Astronomers rarely use the term “Blood Moon.” When they do, they are usually using it as an alternate name for the Hunter’s Moon, the full moon that follows the Harvest Moon, usually in late October. The Hunter’s Moon, like the Harvest Moon, rises slowly on autumn evenings so that it shines through a thick layer of the Earth’s atmosphere, and is colored red by what those who study the atmosphere call Raleigh scattering as well as smog and air pollution.
On rare occasions, the light reaching the moon resembles the color of blood, but there is no way of predicting this in advance. So there are no grounds to call any particular lunar eclipse a blood moon until it actually shows its color. But when it does occur, the explanation is simple.
“During a total lunar eclipse, white sunlight hitting the atmosphere on the sides of the Earth gets absorbed and then radiated out (scattered). Blue-colored light is most affected,” NASA officials wrote online. “That is, the atmosphere filters out (scatters away) most of the blue-colored light. What’s left over is the orange- and red-colored light.”
When a lunar eclipse is the first of a series of four total lunar eclipses in a row, it’s called a “tetrad.” (The lunar eclipse of September 27, 2015 will be the fourth). Such a series of four total eclipses in a row is not an overly rare event. The last such series happened in the years 2003 and 2004, and it will occur seven more times in the current century.
So while a tetrad of total lunar eclipses is somewhat unusual, it is not extraordinarily so, and certainly nothing to make a fuss about. After all, the only thing that happens during a lunar eclipse is that the Moon spends a couple of hours passing through the Earth’s shadow, hardly something to be concerned about.
While we now have a clear understanding of much of what’s going on in the sky, people once routinely believed that astronomical events such as eclipses and comets were harbingers of disaster and doom.
A colleague of mine, Geoff Gaherty at SPACE.com recently cited a book which incredibly has made The New York Times best seller list: Four Blood Moons: Something is About to Change (Worthy Publishing 2013) penned by John Hagee, which suggests a link between the four total lunar eclipses that will occur over the next two years and the prophecy in the Bible about the end of the world.
Gaherty writes, “When the mechanisms behind eclipses were less well understood, they were thought to be omens of bad tidings, just as comets were. Now people know that these are just normal events in the clockwork of the solar system, things which have occurred regularly for thousands of years and which will occur for thousands of years into the future.”
“Associations between ‘disastrous’ events and normal astronomical events are all fabrications of the human mind, as people attempt to find explanations for why disasters affect them. Because of the Internet and cable news channels, people now hear reports of disasters from around the world, including earthquakes, tsunamis and volcanic eruptions, which they never would have been aware of in the past.”
So, my advice to all of you who are blessed with clear skies on and night of a lunar eclipse is, don’t sweat it! This is a beautiful, natural and predictable phenomenon for all of us to see and enjoy. And since we like making predictions here at the Farmers’ Almanac, I’ll go out on a limb and state that, after the final lunar eclipse of this foursome passes into history in September 2015, we all will still be here.