o Carved bone 8500 years old of crescent moon found in Africa (one of the
o Predicted seasons from orientation of horns of crescent moon each month
o 2500BCE, Egyptians used first rising at dawn of star Sirius (brightest star)
to mark the beginning of a 365day calendar… it identified with the
fertility goddess Iris, appeared in predawn sky every year as Nile began its
life giving floods happened yearly. That’s how they predicted their
planting season and prepare for floods
o Egyptians also divided night and day into 12 hours.
o Sun was used for predicting seasonal changes and lunar phases
o Stonehenge giant boulders aligned with seasonal motion of the sun
o Babylonians (first female astronomer was named that moon goddess) she
was astronomer priestess of potamia….
o Chinese people made earliest known supernova explosion and recorded
solar and lunar eclipses (it was powerful enough to be brightest than Venus
and visible during the day for 23 days)
*Birth of astrology search for influences on human lives based on positions of planets
and stars in the sky.
- Ancient philosophers and astronomers accepted without question – as first
principles – that heavenly objects must move on circular paths at constant speeds,
and that the Earth is motionless at the center of the universe.
- Aristotle believed that the heavens were perfect. All motion in the perfect heavens
must be caused by the rotation of spheres carrying objects around in uniform
- Claudius Ptolemy made a mathematical model from Aristotle’s view. However, he
had to move Earth slightly offcenter and as the centuries passed errors in the
- Geocentric universe: a model universe with Earth at the center, such as the
- Heliocentric universe: a model of the universe with the sun at the center, such as
the Copernican universe
- Nicolaus Copernicus was the first person to produce a detailed model with
substantial justifying arguments for a heliocentric universe - In Copernicus’s model, Earth moves faster along its orbit than the planets that lie
farther from the sun
- Even though his model correctly put the sun at the center of the solar system, it
could not accurately predict the positions of the planets as seen from Earth.
Copernicus even had to reintroduce small epicycles to match minor variations in
the motions of the sun, moon and planets
- The Coperican model is inaccurate. It includes uniform circular motion and thus
does not precisely describe the motions of the planets. But the Coperican
hypothesis that the solar system is heliocentric is correct
- Backward motion of planets is called retrograde motion
- Claudius Ptolemy created a mathematical model of the Aristoelian universe in
which the planet followed a small circle called the epicycle that slid around a
larger circle called the deferent. By adjusting the size and rate of rotation of