A Brief History of Early Modern Astronomy

Posted by E. Gazelle on March 9, 2009

The Modern Science of Astronomy

While astronomy can be traced back to ancient civilisations, the science of astronomy as we know it today, only began in 1543 when Nicolaus Copernicus published his book, De Revolutionibus Orbium Coelestium (“On the Revolutions of the Celestial Spheres”), which was often regarded as the starting point of modern astronomy.  Copernicus’ heliocentric theories started the ball rolling, which gained maximum momentum with the successful construction of the first astronomy telescope by Galileo Galilei in 1609.

By the 20th century, professional astronomy has branched into two distinct fields of study: observational astronomy and theoretical astronomy. Observational astronomy focuses on the acquisition and analysis of data using basic principles of physics. Theoretical astronomy, on the other hand, is more concerned with the development of analytical models to describe astronomical objects and phenomena.  The two branches complement each other with theoretical astronomy seeking to explain the observed results while observations are being used to confirm the theoretical models forwarded.

Astronomy in the Middle Ages

European history is generally divided into three “ages”, namely the Classical Civilization of Antiquity, the Middle Ages, and the Modern Period.  The Middle Ages lasted for about a thousand years, from the 5th century to the beginning of the Early Modern Period in the 16th century.

Ptolemy’s World View

The view of the Universe in the Middle Ages was very much influenced by the geocentric theories of the Greek philosophers, Aristotle and Claudius Ptolemy (circa 150 A.D).  In Ptolemy’s model, the earth was stationary and fixed at the center of the Universe. All celestial bodies, including the sun and the “fixed” stars, revolved around it.

Astronomy in the Renaissance Period

In the “transitional” period between the late Middle Ages and the Early Modern Period (roughly from the 14th to the 17th century), the cultural movement known as Renaissance swept through Europe.  It was not only a period of social and political upheaval, but was also a period of widespread educational reform, witnessing revolutions in many artistic and intellectual pursuits.  In the arts, it was best known for the contributions of such great artists as Leonardo da Vinci (1452-1519) and Michelangelo (1475-1564).  In the field of astronomy, there were Nicolaus Copernicus, Tycho Brahe, Galileo Galilei, Johannes Kepler and Isaac Newton, among the notable contributors to the wealth of our scientific knowledge.

Nicholas Copernicus (1473-1543)

Copernicus was a Polish astronomer and mathematician.  While Greek, Indian and Muslim scholars had published heliocentric hypotheses centuries before Copernicus, he was the first to present a scientifically-based heliocentric cosmology where the Earth is not static and is not at the center of the Universe.

Copernicus’ theories were rejected by the Catholic Church as they went against the prevailing religious beliefs.  The ban on Copernicus’ book was only removed by the Church in 1835.

The following are astronomical objects named after Copernicus:-

* Copernicus crater on the Moon
* Copernicus crater on Mars
* 1322 Coppernicus, an asteroid orbiting the Sun.

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Tycho Brahe (1546 – 1601)

Tycho Brahe was a Danish nobleman and an astronomer.  He built what was regarded as the first real astronomical observatory from which he observed the heavens.

Brahe devised some of the most precise instruments which allowed him to make accurate naked eye astronomical measurements of his time – before the invention of the telescope.  From these observations, Brahe compiled a comprehensive table of planetary positions and catalogued more than 1000 stars over a 20-year period.

Among Brahe’s notable observations were the supernova of 1572 and the Comet of 1577, which he determined was not an atmospheric phenomenon, thus shattering Aristotle’s views of crystalline spheres.

Brahe developed his own theory of planetary motions, a fusion of the geocentric and heliocentric theories, in which the Sun orbited the Earth and the other planets orbited the Sun.

While Brahe’s views were not always correct, the quality and accuracy of his observations was instrumental in the development of modern astronomy.  Following Brahe’s death, Kepler obtained possession and devoted his time in analyzing Brahe’s extensive data.

Galileo Galilei (1564 – 1642)

A Dutch lensmaker by the name of Hans Lipperhey who was Galileo’s contemporary, discovered that objects, when viewed through a combination of a convex and a concave lens, seemed to appear closer.  Galileo, an Italian scientist, was extremely interested in this discovery and carried out numerous experiments.

On 21 August 1609, Galileo finally produced the world’s first astronomy refractor telescope.  With his telescopes, Galileo saw craters on the moon, Saturn’s ring, the phases of Venus, Sun spots, Jupiter and its four moons and that the bright Milky Way Band was actually made up of countless stars.  In 1610, Galileo published the results of his telescopic observations.

Galileo’s theories embraced those of Copernicus’ which was regarded as heresy by the powerful Church.  In 1633, under the threat of torture and death, he was forced to renounce all beliefs in Copernican theories.  He was then placed under house arrest for the rest of his life.

In 1992, 359 years after the trial, Pope John Paul II lifted the edict of inquisition against Galileo. Another less fortunate Copernican, Giordano Bruno, was tried before the Inquisition in Rome, condemned and burned at the stake in 1600.

Johannes Kepler (1571-1630)
The Laws of Planetary Motion

Johannes Kepler, a German mathematician and astronomer, was hired by Brahe as an assistant to analyze the data collected from his observations.

The next great development in the history of astronomy was a combination of the theoretical genius of Kepler and the superb quality of Brahe’s voluminous data.

Kepler discovered that the Earth and planets travel about the Sun in elliptical orbits and promulgated three fundamental laws of planetary motion, now called Kepler’s Law.

Kepler’s other important contributions are in the fields of optics and geometry.

Sir Isaac Newton (1642-1727)
Convergence of Physics and Astronomy

Sir Isaac Newton, along with Einstein, was regarded as the most important figure and the most original thinker in the development of modern science. Newton’s contributions were astoundingly multi-faceted, encompassing physics, astronomy and calculus.

Newton’s scientific masterpiece, the Philosophiæ Naturalis Principia Mathematica (“The Mathematical Principles of Natural Philosophy”, often shortened as Principia or Principia Mathematica) was published in 1687. He presented evidence to support Copernicus’ heliocentric theory by showing how gravity produces the forces and movements that we see all around us.

The Copernican system was finally firmly established.

According to Newton, all natural laws can be expressed mathematically, allowing for verifiable predictions to be made. A significant early prediction based on Newton’s laws was made by Edmund Halley who financed the publication of the Principia. Halley predicted that a comet, last seen in 1680, would return in 1758. That bright fireball came blazing on schedule and was named after the man who predicted its arrival.

Going Forward – Astronomy for All

Astronomy is unique compared to other sciences in that many important astronomical discoveries are contributed by non-professional amateur astronomers who have played a very significant role in its development.

This year, the International Year of Astronomy (IYA), and 400 years since Galileo first looked at the heavens through his telescope, is a good time to reflect and to engage everyone in pursuing the objectives of IYA.

Nicolaus Copernicus (1473-1543)
Tycho Brahe (1546-1601)
Galileo Galilei (1564 – 1642)
Johannes Kepler (1571-1630)
Isaac Newton (1643 – 1727)

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