By what assumptions of uniform, ordered, circular motions may we save the appearances?
-Plato
Note: The next two lectures follow the timeline from ancient Greece to the Renaissance. Study the timeline, which summarizes the major names and ideas presented in the first part of your textbook.
Note: These lectures-- like the textbook-- tend to be Greek-Western-centric. For to treat every culture's historical development of astronomy (e.g., the Incan Quipu) would require a separate course.
picture of the Mathematical Mystic.
Cosmos arranged in Crystalline spheres (one, two)
(causing Music of the Spheres)
Note: even in our new millenium much is number
(e.g., mp3, DVD, iPod, wi-fi, the Matrix, and of course even this computer where you are now trained)
Video podcast of Pythagoras and his guitar.
Since Plato believed no true knowledge could be transmitted via books or print, but only through one-on-one dialogues, I refrain from putting much here. Thus I will "dialogue" about Plato in my class lectures.
Aristotle and his mentor Plato (picture1, picture2)
Physics: 4 (or 5) elements model of the Geocentric Cosmos. (picture).
In turn, Aristotle was mentor to Alexander the Great.
Hipparchus' model "saved the appearances" of retrograde motions (c.f., lecture–1 movie and Chaisson Fig.2.4) by retaining uniform circular motions.
Eccentric, Deferent and Epicycle (Chaisson Figs. 2.6 and 2.7) used to explain retrograde motions of planets
See the retrograde simulator
Author of first astronomy textbook: Almagest (picture)
Complete geocentric model of cosmos, adding "equant" to Hipparchus' model
Model predicts planetary motions to accuracy of 5° or less (!)
Model survived for over 1000 years (!!)
Summary of Ptolemaic model
Chaisson: Chap 1,2
The timeline shown in class.
The Galileo Project from Rice University is great source of information on early astronomers discussed here.
Wolfram Research hosts an online Scientific Biography.
Note: For the advanced and/or bored student, see The Exact Sciences in Antiquity by O. Neugebauer and learn how to do math like an ancient Egyptian; e.g., compute heliacal rising times of Sirius using fractions so you can predict for the farmers when the Nile will begin its yearly flood.
Note: in another Pythagorean model all the Cosmos-- including Sun-- revolves about a "Central Hearth." The model also includes a "Counter-Earth" hidden behind the Hearth-- so that total number of objects would add up the complete, or perfect number 10. Odd as this sounds, to this day some folks talk of a hidden planet.
Document URL: http://www.uh.edu/~jclarage/astr3131/lectures/2/2.html
