Supermoon is a natural phenomenon of the moon appear larger (about 7 percent) than usual. This happens because the moon is at the position (distance) closest to the earth.
According to the science of astronomy, the moon around the earth in elliptical orbits, so that there are two positions of the moon to the earth, namely:
- The moon is at the farthest point to Earth (apogee)
- The moon is at its closest to Earth (perigee). Supermoon phenomenon will occur at perigee position because the moon will appear larger due to the distance the moon is close to the earth.
The phenomenon of the moon is in a position closest to the Earth happens every month with a period of about 27.3 days. The phenomenon of the full moon is also a monthly event with a period of about 29.5 days. Because of differences in this period, the perigee is not always in conjunction with the full moon. Perigee and full moon phases occur simultaneously will be repeated every 18 years is 241 x 27.3 multiples of the same day with 223 x 29.5 days.
Distance of the moon is closest to the earth can be reached 356.577 kilometers from Earth. This distance, 30,000 kilometers closer to the average distance Earth-Moon range 382 900 km. Moon in the position closest to the Earth will have an impact on the further strengthening of the tidal effects on Earth. Sea water would have high tide because the force of gravity will be stronger when the moon closer to earth.