What do we mean when we say: The Earth is Tilted Earth’s Seasons Most globes show the axis tilted But what is the axis tilted with respect to? orbit plane perpendicular to orbit plane axis 23½°

The 23.5 degree tilt of the earth axis The number 23.5 shows up often in explaining the changes with the sun throughout the year. The Reasons for the Seasons AND The revolution of Earth around the sun

What is NOT a reason for the Seasons? The earth is closer to the sun? NOOOOOO! Actually, the earth is farthest from the sun in July (Aphelion) and closest to the sun in January (Perihelion)

Point directly overhead Where would Polaris be located? If this is in Red Hook, what is the altitude of Polaris? horizon 42º Altitude = degrees above a horizon

Season Simulation

Summer Solstice

Winter Solstice

Summer Solstice

Winter Solstice

Summer Solstice Concentrated rays

Winter Solstice Rays Spread Out

Equinox path Red Hook 42° N 71.5° 48 ° 24.5 °

Sun’s Path at Different Seasons in Red Hook 42° N

east southeast northeast The sun rises here on September 23 rd and March 21 st The sun rises here on December 21st Facing East in Red Hook The sun rises here on June 21 st

east southeast northeast The paths of the rising sun in Red Hook look like this at each season March, Sept.June Dec How many degrees apart is the sun’s rising position at each season? 23½ Where do you think the sun rose today? (MAY) About here

Sun’s changing vertical ray Sep. 21 Dec. 21 Jun 21 Mar. 21 Red dot shows where Sun is overhead

Changing Zodiac Constellations

Match the picture with the season

Date? September 23 Vertical Ray? Equator Sunrise? Due East Sunset? Duration of daylight? 12 hours Name of orbit position? Autumnal Equinox Due West Sun’s Path? Average Shadows at noon? Average

Date? Dec. 21 Vertical Ray? 23.5 South Sunrise? Southeast Sunset? Duration of daylight? 8 hours Name of orbit position? Autumninal Equinox Southwest Sun’s Path? Average Name of orbit position? Sun’s Path? Low Winter Solstice Shadows at noon? LONG

Date? Mar 21 Vertical Ray? Equator Sunrise? Due east Sunset? Duration of daylight? 12 hours Name of orbit position? Autumninal Equinox Due west Sun’s Path? Average Name of orbit position? Sun’s Path? Low – note long shadows Winter Solstice Name of orbital position? Vernal Equinox Sun’s Path? Average Shadows at noon? Average

Date? June 21 Vertical Ray? 23.5 North Sunrise? Northeast Sunset? Duration of daylight? 16 hours Name of orbit position? Autumninal Equinox Northwest Sun’s Path? Average Orbital position? Summer Solstice Sun’s path? High Shadows at noon? Short

At which season is the Earth very slightly closer to the sun Winter (January) perihelion Summer (June) aphelion On which date is the Daylight period longer For the northern hemisphere?

Label north on the diagram Draw in the path of The sun on Dec.1 st Label the North Star Polaris On which date at noon will the observer cast the shortest shadow?

Where is the sun’s Vertical ray striking On the autumnal Equinox? equator Where is the sun’s vertical ray striking on June 21 st ? 23½º N Where is the sun’s vertical ray striking on December 21st ? 23½º S

east south north Dec. 21st March 21st June 21st On which date are the sun’s rays striking most directly? On which date is the heating from the rays most efficient? On which date is the Surface temperature most likely highest? On which date are shadows at noon the longest?