Ancient and Greek Astronomy Overview

Ancient Times

• Stonehenge, located in southern England, was constructed in stages from 2800 BC to 1075 BC; used to track the sun and moon for calendar purposes
• Big Horn Medicine Wheel, situated in Wyoming's Big Horn Mountains, is an arrangement of rocks forming a 28-spoked wheel. Plains Indians used it as a calendar from 1500 to 1700 AD
• Caracol Temple, located on the Yucatan Peninsula, is a 1000-year-old astronomical observatory

Greek Astronomy

• Greek astronomy was influenced by Babylonian and Egyptian astronomy, which focused on astrology
• Plato (427-347 BC) believed reality was a distorted shadow of a perfect form, particularly circles
• Aristotle (384-322 BC) proposed the Earth was a sphere, based on observations of ships at sea and lunar eclipses
• Aristarchus (ca. 200 BC) theorized that the Earth rotates on its axis and orbits the Sun
• Eratosthenes (ca. 200 BC) developed a method for determining Earth's circumference with surprising accuracy
• Hipparchus (ca. 150 BC) created the first star catalog, cataloging stellar magnitudes.
• Ptolemy (ca. 100 AD) preserved Aristotelian geocentric views, modeling them with sophisticated calculations to account for the movements of planets

Pioneers of Astronomy

• Copernicus (1473-1543): proposed a heliocentric (sun-centered) model of the solar system in 1507, but hesitated to publish it due to Church influence

• Published De Revolutionibus in 1543 (sun-centric)

• Explained retrograde motion without epicycles

• Tycho Brahe (1546-1601): developed instruments to observe celestial bodies, meticulously documented planetary positions, and created the Rudolphine Tables (planetary positions)

• Johann Kepler (1571-1630): used Brahe's data to derive three laws of planetary motion:

  • Planets orbit in ellipses with the Sun at a focus.
  • A line joining a planet and the Sun sweeps out equal areas during equal intervals of time.
  • The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.

• Galileo Galilei (1564-1642): made systematic observations of celestial bodies using a telescope.

  • Confirmed heliocentric theory
  • Observed craters and mountains on the Moon
  • Observed the Milky Way as a collection of stars, many unseen by the naked eye
  • Disproved the concept of celestial perfect spheres
  • Discovered Jupiter's Moons ("Galilean Moons")
  • Observed phases of Venus

Isaac Newton (1642-1727)

• Developed three laws of motion
  • A body continues in motion in a straight line at a constant speed or remains at rest unless acted upon by some external force.
  • A body's change of motion is proportional to the force acting upon it and in the direction in which the force acts.
  • When one body exerts a force on a second body, the second body simultaneously exerts an equal and opposite force on the first body
• Introduced the law of universal gravitation, explaining how all massive objects attract each other
  • F=GMm/r², where F is the force of attraction, G is the gravitational constant, M and m are the masses of the objects, and r is the distance between them.

Explore the fascinating developments in ancient and Greek astronomy, covering structures like Stonehenge and Caracol Temple. Understand how early astronomers like Plato and Aristotle shaped our views of the cosmos. This quiz highlights key celestial observations and calendar systems from various ancient cultures.