When the Earth is positioned between the Sun and the Moon, it enters the region of the Earth’s shadow, causing a lunar eclipse.
Eclipse is a term of Greek origin that means fainting or abandonment, which refers to the obscuration of light when observing the Moon or the Sun during this phenomenon.
The ancient Chinese, Babylonians and Greeks, had already observed and recorded eclipses that constitute landmarks that help to link astronomy with history and chronology. These peoples already knew the mechanics of this phenomenon and foresaw its happening well in advance.
In the 4th century BC, Pythagoras observed the circular shadow that the Earth cast on the Moon, and he used this fact to prove that the Earth was spherical.
The Moon’s translational movement is approximately 29.5 days, and allows us to observe the phases: New, Crescent, Full and Waning. In the Nova phase, a Sun-Moon-Earth alignment takes place, the terrestrial observer cannot see the illuminated face of the Moon, as it is not facing our planet. During the Full phase, the Sun-Earth-Moon alignment takes place and, in this way, the illuminated face of the satellite faces Earth. The entire lunar disk is visible and we have the beautiful Full Moon nights.
The lunar eclipse always happens during the Full Moon, as it is at this stage that the Earth is positioned between the Sun and the Moon. However, this phenomenon does not occur every month because the Moon’s orbit around the Earth is not in the same plane as the Earth’s orbit around the Sun. This inclination of the Moon’s orbit plane is approximately 5.2° with respect to the Earth’s orbit plane with respect to the Sun.
the inclination of the MOON-EARTH orbit with respect to the EARTH-SUN orbit.
When the sun is on the line of intersection of the plane of the Earth’s orbit around the Sun and the plane of the Moon’s orbit around the Earth (line of nodes), the Moon enters the region of the Earth’s shadow causing a lunar eclipse.
During the observation of a total eclipse of the Moon, the Moon is not totally invisible, as in the New Moon phase, because the light coming from the Sun is refracted by the Earth’s atmosphere. This refraction and the amount of dust in the atmosphere makes an observer here on Earth see our natural satellite with a reddish color.