Earth’s Moon  It takes 27.3 days for the moon to revolve around the Earth relative to a background star (sidereal month).  Because Earth also revolves around the Sun, it takes 2 more days for the moon to line up with the Earth and Sun again - (cycles of the moon, 29.5 days). Known as the synodic month.

How does the moon affect the Earth?  Tide: rise or fall in the ocean surface  Gravitational attraction between moon, sun, and large bodies of water  The closer the moon is to the water, the stronger the pull; water on the side facing the moon is pulled more strongly toward the moon, producing a bulge and high tides.  

How does the moon affect the Earth?  Tide: rise or fall in the ocean surface  Gravitational attraction between moon, sun, and large bodies of water  The closer the moon is to the water, the stronger the pull; water on the side facing the moon is pulled more strongly toward the moon, producing a bulge and high tides. DG7RqQ9I DG7RqQ9I N-XVcpkE N-XVcpkE

Problem: Moon rises an average of 52.7 minutes later each day. You can use this formula: T N = T o + N x 52.7 minutes Where T N = the time of high tide in 7 days T o = the original time of high tide N = number of days later for which you want to determine the high tide If the original high tide is 1:00 pm, find the time of high tide in 7 days. TN = 1:00 pm + 7 x 52.7 min = 1:00 pm min = 1:00 pm + 6 hr 09 min = 7:09 pm

Moonlight  The Moon shines because it reflects sunlight from its surface  As Moon orbits the Earth, different areas of the side that faces earth reflects sunlight, causing Moon’s appearance to change

Phases of the Moon  New Moon – Occurs when the Moon is between the Earth and Sun  After new moon, moon phases are waxing (Moon appears to grow larger)  Waxing crescent - The first phase after new moon  First quarter Moon - About a week after new moon; half of Moon is visible  Waxing gibbous – from first quarter Moon until full Moon  Full moon – when side of the Moon facing us is entirely illuminated, Earth is between Moon and Sun

Phases of the Moon  After full moon, moon phases are waning (Moon appears to grow smaller)  Waning gibbous crescent – from full moon to 3 rd quarter Moon  3 rd quarter Moon -half of Moon is visible  Waning crescent –small sliver  New moon  If 2 full moons in one month (29.5 days/one lunar cycle), then second full moon is sometimes called a blue moon

Solar Eclipse When the moon moves directly between Sun and Earth and casts shadow on the Earth. Umbra - Darkest portion of the moon’s shadow Penumbra – lighter shadow on Earth’s surface that surrounds the umbra

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Lunar eclipse  When the Earth passes between the Sun and the Moon and casts a shadow on the Moon  Begins when Moon moves into Earth’s penumbra, moving into Earth’s umbra  Can only occur when Moon enters a full moon phase  Partial lunar eclipse: occurs when a portion of the Moon moves into earth’s umbra; the remaining portion of the Moon is in earth’s penumbra and receives some direct sunlight

Frequency of Eclipse  Total solar eclipse: Up to twice/year, but most people don’t see it  Only those people living in small area where moon’s umbra strikes Earth can see total solar eclipse  Total lunar eclipse – more frequently observed  because all of the Moon is in Earth’s umbra, so anyone on the night side of Earth could see it

Moon’s Surface Craters: depressions on the moon’s surface created by impacts from asteroids and comets Mountains (highlands): areas that were thrust upward from the impact events

Moon’s Surface o Maria: surface features which are dark colored, flat, lava filled regions  Created when cracks formed in the crust from the impact of asteroids/comets, the cracks allowed lava to flow into craters and fill them

Moon’s Surface o Regolith: layer of dusty lunar material produced by collisions between asteroids and comets and the Moon; can be up to 40 m thick

Moon’s Interior o Seismographs left on moon’s surface revealed  Crust  Mantle  Core o Maria on Moon’s surface suggests the interior of the moon must have been molten at one time

Origin of Moon Giant Impact Theory: o Moon formed about 4.4 billion year ago when Mars-sized object collided with Earth o The cores of the 2 bodies combined and settled toward the center of primitive Earth o Some gas and rock thrown into orbit; remainder condensed into mass which formed moon o Explains why Earth and Moon similar, but not identical

Earth Evidence for Earth’s shape as a sphere o No matter where you are on earth, objects fall straight down (gravity) o Earth’s shadow on the Moon during a lunar eclipse is always curved o People in different parts of the world see different stars at night

Earth’s shape o Gravity is responsible for Earth's shape o Astronomers think Earth formed as objects in solar system crashed into each other and combined because of gravitational attraction o Energy released as objects crashed into growing Earth to be molten o Gravity caused molten Earth to form sphere o As Earth cooled over time, different layers formed due to differences in density, becoming the inner core, outer core, mantle and crust

Earth’s Magnetic Field o Magnetic field: Scientists hypothesize it is the result of Earth’s rotation and the circulation of molten metals in outer core o Magnetic reversals: location of magnetic poles change over time; large-scale magnetic reversals occur on average every 200,000 years o Auroras: Sun produces solar winds (streams of electrically charged particles). The magnetosphere deflects these harmful particles, causing them to spiral along Earth’s magnetic field. They eventually collide with atoms and molecules in Earth’s atmosphere, causing them to emit light.

Planet Earth o The orbit of Earth around the Sun is elliptical. o An ellipse is an elongated closed curve with two foci. o The distance of the Earth to the Sun varies o The Earth is closest to the Sun in January (147 million km) and is farthest away in early July (152 million km)

Earth in the Solar System Venus o Venus nearly same size of Earth o Atmosphere contains 96% CO 2 (carbon dioxide) – Earth contains 0.04%. Earth’s oceans absorbed much of it o High CO 2 creates greenhouse effect – temperatures of +460°C (Earth average is 15°C). Mars o Slightly half the diameter of Earth; gravitational pull only 38% as strong, not strong enough to hold dense atmosphere so average surface temperature is -63°C o Mars lacks magnetic field, which allows atmosphere to be stripped away by solar wind