Ch01 Lecture part3 video

Summary

This 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

00:00

🌕 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.

05:00

🌗 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.

10:03

🌒 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.

15:03

🌑 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.

20:06

🌘 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.

Keywords

💡Moon

The Moon is Earth's natural satellite, which plays a central role in the video's discussion of celestial mechanics. It is defined as a celestial body that orbits a planet, and in this video, it is used to explain the concept of lunar phases and its movement in the sky, including its rise in the east and set in the west.

💡Phases of the Moon

The phases of the Moon refer to the changing appearance of the illuminated portion of the Moon as viewed from Earth. The video explains the different phases, from new moon to full moon, and how they occur due to the relative positions of the Earth, Moon, and Sun. The script uses terms like 'waxing crescent' and 'waning gibbous' to describe these phases.

💡Orbit

Orbit is the path that an object in space takes around another object due to gravity. In the context of the video, the Moon's orbit around the Earth and the Earth's orbit around the Sun are key to understanding the changing positions and appearances of these celestial bodies. The script mentions how the Moon's orbit leads to different rise and set times.

💡Eclipse

An eclipse is an astronomical event that occurs when one celestial body moves into the shadow of another. The video discusses two types of eclipses: solar and lunar. A solar eclipse happens when the Moon passes between the Earth and the Sun, casting a shadow on Earth, while a lunar eclipse occurs when the Earth is between the Sun and the Moon, casting a shadow on the Moon. The script provides examples of how and when these events occur.

💡Solar Eclipse

A solar eclipse is a type of eclipse that happens when the Moon moves between the Sun and Earth, blocking the Sun's light either partially or completely. The video describes the experience of a solar eclipse, mentioning the 'diamond ring' effect and the visibility of the Sun's corona, as well as the conditions required for this event to occur.

💡Lunar Eclipse

A lunar eclipse occurs when the Earth is positioned between the Sun and the Moon, casting its shadow on the Moon. The video explains that during a lunar eclipse, the Moon can take on a reddish hue, often referred to as a 'blood moon,' due to the scattering of light by the Earth's atmosphere. The script provides the phenomenon's cause and effect.

💡Atmosphere

The atmosphere is a layer of gases surrounding a planet that is held in place by gravity. The video discusses the Earth's atmosphere and its role in the color changes observed during lunar eclipses and at sunrises and sunsets. It explains how the scattering of blue light and the bending of red light affect the appearance of celestial bodies.

💡Waxing and Waning

Waxing and waning describe the increase and decrease in the visible illuminated portion of the Moon, respectively. The video uses these terms to describe the progression of the lunar phases, from new moon to full moon and back to new moon. Waxing indicates the growth of the visible illuminated portion, while waning indicates its reduction.

💡Crescent

A crescent refers to the thin, curved shape of the illuminated portion of the Moon during its first and last quarter phases. The video mentions 'waxing crescent' to describe the phase where the illuminated portion is increasing, and 'waning crescent' for when it is decreasing.

💡Gibbous

Gibbous is used to describe a phase of the Moon where more than half of the Moon's surface is illuminated but not the entire disk. The video distinguishes between 'waxing gibbous,' where the illuminated portion is increasing towards a full moon, and 'waning gibbous,' where it is decreasing after a full moon.

💡Umbra and Penumbra

Umbra and penumbra are terms used to describe parts of a shadow. The video explains that during a solar eclipse, the umbra is the dark central shadow where the Sun is completely obscured, while the penumbra is the lighter outer shadow where only part of the Sun is obscured. These terms help illustrate the varying degrees of eclipse visibility.

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