Johannes Kepler

Johannes Kepler shattered the ancient dogma that the planets move in perfect spheres and, with the assistance of Tycho Brahe’s detailed and precise astronomical observations, proved that the planets orbit in ellipses with the Sun as one of the foci.

Kepler, like many of his contemporaries, had interests in both astronomy and astrology, both of which were reflected in his works.  For the early part of his life and career, Kepler believed that God had arranged the plants orbits into particular geometric schemes.  Originally he thought in two dimensions, with three sided (triangle), four sided (square), five sided (pentagon), six sided (hexagon), and seven sided (heptagon) all perfectly inscribed in a circle, each nested inside each other with the outermost figure being the triangle.  After observation failed to match the model Kepler then though in three dimensional figures using the platonic solids for the model of the solar system.  This model was elegant, perfect, and completely wrong.

Eventually Kepler got his hands on Tycho Brahe’s observational data where he finally deduced the ellipse as the correct orbit of the planets and formulated the three laws of planetary motion that bear his name.   These laws proved crucial to Newton’s discovery of his laws of gravitation.

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Tycho Brahe

During the 16th century, as the Copernican model of the universe became increasingly accepted, astronomers focused their attention on producing more precise measurements of the stars and planets.  The greatest observer of this per-telescopic era was Tycho Brahe, born in 1546 to a Danish noble family, where he rejected a career in politics and instead dedicated his life to astronomy after witnessing a solar eclipse in 1560 that hooked his attention to the sky.

Brahe is best known for his meticulous astronomical observations that he recorded in his observatory granted to him by King Frederick II, on the island of Hven (now called Ven) near Copenhagen.  The observatory had some of the finest instruments of the time, its own printing press, was a frequent destination of visiting scholars, and became a training station of a generation of young astronomers.

The completeness and accuracy of his observations cemented his legacy as one of the greatest astronomers of his era.  The breadth of data compiled in the observatory is no small feat – he accurately plotted the position of nearly 800 stars all without the assistance of a telescope.  Famously, the observational data compiled at the observatory assisted Johannes Kepler in calculating the elliptical orbits of the planets.

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1543: On the Revolutions of Celestial Spheres

The Earth-centered universe was the prevailing wisdom of Medieval Europe until a Polish scholar named Nicolaus Copernicus suggested otherwise in his 1543 book, On the Revolutions of Celestial Spheres.  Copernicus was not the first person to suggest a heliocentric model of the universe, 1800 years prior Aristarkhos of Samos suggested this same idea, however that idea was never able to compete with the geocentric model championed by Ptolemy and laid out in his treatise known as the Algamest, which was to become the dominate cosmology of Europe for over a millennia.  

I therefore took this opportunity and also began to consider the possibility that the Earth moved. Although it seemed an absurd opinion, nevertheless, because I knew that others before me had been granted the liberty of imagining whatever circles they wished to represent the phenomena of the stars, I thought that I likewise would readily be allowed to test whether, by assuming some motion of the Earth’s, more dependable representations than theirs could be found for the revolutions of the heavenly spheres. – Nicolaus Copernicus

The book was published in the same year of Copernicus’ death, just before he died.  It is believed that Copernicus had refused to publish his ideas earlier due to fear of persecution from the Catholic Church, and the books dedication to Pope Paul III was in attempt to assuage the church.  Sadly, this yet another tragic example of dogmatic religion hindering the progress of truth, knowledge and the advancement of science.

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Francis Bacon

“Knowledge itself is power.” – Francis Bacon

If there is one person who could be credited with establishing the principles of science and ushering in the era of the Scientific Revolution it would be Francis Bacon.  Bacon argued for a new way of learning and collecting knowledge, one of forming observations, formulating hypothesis to explain the observations, then testing the hypothesis by rigorous experimentation.

Francis Bacon was born in London in the winter of 1561, home-schooled in his early youth and entered Trinity College at the age of 12.  Although he excelled in the traditional medieval curriculum, he came to the conclusion that the methods were flawed.  After his schooling he spent much of his life working in the British government before publishing his great philosophical work, Novum Organum (new instrument), where he laid out his method of inductive reasoning and the scientific method.

Bacon had an enormous impact on a generation of scientists and he was also an influential proponent in the concept of establishing scientific organizations, where information could be shared and ideas debated.  It was in the Baconian spirit that the British Royal Society was formed in November 1660, possibly the oldest scientific society in existence today.

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Andreas Vesalius

Referred to by many as the founder of modern anatomy, Vesalius was born in Brussels, studied medicine in Paris, and finally settled in Italy as the Chair of Surgery and Anatomy at the University of Padua, which he earned the first day of receiving his medical doctorate from the University.  He published his famous works on human anatomy, On the Fabric of the Human Body,  a collection of seven books presenting a modern anatomical view of the complete human body, rife with many detailed drawings of the human body.

Vesalius was so influential because he was able to correct the errors of earlier anatomists due to his direct observation of the body through the dissection of executed criminals.  The detailed illustrations were drawn by artists present at the dissections and provided a valuable resource for medical students to reference.  The improved printing technology of the Renaissance helped preserve and distribute these drawings.

Later in life, Vesalius joined Charles V court as a doctor, leaving his post in Padua.  After serving a little more than a decade in the imperial court Vesalius embarked on a pilgrimage to the Holy Land where on his return he was shipwrecked on an island and soon died.  He was 50 years old at the time of his death but his influence on anatomy would be permanent.

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1450: The Printing Press

A vital precursor to the scientific revolution, the invention of the printing press changed the way information spread across the world by improving its fidelity and, most importantly, by hastening its rate of reproduction.  An increasing numbers of books with better accuracy quickly spread across Europe and the globe providing the medium for a diffusion of ideas to a growing literate population.

The printing press was the creation of Johannes Gutenberg, whose creative insight was to combine movable type with a pressing mechanism to create the Gutenberg press.  Simple, yet revolutionary.  In order to print a page you first line up the metal type, apply ink, place the paper on top then apply the press.

The printing press allowed for the mass reproduction of printed material.  Within a few decades hundreds of presses were active in hundreds of cities around Europe, and this basic method of mass production of printing did not change much until the late 18th century.

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900: Gunpowder

Gunpowder was invented in China and spread to the Middle East, eventually arriving in Europe around 1300, nearly 400 years after its invention.  Its impact in warfare was substantial and almost immediately felt on the battlefield through infantry weapons, having a devastating effect on the knightly class. Although this was a setback for the nobility they still had their walled castles.

Artillery weapons powered by gunpowder, initially unreliable but once perfected, made once impenetrable castles vulnerable.  Sieging a castle in the Middle Ages was a long and arduous process.  Techniques involved tunneling under walls, ramming down walls, starving out the inhabitants, all of which could take weeks or even months.  However with the invention of cannons a castle could be taken within a single day.

Gunpowder consists of a mixture of saltpeter (potassium nitrate), charcoal, and sulfur.  The sulfur and charcoal act as the fuel, with saltpeter acting as an additional oxidizer creating a stable chemical reaction with the rapidly expanding gases resulting in the propelling motion.

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800 BCE – 200 BCE: Gears

An important technology in allowing people do to work was the invention of the gear, a system consisting of cogs that takes energy from an input source, such as flowing water, and convert it to an output source, such as a pump.  The oldest archeological evidence for gears dates to about 230 BCE in China, however evidence of geared technology before that time is referenced from ancient manuscripts.

There are various different types of gears such as spur gears, bevel gears and worm gears, with each type providing a unique set of advantages and disadvantages.  For example bevel gears change the axis of rotation (such as from horizontal to vertical) and spur gears may change the speed of force of motion.

The earliest gears were uses in wheels and pulling systems and its uses have since expanded dramatically.  Clocks, vehicles, and a multitude of machines would not be able to operate with out properly working gears.

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Probably no other ancient thinker held a greater influence over medieval European intellectual life more than Aristotle.  It’s easy to see why, giving his prolific writings and interests in a wide range of topics that include physics, cosmology, biology, zoology, geology, psychology, mathematics, logic, metaphysics, politics, ethics, justice, and rhetoric – to name a few.  Over 150 books are attested to be authored by Aristotle, although only 30 or so of his works survive to the modern day.

Aristotle was born in Stageria, Macedon, was orphaned at an early age and raised by his uncle.  At age 17 he went to Athens and joined Plato’s Academy where he spent 20 years studying and earning his reputation as one of Greek’s great philosophers.  After his time at The Academy he ended up in King Philip of Macedon’s court, where he tutored his 13 year old son, Alexander, who grew up to be Alexander The Great.

When Aristotle did not receive headship of the Academy in Athens due to political reasons, he started his own establishment around 335 BCE with encouragement from Alexander called The Lyceum.  It is during his time at The Lyceum where he composed most of his works.  Aristotle was forced to leave The Lyceum and Athens again due to political reasons after Alexanders death.  He died shortly after by natural causes.


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One of the most famous mathematicians of the ancient world was Pythagoras of Samos (that town has now been renamed Pythagorion in his honor), born around 569 BCE.  Much mystery surrounds the early life of Pythagoras and it is sometimes difficults to separate fact from legend.  It is believe that around the age of nine, Pythagoras may have traveled to Miletos and was taught by the famous Greek philosopher Thale
s and his pupil Anaximander.  Later on, around 535 BCE it is likely that he traveled to Egypt and Babylon where he was taught geometrical principles that laid the foundation for his theorems.

In about 518 BCE Pythagoras settled in Cronton, a Greek seaport in southern Italy, where he founded a school dedicated to studying mathematics.

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