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Objectives Solar and Lunar Eclipses WebQuestModule 3: The Earth and the Moon Timeframe:  This activity requires approximately two class periods (~50 minutes)
Objectives:
Lesson Overview:
This activity involves two WebQuest Internet research components. Students will use the Internet links provided to research solar and lunar eclipses in an attempt to better understand the relationship between the sun, moon and Earth. Students will also be presented with fascinating eclipse pictures and a look at the astronomers who chase eclipses around the world. The last part of the lesson involves having students write a descriptive paragraph and a detailed diagram explaining how solar and lunar eclipses differ. Materials and Resources:
Vocabulary:
Background Information:
Solar and Lunar Eclipses Solar Eclipses:
Lunar Eclipse:
Watch
a Solar Eclipse animation During the Moon’s orbit around the Earth, it will occasionally pass through the Earth’s shadow, or will cast its shadow on the Earth. These events are known as lunar eclipses and solar eclipses, respectively. Lunar eclipses occur when the Moon passes through the Earth’s shadow. Because the Moon has to be on the opposite side of the sky from the Sun for this to occur, a lunar eclipse can only take place during the full moon phase. During a lunar eclipse, the Earth’s shadow will travel across the face of the Moon, appearing as though a bite has been taken from it. At total eclipse, the Moon will not darken completely but instead glow deep red because the Earth’s gravity will refract (bend) a small amount of light from the Sun onto the lunar surface. Because the Earth casts a relatively large shadow, lunar eclipses occur a couple of times a year and are visible to large regions on the Earth, lasting up to 100 minutes. Although the frequency of solar eclipses is not considerably different from that of lunar eclipses, they are rarely seen because they are visible only along an extremely narrow path of the Earth. During a solar eclipse, the Moon obstructs the Sun and casts its shadow on the Earth. However, because the Moon is relatively small, the shadow cast during totality never exceeds 270 kilometres in width. If the observer is located in only a portion of the shadow (the penumbra), they would observe a partial solar eclipse where the Moon would only partially cover the Sun. Despite being partially obscured, the Sun is still so bright it would appear no different to the unaided eye (never look directly at the Sun, even during a solar eclipse). It is not until the observer is located within the central region of the Moon’s shadow (the umbra) that the Sun becomes completely covered. Totality of a solar eclipse lasts at most about seven and a half minutes, at which time only the Sun’s corona is visible and several stars will be visible in the daytime sky. Because a solar eclipse can only occur when the Sun and Moon are in the same region of the sky, it can only take place during the new moon phase. In addition to the partial and total eclipses, there is a third type of solar eclipse called the annular eclipse. The annular eclipse can only occur when the Moon is near apogee (its furthest distance from the Earth). At this time, the Moon appears fractionally smaller in size than usual and is therefore not large enough to fully cover the Sun. During an annular eclipse, the observer would see a bright golden arc or a full ring of light around the darkened Moon. Phases of the Moon
By observing the Moon over a period of several weeks, one will notice that the Moon rises and sets at different times each night, and that there is a regular progression through lunar phases. In a synodic month, the Moon progresses through one lunar cycle and will vary between being a completely dark new moon and a fully illuminated full moon . The lunar phases are caused because the orbit of the Moon around the Earth will vary the Moon’s position in relation to the Sun. Half of the Moon is always lit by the Sun, but the portion that we see will change depending on where the Moon is in its orbit. The synodic month “begins” at new moon. Because the Moon is in the same part of the sky as the Sun, the illuminated half of the Moon is not facing us and is not visible. During new moon, the Moon rises and sets at the same time as the Sun, and is therefore in the sky during the day. There is then a progression through the growing crescent phase until we see the right half illuminated; this is known as a first quarter moon. After the first quarter phase, there is another progression, this time through the waxing gibbous phases. The Moon becomes full about 15 days after new moon. During a full moon, the Moon is opposite the Sun and is fully lit. The Moon rises at sunset and sets at sunrise when it is full, so the Moon is always visible in the night sky while full. The Moon then begins to wane through another gibbous phase until it reaches its next phase called last or third quarter moon, and again proceeds through another crescent phase, ultimately returning to the new moon almost 30 days later. The saying “Once in a blue moon” is a referral to when two full moons occur in the same calendar month. Developing the Lesson:
Anticipatory Set
Introduction
Hands-on Activity
Check for Understanding
Independent Practice
Closure:
As a closure to the activities, the teacher uses the applet in a lecture-style delivery format, stopping the animation at key moments and eliciting feedback from the students as to an explanation for the type of eclipse observers on Earth would see.
Extension: Upon completing this lesson, teachers may wish to review the Phases of the Moon lesson. Evaluation:
Teacher Reflections:
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