Transcript Earth - Moon System”

“Earth - Moon
System”
• I. Earth’s Motions:
A. Earth has 2 real motions.
1. Rotation- The turning or spinning motion of an
object on an axis.
* Axis- The imaginary line around
which an object spins.
* Earth’s axis is tilted at 23 1/2 degrees
from the perpendicular to earth’s orbital
plane.
Orbital Plane - The slice of space where an
object orbits
* For earth one rotation takes 24 hours.
Southern Night Sky from Paranal
Observatory in Chile
“Earth - Moon System”
• I. Earth’s Motions:
A. Earth has 2 real motions.
1. Rotation-
The turning or spinning motion
of an object on an axis.
* Axis- The imaginary line around
which an object spins.
* Earth’s axis is tilted at 23 1/2 degrees
from the perpendicular to earth’s orbital
plane.
A.) Orbital Plane - The slice of space
where an object orbits.
* For earth one rotation takes 24 hours.
2. Revolution-The circling of one object in space around
another object.
•Earth revolves around the sun at 107,826 Km/hr.
• Earth’s average distance from the sun is 93 million miles
or 150 million kilometers.
•Aphelion - When earth is
farthest away from the sun
(July 4th furthest away. 152
million km. )
•Perihelion - When earth is
closest to the sun.
(January 3rd closest to the sun.
147 million km)
* For earth one revolution takes 365.25 days.
There is a leap every 4 years, makes up for
the .25 days.
Sidereal vs. Synodic Motion (10
pts.)
1. Read through quietly to establish troublesome
vocabulary.
2. Read aloud together
3. Highlight/underline key points for questions
4. Answer questions.
•
Answer each question using 3-4 sentences.
Sidereal vs. Synodic Motion (10
pts.)
• Words we don’t know:
• Ecliptic - the great circle formed by the
intersection of the plane of the earth's orbit
with the celestial sphere; the apparent
annual path of the sun in space.
• Precession - A slow circular movement of
the earth's axis around the pole of the
ecliptic
Sidereal v. Synodic
• More words we didn’t know:
• Gregorian - relating to Pope Gregory XIII
or the Gregorian calendar
• Vernal Equinox - the time when daylight is
equal to nighttime in spring, on about
March 20 in the northern hemisphere and
September 22 in the southern hemisphere.
• Meridian - a circle of constant longitude
passing through a given place on the
earth's surface and the north/south poles.
Sidereal vs. Synodic Motion (10
pts.)
1. Which one, Sidereal or Synodic, is used to
define our day here on Earth? Describe it. (1
pt.)
2. Which one do you believe should be used to
define our day here on Earth? Why? (3 pts.)
3. Should we have a leap year? Why or why not?
(3pts.)
4. How many years have been leap years since 0
A.D.? (3 pts.)
•
Answer each question using 3-4 sentences.
Earth’s Seasons
• A. Why does earth
have seasons?
• B. Seasonal Dates:
1. Spring Equinox or Vernal Equinox:
* March 20/21
* First day of spring.
* Hours of daylight are the same in both
hemispheres.
2. Summer Solstice:
(Latin for “The Sun Stands Still”)
* June 21/22
* First day of summer.
* North Pole is tilted toward the
sun.
* Longest hours of sun light in the
Northern Hemisphere.
*Sun’s direct rays are on the
tropic of cancer.
(23 1/2 degrees North Latitude.)
* Continual Arctic Circle day
light.
* Called “land of the midnight sun”
.
3. Fall Equinox or Autumn Equinox :
* September 22/23
* First day of fall.
•Hours of day light
are the same in
both hemispheres.
Stop and Think
• Should we still use daylight savings time?
4. Winter Solstice :
* December 21/22
* First day of winter.
* North Pole is tilted away
from the sun.
•Shortest hours of sun light
in the Northern
Hemisphere.
* Sun’s direct rays are on
the Tropic of Capricorn.
(23 1/2 degrees South
Latitude.)
* Continual Arctic Circle
darkness.
* Land of the Mid-Day Moon.
Stop and Think
• What if there were no seasons?
“The Moon”
• I. Moon Characteristics:
A. Moon’s Rotation and Revolution:
1. Moon’s Rotation = It’s Revolution.
2. This is why the same side of the moon
faces the earth at all times.
3. 29.5 days to travel around the Earth
(to Sun).
B. Moon Structure:
1. Craters cover the surface.
2. First thought to be volcanic craters.
3. Now we know that meteorite impacts
caused them.
4. Rays- Streaks extending out
from craters. Caused by violent
meteorite impacts
5. Maria- (Latin for seas or oceans)
Low areas of dark soil where
ancient lava flows covered the
surface.
6. Marias were first thought to be
seas or oceans by early astronomers.
7. The moon also has mountains
(terra/highlands) as large as any on
earth.
• II. Phases of the moon:
A. The moon takes 29 1/2 days to complete all
of its phases.
B. Phase Shapes:
1. Crescent - Banana shaped.
2. Quarter - Half-moon.
3. Gibbous - 3/4 of a circle.
4. Full - Complete circle
5. New - Not visible.
C. Phase Stages:
1.
Waxing means to become brighter.
New to full moon.
2. Waning means to become dim. Full to
new moon.
D. The Phases of the Moon:
1. New Moon
2. Waxing Crescent
3. 1 st Quarter
1
2
3
4
5
6
7
8
9
4. Waxing Gibbous
5. Full Moon
6. Waning Gibbous
7. 3 rd or Last Quarter
8. Waning Crescent
9. New Moon
III. Eclipses:
A. Eclipse- The passing of one object into
the shadow of another object.
B. Total Eclipses - When the object is fully eclipsed.
1. The eclipsed object must be
completely in the umbra of the other
object.
2. Umbra - The complete inner shadow of
an object.
C. Partial Eclipses - When the eclipsed object
is partially in the umbra and partially in the
penumbra of the other object.
1. Penumbra - The partial shadow of an object.
D. Lunar Eclipses:
1. The full moon is in the earth’s shadow.
2. Approx. 2hrs. In length.
3. More often seen than solar eclipses.
Full Lunar Eclipse
penumbra
umbra
penumbra
Partial Lunar Eclipse
penumbra
umbra
penumbra
E. Solar Eclipses:
1. The earth is in the shadow of the new
moon.
2. Length from 4 - 8 minutes.
3. Less often observed than lunar eclipses.
4. Very bright, dangerous eclipse.
5. Never look directly at it.
6. Brightest part of the sun (the corona)
can be seen. (Will permanently damage
the eyes.)
Full & Partial Solar Eclipse
umbra
penumbra
penumbra
• IV. The Moon’s Origin:
The Fission Theory: The Moon was once part of the Earth and somehow separated
from the Earth early in the history of the Solar System. The present Pacific Ocean basin
is the most popular site for the part of the Earth from which the Moon came.
The CAPTURE Theory: The Moon was formed somewhere else, and was later
captured by the gravitational field of the Earth.
The (CO-ACCRETION) : The Moon and the Earth condensed together from the original
nebula that formed the Solar System.
The COLLISION RING Theory: An object the size of Mars struck the earth, ejecting
large volumes of matter. A disk of orbiting material was formed, and this matter
eventually condensed to form the Moon in orbit around the Earth.
• V. Tides:
A. Tides- The periodic rise and fall of the ocean due
to the gravitational pull of the Moon and Sun.
1.) When the ocean levels are highest it is said
to be high tide, and when they are the lowest it
is said to be low tide.
B. Tidal Range- Is the difference in water level
between high tide and low tide.
C. The moon effects tides more than the Sun
because it is closer to the Earth.
D. Because of this, the Sun either increases the
effect of the Moon or decreases the effect.
1.) Spring Tides- A tide of large range that
occurs during the new moon phase or full
moon phase.
* The Sun increases the effect of the
Moon.
1.) Neap Tides- A tide of small range that
occurs during the 1st quarter phase or 3rd
quarter phase.
* The Sun decreases the effect of the
Moon.