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.. shadow a partial lunar eclipse happens.  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.