Monday, April 14, 2014

The Blood Red Moon & The Tetrad

The total lunar eclipse of 20-21 February, 2008,
as seen from one of my CCTV cameras.
The Moon is just entering the umbra. 
Before the sun rises on Tuesday, the 15th of April, 2014, the Moon will have gone through the first of four total lunar eclipses that will be visible from the Americas. There is a lot of confusion arising from this, apparently, and some misinformation floating about.
After all, it's not like total lunar eclipses are very rare events. But first, let's talk about the actual eclipse itself. 
For those of us on the east coast, the eclipse begins at 1:20 AM EDT, according to the folks at "Sky &; Telescope". Other sources list this time as closer to 2:00 AM EDT. Regardless, this is the penumbra portion of the eclipse, and for the most part is barely noticeable. The Moon really begins to darken at 1:58 AM EDT; this is the beginning of the real eclipse. Slowly, the Moon will continue to move eastward in our sky (contrary to the direction the sky's moving, in fact, and with the Earth's rotation), until 3:47 AM EDT, when it will be mid-eclipse, deep within the umbra portion of the Earth's shadow. But it is not going to be dead center in our shadow; it will be off and towards the south. This should be manifest in a southern section of the lunar disk that is brighter, the variable being cloud cover on our planet, which effects the light that shines around the edge of our planet. This light is being lensed through our atmosphere. If the Earth did not have an atmosphere, a lunar eclipse would in fact be total as long as it passed through the Earth umbra. 
The total portion of the eclipse ends at 4:25 AM EDT, as the Moon begins exiting the umbra portion of the Earth's shadow and begins getting brighter. The final partial portion of the eclipse ends for us here on the east coast at 5:33 AM EDT (earlier for us here in New England; due to the fact that we are further east, the Moon will be setting, and the Sun rising, of course). For our friends just a little further west, the entire eclipse will be visible. For the most part, though, both North and South America will see a total eclipse, for again as I mentioned, the penumbra eclipse really isn't that noticeable.
Now on to the bad information that's floating around.

Eclipse visibility chart from the
Wikipedia entry for the 15th April 2014 lunar eclipse.
(Image couresy Wikipedia)
First, unlike a solar eclipse, it doesn't matter where you are during a lunar eclipse. From Boston, you will see the same part of the eclipse as Buenos Aires. This is because we are looking at the shadow being cast, not from it. 
Second, there is no guarantee that the Moon will turn just "blood red". There is a good chance that it will, but remember what I mentioned up there; the real variable is going to be cloud cover around the Earth's atmosphere. The more clouds, the more likely it will be darker. The fewer, the brighter. In short, it could go from blood red to dark chocolate. 
Finally, there is much ado about this eclipse and the "tetrad" that it marks the beginning of. A "tetrad" in this case refers to a series of four lunar eclipses spaces at six month intervals. Usually, it is not uncommon for there to be three lunar eclipses over a one year period. This tends to be the most common pattern, a "triple". Tetrads are not as rare as it would seem, in fact. The last tetrad occurred in 2003-2004 (not quite eleven years ago). What's unusual about this tetrad is that it will be visible from the Americas. 
So, what does this mean?
Absolutely nothing.
There are people who are desperately looking for some sort of meaning in this, yet in reality one does not exist. Have historic events occurred near or around these events? Certainly; after all, really triples, tetrads and just good old lunar eclipses are not that uncommon. As one of my high school teachers used to say "correlation does not equal causation". In other words, they are coincidences, and nothing more. We seek answers, we look for them hard enough and think we see patterns. It is our desire to find those patterns that actually produces them. 
If you get a chance, try and stay up late to catch this wondrous event. For my friends further west, you won't need to stay up nearly so late. For us here in the east, it looks like an all nighter.
And sadly, it's looking increasingly like a no-go here in Connecticut. Clouds are rolling in, and the rain is coming. 
We'll see.

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