Rotation = 1 day, 15° per hour West to East Everything appears to rise in East and set in West

Two types of Days: 1)Sidereal Day: rotation of Earth relative to the stars -23 hours, 56 minutes, 4 seconds -preferred by astronomers b/c stars rise and set at same time every day 2)Solar Day: rotation of Earth relative to the sun -24 hours -longer than sidereal day since Earth moves in a certain distance around the sun each day -Stars rise and set 4 minutes earlier each day since our time is set to solar time

Time: based on fact that noon is when the Sun is directly overhead Problem #1: Earth is round, noon occurs at different times at different longitudes…would have to keep changing watch every time you moved from east to west Solution: Time zones -24 times zones around the world each 15° wide (360° / 24 = 15°) -5 time zones in the United States

Problem #2: time advances as you travel east, if you keep going around the world time keeps advancing Solution: International Date Line -Runs through the middle of Pacific Ocean. -Crossing the line adds or subtracts a day depending on which direction you are traveling JET LAG (desynchronosis): body’s inability to adjust internal clock regulated by hypothalamus

Calendars: based on days in a year 1.Year is one revolution of earth around the sun Tropical year = 365 days, 5 hrs, 48 min, 46 sec If using 365 days/year only takes 4 years to be off 1 day 2. Julian Calendar: originated in 45 B.C. utilized leap year, extra day every 4 years Still off by 11 minutes, 14 seconds to tropical year After a few centuries already off by a couple of weeks 3. Gregorian Calendar: originated in 1582 when calendar was off by 10 days Utilizes leap year rule (no leap year in century years not evenly divisible by 400) Still off by 25 seconds from tropical year, but results only in 1 day less in 3,300 years US adopted in 1752

Seasons: caused by Earth’s axis being inclined 23 ½ ° to the ecliptic 1.Summer: northern hemisphere tilted toward sun, more hours of daylight, sun’s rays more direct leading to warm temps 2. Winter: northern hemisphere tilted away from sun, less hours of daylight, sun’s rays less direct so colder temps 3.Summer solstice: June 21 or 22 longest day of the year at our latitude (45°)…18 hrs 4.Winter solstice: Dec. 21 or 22 shortest day of year…9 hours of daylight 5. Equinox: “equal night” equal hours of day and night (12 hrs), sun rises at due east and sets at due west Spring (Vernal) March 20 or 21 Fall (Autumnal) Sept 22 or 23

Tropic of Capricorn: 23 ½ ° S latitude, sun directly overhead at that latitude on winter solstice Tropic of Cancer: 23 ½ ° N latitude, sun directly overhead at that latitude on summer solstice Arctic Circle: 66 1/2° N latitude, sun does not rise at winter solstice and does not set at summer solstice Antarctic Circle: 66 1/2° S latitude, sun does not rise at summer solstice and does not set at winter solstice

Sun and moon appear to be the same size, so moon at times seems to cover the sun Sun is actually 400 times larger, but also 400 times farther away Eclipse: any part of either the Earth or the Moon enters the shadow of the other

Solar Eclipse: moon covers the sun casting a shadow on the Earth only visible in certain areas on Earth b/c the umbra of the moon is small Lunar Eclipse: casts a shadow on the moon or appears to block the sunlight from the moon seen everywhere on Earth b/c the umbra of the Earth is large moon is in full phase and lasts a little under 2 hours

Must be in path of totality to see a solar eclipse

Two parts of the shadow: Umbra: dark cone where the shadow is the darkest Penumbra: lighter, more scattered region of darkness

Solar Eclipse 2006 Viewed from Aspendos Theatre in Turkey

Lunar Eclipse shot from Honolulu, Hawaii in August of 2007

Next Lunar Eclipse: December 21, 2010 Next Solar Eclipse: July 11, 2011…but you need to travel to the Southern Pacific Ocean to see it!