Transcript Lunar Eclipse

Motions of the Sky
1. Seasons
2. Tides
3. Moon Orbit/Tidal Locking
5. Moon Phases
6. Lunar Eclipses
7. Solar Eclipses
8. Planet Retrograde Motion
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Rotation –Spinning of the earth on its axis
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Revolution- movement of earth around the sun
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24 hours
1 day
365 days
1 year
Precession – wobble of earth on axis
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26,000 years
Seasons
•Seasons ARE NOT caused by the changing distance
between the Sun and Earth.
• During the Northern hemisphere winter, we are
actually CLOSER to the Sun.
Seasons ARE caused by:
•The TILT of the Earth's axis.
•The Earth is tilted 23.5 degrees
Seasons
When it is summer in one hemisphere, it is
winter in the other.
Apparent motion of the Sun
• we do not perceive the Earth moving
(Instead the sun appears to move.)
•Ecliptic – The apparent path of the sun
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Summer
more direct sunlight,
sun appears to be higher in the sky.
 Higher on the ecliptic
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less direct sunlight
sun appears to be lower in the sky.
 Lower on the ecliptic
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Winter
spring and fall
we get equal light as the opposite
hemisphere.
(The sun in on the celestial equator).
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Therefore, the seasons are determined by the
suns position on the ecliptic.
Seasons
Summer Solstice - June 21 - 22. The sun is at the highest point
along the ecliptic. The first day of summer and longest day of
year.
Seasons
Summer Solstice - June 21 - 22. The sun is at the highest point
along the ecliptic. The first day of summer and longest day of
year.
Fall (Autumnal) Equinox - Sept. 22 - 23. The sun crosses the
celestial equator heading south. The first day of fall. Equal
length of day and night.
Seasons
Summer Solstice - June 21 - 22. The sun is at the highest
point along the ecliptic. The first day of summer and
longest day of year.
Fall (Autumnal) Equinox - Sept. 22 - 23. The sun crosses
the celestial equator heading south. The first day of fall.
Equal length of day and night.
Winter Solstice - Dec. 21 - 22. The sun reaches the lowest
point on the celestial sphere. The first day of winter and
the shortest day of the year.
Seasons
Summer Solstice - June 21 - 22. The sun is at the highest point
along the ecliptic. The first day of summer and longest day of
year.
Fall (Autumnal) Equinox - Sept. 22 - 23. The sun crosses the
celestial equator heading south. The first day of fall. Equal
length of day and night.
Winter Solstice - Dec. 21 - 22. The sun reaches the lowest point
on the celestial sphere. The first day of winter and the shortest
day of the year.
Spring (Vernal) Equinox - March 20 - 21. The sun crosses the
celestial equator heading north. The first day of Spring. Equal
length of day and night.
Seasons
Earth/Moon System
Scale Diagram of Earth/Moon System
What causes tides?:
Just as the Earth pulls the Moon, the moon also
slightly pulls on the Earth.
Tides Basics:
Tides:
-The moon pulls on everything on Earth.
-since water is fluid, the Earth cannot hold onto it and the
moon is able to pull on it.
-This creates two tides per day.
(The continents are also pulled, but much less so, only about
30 cm. This is not noticeable)
Tides:
Tidal forces created by one large body on another
Sun Tides:
Tides Caused by the Sun:
The Sun is also pulling on the Earth, causing tides,
but to a much smaller extent
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Spring Tides -When the Sun and Moon align,
and the gravitational pull combine, we get
extra high tides.
Neap Tides:
Neap Tides -When the Sun and Moon are at right
angles, the gravitational pull cancels, and we get extra
small tides.
Tides:
The Bay of Fundy between Nova Scotia and Main has
the worlds most extreme tides. Tides can raise and
lower by 48 feet.
http://www.youtube.com/watch?v=_J2AtORivSY
http://www.youtube.com/watch?v=SOAKZLwHhXU
http://www.youtube.com/watch?v=ycNzUAp6OXk
Tides:
Tides:
Tidal forces causes
1.The Rotation of the Earth to slow down.
1. (This Causes Precession)
Length of day = 6 hrs 4.5 billion years ago (formation of Earth)
Length of day = 20 hrs 300 Million years ago (Devonian time period)
Length of day = 23 hrs 80 million years ago (Cretaceous - Dinosaurs)
2. The moon to drifting away.
It drifts away 4 cm a year, which is slowly increasing the length of the month.
(Verified by Mirrors placed on Moon during Apollo Missions)
3. Tidal Locking.
Tidal Locking (Phase Locking)
Tidal Locking (Phase Locking)
Tidal Locking:
Although the moon rotates AND revolves, people on
Earth only see 1 side of the moon.
Tidal locking causes 1 rotation of the moon to be equal to
1 revolution of the moon
(1 rotation = 1 revolution)..
Tidal Locking (Phase Locking)
Tidal Locking (Phase Locking)
Tidal locking is normal. Objects that are tidally locked:
Moon to Earth
Phobos and Deimos to Mars
Most of Jupiter and Saturn's Moons.
Pluto and Charon
Probably Neptune's and Uranus's moons (not enough data)
Mercury to the Sun
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The moons orbit is not circular, it is elliptical.
This means the moons distance from earth
changes over the course of a month.
Moon Distance
Perigee vs Apogee
Perigee
and
Apogee
Moon Distance
Perigee vs Apogee
Scale diagram of Earth/Moon system
The Moon at Perigee and Apogee
Perigee - The moons closest approach to earth.
(356,000 km)
Apogee - The moons farthest distance from earth.
(407,000 km)
Moon Phases
Moon Phases
Caused by: the angle at which
we view the moon as it orbits the Earth.
Moon Phases
What is happening:
-The sun always shines on 1/2 of the moon.
- Depending on the angle at which we see the moon,
we see different parts of the moon lit up at different times.
Moon Phases
Moon Phases
Moon Phases
Lunar Eclipses
Cause of Eclipses
Cause of Eclipses
Lunar Eclipse –
Occurs when the moon passes through the
Earth’s shadow.
This only occurs during a FULL moon phase,
twice per year.
Lunar Eclipses
Lunar Eclipse Terminology
Umbra – The central, dark, shadow
of the Earth.
Penumbra - The outer, lighter, shadow
of the Earth.
Lunar Eclipse Terminology
Total Eclipse - The entire moon enters the
Earth’s Umbra.
Partial Eclipse – Only part of the moon
enters the Earth’s Umbra.
Lunar Eclipse Terminology
Partial Eclipse
Total Eclipse
Why is the moon RED during total lunar
eclipses?
-Only light scattered through the Earth’s
atmosphere strikes the moon. This
scattered light is red. (same reason why
sunsets/rises look red.
Lunar Eclipse Pictures
Lunar Eclipse Pictures
Solar Eclipses
Solar Eclipses
Solar Eclipse
Terminology
Solar Eclipse - When the
moon passes directly
between the Sun and
Earth, the moons shadow
will strike the Earth.
This only occurs during
a NEW Moon phase,
approximately twice per
year.
Why are Total Solar Eclipses much less
common?
Animated Solar Eclipse as seen from Space:
Notice the tiny size of the moon’s Umbra
Solar Eclipses as seen from Space:
Solar Eclipses as seen from Space:
From a weather satellite
Solar Eclipse Terminology
A.Total
B. Annular
C. Partial
Solar Eclipse Terminology
Total Eclipse - The Umbra of the moon strikes
the Earth. Anyone standing in this spot sees the
moon completely covering the Sun.
Solar Eclipse Terminology
Corona – The faint outer atmosphere of the
Sun. Only visible during Total eclipses.
Antarctic
Total Eclipse
Solar Eclipse Terminology
Partial Eclipse – The Penumbra of the moons
shadow strikes the Earth. Anyone standing in this
Spot sees the moon partially covering the Sun.
Solar Eclipse Terminology
Annular Eclipse – The moon passes directly in
front of the Sun. However, the moon is at Apogee,
and looks too small to cover the sun for a Total
eclipse.
Solar Eclipse Terminology
Ring of Fire – During an Annular eclipse, the
sun appears to be a ring surrounding the
moon.
Annular Eclipse
Annular Eclipse
Retrograde Motion
Retrograde Motion: Planets generally move from
west to east in the sky. Occasionally, a planet will
seem to slow down, stop, and loop backwards for a
short time.
Retrograde Motion of Mars
Retrograde Motion
Retrograde Motion: Planets generally move from
west to east in the sky. Occasionally, a planet will
seem to slow down, stop, and loop backwards for a
short time.
Reason Why:
The planet did not physically stop and move
backward. This illusion is created by the fact that
one of the planets passed the other in orbit.
(Similar to passing a car on a highway, the car being passed
appears to move backward)
Retrograde Motion
Retrograde Motion of Venus