Transcript Sun, Earth, Moon Relationship

What is the difference between
rotation and revolution?
2. What causes the seasons?
3. True/False: The Earth has an axial
tilt.
1.
Objective: Understanding how the Sun, Earth and
Moon move relative to one another and how they
affect each other.

Axis – an imaginary line around which an
object spins; 23.5°

Aristotle
 350BC, knew the world was round due to Earth
always casting a round shadow during an eclipse
Apparent Motion – what seems
to be happening
Real Motion – what really is
happening
1. Sun rises in the East and sets in
the West
1. Earth is rotating on its axis
2. Sun and stars travel in an arc
across the sky
2. Earth is rotating
3. Moon appears and disappears in 3. Moon revolves around (orbits)
phases
the Earth
4. Earth changes temperature with 4. Earth orbits the sun and is tilted
seasons
23.5°
5. Solar day is 24 hours
5. Actual day 23 hours 56 minutes 4
seconds. Shorter than 24 hours
because of Earth’s revolution
around the sun.
Rotation
Revolution
• Turning/spinning of Earth on it’s axis
• Movement of Earth and planets
around the Sun
• Path of revolution is one orbit
• Once every 24 hours (approximately)
• Once every year (approximately)
Causes:
Causes:
• Celestial bodies appear to move in an
arc across the sky
• Change in duration of sunlight at
different latitudes
• Length of day (24 hours)
• Changes in temperature with seasons
(along with tilt)
• Direction of sunrise (East) and sunset
(West)
• Change in angle of sunlight at different
latitudes (tilt)
• Coriolis Effect (bending of winds and
ocean currents)
Winter Solstice
Summer Solstice
• Northern hemisphere is tilted
away from the Sun
• December 21st
• Sun shines directly on Tropic of
Capricorn
• Longest hours of darkness
• Northern hemisphere is tilted
towards the Sun
• June 21st
• Sun strikes Earth at an angle of
90 degrees at the Tropic of
Cancer
• Long hours of daylight
**The hemisphere tilted towards the sun receives the most
radiation and more daylight hours**
Spring (Vernal) Equinox
Fall (Autumnal) Equinox
March 21st
September 23rd
Equinox – days when the amount of sunlight and
darkness is EQUAL; sun is directly over the equator

Reasons for Seasons
 Caused by differences in absorbed solar energy due to
Earth’s axial tilt and revolution around the Sun

Reasons for Length of Day
 Axial tilt
 Tilted away from the Sun = less time facing the Sun =
shorter day
 Tilted towards the Sun = more time facing the Sun =
longer days

Ellipse – a closed curve around 2 fixed points known as
foci; path of the Earth

Aphelion (apogee) – point where Earth is farthest from
the Sun (July 4th)

Perihelion (perigee) – point where Earth is closest to the
Sun (January 2nd)
1.
Orbits of the planets around the sun are
ellipses, with the sun at one of the foci.
2.
An imaginary line joining planet to the sun
will sweep out equal areas in equal periods of
time.
3.
The father a planet is from the sun, the
longer its year.
Geocentric Model
Heliocentric Model
• Earth at the center of the solar
system
• Sun at the center of the solar
system
Explains:
Explains:
• Daily motions of sun, planets
and stars in the sky
• Retrograde motion or “backing
up” of planets in the sky (due to
farther planets moving slower)
• Sort of explains why some
planets appear to “back up” in
their path across the sky
(retrograde motion)
• Apparent diameter changes of
moon and planets
• Phase changes of Venus

Accepted model of the solar system

Proof:
 Foucault Pendulum: path changes due to rotation
of the Earth
 Coriolis Effect: deflection of objects to the right in
the Northern Hemisphere due to Earth’s rotation

A major misconception is that the seasons
are caused by the Earth being closer to the
Sun in the summer and farther from the Sun
in the winter due to Earth’s elliptical orbit.
 Explain why this idea is a misconception. What
really causes winter in the Northern Hemisphere
and summer in the Northern Hemisphere?