PURPOSE: To produce teaching materials where positions of the sun and the moon are changed to grasp the relation among the age of the moon, the position of the sun, and the state of tide on the model on which the state of tide is detected on a basis of the age of the moon and the position of the sun.

CONSTITUTION: Disc-shaped members (a), (b), (c), (d), and (e) shown in figure are layered to form a model A. The upper part of a shaft (n) and the member (a) are fixed. An upper face (m) of the member (d) and the bottom part of the member (b) are fixed also. The member (a) consists of transparent materials, and a line (g) indicating the direction of the sun is written on the member (a), and ages of the moon are written on the circumferential face. In respect to the member (b), only an elliptic part (h) is transparent, and the circumferential part and a part (j) indicating the section of the earth are not transparent. A line (i) indicating the direction of the moon is written on the member (b), and a part (k) of the member (c) is colored to indicate the section of the sea. Members (b), (c), and (d) are rotated, and the line (g) and the line (i) coincide with each other to indicate the spring tide and cross at right angles to indicate the neap tide. The age of the moon in the day is obtained and is coincident with the line (i) to determine positions of the sun and the moon, and the model is rotated at every 15° in one hour on the table where place names of the world are written on the circumference, thus detecting the state of tide in each place.