Three ball instrument is a vivid portrayal of visual teaching instrument between day, month relative motion, the relative position of the utility model can simulate the day, three months in space, and the image that the running state of the earth, the moon, the scientific explanation of various natural phenomena arising therefrom. Therefore, it is an indispensable auxiliary teaching tool to overcome the abstract teaching, deepen the students to master the law of celestial motion change

The Sun : it is a red plastic with a light bulb, which is the center of the center of the earth and other high. the earth can observe the seven continents, four oceans, tropic, south of the Arctic Circle, the equator and the international date line etc. 

The moon : the height of the center and the center of the earth. The instrument of the day, the earth, the size of the moon can not be made according to the actual proportion, so the ecliptic plane angle appropriate amplification.

1.The earth's rotation and revolution 

2.The moon's revolution(day and night twilight in the same place at the same time every day and night twilight.

3. Because the earth always leaned over the revolution and rotation, the northern hemisphere winter day short night long, summer nights are short. In contrast to the southern hemisphere. 

4. Four seasons and cold climate changes in the moon. 

5. Solar eclipse and lunar eclipse. 

6. Twenty-four solar terms