Test 1 is coming up. Wed Feb 22 (no classes on Feb 13, 15, 20) Start preparing! Go over the slides, LTs, and the multiple choice questions at the end of relevant chapters. 50 questions, multiple choice, scantrons. Bring a pencil! 1
Ch. 2 Discovering the Universe for Yourself Moon Phases & Eclipse 2
Quiz What time is it when the waxing crescent moon is highest in the sky? A) 6am B) 9am C) 12noon D) 3pm E) 6pm 3
Quiz waxing crescent moon When does it first rise? A) Midnight B) 6am C) 9am D) 12noon E) 3pm 4
Quiz waxing crescent moon When does it set? A) 3pm B) 6pm C) 9pm D) Midnight E) 3am 5
Lecture-Tutorial (LT): Predicting the Moon Phase (pp. 83-85) Work with a partner! Read the instructions and questions carefully. Discuss the concepts and your answers with one another. Come to a consensus answer you both agree on. If you get stuck or are not sure of your answer, ask another group. If you get really stuck or don t understand what the LT is asking, ask for a help. 6
Quiz What moon phase would be rising in the East at 3pm? A) Full moon B) waxing gibbous C) first quarter moon D) waxing crescent E) New moon 7
Quiz What Moon phase would be setting in the West at 3pm? A) Full moon B) waning gibbous C) first quarter moon D) waning crescent E) New moon 8
Quiz The Moon Phase is highest in the sky at 9pm today. What phase will the Moon be in three weeks after today? A) Full moon B) waxing gibbous C) first quarter moon D) waxing crescent E) New moon 9
Quiz It s 9 am. You look up in the sky and see a moon with half its face bright and half dark. What phase is it? A. First quarter B. Waxing gibbous C. Third quarter D. Half moon 10
We see only one side of Moon Synchronous rotation: the Moon rotates exactly once with each orbit That is why only one side is visible from Earth 11
Eclipses 12
In each phase of the Moon, how much of the Moon is lit up by the Sun? Half the Moon is always lit by the Sun Except... 13
When the Earth s shadow hits the Moon we have a. Moon Lunar Eclipse Earth 14
What causes eclipses? The Earth and Moon cast shadows. When either passes through the other s shadow, we have an eclipse. 15
Lunar Eclipse Clip 16
Moon Orbit Clip 17
Eclipses occur ONLY when the Moon crosses the plane of Earth s orbit around the Sun AND ONLY during the NEW or FULL phases 18
When can eclipses occur? Lunar eclipses can occur only at full moon. Lunar eclipses can be penumbral, partial, or total. 19
Quiz If there is going to be a total lunar eclipse tonight, then you know that (A) the Moon s phase is full (B) the Moon s phase is new. (C) the Moon s phase is 1st quarter. (D) the Moon s phase is 3rd quarter. (E) the Moon is unusually close to Earth. 20
Solar Eclipse 21
When the Moon s shadow hits the Earth, we have a. Solar Eclipse Earth Moon 22
Solar Eclipse Annular Eclipse Partial Eclipse Total Eclipse 23
24 24
25 25
26 26
When can eclipses occur? Solar eclipses can occur only at new moon. Solar eclipses can be partial, total, or annular. 27
Why don t we have an eclipse at every new and full moon? The Moon s orbit is tilted 5 to ecliptic plane So we have about two eclipse seasons each year, with a lunar eclipse at full moon and solar eclipse at new moon. 28
Summary: Two conditions must be met to have an eclipse: 1. It must be full moon (for a lunar eclipse) or new moon (for a solar eclipse). AND 2. The Moon must be at or near one of the two points in its orbit where it crosses the ecliptic plane (its nodes). 29
Predicting Eclipses Eclipses recur with the 18 yr, 11 1/3 day saros cycle, but type (e.g., partial, total) and location may vary. 30
Quiz The fact that we always see the same face of the Moon tells us that (A) the Moon does not rotate. (B) the Moon s rotation period is the same as its orbital period. (C) the Moon looks the same on both sides. 31
What have we learned? Why do we see phases of the Moon? Half the Moon is lit by the Sun; half is in shadow, and its appearance to us is determined by the relative positions of Sun, Moon, and Earth What causes eclipses? Lunar eclipse: Earth s shadow on the Moon Solar eclipse: Moon s shadow on Earth Tilt of Moon s orbit means eclipses occur during two periods each year 32