Elementary Planetarium
The Elementary® planetarium (orreries) is a perfect beginning model to illustrate individual concepts, one at a time. In this model, the Earth and moon are moved separately, by hand. The ladder-chain-and-gear drive keep the axis of the Earth pointed at a 23- 1/2° angle, toward the North Star. An instruction book, Elementary Planetariums, is included. Height: 12” Arm length Among the many basic concepts and phenomena that can be demonstrated with this model are:
• The reason for the occurrence of night and day
• The variation in the length of daylight
• The movement of the Earth around the sun from west to east
• Why only one side of the moon is seen from the Earth
• How eclipses of the sun and moon occur
• Cause of the phases of the moon