Supermoon today and a chance to observe the moon illusion

“supermoon” is the coincidence of a full moon (or a new moon) with the closest approach the Moon makes to the Earth on its elliptical orbit, or perigee, leading to the technical name for a supermoon of the perigee-syzygy of the Earth-Moon-Sun system. The 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 such as earthquakes and volcanic eruptions. However, the evidence of such a link is widely held to be unconvincing.

A supermoon will occur today, Saturday 5th May.

A “supermoon” typically happens once a year and at perigee it is 14 per cent larger than an average full moon, but not much larger than the full moons that precede and follow the supermoon. The closeness of the supermooon does cause higher tides but only about 2 or 3 cms higher than average levels.

Moon Illusion

The moon illusion refers to the moon seeming larger when it is near the horizon than when it is high in the sky. Some people judge it to be as much as twice as large, but the average estimate is 50% to 75% larger. But this is only an optical illusion.

Physical and cognitive explanations do not yet explain the illusion or why some people cannot observe it. The debate goes on.

The so-called “moon illusion” or “moon effect” has perplexed people since earliest historical times, at least as early as the 7th century BCE. It is described in early Greek and Chinese writings. Aristotle mentions it in 350 BCE.

No tidal waves or other catastrophic effects are expected.

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2 Responses to “Supermoon today and a chance to observe the moon illusion”

  1. Nate Says:

    Man, “perigee-syzygy of the Earth-Moon-Sun system” sure is a mouth full. I see why the term “supermoon” is so appealing! I’d like to see this moon, but unfortunately it is rainy and the clouds are blocking the view. Oh well, still an interesting read!

  2. Where to view the annular solar eclipse of May 20th « The k2p blog Says:

    […] days after the “supermoon” of May 5th when the moon was at perigee, the moon will be at apogee and will be too small to obscure th entire […]

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