This is a powerpoint lecture on the earth/moon/sun relationship for the HPU NCS2200 earth science for elementary education summer 2014 online course

1. Earth-Moon-Sun
Relationships

2. Earth Movement Through Space
• Revolution – movement around the sun
– 1 revolution takes ~365 days = 1 year
• Rotation – movement on its axis
– 1 rotation takes ~ 24 hours = 1 day
• Precession – the change in the earth’s tilt on its
axis
– Changes the angle of earth’s tilt approximately every
20,000 years

3. Precession of Earth

4. Precession Video
http://www.columbia.edu/itc/ldeo/mutter/jcm/Topic2/axial2.html

5. Barycenter
• Barycenter –the
point between two
objects where they
balance each other
– The center of the
mass between the
Earth and the Moon

6. Earth’s Shape
• Earth is not perfectly
round but bulges due to
the gravitational and
rotational effects of the
Moon and the Sun on the
Earth
• Gravity of an object pulls
in toward its center.
• Rotational forces act to
push out.
• These two forces pull at
the Earth in different
proportions causing the
less than spherical
shape.

7. Motions of Earth and the Moon
• Full moon – rises at about sunset
– Each night it rises 53 minutes later because it
moves ahead of the earth by 12o each night
– The moon does not emit light, it reflects
sunlight
– The Moon’s plane of orbit is tilted 5.2o
above the earth’s equatorial plane.
• Thus the Earth’s shadow doesn’t always cover it
up

8. Earth-moon Geometry
Notice the angle of the moon’s revolutionary plane with respect to the earth’s
Revolutionary plane. This places the moon above or below the earth’s path
Thus placing the moon only RARELY in the direct shadow of the Earth.

9. Motions of the Earth and the Moon
• Normally we see the PHASES of the moon as it
revolves around the earth.
• Revolves around Earth in 29.5 days
• The Phases of the Moon
– New moon – when the moon is dark
– Crescent moon – four days later
– Gibbous moon – bright moon 10 days after
– Full moon – 14-15 days after the new moon
– Waning moon – as it shrinks toward the next
new moon

10. Fig. 22.17, p.570

11. Lunar Eclipse
• Since I am NOT the expert here I am
going to let the expert speak for himself.
• Click the link to go to Mr. Eclipse’s website
and read all about Lunar Eclipse. Then
come back here and we’ll see what we
can summarize about this phenomenon
• http://www.mreclipse.com/Special/SEprim
er.html

12. Summary of Lunar Eclipse
• Pretty Cool!
• So basically the Lunar
eclipse occurs when
the moon passes
through the preumbra
or umbra shadow of
the earth – but this
only happens when
the moon is in the
same plane as the
earth!
The activty to build your sun-earth-moon
Model will help with this understanding!

13. Moon-Earth Forces
• Tides are caused by the gravitational
attraction of the Moon and Sun.
• The Moon's effect is about 54% of the total
gravitational force
– although the Sun outweighs the Moon by a
factor of 10 million the fact that it is 400 times
further away than the Moon gives the Moon
has gravitational edge

14. Tides
• Changes in tide
height is related to the
rotation of the earth
and the revolution of
the moon around the
Earth.
• The water “bulges” in
response to the
gravity of the moon.

15. Tides
• Spring Tides are the
HIGHEST tides and
occur when the Sun,
Moon and Earth are
aligned
• Neap tides are the
LOWEST tides and
occur when the Sun,
Moon and Earth are
at a 90 degree angle
to each other.

16. Tidal Force Video
• This video from Nottingham university is a
really good explanation of tidal forces (and
the accents are cool to listen to as well!!!)
• http://www.sixtysymbols.com/videos/tides.
htm

17. Seasons and Sun Energy
• The Seasons are caused by the TILT of
the Earth and its REVOLUTION around
the sun.
• As the earth revolves, the tilt of the earth
exposes parts of the world to more or less
direct sunlight, changing the amount of
energy absorbed and thus the
temperatures of the Earth.

18. Fig. 18.12, p.461

19. Tilt and Solar Energy
• The tilt and curvature of the Earth causes the
Sun’s rays to strike the Earth at different
angles.
• The higher the angle of incidence (the angle
the Sun’s rays strike the Earth) the more
spread out the energy is and the less energy
is absorbed.
• The higher the latitude, the greater the angle of
incidence thus,
– Solar energy is GREATER at the EQUATOR and
LOWER at the POLAR

20. Fig. 18.10, p.460

21. Fig. 18.11, p.460

22. Sun Earth Moon Summary
• Earth Revolves around Sun
– Creates seasons due to tilt of earth’s polar
axis relative to rotational plane
– Angle of incidence of sun to earth’s curvature
creates temperature differences  sets up
global climate sectors
• Earth “wobbles” on its axis – precession
• Earth-moon gravitational pull creates a
barycenter – an offset center of gravity

23. Sun-Earth-Moon Summary
• Moon Revolves around Earth
– Moon revolves around the earth 29.5 days
– Moon’s elevation off the Earth’s rotational
plane creates the moon phases
– Barycenter created with the earth due to
uneven gravity between the two
– Moons gravitational pull creates tides
• Neap tide – lowest tide when Sun-Earth-Moon at
90 degrees
• Spring tide – highest tide when Sun-earth-Moon
are in alignment.

24. Sun Facts