Sundial

Surely you have ever seen a sundial and you don't quite know how to use it. It's a type of instrument created to measure the passage of time through the movement of the sun. The graphic representation of this type of clock is based on the shadow cast by a stylus, known as a style or gnomon. To understand how time passes throughout the day, this presentation is done on a board on which different marks are engraved. The shadow of the stylus is named after the sun and is collected on the surface, which is generally flat or cylindrical.

In this article, we're going to tell you all about the characteristics and history of the sundial.

History of the sundial

This type of clock is also known as a sundial. It wasn't the Greeks who first began exploring this subject, although they were usually the ones who invented this type of instrument. In this case, we find the Egyptians, who, back in the 15th century BC, had already begun dividing the night and day into equal parts. The division of day and night into equal parts began to be realized through the appearance of certain stars. This is how they were able to think and design different ways to know the passage of time.

The problem with this method is that it was not portable. Some studies show that the Egyptian pyramids were already oriented in a certain way to measure the passage of time. Furthermore, the obelisks designed during this period also fulfilled this idea of ​​solar measurement. Later, centuries later, in the Greek and Roman eras, there are numerous documents that reveal evidence of the manufacture of the sundial, as is evident in the astronomical clock and in the Prague astronomical clockTo learn more about these topics, you can read our article on the measurement of time and its global influence.

How it works

The sundial is primarily based on the shadow cast by the stylus on the surface. Since the sun changes orientation as the Earth rotates, the different times of day can be plotted on a surface, and the stylus will cast a shadow corresponding to the time of day.

Consider the apparent motion of the sun on any given day. The sun rises in the east, passes through the south at noon, and sets in the west. Noon is considered 12 noon. The sun's apparent motion during this entire period is a constant one. It disappears in the west and travels east again, but while it does so, it is nighttime for us. Thus, we see that the entire path of the sun has an angle of 360 degrees in about 24 hours. The speed at which it is moving steadily is 15 sexagesimal degrees per hour.

Once we know this, we must think that the sun makes the apparent movement by turning around the axis of the earth. If we want to know what time it is according to the movement of the sun, we must have a representation as faithful as possible to the rotational movement of the earth. The style of our sundial must match the tilt of the earth's axis. This means that the inclination that this style should have with respect to the vertical of the place where we are must be equal to the latitude in which we are located. In addition, you can delve deeper into the subject of and its relationship with the Greenwich Meridian.

How to make a sundial

Let's talk about the guidelines needed to make the simplest sundial possible. In this case, the sundial begins with placing the stylus in the direction of the Earth's axis. This is approximately we must place the style in the north-south direction. To ensure that this style is placed in the correct position, we must ensure the latitude of the place where we are. We can learn the latitude of the area where we live from a coordinate map.

Once we've placed the stylus, we've determined our latitude. Thanks to this latitude, we know the inclination at which we should place the stylus. Now we just need to draw a quadrant where the shadow is reflected and marks the hours of the day. On the quadrant or board, we'll place the type of sundial we want to build in one way or another. Here, we have to let our imagination run wild. Each type of sundial will have a different design according to our tastes. This process is similar to creating a analemma in terms of precision and the importance of orientation.

Types of sundial

Let's analyze the different types of sundials that exist. These types vary depending on the orientation of their dial. We have the following types:

• Equatorial sundials: These are those whose quadrant is placed on a plane parallel to the Earth's equator. Here, we have a well-defined inclination of the stylus, and it's quite easy to position this plane. We just need to know that they will have an inclination of 90 degrees to the horizontal.
• Horizontal sundials: These are clocks with a dial placed perpendicular to the vertical line of the location. They are easy to construct and interpret since the dial extends northward, and the dial will not be marked at all times of the day.
• Vertical sundials: They are a type of model in which the style is oriented in the north-south direction. The dial shows the hours of the day and the dial is vertical. Keep in mind that we can orient the quadrant to the north or south, to the east or west.
• Other types of sundial: There are other types of sundials that are less common but can be just as effective. Here we find the shepherd's clock, which is portable, vertical, and small. These clocks get their name because they were used by shepherds to know the time of day when they were taking their cattle to graze. Another type of sundial is the diptych clock. This clock stands out for its two dials, divided into one vertical and one horizontal. These two dials are connected by an axis. In this case, we find that the style is a thread that remains taut when we place both dials perpendicular. They normally require a compass to accurately mark the hours.

I hope that with this information you can learn more about the sundial and its characteristics.