Moon’s
phases






Eclipse: it occurs when one object in the night sky makes another
object less visible.
The moon moves through space into ways. The moon revolves
around Earth and also rotates on its own axis.
The moon rotates once on its axis in the same time that it takes to
revolve once around Earth. Thus, a day on the moon is the same
length as a month on earth. For this reason the same side of the
moon always faces Earth.
As the moon orbits Earth, the relative positions of the moon, earth,
and sun change. The changing relative positions of the moon,
earth, and sun, cause the phases of the moon.
As the moon revolves, what happens to the relative positions of the
moon earth and the sun? The angle between them changes.
How does the moon’s orbit affect which phase of the moon you
see? You see more or less of the sunlit side of the moon, therefore a
different phase, depending on the position of the moon in its orbit
of Earth.





Why can’t you see the far side of the moon from Earth? The
far side always faces away from Earth.
What do you see in the first quarter? Half of the lighted side
of the moon.
What is happening in the waning gibbous phase? You see
more than half of the lighted side of the moon. The amount
you can see from Earth decreases each day.
During which faces are the moon, earth and sun aligned?
A new moon and a full moon.
How can you tell whether the moon is waxing or waning?
Observe it over time to see if it gets larger or smaller. A
waxing moon gets larger, a waning moon gets smaller.
 Phases
of the moon:
 Look at figure 2 page 192
 As the moon revolves around the earth
the amount of the moon’s surface that is
lit remains the same. That part of the lit
surface that can be seen from Earth
changes.
What are Eclipses?



A solar eclipse happens when the moon
passes directly between Earth and the sun,
blocking sunlight from Earth. The Moon’s
shadow then hits Earth.
Which side of the moon receives the light of
the sun during a solar eclipse? The far side.
A solar eclipse lasts only a few minutes. Why?
Because Earth rotates and carries you out of
the moon’s shadow
Causes and effects of eclipses



What causes an eclipse? When an object in
space comes between the sun and the third
object, it casts a shadow on the third object.
Describe some events that occur when the
moon blocks out the sun: day becomes as
dark as night, the air cools, and the sky
becomes an eerie color.
What has to happen to the relative positions
of the sun the moon and Earth for an eclipse
to occur? They all have to line up so that the
moon blocks the sun from Earth or Earth
blocks the sun from the moon.




Umbra: Latin for shadow
Penumbra: Latin for almost shadow
Total solar eclipses: the very darkest part of the
moon’s shadow is the umbra. Within the umbra
the sun’s light is completely blocked. In the umbra
you experience a total solar eclipse.
Partial solar eclipses: the moon casts another part
of the shadow that is less dark than the umbra. This
larger part of the shadow is called the penumbra.
In the penumbra part of the sun is visible from
Earth. During a solar eclipse people in the
penumbra see only a partial eclipse.


A lunar eclipse happens at a full moon when Earth
is directly between the moon and the sun. During
a lunar eclipse, Earth blocks sunlight from reaching
the moon. Lunar eclipse happens only when there
is a full moon because the moon is closest to
Earth’s shadow at that time.
Why lunar eclipses last much longer than solar
eclipses? Earth is much larger than the moon so it’s
shadow is also larger. The moon may take several
hours to pass completely through the complete
shadow of Earth. By contrast during a solar eclipse
it passes in a matter of minutes.




Earth’s shadow has an umbra and a
penumbra.
During a lunar eclipse the umbra is the
darkest part of Earth’s shadow. The penumbra
is the larger, less dark part of Earth’s shadow.
When the moon is in Earth’s umbra you see
the total lunar eclipse..
When the moon passes partly into the umbra
of Earth’s shadow a partial lunar eclipse
happens.





The ends of Earth’s axis tilt toward or away from
the sun depending on the season
In what direction – the south end of Earth’s axis tilt
during winter in the northern hemisphere? Toward
the sun
What season is it in the southern hemisphere when
it is winter in the Northern Hemisphere? Summer
How would the positions of the moon and earth
be different in a lunar eclipse? Earth would be
between the sun and moon
What phase would the moon be in then? full
moon
 Classwork:
Model a solar and a lunar
eclipse. Illustrate the differences.