How do sundials show the time, months, and seasons?

The sundial has a number of scales on the face of the sundial, and by watching the shadow of the sundial needle fall on the exact location of the scale on the face of the sundial, you can read the season, month and time. From the "table" to the sundial, there is a gradual transition process. "Table" if the ground with the appropriate scale division, it can become a horizon sundial. However, the scale of the horizonal sundial needs to use the knowledge of projective geometry - which is exactly what was lacking in ancient China. And equatorial sundials, although the installation is more complex, but in the scale is relatively simple. Therefore, it is natural that equatorial sundials were popular in ancient China.

Materials and tools:

Corrugated cardboard box, disk, ruler, scissors, pen.

Making Methods:

1. Spread out a corrugated cardboard box, draw the outline along the disk and cut it out.?

2. Use a straightedge to find the midpoint of the circle and mark it into four equal parts. Place the straightedge at 3 o'clock and 6 o'clock and divide the quarter into three equal parts, then mark the 4 o'clock and 5 o'clock. And so on, mark the position of all 12 points, which is the sundial surface. ?

3, another cardboard cut a right-angled triangle, it is a right-angled side of the dial from the center to the distance of each number, another right-angled side of the length of the longest side of the longest side of the half, which is the sundial needle. Paste the sundial pin on the dial, the end of the pointer points to Ⅶ.?

4, then, let's make the pillar. Draw the shape of the pillar on the cardboard box and cut it out. Be careful to draw both sides symmetrically. Two such pillars need to be made.?

5, one pillar from the top to the center cut a notch, while the other from the bottom to the center cut a notch. The thickness of the cutout is the same as the thickness of the cardboard. Stick the two struts together and a stable stand is ready.?

6. Glue the sundial to the strut and place the sundial in a sunny garden. The shadow on the sundial will tell you what time it is.

Expanded Information

Sundial, the original meaning is the shadow of the sun. The modern "sundial" refers to the ancient human use of the sun's shadow to measure the moment of a time instrument, also known as "sundial". The principle is to use the sun's projection direction to determine and divide the moment, usually by the sundial needle (table) and sundial surface (with scale table base). The use of sundial timekeeping method is a major invention of mankind in the field of astronomical timekeeping, this invention has been used by mankind for thousands of years.

References:

Baidu Encyclopedia Sundials Article