Tag Archives: Sir Isaac Newton

Newton’s Light

In 1665 England is stricken by the final waves of the bubonic plague. Cambridge university closes down to avoid plague and a young Isaac Newton returns to Woolsthorpe, his family home in the country side. For the next 18 months Isaac Newton made discoveries that would define the rest of his scientific life, especially his work in optics.

Woolsthorpe-manor
Newton’s family home and birthplace in Woolsthorpe-by-Colsterworth.

Since the time of Aristotle, great thinkers believed that white light was pure. Colored light was created by altering white light, hence a prism creates different colors by internally altering pure light. Newton, incredulous, devices a test of his own. By passing sunlight through a prism he produces a spectrum of colors. However when passing red light through a second prism, it remains red. Since red light was not altered, white light had to be a combination of colored light.

NewtonsTelescopeReplica
A replica of Newton’s reflecting telescope. Newton saw his invention as a toy, but his colleague though otherwise.

As the plague subsides, Newton returns to Cambridge in 1667. There, Newton notices that the edges of telescope lenses acted like prisms thereby falsely coloring objects being observed. To solve this Newton uses a series of mirrors rather than lenses. This not only removes false colorizations, it also makes his reflecting telescope much shorter then conventional refracting telescopes. To Newton’s dismay, his telescope made him famous throughout the scientific community and in 1672 he was elected member of the Royal Society. That same year Newton publishes his first paper on colors.

Newton’s eighteen months at Woolsthorpe were legendary. His insights on intervals almost as small as zero became the foundations of infinitesimal calculus. His understanding of forces and gravity becomes the cornerstone of his Magnus Opus the “Principia” (published in 1689). He would later be elected as President of the Royal Society in 1703 as well as serving as a member of parliament in 1689 and 1701. Though well honored and distinguished, Sir Isaac Newton publishes his second major work “Opicks” in 1704, long after his initial discoveries at his home in Woolsthorpe.

Special thanks to Fran May for the featured image

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The Longitude Problem

On October 22 1707, a fleet of English ships returning home from a war with France, meets tragedy. While believing they were on course for Portsmouth England, four ships ran aground on the Scilly Islands killing about 1400 men. In turns out that the fleet was only five degrees longitude west from their destination. Realizing that sailors had no way of calculating their longitude, the Board of Longitude formed in 1714, promises a reward of £20,000 (several million today) to anyone who could provide a solution.

John_Harrison
John Harrison (3 April 1693– 24 March 1776) was an English carpenter and watch maker.

The problem is so significant that the board is comprised of prominent figures such as Sir Isaac Newton, and attracts the attention of prominent mathematicians and scientists such as Leohard Euler. Though a grand and seemingly complicated problem, the solution comes from a simple watch maker, John Harrison.

Harrison realizes that the answer istime. Since the earth revolves once every 24 hours a location 15 degrees longitude away from home-port would be one hour different than the time at home-port. Thus a sailor only needs to know the time at his location and his time at home-port and from there calculate the longitude.

H4_low_250
The H4 Chronometer created by John Harrison was very effective. A replica was tested by Captain James Cook who praised its accuracy.

The only problem was that clocks at the time weren’t accurate at seas since the rocking motions and temperatures made the pendulum unable to keep time. Harrison chose to replace the pendulum with what today is called a balanced wheel. The balanced wheel like the pendulum swung back and forth to count time, the difference was that the balance wheel relied on springs rather than gravity.

The board claiming that Harrison’s H4 Chronometer was insufficient, awards Harrison £10,000. Harrison pleads his case to King George III. King George personally tests one of Harrison’s chronometers for ten weeks in his palace. After months of testing, Parliament awards Harrison an additional £8750 but most importantly, Harrison is given recognition for solving the longitude problem. Three years later, on 24 March 1776, Harrison dies.

Harrison’s life long dedication to clock making not only solves the longitude problem but revolutionizes Oceanic travel. Accurate time keep would later become the foundation of today’s GPS navigation system.

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On the shoulders of giants; Newton’s vision

Sir Isaac Newton (1642 – 1727) – Lucasian Professor (1669-1702), knighted in 1705, President of the royal society (1703-1727), Warden of the Mint (1696-1699) then Master of the Mint in (1699-1727) – is considered today one of the most influential scientists of all time. His Opus Magnus, the Principia, is the foundation of physics and engineering. However, his words carry a greater weight: “If I have seen further it is by standing on the shoulders of giants.”

Within the Principia are Newton’s three laws of motion. These laws allow us to build airplanes and to explore the universe. They allow us to build unimaginable monuments of engineering. They are the foundations of both classical and quantum mechanics. These laws, according to Newton, came because he stood on the shoulders of giants.

Euclid
Euclid

Newton grew up reading Euclid’s work. He studied number theory, geometry, and irrational numbers. As a hobby he computed logarithms, each time more accurately. His reliance on mathematics and proof separated him from many of his more philosophical peers.

Johannes Kepler
Johannes Kepler

Decades earlier, Johannes Kepler formulated Kepler’s laws of planetary motion. Planets orbited in ellipses, with the speed of each depending on its position on the ellipse. This was confirmed by the vast observations gathered by Tycho Brahe. Nevertheless, Kepler could not explain why the planets revolved this way.

Rene Descartes argued that objects could only affect other objects by touching them. Space according to him was filled with objects called “vortexes” which caused the motion of the planets. Newton would take this one step further. These “vortexes” were replaced by the force of gravity.

Rene Descartes
Rene Descartes

Newton’s laws were simple. First, if there is no force on an object, then the object cannot accelerate. Second, force is equal to mass times acceleration. Third, for every action there is an equal but opposite reaction. Now the planets orbited because of the force of gravity; without it they would fly off in straight lines. Planets were always accelerating and decelerating due to gravity, thus their speed changed throughout their orbit.

With the publication of the Principia, science would now depend on mathematics and rigor. His work provided the framework of the science to come. By innovating the works of previous giants, Newton was immortalized. “What Descartes did was a good step … If I have seen further it is by standing on the shoulders of giants.”

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