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A Blood-Red Moon

The first—and most common—usage of the term points to a fully eclipsed Moon. If you’ve ever witnessed a lunar totality, you may understand how this term came about and why it has become so popular: As the Earth’s shadow blocks all direct sunlight from falling onto the lunar surface, the Moon usuallytakes on a reddish color.

You can see the effect in the image below, which was taken during thetotal lunar eclipse in September 2015.

Eclipses in your city (with animations)

Why Are Blood Moons Red?

A total lunar eclipse happens when the Moon travels through the Earth’sumbra, whichblocks all direct sunlight from illuminating the Moon’s surface. However, some red lightstill reaches the lunar surface indirectly, via the Earth’s atmosphere, bathing the Moon in a reddish, yellow, or orange glow.

As the Sun’s rays pass through the atmosphere, some colors in the light spectrum—those towards the violet spectrum—arefiltered out by a phenomenon calledRayleigh scattering. This is the same mechanism thatcauses colorful sunrises and sunsets. Red wavelengths are least affected by this effect, so the light reaching the Moon’s surface has a reddish hue, causing the fully eclipsed Moon to take on a red color.

Depending on the composition of the atmosphere, different parts of the light spectrum are filtered out, so the Moon may also look yellow, orange, or brown during a total lunar eclipse.

Is a Blue Moon really blue?

What you can see during a total solar eclipse

Lunar Tetrads

The second definition ofBlood Moon hasspiritual origins, but it still refers to an actual astronomical phenomenon: alunar tetrad, a term astronomers use to describefour total lunar eclipses that happen in the span of two years.

The eclipses in a tetrad occur about six months apart, with five uneclipsedFull Moons between them. Usually, only about one in three lunar eclipses are total, and about four to five total eclipses can be seen from any single location on Earth in a decade (though this ratio can vary by century). This means that lunar tetrads arerare occurrences, leading some to attach special, even religious, significance to these events.

The2014–2015 lunar tetrad gathered a lot of attention because some religious organizations claimed that the eclipses in the tetrad were asign of the end times. They called the eclipses Blood Moons after a statement in theBook of Joel in the Hebrew Bible that referred to the Sun turning dark and the Moon turning red before the second coming of Jesus.

Other doomsday prophecies that fell short

How Often Do Lunar Tetrads Happen?

Italian astronomer Giovanni Schiaparelli calculated that the frequency of lunar tetradsvaries over centuries. Some have several lunar tetrads, while others do not have any. For example, the years between 1582 and 1908 did not have any tetrads, whereas the next 250 years—from 1909 to 2156—will have 17 tetrads.

The current century—2001 to 2100—will haveeight tetrads. The first tetrad of the 21st century took place in 2003-2004, the second was in 2014–2015, and the next will be in 2032–2033, with the following eclipses:

• April 25/26, 2032
• October 18/19, 2032
• April 14/15, 2033
• October 8, 2033

All eclipses 1900 – 2199

Hunter’s Moon

The third definition of a Blood Moon isunrelated to lunar eclipses. It originates from certain North American traditions, which use the term to describe theFull Moon in October.

It refers to the fact thatOctober is usually the time of the year tohunt game and prepare meat for the coming winter. The October Full Moon is also known as Hunter’s Moon or Harvest Moon.

Traditional Full Moon names

Upcoming 5 Total Lunar Eclipses

2026年3月2–3日 (火)

Lunar Eclipse(Total)East in Europe, Asia, Australia, North America, South America, Pacific, Atlantic, Indian Ocean, Arctic, Antarctica

2028年12月31日 (日)–2029年1月1日 (月)

Lunar Eclipse(Total)Europe, Asia, Australia, Africa, North/West North America, Pacific, Atlantic, Indian Ocean, Arctic

2029年6月25–26日 (火)

Lunar Eclipse(Total)Europe, West in Asia, Africa, North America, South America, Pacific, Atlantic, Indian Ocean, Antarctica

2029年12月20–21日 (金)

Lunar Eclipse(Total)Europe, Asia, North/West Australia, Africa, North America, South America, Pacific, Atlantic, Indian Ocean, Arctic

2032年4月25–26日 (月)

Lunar Eclipse(Total)South/East Europe, Asia, Australia, Much of Africa, Much of North America, Pacific, Atlantic, Indian Ocean, Antarctica

More details about upcoming Eclipses

Topics:Astronomy,Eclipses,Moon