# Astronomy of the Earth's Motion in Space.

# 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**.

- Stargazers and Skywatchers
- The Path of the Sun, the Ecliptic
- Seasons of the Year
- The Moon: the Distant View
- The Moon: A Closer Look
- Optional: Libration of the Moon

- Latitude and Longitude
- The Calendar
- The Jewish Calendar (optional)

- Precession
- The Round Earth and Christopher Columbus
- The central role of the Sun
- Kepler and his Laws
- Graphs and Ellipses
- Kepler's Second Law

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