HISTORICAL REVIEW OF SCIENCE II:
FROM THE RENAISSANCE TO TODAY

The second part of our review starts with the background to the De Revolutionibus Orbium Coelestium (On the Revolutions of the Heavenly Spheres) by Nicholas Copernicus (1473-1543), which was completed sometime between 1530-1533 and published in 1543. De Revolutionibus, comprising 6 books, and a previous 20-page hand-written manuscript called Commentariolus, published around 1507, revolutionized astronomy, for Copernicus had put the Sun at the center of the universe, see figure 1. This was in complete contravention to conventional religious dogma and so a Lutheran theologian, Andreas Osiander, who took responsibility for publication, had declared in the preface, and completely without Copernicus' knowledge, that the book was pure theory and not the literal truth! One can imagine skeptics arguing:

and clerics saying:

In fact, the authorities, who believed emphatically in the Ptolemaic system at first took little notice of the Copernican Theory and in some ways they regarded it as a passing fad, rather as we regard some of the fashions and music of teenagers today! It didn't go away and by the end of the 16th century it was very risky to be a supporter of the Copernican theory, as Giordano Bruno discovered. It is against this sort of background that I find the accomplishments of the scientists of the late Renaissance, particularly Galileo, so remarkable. And so in the middle of the 16th century again we have the Sun back at the center of the solar system, where it had been put originally by Aristarchus almost 2000 years earlier, before the intervention of Aristotelian philosophy! In 1572 another occurrence "shook" the establishment and that was the sudden observation of what we now know was a supernova by Tycho Brähe, a Danish astronomer of noble birth, figure 2. Brähe, using the method of parallax determined that this new, bright object that had suddenly appeared in the constellation of Cassiopeia, was among Copernicus's fixed circle of stars. According to Aristotle the heavens, made of quintessence, were unchanging but Brähe's observation of the "birth" of a star changed all that. Brähe was not a Copernican because his "revised" version of the solar system, although complicated, still retained a central Earth and that put him in much less danger with the authorities than some of his contemporaries. Actually, Brähe was a very interesting character. Apparently, he was kidnapped by his uncle at birth. Also, in December 1566 he quarreled with another Danish nobleman, Manderup Parbsjberg, during a party at a professor's house over who was the better mathematician. In the best tradition of medieval male macho-ism they fought a duel a week later to seek satisfaction and poor Tycho lost part of his nose! He repaired it with a pseudo-nose made of gold, silver and wax, and that's how he appears in some of the later paintings of him, see figure 3.

Brähe died, according to stories that circulated later, of a punctured bladder when he was drunk. Be that as it may, he was an outstanding observational astronomer and in 1599, two years before his death, he was appointed Imperial Mathematician to the Holy Roman Emperor, Rudolph II, in Prague. Johannes Kepler, figure 4, joined him as an assistant and so had access to a large body of very high quality data, all taken before the invention of the telescope, I might add. When Brähe died, Kepler succeeded him as Imperial Mathematician.

The accuracy of Brähe's data allowed Kepler to formulate his three Laws of planetary motion, in 1609 and 1619. These laws dealt in turn with the shape of the orbits, the speed within the orbit and the relationship between the size of the orbit and period of revolution. The first law itself demonstrated beyond all doubt the essential correctness of the sun-centered solar system. Kepler also contributed greatly to the subject of optics; in 1604 he showed that sight was due to the reception of light rays in the eye and he wrote on the optics of the telescope, introducing a design using two convex lenses in 1611 (that forms the basis for modern refracting telescopes) [1]. He also corresponded enthusiastically with Galileo about his telescopic discoveries.

In my humble opinion Galileo Galilei and Isaac Newton are the two greatest scientists our civilization has known and so I will spend a little more with their biographies.

Galileo, see figure 5, was a pioneer of modern applied mathematics, physics and astronomy. He initially studied medicine at the University of Pisa but his real interests were always in natural philosophy and mathematics and eventually he began to study these subjects. He failed to obtain a degree since he had difficulty accepting Aristotelian theories. After a spell of teaching mathematics privately in Florence, he was appointed to the Chair of Mathematics at the University of Pisa in 1589, where he remained for three remarkably productive years, laying the foundations of his studies of motion, particularly free fall. In 1592 he was appointed Professor of Mathematics at Padua, where he stayed for 18 years. Padua was one of the centers of Renaissance learning and so much more tolerant of 'new' ideas although there were a few strong advocates of Aristotelian ideas. Galileo became well-known and well-respected during his time in Padua and around 1600 he formed a relationship with Marina Gamba; she was to bear three children by him. Sometime during the first ten years in Padua it appears he invented the first instrument for actually measuring temperature. He knew about the Copernican theory of the solar system and by 1597 had become a 'Copernican' - he said so in a letter to Kepler - but he was being paid to teach Ptolemaic theory and so he didn't publicly admit his beliefs until 1604. In 1609 he heard about the spyglass, and realizing the importance of a telescope to a maritime power like Venice he built one of his own, which he showed to their Highnesses and the senate of Venice. Using his telescopes in 1609-1610 Galileo began to study various sky objects including:

He published his new discoveries in the Starry Messenger, which was dedicated to Grand Duke Cosimo of Tuscany. He moved back to Florence with his two daughters late in 1610 leaving Maria Gamba and his son in Padua. Before leaving Padua he was puzzled by Saturn, thinking that it had three moons, and determined that the Sun had spots on it. Soon after arriving in Florence he found that Venus had phases like the Moon, proving conclusively that Venus revolved around the Sun and not the Earth. Everything he observed seemed to contradict the earth-centered theory of Ptolemy and he was putting himself in serious danger with the Catholic Church. In fact, he sent coded messages and anagrams to colleagues informing them of his discoveries. He became involved in disputes with philosophers about Aristotelian ideas and these disputes, and his three Letters on Sunspots published in 1613, placed him in serious jeopardy. He became increasingly vulnerable to theologians because of his 'anti-clerical' and 'heretical' views and at the end of 1615 he felt he had to go to Rome to argue his case against Aristotle before various groups. His views were put to the theological qualifiers, whose recommendations of censure were put to the Cardinals of the Inquisition on February 24, 1616. Galileo was notified that he must not hold nor defend Copernican theory. If Galileo resisted, then he was to be warned not to 'hold, defend or teach' the propositions, lest the Inquisition proceed against him. It should be pointed out, however, because of future ramifications, that it was greatly disputed whether the word "teach" was specifically included. Galileo returned to Florence and continued to study the eclipses of Jupiter's moons. In 1623 he published The Assayer in which he outlined his scientific reasoning and contrasted it with what he called ... "the tiresome logical quibbles that seemed to satisfy philosophers."

Intermittently from 1624 Galileo wrote his Dialogue concerning two chief systems of the World, the Ptolemaic and Copernican, which he finished at the end of 1629. But, because of numerous delays due to difficulties of getting a license, first in Rome and then in Florence, the book wasn't published until February 1632. He had wanted to call it Dialogue of the Tides but the censors made him change it. Galileo didn't want to simply Œstate¹ his results as we do in publications today; he used conversations between three persons:

in indirect style, spread over a period of four days. The dialogue form was used for two reasons. Firstly, it was a particularly popular approach used to educate the public, and secondly, the author, Galileo, could detach himself from commitment to views that might be objectionable. The dialogue contained both the pro's and con's of the two theories and was written in Italian - the 'popular' language of the people - rather than Latin, the usual choice of scholars. Naturally, poor Simplicio was hopelessly 'out-gunned' and 'outmaneuvered' by the logic and the arguments of Salviati and Sagredo, and so on numerous occasions he had to agree with them about the Copernican system. Because Galileo had good 'connections' he managed to get the book through the censors, including the Pope, and when it finally appeared it received a tremendous amount of publicity.

However, the full wrath of the Church descended on him almost immediately and in August 1632 the Inquisition ordered all sales to stop, even though the book was licensed. He was accused of ridiculing Pope Urban VIII - who had suddenly changed his attitude because he realized that Galileo had placed the defense of the Aristotelian view in the mouth of a simpleton and also because he had been shown an unsigned memorandum from 1616 that forbade Galileo to teach Copernican idea's.

Despite being nearly 70 and in poor health Galileo was told to travel to Rome or be forcibly brought in chains. Due to bad weather and numerous delays along the road for quarantine because of the plague, he didn¹t arrive until February 1633. He was reexamined by the Inquisition starting on April 12, 1633. Galileo produced the signed affidavit from Bellarmine, based on the Cardinal's ruling, that only included the words '... not hold, nor defend ...' Copernican ideas. Since the memorandum in the Pope¹s possession with the word '... teach ...' in it was unsigned, Galileo could not be acquitted without damaging the reputation and authority of the Roman Inquisition. So it was privately arranged that he should admit to some wrong-doing with the understanding he would be treated leniently. Galileo acknowledged in writing that he had reread his Dialogue and agreed that in some places he had perhaps gone a little too far with some of his arguments but he denied any sinister intent. Subsequently, on June 22, 1633 he was forced to recant his views under a charge of 'vehement suspicion of heresy'. The book was placed on the Index of Prohibited books, where it remained for almost 200 years, although that could have hardly worried Galileo since there were so many copies in circulation that no Papal edict could make any difference. Still, expecting a light sentence, he was crushed by his condemnation to indefinite imprisonment. The Tuscan ambassador in Rome successfully contrived to have the sentence commuted to custody of the Archbishop Piccolomini of Siena, whose humanity and understanding literally saved Galileo's sanity and life.

After several months of house arrest with Piccolomini, he was allowed to return to his villa at Arcetri at the end of 1633 to live out the rest of his life in obscurity, albeit under the eyes of officers of the Inquisition¹s officers. Shortly after his arrival he suffered a serious hernia but was forbidden to seek help from doctors in Florence. Virginia, his daughter, who had entered a Franciscan convent, San Matteo, near Arcetri, taking the name Sister Maria Celeste, was chronically ill and in April 1634, about four months after Galileo's return to Arcetri, she died at the convent. Her death was a tragic blow to Galileo; his other daughter Livia and son Vincenzio were much less close to him, although Virginia had tried constantly to mitigate the difficulties between Galileo and her brother.

During his imprisonment several books were published attacking the Dialogue but, of course, he was not allowed to reply. He still worked with students and devoted himself to his final great work, Discourses concerning New Sciences that dealt with his theories of fracture and of motion, the book that many regard as his finest. It was completely anti-Aristotelian and he used the same three characters and style as before. The manuscript was completed in 1636 but because the Inquisition had banned all of his writings, the book was taken to Holland where it was published by Louis Elzevir in 1638. The arguments were again always convincing and Simplicio was often forced to admit as much.

Galileo's health was rapidly failing, he suffered bouts of asthma and he went blind in 1638 a devastating blow for some-one who had such a special talent for observation. Nearly helpless, he could only be visited by people who had been 'approved' by the Holy Office although he was allowed to visit his son during part of 1638 so he could consult with doctors. At the end of 1638 the restrictions were relaxed a little and a young scholar, Vincenzio Viviani, who later wrote the first biography of Galileo, moved into his villa. In 1641 he was joined by Evangelista Torricelli (1608-1647), who became eminent in his own right and is best remembered as the inventor of the barometer.

Galileo died on January 9, 1642, aged 77; the end of a truly remarkable life. He had been crushed by the verdict of the Inquisition of ...'vehement suspicion of heresy' ... because it cut him off from the Church he apparently loved but he died with a clear conscience. The Roman Church refused to relax its judgment of him and he was buried without any great ceremony or memorial. The year Galileo died, Isaac Newton was born. Whereas Galileo had discovered how things moved, Newton would go on to discover why.

I suppose that a great number of people when they hear the name of Newton, see figure 6, visualize a young man sitting under an apple tree in an English garden, deep in thought, when suddenly an apple falls and strikes the man on the head. Up he jumps, "That" he exclaims, "is an example of gravity!" The story is probably not true, of course, but Newton is best known for his theory of gravitation. In fact, there were many people a little later in his career who might have wished that it was an anvil that had fallen on his head rather than an apple! Newton was not a particularly pleasant man, he was a loner and never married, and his relations with other academics were notorious with a good of his later life spent embroiled in disputes. Even his loyal assistant at Cambridge, William Whiston said that

Nevertheless, his work on motion, optics and gravitation make him arguably the greatest scientist the world has ever known

Newton's life can be divided into three distinct periods; the first in his boyhood days from 1643 up to about 1665. The second period from 1665 to 1687 was the highly productive period, in which from 1669 he was Lucasian professor at Cambridge. The third period from the early 1690's, nearly as long as the other to combined, saw him as a highly paid government official in London with much less active interest in science and mathematics.

His father had died before he was born and when his mother remarried he was left in the care of his grandmother. When his step-father died in 1656 his mother removed him from school, where he had shown little promise in academic work. In fact, his school reports described him as "idle" and "inattentive". An uncle took charge and decided the young Newton should be prepared for university and in June 1661 he entered his uncle's old College at Cambridge figure 7, Trinity College, where his aim was get a degree in law. Instruction at Cambridge was dominated by Aristotelian philosophy but in the third year of the course much more freedom was allowed for independent study. Newton studied Descartes and became very interested in the new algebra and analytical geometry. He was also very much attracted to the mechanics of the Copernican astronomy of Galileo. Gradually his true talents began to emerge. As a result of the great plague, the university was closed in the summer of 1665 and he had to return home. There, in a period of less than two years, and when he was less than 25 years old, he began his revolutionary advances in mathematics, optics, physics and astronomy. While at home he laid the foundations for differential and integral calculus, several years before its independent discovery by Gottfried von Liebnitz. Using the calculus he produced simple analytical methods that unified many separate techniques previously developed to solve apparently unrelated problems such as finding areas, tangents, the lengths of curves and the maxima and minima of functions. However, his book about the calculus, or "method of fluxions" as he called it, which was completed in 1671 failed to get published and did not appear until much later. During this time he laid also the foundations for his theories of motion and gravitation. He returned to Cambridge after the plague and in 1669, Newton, then only 27 years old, succeeded Isaac Barrow as the Lucasian professor and he started his work on optics. Although most every scientist since Aristotle believed that white light was a single entity Newton, because he had observed chromatic aberration in telescopes - that is the coloring at the edges of images - thought otherwise. Indeed, by using a simple prism arrangement he showed that white light was made up of many colors that were bent at slightly different angles to form a continuous spectrum of colors (although dispersion, as this effect is called, had been written about by other in the 13th century). He thought that it would be impossible to correct for chromatic aberration in refracting telescopes, that is those with lenses, and so he designed and built he first reflecting telescope. In 1672 he donated a reflecting telescope to the Royal Society and was elected a Fellow of the Royal Society. That same year he published his first paper on light and color. Two influential scientists who had long spent time studying light, Robert Hooke and Christian Huygens objected to Newton's attempt to prove that light consisted of small particles rather than waves. His relations with Hooke deteriorated and he delayed publication of a full account of his researches on light in a book called Optics until Hooke's death in 1703.

His greatest achievement was his work in physics and celestial mechanics. As we saw above, in 1666 he had begun to formulate his three laws of motion and he had also discovered the law giving the centrifugal force on a body moving in a circular orbit. Newton's novel idea was to imagine that the Earth's gravity influenced the moon, through a centripetal (or center seeking) force. From his law of centripetal motion and Kepler's 3rd Law of planetary motion, Newton deduced the famous "inverse square law". In 1684, partially because many people were tiring of Robert Hooke's boasts, Newton was persuaded by Edmund Halley to write a full treatment of his new physics and its application to astronomy. In 1687 he duly published his Philosophiae Naturalis Principia Mathematica or the Principia as it is always known, see figure 8. In the opinion of many scientists, the Principia is the greatest scientific book ever written. In it Newton analyzed the motion of orbiting bodies, projectiles, pendulums and free-fall near the Earth. He further demonstrated the universal law of gravitation. He explained a wide range of previously unrelated phenomena including the orbits of comets, the tides, the precession of the Earth's axis, and the motion of the moon. After suffering a nervous breakdown in 1693 Newton essentially retired from research to take up a government position in London, becoming Warden of the Royal Mint (in 1696) and Master (in 1699). In 1703 he was elected president of the Royal Society and re-elected every year afterwards until his death in 1727. In 1705 he was knighted by Queen Anne, the first scientist to be so honored.

During the 18th and 19th centuries electricity and magnetism became the "hot" topics for study. Notable scientists were Benjamin Franklin who was one of the first to experiment with charges, Charles Coulomb who measured the force between electrical charges, Hans Oersted who showed that an electrical current gives rise to a magnetic field, André-Marie Ampère who derived the law connecting the two, and Michael Faraday who showed that a changing magnetic field produces an electrical current. In fact, you may recognize a number of these scientists because they have been honored by having "units" named after them.

It was apparent to many that there was therefore a close connection between electricity and magnetism but it was James Clerk Maxwell, see figure 9, who actually unified the two. Richard Feynman once said

Maxwell's work is not that well known by non-scientists because it was entirely theoretical but he showed that four relatively simple mathematical equations could express the behavior of electric and magnetic fields and their interrelation. These four equations, now known as Maxwell's equations, first appeared in 1873. His equations yielded the astonishing result that charges that were accelerating give off radiation and this radiation is in the form of waves consisting of electric and magnetic fields traveling together. When he calculated the speed of the radiation he found that it was the same as the speed of light. So he had shown that light was an electromagnetic wave. Similarly, radio waves, TV waves, microwaves, infra-red radiation, ultra-violet light, x-rays and g-rays are all electromagnetic waves (that travel with the same velocity, the speed of light). The only difference is their frequencies and wavelengths, for example:

No historical review of physics would be complete without mentioning the contributions from Einstein and Schrödinger. Albert Einstein (1879-1955), see figure 10, had his "finger" in many scientific pies. He was born in Ulm, Germany but in 1894 he decided officially to relinquish his German citizenship in favor of Swiss. He had a relatively inauspicious start to his career - in 1895 he failed an examination that would have allowed him to study for a diploma as an electrical engineer in Zurich. After attending secondary school at Aarau he returned to the Zurich Polytechnic and eventually graduated in 1900 as a secondary school teacher of mathematics and physics. Between 1902 and 1909 worked in the patent office in Bern, Switzerland. He earned a doctorate from the University of Zurich in 1905 and in 1908 he became a lecturer at the University of Bern. In 1909 he became a professor of physics at the University of Zurich. So when he left the patent office in 1909 he had earned the reputation as a leading scientific thinker. He went on to hold Chairs in Prague and Zurich and in 1914 he took a position at the Kaiser-Wilhelm Gesellschaft in Berlin; it is interesting to note that from that time on he never taught a university course! In 1933 he left his post in Berlin to take a research position at the Institute for Advanced Study at Princeton, where he remained until his death.

While working in the patent office at Bern, he completed an amazing range of theoretical physics publications, written in his spare time without the benefit of close contact with scientific literature or colleagues. Let me give you just three examples all published in 1905. For example:

Einstein sought to extend special relativity to phenomena involving acceleration; the key appeared occurred in 1907 with the principle of equivalence in which puts forward the idea that gravitational acceleration is completely indistinguishable from acceleration caused by mechanical forces. Then in 1911 he made some preliminary predictions about how a ray of light from a distant star, passing near the sun would appear to be bent slightly in the direction of the sun. In 1912 he began a new phase of research involving gravitation and late in 1915, after a number of "false starts" the definitive version of the general theory of relativity appeared. When British eclipse expeditions in 1919 confirmed his predictions of the bending of light he was idolized in the popular press. He received the Nobel Prize in 1921 not for his work on relativity - which still hadn't been universally accepted - but for his work on the photoelectric effect, which I referred to earlier.

In 1924 Louis de Broglie, see figure 11, published his Ph.D thesis which was concerned with what was called wave/particle duality, i.e., the idea that matter has the properties of both waves and particles. In particular, he put forward the theory of electrons being waves ... an idea that was confirmed by experiments in 1927. After reading the thesis, Erwin Schrödinger, see figure 12, had the idea to describe the electrons orbiting around the nucleus of an atom in terms of these waves ... he developed a completely new subject we now call wave mechanics. In 1933 Schrödinger received the Nobel Prize for this work. Some people describe wave mechanics as yet a further abstraction from common sense. Conceptually it is probably the most difficult subject to come to terms with and debates about what it all means continues among natural philosophers to this day! Even Einstein was unable, at first, to accept it. Be that as it may, wave mechanics, using Schrödinger's equations, now forms the basis for most of our current understanding of the properties of electrons in atoms and solids ... a subject very close to my own research interests.

Schrödinger left Germany in 1933 in disgust over politics and moved to Oxford University. Although not exactly handsome, he certainly had a way with the ladies! He had a highly unusual family arrangement ... when he moved to Oxford he took with him his wife Anny and his mistress Hilde, and they all lived together. Schrödinger considered Hilde, who was expecting his baby, a second wife. He had a most unhappy time at Oxford since the university society was distinctly misogynist; Fellows and Dons much preferred 'male company'. In fact, when Schrödinger's appointment came up for renewal one highly renowned member of the university said:

Schrödinger moved to Ireland within a year, helped to set up a top-rated Institute for Theoretical Studies in Dublin, and spent most of the rest of his life there. Despite his highly questionable morals there is no doubt that he was a supremely gifted scientist ... I admire him so much I named one of my cats after him!

Richard Feynman (1918-1988), see figure 13, anti-establishment figure, raconteur, bon-vivant, painter, bongo-player - who once wrote an opera backed by drums - was an original and brilliant researcher and much-adored teacher. He studied at MIT and received his doctorate at Princeton in 1942. In his research he replaced Maxwell's wave model of electromagnetism with a model based on particle interactions. In 1941-42 he worked on the atomic bomb project at Princeton and then from 1943-45 at Los Alamos. After the war he was appointed Chair of Theoretical Physics at Cornell and then, in 1950, to the Chair of Theoretical Physics at Caltech, where he remained for the rest of his career. Feynman's main contribution to science was to quantum mechanics. He introduced special diagrams - now called Feynman Diagrams, see figure 14 - as pictures of the mathematical expressions describing the interaction between particles. For his work on 'quantum electrodynamics' (QED) he was awarded the Nobel Prize in 1965, jointly with Schwinger and Tomanaga. Several very popular books have been published stemming from his lectures at Caltech - the so-called Feynman lectures - and through his collaborations with Robert Leighton.

Stephen Hawking (1942- ), see figure 15, is one of the more well-known of today's scientists, most likely because he has not let ALS (or Lou Gehrig's disease) stand in the way of an outstanding contribution to our understanding of the universe and black holes, and because of several popular books he has published on cosmology. He graduated from Oxford and then went on to study cosmology at Cambridge. After obtaining his doctorate he continued research at Cambridge on black holes and discovered that they emit radiation. At the age of thirty-two he became a Fellow of the Royal Society and the Lucasian Professor of Mathematics at Cambridge [2]. Confined for a number of years in a wheelchair he now speaks with the aid of a special 'computer'. Despite his tremendous handicaps, Hawking is considered one of the leading scientists on today.

I know that I have not mentioned many important discoveries nor talked about some very famous work of other scientists, such as James Joule, Thomas Young, the Curie's, Henri Becquerel, Wilhelm Röntgen, J.J. Thomson and Max Planck. During this course we will take a close look at some of the important discoveries that these scientists have made.

FOOTNOTES

[1] Galileo's telescopes comprised two lenses also; however, the lenses were of different types, one convex (the objective) and one concave (the eyepiece).

[2] The Chair was founded in 1661 with money left in the will of the Reverend Henry Lucas, who had been a Member of Parliament for the University. It was first held by Isaac Barrow and later, in 1663, by Isaac Newton.

REFERENCES

I have made use of many texts, certainly too numerous to mention, but the main sources have been:

George Sarton, Ancient Science through the Golden Age of Greece (Dover Publications, Inc., New York). This is a remarkable little book and I have used a good deal of material from it.

I have also used material from many Web-sites including the following (and they are all worth visiting):

Biographies and historical topics:

The Galileo Project Homepage and Ptolemaic system: