What is a “Micromoon”?

17 July 2014

The Short Answer (TSA)

Micromoon & Supermoon

The Supermoon gets a lot of attention.   But it’s opposite, the “Micromoon,” is often neglected.  A Supermoon is any Full or New Moon that happens when the Moon is closest to the Earth.

The Moon has an “irregular” orbit around the Earth.  So, sometimes the Moon is much closer than at other times.  The Moon is said to be at its “perigee” when it is closest to the earth.  When the Moon is both (1) a Full Moon and (2) making its closest approach to the Earth, it is called a Supermoon.  A Supermoon is worth looking at because the Moon in the sky looks visibly bigger as it gets closer to the Earth.

But the opposite also happens.  When the Moon is farthest from the Earth, it is said to be at its “apogee.”  When the Moon is both (1) a Full Moon and (2) farthest from Earth, it is called a Micromoon.

Why does the Micromoon get so little attention?

First, "the smallest Moon you could ever see in the sky" just seems like a “smaller” event than "the largest Moon you could ever see in the sky."

Second, Supermoons are wrapped up in a controversy.  When the Moon is close to the Earth, it exerts more gravitational pull on the Earth.  For example, the ocean tides are stronger when the Moon is closer to the Earth.

Some believe that the Super Full Moon causes earthquakes and volcanic eruptions.  The theory is that, when the Sun and Moon are on opposite sides of the Earth, pulling in opposite directions, the gravity “tug-of-war” puts extra strain on the surface of the Earth.  And, when there's not only a Full Moon, but the Moon happens to be at its closest approach to the Earth, the increased gravity is more likely to cause disturbances like earthquakes.

Some believe that more stress is put on the Earth's surface at the New Moon, when both the Sun and Moon are together on one side of the Earth.  And, when the New Moon is also a Supermoon, with the Moon at its closest approach to the Earth, the gravity exerted on the Earth’s surface is at its very strongest.  So, does gravity from Super New or Full Moons cause earthquakes or volcanic eruptions?

Although there seems to be logic to the idea that more gravity could affect the surface of the Earth, science says no.  Studies have not produced any evidence that the Sun and the Moon, even when the Moon is at its closest, produce enough "extra" gravity to cause anything like an earthquake or volcanic eruption.  However, others disagree.

At any rate, the forgotten Micromoon is the smallest (not the biggest).  So, because the Microoon is farthest away from the Earth, it has the weakest gravitational pull on the Earth.   No one thinks the Micromoon could cause any trouble.  So, there is no controversy -- with the result that Micromoons gets very little attention.

Any Full Moon, when the Moon is more than 250,000 miles away, is a Micromoon.  When it comes to Micromoons, only Full Moon's count.  New Moons seem to be ignored.   So, a New Moon would not be called a Micromoon even when the Moon was more than 250,000 miles away.

The next Micromoon happens on 5 March 2015.

M Grossmann of Hazelwood, Missouri
(& Belleville, Illinois)
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17 July  2014