Week 2 Earthly Phenomena: Seasons Lunar Phases Solar and Lunar Eclipses Tides Reading: E2, E3, 5.2 (12 pages)

Quick Quiz 1)If new Moon fell on March 2nd, what is the Moon's phase on March 14th? A) waxing crescent B) first quarter C) waxing gibbous D) full E) waning crescent 2)Only people in the Moon's umbral shadow can see a total solar eclipse. T/F 3)What will occur when the full Moon is on the ecliptic? ) A) a total lunar eclipse B) a total solar eclipse C) a partial solar eclipse D) an annular lunar eclipse E) a partial lunar eclipse if the Moon is at perigee

Rotation of the Earth Revolution (orbit) of the Earth Revolution (orbit) of the Moon Rotation of the Moon

Rotation of the Earth Earth’s rotation around its axis: Causes night and day (Solar day = average time between consecutive “noontimes”). Causes (apparent) motion of the stars

Rotation of the Earth Earth’s rotation around its axis: Causes night and day (Solar day = average time between consecutive “noontimes”). Causes (apparent) motion of the stars

Revolution (Orbit) of the Earth The revolution of the Earth around the Sun defines the year ( days). Earth’s motion around the Sun traces a path on the Celestial Sphere called the ecliptic. The Earth’s revolution around the Sun also causes the seasons. How?

TPS: What causes the seasons? A. The changing distance between the Earth and the Sun? B. The 23.5 degree tilt of the Earth’s axis? Hint: Although it is Winter in the Northern Hemisphere right now, it is Summer in the Southern Hemisphere.

Spring in Northern Hemisphere Fall in Southern Hemisphere Winter in Northern Hemisphere Summer in Southern Hemisphere Summer in Northern Hemisphere Winter in Southern Hemisphere Fall in Northern Hemisphere Spring in Southern Hemisphere NP SP

Why exactly? The Sun is lower in the sky in the Winter. The light from the Sun is diluted. Short Winter days mean less overall light shining on that part of the Earth. SummerWinter

Earth as Seen from the Sun North American Summer North American Winter

Equinoxes – Sun crosses the celestial equator (twice – Spring and Fall) Solstices – Sun’s farthest northerly or southerly position (Summer or Winter) Ecliptic – Path that the Sun follows in the sky

Seasons Ecliptic is plane of Earth’s path around Sun; at 23.5° to celestial equator Northernmost point (above celestial equator) is summer solstice; southernmost is winter solstice; points where path cross celestial equator are vernal and autumnal equinoxes

Seasons Combination of day length and sunlight angle gives seasons Time from one vernal equinox to next is tropical year

“Path of the Sun”

Revolution of the Moon The Moon’s revolution around the Earth causes: Lunar phases Eclipses Tides

Lunar Phases What causes the phases of the Moon? Is this crescent Moon caused by A. Sunlight shining mostly on the “far side” of the Moon? B. The shadow of the Earth?

Months The Moon takes about 29.5 days to go through whole cycle of phases – synodic month Phases are due to different amounts of sunlit portion being visible from Earth Time to make full 360° around Earth, sidereal month, is about 2 days shorter

Waxing crescent First quarter Full Moon Waning gibbous Third quarter Waxing gibbous New Moon Waning crescent

Waxing crescent New Moon Waning crescent First quarter

Waxing crescent First quarter Full Moon Waning gibbous Third quarter Waxing gibbous New Moon Waning crescent

Name of PhaseFraction Illuminated(Apparent) Side IlluminatedRisesSets New Moon 0None6am6pm Waxing Crescent¼West (Right)9am9pm First Quarter½West (Right)NoonMidnight Waxing Gibbous¾West (Right)3pm3am Full Moon1All6pm6am Waning Gibbous¾East (Left)9pm9am Third Quarter½East (Left)MidnightNoon Waning Crescent¼East (Left)3am3pm

Lunar Phases Movie

Does the Moon rotate? Yes! The Moon rotates once per every revolution of the Earth. As a result, we always see the same side of the Moon! We never see the “far” side of the Moon.