The Moon moves ≈1 km / s, in an elliptical orbit and its distance from Earth varies greatly from about 50 000 km. At its apogee, the point farthest from the Earth, it is averages at 405 700 km while at perigee, it is averages at 356 400 km.
Supermoon is a term coined by Richard Nolle astrologer in 1979. Supermoon occurs when the Moon is closest to the Earth, then it is bigger and brighter than any other time. The Supermoon is even more spectacular when it coincides with the full moon, at that time, we observe a moon of a high brightness and a beautiful shine. Of course when it is at its perigee, it appears larger, exactly 14% larger, 14% is the difference between the two apsides (nearest point and the farthest point relative to the Earth) of the orbit of the Moon.
The moon has an elliptical orbit around the center of the Earth, but the reality is a bit more complex, dual system that is the Moon and the Earth revolves around the common center of mass called barycenter. Their center of gravity, which is not fixed, varies according to their average separation distance (≈384 400 km) and is located on the Earth-Moon line, inside the Earth ≈1708 km of the surface and ≈4670 km from the center of the Earth, the radius of the earth being ≈6378 km (see note).
As the center of mass of the Earth / Moon system is located inside the Earth, it simply says that the moon revolves around the Earth. Earth it rotates around a point that moves within itself, and it describes spirals lower along its orbit, i.e. it waltz with the Moon around the Sun.
Given the distance from the Sun., its gravitational influence on the Earth / Moon barycenter is negligible. As seen from the Sun, all the couple of the two stable body Earth / Moon forms a uniform gravitational field. The gravitational field surrounding the pair is considered as a field of a single object. However, there is also a barycenter Sun / (Earth / Moon) calculable with the same formula (see note).
Supermoons occur frequently, every lunar month, i.e. every 27 days 7 hours and 43 minutes is the period of revolution of the Moon also called the orbital period. This is exactly the time it takes the moon to complete a full rotation around the Earth or the time interval between two perigee of the Moon (27.55455 days on average).
The full Moons occur every 29 days 12 hours 44 minutes. This is exactly the time it takes the Moon to return to the same apparent configuration relative to the Earth and the Sun.
The coincidence between the super moon and the full moon takes place 1-5 times a year. In 2014, the super moon was 14% larger and 30% brighter than a normal full moon, according to NASA records.
What are the effects of the supermoon?
Besides folk effects such as increased childbirth, suicide, disease, crime, social unrest and other natural disasters, the main effect of the super moon is obviously the effect on tides. At this time there, the ocean tides is maximum, in some places of the Earth, the foreshore, i.e. the difference in height between high tide and low tide, exceeds more than 15 meters.
The effects of a supermoon on Earth are minor, and according to the most detailed studies by seismologists and volcanologists, the combination of the supermoon (closest to the Earth) and full moon (aligned with the Earth and Sun), should not affect the internal energy balance of the Earth since there are lunar tides every day. The Earth has a tremendous amount of internal energy and small variations in the tidal forces exerted by the moon are not enough to fundamentally alter the internal balance that drives plate tectonics.
NB: calculation of barycenter Earth / Moon:
Barycenter TL = (ML/ML+MT) x DTL = 4670.78 km
ML = Mass of the Moon =0,073477 x 1024 kg
MT = Mass of the Earth = 5.9736 x 1024 kg
DTL = Distance Earth / Moon = 384 400 km
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Image: Supermoon is a term coined by Richard Nolle astrologer in 1979. Supermoon occurs when the Moon is closest to the Earth, then it is bigger and brighter than any other time. The Supermoon is even more spectacular when it coincides with the full moon, at that time, we observe a moon of a high brightness and a beautiful shine. At perigee, the Moon is 14% greater than at its apogee. 14% is the difference between the two apsides (nearest point and the farthest point relative to the Earth) of the orbit of the Moon. Credit astronoo.com