topic 7 Flashcards
What is the geocentric model?
an ancient cosmological model that places the Earth at the center of the universe. According to this model, celestial bodies such as the Sun, Moon, planets, and stars orbit around the Earth.
Who came up with the geocentric model?
Claudius Ptolemy
What were the issues with the geocentric model?
retrograde Motion: One of the most notable challenges for the geocentric model was explaining the retrograde motion of planets. Retrograde motion refers to the apparent backward motion of planets in the sky, as observed from Earth. The geocentric model attempted to explain this phenomenon by introducing complex systems of epicycles and deferents, but these explanations became increasingly convoluted as observations became more precise.
Inaccuracies in Planetary Positions: Despite the intricate system of epicycles and deferents, the geocentric model failed to accurately predict the positions of planets in the sky over time. As observational techniques improved, discrepancies between the model’s predictions and actual observations became more apparent.
what are epicycles?
Epicycles are like loops added onto bigger loops to explain why planets sometimes seem to go backward in the sky from Earth’s perspective.
what were the advantages of the addition of epicycles, as described by Ptolemy
Explanation of Retrograde Motion: Epicycles helped explain the phenomenon of retrograde motion, where planets appear to move backward in the sky relative to Earth’s motion. By adding small circular motions (epicycles) to the larger circular orbits (deferents) of planets, astronomers could account for these apparent reversals in motion.
predictive Accuracy: The addition of epicycles allowed astronomers to refine their predictions of planetary positions in the sky. By incorporating the complex motions of epicycles within the geocentric model, they could better match their calculations with observed celestial phenomena.
what is the heliocentric model
Sun-Centered: In the heliocentric model, the Sun is positioned at the center of the solar system, with the planets, including Earth, orbiting around it.
Planetary Orbits: Instead of moving in complex paths around Earth, as in the geocentric model, planets orbit the Sun in relatively simple elliptical paths. This concept laid the foundation for Kepler’s laws of planetary motion.
Rotation of Earth: Copernicus proposed that Earth rotates on its axis daily, causing the apparent motion of celestial bodies across the sky. This rotational motion of Earth helps explain phenomena such as the rising and setting of the Sun and stars.
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