The Moon and Its Changing Shapes - First Grade Science

When dusk settles into evening, the night sky is often illuminated by the silvery glow of the moon. The moon is Earth's closest cosmic neighbor and our only natural satellite. A satellite is any celestial object that orbits around a larger planet. For thousands of years, people have looked up at the moon in awe, wondering why it seems to change shape from a slender sliver to a brilliant glowing circle and back again. By studying the moon, you discover that its changing shapes are part of a predictable monthly lunar cycle.

What is the Moon?

Unlike the sun, which is a fiery star generating its own light and heat, the moon is a cold, rocky sphere.

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|                          FACTS ABOUT OUR MOON                         |
|                                                                       |
|   CLASSIFICATION    Earth's natural satellite.                        |
|   SURFACE TYPE      Dry, rocky, dusty, covered with impact craters.   |
|   ATMOSPHERE        No atmosphere, no wind, no weather, no rain!      |
|   WATER & AIR       No liquid water, no air to breathe.               |
|   GRAVITY           1/6th of Earth's gravity (you could jump 6x high!)|
|   LIGHT SOURCE      Reflects sunlight like a giant dusty mirror!      |
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The Moon Does Not Make Its Own Light!

One of the most surprising facts in astronomy is that the moon does not produce any light of its own! When you see the moon shining in the night sky, you are actually seeing sunlight bouncing off the moon's light gray, rocky surface, reflecting back to your eyes on Earth just like a mirror.

Craters and Maria

The surface of the moon is covered with round bowl-shaped dents called craters. Because the moon has no protective atmosphere, space rocks called meteoroids have crashed into its surface for billions of years without burning up. The smooth dark gray patches on the moon are ancient plains of solidified volcanic lava called maria (the Latin word for "seas").

Why Does the Moon Seem to Change Shape?

The moon does not physically change its shape or shrink in size; it is always a round, rocky sphere! The apparent changes in its shape are called moon phases (lunar phases).

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|                         THE 8 PHASES OF THE MOON                      |
|                                                                       |
|   1. NEW MOON          Moon is between Earth & Sun; dark side faces us|
|   2. WAXING CRESCENT   Slender sliver of light grows on the right.    |
|   3. FIRST QUARTER     Half of the moon's face is lit up on the right.|
|   4. WAXING GIBBOUS    More than half is illuminated and growing.     |
|   5. FULL MOON         Whole lit side faces Earth; glowing circle!    |
|   6. WANING GIBBOUS    Lit portion begins shrinking on the right.     |
|   7. THIRD QUARTER     Half of the moon is lit on the left side.      |
|   8. WANING CRESCENT   Thin crescent sliver before returning to New.  |
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|                        VISUALIZING MOON PHASES                        |
|                                                                       |
|      (   )            ) )            ( | )           ( o )            |
|     NEW MOON        CRESCENT     FIRST QUARTER     FULL MOON          |
|    (Dark Face)   (Thin Sliver)    (Half Circle)  (Complete Circle)    |
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The Lunar Month

As the moon orbits around the Earth once every 29.5 days (about one month), our viewing angle changes. Half of the moon is always lit up by the sun, and half is in shadow. The phases simply show how much of that illuminated half we can see from our vantage point on Earth! Waxing means the lit part is growing larger each night (New Moon to Full Moon). Waning means the lit part is shrinking smaller each night (Full Moon to New Moon).

Humans on the Moon: The Apollo Missions

The moon is the only place in outer space where human beings have ever set foot! In July 1969, astronauts Neil Armstrong and Buzz Aldrin landed their spacecraft, Apollo 11, on the lunar surface. Because there is no wind or rain on the moon to blow dust away, the footprints those brave astronauts pressed into the lunar dust remain there to this day, preserved like footprints in fresh plaster!

Chapter Review Exercises

Question 1: What is a natural satellite, and what is Earth's natural satellite?

Question 2: Does the moon produce its own light? Explain where the moon's light comes from.

Question 3: Why does the moon appear to change shape throughout the month?

Question 4: What is the difference between a "waxing" moon and a "waning" moon?

Solutions and Explanations

Solution 1: A natural satellite is any celestial body that orbits around a larger planet. The moon is Earth's natural satellite.

Solution 2: No, the moon does not produce its own light. The moonlight we see is sunlight reflecting off the gray rocky surface of the moon back toward Earth.

Solution 3: The moon appears to change shape because as it orbits around Earth, we see different amounts of its sunlit half. The moon is always half-illuminated by the sun, but our viewing angle from Earth changes continuously over its monthly orbit.

Solution 4: A waxing moon is when the sunlit portion we see from Earth is growing larger each night (progressing toward a Full Moon), while a waning moon is when the sunlit portion is shrinking smaller each night (progressing toward a New Moon).