The sun's paths in different seasons, demonstrated by the Planetarium star projector
For Grade 3
To arrange a visit for your school group, please call (585) 697-1942 at least three weeks in advance.
Developed in consultation with third-grade teachers and students, this program takes advantage of the Planetarium's unique capabilities to show changes in the sky.
Review the concept of cycles and generalize it to the cycles of the day, year and lunar month, all caused by rotation and revolution. Compare and contrast the sun's paths in the skies of summer, fall, winter and spring. Observe the sun's daily path from sunrise to midday in each season. Measure the height of the midday sun by pointing to it. Predict the direction of sunset in each season. Step through the order and sequence of the phases of the moon. Finally, tour the night sky, observing and classifying currently visible planets and constellations.
NYS Learning Standards: ELA1; MST3, MST4PS(1); MST6(1,2)
Click here to download a transcript of a typical presentation (59k pdf)
Outline of the Program
What is a cycle?
You already know the word cycle from the word bicycle (two wheels). A cycle is a series of events that occurs in the same way, over and over, just as a spinning wheel returns over and over again to its starting position. Students may already know other examples of cycles, such as the life cycle of a butterfly or frog, or Earth's water cycle.
The cycle of the day
The cycle of the day is caused by the rotation of the Earth on its axis. When our part of Earth is turned toward the sun, we have daytime; when our part of Earth is turned away from the sun, we have night. A complete cycle of day and night takes 24 hours. From our perspective on Earth's surface, the Earth's rotation makes the sun appear to rise, travel across the sky, and set. At night, Earth's rotation makes stars appear to rise, travel across the sky, and set.
The cycle of the year
The year is caused by Earth's revolution about the Sun. Seasons are caused by the tilt of Earth's axis (a hard point to visualize at third grade, or even later!) From our perspective, Earth's revolution plus the tilt of its axis causes the sun's daily path through our sky to change with the seasons:
The sun rises south of east.
The sun travels in a low path across the sky.
The sun sets south of west.
On the first day of winter (the winter solstice), the sun is in Rochester's sky for only about 9 hours.
On the first day of spring (the vernal equinox):
The sun rises exactly east.
The sun travels in a medium-high path across our sky.
The sun sets exactly west about 12 hours later.
The sun rises north of east.
The sun travels in a high path across our sky.
The sun sets north of west.
On the first day of summer (the summer solstice), the sun is in Rochester's sky for more than 15 hours.
On the first day of fall, or autumn (the autumnal equinox):
The sun does the same thing as on the first day of spring.
The cycle of the moon's phases: the lunar month
The moon revolves around the Earth about once a month. The same side of the moon always faces Earth. However, the Earth-facing side of the moon receives different amounts of sunlight at different times. The changing direction of sunlight on the moon causes its phases, which repeat in a cycle lasting about 29 1/2 days.
Phases of the moon
1. New moon (not visible; the only time solar eclipses can happen)
2. Waxing crescent
3. First quarter
4. Waxing gibbous ("gibbous" comes from a Latin word meaning a hill)
5. Full moon (always rises about the time of sunset )
6. Waning gibbous
7. Last quarter
8. Waning crescent
1. New moon (again, beginning a new cycle)
The phases of the moon are not caused by clouds or shadows. They are caused by the changing direction of sunlight striking the side of the moon that faces us.
Further Information Outside RMSC
Animation of the Moon's Phases
This short video, produced at Strasenburgh Planetarium and posted on YouTube, shows the cycle of the moon's phases from an outer-space point of view and from Earth's point of view. In the world of education books and videos there are many confused "explanations" that make the enjoyable activity of moon watching into a baffling nightmare! We want this video to help dispel the confusion.
Moon phases past and future
Do you need to track the phases of the moon? If the sky is cloudy, or if you're in a hurry, you can get an accurate picture of the moon's phase for any date from January 1, 1800 through December 31, 2199 from the U.S. Naval Observatory's Virtual Reality Moon Phase web page— http://tycho.usno.navy.mil/vphase.html.
Note: when you enter a time, you'll need to use 24-hour (military) time. That is, 4pm will be 16 hours; 8pm will be 20 hours, and so on.