1. Unit 2 Lesson 3
What Are Moon Phases?

2. Learning Goals
I will be able to identify and draw the phases of the moon.

3. Our Moon: Earth’s Satellite
The moon is Earth’s satellite.
A satellite is any object that revolves around another larger object in space.

4. Our Moon: Earth’s Satellite
The moon revolves around the Earth, but it also rotates on an axis just like Earth does, to have its own day and night times.
Days on the moon: 250 degrees
Night on the moon: 250 degrees BELOW ZERO

5. Our Moon: Earth’s Satellite
An interesting fact: the moon revolves around the earth at the same exact speed that it is rotating.
This is why we can only see one side of the moon from Earth.

6. Our Moon: Earth’s Satellite
It takes the moon about a month to make one revolution around the earth.
At this time, the process starts over again.
This is similar to when Earth makes a full revolution around the sun (365 days) – a new year starts.

7. Our Moon: Earth’s Satellite
As Earth revolves around the Sun, the moon constantly revolves around the Earth.
It takes about a month for the moon to get around the Earth one time.
Earth
Sun
The red spot indicates where the moon would be in about 28 days as it revolves around the Earth.

8. Our Moon: Earth’s Satellite
The moon looks very different from Earth:
No air
No liquid water
Rocky Surface
Lots of craters
Having mountains is the only similarity to Earth.

9. Our Moon The moon is the largest, brightest object in the night sky.
Although it appears to be shining, it is actually just reflecting light from the sun back to Earth.
Even if you see the moon during daylight hours, this is because the moon is reflecting light back from the sun.

10. Our Moon
The moon is much smaller than Earth, which is much smaller than the sun. The moon is only about ¼ the size of the Earth.
Think of a soccer ball, baseball, and golf ball to picture the size relationships of the Sun, Earth, and moon!

11. Moon Phases
The changes in the appearance of the moon’s shape are known as phases.
It takes about a month for the moon to complete all of its phases.

12. Moon Phases
The “phases” we see are just the lighted part of the moon that faces the Earth.
The amount of light we see changes every week.
Each week, more of the moon lights up until it eventually reaches a full moon. Then, we start seeing less light from the moon.

13. Moon Phases
New Moon Phase (you cannot see the moon during this time)

14. Moon Phases
Notice how after new moon, we start seeing more light reflected. This is called waxing.

15. Moon Phases
When the moon has “waxed” about half way across, we have the First Quarter Phase.

16. Moon Phases
The moon will keep “waxing” until we have the full moon phase.

17. Moon Phases
After the full moon, “waning” begins. This means we start seeing less light reflected from the moon.

18. Moon Phases
When about half the moon has “waned” about half way, we have the Last Quarter Phase.

19. Moon Phases
We will continue to see less light reflected from the moon during waning.

20. Moon Phases
The last bit of “waning” happens, meaning we get back to new moon phase and the process starts over again.

21. Moon Phases
Video Clip

22. Lunar and Solar Calendars
People use the phases of the moon and Earth’s orbit around the sun to make calendars and to track time.
Our modern calendar is based on Earth’s orbit around the sun and the moon’s phases.
Calendars based on Earth’s orbit are called solar calendars.

23. The Chinese Zodiac Calendar
The Chinese zodiac calendar is based in part on the phases of the moon.
Since their calendar is based on the moon, it’s a lunar calendar.
Cycles of time on the Chinese calendar are names after animals.

24. Solar vs. Lunar Calendar
Solar Calendar
First Month
Second Month
Lunar Calendar
First Month
Second Month
What conclusion can you draw about lunar months compared to solar months based on the graphic above?

25. Review song! Click on the full moon!