665-1666: Studied at his home in Woolsthorpe, saw the development of his theories on calculus, optics and the law of gravitation (inverse square law, g = 1/d^2 whereby g is gravitational force and d is the distance from the Earth's core) and prepared //Mathematical Principles of Natural Philosophy// - 1667: Returned to Cambridge as a fellow of Trinity - 1668: Method of integration by infinite series became known - 1669: Elected Lucasian Professor of Mathematics -<span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1670-1672 lectured on optics ( investigated the refraction of light by a glass prism, decomposed white light into a spectrum of colours) <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1671 was elected a Fellow of the Royal Society of London <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1672 published an edition of //Geographia generalis// by the German geographer Varenius <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1679-1680 Correspondence with Hooke <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1687 publishment of "Principia" (three universal laws of motion, inverse square law ) <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1689 was elected Member of Parliament for the University of Cambridge to the Convention Parliament of 1689 <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1690 Newton's friends proclaimed the priority of Newton's methods of fluxions. The Calculus Priority Dispute began,he was involved in a dispute with Leibniz until the Leibniz’s death in 1716. <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1696 moved to London as Warden of the Royal Mint <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1703 became President of the Royal Society of London <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1704 published //Opticks// <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1705 was knighted in Cambridge <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1707 Newton’s Cambridge lectures, delivered from about 1673 to 1683, were published <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1710 "On the Nature of Acids" published an incomplete theory of chemical force, concealing his exploration of the alchemists <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">21/05/1721 Newton died in his sleep in London <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">Posthumously published writings: <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1728 //The Chronology of Ancient Kingdoms Amended// <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1728 //The System of the World// <span style="font-family: 宋体; font-size: 9pt;">— <span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">1733 the first draft of Book III of the //Principia//, and //Observations upon the Prophecies of Daniel and the Apocalypse of St John//


 * Brief Biography**

Sir Isaac Newton was an english experimenter,empiricist,physicist,mathematician,and natural philosopher who was considered by most people to be the most influntial man in human history and the greatest single scientific mind of all time.He was born in the little English village of Woolsthorpe in 1642, and was under the care of his grandparents. The coldness they met him with left him with an aloof character. The first formal schooling he received was at a small school of Skillington and he later enrolled in King's school. Though Mathematics was not taught, he studied by himself, perhaps by reading books that had belonged to a teacher at King's who had recently died. Nearly 19 years of age, he started receiving Greek, Latin and Bible study lessons at Cambridge University, earning a scholarship in 1664 which gave him four more years' time to earn the Master's degree (M.A.). Newton began to pursue his interests in Math, and attended Isaac Barrow's (first professor of Mathematics) lectures. In mathematics, Newton shared the credit with Gottfried Leibniz for the invention of the calculus, which aimed to describe rates of change. During the plague years of 1665-1667, he returned home, and conceived the law of gravitation after witnessing an apple fall to the ground. He also worked on other areas such as vision and colour, often endangering his health by experimenting on himself.

At the age of 27, Isaac Newton was appointed as the successor to Isaac Barrow as the Lucasian chair of Mathematics. Impressed by his accomplishments including the advent of an improved telescope which minimised refraction, he was invited by the Royal Society to join as a member, an offer he promptly accepted. This led to conflicts with another member, Robert Hooke, who accused Newton of stealing ideas from his book titled //Micrographia.//

Throughout the 1670s, he worked on alchemical experiments, and perceived alchemy as "a way to increase 'the knowledge of God and secondly the way to find out about true medicines'" (Rosinsky, 2008).

Of course, the work he is most famous for is the law of universal gravitation whereby all objects with mass exert an attractive force on each other. This might have been sparked by correspondence with Hooke, which started in November 1679, whereby Hooke questioned Newton about planetary motion. Although Newton broke off the corespondence, Hooke's letters provided a conceptual connection between central attraction and a force falling off with the square of distance, possibly influencing Newton who later theorized that the gravitational attraction between two objects was inversely proportional to the square of the distance in between. This was published in the Principia in which he described gravity and the three laws of motion. These dominated the scientific view of the physical universe for the next three centuries. It also removed the last doubts about heliocentrism and advanced the scientific revolution.

Throughout his life, Newton only found out how the Universe works and never bothered to find out why things happened. He believed it "vain and scientifically improper to seek out an underlying explanation for what he saw as God's handiwork" (RGS History Notes 2010) and reinforced this message during his presidency of the Royal Society when he said "hypotheses non fingo" (I frame no hypotheses). Newton remained lucid and was a prominent figure even in the last years of his life. He died in his sleep in London on 31 March 1727 at the age 84 and remains as the only natural philosopher to have been buried in Westiminster Abbey.


 * Major Discoveries**

Newton is famous for his three laws which describe motion. He had also conceived the theory of Universal Gravitation, and postulated that everything which has mass exerts a force on every other objects with mass. This involved Mathematical calculations and he devised a branch of Math, known as calculus, to explain elliptical orbits. He also calculated that the gravitational force at surface of Earth is hundreds of times stronger than that at the centrifugal force Earth experiences, providing a solution for ancient idea that the Earth would fly apart due to centrifugal force. Other than that, his extensive work on light and the splitting of light into the spectrum led him to theorize that light consisted of streams of particles and paved the way for the wave-particle duality theory of light. Details of his field of research and contributions are as follows:


 * 1) Optics**

<span style="font-family: 'Arial','sans-serif'; font-size: 9pt;">Newton investigated the composition and refraction of light through a series of experiments, inspired by the writings of Kepler and Descartes he had read in his college years. As a result, he discovered measurable, mathematical patterns in the colour of light. Contrary to the theories of Aristotle and other ancients, Newton found that white light, instead of being the purest light, is actually a mixture of infinitely varied coloured light rays. Newton demonstrated this in one of his most famous experiment, //experimentum crucis//, by decomposing white light into a spectrum of colours using a prism, and recomposing the multicoloured spectrum into white light by a lens and a second prism. In addition, by separating out a coloured beam and shining it on various objects, Newton showed that the coloured light does not change its properties. Its colour remains the same whether it was refracted, scattered or transmitted. Therefore, he concluded that white light is a “heterogeneous mixture of differently refrangible rays” and the colours of the spectrum cannot be themselves individually modified themselves, but are “original and connate properties”

Newton applied this concept to derive at the notion that the lens of any refracting telescope would disperse light into colours. To avoid this problem, he constructed a telescope using mirror as the objective, building the design of the first known functional reflecting telescope (known as the Newtonian telescope today) produced in 1668 which eliminated the problem of suitable mirror material and shaping technique. In 1671, the Royal Society asked for a demonstration of his reflecting telescope. Their interest encouraged him to publish his notes //On Colour//, which he later expanded into his // Opticks //

<span style="font-family: 'Arial','sans-serif';">Newton’s theory of light is fundamentally corpuscular or particular, opposing the widely held theory in 17th century that light consisted of a wave of undulatory motion. In effect, since light travels in straight lines and casts a shadow, Newton proposed that light was composed of discrete particles moving in straight lines in the manner of inertial bodies. This could explain the constant and unchanging properties of the separate colors of light, since light itself is particles. However, at various points in his career, Newton in effect combined the particle and wave theories of light, laying down the foundations for the wave-particle duality of light. Newton verged on sound-like waves (Opticks Bk.II, Props. 12) to explain the repeated pattern of reflection and transmission by thin films observed in a series of experiments concerning the colors of these films. Nevertheless, he retained his theory of 'fits' that disposed corpuscles to be reflected or transmitted (Props.13).

These ideas were published in the //Opticks//, Newton’s most comprehensive work on light and colour. //Opticks// was divided into three books, moving from definitions, axioms, propositions, and theorems to proof by experiment. In Newton’s words, the purpose of //Opticks// was ‘not to explain the properties of light by hypotheses, but to propose and prove them by reason and experiments’. With the subtle blend of mathematical reasoning and empirical observation, the //Opticks// became the model for experimental physics in the 18th century. Like Francis Bacon, Newton believed that one must observe phenomena before attempting to explain them. His work relies heavily on empirical observations and data derived from experimentations. He employs inductive reasoning, focusing on the study of a particular pattern before making generalizations about natural causes. In addition, he recognized the importance of applying the theories to test whether they described what was observed. Therefore, most of Newton’s theories can be applied to everyday world, giving science its practical purpose. Newton’s work promoted Baconian empiricism in the study of science, developing the scientific method through his works that rely on this approach.


 * 2) Mathematics**

<span style="display: block; font-family: Arial,Helvetica,sans-serif; font-size: 9pt; text-align: left;"><span style="font-family: Arial,Helvetica,sans-serif; font-size: 9pt;"><span style="font-family: Arial,Helvetica,sans-serif; font-size: 9pt;"><span style="color: #000000; font-family: Arial,Helvetica,sans-serif; font-size: 9pt; line-height: 150%;">Newton made fundamental contributions to Mathematics especially in analytic geometry, algebra and calculus. His work had been said "to distinctly advance every branch of mathematics them studied". Newton invented infinitesimal calculus which provided solutions to the contemporary problems in analytical geometry of drawing tangents to curves (differentiation) and defining areas bounded by curves (integration ). It consisted of differential calculus and integral calculus which are used for the techniques of differentiation and integration respectively. The calculus is a study of change which aims to establish a relationship between two or more variables (functions).

Newton had discovered the general methods of resolving problems of curvature, embraced in his "method of fluxions" and "inverse method of fluxions". Fluxional calculas is a method for treating changing or flowing quantities. Fluxion represents the rate of change of a fluent, a continuously changing flowing quantity. This method was used in his second law of motion, whereby Force = Mass × Acceleration involves differential calculus because acceleration can be expressed as the derivative of velocity. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 9pt;">In addition, Newton is also credited for the creation <span style="font-family: Arial,Helvetica,sans-serif; font-size: 9pt;">of the generalized binomial theorem which allows real complex exponents other than non-negative integers in a formula, Newton’s identities concerned with the relations between two types of symmetric polynomials, power sums and elementary symmetric polynomials, Newton’s method for finding successively better approximations to the zeroes (or roots) of a real-valued function. Furthermore, Newton made substantial contributions to the theory of finite series too. He also the first to use fractional indices and to employ coordinate geometry to derive solutions to Diophantine equations.

Newton's work on pure mathematics was virtually hidden from all but his correspondents until 1704, when he published, with //Opticks//, a tract on the quadrature of curves (integration) and another on the classification of the cubic curves. His Cambridge lectures, delivered from about 1673 to 1683, were published posthumously in 1707. Newton also developed a more complete account of his method of infinitesimals in the book //The Method of Fluxions and Infinite Series// which was published in 1704, nine years after his death. His cambridge lectures, delivered from about 1673 to 1683 were published later in 1707.

Newton shared Cartesian's belief in the power of mathematics to describe nature. His use of Mathematics in the explanation of forces and the Universe was of great significance as it symbolised the birth of a Mechanical Universe, whereby phenomena and the workings of the Universe could be expressed in mathematical terms as workings could be done step by step through deduction and this increased the reliability of theoretical explanations. In addition, the use of Mathematics to describe the Universe was a leap in the intellectual discovery of Man and showed that the understanding of the Universe was not confined to the divine.


 * 3) Mechanics and Gravitation**

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 9pt; line-height: 150%;">Newton’s research in mechanics falls into three major periods: the plague years 1664-1666, the investigations of 1679 following Hooke’s correspondence, and the period of 1684-1687 after Halley’s visit.

Newton’s work on gravity began in Woolsthorpe. Contrary to the famous story that Newton discovered gravity when hit on the head by a falling apple in his orchard, at the time of his famous moon test, Newton had yet to arrive at the concept of gravitational attraction. Early manuscripts suggest that in the mid 1660’s, Newton did not think in terms of the moon’s attraction but of the moon’s centrifugal tendency to recede. He had yet to consider the possibility of action at a distance due to the influence of mechanical philosophy. Newton hypothesized that the moon’s centrifugal tendency to recede to be equal and opposite to some unknown mechanical constraint. He proposed a circular orbit and an inverse square relation derived from Kepler’s third law of planetary motion which states that the square of a planets orbital period is proportional to the cube of its mean distance from the sun. To prove his hypothesis, Newton compared the restraint on the moon’s tendency to recede with the observed rate of acceleration of falling objects on earth to test the inverse square relation against empirical data. However, Newton could not obtain accurate data such as the size of the earth and his calculations did not turn out right. Thus, he abandoned the problem.

<span style="font-family: 'Arial','sans-serif'; font-size: 9pt; line-height: 150%;">In late 1679 and early 1680, an exchange of letters with Robert Hooke renewed Newton's interest. Hooke wrote to Newton about a hypothesis presented in his //Attempt to Prove the Motion of the Earth// (1674). He proposed that planetary orbits result from a tangential motion and an attractive motion towards the central body, indicating a central attracting force that diminishes with the square of distance. With the crucial insights provided the Hooke, Newton rejected his earlier notion of centrifugal tendencies in favor of central attraction and worked out the mathematical proof that the elliptical planetary orbits proposed by Kepler resulted from a centripetal force (gravity) inversely proportional to the square of the radius vector. <span style="font-family: Arial,Helvetica,sans-serif; font-size: 9pt; line-height: 150%;">Newton communicated his results to Edmund Halley who visited Cambridge in 1684. Halley encouraged Newton to publish his findings. He financed the Principia and saw it through the press to publication in July 1687.

The Principia was Newton’s masterpiece. It is regarded as one of the most powerful and influential work in the history of science which marked the start of a new era in science. The Principia was divided into three books with two further editions published in 1713 and 1726. In this work, Newton stated the three universal laws of motion and the law of universal gravitation which combined Kepler's three laws of planetary motion and Galileo's experiments on free fall, outlining the fundamental force at work in the universe. These laws laid down the foundation for classical mechanics and modern physics. In formulating physical theories, Newton developed a new branch of mathematics, now known as calculus. He gave many of his proofs in geometric form of infinitesimal calculus. In addition, he produced the first analytical determination of the speed of sound in air based on Boyle’s law. In his third and final book, Newton extended his three laws of motion to the frame of the world, demonstrating that gravity tended to all bodies, particularly the movements of planets and their satellites. The book offered estimates of relative masses for the known planets and the sun, show how the law of gravity can account for irregularities in the motion of the moon, identifies the oblateness of the figure of Earth, accounts for tides including the phenomena of spring and neap tides by the perturbing and varying gravitational attractions of the sun and moon on the Earth’s waters, explains the precession of the equinoxes as an effect of the gravitation attraction of the moon on Earth’s oblateness and gives theory for the determination of the orbits of comets.

<span style="font-family: 'Arial','sans-serif'; font-size: 9pt; line-height: 150%;">This illustrated the greatness of Newton’s laws, that they were universal, backed by powerful evidence from everyday observation and experience. They could explain the motions of every object from a falling apple in the terrestrial world to the moving planets in celestial world, revealing the fundamental laws that govern the universe, in other words, how the universe works. In addition, Newton’s theories described and explained the motions of objects with the clarity of mathematics using powerful formulas and equations instead of the mechanist’s explanation of invisible swirling particles at work. This spread the light of mathematics in science which up to then had remained in the darkness of conjectures and hypotheses. The methods employed by Newton in his investigations become synonymous with physics, practiced for three and a half centuries. Today the two methodological aspects that Newton outlined could be called analysis and synthesis. The Principia <span style="color: black; font-family: Arial,Helvetica,sans-serif; font-size: 9pt; line-height: 150%;">was considered the most important text in physics for centuries. It not only affected the content, but the style of science. The idea that science is a precise description of what happens rather than an explanation of why it happens is an expansion of Newton’s gravity theory.

--**Newton's Laws of Motion and Universal Gravitation**

= = <span style="font-family: Arial,Helvetica,sans-serif; font-size: 9pt;">In //Principa// Newton defines mass, velocity, and acceleration and his three laws of motion.


 * 1) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 9pt;">Every body continues in tis state of rest or uniform motion in a straight line, unless it is compelled to change that state by forces impressed on it (inertia)
 * 2) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 9pt;">The change in motion is proportional to the motive force impressed and is made in the direaction of the straight line in which that force is impressed (F=ma)
 * 3) <span style="font-family: Arial,Helvetica,sans-serif; font-size: 9pt;">To every action there is always an opposed and equal reaction

<span style="font-family: Arial,Helvetica,sans-serif; font-size: 9pt;">Newton’s first law, also known as the law of inertia, is a restatement of what Galileo had described and Newton gave credit to Galileo for this. Galileo realized that force acting on a body determines acceleration, not velocity. This insight leads to Newton’s first law which states that no force means no acceleration and hence the body will maintain a constant velocity.

From the three laws, Galieo's experiments on free fall and Kepler's Laws, he devised the universal law of gravitation. He showed that the force that causes kepler's elliptical orbits is a central force, directed to the center of motion. He also demonstrated that planets under the influence of this central force follow Kepler's second law. This force, Newton discovered was gravity. According to Newton, every massive particle in the universe attracts every other massive particle with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them.

Newton used the thought experiment to illustrate the how gravity held the planets and satellites in their orbits. Suppose we fire a cannon horizontally from a high mountain; the projectile will eventually fall to earth, as indicated by the shortest trajectory, because of the gravitational force directed toward the center of the Earth and the associated acceleration. But as we increase the muzzle velocity for our imaginary cannon, the projectile will travel further and further before returning to earth. Finally, Newton reasoned that if the cannon projected the cannon ball with exactly the right velocity, the projectile would travel completely around the Earth, always falling in the gravitational field but never reaching the Earth, which is curving away at the same rate that the projectile falls. That is, the cannon ball would have been put into orbit around the Earth. Newton concluded that the orbit of the Moon was of exactly the same nature: the Moon continuously "fell" in its path around the Earth because of the acceleration due to gravity, thus producing its orbit.


 * Significance**

Newton's achievements revolutionised classical science. His work on the laws of motion and gravity demostrated that universl laws, mathematically proved, could explain all motions in the universe, from the movements of planets in the celestial world to the an falling apple in the terrestial world. He revealed that the natural world could be known by human investigations, breaking the perception that not all areas of knowledge were accessible to humans, that humankind is entitiled to comprehend only what God deigns to reveal. This is a new idea played a pivotal role in the evolution of human self awareness, providing a psychological turning point which brought about liberation and empowerment. With this new understanding, scientific development was greatly advanced as people are encouraged to explore the world in the language of science.

Newton's work redefined the meaning of science. He demostrated that science was not purely theological, but practical. For instance his theories and laws were backed by powerful evidence from everyday observations and experiences, accounting for most physcial phenomena. This showed that science had practical applications in the everyday world. For example, Newton's laws of motion helped engineers in machinery, allowing them to design new working parts for machines. His universal law of gravitation also helped in map-making with the realisation that the Earth was not a perfect sphere. Moreover, the mathematics of gravity could be applied in the prediction of tides even in unsailed waters, promoting maritime trade in an age of seaborn empires. The numerous applications of science demostrated that science could be used to improve our lives. This gave humanity greater power over its enviroment and encouraged confidence in human powers which helped to put an end to the doubts and uncertainties of the previous age. Thus, more people were inspired to engage in the study of science for the benefit of mankind. In addition, Newton's use of mathematics in formulating his theories and hypothesis shed light to mathematical reasoning in science.

Newton's work provided a single comprehensive explanation of all motions, outlining the foundamental forces that governs the universe, thus giving mankind for the first time an orderly and comprehensible picture of the heavens and earth. This new perpeception of the universe created a cosmology in which the world was seen largely in mechanistic terms. The universe was seen as a huge, regulated and uniform machine that operated according natural laws in absolute, time, space and motion. As a result, nature was conceived as machinery, eliminating mythical ideas and the previous assumptions of the presence of divine purpose in nature. This drive on mechanical understanding of nature brought about the empowerment of Mathematics as the language of science.

Newton's work also united the philosophical theories of Bacon (empiricism and induction) with that of Descarte's (deduction and rationalism) which formulated a new way of scientific investigation, contributing to the development of the scientific method which formed the building pillars of science. For instance, Newton makes use of experimentation and empircal observation (Bacon) together with logical reasoning and deduction (Descartes) in tackling scientific problems. Theories employed mathematical reasoning, proving ideas with workings and logic done in a step by step manner (deduction), and these theories were also backed up or refuted with experimentation and empirical evidence. (Scientific Method). This was incoporated in Newton's Rules of Reasoning in Philosophy included in the second and third editions of Book III of Principia. For example, in Rule IV, Newton states that //"In experimental philosophy we are to look upon propositions inferred by general induction from phenomena as accurately or very nearly true, notwithstanding any contrary hypotheses that may be imagined, till such time as other phenomena occur by which they may be made more accurate or liable to exception."// Newton also stated "(To) never to accept anything for true which I did not clearly know to be such". This is pro-foundational skepticism and was incorporated by Newton via experimentation to determine if what he knew was the truth. Newton also drew on Descartes' stress on Mathematics and discovered calculus which he used to derive his univesal law gravity.

Newton's work shaped science in a way that focuses on how the universe operated not why. This is illustrated in his refusal assign a cause to gravity. He believed that it is unnecessary and improper to frame hypotheses of things that were not implied by the phenomena, expressing this in his famous expression "hypotheses non fingo".

All in all, Newton's work not only encouraged a paradign shift in persperctives but also reformed man's perception on knowledge, pushing the scientific revolutions with new enlightenment.

<span style="color: #ff0300; font-family: 'Arial Black',Gadget,sans-serif; font-size: 130%;">Questions: In what other ways did Newton unify both Descartes' and Bacon's theories? How did all these ideas affect Scientific development? In my opinion, these ideas either resulted in a paradigm shift away from old theories or new and possibly more accurate scientific knowledge led to the formulation of new theories. Do you think Galileo or Newton played a greater role in Scientific revolution? Why?

Zera: I think Galileo played a greater role as his observations were proof of a heliocentric system and his discoveries such as the equal rate of acceleration led to a better understanding of the universe and paved the way for future natural philosophers like Isaac Newton who came up with theoretical explanations for these phenomena (However, it is quite a difficult choice since Newton was the one who had produced a lot of the theories and these theories worked hand in hand with observations to result in progress in Science.)

Zhang Peiwen: In my opinion, Sir Isaac Newton played a more important role in Scientific Revolution. Being widely regarded as the most influential scientific personnel of all time, Sir Isaac Newton wrapped up the previous discoveries of Galileo and Kepler, stating an earth-shaking theory of global gravitation. In addition, he applied the thinkings of both Descarte and Bacon, further publisizing the scientific methods, leading more accurate theories to come. More preciously, his gravitation and motion theories are widely applied, from a fallininapple to the orbitting planets. They knew the tides and a lot more. With his science, people were able to arrange their life in alignment with nature, and even think about conquerring the mighty nature to serve themselves better. These also posed a change in people's mindset.

In my opinion, these ideas either resulted in a **paradigm shift away from old theories** or **new and possibly more accurate scientific knowledge led to the formulation of new theories.**

Were they revolutionary? Why? Zera: I guess, first, we should define the term "revolutionary". "Revolutionary" to me means to have had a long-lasting impact on future advances. Since that is the case, I feel that both Galileo and Newton were revolutionary. As explained above, Galileo used empirical, concrete observations in the formulation and repudiation of theories, and this has a long-lasting impact as it played a major role in the formation of the Scientific Method. The Scientific Method ensures that standardised ways of experimentation are carried out and that all conclusions/inferences/generalizations are supported by observations instead of mere speculation, leading to a greater accuracy in acquired knowledge. Newton laid the foundation for Science as he had explained a problem which had directly/indirectly perturbed natural philosophers for centuries with his law of gravitation, and also united Descartes and Bacon's theories in experimentation. In addition, he led to a new belief that the understanding of how the Universe worked was not confined to the divine, "a belief in the unfettered entitlement to knowledge", which could be said to be "the most important intellectual development along the lengthy time line of the past millenium". (McGraw, 2005).


 * References

-Books** 1) MacLachlan, J. (1997). //Galileo Galilei First Physicist//, New York: Oxford University Press 2) Gribbin, J. (2002). //The Scientists - A history of Science told through Eyes of its Greatest Inventors,// New York: Random House, Inc. 3) Glenn, J. (1996). //The twenty greatest minds. Galileo Galilei: pg 24-26, Isaac Newton: pg 52-54.// Published by Saraband Inc. 4) McGraw, H. (2005). //World History - Vol. 2: 1500 to the Present, 8th ed. Article 18, pg 82-84.// 5) Rosinsky, N.M. (2008). //Sir Isaac Newton: Brilliant Mathematician and Scientist//. Published by Compass Book Points. 6) Christianson, G.E. (1996). //Isaac Newton and the Scientific Revolution.// Published by Oxford University Press, Inc.

1) Galileo Galilei - Wikipedia, the free encyclopedia. (n.d.). Retrieved 16 February 2010 from [] 2) Discourse on the Method - Wikipedia, the free encyclopedia. (n.d.). Retrieved 23 February 2010 from [] 3) Isaac Newton - Wikipedia, the free encyclopedia. (n.d). Retrived 24 February 2010 from [] 4) Sir Isaac Newton - Professor Robert A Hatch Scientific Revolution Homepage. (n.d) Retrived 24 February 2010 from [] 5) The scientific Revolution - Suite101 Retrived 24 February 2010 from [] 6) Philosophiæ Naturalis Principia Mathematica - Wikipedia, the free encyclopedia (n.d) Retrived 27 Feb 2010 from [] 7) Calculus - Wikipedia, the free encyclopedia. (n.d.). Retrieved 27 February 2010 from http://en.wikipedia.org/wiki/Calculus#Applications 8) Isaac Newton's life - Isaac Newton institue for mathematical sciences, Retrived 27 Feb 2010 from []
 * -Websites**

Others RGS Teacher's Notes 2010

Group Members: Yang Jing, Yueyue, Xu Hui, Peiwen, Zera