Classwork Sun Moon Earth System
Classwork Sun Moon Earth System Name ____________________ Date____
Daily Motions
Sun, Moon, planets, and stars rise in the East and set in West
These daily motions occur as a result of Earth’s rotation
How do we know Earth is rotating? Two ways:
1. Foucault pendulum swings in a constant direction; due to Earth’s rotation, it appears that the pendulum shifts; can see this when place pegs on floor and pendulum knocks pegs down
2. Flowing air and water diverted from north-south direction to east-west direction
Annual Motions
We know Earth rotates around the sun because:
1. See weather changes, 2. day length changes, 3. temperature changes as result of Earth’s motion around the Sun
ecliptic - The plane in which Earth orbits the Sun
Effects of Earth’s Tilt
Earth’s axis tilted to the ecliptic at 23.5 degrees
As Earth orbits Sun, orientation of the Earth’s axis remains fixed so at one point the northern hemisphere is tilted toward the sun, and at another point 6 months later, the northern hemisphere is tilted away from the Sun.
Solstices -
During summer solstice, Sun is at highest altitude in the sky (June 21); number of daylight hours at maximum
Summer solstice-Sun is directly overhead at Tropic of Cancer (23.5N latitude)
During winter solstice, the sun is at its lowest altitude in the sky (Dec 21); number of daylight hours at minimum; Sun is directly overhead at Tropic of Capricorn (23.5S latitude)
Equinoxes
Two positions Earth is not pointed at Sun; as result both hemispheres receive same amount of sunlight and Sun is directly overhead at the equator
Called autumnal and vernal equinox (equinox means “equal nights”)
Tides
Moon affects Earth by the formation of tides
Moon’s gravity pulls on Earth along imaginary line connecting Earth and the Moon that creates bulges of ocean water on both the near and far sides of the Earth
Earth’s rotation contributes to tide formation
As Earth rotates, these bulges align with the Moon
Person at shoreline on Earth’s surface would see ocean level rise every 12 hours
Sun’s gravitational effect (about ½ of the Moon’s) not as strong as the Moon’s because further away from the Earth
When Sun and Moon are aligned, see stronger tides because effects are combined
These higher tides are called spring tides and they are high when Moon is nearest Earth and Earth is nearest the Sun
Lower than normal tides, or neap tides, occur when the Moon is at a right angle to the Sun-Earth line
Solar Eclipses
A solar eclipse occurs when the Moon passes directly between the Sun and the Earth and blocks our view of the Sun
When the Moon perfectly blocks out the Sun’s disk, we only see the dim, gaseous outer layers of the Sun; this is called a total solar eclipse
Partial solar eclipse seen when the Moon blocks a portion of the Sun’s disk
The difference between a partial and total solar eclipse can be explained by the fact that the Moon casts a shadow on Earth.
Shadow consists of two regions: inner portion called the umbra that doesn’t receive direct sunlight, and an outer portion called the penumbra that receives some sunlight
People who witness eclipse from the umbra (inner portion) see a total solar eclipse
People who witness eclipse from the penumbra (outer portion) see a partial solar eclipse
Umbral shadow very small (~270 km), so total solar eclipse visible from small portion of Earth
Solar Eclipse
Effects of Orbits
Only when the Moon intersects the Earth’s ecliptic in line with the Sun and Earth does a solar eclipse occur
Closest point in Moon’s orbit around Earth is called the perigee
Farthest point in Moon’s orbit around the Earth is the apogee
When Moon is near apogee, appears smaller from Earth and can’t block out Sun entirely
When Moon is near perigee, appears larger on Earth and can block out Sun entirely
Lunar Eclipse
Lunar eclipse occurs when Moon passes through Earth’s shadow
Can only happen during a full moon when the Moon is in the opposite direction from the Sun
Earth has two parts to its shadow like the moon: umbral and penumbral
When entire Moon is in the Earth’s umbral shadow, you can see a total lunar eclipse
Total lunar eclipse lasts approximately 2 hours; can see a Moon during this phase because sunlight that has passed near Earth has been refracted by Earth’s atmosphere
Gives light a reddish appearance
Periodicity of Eclipses
Solar and lunar eclipses don’t occur every full moon because the Moon in orbit usually passes above or below the Sun as seen from Earth
Solar and lunar eclipses occur in almost equal numbers, with slightly more lunar eclipses
Maximum number of combined eclipses that can occur per year is seven; this won’t happen again until 2038
Assignment:
Using your notes and/or your textbook, make flash cards to show each of the following (draw it on one side, identify it on the other side):
Earth’s tilt
Ecliptic
Autumnal Equinox
Vernal Equinox
Apogee and perigee
Solar eclipse
Lunar eclipse
Moon surface features
EM spectrum (radio waves …. Gamma waves)
Latitude and longitude lines; equator and Prime Meridian
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