Since the beginning, humans have looked up at the sky and attempted to make sense of the universe. In Ancient times, geocentric models of the universe were commonly accepted as the truth–meaning that most people thought that the planets in our solar system revolved around our home planet, Earth. Aristarchus of Ancient Greece was the first person to suggest a heliocentric model of the universe–meaning that all the planets of our solar system, including Earth, actually revolve around the sun–but his idea was ignored for several centuries.
Astronomers throughout history continued to try to plot the movement of the planets in our solar system, but the way Mars moved stumped them, for it appeared to change direction at different points in time. Finally, in 1543, Copernicus published his findings on the universe we live in, and his theories changed science forever. He found that not only was our universe heliocentric, but also that the Earth’s axis shifts over time, causing the North Pole to change as well. His heliocentric model and other findings explained Mars’ strange motion as well. When Earth passes by Mars, it appears to go backwards, then appears to go forwards once again once Earth has passed.
Newton and Kepler based their ideas of gravity and motion on the heliocentric model, and the heliocentric model is still used today when studying space. I found an article on universetoday.com called “What Is The Difference Between the Geocentric and Heliocentric Models of the Solar System?” that explains all of this.
UPDATE: (CONNECTION TO CLASS) I liked the article because it explained all of the information that we learned in class in a condensed, easy to read format. Reading the article explained the differences between heliocentric and geocentric models, and how these discoveries gave way to Kepler’s and Newton’s theories of planetary motion and gravity.
The fourth conceptual objective, I can describe how the heliocentric model of the solar system was developed and why it was adopted over the geometric model of the universe, has been discussed frequently in class. In class, we discussed and eventually came to the realization that the “Earth circles the Sun”. Prior to this belief, many philosophers, scientists and astronomers believed that the Earth was at the center, otherwise known as the geocentric belief. This conceptual objective goes into depth about factors that dispute the geocentric belief. As time went on, more evidence surfaced that supported the heliocentric theory. These findings ultimately dismissed the geocentric theory. The philosopher most known for believing that the Earth was at the center of the universe was perhaps, Aristotle. Eventually, Copernicus came along and proposed that the sun was, in fact, at the center of the solar system. Other discussion topics in class included retrograde motion. Retrograde motion played a big role in supporting the heliocentric theory. As defined in class, retrograde motion is when the Earth overtakes the slower moving outer planets, causing the planets to appear to move backward compared to the background stars. The article I chose, “The Copernican Model: A Sun-Centered Solar System”, discusses the events leading up to Copernicus’ new model and how it was eventually adopted. This article closely relates to the fourth conceptual objective. The Earth was believed to be at the center of the universe for nearly 2000 years. In the 16th century, near the time of his death, Nicolai Copernicus proposed the new idea of the heliocentric system. The Copernican system led to a simple explanation for varying brightness of the planets and retrograde motion. These occurrences could not be explained under the geocentric system. In class we discussed Epicycles. This article clearly demonstrates this concept. Uniform circular motion was often used to describe planets and was assumed to be likely for all planets. Planets, instead of orbiting circular, orbit in ellipses. However, the Copernican system did require fewer epicycles because it moved the Sun to the center of the solar system. The article then continues to support the Copernican system and refute the geocentric system. This article is very comparable to what we exercised in class regarding retrograde motion and the heliocentric model. This article has made this objective more clear to me. The information presented in this article is listed precisely in a way that is easy to understand. The clearness of this article is great because this concept/objective can be difficult to comprehend for some.