Earth in Different Dimensions Observing the World Round? observation the key first step to ALL science driven by curiosity a process of discovery answer questions about how the world works knowledge improves quality of life Or flat? Calculate circumference ( C) using simple math: Eratosthenes (Egypt, 235 B.C.) 360 o/7.2 o = C/500 miles; C = 50 x 500 miles = 25,000 miles On June 21 (summer solstice), midday sun a shadow cast by a directly overhead, shining down a deep well in monument in Alexandria the city of Syene (Aswan) the Sun's rays Angle of shadow made by sun shining on a ~5000 stadia = 500 mi ° ° monument at midday on June 21 in Alexandria 7 12' = 7.2 a well in Syene was 7o21’ Alexandria lies ~5000 stadia to the north of Aswan (~ 500 miles ) Remarkable agreement with actual figure of 24,862 miles (40,010 km) – WOW. 1 Where in the World are we? How do we describe where we are on the planet? Latitude (North-South) & Longitude (East-West) based on angular relationships to Earth’s center grid system used to precisely describe locations on the Earth’s surface expressed in degrees (o) of arc each degree is divided into 60 minutes (‘) each minute is divided into 60 seconds (“) 90 °N (North Pole) Latitude Longitude 180 °W 60 °N (180 °E) “parallels” = grid lines “meridians” = grid lines 30 °N that are parallel to the that intersect at poles 150 °W equator 0o = “Prime Meridian” ° 0o at equator, 90 o at 0 (Equator) (Greenwich, England) 120 °W 90 °W 60 °W 30 °W poles Parallels (Latitude) 180 o = halfway around Meridians (Longitude) 0o-90 oN = N. Hemisphere 30 °S Earth 0° o o o o 0 -90 S = S. Hemisphere 60 °S 0 -180 to west of Everywhere on Earth’s surface: Greenwich = W. Hemisphere 90 °S 1o lat. = 60 nautical miles (South Pole) 0o-180 o to east of 1’ lat. = 1 nautical mile Greenwich = E. Hemisphere 2 Equatorial View Polar View Special Latitudes and Latitudinal Zones North Pole 90 °N North Pole 90 °E (90 °N) 120 °E 60 °E 60 °N Arctic Circle northern high latitudes (66.5 ° N) 60 °N 30 °N 150 °E 30 °E mid-latitudes Prime ° ° ° ° ° ° Meridian 30 N 150 W 120 W 90 W 60 W 30 W Tropic of Cancer (23.5 ° N) subtropics 180 °W North Pole ° ° 0 ° 0 Equator (180 E) 90 °N 180 °W 0° Prime tropics (180 °E) Meridian 0° (Equator) 30 °S 150 °W 60 °N 30 °W Tropic of Capricorn (23.5 ° S) subtropics ° 30 °N 30 °S 60 S 120 °W 60 °W Equator ° 0 90 °W mid-latitudes 90 °S Antarctic Circle ° South Pole (66.5 ° S) 60 S Smith College southern high latitudes (90 °S) Lat. 42°19 ’ N, Lon. 72°38 ’ W South Pole The Earth’s tilt – the reason for the seasons Earth's axis of rotation (23.5 ° tilt) Arctic Circle North Pole Tro pic of Ca nce S e r Plane of Earth's orbit around Sun (aka, “the ecliptic”) qua tor Tro pic of U Ca pric orn Antarctic Circle N South Pole 3.