1. Ch.1, Sec.1 – Astronomy
- some of the earliest civilizations used astronomy to create calendars, necessary for planting crops effectively (Mayans)
astronomy: the study of the Universe
Our Modern Calendar
year: the time required for the Earth to orbit (one revolution) once around the Sun ( days)
month: a division of the year that is based on the orbit (one revolution) of the Moon around the Earth (29.53 days)
day: the time required for Earth to rotate once on its axis (23 hours, 56 minutes)

2. Ch.1, Sec.1 – Astronomy
- The Mayans knowledge of astronomy allowed them to create structures, like Chichen Itza, where the Sun’s movement on the equinoxes (March 20 & September 22) casts a perfect shadow of one of their gods – Kukulkan!

3. Ch.1, Sec.1 – Astronomy Who’s Who of Early Astronomy
1. Ptolemy – the first astronomer to create a solar system model, but he was incorrect by having Earth at the center of the Universe (A.D. 140)

4. Ch.1, Sec.1 – Astronomy
2. Nicolaus Copernicus – the first astronomer to create an accurate solar system model and had the Sun at the center of the Universe (A.D. 1543)

5. Ch.1, Sec.1 – Astronomy
3. Tycho Brahe – favored the Ptolemaic theory of an Earth centered Universe, but did make significant observations regarding the planets and stars (A.D. 1500s)

6. Ch.1, Sec.1 – Astronomy
4. Johannes Kepler – favored Copernicus’ Sun-centered Universe and created three laws of planetary motion (elliptical orbits)

7. Ch.1, Sec.1 – Astronomy
5. Galileo Galilei – became the first astronomer to use a telescope and observed distinct features from the moon and the planets

8. Ch.1, Sec.1 – Astronomy
6. Isaac Newton – showed how gravitational force attracts everything in the Universe including planets orbiting the Sun (smaller objects are attracted to larger objects)

9. Ch.1, Sec.1 – Astronomy Modern Astronomy
- In 1924, Edwin Hubble was able to view other galaxies other than the Milky Way, thus proving the Universe is much bigger than expected