NotesIII. The Earth, Moon, Sun System A. Movements of the Earth 1. Rotation: Spin of the earth on its axis. - Takes 23 hours, 56min to complete - Gives us day and night
2. Revolution:The Earths motion in its orbit around the sun. a. The Plane of the Ecliptic: The plane which contains the Earths orbit around the sun. This motion takes one year to complete.
b. The Earths Tilt: The earth does not rotate perpendicular to the plane of the ecliptic. It has a 23.5 degree tilt.- The star closest to the north rotational axis is Polaris, the north star. The Earths axis points in thisdirection throughout the year.
c. The Seasons: The direction the Earths axisremains pointed in the same direction all year. Soas it travels in its orbit, it appears to changedirection relative to the sun. This motion takes one year to complete.
d. The Four Seasonal Positions of the EarthJune Solstice: The day with the longest period ofdaylight, and the most direct rays from the sun.Marks the beginning of summer. The reverse forthe southern hemisphere.December Solstice: The day with the shortestperiod of daylight, and the least direct rays fromthe sun. Marks the beginning of winter. Thereverse for the southern hemisphere.
d. The Four Seasonal Positions of the EarthEquinox: The day in which there will be roughly 12hours of night and 12 hours of day. - Vernal Equinox: March 21st (marks start of spring) - Autumnal Equinox: September 21st (marks start of fall)
d. The Zodiac: The twelve constellations the sun appears to pass through during the year.These constellationsencircle the ecliptic ecliptic- Your “sign” is determined by the constellation thecovered by the sun when you are born.- You CANNOT see your constellation at night onyour birthday. You have to wait roughly 6 monthsbefore it rises high in the sky
- The twelve constellations of the Zodiac.There are twelve constellations: Pisces, Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius (this is the correctorder)- Ancient peoples would often associate different traits to the planets, and asthe planets moved through the various constellations they predicted things thatwould happen in your life.
Notes A. Movements of the Earth 3. Procession: The wobble of the earth on its axis - The earth maintains its 23.5 degree angle but the direction the axis points changes. Moving in a circle. - Think of a top spinning on its axis. The vertical axis begins to wobble over time. - This motion of the earth causes the north star to change.
B. Motion of the Moon 1. The moons orbital period is 27.3 days. The time it takes to go all the way around the earth. 2. The moons rotational period is ALSO 27.3 days. This is why only one side of the moon faces the earth. (more to come) - Not because its not rotating, because it rotates at the same speed it revolves.
3. The Phases of the Moon- As the moon moves around the Earth, it appearsto change shape. The ENTIRE moon is still present,but different portions are illuminated.
3. Phases of the moon (continued) New moon: None is illuminated Waxing Crescent: Sliver is visible First Quarter: Half-Full Waxing Gibbous: Mostly Full Full Moon: 100% Illuminated
3. Phases of the moon (continued) Waning Gibbous: Mostly Full Third Quarter: Half-Full Waning Crescent: Sliver visible
d. Eclipses: When one object passes into the shadow ofanother object. - Total Lunar Eclipse: When the entire moonpasses into the earths shadow. - Partial Lunar Eclipse: When part of the moonpasses into the earths shadow.
d. Eclipses: When one object passes into the shadow ofanother object. - Total Solar Eclipse: When the moon completelycovers the sun placing part of the earth inshadow.. - Annular Eclipse: When the moon overlays thesun but does not block it out completely.- Partial Solar Eclipse: When only part of the moonpasses over the face of the sun.
Notes 4. Effects of the Moon on the Earth a. Tidal bulging: The stretching of the Earth along the earth-moon line. - This effect happens whenever one body moves around another body in space. - This happens because the earth is STRECHED by the gravity of the moon, not because the moon is pulling the anything towards it. - On earth this is noticed as high and low tides in the oceans.
B. Motion of the Moon 2. Tides: Noticeable daily changes in ocean depth caused by the gravitational attraction between the earth moon and sun. a. Spring Tides: Take place when the Earth, Moon & Sun are lined up. Cause higher then average high tides and lower then average low tides. a. Neap Tides: Take place when the Earth, Moon & Sun are at right angles to eachother. Cause the smallest change between high and low tides.
3. Tidal Friction: Friction generated as an object rotatesthrough tidal bulges. a. Two Effects of Tidal Friction: - Causes the rotation of the bodies to gradually slow - Causes the bodies to move further apart. b. Eventually tidal forces stop both bodies from rotating relative to one another. So that only one side of each faces the other. - This is called Synchronous Rotation. - Because the gravity of the earth is much stronger then the gravity of the moon. The moon is already in a synchronous rotation with the earth.
4. Features of the Moon a. Maria: Large dark areas on the moons surface. - Large flat plains formed during an earlier volcanic period in the moons evolution. Lava filled in many of the old craters, leaving what appeared to be seas. b. Highlands: lighter coloured areas with elevations several kilometres above the Maria. a b
4. Features of the Moon (continued) c. Craters: Circular depressions formed when objects impact the moon.