Three-ball instrumentFor teaching the earth, the moon's revolution and rotation, day and night changes, seasonal changes, the causes of solar eclipses and lunar eclipses, changes in the phases of the moon.

Three-sphere instrument structure: the sun is replaced by a bulb, the center height is equal to the center height of the earth, the earth is north and south, the middle red line is the equator, the equator is on both sides of the equator is the Tropic of Cancer, and the upper and lower circles are the north and south poles. The average height at the center of the Moon is equal to the height at the center of the Earth.

      Three-ball instrument: The inclination angle of the earth's axis is 23.5, which is always inclined in one direction when rotating around the sun. The solar term disk indicates the four seasons of spring, summer, autumn and autumn. Arrows indicate the seasons and lunar seasons when rotating around the sun. The moon phase disk is used to indicate the position of the moon phase. When the moon revolves around the earth, its orbit is inclined by 5.09 degrees. Since it cannot be proportioned, it is changed to about 25 degrees, and the direction is from west to east.

The relative motion of the earth, the moon and the sun, pushing the handle can be seen that the earth takes the moon to revolve around the sun in a counterclockwise direction, the earth revolves around the axis of the earth when it revolves around the sun, the moon revolves around the earth in a counterclockwise direction, the earth revolves around the sun for one week, the moon revolves around the earth for twelve weeks, and the earth rotates for 365 weeks.

Note: When using the three-ball meter, use light force and turn it counterclockwise.