Phases, Eclipses, and Tides

Activating Prior Knowledge

Describe the different ways you have seen the moon. (write down some of the terms)

Discover: How does the Moon Move?

Items used: Two coins or option with a globe

Key points: Point of View

From the earth does the moon rotate? No we always see the face of the moon

From the point of View of the moon, does it rotate? No we always face the earth

For this reason no one from the earth has ever seen the back of the moon

Assign Reading
 

Go over "Guide for Reading" and "Reading Strategies" p24 K

Reading Assignment: Section 1-2

Objectives: The student will be able to…

• Explain what causes the phases of the moon
• Compare the causes of solar and lunar eclipses
• Explain what causes the tides

• The moon is the Earth’s closest neighbor in space, so it makes sense that it has been closely observes and studied since the earliest times.
• Even though it is very close compared to all the other objects in space, it is still about 384,400 kilometers from earth.
• The moon moves just like Earth , it revolves around the earth and rotates on it’s axis
• As the positions of the moon, earth, and sun change, lunar phases, eclipses and tides occur.


Motions of the Moon (p. 24 J)
 

• Revolution of the moon. How long does it take the earth to revolve around the sun? 365.25 days. The moon revolves around the Earth in 27.3 Days.
• 27.3 Days is the moons sidereal period or the time it takes for it to return to the same position compared to the stars.
• Remember that it takes 29.5 days to make it's synotic period or the time it takes to go through all of the phases.
• This period of time, one revolution (29.5 days) of the moon was called a month or moonth.. So the months of the year were once based on the revolution of the moon. The moon then was once used to determine the calendar year.
• Orbit: the orbit of the moon or the path that it takes through the sky is a slight oval shape.
• Rotation: As we saw in the discover problem the moon also rotates, very slowly. How long does it take to make one rotation? 27.3 days.
• Because of this we only see on side of the moon. It is gravitationally locked in place and even bulges out slightly to the earth side.

• On a clear night with a full moon the sky may seem lit up by the moon.
• How do we see the moon? The light from the sun hits the moon and bounces off to our eye.
• What is the shaded part of the moon? The side of the moon opposite the sun, so that no light gets there.
• The moon itself is a dark gray almost the color of old asphalt.
• Because of the light of a full moon some events or celebrations were held during full moons.
• At Autumnal Equinox in September the full moon is called the Harvest Moon, because it is bright enough to continue harvesting at night.
• A month later in October, it is called the Hunter’s moon, because it is bright enough to hunt at night and get the final game preparations for winter.

• Phases of the moon are caused by the relative locations of the Moon, Earth and sun.
• The earth and the moon are always ½ way lit by the sun
• The phases of the moon are cause by the amount of the sunlit moon that we can see from our position on the earth.

• Draw the diagram on the board and discuss the terms and positions

• Set up the class with the sun at one end of the room.
• Have the students in the middle as the earth
• Revolve around the earth, with the moon start with the new moon and go through each phase
• Now show the class why we see the moon as we do
• "What does waning mean?" The moon will get dimmer each night and the right side is lit up.
• "What does Waxing mean?" The moon will get brighter each night and the left side is lit up
• "What does Gibbous mean? More than half way lit up.
• "What does crescent mean? Less then half way lit up.

• "What is an Eclipse? An eclipse occurs when one object moves through the shadow of another.
• There are two types of eclipses that we commonly see from earth. A lunar eclipse when the shadow of the earth crosses the moon and a solar eclipse when a shadow from the moon crosses the earth.

• Solar Eclipses: are the most dramatic. If you are in the shadow of the moon during a solar Eclipse the air gets colder, the wind picks up and the sky turns dark.
• Draw positions of the sun moon and earth. What occurs is the moon passes between the earth and the sun and the shadow of the moon covers the earth.
• Total Solar Eclipse The full shadow is called the Umbra and that is where the sun is completely blocked by the moon. Figure 7
• Partial Solar Eclipse: A partial shadow where you see part of the Sun covered is called the Penumbra
• NOTE: Our moon just by chance is the perfect size and distance from earth, to completely block out the sun. Other planets do not. The sun is either much larger or smaller.
• Eclipses to many cultures were thought to be a bad omen meaning that something bad was going to occur, like war or a plague
• How often Does the moon pass between the sun and the earth? Once a month
• Why don’t we have an eclipse every month? Because the moon travels above and below the plane of the solar system, by about 5 degrees.
• The result is that some times the moon’s shadow passes above the earth and sometimes below the earth.
• Why is it rare? Because the Moon’s shadow is so small only a few hundred miles that it rarely passes over the same place so that we can see it.
• During what phase of the moon does a solar eclipse occur? New moon.
• Why does a lunar eclipse usually proceed a solar eclipse by about two weeks. Because it normally occurs during a full moon which is 2 weeks before a new moon.

• Lunar eclipses occur when the moon passes through the Earth’s shadow.
• Draw the positions of the Earth Sun and Moon.
• This can only occur then during a full moon.
• Total Lunar eclipse is where the moon passes through the earth’s umbra
• Since the earth’s shadow is so large compare to the moon it can be see from almost any where on the night-time side of the earth.
• Partial Solar Eclipse: is when the moon passes through the earth’s penumbra or partial shadow. In this case you only observe part of the moon being shaded. This may take two –3 hours.

Follow directions but use an overhead and moon ball to do it.

Work in pairs.

Tides:

• "What causes tides?" tides are caused by the pull of gravity
• The moon is held in orbit around the earth by the pull of gravity, but the moon also has gravity and it pulls back at the earth.
• The moon pulls the most on the sides of the earth that it is closest too.
• High Tides; occur when water is pulled towards the moon. The side of the earth facing the moon also has a large bulge of water pull towards it.
• On the side opposite the moon there is also a high tide. This is because the earth is pulled more than the water leaving the water behind.

• Spring tides. During a full moon the earth and sun and moon line up the pull of all three cause higher than normal tides
• Neap tides: when the moon and sun are 90" to earth causing lower than normal tides.

Biological Clocks. People and animals have their own clocks or rhythms that have some control on our waking sleeping and activity. If the cycle is based on the solar day it is called a circadian rhythm. If it is based on a lunar day 24.8 hours it is a lunar rhythm.

People think it may effect moods and many subtle effects in us.

Local Tides:

• Tides can be effected by the local terrain.
• Some are much more dramatic especially in areas with shallow bays or inlets that may become completely dry during low tides.
• Boats and ships may be stuck and have to wait for high tides.
• Some ships save energy by leaving with the tide, or come into harbor with the tide. So that the currents move them along.
• Sea animals must be well adapted to these changing conditions such as suction cups to prevent being swept away, or hard shells to protect them from predators or to prevent them form drying out.

Assignment:

Complete review and enrich worksheet.