Astronomy of the Earth's Motion in Space.

August 27, 2010, 5:55 pm

I.   Astronomy of the Earth's Motion in Space

An algebra-based overview of elementary and (mostly) pre-telescope astronomy, for personal study, also for middle school (some), high school (mostly) and beginning college.

Starting with the apparent motions of the Sun and stars on the celestial sphere, it explains the seasons of the year, latitude and longitude, time zones and universal time, and the basics of navigation.

Next calendars are described--Julian and Gregorian, Metonic (esp. Jewish), Moslem, Persian and even Maya.

After that the site tells how the spherical shape of the Earth was recognized and measured, leading to the formula for the distance of the horizon, the concept of parallax and the ways the ancient Greeks estimated the distance of the Moon.

The Greeks also tried to derive the distance of the Sun, starting the road to heliocentric theory, with roles by Ptolemy, Copernicus, Galileo and Kepler.

The section ends with a fairly detailed discussion of Kepler's laws and planetary orbits, which serves as a bridge to the next section, on Newtonian Mechanics.

Interspersed with the above are three web pages on the Moon (which may also be tied to the Greek calculations of the Moon's distance) and one on the precession of the equinoxes, connected to the Milankovitch theory of ice ages.


  1.  Stargazers and Skywatchers
    1. The Celestial Sphere
    2. Finding the Pole Star
  2. The Path of the Sun, the Ecliptic
    1. Building a Sundial
  3. Seasons of the Year
    1. The Angle of the Sun's Rays
  4.   The Moon: the Distant View
    1. The Moon: A Closer Look
    2. Optional:  Libration of the Moon
  5. Latitude and Longitude
    1. Navigation
    2. The Cross-Staff
    3. Coordinates
  6. The Calendar
    1. The Jewish Calendar (optional)
  7. Precession
  8. The Round Earth and Christopher Columbus
    1. Distance to the Horizon
    2. Parallax
    3. How Distant is the Moon?--1
    4. How Distant is the Moon?--2
  9. The central role of the Sun
    1. Aristarchus: Is Earth Revolving around the Sun?
    2. The Earth's Shadow
    3. Copernicus, Galileo, and the Discovery of the Solar System
  10. Kepler and his Laws
    1. The Scale of the Solar System
  11. Graphs and Ellipses
    1. Ellipses and Kepler's First Law
  12. Kepler's Second Law
    1. More on Kepler's Second Law
    2. How Orbital Motion is Calculated Optional: The 2004 Transit of Venus
    3. Halley's Method of Deriving the AU
    4. The displacement D of the track of Venus
    5. Deriving the Astronomical Unit




(2010). Astronomy of the Earth's Motion in Space.. Retrieved from


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