Heliocentrism: the Copernican Revolution – We are not the center of the Universe

scientific revolutionsAhh, to be the center of the Universe, now that’s a comforting thought. Besides, without the use of telescopes what was one to think when they looked to the heavens and saw the constant movement of the Moon and stars, they are revolving around us, seems like a logical conclusion to me. And so it was the accepted science of the early 16th century.

However – the 16th and 17th century proved to be a significant time of learning for humanity, it was during this scientific revolution thanks to breakthroughs in the fields of physics, biology, chemistry, and astronomy laid down the foundations of modern science. When it comes to astronomy, the most influential scholar was non other than Nicholas Copernicus, the man, the legend whom was credited with taking us away from the center of the Universe with his Heliocentric model of the Universe.

Although Copernicus wasn’t the first person in the world to propose Earth was not the center of the Universe, the manner in which he described it and perhaps more importantly his timing was perfect. It came at a time when European astronomers and mathematicians were struggling to figure out the mathematical and observational problems that were arising from the currently accepted idea that Earth was the center of the Universe, known as the Ptolemaic model originally proposed in the 2nd Century CE.

Map of the universe

An illustration of the Ptolemaic geocentric system by Portuguese cosmographer and cartographer Bartolomeu Velho, 1568. Credit: Bibliothèque Nationale, Paris

The Ptolemaic Model, or geocentric systems in which the Earth is the center of the Universe and is circled by all the planets, stars, moon and Sun was the accepted cosmological model since ancient times. By the end of antiquity, this model was formalized by Greek and Roman astronomers, particularly Aristotle (384-322 BCE) – who theorized the physics behind planetary motion, and Ptolemy (100-170 CE) who proposed the mathematical solutions.

It made sense in antiquity, everything is revolving around us, and to us, we are not moving at all. However, it didn’t really account for the long term motion of the planets, most noticeable, the size of the retrograde loop of Mars, and to a lesser extent the other planets. Although not perfect, this model was surprisingly accurate in predicting planetary motions and so was used throughout the Roman, Medieval European and Islamic worlds for over a thousand years.

“To know that we know what we know, and to know that we do not know what we do not know, that is true knowledge.”

heliocentric model

A comparison of the geocentric and heliocentric models of the universe. Credit: history.ucsb.edu

Copernicus began work developing his theory in the 16th century and by 1514 he had begun to circulate copies to his friends and fellow scholars and astronomers of a small 40 page treatise titled:, “Commentariolus,” (Little Commentary). Although not quite complete at this stage, he had already laid down the foundations of Heliocentrism. The main principals described in this treatise stated that:

  • Celestial bodies do not all revolve around a single point
  • The center of Earth is the center of the lunar sphere—the orbit of the moon around Earth
  • All the spheres rotate around the Sun, which is near the center of the Universe
  • The distance between Earth and the Sun is an insignificant fraction of the distance from Earth and Sun to the stars, so parallax is not observed in the stars
  • The stars are immovable – their apparent daily motion is caused by the daily rotation of Earth
  • Earth is moved in a sphere around the Sun, causing the apparent annual migration of the Sun. Earth has more than one motion
  • Earth’s orbital motion around the Sun causes the seeming reverse in direction of the motions of the planets

Continuing with his research and gathering more data for more details work, by 1532 he was nearly ready to publish his dangerous new ideas in his manuscript of his magnum opus – ‘De revolutionibus orbium coelestium,” (On the Revolutions of the Heavenly Spheres). In it he advances the above arguments but this time backs it up with a more details overview and an explanation of the mathematics behind the theory.

One of the most important observations Copernicus made was that by placing the orbits of Mercury and Venus between the Earth and the Sun, he was finally able to account for the different sizes the planets are during the year.  Simply put, when they are on the same side of the Sun as us, they appear larger, and when they are on the opposite side, they appear smaller. He also explained the retrograde motions of other planets further away like Mars and Jupiter by proving Earth was not the fixed frame of reference astronomers thought it was.

copernicusCopernicus was far from a Silly man, and quickly realized how his new theory would be viewed by the church. In a word, unfavorably! Perhaps worse, he knew from experience that those who taught against doctrine could be condemned by the Church, they could have had him locked him for his heresy.  He withheld his research until the year before his death.

“So, influenced by these advisers and this hope, I have at length allowed my friends to publish the work, as they have long besought me to do.”

It was 1542, when he was near death that he finally send his manuscript to Nuremberg to be published. However – despite his fears of condemnation, the controversy of the publication was relatively mild. Over time many religious scholars tried to argue against his model, but reason prevailed. In just a short few generations times, Copernicus’s theory cemented itself as the prevailing model of the heavens.

Galileo's Sketches of the Moon

Galileo’s notes on the Moon – courtesy of galileo.rice.edu

Many scientists and scholars over the following years would defend the theory, Galileo (1564-1642) using the telescope discovered moon orbiting Jupiter, Sunspots and the imperfections on the moons surface; undermining the notion that planets were perfect orbs, rather than share similarities with Earth. Sorry Earth – you’re just not that special. And even though Galileo’s additions to the Heliocentric Model had him locked under house arrest more would still follow.

A German man, whose name you may recognize, Johannes Kepler (1571-1630) an astronomer and mathematician refined the idea by adding elliptical orbits, this showed how some of the planets seem to speed up and slow down during different parts of their orbit.

Copernicus didn’t just take us away from the center of the Universe, his model showed how Earth was capable of motion as well, which inspired a total rethinking of the field of physics. Prior to this it was thought motion was dependent on an outside force, for example the breeze of wind against a sail, or throwing a ball. Inspired by Copernicus, Sir Issac Newton formed the basis of gravity and inertia in his publication, “Principia,” forming the basis of modern physics and astronomy as we know it today. The impact of Copernicus’s theory is nothing short of a Scientific Revolution that propelled humanity from the scientific dark ages and forever changed our understanding and place in the Universe.

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