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Early Models of the Universe - Geocentric and Heliocentric Models | Physical Science | Astronomy

Models of the Universe#Geocentric#Heliocentric#Retrograde Motion#Stellar Parallax#Laws of Planetary Motion
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Ancient beliefs about Earth's shape evolved from flat to spherical, with Greek philosophers like Pythagoras and Aristotle contributing to the idea of a spherical Earth. Aristarchus proposed a heliocentric model, but Ptolemy's geocentric model prevailed until Copernicus revived the heliocentric model. Galileo's observations and Kepler's laws of planetary motion further supported a sun-centered system with elliptical orbits. The laws of equal areas and period describe how planets orbit the sun in predictable patterns.

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Evolution of Earth's Shape Beliefs
Greek philosophers such as Pythagoras and Eratosthenes played a role in the transition from the flat Earth belief to the spherical Earth concept.
Various philosophers proposed geocentric and heliocentric models of the universe.
Early astronomer Eudoxus explained retrograde motion and planetary movements, advocating for a universe where visible planets orbited Earth.
Aristotle's model placed a stationary Earth at the center of the universe, with celestial bodies moving symmetrically around it.
The debate between heliocentrism and geocentrism in ancient astronomy.
Aristarchus of Samos proposed a heliocentric model with Earth and other planets revolving around the sun, opposed by Aristotle and many philosophers.
Claudius Ptolemy's geocentric model placed Earth at the center and explained celestial motion accurately, including retrograde motion.
Tycho Brahe observed planets and believed in a geocentric universe with slight variations from Ptolemy's model.
Key highlights on the contributions of Copernicus, Galileo Galilei, and Johannes Kepler to modern astronomy.
Copernicus revived the heliocentric model of the universe and faced fear of condemnation before publishing his findings.
Galileo Galilei proved the Copernican hypothesis and observed that distant stars do not exhibit parallax.
Johannes Kepler mathematically showed that a sun-centered system works well with predictable motion along off-center ellipses.
Kepler's three laws of planetary motion include the law of ellipses, describing the orbit of planets in ellipses rather than perfect circles.
Laws of Planetary Motion.
Planets move in an elliptical path around the sun, with perihelion as the closest point and aphelion as the farthest.
The law of equal areas states that a planet covers equal areas in equal times as it orbits.
The law of period, or harmonic law, states that the period of revolution of a planet around the sun is proportional to the cube of the average distance from the sun.