The Copernican Revolution shook up our view of the cosmos. It replaced Earth-centered models with a sun-centered system, explaining planetary motions more elegantly. This shift laid the groundwork for modern astronomy and challenged long-held beliefs.

Galileo's observations with the telescope provided crucial evidence for the heliocentric model. He spotted Jupiter's moons, Venus's phases, and the moon's rough surface. These findings, along with his work on motion, paved the way for Newton's laws and a new understanding of the universe.

The Copernican Revolution

Copernicus' heliocentric model

• Proposed sun-centered model of the solar system
  • Sun at the center, Earth and planets orbiting around it
  • Contrasted with prevailing Earth-centered models (geocentric)
• Significance of heliocentric model:
  • Challenged long-held belief of Earth as center of universe
  • Provided more elegant and simplified explanation for apparent motions of celestial bodies (planets, stars)
  • Laid foundation for development of modern astronomy

Heliocentric vs geocentric models

• Geocentric models (Ptolemaic model):
  • Earth at center of universe, sun, moon, and planets orbiting around it
  • Required complex systems of epicycles to explain apparent retrograde motion of planets (Mars, Jupiter)
• Copernican heliocentric model:
  • Sun at center, Earth and planets orbiting around it
  • Explained retrograde motion of planets as natural consequence of their orbits around sun
  • Eliminated need for epicycles, providing simpler and more elegant explanation
• Johannes Kepler refined the heliocentric model by introducing elliptical orbits, improving its accuracy

Galileo's Contributions

Galileo's astronomical observations

• Used newly invented telescope to make groundbreaking observations:
  • Discovered four moons orbiting Jupiter, demonstrating not all celestial bodies orbit Earth
  • Observed phases of Venus, could only be explained by planet orbiting sun
  • Discovered sunspots, challenging notion of sun as perfect, unchanging celestial body
  • Observed rough, mountainous surface of moon, contradicting belief in perfect celestial spheres
• Observations provided strong evidence supporting Copernican heliocentric model
  • Challenged Aristotelian and Church-supported view of universe
  • Demonstrated Earth not center of all celestial motions

Galileo's contributions to astronomy

• Studies of motion and forces laid groundwork for Newton's laws of motion and universal gravitation
  • Investigated motion of falling objects and projectiles (cannonballs)
  • Developed concept of inertia, object in motion remains in motion unless acted upon by external force
• Work on motion and forces:
  • Helped explain orbits of planets and moons in solar system
  • Provided foundation for understanding behavior of celestial bodies
  • Contributed to development of mechanistic view of universe, essential to modern astronomy
• Pioneered the use of the scientific method in astronomy, emphasizing observation and experimentation

Advancements in Astronomical Understanding

Kepler's Laws and Observational Data

• Kepler's laws of planetary motion:
  • Described the elliptical orbits of planets around the sun
  • Explained the varying speeds of planets in their orbits
  • Provided a mathematical framework for predicting planetary positions
• Tycho Brahe's precise observational data:
  • Collected extensive and accurate measurements of planetary positions
  • Provided crucial data for Kepler to formulate his laws
• Stellar parallax:
  • Observed apparent shift in position of nearby stars relative to distant stars
  • Provided direct evidence for Earth's motion around the sun, supporting the heliocentric model