or more accurately how did it replace the geocentric model
Early observations
Indian astronomers, had knowledge of the planets and the Earth’s orbit long before Galileo's time.
Greek scholars like Aristarchus of Samos (310–230 BCE) were among the earliest thinkers to propose a heliocentric model of the universe. Aristarchus was a Greek astronomer and mathematician who famously suggested that the Earth and other planets revolve around the Sun. His model was revolutionary, as it directly challenged the dominant geocentric view (which placed the Earth at the center of the universe) upheld by philosophers like Aristotle and the later Ptolemaic system.
Aristarchus’ heliocentric theory was based on observations that indicated the Sun seemed to occupy a central position in the sky. He also argued that the apparent movement of the stars could be better explained if the Earth were rotating and orbiting the Sun. However, Aristarchus’s ideas were not widely accepted in his time. The Greek geocentric model, supported by the works of Aristotle and Ptolemy, was more intuitive and aligned with both philosophical and religious beliefs that placed humanity at the center of the cosmos. Additionally, Aristarchus lacked the tools and evidence needed to support his heliocentric theory empirically, such as a telescope or precise measurements of planetary motions.
The heliocentric model of Aristarchus was largely forgotten for many centuries, overshadowed by the dominance of the Ptolemaic system, which became the standard for understanding the universe in both the scientific and religious communities. wiki
In his work, The Sand Reckoner, Archimedes of Syracuse (c. 287 BCE – c. 212 BCE) writes about the Earth being in the center of the universe and mentions that Aristarchus proposed a different idea of a much larger universe. According to Aristarchus, Archimedes tells us, the Sun and the stars are immovable, the Earth revolves around the Sun, and the size of this universe is the sphere of the fixed stars, which has the same center as the Sun but is immensely larger. the collector
The first human to successfully calculate the earths circumference was Eratosthenes a Greek mathematician and astronomer, around 240BC.
- Aryabhata, in his work Aryabhatiya, 499CE was one of the earliest astronomers to propose that the Earth rotates on its axis, explaining the apparent motion of the stars as a result of Earth's rotation, rather than the sky rotating around the Earth. He also described a geocentric model of the Solar System, where the Sun and Moon each followed epicycles around Earth. In this model, the planets, including Mercury, Venus, Mars, Jupiter, and Saturn, moved around Earth with varying speeds and motions, reflecting an early understanding of planetary movement. Aryabhata also offered scientific explanations for solar and lunar eclipses, correctly identifying them as resulting from shadows cast by the Earth, not by mythological entities. Most historians of astronomy consider that this two-epicycle model reflects elements of geo-centric pre-Ptolemaic Greek astronomy. Another element in Aryabhata's model, the śīghrocca, the basic planetary period in relation to the Sun, is seen by some historians as a sign of an underlying heliocentric model. wiki thou contradicted here in quora.
- Following Aryabhata, the Kerala School of Astronomy and Mathematics, active from the 14th to 16th centuries, developed further ideas related to a heliocentric model, as indianculture.gov.in notes state.
The prevailing Geocentric model
The Ptolemaic system , which refers to the geocentric model of the universe developed by the Greek astronomer Claudius Ptolemy (c. 100–170 AD) in his work Almagest. In this model, the Earth is at the center of the universe, and all celestial bodies—such as the Sun, Moon, planets, and stars—move in circular orbits around it. The Ptolemaic system was the dominant cosmological model for over 1,400 years, influencing both Western and Islamic astronomy until the Copernican Revolution in the 16th century.
In the Ptolemaic system, the planets and other celestial bodies were thought to move in epicycles—small circular orbits whose centers followed larger circular orbits, known as deferents, around the Earth. This complex system of circles within circles was used to explain the apparent retrograde motion of planets (the phenomenon where planets appear to move backward in the sky at certain times). The epicyclic model allowed Ptolemy to account for the observed motions of the planets with reasonable accuracy, given the observational tools of the time.
It was widely accepted for centuries, particularly in ancient Greece and the Middle Ages. The period during which humans generally believed the Earth was the center of the solar system, a concept known as geocentrism, spanned from the 4thc BC until the 17c AD. This belief was dominant in ancient Greece and continued through the Middle Ages, influencing scientific and philosophical thought for a long time.
Nicolaus Copernicus and the Heliocentric Theory: A Revolutionary Shift in Astronomy
Helio-centric derives its meaning from Greek word helio meaning sun.
Nicolaus Copernicus (1473–1543) was a Polish astronomer and mathematician and is often credited with revolutionizing our understanding of the universe through his heliocentric theory, which proposed that the Earth and other planets revolve around the Sun, contrary to the geocentric model that had dominated Western thought for centuries. Copernicus outlined his groundbreaking ideas in his seminal work De revolutionibus orbium coelestium (On the Revolutions of the Heavenly Spheres), published in 1543, just before his death. However, the theory itself had been in development since around 1510, as Copernicus began formulating a model that would challenge the long-held beliefs of the time.
Before Copernicus, the prevailing view of the universe, known as the Ptolemaic system, held that the Earth was the center of the universe and that the Sun, stars, and planets all revolved around it. This geocentric model was widely accepted not only by scholars but also by the Church, as it seemed to align with Biblical interpretations. Copernicus, however, questioned this model after careful observations and mathematical calculations. By placing the Sun at the center of the solar system, Copernicus argued that the Earth was simply another planet, orbiting the Sun once a year while also rotating on its axis daily. This radically shifted the way people would view the cosmos.
Copernicus’s heliocentric model was not only scientifically revolutionary but also philosophically challenging. By removing Earth from the center of the universe, Copernicus indirectly questioned humanity’s special place in the cosmos, which had been a central theme in Christian thought. Although Copernicus himself did not publish his full findings until 1543, he circulated his ideas among select scholars for years prior, fearing the backlash that might come from religious authorities who saw the heliocentric model as a direct challenge to traditional interpretations of the Bible. In fact, the Church would later place De revolutionibus on its list of prohibited books in the 17th century, though Copernicus’s ideas would lay the groundwork for later scientific advancements.
While Copernicus’s model was not immediately accepted and had several flaws, including the use of circular orbits (which would later be corrected by Johannes Kepler), it marked the beginning of a new era in astronomy. The heliocentric theory provided a simpler and more accurate explanation of the apparent motions of the planets.
Copernicus’s work was a milestone in the history of science, not just for its astronomical significance, but also for its boldness in challenging the prevailing views of the time. His heliocentric theory marked the beginning of the shift from a medieval, Earth-centered view of the cosmos to a modern, Sun-centered understanding that would eventually reshape humanity’s place in the universe.
Tycho Brahe made significant contributions to heliocentrism, specifically through his Tychonic system, a compromise between geo-centrism and heliocentrism, which he developed around 1583. In his model, the Earth is fixed at the center, and the Sun, Moon, and stars revolve around it, while the other planets orbit the Sun. This system was a precursor to the fully heliocentric model proposed by Copernicus.
Kepler
Johannes Kepler significantly contributed to the heliocentric model by formulating his three laws of planetary motion between 1609 and 1619. These laws, published in "Astronomia Nova" (1609) and "Harmonices Mundi" (1619), replaced the circular orbits and epicycles of the original heliocentric model with elliptical orbits, providing a more accurate description of planetary motion.
Kepler’s laws are:
Planets move in elliptical orbits with the Sun at one focus.
A line joining a planet and the Sun sweeps out equal areas during equal intervals of time.
The square of a planet’s orbital period is proportional to the cube of its average distance from the Sun178.
Galileo Galilei - House Arrest, Church, and Friendship
The story of Galileo Galilei and his infamous house arrest has often been painted as a tale of a brilliant scientist persecuted by the Catholic Church for championing the heliocentric theory—the idea that the Earth revolves around the Sun. However, the reasons behind Galileo’s persecution were more complex than just challenging the Church’s teachings.
In a recent discussion about the subject, Neil deGrasse Tyson explains the often overlooked detail that Galileo wasn’t just condemned for asserting that the Earth revolved around the Sun, but rather for publishing a book that ridiculed the Pope personally. This book, Dialogue concerning the Two Chief World Systems, first published 1632, was intended to present the heliocentric theory, but it did so in a way that mocked the Pope as a “simpleton” for his views.
Pope Urban VIII (Maffeo Barberini) and Galileo initially had a cordial relationship and initially enjoyed the patronage and encouragement of Pope Urban VIII, who even allowed him to publish works on Copernicanism as a mathematical hypothesis.
Galileo published the Starry Messenger in 1610, which further supported his heliocentric views with his telescopic observations, particularly of Jupiter's moon. Galileo first openly expressed support for the heliocentric view, the idea that the Earth and other planets revolve around the Sun, in his 1613 work, Letters on Sunspots.
The Churches Reaction
The Catholic Church's formal stance against helio-centrism, -which had been first theorised by Nicolaus Copernicus - was largely a reaction to the latest writings from Kepler and Galileo and a desire to defend its own authority and interpretations of scripture. In 1616 the Church officially declared heliocentrism as a heretical and philosophically false doctrine, after a special committee determined that the theory was heretical . The also church forbade Galileo from defending or holding the view that the Earth revolved around the Sun. This condemnation was primarily a response to Galileo's public support and defense of the heliocentric theory, which was seen as a challenge to the Church's teachings
In 1616 St. Robert Cardinal Bellarminea prominent Jesuit theologian met with Galileo and advised him not to hold or defend views on the helio centric model theory unless he could prove it . The implication was if Galileo could prove the heliocentric theory, the Church would revise its teachings. Until then, however, Galileo was supposed to present it as a theory, not as undeniable truth. Instead, Galileo insisted on teaching it as fact without proof, which led to the conflict with the Church.
Galileo’s Methods and Personality
In Galileo’s approach to both the scientific method and his interactions with others, while he was undoubtedly correct about the heliocentric model, he relied heavily on deductive reasoning and observations through the telescope, andt he couldn’t conclusively prove the heliocentric theory at the time.
Galileo's tendency to insult and belittle those who disagreed with him didn’t help his cause. Rather than engaging in respectful scientific debate, Galileo’s public demeanor often alienated colleagues and opponents alike, further escalating tensions. This aggressive behavior, combined with his failure to prove his claims, made his situation much worse.
This led to Galileo being summoned by the Inquisition in and warned to abandon the theory. He was later found "vehemently suspect of heresy" and sentenced to imprisonment at the pleasure of the Inquisition, which was later commuted to house arrest. His trial took place in 1633, and he was forced to recant his views. He continued to work from home and died at age 77 in 1642 at home, before others especially Newton confirmed his observations.
This, not his advocacy for heliocentrism alone that led to Galileo’s downfall.
The Church’s Position: Not the Enemy of Science
The Catholic Church’s opposition to Galileo was not a pure rejection of science or the heliocentric theory itself. In fact, some Church officials, including early supporters of Galileo, did not oppose the heliocentric model outright. The main issue was Galileo's presentation of the heliocentric theory as indisputable fact, while it was still an unproven theory at the time. Figures like Cardinal Robert Bellarmine wanted Galileo to present his ideas as a theory, rather than as established truth, until solid empirical evidence could be provided. The Church was cautious in its approach, seeking to avoid conflicts with biblical interpretations and holding to the traditional geocentric view of the cosmos.
Galileo, however, chose to argue for the heliocentric model as a proven reality rather than a speculative theory. This became a point of contention. The Church wanted to wait for conclusive proof before accepting the theory as truth, but Galileo's insistence on presenting it as fact—coupled with his publication of Dialogue Concerning the Two Chief World Systems, which ridiculed the Pope’s position—escalated the conflict. His book made fun of the Pope's stance, which was seen as a serious breach of respect and etiquette, likely fueling the Church’s decision to take action against him.
This, it was not his advocacy for heliocentrism alone that led to Galileo’s downfall.
Afterwards
The churchs Acceptance
While the modern world believes in the helio centric model without debate how did the church deal with and accept it .
- 1740-1758: Pope Benedict XIV partially lifted the ban on Galileo's "Dialogue" and Copernican books in general.
- 1758: The general prohibition of books advocating heliocentrism was removed from the Index of Forbidden Books.
- 1822: Pope Pius VII allowed the printing of books advocating for the heliocentric model in Rome.
- 1835: Galileo's "Dialogues on the Two World Systems" and Copernicus' "On the Revolutions of the Celestial Spheres" were removed from the Index of Forbidden Books.
- 1992: Pope John Paul II acknowledged the church's unfair persecution of Galileo.
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