SOLAR CALENDAR

Objective: SWBAT: MAKE A SOLAR CALENDAR

Introduction:

How many days are in a year? 365. How many degrees are in a circle? 360.
It is no accident that these numbers are very close. A year is the time it takes for the earth to make a complete orbit around the sun. Ancients tracked the sun throughout the year as it rose and set against the background of the stars. They calculated that it took 360 days for the sun to appear to make a complete circle with respect to the stars. Most ancient calendars were round. Today’s calendars are square and don’t show the relationship of the calendar to its origin. We are going to make a round calendar that will enable us to track our position as we move around the sun during this school year.

Time needed: two or three periods

Materials:

Protractor
Pencil & Paper

Procedure:

1. Make a dot in the middle of your paper.
2. Place the center mark of the protractor over the dot on the paper.
3. Mark the two zero points on either side.
4. Use the bottom edge of the protractor to draw a line that connects the two zero marks and the center.
5. Place the protractor so that it lines up with the center and zero marks.
6. Draw the hemisphere arc that connects the two zero points. Mark the 90 degree point.
7. Flip the protractor upside down.
8. Line up the center and the zero points.
9. Draw another hemisphere arc. Mark the 90 degree point.
10. Draw a line that connects the two 90 degree points and passes through the center.
11. Mark off every ten degrees between the zero marks and the 90 degree marks.
12. Label the equinoxes and the solstices:

September 23—Fall Equinox
December 22—Winter Solstice
March 20 – Spring Equinox
June 20 – Summer Solstice

13. Fill in the dates between the equinoxes and the solstices: One degree = one day. Start at the September Equinox. There are 360 degrees in a circle. There are 365 days in a year. (366 days in a leap year). That means that you will have to squeeze in more days at some point on the calendar. The best place to do this is around the June Solstice. ( We will find out why later in the year).14. Starting on the September solstice, make a blue circle on the calendar every ten days to show the position of the Earth with respect to the Sun.

Questions:
1. Approximately how many days are between:
The Fall Equinox and the Winter Solstice?
The Fall Equinox and the Spring Equinox?
The Winter Solstice and the Summer Solstice?

2. What percent of the year does each season represent?

3. Approximately what percent of its orbit around the Sun will Earth travel between the Fall Equinox and the Winter Vacation?

4. Approximately what percent of its orbit around the Sun will Earth travel between the Fall Equinox and the date you graduate?

5. Measure the angle of the arc that Earth will transcribe in its orbit between the Fall Equinox and your birthday. Approximately how many degrees does the angle have? Is the angle acute or obtuse?

6. Ask and answer a question about Earth’s orbit around the sun that can be answered by looking at the calendar.

Vocabulary: Define the following words.

Equinox; Solstice; circle; center; hemisphere; arc; angle; degree; day; acute angle; obtuse
angle; orbit; protractor

Standard 4 The Physical Setting.
Key Idea #1 The Earth and celestial phenomena can be described by principles of relative motion and perspective. P.S. 1.1e-I