Category Great Personalities

You might have come across laser pointers while attending a seminar or conference, or perhaps used it to play with your cat or dog. In the sixty years since physicists demonstrated the first laboratory prototype of a laser in 1960, it has been put to use in numerous ways from barcode readers to systems for hair removal.

The technology behind laser devices is based on Einstein’s Theory of Stimulated Emission. This theory came a year after the discovery of general relativity. Einstein imagined a bunch of atoms bathed in light. He had earlier discovered that atoms sitting in their lowest energy state can absorb photons and jump to a higher energy state. Similarly, higher energy atoms can emit photons and fall back to lower energies.

After sufficient time passes, the system attains equilibrium. Based on this assumption, he developed an equation that can be used to calculate what the radiation from such a system would look like. Unfortunately, Einstein’s calculations differed from the laboratory results. It was obvious that a key piece of the whole puzzle was missing.

Einstein resolved this by guessing that photons like to march in step. This would mean that the presence of a bunch of photons going in the same direction will increase the probability of a high-energy atom emitting another photon in that direction. Einstein labelled this process stimulated emission. He was able to rectify the disparity between his calculations and the observations by including this in his equations.

A laser is a device to harness this phenomenon. It excites a bunch of atoms with light or electrical energy. The photons released as a result are channelled precisely in one direction. Lasers are used in delicate surgery or industrial processes that require precision.

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Wall Street in New York is the home of the New York Stock Exchange. An army of mathematicians are employed there to analyze and predict the stock price variations. Their employers can potentially earn millions of dollars based on their predictions about which way the prices will jump.

Mathematicians however say that stock markets follow a random walk. This means that unless some spectacular event occurs, the prices have the same chances of decreasing and increasing at the end of any day. If patterns do exist, they will be elusive and difficult to find, which is why financial mathematicians are paid huge sums.

Some of the intricate mathematics used for stock market analyses can be traced back to Einstein. He developed the fluctuation-dissipation   theorem to explain the random movement of particles found in liquids or gases.

This movement called ‘Brownian motion’ was first observed by the Scottish biologist Robert Brown. Brownian motion is highly similar to the price fluctuations seen in stock markets. The similarity was observed in 1970 and since then it has been used on Wall Street. Einstein’s paper on Brownian motion is still used as the basis for certain stock market predictions.

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Einstein’s General Theory of Relativity has predominantly found applications in astronomy through gravity waves, big bangs and black holes. One of its rather unexpected applications was in the multi-billion-dollar industry centred around the Global Positioning System (GPS).

All GPS navigators including Google Maps work by measuring the distance from one point on Earth to one of the satellites orbiting our planet. Though GPS was originally developed with military use in mind, it has since become an inherent part of everyday life.

GPS is based on a collection of 24 satellites, each carrying a precise atomic clock. A hand-held GPS receiver which detects radio emissions from any satellite overhead can find the latitude, longitude and altitude with accuracy up to 15 metres and local time to 50 billionths of a second. The clocks on satellites are ahead of those on Earth by 38,000 nanoseconds. The reason for this is explained by the General Theory of Relativity. Though it may appear as an inconsequential amount of time, if these nanoseconds are not taken into account, GPS systems would be highly inaccurate.

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Einstein received a paper from Indian scientist Satyendra Nath Bose in 1924. The paper was on a new perspective: to think of light as a gas filled with indistinguishable particles. Einstein recognized the relevance of the paper. He translated it to German and submitted it on behalf of Bose to the famous journal Zeitschrift fur Physik. Bose went to Europe and worked with Einstein at the X-ray and crystallography laboratories there.

Einstein worked with Bose to extend his idea to atoms and they predicted a new state of matter which came to be called the Bose-Einstein Condensate. A Bose-Einstein Condensate is a dense collection of particles with integer spin known as Bosons.

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Einstein was primarily in pursuit of a universal field theory after the General Theory of Relativity. He engaged in a series of unsuccessful attempts to further generalize the theory of gravitation in order to unify and simplify the fundamental laws of physics, in particular, gravitation and electromagnetism.

This ‘theory of everything’ was supposed to refute the quantum theory. Though he published a paper in 1929 which supposedly had such a theory, Einstein himself had to acknowledge the errors in his argument.

Einstein remained in the cocoon of his research, largely ignoring other developments in physics and quantum theory. He however, did a few collaborations with the Indian scientist Satyendra Nath Bose, the Austrian Erwin Schrodinger and his Hungarian former student Leo Szilard.

In the 1930s he worked together with Russian physicist Boris Podolsky and the Israeli physicist Nathan Rosen. Nevertheless, his search for the ‘theory of everything’ and his distrust of the quantum theory consumed him in his later years.

Einstein had also made contributions to the development of the quantum theory. The concept of light quanta (photons) was used by him in 1905 to explain the Photoelectric Effect and to develop the quantum theory of specific heat.

Despite playing a main role in its development, Einstein regarded the quantum theory only as a temporarily useful structure.

His efforts were primarily in formulating the unified field theory which he believed would turn out to be the reason behind quantization of energy and charge. He felt that the quantum theory lacked the simplicity and beauty befitting a rational interpretation of the universe.

He engaged in a series of private debates with physicist Niels Bohr about the validity of the quantum theory later on. The 1920s witnessed his prolonged public debates with Niels Bohr and Werner Heisenberg over quantum mechanics. Einstein was rather lukewarm about the quantum theory even from a philosophical standpoint, saying in 1926 that he was convinced God does not throw dice. However, Bohr showed the ambiguities in Einstein’s reasoning.

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The Nobel Prize in Physics 1921 was awarded to Albert Einstein “for his services to Theoretical Physics, and especially for his discovery of the law of the photoelectric effect.”

Albert Einstein received his Nobel Prize one year later, in 1922. During the selection process in 1921, the Nobel Committee for Physics decided that none of the year’s nominations met the criteria as outlined in the will of Alfred Nobel. According to the Nobel Foundation’s statutes, the Nobel Prize can in such a case be reserved until the following year, and this statute was then applied. Albert Einstein therefore received his Nobel Prize for 1921 one year later, in 1922.

However, Einstein did not attend his prize giving. Though he was informed that he was to receive the prize, he continued with a lecture tour of Japan.

Einstein has published four papers on the general theory of relativity. In the third paper, he used general relativity to explain why Mercury’s closest point to the Sun (its perihelion) is erratic.

Gravitational influence of the Sun and other planets was not sufficient explanation for this movement. Some even went as far as to suggest in the 19th century that a new planet, Vulcan, orbiting close to the Sun was the reason! But this was disproved as Einstein succeeded in calculating the shift in Mercury’s perihelion using the general theory of relativity.

The theory not only explained previously unexplained phenomena, it could even predict events that have not occurred yet. In 1919, the theory was validated again when Sir Arthur Eddington, secretary of the Royal Astronomical Society of London travelled to the island of Principe off the coast of West Africa. There, he had the perfect view of the Sun during a total eclipse.

The light emitted from a certain strand was measured and it was found that the light was deflected, or bent, by just the amount that Einstein had predicted. Einstein’s fame skyrocketed after this.

The General Theory of Relativity predicted that the space-time around Earth would be warped and twisted due to Earth’s rotation. The theory gave a new framework for all of physics and proposed new concepts of space and time.

In 1907, Einstein had certain realizations about his theory. He understood that special relativity could not be applied to gravity or to an object undergoing acceleration. Consider a person sitting inside a closed room on Earth. That person experiences Earth’s gravity. Now imagine if the same room was placed in space, away from the gravitational influence of any object.

If it is given an acceleration of 9.8 m/s2 (same as Earth’s gravitational acceleration), the person inside the room won’t be able to tell whether he is feeling gravity or uniform acceleration. This idea laid the foundation of the General Theory of Relativity.

Einstein’s next question was how light would behave in the accelerating room. When we shine a torch across the room, the light looks like it is bending forward. This is because the floor of the room would be coming up to the light beam at an ever-faster speed, so the floor could catch up with the light. As gravity and acceleration are equivalent, light would bend in a gravitational field.

It took Einstein several years to find the correct mathematical expression of these ideas. In 1912, his friend, mathematician Marcel Grossman, introduced him to the tensor analysis of some mathematicians. This helped him. After three more years of work, the foundations of this theory were laid in the four papers he published in 1915.

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Einstein was not the first scientist to observe and study the photoelectric effect. However, he was the first to properly understand the nature of light and draw the correct assumptions from it. Physicists James Clerk Maxwell in Scotland and Hendrik Lorentz in the Netherlands had already proved the wave nature of light in the late 1800s. This was proven by seeing how light waves demonstrate interference, diffraction and scattering- which are common to all waves including water.

Einstein’s 1905 argument that light behaves as sets of particles (initially called quanta and later ‘photon’) was contradictory to the classical description of light as a wave. A completely new model of light was needed to explain the phenomenon. Einstein developed a model for this purpose and according to this, light sometimes behaved as particles of electromagnetic energy or photons. Though others had presented this theory before Einstein, he was the first to explain why it occurred and consider its potential.

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Photoelectric effect is the emission of electrons from a substance when electromagnetic radiations fall on it. For instance, when light falls on a metal plate, electrons are ejected.

Light with energy above a particular point frees electrons from the surface of the solid metal. Each photon (particle of light) collides with an electron and uses some of its energy to remove the electron. Photon’s remaining energy transfers to the free negative charge which is called a photoelectron. This was a discovery that revolutionized modern physics as it clarified many doubts regarding the nature of light.

The photoelectric effect proposed by Einstein in 1905 remains valuable in various areas of research such as material science and astrophysics. It is also the basis of many useful devices. The ‘electric eye’ door openers, light metres used in photography, solar panels and Photostat copying are all applications of the photoelectric effect.

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The equation E=mc2 is perhaps one of the most famous scientific equations of all time. As mentioned previously, this equation came up in the fourth paper Einstein published in 1905. It states that energy is equal to the product of mass and the square of the speed of light. Which means that, matter can transform into energy if it moves fast enough.

One of the factors making this equation so remarkable is that it establishes a connection between hitherto seemingly unrelated entities. Before Einstein’s fourth paper was published, time and Space, and mass and energy were separate entities.

Through establishing the concepts of space-time and E=mc2, he formulated his theory of relativity. Though special relativity is one of the last intuitive theories ever made in the history of science, it turned out to be a crucial one for physics.

Scientists proved all the theories Einstein proposed in 1905. The uses of these theories did not always turn out to be for the benefit of mankind. Changing matter into energy is the principle behind the generation of nuclear energy which provides electricity to millions of people.

However, the same principle was used to split atoms and release the destructive energy of atom bombs. Thus, the equation which is a blessing in electricity production and medical diagnostic tools also became the foundation of the nuclear bomb.

The Special Theory of Relativity was published in 1905. It presented the astonishing idea that space and time are not absolute but relative. Or simply put, changes in the measurements of distance and passing of time depends on the observer who is measuring them. Einstein added a fourth dimension (time) to the three existing dimensions (length, width and height).

Einstein revealed that time is experienced differently by observers in relative motion. Two events might appear as if they are happening at the same time for one observer, but they might happen at different times from the perspective of another. And the observers would be right in both cases.

Einstein later demonstrated this point with an experiment. Imagine a man standing on a railway platform as a train goes by. Each end of the train is struck by a bolt of lightning just as the midpoint of the train passes him. Because the lightning strikes are the same distance from the observer, their light reaches his eye at the same instant. Therefore, he would correctly say that they happened at the same time.

Meanwhile, there is an observer sitting in the exact midpoint of the train. From her perspective, the light from the two strikes also has to travel equal distances. She will therefore measure the speed of light to be the same in either direction.

However, as the train is moving, light from the lighting that struck the rear must travel more to catch up and will be slower to reach than the light from the front. This causes the observer inside the train to conclude that lightning struck the front of the train first rather than simultaneously. Einstein says that simultaneity is relative.

These new ideas were published in a paper titled On the Electrodynamics of Moving Bodies.

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Einstein too had an annus mirabilis like Newton. In 1905, Einstein published four scientific papers in the German journal Annalen der Physik. These four papers laid the foundation of modern physics by revolutionizing how the scientific community perceived fundamental concepts of space, time, mass, and energy. As all four papers were published in 1905, this year is considered Einstein’s annus mirabilis or miracle year.

The first paper introduced the revolutionary idea that light is composed of both energy and particles. The foundation for quantum physics that physical systems can behave both as waves (energy) and as particles (matter) began here.

The second paper, though without any revolutionary concepts, was important in its own right. Einstein discovered the empirical evidence behind Brownian Motion which refers to the random movement displayed by small particles that are suspended in fluids. Though many scientists had accepted this already, empirical evidence had been lacking.

The third paper which contained the special theory of relativity possibly had the most ground-breaking content among all four papers.

The last of these papers published on 21 November 1905 had the mathematical confirmation of the Special Theory of Relativity, the most famous equation: E=mc2.

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Albert Einstein is considered to be one of the most influential persons of the 20th century. His thoughts on space, time, motion and energy revealed new trajectories to the world.

Astronomers use his work till day to study everything from gravitational waves to Mercury’s orbit. His contribution also extends to the philosophy of science.

Einstein’s formula on mass – energy equivalence, E=mc2(square) has been called the world’s most famous equation. Even those unfamiliar with the underlying physics know about this equation.

In 1921 he was awarded the Nobel Prize in Physics for the law of the photoelectric effect. His theory of general relativity gives an explanation of gravity while the law of photoelectric effect explains the behaviour of electrons in certain conditions.

Einstein’s theories and discoveries marked a turning point in the development of quantum theory and influenced the development of atomic energy.

The ‘theory of everything’ was a single theory under which Einstein tried to unify all the forces of the universe. He worked on this unified field theory, though unsuccessfully, till the time of his death.

Einstein’s insight and inquisitiveness made him the most influential physicist of the 20th century.

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Newton’s contributions to science are truly staggering. In a foreword to a twentieth century edition of Newtons Opticks, Albert Einstein wrote:

“Nature was to him an open book, whose letters he could read without effort… In one person, he combined the experimenter, the theorist, the mechanic and, not least, the artist in exposition. He stands before us strong, certain and alone; his joy in creation and his minute precision are evident in every word and every figure.”

Newton summarized his achievements in these words: “I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the seashore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, whilst the great ocean of truth lay all undiscovered before me…”

Sir Isaac Newton led an active life until his old age when age-related afflictions became a barrier. As he experienced inconsistencies due to weakness in the bladder, he was forced to limit his movements and follow dietary restrictions.

He became ill with gout in 1725 and suffered haemorrhoids the next year. In the months prior to his death, Newton was ill and bedridden. He lost consciousness on 19 March 1727 due to pain from his bladder stone and never regained consciousness. Newton passed away on 31 March 1727 at the age of 84. He was buried in London’s Westminster Abbey on April 4, to rest among the kings and queens, dukes and earls of England.

Isaac Newton’s pallbearers included two dukes, three earls and the Lord Chancellor. Voltaire described Newton’s funeral as the funeral of a king who had done well by his subjects.

In the last years of his life, Newton’s circle of friends included Prince George (later George II) and his wife Caroline, whom he visited regularly. He was successful, famous and wealthy by the time he died. Newton is said to have helped his extended family generously and was a charitable person. As he had never married, his estate went to the descendants of his stepfather, Barnabas Smith.

His papers were given to his half-niece Catherine Barton and her husband John Conduitt.

Alchemy is a proto-science which studies, among other things, the possible methods to transform base metals such as lead and copper into silver or gold. Alchemy also involves the search for the cure for diseases and a way to extend life.

Alchemy is shrouded in mystery and secrecy. Newton has been considered as a credulous alchemist by many. He had even described a recipe for the Philosopher’s Stone in one of his manuscripts. Philosopher’s Stone is said to have the ability to turn base metals into silver and gold and had magical properties and could even help humans achieve immortality.

Newton’s belief that he had discovered a blueprint for the Philosopher’s Stone was rather surprising, considering his status as a serious and empirical scientist.

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Despite his success as a scientist, Newton was at first largely inactive in the political arena. Later, he became the Member of Parliament, representing Cambridge University from 1689 to 1690. This had been the period when the Parliament enacted the Bill of Rights, which limited the power of the monarchy and laid out the rights of Parliament and individuals. However, Newton was anything but an active parliamentarian. He reportedly spoke just once and that had been to ask an usher to close a window on a chilly day!

Despite his lacklustre contributions as a parliamentarian, he became acquainted with many influential individuals including King William III and philosopher John Locke, during his time in London. Newton served a second term in the parliament from 1701 to 1702 but this time too his participation in the proceedings of Parliament was minimal.

In 1705, he was knighted by Queen Anne for his contributions to science and public service. The event was held at a lavish ceremony at Trinity College. Newton became the first scientist to be given this honour.

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Among all the duties Newton had at the Royal Mint, the most impossible one was testing the purity and accuracy of coins. The coins had to be of the correct weight and fineness, with only the least difference from each other.

The task of determining whether each coin was identical to the other, turned out to be a tedious one. However, Newton’s scientific training came in useful to tackle this job.

Newton visited the pressing plant next to his office at the Royal Mint every day. Workmen would take out a small sample of the molten metal using ladles designed for this purpose. The sample would be taken back to the warden’s laboratory where he conducted chemical experiments on the metal to verify if it met the required standards of purity.

Newton claimed that he had brought the coinage to a much greater degree of exactness than ever before. Naturally, he reacted angrily when a judgment by the jury in the Trial of the Pyx in 1710 declared that the gold coins were substandard. (The Trial of the Pyx is a procedure in which the integrity of the coinage of England was tested.)

Isaac Newton was appointed as the warden of the Royal Mint in 1696. He received the position on the recommendation of Charles Montague, a well-known politician of the time. The prestigious post was intended as a reward for Newton’s scientific achievements.

Newton took up the position at a crucial time as England was in the process of changing its silver coinage prevalent from the time of Elizabeth I. As these coins had a smooth edge, people could easily clip small amounts of silver from them and still use the same coin. Making counterfeit coins was also a common occurrence. Newton took a firm stance on counterfeiting. He cracked down on the group of thieves known as clippers who clipped off small pieces of coins, melted down the metal and extracted the silver.

Under Newton’s wardenship, auxiliary mints were set up on different parts of the country. He supervised the processing of new coins and its distribution to various banks across the country. Newton was so successful that in 1699, within 3 years of his appointment, he was made the Master of the Royal Mint.

Isaac Newton became the president of the Royal Society in 1703. The 60-year-old Newton undertook responsibilities with his characteristic determination and energy. In the preceding years the Society had a series of politicians as its presidents. They were not concerned about the Society’s aims and the weekly meetings were no longer based on the scientific interests which laid the foundation of the Society.

Once Newton took charge, he devoted his time to bring the Society back to its old grandeur. He developed a scheme and methodology for conducting its meetings. According to the scheme, weekly meetings would have to be held, where serious discussions would take place. Moreover, he also made a provision for people with good scientific reputations to give demonstrations at the meetings. This succeeded in increasing the attendance and improving the quality of the deliberations.

The Royal Society became stronger during and following the 24 years of Newton’s presidentship. He played a significant role in making the Society into the world-famous organization it is today. However, Newton is also said to have exploited his position as the president to make public his disagreements with scientists such as John Flamsteed, the astronomer.

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Newton was invited to join the Royal Society in early 1672. The Society had distinguished personalities such as Robert Boyle and Christopher Wren as its members at the time. Newton had seen the invitation to join as a great honour.

He found a rival of his rank at the Society. It was Robert Hooke, who had been a member of the Royal Society right from its start. Hooke was a brilliant and inventive man whose mind moved from discipline to discipline, making discovery after discovery.

Though Hooke was mainly interested in mechanics, he built amazing microscopes and researched the structure of the plant cell. He was also a gifted inventor who created dozens of devices ranging from an early form of the telegraph to a diving bell.

He had also ventured into the study of combustion, musical notes and the nature of light, the last of which became the bone of contention between Hooke and Newton. The conflict between the duo began with conflicting opinions about the nature of white light. Newton presented his first paper to the Royal Society in February 1672, in which he detailed his work on the nature of light and advanced his theory that white light was a composite of all the colours of the spectrum. Newton asserted that light was composed of particles.

Hooke had his own ideas about the nature of light. He believed that light travelled in waves, in contradiction to Newton’s belief. Hooke was critical of Newton’s paper.

He went on to attack Newton’s methodology and conclusions. Hooke was certainly not the only person to take a critical stand. Huygens, the great Danish scientist and a number of French Jesuits also raised objections. However, due to his work in the same field and prominence within the society, Hooke’s remarks were the most cutting.

Newton responded to the criticism by being angry and defensive. This came to be his characteristic response to any critique of his work.

The Royal Society was the leading national organization for the promotion of scientific research in Britain. It is also the oldest national scientific society in the world.

The origin of the society can be traced back to November 28, 1660, when twelve men met. They decided to set up a College for promoting ‘Physico-Mathematicall Experimentall Learning’. These men included scientist Robert Boyle, architect Christopher Wren, Bishop John Wilkins and the courtiers Sir Robert Moray and William, 2nd Viscount Brouncker.

Brouncker went on to become the first president of the Royal Society. King Charles II granted a royal charter for it as ‘The Royal Society’. Through the royal charter the society got an institutional structure- a president, treasurer, secretaries, and council. The society has always remained a voluntary organization, independent of the British state despite receiving royal patronage from the beginning.

The conduct and communication of science was revolutionized by the Society. In 1665 itself, Hooke’s Micrographia and the first issue of Philosophical Transactions were published. Philosophical Transactions is now the oldest continuously-published science journal in the world.

The Royal Society also published Isaac Newton’s Principia Mathematica, and Benjamin Franklin’s kite experiment demonstrating the electrical nature of lightning.

Newton was a mathematics professor at Trinity College, Cambridge. But he was not a successful teacher. Newton preferred to spend his time alone in the laboratory, which he built himself, or in the small garden outside his rooms.

Only a few students attended his classes and fewer still understood what he said. A secretary later commented that often, Newton ended up teaching his walls with no students in front of him!

Not even one student who studied mathematics under Newton in the thirty years of his teaching career dedicated himself to the study of mathematics.

Newton’s absent-mindedness was also well known. He would sometimes stay in bed an entire day pondering upon a particular problem. If he received visitors while he was immersed in a new idea, Newton would simply walk into another room to continue thinking; completely forgetting that somebody was awaiting him in the other room.

By the 1670s, Trinity College became a lonely place for him. He enjoyed the brotherhood of similar minds and hence, he eagerly accepted the offer to join the Royal Society.

The English version of Opticks: or A Treatise of the Reflexions, Refractions, Inflexions and Colours of Light was published in 1704. A Latin translation of the book appeared in 1706. This is Newton’s second major book on physical science. It analyses the fundamental nature of light.

The book covers discoveries and theories concerning light and colour made by Newton in 33 years. It deals with ideas ranging from the spectrum of sunlight to the invention of the reflecting telescope. It also includes the first workable theory of the rainbow and the first colour circle in the history of colour theory. Newton also discusses various other subjects such as metabolism, blood circulation and a study of the haunting experiences of the mentally ill.

One of the major impacts of Opticks was that it overthrew the idea that ‘pure’ light (such as sunlight) is white or colourless, and it becomes coloured by mixing with darkness caused by interactions with matter. Newton showed that this assumption from the time of Aristotle and Theophrastus was wrong.

Newton also illustrated that colour is a result of the physical property of light, as each hue is refracted at a characteristic angle by a prism or lens. He also added that colour is a sensation within the mind and not an inherent property of material objects or of light itself. Considering the impact of the book on science, it is astonishing to think that it was initially published anonymously with just the initials I.N. at the end of an advertisement at the front of the book.

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Astronomer Edmond Halley persuaded Newton to expand his studies. Halley was the driving force behind the publication. He acted as a critic as well as supporter for this work.

Edmond Halley even convinced Newton to allow him to edit the Principia. Halley covered the various expenses, corrected the proofs himself, and ultimately got Philosophiae Naturalis Principia Mathematica printed in 1687.

Newton was famously reluctant to publish his works. Without Edmond Halley’s compulsion to publish Principia, Newton may have never become an outstanding figure in the history of science.

Newton would probably be known only for his mathematics and optics, and remain a relatively obscure professor in Cambridge.

Philosophiae Naturalis Principia Mathematica (Latin for Mathematical Principles of Natural Philosophy) is often simply referred to as Principia. This work in three books, written by Isaac Newton in Latin was first published on 5 July 1687. In retrospect, its publication was a landmark event in the development of modern physics and astronomy.

Newton published two more editions in 1713 and 1726 after annotating and correcting his personal copy of the first edition. Principia contains the laws of motion, law of universal gravitation and a derivation of Kepler’s laws of planetary motion (Kepler originally obtained these empirically). The work also forms the foundation of classical mechanics. Principia is considered as one of the most important works in the history of science.

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The significance of the Newtonian reflector does not lie in the discovery of new celestial bodies or celestial phenomena. Newton neither discovered the moons around Jupiter like Galileo nor did he plot the return of a comet – like Halley. However, the Newtonian reflector and Newton’s theory of universal gravitation made an invaluable contribution: they tied together Mathematics, Astronomy, and our understanding of the universe.

He mathematically established that gravitation was a two-way operation. While the Earth pulled on a falling apple, the apple too pulled on Earth. This was seen, calculated and confirmed in the motions of heavenly bodies. It was made possible by the science of the reflector telescopes which can be credited to Newton. The work of Copernicus and Galileo were carried through by Newton and his telescope.

While it is commonly assumed that Newton invented the first reflector telescope, claims to the contrary are also there. The Italian monk Niccolo Zucchi claimed to have experimented with the idea as far back as 1616. It is possible that Newton read James Gregory’s 1663 book Optica Promota which contained designs for a reflecting telescope using mirrors. Gregory had been trying to build such a telescope, but he did not succeed. Ultimately, Newton’s telescope was the one that worked well and brought reflectors to the scientific world.

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The first successful practical reflecting telescope was built by Newton. Until then telescopes were large unwieldy instruments. The design of the telescope was recast by Newton on the basis of his theory of optics. He used mirrors instead of lenses and the result was a new telescope 10 times smaller than the traditional ones.

Earlier also many efforts were made to make more powerful telescopes using larger lenses. They were unsuccessful as the lens kept producing coloured rainbows around bright objects like the Moon and the planets. The coloured fringes formed due to the unequal refraction of colours by the lens were unavoidable in simple telescopes.

Newton was under the assumption that no lens could rectify this issue. Though this was a mistaken assumption, it led him to use a mirror to form an image and thereby to build a reflecting telescope. This is now called the Newtonian reflector. A curved mirror brings rays of light to a focus and forms an image by reflection (whereas a lens does it by bending or refraction). Some of the largest telescopes used today are based on the telescope made by Newton in 1668.

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The laws of motion are applicable even in outer space. Newton’s Second Law states that force is needed to increase or decrease the speed of a body. This implies that astronauts must learn to push themselves through their spacecraft, or else they will float around helplessly. They also need to remember to stop themselves as they near their destination or else they’ll keep moving till they hit something.

During their first attempt, astronauts usually end up a little worse for the wear after stumbling around the spacecraft. Unlike humans, animals flown to space often fail to learn this. A set of new-born quails aboard Russia’s Mir space station couldn’t adapt to life in space and died in a few days. Newton’s Third Law too has application for astronauts. The law states that for every action, there is an equal and opposite reaction. While turning a screw, astronauts have to anchor themselves to a wall, or else they’ll be the ones twisting. Even the mildest action like typing at a computer keyboard will send an astronaut floating away. To remedy this problem, workstation on the international space station has restraining loops for the crew to anchor their feet.

Though it may seem like the laws of motion are different in space and on Earth that is not the case. The overwhelming force of Earth’s gravitational field simply masks its exact effects. Gravity plays an astonishing part in many phenomena we take for granted. For instance, hot air (which is lighter than cool air) rises, and a convection current is formed which enables natural air circulation in our houses. In space however, nothing is lighter than anything else and ordinary convection currents do not exist. Thus, to make sure that the astronauts don’t suffocate due to carbon dioxide accumulation, a ventilation fan is installed to facilitate air circulation.

The International Space Station is a perfect example of the laws of motion. Though intuition and common-sense points otherwise, Newton realized that a bullet shot from a gun should continue to move indefinitely. On Earth, atmospheric friction slows the projectile while gravitational force pulls it to the ground. But the faster the bullet is shot, the farther it will travel before falling. And if you can manage to shoot something at a speed of around 11.2 km/s, it will never finish its trajectory. It will instead orbit the Earth in a state of perpetual free fall. This particular velocity (11.2 km/s) cancels the pull of Earth’s gravity and is used to launch spacecraft.

Even fire is not exempt from the laws of motion in space. Behaviour of weightless flames is rather different from those on Earth. However, such a fire is best limited to the lab as fire aboard a spacecraft can have catastrophic effects.

The sizes of rockets range from small fireworks used by ordinary people to massive Saturn Vs that once carried payloads toward the Moon. Newton’s third law of motion explains the propulsion of all rockets, jet engines, deflating balloons, and even the movement of squids and octopuses.

The engines of rockets need to overcome both the pull of gravity and the inertia of the rocket as stated in the first law. According to Newton’s Third Law, “every action has an equal and opposite reaction”. A rocket is pushed forward by the push of the burning fuel at its front. This also creates an equal and opposite push on the exhaust gas backwards.

Once they’re in motion, they won’t stop until a force is applied. As per Newton’s second law, as mass of the object increases, the force needed to move it also increases. The larger a rocket, the stronger the force (for instance, more fuel) to make it accelerate. A space shuttle requires around three kilograms of fuel for every kilogram of payload it carries.

Astronauts in space must also keep the laws of motion in mind. During his pioneering orbit of the Earth in 1961, Russian cosmonaut Yuri Gagarin was the first to experience the practical effects. Gagarin put down his pencil while writing his log. In keeping with Newton;s first law, by which the planets move around the Sun, the pencil floated out of reach. He ended up completing the log using a tape recorder. Now astronauts keep their equipment tethered to a surface with Velcro or bungee straps.

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The publication of Newton’s laws of motion proved to be greatly advantageous for scientists and engineers across the globe. His laws have found applications in everything with moving parts whether it is the design for machines and scientific equipment or clocks and wheeled devices. On the basis of these laws, it was possible to predict whether a machine would work even before it was built.

In the nineteenth century, British engineer lsambard Kingdom Brunel, built huge steamships and suspension bridges using Newton’s laws. James Watt couldn’t have made the first working steam engine without the laws of motion. We use these laws even today to solve the problems related to the construction of modern structures and tall buildings.

Newton’s laws of motion are still the basis of modern mechanical engineering. Its application is spread across different fields. Everyone from oil-well technicians to space engineers and car designers to satellite constructors utilise these laws.

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Newton presented the three laws on motion in 1687 in his book Philosophiae Naturalis Principia Mathematica. The universal laws of motion describe the relationship between any object, the forces acting upon it and the resulting motion.

The first law of motion or the law of inertia states that if a body is at rest or moving at a constant speed, it will continue in that state unless it is acted upon by an external force. This tendency of massive bodies to resist changes in their state of motion is called inertia.

Using this law of motion, we can explain why a car stops when it hits a wall but the human body in the car will keep moving at the earlier speed of the car until the body hits an external force, like a dashboard or airbag.

Similarly, an object thrown in space will continue infinitely in the same speed, on that path until it comes into contact with another object that exerts force to slow it down or change direction.

Newton’s second law of motion is F=ma or force equals mass times acceleration. For example, when you ride a bicycle, your pedalling creates the force necessary to accelerate. This law also explains why larger or heavier objects require more force to move and why hitting a small object with a cricket bat creates more damage than hitting a large object with the same bat.

The third law of motion is, for every action, there is an equal and opposite reaction. This is a simple symmetry to understand the world around us. When you sit in a chair, you are exerting force down upon the chair, but the chair is exerting an equal force to keep you upright.

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The universal law of gravitation was proposed by Newton in 1687. He used it to explain the observed motions of the planets and the Moon. Mass is a crucial quantity in Newton’s law of gravity.

According to the law, every particle in the universe attracts every other particle with a force. This force is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. It implies that the attractive force of gravity increases with the increase in mass and decreases with the increase in distance.

For example, if we transported an object of the mass ‘m’ to the surface of Neptune, the gravitational acceleration would change because both the radius and mass of Neptune differ from those of Earth. Thus, our object has mass ‘m’ both on the surface of Earth and on Neptune, but it will weigh much more on the surface of Neptune because the gravitational acceleration there is 11.15 m/s2. Thus, Newton was able to mathematically prove Kepler’s observations that the planets move in elliptical orbits.

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Isaac Newton was the first to connect gravity to planets other than Earth. He proposed that other planets and stars also have gravitational force. In fact, it was present everywhere in the universe. Planets including Earth remain in their orbits and rotate around the Sun due to the force of gravity exerted by the Sun. It is Earth’s gravitational force that keeps the Moon moving in its orbit. The pull of the Earth causes Moon to travel in a curved path. 

The same principle applies to satellites in orbit around Earth. If Earth had no gravity, the satellites would fly off into space. We can very well say that gravity is what binds the solar system together.

The planets also disturb each other’s orbits due to gravity. These disturbances are termed as ‘perturbations.’ Scientists discovered Neptune because of the unexpected perturbations observed in the orbit of Uranus.

The story commonly told is that Newton saw an apple falling from a tree and discovered gravity while thinking about the forces of nature. Another version says that the apple landed directly on his head. Either way, Newton realized that there must be some force acting upon all objects, causing them to fall.

He also considered the moon which should actually fly away from Earth in a straight-line tangent to its orbit if there hadn’t been a force binding it to Earth. He concluded that the moon is a projectile rotating around the Earth due to gravitational force.

Newton called this force ‘gravity’, something that pulls everything to the ground. The weight of an object is the measurement of the strength with which it is being pulled by gravity. Or in other words, gravity gives weight to physical objects. The reason we can keep our feet firmly on the ground and walk around is gravity. It is what stops objects from flying off into space.

Gravity is the force that had the effect of pushing on the planets and was equal to the pull of the sun. It is in fact responsible for many of the large-scale structures in the universe. Newton also explained the astronomical observations of Kepler using the concept of gravity.

Newton was famously slow in publishing his researches. His New Theory of Light and Colours appeared in the Philosophical Transactions of the Royal Society only in 1672. The publication resulted in a dispute with Robert Hooke who was a dominant figure in the Society.

Newton’s experiments with white light had many practical applications that benefited the common man. Spectacles were a luxury only affordable for the upper classes in the seventeenth century. Even then, the glasses were of poor quality. In the decades following the publication of Newton’s research, amazing advancements were made in the design and manufacture of lens and spectacles.

Similarly, Newton’s findings were also applied to create sophisticated microscopes. Though microscopes existed even during his time, they were basic models that produced blurred images. With the development of better microscopes came breakthroughs in medicine and biology.

However, the most resounding impact of Newton’s work was perhaps the creation of an entirely new science, the science of spectroscopy. Spectroscopy is the study of light in relation to the length of the wave that has been emitted, reflected or shone through a solid, liquid, or gas.

Newton’s discoveries revolutionized our understanding of the most common aspects of nature such as light. Prisms were seen as trivial toys used for fun in laboratories until Newton came across them. He conducted a series of experiments with sunlight and prisms after getting a prism at a fair in 1664.

Newton made the astonishing discovery that clear white light was composed of seven visible colours. The visible spectrum, the seven colours of the rainbow, was scientifically established by Newton. This discovery opened new vistas in optics, physics, chemistry, and the study of the colours in nature.

One bright sunny day, Newton darkened his room and made a hole in his window shutter, allowing just one beam of sunlight to enter the room. He then took a glass prism and placed it in the sunbeam. The result was a spectacular multi-coloured band of light just like a rainbow.

Newton believed that all the colours he saw were in the sunlight shining into his room. He thought he then should be able to combine the colours of the spectrum and make the light white again. To test this, he placed another prism upside-down in front of the first prism. He was right. The band of colours combined again into white sunlight. Newton was the first to prove that white light is made up of all the colours that we can see.

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We may remember Newton mostly in association with the theory of gravity and the story of the apple tree. But he was also a great mathematician on par with legendary figures like Archimedes and Gauss. Newton’s contributions paved the path for numerous mathematical developments in the succeeding years.

Until Newton, algebraic problems where the answer was not a whole number posed a problem for mathematicians. The formula published by Newton in 1676 called ‘binomial theorem’ effectively resolved this issue. It has been said that through Newton’s works, there was remarkable advancement in every branch of mathematics at the time.

Newton (along with mathematician Gottfried Wilhelm von Leibniz) is credited with developing the essential theories of calculus. He developed the theory of calculus upon the earlier works by British mathematicians John Wallis and Isaac Barrow, and prominent mathematicians Rene Descartes, Pierre de Fermat, Bonaventura Cavalieri, Johann van Waveren Hudde and Gilles Personne de Roberval.

While Greek geometry was static, calculus allowed mathematicians and engineers to make sense of the dynamic world around them. They could now make sense of motion such as the orbits of planets and the flow of fluids.

Many modern historians believe calculus was developed independently by Newton and Leibniz, using different mathematical notations. Leibniz was however, the first to publish his results.

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With the outbreak of the bubonic plague, Cambridge University closed its doors in 1665. As a result, Newton was forced to return home to Woolsthorpe Manor where he ended up staying with his mother for over a year. In the peaceful countryside, he concentrated on the scientific problems about which he had wondered during his post graduate years.

Some of his greatest discoveries such as the laws of gravity, laws of motion, and the components of white light had their origin during this time.

It is said that Newton was sitting in the orchard when he saw an apple falling from a tree. Contrary to popular versions of this event, there is no evidence to suggest that the apple had fallen on his head. Pondering upon what he saw, Newton wondered why apples fall straight to the ground rather than going upwards or sideways. Following this line of thought, he finally formulated the law of universal gravitation.

This was the account of his discovery given by Newton himself to his acquaintances including the French philosopher Voltaire; his assistant at the Royal Mint, John Conduitt who was the husband of his niece Catherine Barton; his friend William Stewkeley; and Christopher Dawson who was a student at Cambridge. The note on Newton’s life collected by John Conduitt in 1726 contains the first written account.

The year he spent in Woolsthorpe later came to be called his annus mirabilis (year of wonders). Newton returned to Cambridge in 1667.

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