Comparative Analysis: Geocentric and Heliocentric Universe Models

This essay delves into the historical and scientific debate surrounding the structure of the universe, contrasting the geocentric and heliocentric models. It begins with the Ptolemaic or geocentric model, attributed to Ptolemy, which posited Earth as the center of the universe, explaining planetary retrograde motion through epicycles. The essay then transitions to the heliocentric model proposed by Copernicus, placing the sun at the center of the solar system. It highlights the advantages of the heliocentric model, such as its ability to simplify the ordering of planets and explain planetary motions more effectively. The essay also discusses the challenges faced by the Copernican model, particularly the explanation of stellar parallax, and how later developments, like Kepler's work, addressed these issues. The document concludes by emphasizing the shift from an Earth-centered to a sun-centered perspective, influencing the understanding of the universe and suggesting the potential for other planetary systems.

Running head: MODELLING OF THE UNIVERSE: GEOCENTRIC AND HELIOCENTRIC
Modelling of the Universe: Geocentric and Heliocentric
Name of the student
Name of the University
Author Note

It is 21st century and the Universe is still a lot of mystery. There were too many occasions
where the debates had been made for the structure of the Universe specially the solar system.
Previously the world knew that the Earth is the centre of the Universe proposed by an ancient
Egypt cosmologist Ptolemy in second century (Cherepashchuk 2013). This is called the
Ptolemaic model or the Geocentric model of the Universe. Whereas in the late 1500s, a polish
cosmologist Copernicus first suggested the Heliocentric model (Copernican model) which says
that the sun is the centre of this planetary system. However, the Geocentric model seemed very
logical as Ptolemy successfully found a way to prove a to explain the retrograde motion of the
planets when earth passes by them which he stated the circular epicycle of the planet’s path.
Also, the epicycle’s centre moves in circular path around the earth. He described the motion as a
turning loop of the planet shows the effect (Evans and Cannan 2014). The main drawbacks of
this model were that it did not helped in categorizing planet as each planet was treated
independently. However, the model gave good predictions of the astronomical and cosmological
event for 1500 years. Later it got understood that the retrograde effects happen due to passing by
a planet just like passing a car feels like the other car is moving backwards. The Heliocentric
model described the rotation and revolution of the planets including earth very well (Swerdlow
2017). According to this model, earth orbits around the sun and the moon orbit around the earth.
Also. The sun is the centre of the system except the Universe, as there are uncountable stars in
the Universe and sun is also a star. Heliocentric reduces the complexity in tracking the order of
the planets. The planets are ordered in: Mercury, Venus, Earth, Mars, Jupiter, Saturn etc. The one
thing that Copernicus could not explain, is the (parallax distance) position shifting of the stars if
watched from the two different sides of the earth’s revolution path. Later, it was corrected and
explained by the Kepler a century later of the Geometric Model. It was also described by using a

simple example of human eye and any object. If someone sees his one figure from very close and
keeping one eye closed repeatedly, it is found that the figure changes the position due the
different source (eye) of the image. After slowly moving apart the figure the shift will disappear.
It explains that the shifts of the stars from different position of the earth’s revolutionary paths is
negligible (Huber et al. 2017). The Copernican model suggests that Earth is not the centre of the
Universe that could mean that there are more stars that consist the planetary system. If there is
possibility of having other planets then it can be said that the creation of the earth and life is not
only the case.

References
Cherepashchuk, A.M., 2013. History of the Universe History. Physics-Uspekhi, 56(5), p.509.
Evans, J. and Cannan, C.C., 2014. Mechanical astronomy: a route to the ancient discovery of
epicycles and eccentrics. In From Alexandria, Through Baghdad (pp. 145-174). Springer, Berlin,
Heidelberg.
Huber, D., Zinn, J., Bojsen-Hansen, M., Pinsonneault, M., Sahlholdt, C., Serenelli, A., Aguirre,
V.S., Stassun, K., Stello, D., Tayar, J. and Bastien, F., 2017. Asteroseismology and gaia: testing
scaling relations using 2200 kepler stars with TGAS parallaxes. The Astrophysical
Journal, 844(2), p.102.
Swerdlow, N.M., 2017. Copernicus’s Derivation of the Heliocentric Theory from
Regiomontanus’s Eccentric Models of the Second Inequality of the Superior and Inferior
Planets. Journal for the History of Astronomy, 48(1), pp.33-61.