History, unfortunately, did not preserve the names of the designers of ancient monumental structures, such as the pyramids in the Giza Valley in Egypt or the Temple of the Sun in South America. Only one thing can be said with confidence: the one who built and especially the one who designed these structures not only knew how to achieve perfect horizontal surfaces and clearly maintained verticals, but also had excellent orientation to the cardinal points. They definitely knew such concepts as “zenith” and “nadir”. This is perfectly visible by the ideal location of the huge structures and their impeccable proportions.
What is zenith, nadir
In short, nadir is the opposite of zenith. But first things first. We will orient ourselves in our earthly space. If you use a compass (in most modern smartphones equipped with a magnetic sensor, it is installed as an application, but you can use the usual one with a magnetic arrow) and become a face to the north, the picture will be like this.
The eyes of the observer will look north, behind the south. Far eastern countries will lie on the right hand, and west on the left side of romantic sunsets and wild cowboys.
Directly above your head in the very center of the heavenly dome will be the zenith. Well, and nadir is its opposite, which is below.
All this is simply and clearly shown in the diagram.
In what areas do they use the concept of nadir
If you really want to see the exact direction of the nadir, just use the usual plumb line. When the load calms down and the thread freezes motionless, the tip, like an arrow, will indicate the desired direction. However, builders are more interested in the deviation of structures from verticals and horizontals, they are not interested in where the nadir is located. Astronomy uses this concept to indicate the sides of cosmic bodies, relative to the location of a particular point on their surface.
There is another area where you can often hear the word "nadir". This is aviation and astronautics. When calculating the trajectory and directions of an air flying or spacecraft, the direction of the nadir is the direction of gravity, which plays a key role in the calculations.