1. The Sun-Earth-Moon System
Grade 6
Image Credit: wordpress.com

2. Content Topics Associate cycles in the sky with time
Describe why Earth has seasons
Determine the phase of the moon
Compare and contrast all types of eclipses

3. What are the motions of the Earth, Moon, and Sun?
The apparent motion in the sky is due to the motions of the Earth and Moon.
Image Credit: Ashish Meshram

4. Some Vocabulary
Revolution is the action by a celestial body of going round in an orbit or elliptical course.
The Moon revolves around the Earth
Rotate is to turn around in a circle; to spin.
The Earth rotates on its axis once each day.

5. From a Million Miles Away, NASA Camera Shows Moon Crossing Face of Earth

6. Practice How many rotations does Earth complete in one revolution?
Do you think the Sun rotates and/or revolves?
The Sun rotates an average of once every 25 Earth days.
The Sun revolves once every 250 million years.

7. What are the cycles that determine time keeping?
Many early calendars were based on the cycles of Moon phases.
We currently use the Gregorian calendar (1582), based on the cycle of Earth’s revolution around the Sun.
Leap years must be divisible by 4
Leap years exclude years divisible by 100

8. Solar Year Time taken to make one revolution around the Sun
Time it takes Earth to complete a full orbit
Time it takes the Sun to return to the same position in the cycle of seasons, as seen from Earth

9. Animation of a Year

10. Slideplayer.com

11. Month The month is based on the motion of the Moon.
Unit of time based on the revolution of the Moon around the Earth (27.3 days) and defined as the period between two successive new moons or, on average, days.

12. Image Credit: wordpress.com

13. Practice
Why does the moon phase cycle take longer than the moon orbit cycle?
The Earth is traveling in its orbit while the Moon orbits the Earth.
The Moon completes its orbit in 27.3 days. What is the change in position of the moon (number of degrees) in the sky, each day?
360 degrees = degrees per day
27.3 days

14. Solar Day The day is based on the rotation of the Earth.
The solar day is defined as the time it takes for the Sun to return to its culmination point (its highest point in the sky).
Time for two successive crossings of the Meridian by our Sun.

15. Your Meridian
Image Credit: astronomy.ohio-state.edu

16. Practice How many months are there in a year?
How many hours are there in a day?
24 hours

17. What causes Earth to have Seasons?
The changing distance between the Earth and the Sun is not the cause of the seasons.
Our distance from the Sun only varies by 2-3%
NASA Image

18. Tilted Earth
23.5° Tilt

19. Image Credit: lumenlearning.com
Angled Sunlight
The more direct sunlight a hemisphere receives, the more it is heated.
Direct Sunlight
Indirect Sunlight
Image Credit: lumenlearning.com

20. lumenlearning.com

21. Seasons and Sun Path
Image Credit: pinterest

22. Practice
Why is the number of daylight hours on the first day of fall and spring the same?
The Sun’s position in the sky is the same on the first day of fall and spring.
How can we know when it has been a year? Is there more than one way to tell?
When it is Christmas
When it is summer break
When we have had all of the seasons

23. Why do we see different shapes of the Moon?
As the amount of reflected sunlight that we can see changes, we see the phases of the Moon.
Image Credit: hyperphysics.com

25. Moon Phase Terminology
New Moon Phase – No illumination
Full Moon Phase – All illumination
1st and 3rd Quarter – Half
Gibbous – More than half
Crescent – Less than half
Waxing –Increasing
Waning – Decreasing
Image Credit: NASA

26. Practice
There is always half of the Moon’s sphere reflecting sunlight. (True or False)
True
Is the moon ever visible during the day?
Yes

27. More Practice
If the moon in the image has been increasing in size each night, what is the phase of the moon? Waxing Gibbous
Image Credit: NASA

28. When do eclipses occur?
Eclipses only occur when the Earth, Moon, and Sun all lie in the same plane (the ecliptic) and are in the same location of space at the same time.
Image Credit: Wikipedia.org

29. Practice How often is it possible for an eclipse to occur?
Every 6 months
How can the tiny moon and Earth block the huge sun? Relative distance
Image Credit: pinterest

30. Eclipse Terminology An eclipse is a shadow. Umbra: complete shadow
Penumbra: partial shadow
2017 Eclipse Umbra
Viewed from Space
(NASA)

31. Total Solar Eclipse
The umbra of the Moon's shadow touches Earth’s surface. Full disk of Sun is blocked. (Sun-Moon-Earth)
Image Credit: NASA

32. Path of Totality
The umbra from a total solar eclipse is at most 167 miles wide.
Image Credit:

33. Annular Solar Eclipse
The umbra does not reach Earth, anti-umbra touches Earth.
Sketch not to scale
Image Credit: NASA

34. Partial Solar Eclipse
The penumbra touches Earth, and part of Sun disk is blocked by Moon.
Image Credit: lumenlearning.com

35. Practice What is the phase of our Moon during a total solar eclipse?
New Moon
Sketch a model of a total solar eclipse that shows the umbra and penumbra.

36. Lunar Eclipses The umbra of Earth's shadow covers our Moon.
Image Credit: socratic.org

37. Partial Lunar Eclipse
Image Credit: lumenlearning.com

38. Refraction
The fully eclipsed Moon appears red because light is refracted in the Earth’s atmosphere.

39. Practice What is the phase of the Moon during a total lunar eclipse?
Full Moon
Why is the shadow dark before it is red during a total lunar eclipse?
The Earth must block most of the intense white light before the refracted red light can be seen.
Sketch a model of a total lunar eclipse that shows the umbra and penumbra.