Earth’s MoonIt 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 surfaceGravitational attraction between moon, sun, and

large bodies of waterThe 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.

https://www.youtube.com/watch?v=5ohDG7RqQ9I https://www.youtube.com/watch?v=IIMN-XVcpkE

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.

• https://www.youtube.com/watch?v=5ohDG7RqQ9I

• https://www.youtube.com/watch?v=IIMN-XVcpkE

Problem: Moon rises an average of 52.7 minutes later each day. You can use this formula:

TN = To + N x 52.7 minutes

Where TN = the time of high tide in 7 days

To = 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 + 369 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 MoonNew Moon – Occurs when the Moon is between the

Earth and SunAfter new moon, moon phases are waxing (Moon

appears to grow larger)Waxing crescent - The first phase after new moonFirst quarter Moon - About a week after new moon;

half of Moon is visibleWaxing gibbous – from first quarter Moon until full

MoonFull 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 3rd

quarter Moon3rd quarter Moon -half of Moon is visibleWaning 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

Videos

https://www.youtube.com/watch?v=NCweccNOaqo

https://www.youtube.com/watch?v=xBc8QHSsFgE

Lunar eclipseWhen 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 itOnly 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 Interioro 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 sphereo 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 Fieldo 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 Eartho 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

Venuso Venus nearly same size

of Earth

o Atmosphere contains 96% CO2 (carbon dioxide) – Earth contains 0.04%. Earth’s oceans absorbed much of it

o High CO2 creates greenhouse effect – temperatures of +460°C (Earth average is 15°C).

Marso 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