What does Zenit mean, where does this term used above all in space and astronomy come from, as definition and difference compared to nadir as poles delimiting the horizon.
Meaning of zenith
When making astronomical observations regarding the sky, the point corresponding to the intersection between the line perpendicular to the plane of the horizon passing through the observation point with the visible surface of the celestial hemisphere is called the zenith.
In short, the zenith is nothing more than the imaginary point located perfectly above the head of the one who is making this type of scientific observation.
In a position diametrically opposite the zenith is the nadir, from this particularity derives the fact that Zenit and Nadir are defined as the poles of the horizon.
To give a practical example, just think of the phenomenon of the sun placed exactly at the zenith, an event observable only at noon at the equator during the equinoxes or in the tropics at the solstices.
To simplify, you can imagine a straight line that, starting from the center of the observer's head, stretches towards the sky at an angle of ninety degrees, until it virtually touches it in a virtual point called Zenit.
When a star reaches a height equal to 90 ° with respect to the observation point it is said that it is at Zenit, i.e. located above the observer, who, in order to observe it, must stand perfectly straight with the head bent backwards as far as possible, or alternatively lying down.
This observation can be put into practice only on a certain day with a precise time, when the declination of a star corresponds to the same value and cornerstone of the latitude to which the observer is placed.
