Reason for the Seasons Notes Seasons Vocabulary Seasons - Due to the tilt of earth as it travels around the Sun, we have spring, summer, fall, and winter. Source: http://www.srh.noaa.gov/abq/features/whatcausestheseasons/summersolstice2008.php Earth s Revolution - The circling of the Earth around the Sun. (The Moon also revolves around the Earth.) It takes 365 days (one year) for the Earth to revolve once around the Sun. Axis Source: http://www.learner.org/jnorth/tm/reasonsback.html Axis of Rotation - An imaginary line going from the North Pole to the South Pole. The earth spins on this line.
Earth s Rotation The Earth spinning on its axis. It takes the Earth 24 hours (one day) to revolve one time around its axis. Source: http://www.physicalgeography.net/fundamentals/6h.html Earth s Tilt - The earth s axis is not straight up and down, instead it leans at a 23.5-degree angle. Orbit - The path that a planet travels as it goes around the Sun or a moon takes as it goes around a planet. Source: http://www.aerospaceweb.org/question/astronomy/q0262.shtml Direct Sunlight (heat energy) - Covers a small surface area; heat is concentrated and warmer; Sun is high in the sky; summer heat energy is direct.
Indirect Sunlight (heat energy) - Covers a large surface area; heat is spread out and colder; Sun is low in the sky; winter heat energy is indirect. http://ag.arizona.edu/watershedsteward/resources/module/climate/climate-intro_pg2.htm Why do we have seasons? Because the Earth tilts. Earth tilts 23.5 o. How does tilt cause seasons? Earth Revolves Around Sun. Earth tilts towards or away from Sun. Earth tilts towards Sun in summer. Earth tilts away from Sun in winter.
Earth doesn t tilt towards or away from the Sun in spring and fall/autumn. Very important facts about the seasons. Earth is closest to the Sun in January (winter). Earth is farthest from the Sun in July (summer). The Earth s distance to the Sun has NO EFFECT ON WHY WE HAVE SEASONS Direct and Indirect Sunlight (Heat Energy) Direct sunlight (heat energy) is received in the summer. Indirect sunlight (heat energy) is received in the winter.
Direct Sunlight We receive direct sunlight (heat energy) when Earth tilts towards the Sun. Sunlight (heat energy) is concentrated (it covers a small area of the Earth s surface). Heat energy warmer. Sun is high in the sky. Indirect Sunlight We receive indirect sunlight (heat energy) when Earth tilts away from the Sun. Sunlight (heat energy) is not concentrated (it covers a large area of the Earth s surface). Heat energy colder. Sun is low in the sky.
Key Season Dates Event Date Seasons Winter Solstice December 21 st First Day of Winter Spring Equinox March 21 st First Day of Spring Summer Solstice June 21 st First Day of Summer Autumnal Equinox September 21 st First Day of Autumn/Fall Key Terms Solstice Dates the Sun is the highest or the lowest in the sky. Equinox Equal Nights Daylight and nighttime hours are equal about twelve hours of daylight and about twelve hours of nighttime. Winter Solstice Sun is at the lowest point in the sky. Has the fewest hours of daylight ( shortest day ) about eight hours of daylight. Summer Solstice - Sun is at the highest point in the sky. Has the most hours of daylight ( longest day ) about sixteen hours of daylight. Seasons Are Reversed When Northern Hemisphere is tilting towards the Sun (summer), the Southern Hemisphere is tilting away from the Sun (winter). When Northern Hemisphere is tilting away from the Sun (winter), the Southern Hemisphere is tilting towards the Sun (summer). Earth s Position Around Sun How Northern and Southern Hemisphere Tilt North Tilts way from Sun. South Tilts towards from Sun. Season in Northern and Southern Hemisphere North Winter South Summer Neither Hemisphere tilts towards/away from Sun. North Spring South Autumn/Fall
Seasons Are Reversed When Northern Hemisphere is tilting towards the Sun (summer), the Southern Hemisphere is tilting away from the Sun (winter). When Northern Hemisphere is tilting away from the Sun (winter), the Southern Hemisphere is tilting towards the Sun (summer). Earth s Position Around Sun How Northern and Southern Hemisphere Tilt North Tilts toward Sun. South Tilts away from Sun. Season in Northern and Southern Hemisphere North Summer South Winter Neither Hemisphere tilts towards/away from Sun. North Autumn/Fall South Spring