A supermoon is a full moon or a new moon that nearly coincides with perigee—the closest that the Moon comes to the Earth in its elliptic orbit—resulting in a slightly larger-than-usual apparent size of the lunar disk as viewed from Earth. The technical name is a perigee syzygy (of the Earth–Moon–Sun system) or a full (or new) Moon around perigee. Because the term supermoon is astrological in origin, it has no precise astronomical definition. The real association of the Moon with both oceanic and crustal tides has led to claims that the supermoon phenomenon may be associated with increased risk of events like earthquakes and volcanic eruptions, but no such link has been found. The opposite phenomenon, an apogee syzygy or a full (or new) Moon around apogee, has been called a micromoon. Definitions The term supermoon is attributed to astrologer Richard Nolle while reading "Strategic Role Of Perigean spring tides in Nautical History and Coastal flooding" published in 1976 by NOAA Hydrologist Fergus Wood. In practice, there is no official or even consistent definition of how near perigee the full Moon must occur to receive the supermoon label, and new moons rarely receive a supermoon label. Nolle Nolle described the concept in a 1979 edition of Dell Horoscope including both full and new moons, but has never outlined why he chose 90% nor has provided a definitive formula for determining if a given full or new moon is "super". The basic 1979 definition read: Nolle amended his definition in 2000 specifying the distance of a given full or new moon be judged against 90% of the mean distance of perigees. Nolle (incorrectly) referenced In 2011, Nolle added apogees to consideration explaining that he based calculations on 90% of the difference in lunar apsis extremes for the solar year. EarthSky analyzed Nolle's tables and described the updated definition as a full or new moon is considered a supermoon if where is the lunar distance at syzygy, is the lunar distance at apogee, and is the lunar distance at perigee. Nolle based those the mean apsis extremes referencing (incorrectly) the Wikipedia article on the subject arriving at: Nolle also added the concept of extreme supermoon in 2000 describing the concept as any new or full moons that are at "100% or greater of the mean perigee". Espenak The term perigee-syzygy or perigee full/new moon is preferred in the scientific community. Perigee