Isaac Newton's Discoveries

'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 sea-shore, 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

This quote gives us an insight into the working of great minds like Newton. Curiosity, an appreciation of the beauty of nature and excitement of exploring a mystery are the prime driving forces of a scientific mind. Sir Isaac Newton needs no introduction. One of the greatest minds of all time, Sir Isaac Newton's discoveries led to a deeper understanding of nature and gave physics (known as 'Natural Philosophy' in his time) a firm physical and mathematical foundation. Isaac Newton's discoveries in theoretical physics are the prime subject of this article.

Isaac Newton's Discoveries in Theoretical Physics
Sir Isaac Newton contributed to many branches of human thought, among which physics and mathematics were the fields in which he contributed substantially. He synthesized what was known, into a logically whole and consistent theoretical framework, through his laws of motion and theory of gravitation. To create the great generalizations which bind all the loose threads of clues into a coherent whole, is an art that has been mastered by only a few till date. Sir Isaac Newton was one of them. Through invention of 'Infinitesimal Calculus', (credit for which also belongs to Leibniz), Newton also provided a mathematical framework which enabled the harnessing of these theoretical physics principles and predict greater results. One of Isaac Newton's inventions is the reflecting telescope, which was his entry card into the premier 'Royal Society of London'.

The greatest of Newton's discoveries came when he experienced pristine solitude, in which he could meditate on his vague ideas and assimilate them together into a logically coherent whole. The principle that guided Newton's discoveries was simplicity. Like Newton, another theoretical physics giant, Albert Einstein was also guided by simplicity and elegance in his thinking about physical laws. One of Isaac Newton's quotes, magnanimously proves the point;

"Truth is ever to be found in the simplicity, and not in the multiplicity and confusion of things." - Sir Isaac Newton

Newton contributed to various fields of physics and mathematics. Let us talk about Isaac Newton's major discoveries in theoretical physics.

Isaac Newton's Discoveries in Mechanics
Isaac Newton's laws of motion defined the concept of inertia and force. They also revealed the nature of a force. Newton's three laws of motion are as follows:

• Newton's Law of Inertia: Every object stays in its state of rest or uniform motion, unless disturbed by an external force.
• Newton's Force Law: The force acting on a body is defined as the rate of change of its linear momentum, with time.
• Newton's Action-Reaction Law: Every action has an equal and opposite reaction.

These three laws together define the effect that the absence or presence of force has on objects. They together defined framework of mechanics, through which the dynamics of forces and their effects could be analyzed.

Isaac Newton's Discovery of the Law of Gravitation
While the three laws of motion define a type of mechanics, the Newton's law of gravitation defines the universal force of gravity, whose implications can be studied in the mechanical framework that he created through the laws of motion. The Newton's law of universal gravitation states that:

"Every particle of matter attracts every other particle with a force along the straight line joining them and is directly proportional to their masses, while inversely proportional to the square of the distance between them."

Using this law and making extrapolations based on it, Newton, derived Kepler's empirical laws of planetary motion, which naturally emerged from his gravitational theory. Many people observed apples falling down before Newton, but none of them followed the broad generalization that it represented. Even moon falls towards the Earth and Earth towards the Sun, in the same way! That is what Newton figured out through his deep thought!

A paradigm shift which occurred through Newton's law of gravitation was the concept of 'Action at a Distance'. A gravitational force acts between two particles even though they are not in contact with each other. That is, it manifests as an action at a distance. This concept of an action at a distance proved to be the undoing of Newton's theory later and which was overthrown by Einstein's theory of 'General Relativity'.

Even though now superseded by general relativity, Newton's idea of gravitation serves well in understanding the motion of planets and stars to incredible accuracy. For the first time, man could understand the motion of planets and satellites and give it a rational explanation.

Isaac Newton's Discoveries in Optics
Newton was fascinated with the field of optics and he made many major discoveries in this field too. Some of Newton's discoveries in optics are:

• He discovered that white light is composed of component color wavelengths and demonstrated this with the use of a prism. He discovered many properties of the light and colors.
• He predicted the dispersion and aberration of light in telescopes and suggested remedies to correct the same. In the process, he invented a new kind of telescope. Newton promoted the concept of a universal ether through which the light propagates. This was later proved wrong by the special theory of relativity.
• He also put forward the theory that light is made up of corpuscles, which was later proved wrong by Huygens' wave theory of light. However, the idea got a sort of new life when Einstein introduced light to be made of photons which are energy corpuscles. However, photons are far different from the corpuscles that Newton imagined. Nevertheless, he provided the impetus to new lines of thought.

These were the most important of Isaac Newton's discoveries in theoretical physics, that led to a radical change in our world view. One has to only ask two questions - 'why' and 'how' to begin an adventurous pursuit of truth. This journey in pursuit of truth, not only gives you a high, but also makes you connect more deeply with nature. Those of you who enjoy this kind of a scientific pursuit, can certainly understand the way of thinking that led to some of the greatest of Isaac Newton's discoveries.