Earth-Moon-Sun Systems Study Guide
 The impact theory explains that when Earth was molten a Mars-sized object crashed into
Earth. The debris from the impact settled into orbit around the Earth and gravity pulled it
together.
 Moon rotates once on its axis in the same time as it completes revolution around Earth.
This means only one side of the moon faces Earth.
 Maria- dark areas where lava covered the surface making basalt rock.
 Lunar Highlands- made of lighter rock and contain mountain ranges and many craters.
 Regolith- loose rock and dust on the moon (not soil).
TIDES- the periodic rise and fall of the ocean surface due to gravitational pulls of the moon and sun.
• HIGH TIDE- when water reaches the highest point on the shore.
• LOW TIDE- when water reaches the lowest points on the shore.
Gravity is stronger when objects are closer together therefore it is the moon that causes the tides rather than the sun.
• There are two tidal bulges because as earth spins, centrifugal force causes the water on the opposite side of earth to
also bulge.
• Tides are about 50 minutes later each day because the moon rises 50 minutes later each day. This is because the lunar
month is 29 days.
There are 2 high tides and 2 low tides per day.
• The sun also has an effect on tides but because it is much farther away its effect is about half of the moon's influence.
• SPRING TIDE-When the sun and moon are in line, their tide making effect is added together causing higher high tides.
• NEAP TIDE- When the sun and moon are at 90o from each other causing lower high tides.
There are 2 spring tides per month during full and new moons.
There are 2 neap tides per month during 1st quarter and 3rd quarter moons.
 Core: consists mostly of hydrogen and helium. Temperatures reach 15,600,000C.
 Radiative Zone: Around the core but is cooler than the core.
 Convection Zone: Rising and falling of plasma (charged particles) that carries energy to
sun's surface.
 Photosphere: visible surface of the sun with a temperature of 6,000C.
-Sunspots-dark spots that are cooler than the surrounding photosphere caused by
an increase in the magnetic field.
 Chromosphere: Inner layer of the sun's atmosphere with a temperature of 20,000C
causing the hydrogen within it to emit red light.
-Prominence-material ejected by the magnetic field.
 Corona: thin outer atmosphere with a temperature of 3,000,000C.
-Solar Wind- stream of electrically charged particles.
A lunar eclipse is an event during which earth’s shadow prevents the sunlight from reaching the moon. A
lunar eclipse can only occur at the full moon phase. Even though a full moon occurs every month, a lunar
eclipse occurs less often, because of the 5° angle between the plane of Earth’s orbit and the plane of the
moon’s orbit. The umbra is the area of total shadow. The penumbra is the area of partial shadow. When an
eclipse does occur, the moon usually remains visible, but has a reddish color. A total lunar eclipse may last as
long as 2 hours.
A solar eclipse occurs when the moon comes between the sun and Earth, and the moon’s shadow hits Earth’s
surface. A solar eclipse only occurs at the new moon phase. A total eclipse can last at most 7.5 minutes.
Although at least one solar eclipse occurs every year, a given area experiences a total solar eclipse only once
every three or four centuries.
1. Total Solar Eclipses occur when the umbra of the Moon's shadow touches a region on the surface of the
Earth.
2. Partial Solar Eclipses occur when the penumbra of the Moon's shadow passes over a region on the
Earth's surface.
3. Annular Solar Eclipses occur when a region on the Earth's surface is in line with the umbra, but the
distances are such that the tip of the umbra does not reach the Earth's surface.
The reason that the weather is warmer in summer and colder in winter for the northern hemisphere is not due
to the fact that the earth is nearer to the sun in summer and farther from the sun in winter.
The two factors which produce the seasonal effects are (1) the duration of sunlit hours experienced during each
season and (2) how directly the sun's rays strike the earth's surface.
These two factors are in essence due to a single factor, namely the inclination or tilt of the plane of earth's
equator with the plane of its orbit around the sun. Put another way, the axis of the earth is inclined 23 ½° from
the perpendicular to its orbit.
In summer, the northern half of the earth's axis is tipped toward the sun. In winter, the northern hemisphere of
the earth is tilted away from the sun.
Summer solstice - First day of summer in northern hemisphere. Northern Hemisphere is at maximum tilt to
the sun of 23.5%. Longest day in northern hemisphere. Shortest day in southern hemisphere. Sun is directly
above the Tropic of Cancer.
Winter solstice - First day of winter in northern hemisphere. Northern hemisphere at max tilt away from the
sun of 23.5%. Shortest day in northern hemisphere. Longest day in southern hemisphere. Sun is directly
over the Tropic of Capricorn.
Vernal equinox - First day of spring. Sun is directly over the equator. 12 hour of daylight in each hemisphere.
Autumnal equinox – First day of fall. Sun is directly over the equator. 12 hour of daylight in each hemisphere.