Finding Our Place in the Cosmos: From Galileo to Sagan and Beyond
Modeling the Cosmos
Ancient Greek Astronomy and Cosmology
As the stars move across the sky each night people of the world have looked up and wondered about their place in the universe. Throughout history civilizations have developed unique systems for ordering and understanding the heavens. Babylonian and Egyptian astronomers developed systems that became the basis for Greek astronomy, while societies in the Americas, China and India developed their own.
Astronomical Innovation in the Islamic World
Between the 8th and 15th centuries Islamic astronomers produced a wealth of sophisticated astronomical work. Largely through the Ptolemaic framework, they improved and refined the Ptolemaic system, compiled better tables and devised instruments that improved their ability to make observations. The extensive contributions of Islamic astronomy also exposed some weaknesses in the Ptolemaic and Aristotelian systems.
Whose Revolution? Copernicus, Brahe & Kepler
Copernicus is often described as a lone astronomer who defiantly argued that the sun, not the Earth was at the center of the cosmos. Copernicus' contributions to astronomy are so significant that they warrant their own term: The Copernican Revolution.
Galileo and the Telescope
The invention of the telescope played an important role in advancing our understanding of Earth's place in the cosmos. While there is evidence that the principals of telescopes were known in the late 16th century, the first telescopes were created in the Netherlands in 1608. Spectacle makers Hans Lippershey & Zacharias Janssen and Jacob Metius independently created telescopes. The telescope emerged from a tradition...
Physical Astronomy for the Mechanistic Universe
Aristotelian cosmology was still present in 17th century understanding of the cosmos. This section briefly explores the contributions of Rene Descartes and Isaac Newton to the development of a new mechanical model for describing the relationship between heavenly bodies. In continental Europe, Rene Descartes theory of vorticies served as a powerful conceptual tool for theorizing the nature of the heavens. In England, Isaac Newton...
Competing Cosmological Models
In 1543, Copernicus suggested the sun was at the center of the cosmos. However, it was centuries before a sun-centered model became widely accepted. The history of science is often thought of as a procession of discoveries and advances. This obscures the complex stories of how theories and models can compete and coexist over long periods of time. When the Copernican model eventually won...
Stars as Suns & The Plurality of Worlds
What does it mean for a planet to be a world? How did we come to understand that our sun is just another one of the stars? Many are familiar with the shift from an earth-centered cosmos to a sun centered one. In parallel to that story, there is a story of a plurality of worlds and the realization that each star in the...
The Milky Way: One of the Many Galaxies
The idea that each star is a sun, many with their own solar systems, is a powerful reminder of the immense scale of the cosmos. However, the distances to stars in our galaxy are tiny in comparison to distances to other galaxies.