Category Scientist & Invensions

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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