Assign. #1 distributed Friday Sep. 15. Due in your lab section slot, by 5 PM Sep 23. Office hours...
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Transcript of Assign. #1 distributed Friday Sep. 15. Due in your lab section slot, by 5 PM Sep 23. Office hours...
Assign. #1 distributed Friday Sep. 15.Due in your lab section slot, by 5 PM Sep 23.
Office hours Mon, Thurs, and Friday this week. See Web page.
Lab 1 will be due between Sep. 25 - 28.
The motion of The motion of
the Moonthe MoonANNOUNCEMENTS
The Moon, Our Constant CompanionThe Moon, Our Constant Companion
Why do we see phases of the Moon?
What conditions are necessary for an eclipse?
Why were eclipses difficult for ancient peoples to
predict ?
Our goals for learning:
Note: the Chpt. 2 Moon tutorial on
masteringastronomy.com is useful!
AnimationsAnimations
Ecliptic Plane
Orbit of Moon
Why do we see the same face?Why do we see the same face?
Rotation period = orbital period
What do you see if you're standing on the
Moon looking at Earth?
AnimationsAnimations
Causes of lunar phases
Lunar MotionLunar Motion
Phases of the Moon’s 29.5 day cycle
(is that synodic or sidereal???)new
Crescent
first quarter
gibbous
full
gibbous
last quarter
crescent
Waxing
Waning
The lunar phasesThe lunar phasesNotice that the size seems
to change. Why?
Notice that it 'wobbles' a
bit. Why?
The lunar phasesThe lunar phasesNotice that the size seems
to change. Why?
Moon is not at a constant
distance.
Notice that it 'wobbles' a
bit. Why?
Because the orbital speed
is not exactly constant
Called 'librations'
Why do we see phases?Why do we see phases?
Half the Moon
illuminated by Sun
and half dark
We see some
combination of the
bright and dark
faces
Preliminaries: Local Solar timePreliminaries: Local Solar time
Interactive
applet at
mastering
astronomy
.com
Phases of the Moon. An example: Phases of the Moon. An example:
the waxing crescentthe waxing crescent
From the
publisher's
web site.
Rising/setting times of the MoonRising/setting times of the Moon
Depending on the phase
of the Moon it always
rises and sets at the
same (rough) local solar
time.
This is due to simple
geometry of the
illumination by the Sun.
See Fig 2.21 of Cosmic
Perspective.
NOTE: The times above neglect the Earth's tilt!
AnimationsAnimations
Phases of the Moon
Rise/set time vs phase
Handout given in class
Q: You see a quarter moon Q: You see a quarter moon
rising after drinking in the Pit. rising after drinking in the Pit.
What time is it?What time is it?
A) 9 PM
B) Midnight
C) 3 AM
D) 6 AMBonus : First or Third quarter?Bonus : First or Third quarter?
Eclipses : Puzzles for ancient Eclipses : Puzzles for ancient
astronomers/astrologersastronomers/astrologers
The Earth & Moon cast
shadows.
When either passes
through the other’s
shadow, we have an
eclipse.
Why don’t we have an
eclipse every full & new
Moon?Eclipses
twice a
month?
The Moon's orbit is inclined.The Moon's orbit is inclined.Moon not necessarily in the ecliptic when it
comes `into line' with the Sun
AnimationsAnimations
Moon's orbit tilt
Eclipse Seasons...
How rare are eclipses
Eclipse PredictionsEclipse PredictionsEclipses recur in the approx. 18 yr, 11 1/3 day
saros cycle
But even then, eclipse location and type (e.g.,
partial, total) may vary. Why?
Lunar Eclipses Lunar Eclipses (way out of scale)(way out of scale)
From the
publisher's
web site.
Lunar Eclipse SequenceLunar Eclipse Sequence
Is time
going
L to R
or
R to L
?????
Lunar eclipse geometryLunar eclipse geometry
Solar eclipse geometries
Total
Partial
Annular
Does time go from right to left or left to right here?
Time-lapse photo taken in northern Europe
Solar EclipsesSolar Eclipses
Animation