Ch01 Lecture part3 video
Summary
TLDRThis lecture delves into the celestial mechanics of the Moon, explaining its phases and movement across the sky due to Earth's rotation and the Moon's orbit. It explores the waxing and waning cycles, the Moon's different phases, and the rare occurrences of solar and lunar eclipses. The presentation also touches on the Earth's atmospheric effects during eclipses, causing the red hue of a lunar eclipse and the visibility of the Sun's corona during a solar eclipse. The lecture concludes with insights into predicting eclipse seasons based on the orbits of the Earth and Moon.
Takeaways
- 🌓 The Moon has different phases due to the relative positions of the Earth, Moon, and Sun, which affect how much of the Moon is illuminated and visible from Earth.
- 🌅 The Moon rises in the east and sets in the west, following the Earth's rotation and its own orbit around the Earth.
- 🌑 A new moon is when the Moon is not visible from Earth because the side facing us is not illuminated by the Sun.
- 🌒 Waxing phases include the crescent and gibbous phases, where the visible portion of the illuminated Moon increases from new to full moon.
- 🌕 A full moon occurs when the entire face of the Moon is lit up and visible, which happens when the Moon is on the opposite side of the Earth from the Sun.
- 🌗 Waning phases are when the illuminated portion of the Moon decreases from full to new moon, including the waning gibbous and crescent phases.
- 🕒 The Moon's orbit around the Earth takes about 27.3 days, but a full lunar cycle (from new moon to new moon) takes about 29.5 days due to the Earth's movement around the Sun.
- 🌞 Solar eclipses occur when the Moon's orbit aligns with the Earth's orbit around the Sun, casting a shadow on the Earth.
- 🌜 Lunar eclipses happen when the Earth's shadow falls on the Moon, which can give the Moon a reddish hue due to the scattering of light by the Earth's atmosphere.
- 🔭 The Earth's atmosphere bends red light towards the Moon during a lunar eclipse, causing it to appear red, which is a result of all the sunrises and sunsets on Earth being projected onto the Moon.
- ☀️ The visibility of the Moon and the occurrence of eclipses can be predicted based on the understanding of the Earth's and Moon's orbits, with eclipse seasons where solar and lunar eclipses are likely to happen.
Q & A
Why does the Moon appear to rise in the east and set in the west?
-The Moon appears to rise in the east and set in the west due to the Earth's rotation on its axis. This is similar to how the Sun and stars move across the sky from east to west.
What causes the different phases of the Moon?
-The different phases of the Moon are caused by the changing angles between the Earth, the Moon, and the Sun. As the Moon orbits the Earth, different portions of the Moon's surface are illuminated by the Sun, resulting in various visible phases.
What is the term used for the phase when the Moon is not visible from Earth?
-The phase when the Moon is not visible from Earth is called the 'new moon.'
How is the waxing crescent phase of the Moon different from the waning crescent phase?
-The waxing crescent phase occurs between the new moon and the first quarter, where the visible portion of the Moon is increasing. The waning crescent phase occurs between the third quarter and the new moon, where the visible portion is decreasing.
What is the term for the phase when half of the Moon is illuminated as seen from Earth?
-When half of the Moon is illuminated as seen from Earth, it is called the 'first quarter' or 'last quarter' phase.
Why does the Moon's rise time change each day?
-The Moon's rise time changes each day because the Moon orbits the Earth approximately 50 minutes later each day due to the Earth's rotation and the Moon's orbit around the Earth.
What is the difference between a sidereal month and a synodic month?
-A sidereal month is the time it takes for the Moon to orbit the Earth once, which is about 27.3 days. A synodic month is the time it takes for the Moon to go through one full cycle of phases, from new moon back to new moon, which is about 29.5 days.
What causes a solar eclipse?
-A solar eclipse occurs when the Moon is positioned directly between the Earth and the Sun, casting its shadow on the Earth and blocking the Sun's light.
What causes a lunar eclipse?
-A lunar eclipse occurs when the Earth is positioned directly between the Sun and the Moon, casting the Earth's shadow on the Moon.
Why does the Moon appear red during a lunar eclipse?
-During a lunar eclipse, the Moon appears red because the Earth's atmosphere scatters shorter wavelength light (blue light), while longer wavelength light (red light) bends around the Earth and reaches the Moon, giving it a reddish hue.
How can the occurrence of solar and lunar eclipses be predicted?
-The occurrence of solar and lunar eclipses can be predicted by understanding the orbits of the Earth around the Sun and the Moon around the Earth. The alignment of these orbits at certain periods allows for the prediction of eclipse seasons.
Outlines
🌕 Introduction to Moon Phases and Movements
The paragraph introduces the concept of the moon's movements in the sky, explaining how the moon rises in the east and sets in the west due to Earth's rotation. It discusses the moon's phases, starting from a new moon where the moon is not visible, progressing through the waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, third quarter, and back to new moon. These phases result from the moon's position relative to Earth and the Sun, with specific terms like 'waxing' indicating increasing visibility and 'waning' indicating decreasing visibility.
🌗 Moon Phases and Timing
This paragraph details how the moon's phases relate to its position in its orbit around Earth. It explains how the moon appears at different times of the day depending on its phase, such as the third quarter being visible in the morning and the first quarter in the afternoon or evening. The paragraph also mentions that the moon rises about 50 minutes later each day due to its orbit around Earth. Additionally, it touches on the phenomenon of eclipses, where the Earth's or Moon's shadow may block out the other, depending on the alignment.
🌒 Eclipses: Solar and Lunar Explained
The paragraph provides an explanation of solar and lunar eclipses. A solar eclipse occurs when the moon blocks the Sun's light from reaching Earth, and a lunar eclipse occurs when Earth's shadow falls on the moon. The paragraph explains that these events are rare due to the tilt in the orbits of the moon around Earth and Earth around the Sun. The moon's shadow during a solar eclipse only covers a small area on Earth, while Earth's shadow during a lunar eclipse can cover the entire moon. The paragraph also introduces the terms 'umbra' and 'penumbra' to describe the types of shadows cast during these eclipses.
🌑 The Solar and Lunar Eclipse Phenomena
This paragraph delves deeper into the specifics of solar and lunar eclipses, describing how a solar eclipse progresses from partial to total coverage of the Sun by the moon, revealing the Sun's corona. It also explains the lunar eclipse phenomenon, where the moon appears red due to Earth's atmosphere bending red light while scattering blue light, a phenomenon linked to the scattering of light during sunrise and sunset. The paragraph emphasizes that these eclipses occur rarely due to the specific alignments required, with solar and lunar eclipses often occurring in close succession.
🌘 Predicting Eclipse Seasons
The final paragraph discusses the predictability of eclipses, referring to 'eclipse seasons' where solar and lunar eclipses happen within a short period. The predictability is based on the understanding of Earth's and the moon's orbits. The paragraph provides examples of past and future eclipses, mentioning the notable solar eclipse of 2017 and upcoming eclipses in 2024 and beyond. The conclusion encourages anticipation of future lectures related to celestial movements.
Mindmap
Keywords
💡Moon
💡Phases of the Moon
💡Orbit
💡Eclipse
💡Solar Eclipse
💡Lunar Eclipse
💡Atmosphere
💡Waxing and Waning
💡Crescent
💡Gibbous
💡Umbra and Penumbra
Highlights
The Moon rises in the east and sets in the west due to Earth's rotation on its axis.
The Moon's phases change as it orbits the Earth, with the full moon being completely lit up and the new moon not visible.
The waxing and waning phases of the Moon are explained by the varying amounts of the Moon's surface illuminated by the Sun.
The Moon's orbit around the Earth and Earth's orbit around the Sun result in different rise and set times for the Moon.
The Moon's orbit is slightly tilted relative to Earth's orbit around the Sun, causing infrequent eclipses.
A lunar eclipse occurs when the Earth's shadow falls on the Moon, and a solar eclipse when the Moon blocks the Sun.
The duration of a lunar month is approximately 29.5 days, which is longer than the Moon's sidereal month due to Earth's movement around the Sun.
The phenomenon of the Moon's phases can be observed by the time of day the Moon is visible and its position in the sky.
The Earth's atmosphere scatters blue light, causing the sky to appear blue during the day and the Sun to appear red during sunrise and sunset.
During a lunar eclipse, the Moon takes on a reddish hue due to the Earth's atmosphere bending red light towards the Moon.
Eclipse seasons, where solar and lunar eclipses occur close together in time, can be predicted based on the orbits of the Earth and Moon.
A solar eclipse is visible only in a narrow path on Earth, with the rest of the planet experiencing a partial eclipse or no eclipse at all.
The 'diamond ring' effect is observed during a solar eclipse when the last rays of the Sun peek through valleys on the Moon's surface.
The Sun's corona is visible during a total solar eclipse, revealing the Sun's atmosphere.
The occurrence of eclipses is rare due to the specific alignment needed between the Earth, Moon, and Sun.
Historical and future dates of solar and lunar eclipses are charted, showing the predictability of these celestial events.
The upcoming solar eclipse on April 8th, 2024, will be visible from Mexico through Texas and the eastern United States.
The lecture series will continue to explore the movement of celestial bodies and our understanding of their motion.
Transcripts
hello everyone welcome to part three of
our first lecture today now we're to
talk about the moon the last part of
what we see the sky
changing over time now our Moon the moon
it does rise in the set or rise in the
east and sets in the west
now just like everything else this has
to do with the fact that the Earth spins
on its axis but just like the planets
the Sun and the stars okay you're gonna
see the moon move from the east to the
west in the night or the daytime sky
nighttime sky depending on what time of
day it or what time of the month it is
but how does this actually work the moon
when you look at it you will notice that
it has different phases so sometimes it
looks like this where you can see the
whole moon lit up other times not so
much why well these phases how much of
the moon you see lit up
well it goes from we call new which
means that you can't see the moon at all
back to new or you can't see them there
at all but in between you can see
different amounts of the moon lit up
different amounts the moon lit up to
where you have a full moon where you can
see the entire moon that faces us you
can see the whole thing lit up now we
call this new when you can't see it at
all
up through the first quarter we can you
see a quarter of the moon lit up
that is called the waxing crescent phase
of the moon from first quarter to full
we call that waxing gibbous but once
it's full we start seeing less and let
it less less less and less of it lit up
we call that waxing gibbous or waning
gibbous so waning means less and less
waxing means more and more and then you
go from third quarter back to new again
waning we call that waning crescent so
why do we have these phases well it has
to do with where we are relative to the
Sun and where the moon is relative to us
so if you are here on the planet and you
are the sun's over here to the left you
are this is clearly noon
right because you are looking at the Sun
well if the moon happens to be here the
side of the Moon that you can see this
side of the moon
well that side of the Moon is in
darkness it's not lit up the side of the
moon it's lit up by the Sun is facing
away from us and that would be a new
moon now about a week later you're gonna
be here or the moon is gonna be here as
it goes around the earth because of
orbits around the earth in this
direction so one week later the moon
would be here if you're standing on the
earth and you happen to be right here on
the earth first of all because the Earth
spins this direction if you're here on
the earth that is gonna be sunset but if
you're looking up and you see the moon
if the moon happens to be here
well the left-hand side of the moon is
lit up by a Sun you're gonna see the
left-hand side lit by the Sun it's gonna
be first quarter the right-hand side of
the Moon is facing space so it's dark on
the other hand if you wait a while the
moon eventually goes around the earth
it's gonna be here at full if you're
here on the earth it's midnight but if
you're looking at the Sun at the moon
the moon the side of the Moon you can
see is fully lit up that's a full moon
if the moon a week after that the moon's
gonna be here if you're here on the
earth first of all because there's the
spinning that is a round sunrise
looking at the moon and the moon happens
to be up here it's gonna be third
quarter and if you look at the moon its
third quarter you will notice the
left-hand side is lit up if you're here
on the earth and the moon happen is the
first quarter okay you're looking down
at the moon it's the right hand side is
lit up so you can tell what phase the
moon is in just like looking at it and
by knowing what time of day it is when
you can see it okay if you see the moon
at night if you're here at night you're
looking at the moon if it's mostly full
or close to full or just after full
you're only gonna see it at night okay
the third quarter moon you're gonna see
in the morning first quarter moon you're
gonna see in the afternoon or evening
all right
now the moon because the earth orbits
around the Sun and the moon orbits
around the earth you're gonna have
different rise time and set times
depending on where the moon is as it
orbits around the earth it's about 50
minutes later each day so if you see the
moon rise today tomorrow the moon is
gonna rise 50 minutes and later alright
that just has to do with the fact that
the Earth or the moon orbits around the
earth and the Earth orbits around the
Sun now there will be times when the
moon's orbit around the Earth and the
Earth's orbit around the Sun coincide
which to say that the moon will
occasionally block out the Sun and the
earth will occasionally block out the
moon by which I mean the Earth's shadow
will cast onto the moon such that the
moon is not lit up by the the Sun now
this only happens very very infrequently
the Earth's orbit around the Sun and the
moon's orbit around the Earth are
slightly tilted relative to each other
so you don't have overlap all of the
time now one thing to note the Earth's
orbit around the Sun that takes a year
the moon's orbit around the Earth takes
twenty three or twenty seven point three
days that is not how long it takes for
the moon to go through one full cycle so
for a full cycle what I mean is from
like a new moon through
a first quarter through full moon
through third quarter and back to new
so from new all the way back to new
actually takes twenty nine point five
days twenty nine and a half days
why is it different well the moon goes
once around the earth every 27 days
twenty seven point three days but if the
Earth or the moon goes once around the
earth keep in mind in one month the
earth has moved around the Sun because
the Earth orbits around the Sun so when
the moon goes fully around the earth
once well it will be here but that this
position that is not full because the
moon is not directly between the Earth
and the Sun for the moon to get full it
has to go a couple of days further to
get here which is why it takes a little
bit longer for a full cycle of the moon
so from new back to new or full back to
full as opposed to how long it takes the
moon to go once around the earth this is
called acid aerial month you should note
the same thing happens with the earth
and days so you guys think about the
earth have spinning around once on its
axis as being 24 hours it's actually not
it's actually 23 hours and 56 minutes it
takes the earth to spend once on this
axis but a day is 24 hours it's the same
kind of thing
it's d real day as opposed to actual day
is different than a well it's the same
thing as a stereo month as opposed
- an actual month all right now every
once in a while as I said the moon the
earth and the Sun will line up such that
the moon casts a shadow on the earth or
if the moon is over here the earth can
cast a shadow on the moon now if the
moon blocks out the Sun we call that a
solar eclipse if the Earth's shadow hits
the moon we call that a lunar eclipse
but it only happens every once in a
while because remember the moon's tilt
as it orbits the earth is different than
the earth's tilt as it orbits the Sun
which means only every once in a while
does the moon actually cast a shadow on
the earth or vice versa
now if the moon casts a shadow on the
earth it looks like this this is the
moon shadow on the earth it only hits a
small spot on the earth if the Earth's
shadow hits the moon the whole moon can
be covered but that's just because
remember the moon is smaller than the
earth it casts a smaller shadow so the
moon shadow only covers a little part of
the earth and what's going on is that
the moon is exactly aligned such that
shadow hits the earth now usually the
moon will be like up here and the shadow
doesn't hit the earth or I'll be down
here the shadow doesn't hit the earth
only every once in a while does the
moon's orbit around the earth coincide
with the Earth's orbit around the Sun
such that the moon's shadow is actually
hitting the earth but when that happens
and you get the
shadow on the earth and you see a solar
eclipse the Sun is blotted out by the
sky because the moon is in front of it
now you can only see it if you happen to
be right here in the middle okay if
you're out here on the earth you're not
going to see any kind of shadow at all
you're not gonna see in eclipse at all
if you're here which is in what's known
as the penumbra the penumbra of the
shadow is where you can see part of this
the Sun blotted out by the moon but only
part so only part of the Sun is blotted
out if you're in the middle it's called
the Umbra of the shadow and you're in
complete shadow the whole Sun is if you
were to watch this you would see the
moon the Sun start to move in front of
the moon or the moon start to move in
front of the Sun sorry and eventually
you would get most the Sun blotted out
almost all the Sun bought it out and
then the entire Sun blotted out and what
you see when the entire Sun has blotted
out is this which is the atmosphere we
will talk about this later on in this
class about the atmosphere of the Sun
that is known as the Sun's corona and
then when the Sun starts to or the moon
starts to leave start starts to stop
blocking out the Sun the very first
thing that happens is you will see a
little bit of the Sun lit up that's
often known as the diamond ring if you
ever get a chance to see a solar eclipse
I highly recommend it it is actually
pretty amazing in the sky
it's the only time only time you could
ever see the sun's atmosphere now
you will also get times when the moon is
in the Earth's shadow okay we call that
a lunar eclipse when the moon goes into
the earth shadows something weird
happens though it doesn't go dark it
actually becomes bright red it's like
weird dull red color that is often
called a blood mmm because it is so red
now why is red why is it not just like
disappear because it's in the earth
shadow well that actually has to do with
the atmosphere of the earth so what's
going on here is that light from the Sun
hits the Earth's atmosphere here and red
light gets bent by the atmosphere so red
light coming through the Earth's
atmosphere it's bent towards the moon
whereas blue light blue light gets
scattered blue light is scattered by our
atmosphere which is why during the day
the sky looks blue blue lights getting
bounced around in our atmosphere at
random directions and so if you're on
the earth looking at the Sun if you're
like here on the earth looking at the
Sun okay all around you you're gonna see
atmosphere and that atmosphere is gonna
look blue because blue light is
scattered red light is not scattered red
light goes through the atmosphere but it
is bent so this is why at like in the
evening or in the morning like say
you're here this is the morning you're
looking towards the Sun the Sun is
rising but the Sun has to go through the
sun's light has to go through a lot of
atmosphere here before you can see it
and because of that the blue light is
getting scattered out by the atmosphere
and the Sun is going to
renner because blue lights bein
scattered out now when you're here on
the earth and it's noon
you're not looking through nearly as
much atmosphere and the Sun schooling a
Sun you're here in the evening again
you're looking through a lot of
atmosphere at the Sun and blue lights
being scattered out so the Sun looks
redder that's why we have red Sun rises
and Sun Sun Sun sets it has to do with a
scattering of blue blue light but red
light it gets through it's not scattered
it's through the atmosphere which is why
the Sun looks kind of reddish during
this sunrise and sunset but it's that
same red light that goes through our
atmosphere and gets bent it's tilted a
little bit and it gets projected onto
the moon during a solar eclipse or doing
it during a lunar eclipse oh sorry so
during a lunar eclipse the red light
going through the Earth's atmosphere
it's tilted and projected onto the moon
so when you see a lunar eclipse and
looks red what you're literally seen
literally is all the sunrises and
sunsets on the earth projected onto the
moon so these kinds of eclipses happen
rarely because usually the moon will be
like here and the moon shadow doesn't
hit the earth where the the moon will be
here like a full moon but the Earth's
shadow does not hit it only every once
in a while will the the moon shadow
align right such that it hits the earth
or the Earth's shadow will align just
right and will hit the moon usually you
will find these happen coincidentally
which is to say that you have Eclipse
seasons so if if you have a solar
eclipse you're probably gonna have a
lunar
it's a couple of months later a so for
example you know solar eclipse September
13th
lunar eclipse September 28th okay two
weeks later so you have what I call the
clip seasons and you can predict these
things you can predict win exactly these
eclipses are going to happen once you
understand the Earth's orbit around the
Sun and the moon's orbit around the
Earth if you understand how those things
work you can predict when this is gonna
happen okay
so again usually the moon shadow doesn't
hit the earth and the Earth's shadow
does not hit the moon every once in a
while though when things line up just
right okay the moon will be here and it
casts a shadow on the earth or the moon
be here and the earth will cast a shadow
on it only every once in a while but
again you can predict these things
because we understand the Earth's orbit
around the Sun and we understand the
moon's orbit around the Earth we can
predict these things what happen okay so
here is a chart of when these things
will happen in the past in the future in
2004 or 2017 sorry there was a lunar or
a solar eclipse so the moon shadow
passed across the United States that was
pretty remarkable if you guys are you
saw that it was great if not well
there's never a chance in 2024 April 8th
we're gonna have a solar eclipse that
goes up through Mexico through Texas and
through the eastern seaboard of the
United States but you know there other
time
December 14th 2020 there will be a solar
eclipse that happens through South
America 2030 through South Africa ok so
all these times and dates are when
you're gonna see be able to see this
kind of event now that is it for our
first lecture in this series of lectures
that have to do with this class and stay
tuned for continuing lectures that he'll
have to do about stuff moving this guy
and how we understand how that stuff
moves to the sky
5.0 / 5 (0 votes)