Introduction
The dark sky has piqued the interest of humans since the dawn of time. From the Babylonians to the Egyptians, Greeks, and Indus, all had a sense of wonder with celestial objects. The intellectual elite developed ideas to explain the miracles of the heavens. Originally, they were thought to be from the gods, but later explanations became more logical and scientific. Yet, proper conceptions concerning the earth and the rotation of the planets did not appear until the Greeks. The two hypotheses for the order of the cosmos, including the planetary wind, are heliocentric and geocentric. According to the geocentric concept, the Earth is at the centre of the natural world or universe, while the planets, sun, moon, and stars revolve around it. The sun was regarded as the centre of the early heliocentric models, and the planets rotated around it. No one can refute that the earth rotates around the sun in the current world environment. But, there was also a time (roughly 5 centuries ago) when the entire world assumed that the sun did circle the Earth.
Geocentric model vs Heliocentric model
The primary distinction between geocentric and heliocentric models is that the geocentric model places the earth at the centre of the cosmos or universe, whereas the heliocentric model places the sun at the centre and planets orbit around it. In this theory, we presume that the Earth is the centre of the universe and that the sun revolves around it. According to the heliocentric hypothesis, the sun is the centre of the universe. Ptolemy, a Greek philosopher, developed the geocentric concept. Nicolaus Copernicus was a Polish monk who proposed the heliocentric concept in response to the Ptolemaic paradigm.
Ptolemy's model depicted a stationary Earth, whereas Sunopernicus contended that the Sun was static and that other planets, including Earth, rotated around it. The Ptolemaic geocentric paradigm was widely accepted until the 1500s when the heliocentric model developed. We began to believe in the sun as the centre of the solar system and planets moving around it when Galileo supported the Copernican theory, which was later verified by Johann Italicus Kepler.
Difference between Heliocentric and Geocentric in Tabular Form
| Parameters of comparison | Geocentric | Heliocentric |
| Definition | any hypothesis of the construction of the solar system (or the cosmos) in which Earth is thought to be at the centre of everything. | The astronomical model in which the Earth and planets revolve around the Sun, which is located at the centre of the universe. |
| Developed by | Aristotle | Copernicus |
| Earth | Earth is stationary. | Earth is not stationary. |
| Materials | Apart from the earth, everything else in the universe is made from Aether. | All the celestial objects including the earth are made from earth-like materials. |
| Main difference | In geocentrism, Earth is the center of the solar system or universe. | In heliocentrism, Sun is the center of the solar system or universe. |
What is the Geocentric model?
"Geocentric" implies "measured as if from the centre of the earth," according to the dictionary. The geocentric hypothesis describes a geocentric system in which the Earth is at the centre of the solar system and other objects or planets orbit it. This theory, promoted by philosophers such as Plato and Aristotle, posits that all objects or planets ring the Earth, with the stars on the outermost sides and the moon on the innermost. This is the oldest idea, developed by Greek philosophers centuries ago.
This hypothesis is also known as the "Ptolemaic system," after the Greek scientist Claudius Ptolemy. In physics, it is also known as the Aristotelian Universe after Aristotle. Notable scientists who support this theory include Pythagoras. This idea has stayed popular for so long because it explains why everything falls freely towards Earth and why all planets remain at specific distances from Earth. This hypothesis was challenged in the 16th century by Galileo Galilee's invention of a scientific device known as the telescope.
In astronomy, a geocentric model is a paradigm that states that Earth is indeed the centre of the solar system. In other words, this is a halted universe description with Earth in the centre. The Sun, moon, stars, and other planets orbit the Earth in this model. In many ancient civilizations, notably Aristotle's in classical Greece, this was the dominant description of the cosmos.
There are two observations according to this model
- The Sun appears to revolve around Earth once each day from anywhere on Earth. While the Moon and planets have their motions, they appear to circle Earth once every 24 hours. The stars looked to be fixed on a celestial sphere that rotated once every day about an axis across Earth's geographic poles.
- An earthbound observer observes no movement in the earth because it seems solid, stable,
History
The ancient Greeks, Romans, and mediaeval philosophers attempted to integrate the geocentric model with the concept of a spherical Earth rather than the flat Earth model. This model first appeared in Ancient astronomy and philosophy. Pre-Socratic philosophy, for example. Plato and his student Aristotle constructed a cosmos structure based on the geocentric model in the fourth century BC. It depicted the Earth as a fixed sphere at the centre of the universe. The moon, sun, Venus, Mercury, Mars, Jupiter, Saturn, and some other fixed stars were carried around the Earth on spheres or circles in the order of the moon, sun, Venus, Mercury, Mars, Jupiter, Saturn, and some other fixed stars.
They are two models
- Aristotelian physics
- Ptolemaic Universe
Aristotelian physics
The structuring of the cosmos into concentric spheres, with the Earth at the centre and celestial spheres surrounding it, is a key principle of Aristotelian physics. The terrestrial sphere was composed of four elements that were vulnerable to change and decay: earth, air, fire, and water. The celestial spheres were made of an immutable fifth element, aether. Things composed of these elements move naturally: those made of earth and water tend to fall, while those made of air and fire prefer to soar. The speed of such motion is determined by their respective weights and the density of the medium. According to Aristotle, a vacuum could not exist because speeds would become infinite.
The Sun, Moon, planets, and stars are all embedded in precisely concentric "crystal spheres" that spin at constant rates forever. Because the celestial spheres cannot alter except through rotation, the terrestrial sphere of fire must account for heat, brightness, and the occasional meteorite. [9] The lowest celestial sphere is the only one that comes into contact with the sublunary orb's changing, terrestrial substance, drawing the rarefied fire and air under it as it spins.
Ptolemaic Universe
Eccentric motion is the first premise of the Ptolemaic model. From a terrestrial perspective, a body travelling at uniform speed on a circular course with Earth at its centre will sweep out at equal angles at equal times. If the path's centre is removed from Earth, the item would sweep out right angles at unequal times (again, from a terrestrial perspective), travelling slowly when farthest from Earth (apogee) and quickly when closest to Earth (perigee) (perigee). Ptolemy explained the Sun's changing velocity through the zodiac using this basic eccentric model. Another variation of the concept, suitable for the Moon, gradually shifted the orientation of the line from apogee to perigee.
Ptolemy used eccentricity with an epicyclic model to describe the motion of the planets. Each planet circles uniformly along a circular path (epicycle) in the Ptolemaic system, the centre of which revolves around Earth along a bigger circular path (deferent). Because one half of an epicycle moves in the opposite direction as the different path, the overall motion seems to slow down or even reverse direction (retrograde). The epicyclic model described the observable occurrence of planets retrograding when at perigee by carefully coordinating these two cycles. Ptolemy accentuated the effect of eccentricity by having the epicycle's centre sweep out equal degrees along the deferent in equal times as seen from a position known as the equant.
What is heliocentric?
The heliocentric theory took the place of geocentrism. This hypothesis holds that the sun is at the centre of the solar system. Heliocentric is defined as "sun being seen from the centre of the sun" in the dictionary. While the geocentric theory predominated, the heliocentric model concept was there as early as 200–300 B.C. As technology advanced, more and more issues arose that the geocentric theory of the solar system was unable to address. Astronomer Nicolaus Copernicus assembled the efforts of earlier astronomers and put forth a hypothesis in the 16th century that put the sun at the centre of the solar system and had the planets, stars, and Earth revolving around it. Edwin Hubble established that the sun was not the hub of the solar system, but rather one among millions of worlds. In his model, our planet Earth is positioned third from the Sun. He assumed that the Earth spins about its axis and that the stars do not rotate around it. It causes the stars in the sky to appear to move.
Ancient Greece is also where the idea that the sun is the centre of the cosmos first appeared. The notion was first put forth by the Greek philosopher Aristarchus of Samos in the third century BC, but due to the impact of the Aristotelian view of the cosmos and the lack of evidence at the time, it was not taken seriously. Nicholaus Copernicus, a mathematician and Catholic theologian, created a mathematical model to describe the motion of the celestial bodies during the Renaissance. His model placed the sun at the centre of the solar system, with the Earth and other planets orbiting it. And it was believed that the moon rotated around the Earth.
Copernican Heliocentrism
Copernican heliocentrism is an astronomical concept devised and published by Nicolaus Copernicus in 1543. The Sun was placed at the centre of the Universe, immobile, with Earth and the other planets orbiting it in circular orbits modified by epicycles and at uniform speeds. The Copernican paradigm supplanted Ptolemy's geocentric concept, which had put Earth at the centre of the Universe for ages.
Although he had communicated an outline of his heliocentric theory to colleagues before 1514, he did not decide to publish it until pressed by his pupil Rheticus. Copernicus' objective was to propose a practical alternative to the Ptolemaic model by measuring the length of a solar year more elegantly and correctly while keeping the metaphysical implications of a mathematically ordered world. As a result, his heliocentric model preserved numerous Ptolemaic components, resulting in inaccuracies such as the planets' circular orbits, epicycles, and uniform speeds.
Observation from this theory
The Earth is one of several planets that revolve in a specific order around a fixed sun. The Earth moves in three directions: daily rotation, annual revolution, and annual axis tilting. The Earth's motion explains the planets' retrograde motion. The distance between the Earth and the Sun is tiny in comparison to the distance between the Sun and the stars.
Heliocentrism By Johannes Kepler’s
Johannes Kepler’s Heliocentric Model showed that the orbits of planets are ellipses rather than circular. Kepler followed Copernicus' heliocentric method, although he first perfected Ptolemy's conception of the solar system (or, rather, its heliocentric equivalent). Consequently, Kepler rectified Ptolemy's incorrect equates model of the sun's apparent orbit around the earth with a revised one containing an equant, half the orbit's eccentricity.
Kepler also included equants in the superior and inferior planets' epicycles. When Kepler completed Ptolemy's model, the heliocentric nature of the solar system became clear to him. For example, he discovered that the superior planets' epicycles, the sun's apparent orbit around the earth, and the inferior planets' deferents all had the same eccentricity. The obvious assumption is that these circles all correlate to some kind of shared motion inside the solar system—specifically, the motion of the Earth around the sun.
Difference between geocentric and heliocentric in points
- According to the heliocentric theory, the sun is at the centre of the solar system, in contrast to the geocentric hypothesis, which places the earth at its centre.
- All things, including the moon, sun, and stars, are said to orbit the Earth according to the geocentric theory, but all other objects, including the Earth, moon, and stars, are said to orbit the Sun according to the heliocentric theory.
- The moon spins around the Earth following the geocentric theory, however in the heliocentric theory,
- Earth spins on its axis, giving the appearance of moving stars.
- The geocentric theory asserts that the heavenly bodies' paths of movement are circular, whereas the heliocentric hypothesis states that the paths of movement are elliptical.
Conclusion
According to the geocentric concept, the Earth is at the centre of the cosmos or universe, while the planets, sun, moon, and stars revolve around it. The sun is considered the centre of the early heliocentric models, and the planets orbit around it. Other celestial bodies, such as planets, are said to rotate around Earth in the geocentric model, whereas planets are said to revolve around the Sun in the Heliocentric model. The Heliocentric concept is supported by scientific facts and observation, whereas the Geocentric model is supported by ancient beliefs but lacks proof.
