History of Astronomy

Ptolemy- the “P” is silent Used the observations of ancient astronomers to come up with a ___________________ model of the universe. His model became the accepted explanation of the universe for the next _______ centuries. This model did not create any _________________ or _______________________issues and was widely accepted.

Ptolemy’s Model

Retrograde Motion and Epicycles ______________________ motion is the apparent “___________________” motion of a planet when viewed from Earth. Early models of the universe, including Ptolemy’s, explained this by adding ________________, or _________________ circles of planetary motion within the large circle of its ________________around the Earth.

Retrograde Motion of Mars

Nicolaus Copernicus Believed that a simpler model of the universe would make more sense, and suggested that the sun was at the ______________, and not the Earth. ___________ orbited in circles around the ____________. Due to some minor irregularities, Copernicus did add some epicycles to explain the data.

Nicolaus Copernicus Did not publish his ideas until he was on his ______________ because he feared criticism and ridicule from scientists and the _________________. The church did not take his work seriously when it was first published and did not take much _______________ of it.

Copernicus’ Model

Retrograde Motion and Copernicus’ Model

Galileo Galilei Galileo was the first astronomer to use a ___________________ to study, in detail, celestial objects. His telescope showed that the sun and the moon were not “______________” heavenly bodies, as many people thought. He observed ____________ on the moon and ________________ on the sun. His observations also showed that the sun ______________ and was not stationary.

Galileo Galilei Defended the ___________________ model of the universe and publicly __________________the earlier (and still widely believed) geocentric view of the solar system. When Galileo started to provide strong observational evidence for ___________________, the church took noticed and eventually convicted him of _____________________(going against the proclaimed doctrine of the church). Galileo spent the remainder of his life under house arrest for his “________________.”

Tycho Brahe Collected vast amounts of _______________________ data without using a________________. His model attempted to combine the ______________________ logic of Coperincus’ heliocentric model with Ptolemy’s more widely accepted ___________________________ model in order to avoid conflict with _______________________.

Tycho Brahe ____________________________ Was a keen accurate ______________ and note taker Measured the position of _______stars without a _______________________ Measured the position of the ________, ________________, and planets daily for almost _______ years.

Tycho Brahe’s Model All planets except Earth orbit the ___________ Moon and the sun (with all other planets) orbit the _______________ Stars are in a fixed ______________ around the whole system

“Tychonic” Model Tycho Brahe’s model was used favorably for quite some time, since it did not go against religious teachings, explained all observational _________, and eliminated the need for confusing ______________________.

Johannes Kepler A student of Tycho Brahe’s, _______________ used the extensive data to come up with his model. Kepler determined that the orbits of the planets must be slightly ___________________, or similar to an _____________ shape. An ellipse has two center points, called ______________. The __________is at one focus in Kepler’s model.

Kepler’s Model Fit observational data perfectly No need for epicycles

Acceptance of Model Kepler’s model was not immediately accepted. Even Galileo thought __________________ orbits were improbable. Many people objected, on philosophical grounds, to the use of _______________ to explain the _______________ of heavenly bodies. Kepler’s model is the basis of our current understanding of ______________________ motion (with only minor changes).