Sundial is the most reliable, because they will never be fast or slow. That is why Egyptians, Chinese, Babylonians, Greeks, Indians, and Peruvian Incas probably built them. Want to try? The process of making sundial can be a remarkable lesson in mathematics and astronomy for your children. Simple equatorial sundial can be made from materials on hand. You can also place them in the garden or on the balcony. This watch is called equatorial because the plane of the dial is parallel to the plane of Earth's equator.
1. Determine the direction of the north by the most ancient and precise way. Fix the vertical rod (gnomon) on a horizontal surface. Note the position of the shadow of the gnomon for a couple of hours before the solar noon point and draw a circle with the center at the site of fixing a gnomon and a radius equal to the length of the shadow of it in the initial moment of observation.
2. Follow the shadow: it will decrease and depart from the drawn circle, but at some point, it will begin to grow and re-cross it. Fix the shadow’s touch by the second point and connect it with the first one. The resulting segment is bisected. The line passing through the center of the circle and the midpoint will give us the midday line. This line is the exact north-south direction.
3. Mark up the dial. It is very easy to do: divide the circle into 24 equal parts by 15 ° (24h x 15 ° = 360 °) and mark the hours.
4. Now it is time to make it. You will need thick cardboard, a piece of plywood, a thin plank (you can also use the foam). It is necessary to fix the gnomon and impose the dial on him perpendicularly to the surface.
5. The last thing you need to do is to orient the resulting construction. Create the following conditions: a) the dial line "6-18" should be placed horizontally; b) the line "12-24" must coincide with the direction north-south, which we have already found (please refer to 1); c) plane the clock dial to the north, so that the angle between the gnomon hours and the plane of the horizon was equal to the latitude of your location (for Moscow it is approximately 55,5 °). The sundial is ready!
It reflects the true solar time, and its readings coincide with your wristwatch, if you take the summer and standard time in our country into account. Unfortunately, the sundial cannot work in winter: the sun in our latitudes is too low on the horizon, and the gnomon will give shade.