The Heliocentric Theory

Background: Geocentric Theory• Geocentric Theory: that the

earth is the center of the solar system (and universe)

• Geocentric theory reflected both the prevailing world view, and desire to explain world mathematically

• Heavenly bodies inhabited spheres encapsulating the earth, with God and angels outside (Circles/spheres were considered divinely perfect)

• Epicycles explained anomalous observations of orbits

Copernicus (1473-1543, Poland)• Heliocentric Theory: that

the sun is the center of the solar system

• Each heavenly body inhabited a sphere encapsulating the sun

• Simplified the Ptolemaic theory: epicycles still required, but smaller

• Increased mathematical elegance in accounting for observations justified the theory

• 1543: On the Revolutions of the Heavenly Spheres

Brahe (1546-1601, Denmark)

• Geocentric theory, but with modifications:

• sun and moon orbited the earth; remaining planets orbited the sun

• (Tyco had a pet moose)

Johannes Kepler (1571-1630, Germany)

• Used Brahe’s observational data to support heliocentric theory, but with elliptical orbits

• 1609: The New Astronomy

• No answer to problem of why planets orbited elliptically, or why they didn’t hurtle off into space

Galileo (1564-1642, Italy)

• First use of the telescope to study astronomy

• 1613: Starry Messenger argued for a Copernican interpretation (heliocentric)

• Fitted close astronomical observation with mathematics; believed in rational, mathematical explanation of physical universe

Isaac Newton (1642-1727, England)

• 1687: published Principia Mathematica: movement through mutual attraction, or gravity

• Developed calculus, which helped calculate quickly

• Invented many optical devices, including wide light-gathering telescope

• Emphasized the importance of empirical data and mathematical relationships

Conclusions• Heliocentric theory challenged

Europeans’ world view

– Were humans the most important element of the universe, if they weren’t physically at the center?

– Would God create a world for humans that wasn’t at the center?

– Was every sentence in the Bible literally true, or was interpretation necessary?

• Success of the heliocentric theory pointed to the value of

– mathematics in describing reality and making predictions based on theory

– observational tools to increase humans’ capacity to gather data

– man’s ability to explain reality mathematically

– math’s ability to simplify complex phenomena so that man can analyze and understand it

From Theodore Roosevelt’s history of the war