Total lunar eclipses, or “blood moons” are rare, but even rarer are lunar tetrads. The earth has been, and will be spectator to a series of rare astronomical events this century, including the blood moon that will occur on April 4th, third sequence in the much rarer lunar tetrad. Some say the strange astronomical events could be mystical signs of the times.
A lunar tetrad is when there is four total eclipses happen in a row. The phenomenon can be very rare, and other times more common. Italian astronomer Giovanni Schiaperelli (1835-1910) calculated that lunar tetrads happen more commonly over some centuries than others. Some 300 year intervals have several tetrads, while other 300 year intervals have none. The years 1852-1908 had no tetrads while in the current succession of three centuries, we will see 17 tetrads.
A “blood moon”, or total lunar eclipse, the kind that makes up lunar tetrads, are somewhat rare in their own right, occurring once in three. A “blood moon” is when the earth moves between the moon and sun, and eclipses the full moon; while all sunlight is blocked, but the cascading rays of the sun still light up the moon. Because the light travels through the Earth atmosphere, a process known as Rayleigh scattering, (the same process responsible for making the sky such pretty colors during sunrise and sunsets), the moon appears red, hence the name, “blood moon”.
The first of this series of moons in the lunar tetrad happened on April 15, 2014. The second happened on October 8, 2014. This moon of the lunar tetrad will happen on April 4th, with the fourth following on September 28, 2015. The eclipse this year will begin at 9:01 Greenwich Mean Time. The most dramatic of the “blood” effect will begin an hour into the eclipse when the moon moves into its umbral shadow. This eclipse will be the shortest of the series because the moon this year will pass through the edge of the Earth and not at its center.
This astronomical phenomenon has stargazers, spectators, and astronomers all excited, but also some theorists, who say the phenomenon of late is a tell tale sign of something more, with some being more grandiose then others. There is even a group that believes the lunar tetrad is a sign of the apocalypse.
Earlier on in the decade, Comet Ison was vaporized by the sun on November 28th, 2013. Two solar eclipses are upcoming as well.
If you wish to see the third moon in the current lunar tetra, it will be visible for those in most of North America.