Heliocentric Model Summary

Geocentric Model:
- Earth is at the center of the universe.
- Proposed by Aristotle around 300 BCE.
- Ptolemy expanded this model, incorporating epicycles to explain the movements of celestial bodies.
Heliocentric Model:
- The Sun is at the center of the universe.
- Proposed by Aristarchus.
- Copernicus, Galileo, and Kepler refined this model, leading to its acceptance.

Copernicus:
- Rediscovered the heliocentric model.
- Proposed that only the Moon orbits Earth, while all other planets orbit the Sun.
- Simpler explanation compared to Ptolemy's geocentric model.
Galileo Galilei:
- Observed the moons of Jupiter, providing evidence that not all objects orbit Earth.
- Observed the phases of Venus, supporting the idea that Venus orbits the Sun.
- His findings contradicted the Church's teachings, leading to his house arrest.
Johannes Kepler:
- Demonstrated that planetary orbits are elliptical, not circular.
- Developed three laws of planetary motion based on Tycho Brahe's data.
- Showed that planets move at varying speeds, faster when closer to the Sun.

Sun:
- The star at the center of our solar system.
Planets:
- Mercury, Venus, Earth, Mars (terrestrial planets).
- Jupiter, Saturn, Uranus, Neptune (gas giants).
Dwarf Planet:
- Pluto
Comets:
- Small objects made of ice and dust that orbit the Sun.
Asteroids:
- Small, rocky objects that orbit the Sun, mostly located between Mars and Jupiter.
Meteoroids:
- Small chunks of rock and metal debris in space.
- Become meteors when they enter Earth's atmosphere; meteorites if they hit the surface.

Asteroid: Small rocky object orbiting the Sun.
Celestial: Relating to the sky or space.
Comet: Icy and dusty object orbiting the Sun.
Epicycle: A small circle whose center moves along the circumference of a larger one.
Geocentric: Earth-centered view of the universe.
Heliocentric: Sun-centered view of the universe.
Meteoroid: Small rock or metal debris in space.