History of Astronomy. How did we get to where we are today? We stand on the shoulders of giants. Greek, Egyptian, Asian, European, Islamic, Indian scientists all observed the heavens and tried to explain what they saw What did the ancients know? And how did they know it?
Great Pyramid of Giza
Astronomical alignments built in to the pyramid
There is geometry in the humming of the strings... there is music in the spacing of the spheres.
How did classical astronomers explain this strange backwards motion?
Ptolemy attempts to explain retrograde
motion by hypothesizing that the planets
move in circles within circles…
…his theories remained in use for another
1500 years, until it became too complex to
be physically meaningful
Distances to even nearest stars are so huge, stellar parallax is a VERY small
quantity, and so could not be measured until the middle of the 19th century!
Evidence for heliocentric model existed, but was just outside our grasp to
“Absence of evidence is not evidence of absence.”
At last, a simple & accurate
model for predicting
P2 years = a3 AU
equal areas in
Sun at one focus
Kepler’s Laws are empirical, which means they are based on actual data &
measurements, not just theory…
The phases of Venus,
As observed from Earth
No matter what configuration,
epicycles cannot explain
the phases of Venus…
More on Newton and his Laws later…