1642 – 1727

So many extensive books and articles have been written on the life and impact of Sir Isaac Newton over the last three centuries it is impossible to do his achievements justice in a short entry like this. He is quite simply one of the greatest scientists of all time.

. A Slow Beginning

His early years did not necessarily suggest, however, he would end up as such. Born and bred in the quiet village of Woolsthorpe in Lincolnshire, England, and schooled in the nearby town of Grantham, he was not particularly noted for academic achievements as a child. Even on entry to Trinity College, Cambridge, he did not stand out until, ironically, the University was forced to close during the period 1665-1666 due to the high risk of plague. Newton returned to Woolsthorpe and began two years of remarkable contemplation on the laws of nature and mathematics which would transform the history of human knowledge. Although he published nothing during this period, he formulated and tested many of the scientific principles which would become the basis for his future achievements.

However, it would often be decades before he returned to his earlier discoveries. For example, his ideas on universal gravitation did not re-emerge until he began a controversial correspondence on the subject with Robert Hooke in around 1680. Furthermore, it was not until Edmond Halley challenged Newton in 1684 to find out how planets could have the elliptical orbits described by Johannes Kepler, and Newton replied he already knew, that he fully articulated his law of gravitation. Yet he had begun work on the subject back in the 1660s in Woolsthorpe after famously seeing an apple fall from a tree and wondering if the force which propelled it towards the earth could be applied elsewhere in the universe.

Following his declaration to Halley, Newton was forced to recalculate his proof having lost his original jottings, and the result was published in Newton’s most famous work Philosophiae Naturalis Principia Mathematica (1687). This law of gravitation proposed that all matter attracts other matter with a force related to the combination of their masses, but this attraction is weakened with distance, indeed, in inverse proportion to the square of their distances apart. This universal principle applied just as equally to the relationship between two small particles on earth as it did between the sun and the planets, and Newton was able to use it to explain Kepler’s elliptical orbits.

. Newton’s Laws of Motion

In the same work, Newton built on earlier observations made by Galileo and expressed three laws of motion which have been at the heart of modern physics ever since. The ‘law of inertia’, states that an object at rest or in motion in a straight line at a constant speed will carry on in the same state until it meets another force. The second stated that a force could change the motion of an object according to the product of its masses and its acceleration, vital in understanding dynamics. The third declares that the force or action with which an object meets another object is met by an equal force or reaction.

Aside from the wide-ranging uses for the laws Newton outlined in the Principia, the important point is that all historical speculation of different mechanical principles for the earth from the rest of the cosmos were cast aside in favour of a single, universal system. It was clear that simple mathematical laws could explain a huge range of seemingly disconnected physical facts, providing science with the straightforward explanations it had been seeking since the time of the ancients. Newton’s insistence on the use of mathematical expression of physical occurrences also underlined the standard for modern physics to follow.

. Further Achievements

Newton achieved major breakthroughs in other areas too. His proof that white light was made up of all the colours of the spectrum was outlined in his 1672 work New Theory about Light and Colours. In Opticks (1704), he also articulated his influential (if partially inaccurate) particle or corpuscle theory of light.

Another achievement significant to mathematics was his invention of the ‘binomial theorem’.

Newton had a practical side too, inventing the reflecting telescope in the 1660s. This new instrument bypassed the focusing problems caused by chromatic aberration in the refracting telescope of the type Galileo had created.