The Ordered Universe The Birth of Modern Astronomy (Trefil & Hazen, The Sciences, Ch 2)

Homer’s “Bear that never bathes”

Stonehenge …one of several old “time-reckoning” machines. It’s moving parts are in the sky. Ancient astronomy

Great Pyramid of Giza …was aligned to the pole star, and it was possible to read the seasons from the position of the pyramid’s shadow.

The Mayans of Yucatan …inscribed stone monuments with formulae for predicting solar eclipses

Plains Indians Recorded the rising points of the bright stars, to record seasonal grazing patterns.

Political Power …Columbus influenced native people to provide food for his crew by warning of “an inflamed and angry moon.”

Brief Overview of Early Science Greece, 4 th C B.C. Roman Empire Fell, 5 th C A.D. Chinese, Polynesians, Arabs Islamic influences in Spain th C Universities emerge in Europe, 13 th C Printing press, 15 th C Copernican hypothesis heliocentrism 15 th C Galileo and “scientific method” 17 th C

The Ordered Universe Part 1: Ancient Astronomers

Ancient China Working calendar 13 th Century B.C.! Star Catalog with 800 entries, 350 B.C.! Observed comets and supernovas

Babylonian Astronomy Oldest scientific documents 800 B.C. Record eclipses, positions of planets and rise/setting of the Moon

Greek Astronomy 600 B.C. to 200 A.D. Thales introduced geometrical ideas into astronomy. Pythagorus universe as a series of concentric spheres Eudoxus the idea of rotating spheres to account for the observed complexities of planetary motions. Aristotle correct explanation of lunar eclipses; sound argument for the spherical shape of the earth.

Astronomy at Alexandria 3 rd Century B.C. Aristarchus Determined size and distance of Sun and Moon rel to Earth Developed 1 st heliocentric model Eratosthenes Made accurate calculation of the size of the Earth

Claudius Ptolemy Greek astronomer from 2 nd Century, proposed first enduring theory of the universe, an Earth-centered or Geo-centric model.

Occam’s Razor and interpreting oddities 14 th Century English Philosopher Given a choice, the simplest solution to a problem is most likely to be right.

Stonehenge

The Ordered Universe Part 2: Birth of Modern Astronomy The “Fab. Four” Copernicus, Brahe, Kepler, Galileo

Figure 2-5 The Ptolemaic (a) and Copernican (b) systems both assumed that all orbits are circular. The fundamental difference is that Copernicus placed the Sun at the center. (a)(b)

Mikolai Kopernik, 1473 Copernicus outlined a theory for a sun-centered or “heliocentric” universe 1543, On the Revolutions of the Spheres

Tycho Brahe,

Johannes Kepler,

Kepler’s Laws Planets orbit the sun in an ellipse. planets move more rapidly when close to the sun and more slowly when distant from the sun The cube of the mean distance of each planet from the sun is proportional to the square of the time it takes to complete one orbit

Check your neighbor… Summarize key ideas of our attempt to make sense of the universe –Ancients of China, Egypt, Greece –Aristarchus –Eratosthenes –Ptolemy –Copernicus –Brahe –Kepler