Download Aristotle Eratosthenes 350 250 Archimedes Aristarchus Ptolemy

Ptolemy’s Model of the Universe (Geocentric)
400
400
350
- Abandoned Aristotle’s linkage of the motion of celestial spheres with one another
- Calculation of motion must match observation.
( There was enough good historical data to show that the heavens were
changing. What was most important was accurate navigation tables
and calendars)
Plato
Aristotle
Aristarchus
280
Eratosthenes
250
Archimedes
240
0
150
- Preserved the idea of circular orbits but incorporated eccentrics and epicycles
to account for observed changes in heavenly objects.
Ptolemy
Planet
Planet
Copernicus
1520
Tyco Brahe
1580
Galileo
1600
Kepler
1630
Earth
Earth
Eccentric
Copernicus’ Model of the Universe ( Heliocentric)
- Revived Aristarchus’ idea of a sun centered unvierse
- Did not like the complexity of Ptolemy’s model
- Seemed more reasonable to have the earth rotate than the celestial sphere
( The speeds of the stars would have to be unbelievably high )
-
Moon circled the earth
o
Earth rotates on tilted axis of 23.5 in 23 hr. 56 min.
Had an idea that the earth’s axis was rotating about the orbital axis
Calculated the ratios of the planetary distances to the sun
Calculated the earth - sun distance to be 4.8 million miles
- Copernicus’ model gave poorer results than Ptolmey’s for predicting the
positions of heavenly objects
- Model modified using some of Ptolmey’s ideas
(46 spheres rather than 70)
Tyco Brahe’s Model of the Universe
- Earth is the centre of the universe
- Sun and moon orbit the earth as do the stars (circular orbits )
- Planets orbit the sun
- Earth is motionless
-
Knew there were serious problems with both Copernicus’ and Ptolmey’s models
Gathered new data (no telescope) (20 years of work tracking planets etc.)
Data was accurate to 4 minutes of arc
Did not finish the model, charged is assistant Kepler to do the calculations
Epicycle
Objections to Copernicus’ Model
Scientific
- No stellar parallax was observed
- Apparent size of the stars would be too large
- If earth is in motion where is the wind?
- If earth is rotating why do falling objects appear to fall straight down?
- If earth is rotating why are we not flung off the earth (centrifugal force)
- What power keeps the earth in motion?
Philosophical and Theological
- Did not agree with a literal interpretation of the Bible
- A sun centered universe was a Pagan idea (sun worship)
- Earth was not perfect, therefore was not like a planet