Astronomy is the study of...
all physical objects beyond Earth, examples: Moon, planets, stars, nebulas and galaxies!
System for organizing time!
solar (sun based), lunar (moon based) or solar/lunar (both)!
Time it takes for Earth to orbit the Sun once. (Approximately 365.25 days long!)
Approximately the time it takes the moon to orbit Earth once. (About 28 days long)
There are (blank) lunar cycles in one year!
Time it takes for the Earth to rotate once on it's axis! (24 hours long!)
Ancient Egyptian Calendar
5,000 B.C. - Solar based, 12 thirty- day months, plus five days for festivals!
Ancient Hebrew Calendar
3,000 B.C. - Solar/Lunar based, years have 12 or 13 months!
Ancient Mayan Calendar
Very complex! Based on cycles of sun, moon, and Venus!
Ancient Roman Calendar
Solar/Lunar based. 365 days a year, 7 days a week. No leap year so seasons shifted!
Year to which an extra day is added to keep calendars accurate!
Julius Caesar added 90 days to 46 B.C., and a leap year every 4 years!
Present day calendar. Pope Gregory in 1582 adjusted leap years!
Early Astronomers all backed up their theories with...
(A.D. 140) Believed Earth was at center of universe with planets, sun, and starts revolving around it! Called the Geocentric Theory.
(A.D. 1543) Believed Sun was at center of universe. Called the Heliocentric Theory!
(Late 1500's) Made precise measurements of positions of planets!
(A.D. 1609) Stated Three Laws of Planetary Motion!
(A.D. 1609) First used a telescope to study the sky, and observed surface of the Moon and four moons of Jupiter!
(A.D. 1687) Three Laws of Motion!
(A.D. 1781) Discovered planet Uranus!