week 2 earthly phenomena: seasons lunar phases solar and lunar eclipses tides reading: e2, e3, 5.2...
TRANSCRIPT
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 (365.2425 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 HemisphereWinter in Northern Hemisphere
Summer in Southern Hemisphere
Summer in Northern Hemisphere
Winter in Southern HemisphereFall 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.
Summer 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
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?
MonthsThe 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
First quarter
Full Moon
Waning gibbous
Third quarter
Waxing gibbous
New Moon
Waning crescent
Name of Phase Fraction Illuminated (Apparent) Side Illuminated Rises Sets
New Moon 0 None 6am 6pm
Waxing Crescent ¼ West (Right) 9am 9pm
First Quarter ½ West (Right) Noon Midnight
Waxing Gibbous ¾ West (Right) 3pm 3am
Full Moon 1 All 6pm 6am
Waning Gibbous ¾ East (Left) 9pm 9am
Third Quarter ½ East (Left) Midnight Noon
Waning Crescent ¼ East (Left) 3am 3pm