This year the full moon in April is a bit special. a superluna, so called since 1979 when the position is found closer to the Earth than the average distance. So it will appear a little larger than usual, although it is difficult to notice with the naked eye. At 5.33 am (Italian time) on Tuesday 27 April he will be at a distance of 369,869 kilometers, while the average distance of 384,403 km (measured from the center of our planet to the center of the Moon). But this is not the peculiarity: in fact, there are 5-6 supermoons per year. Rather, in 2021 it will always be superluna until September due to the fact that the orbit of the Moon around the Earth is not a perfect circle, but an ellipse with a maximum and a minimum distance, which in turn are not always constant but vary under the gravitational influence of the Sun and, to a much lesser extent, Jupiter.
The particolarity
April is not even a record supermoon, with the closest point to Earth being reached on November 14, 2016 at a distance of 356,509 kilometers and only to be surpassed in 2034. So what’s special about it? The tide it generates. The current full moon occurs exactly when its orbital plane intersects that of the Earth (called the ecliptic) in our planet’s orbit around the Sun. The plane of the Moon forms an angle of 5.14 degrees with that of the Earth. Therefore for a while its orbit is above the ecliptic, and for a while below. The two planes intersect at what are called nodal points: an ascending one when the orbit of the Moon passes from below to above that of the Earth, descending in the opposite case.
The next risk factor
The position of the nodal points of the Moon undergoes a precession and changes in a cycle lasting 18.61 years. We are currently in a downward phase, and therefore the influence on the tides is less. The downward phase will last until 2025, then it will start to grow. As sea levels are rising more and more due to global warming, the influence of the astronomical tide at nodal points could become a risk factor for coastal cities such as Venice in the near future.
April 26, 2021 (change April 26, 2021 | 20:26)
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