19 March 2011

Vernal Equinox, Super Full Moon, and other astronomical musings

I enjoy sharing highlights of the sky with friends and have been blogging for several years now, pointing out events of astronomical interest here as The Urban Astronomer. I was surprised to see the excitement and questions about the Super Full Moon, the coincidence of nature that is leading to a full moon at perigee today. The fact that the general public is being scared into thinking something bad is about to happen is unfortunate, but the fact that people will be out tonight looking at the full moon is the good outcome that I wish for. Of course, there is absolutely nothing to be worried about. Every 29 days the Moon swings a bit closer to the Earth than other times of the month, and that pattern of perigee and apogee, full and new, repeats in a beautiful "super pattern" every 18 years, something now known (but likely not fully understood) by the many who are reading about the Super Full Moon being the biggest one in 18 years.

There are numerous patterns and cycles in the heavens. Tomorrow, March 20th, is the Vernal Equinox, the semi-annual moment when the length of the day is exactly 12 hours everyone on Earth. I like that dynamic, a twice-a-year event in which we are all given equal periods of sun above the horizon and below the horizon, regardless of your latitude, regardless of whether you are in the Northern or Southern Hemisphere. That is a moment of beauty in the grand annual rhythms of our home planet.

The pattern of lunar repetition that lasts for just longer than 18 years is also responsible for the cycle of lunar and solar eclipses that take place around the world. I witnessed a total solar eclipse in Europe in July 1999, and the celestial dynamics of that eclipse will exactly repeat in August 2017 when a wonderful total solar eclipse will sweep across the United States. For me, it will be a rare chance to be standing in the shadow of the Moon on the second passing of this particular alignment of Moon, Earth and Sun, one that will be far more dramatic and meaningful to me than any particular Super Full Moon you might encounter between now and then. But in the end, if you can find some meaning and solace looking up at the Moon tonight, savor the moment and mark your calendar for April 2029 when the conditions will align themselves and present you with a chance to relive this magic moment when you saw a particularly big and impressive full moon. That is something worth pondering, and the rest of the media hype you are hearing right now should be simply ignored.

Image courtesy NASA.


Paxjorge said...

Enlightening post, thanks! I happened to be in the north of France in '99, it was a very impressive moment, humbling even.

Paulie said...

I was vaguely aware of the perigee full Moon a couple weeks ago, but what really caught my attention was that people not really interested in astronomy started asking me about it. It seems the media created a story out of what I consider no big deal. I the U.S., the Moon wasn't even up when perigee and maximum illumination occurred in the afternoon. I see that next month's full Moon will occur about 18 hours after perigee, but, so it too will be a larger than usual full Moon, but without the hype.

But as you point out, the hype was good for building public interest. I estimate that around 400 people came out to Chicago's Adler Planetarium to see the "Super Moon," but were let down by the clouds. Oh well. Maybe some of them will gather next month for our ritual of observing the full Moon rise over Lake Michigan.

Also, as we were packing our gear at the end of the session, I mentioned 2017's solar eclipse to my friend Joe. The path of totality runs through southern Illinois/St. Louis (or very near anyway). I'm looking forward to that day, to be standing in Luna's shadow.