What illuminates the Earth during the night?
At night the Earth’s surface is lighted by the Moon and some other illuminants. During the clear lunar nights when your eyes get adapted, i.e. get used to the lunar light you can enjoy the night scenery. The landscape is covered with the moon light; it attracted the artists and the poets many times. One of the maxims said by Kozma Prutkov is the following: “if you are asked: what is more effective, the sun or the moon? Always answer that it is the moon. The sun shines during the day when it is already light; and the moon illuminates during the night”. The strongest illuminant during night is the moon. The full moon illumination produced by a “young” moon is 1/5 higher than the one produced by the “old” moon. This may be explained by the fact that the moon’s surface turned towards the Earth has the spots, i.e. the lunar ocean and sea zones are positioned by fits and starts: if you look at the moon “portrait” you will see that the left part of it has more dark zones that the right one. When there is a moonless night (the most appropriate time for studying the starry sky), the land objects are still visible, though rather weak. They are lighted by the stars. The more human eyes adapt to the darkness, the more he distinguishes weak stars. The overwhelming majority of the stars is located in the Milky Way area. This is the most luminous part of the starry sky. The first trials for the star glow evaluation at night time were held in 1901 by Newcomb, an American astronomer. He noticed that the whole illumination created by the stars makes only one part of it, if to observe from the Earth’s surface during the moonless night. Other planets’ illumination towards the Earth is insignificant. So, what kind of illuminant is there then? This illuminant was discovered in the same year by the German scholars with the help of capturing the night-sky spectrum. The green lines were disclosed along the spectral plates, which are characteristic of the aurora Polaris. They made the suggestion that the continuous green light releases the light source located in the Earth’s atmosphere. Between 1909 and 1015 the Dutch and British scholars were investigating the Milky Way spectrum at different latitudes and even at the areas where the polar light is rarely observed. Every shot showed the green line. The closer to the horizon were the photos taken, the brighter was the line. They could only make the conclusion that the whole firmament illuminates the continuous light every night, which is almost alike with the polar light.
Therefore, the night airglow was discovered. It turns out that the Earth’s atmosphere and its “air coat” not only heats the Earth by swallowing the warmth that is released to the outer space by the sun and not only protects the Earth from destructive ultra-violet rays and “celestial rocks”, the so called meteorites, but also illuminate the Earth during the night. That is, when there is no moon, the Earth’s atmosphere is the main “illuminant”.
Not all layers are lighted in the atmosphere but the upper, rarified on heights from 100 to 300 km. Under the sun’s ultraviolet emission influence the splitting occurs, or like others say, the molecular gas dissociation. When atoms collide with each they again become molecules and release the radiant energy.
Why is the moon considered to be a satellite?
According to the astronomical studies the satellite is a body that rotates around a huge-sized body and is hold by the gravitation force. The moon is the Earth’s satellite!
The artificial satellites are man-made space vehicles that rotate around the Earth or any other planet. There are launched by a number of reasons: either for the research studies or weather studies, as well as for communication.
The Moon is a unique phenomenon in the Solar system as there is no other planet that has such a large satellite. The moon is the only Earth’s satellite, though it is a huge one and is set close to the Earth!
You can observe it with the naked eye, unlike any other planet through the telescope. The telescopic observation and large photographs show that its beautiful surface is rather irregular and extremely complicated. The active illumination of the Earth’s natural satellite has broken out since 1959, the time when our country, as well as the USA launched the space probes and automatic space stations towards the Moon for its overall investigation. And even today, these space probes supply a lot of useful information for the lunarians (scientists who study the moon). This planet is a very mysterious kind of satellite. People had not seen its backside until 1969 when the automatic station named “Luna-3” captured the invisible part of the lunar surface. Later, the Moon’s surface maps were constructed based on the shots made with the help of the native space station “Zond-3” and American space probes “Lunar Orbiter”. The lunar automatic space station flying activities as well as the expedition landing helped a lot to answer the whole list of answers asked by the astronomers. However, they have also posed some new tasks for the astronomers in return.