1. Climate and Latitude Sun’s rays spread over large area = cooler
concentrate in small area = warmer
Warmest where sun directly overhead (at noon)
cooler
warmer
cooler

2. Seasons What do we observe? Warm in Summer; Cold in Winter
Yearly cycle
Linked to Sun’s location on ecliptic (Spring = Vernal Equinox, Summer = Summer Solstice; etc)
Sun is heat source
Seasons in N and S hemispheres opposite
N summer = S winter
Seasons near Equator less severe

3. Cause of Seasons No! Changing distance to Sun?
Orbit is ellipse; distance changes
Good idea, BUT
Orbit almost circular
Trivial change in distance
little change in heating
Closest to sun in January
Predicts summer in January
Both N and S hemispheres at same distance
Predicts seasons same in N and S hemispheres

4. Cause of Seasons Yes Tilt of Earth’s Axis?
Location where sun overhead (at noon)
Vernal & Autumnal Equinoxes (Mar 21, Sept 21)
Overhead at Equator
Summer Solstice (Jun 21)
Overhead on Tropic of Cancer (23.5º N)
Warmer in N hemisphere; cooler in S hemisphere
Winter Solstice (Dec 21)
Overhead on Tropic of Capricorn (23.5º S)
Warmer in S hemisphere; cooler in N hemisphere
cooler
warmer
cooler
Zenith
Horizon

5. Cause of Seasons - Part 2 No!! Changing distance to Sun?
Earth’s axis tilted
N hemisphere closer in summer; farther in winter
Opposite for S hemisphere
BUT
Trivial change in distance
Predicts little change in heating

6. Cause of Seasons - Part 2 Yes Tilt of Earth’s Axis? Path of Sun in sky
Summer Solstice (Jun 21)
Sun farthest north
Transits high at noon
Days are long
Winter Solstice (Dec 21)
Sun farthest south
Transits low at noon
Days are short
Large amount of heating
Small amount of heating

7. For an observer in the continental U. S
For an observer in the continental U.S., which, if any, of the x’s (a – e) in the figure below correctly shows the position of the Sun’s shadow
at noon? Note that the position of the Sun’s
shadow at noon on the Winter and Summer Solstices are shown.
a) a
b) b
c) c
d) d
e) e

8. Motions and Phases of the Moon
Composite Image Credit: T.A. Rector, I.P. Dell'Antonio, NOAO, AURA, NSF

9. Motion of Moon Daily Motion Like Stars Moon Orbits Earth
Rise in East; Transit in South; Set in West
Moon Orbits Earth
Moon slips on Celestial Sphere
13 degrees per day = 1 lunar diameter per hour
Sidereal Period = Orbital Period
27.3 days
Time from full moon to full moon
29.5 days
(similar to sidereal day vs. solar day)
Moon rises roughly 50 min later each day

10. Rotation of Moon Always see same side Moon rotates once per month
Non-rotating moon
Rotating moon

11. D --> O --> C Moon Phases New = all black Full = all white
crescent
Moon Phases
Waxing
1st quarter
New = all black
Full = all white
Crescent < half white
Gibbous > half white
Quarter = half white
Waxing = growing
Waning = shrinking
gibbous
full
gibbous
3rd quarter
Waning
D --> O --> C
crescent

12. Phases of Moon

13. Phases of Moon Not caused by Earth’s shadow! Cause:
Changing view of illuminated side
(as Moon orbits Earth)
“Back Side” sometimes called “Dark Side”
Back side not dark
Back side has night and day
(just like front side)

14. Workbook Exercise: Cause of Moon Phases
(pages in workbook)

15. During the full moon phase, how much of the Moon’s surface is being illuminated by sunlight?
a) none
b) less than half
c) half
d) more than half
e) all

16. CHALLENGE QUESTION
You look up at a 1st Quarter moon and see that the crater where you built your retirement home is on the terminator (the dividing line between light and dark). What time of day is it there?
Sunrise
Noon
Sunset
Midnight

17. Workbook Exercise: Predicting Moon Phases
(pages in workbook)

18. Which phase of the Moon rises at noon?
a) Waning gibbous
b) Third quarter
c) First quarter
d) Waxing crescent
e) None of the above

19. Solar & Lunar Eclipses

20. Eclipses Solar Lunar Moon’s shadow falls on Earth
Moon moves into Earth’s shadow

21. Earth and Moon Shadows
Umbra
(and C) Penumbra
Umbral Extension

22. Earth and Moon Shadows A B C D Total Partial Annular Appearance of Sun
Observer location A B C D
Type of Eclipse
Total
Partial
Annular

23. Solar Eclipse

25. Lunar Eclipse

26. Eclipse Requirements Why not every new/full moon? Moon’s orbit tilted
Moon usually crosses above (or below) Sun
Eclipses require:
Moon crossing ecliptic
Sun at crossing point

28. Eclipse Seasons Twice each year Eclipses occur in sets
when sun near lunar crossing
Eclipses occur in sets
“two’s” or “three’s”
alternate lunar, solar (separated by 2 weeks)
Frequency of eclipses: solar same as lunar
Lunar visible from half of Earth
Solar only dramatic if total
Total Solar only visible from small region

29. When the Moon appears to completely cover the Sun (a solar eclipse), the Moon must be at which phase?
a) full
b) new
c) first quarter
d) last quarter

30. When the Moon moves through the Earth’s shadow, causing it to appear to darken (a lunar eclipse), the Moon must be at which phase?
a) full
b) new
c) first quarter
d) last quarter

31. Motion of the Planets Diurnal motion like fixed stars
Rise in “east”
Transit “high/low in south”
Set in “west”
Position on celestial sphere slowly “slips” from day to day (similar to sun and moon)

32. Planet Motion E W Generally move from W to E
Retrograde motion - time when planet appears to move backwards from E to W

33. Planets Planet = Greek for “wanderer”
5 visible planets (others too faint)
Mercury, Venus, Mars, Jupiter, Saturn
Total of 7 wandering objects (including Sun and Moon)

34. Planet Location Planets always found in Zodiac
18º wide belt centered on ecliptic
Mercury and Venus always close to sun
Mars, Jupiter, Saturn seen everywhere (in Zodiac)
Sometimes near sun (conjunction)
Sometimes opposite to sun (opposition)

35. Where (and at what time) would you look to see a planet rise when it is in retrograde motion?
a) Near the eastern horizon at sunrise
b) Near the western horizon at sunrise
c) Near the eastern horizon at sunset
d) Near the western horizon at sunset

36. Workbook Exercise: Understanding Retrograde Motion
(pages in workbook)

37. A planet moving in retrograde motion will, over the course of one night, appear to
a) move east to west
b) move west to east
c) not move at all, as planets do not move with the stars
d) move randomly, as planets move differently than the stars

38. A planet is moving in retrograde motion
A planet is moving in retrograde motion. Over the course of several nights, how will the planet appear to move relative to the background stars?
a) east to west
b) west to east
c) It will not move at all, as planets do not move with the stars
d) It will move randomly, as planets move differently than the stars

39. A planet is moving in normal motion
A planet is moving in normal motion. Over the course of several nights, how will the planet appear to move relative to the background stars?
a) east to west
b) west to east
c) It will not move at all, as planets do not move with the stars
d) It will move randomly, as planets move differently than the stars