Three-ball instrument, also known as the lunar ground operator, is a tool for the teaching and popularization of astronomy. It consists of three balls representing the sun, the earth and the moon, and has a mechanical linkage to demonstrate the relationship between the three balls, resulting in some astronomical phenomena.

Introduction

      To mimic what is true in nature, the sun in the middle of the tribulometer usually uses luminous bulbs to illuminate the earth and the moon. The Earth's orbit around the Sun rotates obliquely, and the Moon's orbit around the Earth intersects the Earth's orbit around the Sun at an angle. In this way, we can demonstrate solar and lunar eclipses, the profit and loss of the moon, the rotation and revolution of the earth, and the alternation of day, night and seasons.

Three-ball instrumentself-made method

      1. The sun is composed of a 100-watt bulb with a Milky White circular cover mounted on the top of the left pillar.

      2. The globe is made of ping-pong ball, with a small wire slanting through the axis, with a half ring iron support fixed on the right axis.

      3. Pulley: A larger pulley is fixed on the axis of the solar column 5cm under the assumed sun; under the vertical axis supporting the earth, a small pulley that can rotate around the axis is installed. The ratio of the diameters of the two pulleys is 12:1.

      4. Moon: Take a small ball of the right size with a hole in the middle, wear it on the wire, and then install it on the small skin under the globe. The edge of the pulley is flush with the middle of the earth, and can follow The rotation of the small pulley rotates around the earth.

      5. Tray. A support plate that can rotate around the shaft is installed on the shaft under the large pulley, and the length of the support plate is about 50-60cm. It has a hole at the right end of the, fix the shaft of the small pulley in the hole, hang the belt with the appropriate tightness, and push the support plate to support it, the plate drives the earth to rotate around the sun, and the small pulley drives the moon to rotate around the earth.

The use method of three ball instrument

      Demonstrations need to be performed in a shaded room. By continuously pushing the tray by hand, the earth revolves around the sun and the moon revolves around the earth, which can see the full moon and the lack of the moon, when the earth moves between the sun and the moon, the formation of the lunar eclipse; when the moon moves between the sun and the earth, the formation of the solar eclipse.