In 1610 Galileo Galilei published in Sidereus nuncius the results of his telescopic observations. Galileo showed the Copernican system in which the planets circle the sun was correct. In 1632 he published another work that clearly proved that Copernican system was correct. This resulted in Galileo's trial by the Roman Inquisition and his recantation.

 

In 1610, Galileo Galilei made a groundbreaking contribution to science when he published Sidereus Nuncius (“The Starry Messenger”), a book that presented the results of his telescopic observations. Using a telescope, which was a relatively new invention at the time, Galileo observed the night sky in ways no one had done before. His discoveries provided strong evidence in support of the heliocentric model of the universe, a model that was first proposed by Nicolaus Copernicus in the early 16th century. The Copernican system stated that the planets, including Earth, revolved around the Sun, rather than the Earth being the center of the universe as was commonly believed in the geocentric Ptolemaic system.

Galileo’s observations, which he recorded in Sidereus Nuncius, included the discovery of four moons orbiting Jupiter, the rugged and mountainous surface of the Moon, the phases of Venus, and countless stars previously invisible to the naked eye. The discovery of Jupiter’s moons was particularly significant because it directly challenged the prevailing geocentric belief that all celestial bodies revolved around the Earth. Galileo’s findings indicated that not all objects in space orbited Earth, providing evidence for the heliocentric theory. The phases of Venus, which showed that it went through a full set of phases similar to the Moon, further demonstrated that Venus must orbit the Sun.

While Sidereus Nuncius stopped short of directly advocating the Copernican model, it strongly implied that the heliocentric theory was correct. Galileo was cautious in his early work, understanding that directly challenging the widely accepted geocentric model could provoke a backlash from the powerful Catholic Church, which supported the Ptolemaic system.

In 1632, Galileo took a bolder step. He published Dialogo sopra i due massimi sistemi del mondo (“Dialogue Concerning the Two Chief World Systems”), a work that explicitly compared the Copernican and Ptolemaic systems. The book was written as a dialogue between three characters: Salviati, who represented the Copernican system; Simplicio, who defended the Ptolemaic system; and Sagredo, a neutral figure. Through the dialogue, Galileo made a compelling case for the heliocentric model, effectively proving that it was the more accurate representation of the cosmos. Dialogo was written in Italian rather than Latin, the scholarly language of the time, which allowed it to reach a wider audience and made the Copernican theory accessible to the general public.

However, Galileo’s work did not go unnoticed by the Roman Catholic Church. The Dialogo was seen as a direct challenge to Church doctrine, which held the Earth at the center of the universe. The Church believed that the Copernican model contradicted certain passages in the Bible, and in 1616, the Church had issued a decree stating that the heliocentric theory was heretical. Despite this, Galileo persisted in his support of the Copernican system.

In 1633, Galileo was summoned to Rome to stand trial before the Roman Inquisition. The Inquisition accused him of heresy for advocating the Copernican theory. After a lengthy trial, Galileo was found guilty of “vehement suspicion of heresy.” To avoid harsher punishment, Galileo was forced to recant his views publicly. According to legend, after his recantation, Galileo is said to have muttered, “E pur si muove” (“And yet it moves”), referring to the Earth’s movement around the Sun. Although this anecdote may be apocryphal, it reflects Galileo’s steadfast belief in the truth of the heliocentric model despite his forced recantation.

As a result of the trial, Galileo spent the rest of his life under house arrest. Nevertheless, his work continued to influence future generations of scientists. His observations and defense of the Copernican system laid the foundation for modern astronomy and helped usher in a new era of scientific thinking. Galileo’s trial and recantation represent one of the most famous conflicts between science and religious authority, but his contributions to our understanding of the universe remain a cornerstone of scientific progress.