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Our Inspiration > Sir ISAAC NEWTON

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Sir ISAAC NEWTON

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"If I have been able to see further, it was only because I stood on the shoulders of giants."

Born Christmas Day 1642 in Woolsthorpe (Lincolnshire, England), Isaac Newton is one of the most influential scientists the world has known. His father, an illiterate but moderately wealthy farmer, died three months before his birth. He attended boarding school before entering Trinity College, Cambridge University, where he lived from 1661 to 1696. As the plague spread across England and leading to the closure of Cambridge University, the 22year-old Newton returned to Woolsthorpe and, working alone, established the theoretical framework that would shape the direction of physics for the next two centuries.

Ask the scientist?

- Why do apples keep falling on my head?
- How does the moon orbit the Earth?

Curriculum Vitae

1642 (25 Dec.) Newton's birth in Woolsthorpe, Lincolnshire, UK
1643 (4 Jan.) Alternative birth date (corrected Gregorian calendar date)
1661 Attends Trinity College, Cambridge University
1669 Elected Lucasian professor of mathematics
1672 (11 Jan.) Elected Fellow of the Royal Society
1676 (5 Feb.) Letter to Hooke including quote "…on the shoulders of giants"
1682 (Sept.) Observes comet to be later named Halley's Comet
1687 (5 July) Publishes Principia
1703 Elected President of the Royal Society
1704 Publishes Opticks
1705 (16 April) Knighted by Queen Anne
1727 Newton dies and is buried at Westminster Abbey

Achievements

MATHEMATICS : invented integral calculus, and (with Leibnitz) differential calculus

THEORETICAL ASTRONOMY : defined the laws of motion and universal gravitation , used to predict the motion of the stars, and of the planets around the sun .

OPTICS : developed the first reflecting telescope

WRITINGS : defined a unified system of laws applicable to a range of physical phenomena, leading to his two principal works - Opticks and Principia - and, among other applications, the Universal Law of Gravity .

Talk Back

About that apple…
The story goes that Isaac Newton was taking tea under an apple tree one sunny afternoon when an apple dislodged itself and landed on his head. It dawned on Newton that what goes up must come down, and this formed the basis of his Universal Law of Gravity. A tale perhaps, but there is evidence in writings at that time to suggest it actually happened.

What is more likely to have happened is Newton, upon observing the falling apple, established his theory on gravitation in connection with the notions of 'acceleration' and 'velocity'. Newton established that there must be a 'force' acting on the apple to cause its acceleration (Newton's 2nd Law) as it moves back toward the Earth. This force he called gravity . He imagined that, if the tree were twice as high, the apple would still accelerate straight towards the Earth's centre, confirming that gravity reached even the tallest tree. His deduction: gravity is not limited to a certain distance from the Earth but that the force of gravity extends much farther, even as high as the stars.

Around the world with Sir Isaac
Newton's greatest insight came when he applied the notion of gravitational force on the Earth to the motion of the moon around the Earth. He reasoned that the moon's orbit about the Earth could be caused by the same acceleration that drew the apple to the ground. He gave the following example: If we were to fire a cannon horizontally from a mountain top, the projectile will eventually fall to Earth following the shortest trajectory - because of the gravitational force directed on the centre of the Earth and the associated acceleration (change in velocity).

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Increasing the muzzle size of the cannon and velocity of the projectile, the cannonball will take longer to fall to Earth and thus travel further. Newton concluded that, projected at just the right velocity, a cannonball could, theoretically, travel all the way around the Earth, constantly 'falling' within the gravitation field but never actually reaching the Earth, which curves away at the same rate as the falling cannonball. Of course the cannonball is a simile for the moon. Newton reasoned that the moon continuously 'falls' as it travels about the Earth in line with the acceleration caused by gravity, hence producing an orbital effect.

LAW OF UNIVERSAL GRAVITATION: Every object in the universe attracts every other object with a force directed along the line of centres for the two objects that is proportional to the product of their masses and inversely proportional to the square of the separation between the two objects.

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