Universe Cycle - Earth (3)
Pre Lab 

   
OBJECTIVES:
  • Exploring eclipses.
  • Comparing lunar and solar eclipses.
VOCABULARY:
  • lunar eclipse
  • solar eclipse
MATERIALS:

Students learn about lunar and solar eclipses.


Solar eclipse

BACKGROUND:

A solar eclipse takes place when the Moon comes between the Sun and Earth. The Moon thus casts a shadow on the "daytime" part of the Earth. Because the Moon is small compared to the Earth, only a limited portion of the Earth experiences the eclipse. Viewed from Earth, the Moon appears to move in front of the Sun for a period of minutes to hours. It becomes as dark as night if the Sun is fully blocked, or partially dark if the eclipse is incomplete.

When the Earth is between the Sun and the Moon, a lunar eclipse can occur. The Earth blocks off the sunlight from the Moon. This may cast the Moon into total darkness, or if the eclipse is partial, the Moon may glow a dark red color.

When the Moon is not aligned with the Sun and Earth, only part of it is visible. The Moon revolves counterclockwise around the Earth. From the time of a new Moon, when no portion of it is visible, the Moon increases in size. The right side of the Moon becomes visible first. The Moon grows to its full size, and then shrinks. Shadows also progress across the Moon from right to left.

PROCEDURE:

  1. The book, Eclipse: Darkness in Daytime describes how scientists predict when an eclipse will take place and where the Moon's shadow will fall. Read Eclipse: Darkness in Daytime to the class. Make sure the students understand what an eclipse is. Explain how the appearance of the Moon changes as it rotates around the Earth. It may help to draw diagrams on the board.
     
  2. Set up the planetarium as shown in the diagrams below. Ask the students the questions that follow, and have them answer them out loud. The answers are given below in parentheses.

General questions: (1) Ask the students how many planets are shown on the model. (2) Have the students name them. (Venus, Earth) (3) Which inner planets are missing? (Mercury and Mars). (4) Which planet on this model receives the most heat from the Sun? (5) (Venus is the closest on this model.)

Diagram A: Are there any areas of the Earth and Moon that are not receiving sunlight? What is it called when this happens? (Yes, part of the Earth is in shadow. This is called a solar eclipse).

Diagram B: Are there any areas of the Earth and Moon that are not receiving any sunlight? What is it called when this happens? (Yes, this time part of the Moon is in shadow. This is called a lunar eclipse).

Diagram C: How much of the Moon is visible from Earth? (Half) Make sure the students see that the right half of the Moon is visible.

Diagram D: How much of the Moon is visible from Earth? Is it the same part of the Moon as in the last question? (Half of the Moon is visible again. No, the left half of the Moon can be seen this time.)
  

  1. For more information on past and future eclipses, visit :

    http://sunearth.gsfc.nasa.gov/eclipse/OH/OH2002.html
    This is a NASA website with links to solar and lunar eclipse information, including maps, up to 3 years into the future.

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