# Isaac Newton

Curiously, Isaac Newton born less than a year after the death of Galileo (who, in turn, was born three days before the death of Michelangelo, one of the greatest Renaissance artists). He was extremely fragile in his early months and soon lost his father, being raised by his grandparents when his mother remarried. It is said that he was not very prominent in his studies before adolescence and that he loved to invent and build small objects, from kites to solar and water clocks.

An uncle who worked at Cambridge University noticed his tendencies and was able to take him to study at that university. During his years there, Newton was not considered exceptionally brilliant, but he nonetheless developed a mathematical resource that still bears his name today: Newton's binomial. (With this feature, you can quickly get the powers of the sum of two terms.)

## The Apple

By the time he graduated, a plague epidemic was raging in London, causing him to retire to his mother's farm. It was there that he made his most famous remark: he saw an apple fall from a tree. This ordinary phenomenon led him to think that there would be a force pulling the fruit to Earth and that same force might also be pulling the moon, preventing it from escaping its orbit out of space. (Only much later, taking into account the studies of Galileo and Kepler, and his own experiments and calculations, would Newton formulate this idea on the following principle: "The velocity of fall is proportional to the force of gravity, and inversely proportional to the square of distance to the center of the earth. ")

This would have been the first time it was thought that the same physical law (the attraction of bodies) could apply to both earthly objects and heavenly bodies. Hitherto, following Aristotle's reasoning, these two worlds - Earth and sky - were thought to have completely different natures, each being governed by a specific set of laws. "If I saw beyond the others, it's because I was on the shoulder of giants" (Isaac Newton)

## Light Phenomena

Newton's experiments with light also made surprising discoveries possible. The best known of these was achieved by letting a small beam of sunlight into a dark room and through a glass prism. He found that the beam opened as it emerged from the prism, revealing that it consisted of lights of different colors, arranged in the same order as they appear in the rainbow. To prevent these colors from being added by the glass itself, Newton passed the colored beam through a second prism. As a result, the colors came back together, proving that their meeting formed another beam of white light, just like the initial one.

Indeed, the phenomenon of light refraction occurred whenever light passed through prisms or lenses (less pronounced), which limited the efficiency of telescopes. Newton then designed a reflective telescope in which the concentration of light, rather than being made with a lens, was obtained by reflection in a parabolic mirror. This principle is still used today in most telescopes.

## Disputes

Already known for his optical experiments, Newton returned to Cambridge, where he would become a 27-year-old full professor of mathematics. He was later elected a member of the Royal Society.

In this society of scientific studies, he faced the frequent enmity of Robert Hooke. This belligerent relationship was made worse by Newton's extreme susceptibility to criticism. The biggest feud between the two (out of many over the years) concerned the nature of light: Newton believed it to be composed of particles; already for Hooke, light was made of waves, like sound, (This dispute would continue long after their deaths. We can now consider, in the light of the most advanced knowledge, that this match resulted, as it were, in a draw with two vendors: light has a simultaneously undulatory and corpuscular nature.)

Another dispute, this time international, involved Newton and German mathematician Gottfried Wilhelm Leibniz. Both independently created - and, to complicate matters, almost at the same time - the infinitesimal calculus, based on the studies done by the Frenchman Pierre de Fermat.

## Scientific publications

In 1687 Newton published his most important work, Philosophiae naturalis principia mathematica Mathematical principles of natural philosophy. In this work he includes all his scientific knowledge. It contains, for example, his famous three laws of motion, which allowed him to mathematically formulate the value of the force of attraction between any two bodies anywhere in the universe. Although Newton knew that gravity was constant, this value would still remain unknown for a century, until determined by Cavendish.)

With this relationship, known as the law of universal gravitation, one could finally adequately describe the movements of all the bodies of the Solar System, including the slightest irregularities of their transits. These could now be explained as resulting from the gravitational influence of the various bodies on each other.

If Copernicus is often seen as the initiator of a period of intellectual progress called the Scientific Revolution, Newton can be considered the apex of this rise. Their conclusions explained as many phenomena with as few elements as possible. (This is what many scholars call the "elegant solution.")

Astronomer Edmond Halley (the discoverer of the comet bearing his name) once asked Newton how he could make so many remarkable discoveries. He replied that he attributed them more to a continuous effort of thought than to inspiration or sudden perception. This mental effort, however, must have consumed him so much that, at the age of fifty, he had to interrupt his production for two years due to nervous exhaustion. (It is said that a candle would have fallen on a lump of calculations developed over several years.) This did not prevent him, however, from returning to work or becoming a member of the English Parliament or being director of the Mint.

In 1703, he was elected president of the Royal Society (when Hooke was already dead), a position to which he was reelected annually while he lived. In 1704, he published Opticks, a book that deals with his discoveries in the field of optics.

Interestingly, Newton turned gray at the age of 30, but remained mentally active for life. At 80, he was proud to see and hear well and still have all his teeth!
Trying to gauge his scientific career, he once said, "I have the impression that I was a child playing by the sea, enjoying discovering a smoother pebble or a prettier shell than the others, while the immense ocean of truth remains mysterious before my eyes. "