Sundial - Astronomical Study and Observation

To read the Portuguese version (click here) and Spanish (click here)

What is Astronomy?

Astronomy is the study and observation of Celestial bodies, like stars, galaxies, etc ...

Considered one of the oldest sciences, identified their study in civilizations as Sumerian, Babylon, Egypt, China, Maya, and many others, which have methodical records of the movements of the sky. Due to this historical, we now have the definition of our calendar, with the phases of the moon and seasons.

There are two fields of study in astronomy: Observation and Theoretical. Theorist uses calculations and analytical models to describe celestial phenomena, while the observation does the opposite, confirming in practice the results of the theory.

Sundial

This astronomical instrument is considered one of the oldest observation tools of our nearest star: THE SUN.

With him we can understand the operation and duration of the day, being able to analyze its behavior and anomalies. The Sundial is the only mechanism that shows us the true duration of the hours, which is not the same every day. The 24 hours we know, were created through a mathematical calculation (equation of time), obtaining an average of the time to define the day.

The model of this Sundial is the "Horizontal", which uses a level surface, with the distribution of the true hours of the Sun (quadrant) and a fixed pointer (gnomon), being positioned so that the movement (east - west) creates through the pointer, shadows that indicate the hours.

Solar Analemma

The movement of the Sun creates over a year a "Graph" (set of points that are related), being easily observable through the capture of images (photos), throughout the year. These images need to be taken in the same place and time, for every month. The result of these overlapping series of images is the Solar Analemma, which looks more like an 8 (eight) or symbol of infinity.

This is the movement of the Sun that creates the different climatic seasons. There is a model of Sundial that is based on the Analemma, where the pointer (gnomon) is not fixed, being changed of place in the different months, according to the movements of the Sun.

Beyond Astronomy - Vitamin D, the importance of the Sun for life:

For proper production of Vitamin D, the exposure to sun should be done without barriers, such as car windows or sunscreen, for 10 to 15 minutes, between 10:00 and 15:00hs (UVB incidence period).

One Tip: If you do not have a clock, just watch your shadow: if your shadow size is "smaller" than you, will be producing Vitamin D. If the shadow is "bigger," you will only be receiving UVA rays, which are "Photo Aging" and causing cancer. Stay tuned!

Seek Knowledge!