1. Origins of Modern Astronomy
- Ancient and Modern Astronomers -

2. A paradigm is a set of ideas or a way of looking at the world.
I. Paradigm Shifts
What’s a paradigm?
A paradigm is a set of ideas or a way of looking at the world.
Ex. For a long time, predator/prey relationships were viewed as the food chains.
Now, we talk about “food webs”.

3. I. Paradigm Shifts What’s a paradigm in astronomy?
Knowledge of the universe was often seen as a revelation handed down by prophets.
Now, we accept the concept of observational science.

4. Aristotle II. Early Astronomers Greek who lived from 384 -322 BC
1. He studied and lectured on…everything
2. He was a student of Plato.
Plato’s concept was that the sphere was perfect. The Earth must be at the center of many spheres.
3. He introduced the idea of a geocentric universe.

5. B. Eratosthenes 276 to 194 BC calculated Earth’s circumference
Greek mathematician
calculated Earth’s circumference
paid a servant to walk from Alexandria to Syene – about 500 miles.
on the summer solstice, the sun cast a slight shadow in a well in Alexandria but no shadow in Syene.

6. C. Ptolemy 140 AD in Alexandria
Built on Aristotle’s work
- developed the concept of Geocentrism.
- had a problem with retrograde motion of some objects (Mars)
About the same time, a man named D. Aristarchus developed the idea of Heliocentrism.

7. Aristotle, Ptolemy, and the Geocentric Theory https://www. youtube

8. The Middle Ages
At the end of this era, Europe entered the Middle Ages….
The Middle Ages: after the fall of the Roman Empire and before the Renaissance

9. The Middle Ages
During this time, there was a lack of scientific and material advancements, written history, and recorded literature - this period is sometimes referred to as the “Dark Ages”
Somewhat a misnomer…
Knowledge of science & stars is lost…
However, Arabic scholars managed to save much of this knowledge of the heavens – Islamic Golden Age

10. E. Copernicus AD
Published a book “On the Revolutions of the Celestial Spheres” on his death bed.
This led to the Copernican revolution and heliocentrism.

11. F. Tycho Brahe 1546 – 1601 AD Royal astronomer to the Dutch Court
Made precise astronomical observations of Mars for 20 years.
Believed in Geocentrism
Hired J. Kepler as his understudy

12. G. Johannes Kepler 1571 – 1630 AD
Stole Tycho’s work following his death.
Used the Mars observations to develop 3 planetary laws of motion.
1. Ellipses – all planets travel in elliptical orbits. The sun is one foci, the other foci is empty.
2. Equal Area – planets sweep out equal areas of
space in equal amounts of time.
3. The further a planet is from the sun, the longer it takes to orbit.

13. H. Galileo Galilei 1564 – 1642 AD
Believed in observation, not revelation.
First scientist to use a telescope for Astronomy:
Moon has craters & mountains
The sun has spots
Venus has phases just like our moon
Jupiter has its own satellites (moons)
He believed strongly in the Heliocentric model

14. H. Galileo Galilei 1564 – 1642 AD continued…
Galileo angered the Catholic Church with his teachings of heliocentrism.
He was placed under house arrest for the last 10 years of his life.

15. I. Sir Isaac Newton 1642 - 1727 Studied Physics “cannon ball physics”
watch?v=51mxBkwwSB8
how-orbits-work/en/

16. I. Sir Isaac Newton 1642 - 1727
He proposed - - Laws of motion - Universal gravitation - Built a reflecting telescope with eye piece. “Newtonian Telescope”