Transcript Lunar eclipses

The Earth, Moon, and Sun
System
SOL 6.8
Introduction
In this presentation we will learn:
 About the relative sizes, motions, locations, and
characteristics of the earth, sun and moon.
Vocabulary includes: rotation, revolution, axis of rotation, orbital plane,
periods of rotation and revolution, mass, diameter, radius of orbit, density,
composition, surface, core, atmosphere.
 The effects of their motions and positions on our
seasons, tides, eclipses, and the measurement of
time.
Vocabulary includes: seasons, high and low tides, phases of the moon,
equinoxes, solstices, perihelion, aphelion, day, night, month, year, solar
and lunar eclipses.
Lets compare all three
heavenly bodies
for a minute!!
We’ll start with the Sun
The Sun
A G2 typical yellow dwarf star
 Diameter: 1.4 million kilometers
 Contains 99.8% of the mass of
the solar system
 Composition: 75% hydrogen,
25% helium
 Surface Temperature: 5500 oC
 Core Temperature: 15 million
degrees Celsius
 Rotates on its own axis once
every 25.4 days at the equator.
 Revolves around the center of
the Milky Way Galaxy once
every 225 million years.
The Earth
 Diameter: 12.7 thousand
kilometers
 Mass: 6.0 x 1024 kilograms or
six sextillion metric tons
 Composition: water, silicon,
heavy metal iron-nickel core
 Atmosphere: nitrogen, water
vapor, oxygen, carbon dioxide
 Surface Temperature: -13 –
37oC
 Called the “Blue Planet”
because of the color of nitrogen
in it’s atmosphere.
Earth’s Movement
 The Earth rotates on an axis that is tilted 23 ½ degrees
relative to the orbital or ecliptic plane.
 It’s period of rotation is one day or 23 hours and 56
minutes.
 The period of revolution around the Sun is a year or 365
and one-quarter days.
 Why do we have leap years every four years?
 The earth completes this elliptical orbit at an average
radius of 150,000,000 kilometers from the Sun.
 It travels through 942 million kilometers of space during its
elliptical orbit, and travels at a speed of 100,000 km per
hour to finish that path in one year.
 The earth is also wobbling back and forth along its orbit
because of the movement of the moon.
The Moon
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Diameter: 3.4 thousand kilometers
(about ¼ of the diameter of the
earth)
Mass: 7.36 × 1022 kilograms or
about 1/80 of the mass of the earth
Composition: similar to the earth’s
crust
Atmosphere: because of little
gravity the moon basically has no
atmosphere
Surface covered with craters and
mares (flat seas of rock)
Surface Temperature: -233 – 123 oC
The moon always shows the same
side to Earth
What is the collision theory about
how the moon was formed?
The Movements of the Moon
 The Moon rotates on an axis that is not tilted very much
relative to the Earth.
 It’s period of rotation is 27.3 days.
 The period of revolution around the Earth is 27.3 days as it
completes a near circular orbit at an average radius of 384,000
kilometers.
 What do these last two facts mean?
 That’s right. We are always looking at the same side of the
moon from the Earth. Actually we can see a little more around
the edges, but only 55% of the lunar surface is visible from the
earth.
 It travels through 2.4 million kilometers of space during its
slightly elliptical orbit, and travels at a speed of 3700 km per
hour to finish that path in one month.
 The moon looks as much as 11% bigger or smaller because of
the apogee, perigee, and tilt of its orbit relative to the earth.
 The moon’s orbital plane is 5 degrees tilted compared to the
Earths ecliptic plane.
Let’s see what you know!!
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Which one is the smallest?
Which one is the densest?
Which one has the greatest mass?
Which is spinning fastest on its axis?
Which one is spinning slowest?
Which one has the longest orbit?
Which is moving fastest? Be careful on this one!!
Now let’s see how they are related!!
 The moon is constantly revolving around the
Earth as the Earth revolves around the Sun.
 The appearance of the lit side of the moon
causes a change in the appearance of the
moon called a phase.
 Lets look closer at phase changes and other
things related to this movement.
Phases of the Moon
The Moon Phases and Tides
 Tides are periodic rises and falls of large bodies of
water. Tides are caused by the gravitational
interaction between the Earth and the Moon.
 The gravitational attraction of the moon causes the
oceans to bulge out in the direction of the moon.
Another bulge occurs on the opposite side, since
the Earth is also being pulled toward the moon
(and away from the water on the far side).
 Since the earth is rotating while this is happening,
two tides occur each day.
 Isaac Newton (1642 -1727) was the first person to
explain tides scientifically. His explanation of the
tides (and many other phenomena) was published
in 1686, in the second volume of the Principia.
Take a Look!!
Variations in Tides
What two dates would have the highest tides?
How many times a day do high tide
and low tide happen?
 Tides at the Chesapeake Bay Bridge Tunnel
2004-04-22
4:47 AM EDT
Low Tide
0.20 feet
2004-04-22
10:53 AM EDT
High Tide
2.44 feet
2004-04-22
4:38 PM EDT
Low Tide
0.24 feet
2004-04-22
11:08 PM EDT
High Tide
2.92 feet
2004-04-23
5:24 AM EDT
Low Tide
0.34 feet
2004-04-23
11:30 AM EDT
High Tide
2.33 feet
2004-04-23
5:16 PM EDT
Low Tide
0.35 feet
Besides tides and phases, the
moon’s movement is also
responsible for two common
events called solar and lunar
eclipses.
Facts about Eclipses
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Eclipses are caused by a shadow being
cast on the moon or the earth.
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When the moon cast a shadow on the
Earth it is a solar eclipse (The sun is
blocked from view)
When the Earth casts a shadow on the
moon it is called a lunar eclipse (we can
not see the moon)
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Lunar eclipses do not occur as
frequently as total solar eclipses, but
they are visible from anywhere on the
side of Earth facing the Moon during the
evening. (seen most often)
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A total solar eclipse can only be seen
from a narrow band about a hundred
miles wide at most, and while up to
seven of these a year are not unusual,
they frequently occur over the most
inaccessible regions on the planet.
(most common) (least seen)
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Even when 99% of the Sun's surface is
obscured during the partial phases of a
total eclipse, the remaining crescent is
intensely bright and cannot be viewed
safely without eye protection. Failure to
use appropriate filtration may result
in permanent eye damage or
blindness.
Eclipse Schedules - 2004
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Apr. 19. Partial eclipse of the Sun. Visible in Antarctica, southeast Atlantic
Ocean, southern half of Africa and Madagascar.
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May 4. Total eclipse of the Moon. The beginning of the umbral phase visible in
Asia except extreme northeast, Europe except western region, Africa except
northwestern part, Indonesia, Australia, New Zealand, Antarctica except part of
the peninsula, the eastern South Atlantic Ocean, the Indian Ocean, and the
western Pacific Ocean; the end visible in Africa, Europe, western Asia, western
Australia, Antactcia, South America except the southwestern part, the eastern
North Atlantic Ocean, the South Atlantic Ocean, the Indian Ocean, and the
extreme southeastern South Pacific Ocean.
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Oct. 14. Partial eclipse of the Sun. Visible in Northeast Asia, Japan, western
Pacific Ocean, Hawaiian Islands, and the western part of Alaska.
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Oct. 28. Total eclipse of the Moon. The beginning of the umbral phase visible in
Africa, Europe, Greenland, the Arctic region, North America except the extreme
northwest, Central America, South America, extreme western Asia, part of
Queen Maud Land and the peninsula of Antarctica, the Atlantic Ocean, the
eastern South Pacific Ocean, and the western Indian Ocean; the end visible in
North America, the Arctic region, Greenland, Central America, South America,
Europe, western Africa, Antarctic peninsula, the eastern Pacific Ocean, and the
Atlantic
Models of Solar Eclipses
Model of a Lunar Eclipse
The Earth is moving around the
Sun and is tilted on an axis
relative to the orbital plane.
What kinds of things does this
cause?
What Causes the Seasons?
Check this out!!
 In the below animation, you can see the Earth during one
full year (the animation then starts over again), as you
would if you looked straight at it from the Sun. As you can
see, the part of the Earth that is directly facing the sun
changes with the time of the year. It is the northern half for
a while, then moves south of the equator, only to move
back to the north again.
Kind of makes you dizzy thinking
about it, doesn’t it?
 A common myth is that the seasons are caused by the
changing distance between the Earth and the Sun.
 The info below disproves that myth.
 The aphelion is the furthest distance from the Sun, and the
perihelion is the closest distance to the Sun.
 Notice that the perihelion happens during the winter and
the aphelion in the summer.
Perihelion
Aphelion
Equinoxes
Solstices
Jan 4 18
July 5 11
Mar 20 06 49
June 21 00 57
Sept 22 16 30
Dec 21 12 42
Equinoxes and Solstices
 The official date beginnings of the seasons are the
equinoxes and the solstices.
 Summer begins on the summer solstice (the longest day of
the year)
 Fall begins on the autumnal equinox. (equal night 12h/12h)
 Winter begins on the Winter solstice (the shortest day of
the year)
 Spring begins on the vernal equinox. (equal night)
 In 2004 these occur on:
 Equinoxes
Mar 20 06 49
Sept 22 16 30
 Solstices
June 21 00 57
Dec 21 12 42
What would happen if…
 the earth’s axis was not tilted toward or
away from the sun?
 the earth’s axis was tilted more than 23.5
degrees?
 The earth’s axis was tilted less than 23.5
degrees?
Time Goes On
 A day is the time it takes for the Earth to complete
one rotation on its axis.
 A year is the time it takes for the Earth to complete
one revolution around the sun.
 A month is the time it takes for the moon to
complete one revolution around the earth and one
rotation on its axis.
 A week is 7 days long, which is the time it takes to
go through one phase of the moon.
 Monday is “moon” day, and Sunday is “Sun” day
 What would happen to time measurement if the
earth started rotating twice as fast on its axis?
Do You Understand?
 What causes the seasons?
 Tides are caused by the tilt
of the Earth. T or F
 What are the highest tides
called?
 If your days are shorter
than twelve hours long and
getting shorter all the time
what season are you?
 What do we call the
longest day?
 If your days are longer
than twelve hours and
getting longer all the time,
what season are you?
 What type of eclipse
happens most often?
 What type of eclipse is
seen more often?
 What calendar time
periods are related to the
movement of the moon?
September
Summer
October
Fall
November
Autumnal Equinox
August
Sept. 22
July
Aphelion – July 5
December
Summer Solstice
Winter Solstice
June 21
Dec. 21
June
Perihelion – Jan. 4
Winter
January
March 6,1959
May
Vernal Equinox
Spring
Mar 20
April
February
March