Lecture Series: History of Astronomy

Lecture Overview

• Focus on ancient astronomy
• Discuss geocentric model (Earth-centered) and flat Earth model
• Explore the scientific method in astronomy
• Importance of critical thinking and skepticism

Understanding the Universe

• Modern tools improve our understanding (telescopes, etc.)
• Knowledge developed primarily in last few hundred years
• Significant discoveries: other galaxies (1923), first black hole image (2019)

Ancient Astronomy

• Early astronomers were religious figures
• Astronomy linked to astrology for thousands of years

Astronomy in Ancient Civilizations

• Writing and mathematics essential for proper astronomy
• Babylonians and Egyptians developed calendars for agriculture
• Babylonian records predicted lunar eclipses
• Ancient Chinese astronomers documented solar eclipses and other phenomena
• Historical data from ancient cultures still used today

Axial Precession

• Discovered by Hipparchus (~150 BC)
• Changes position of the north celestial pole over time
• Earth's axis precesses every 25,700 years

Spherical Earth

• Ancient Greeks proved Earth was spherical ~2500 years ago
• Evidence includes lunar eclipses, observation of new stars, and circumnavigation of the Earth
• Eratosthenes' experiment to measure Earth's circumference

Geocentric Model

• Belief in Earth-centered universe until 17th century
• Geocentric view supported by religions and lack of perceived Earth movement
• Heliocentric model (Sun-centered) proposed by Aristarchus rejected initially

Stellar Parallax

• Demonstrates Earth's movement around Sun
• Ancient Greeks couldn't detect parallax due to insufficient technology

Ptolemy's Geocentric Model

• Introduced in Almagest
• Used for over 1400 years
• Explained retrograde motion with epicycles

Modern Understanding

• Heliocentric model with elliptical orbits explains planetary motion
• Simple models preferred (Occam's Razor)
• Scientific model usefulness based on explanatory power

Conclusion

• Science replaces incorrect hypotheses (geocentrism, flat Earth)
• Need for skepticism against anti-scientific beliefs
• Next lecture focus: astrology

Reading and Practice

• Refer to section 2.2 of the textbook
• Practice questions will be posted on TIMSS