All of these people made notable contributions to mankind’s understanding of the nature of the solar system and the universe, but the discovery that planets move in elliptical orbits, as opposed to perfect circles as was initially believed, was made by Johannes Kepler in the seventeenth century.

Analytical geometry is the study of geometry that employs a coordinate system and marries geometry and algebra in a way previously not understood by European mathematicians. The work was pioneered by René Descartes in his work La Géométrie. It laid the foundation for the invention of calculus a few decades later by Isaac Newton and Wilhelm Leibniz.

For much of history, from the time when Aristotle lived until the Scientific Revolution, it was assumed that light travelled instantaneously. However, Galileo postulated, correctly as it turns out, that all we can deduce is that light travels faster than the speed of sound, but does not necessarily travel instantaneously.

Antonie van Leeuwenhoek is considered to be the world’s first microbiologist. He greatly improved the capabilities of microscopes, and in doing so, opened up the world of the microscopic to human examination for the first time in human history. Among other things, he is believed to be the first human being to observe single-celled organisms, bacteria, yeast, and blood cells.

On the Fabric of the Human Body is one of the most influential works on human anatomy in European history. It was written by Andreas Vesalius in the mid-sixteenth century and refuted the long held belief in Galen’s understanding of the “humors” and human blood.

Robert Boyle was an Irish chemist who lived during the seventeenth century. He is most widely known for his innovations in the field of chemistry, particularly Boyle’s Law—an equation conveying the inverse relationship between pressure and volume of gas.

Robert Hooke was an English scientist in the seventeenth century who, among other things, pioneered work in the field of microbiology. He was the first man to employ the term “cell” to describe the composition of organisms that he observed under a microscope.

The first reliable mercury thermometer was invented by the German scientist Gabriel Fahrenheit in 1714. The scale used to measure temperature was later altered by the Swedish scientist Anders Celsius, who set the freezing point of water at zero and the boiling point at one hundred and created the Celsius temperature measurement system. Lord Kelvin is famous for inventing the Kelvin scale that sets its zero point at absolute zero, the lowest possible temperature attainable before matter becomes completely motionless and devoid of energy.

Kepler, Copernicus, and Galileo were all notable astronomers in the sixteenth and seventeenth centuries. Collectively they did a great deal to advance our understanding of the Earth’s place in the solar system and in the universe. Copernicus was the first to prove, mathematically (his work improved upon by Kepler), that the sun, not the Earth, was the centre of the solar system. For their efforts, all three of these men had to fear intense church retribution when publishing their works.

The “uncertainty principle” states that you can never simultaneously know the position and velocity of an electron; you can only know one or the other at a time. Essentially, if you know how fast it is moving, you do not know where it is, and vice versa. The exact reasons for this are too complicated to go into here, but the important thing to note is that the nature of this discovery is critical to understanding the scientific perspective of the first half of the twentieth century. The absolute faith in the power of science to explain the workings of the universe was being questioned anew, as science was creating more questions than answers.