Our Moon

In the days before television, electric lights, instantaneous communication and immediate gratification there was our Moon. Its cycle was constant, its phases predictable and its influence on the human race was immense.

A quick check of my Webster's Unabridged shows moon influence from blue moon (once in a) to moonshine(r) and many words and usages in between.

When I was young old farmers planted crops timed to the phase of the Moon. Fishermen counted on the "dark of the moon" to produce a better bite and workers at mental hospitals around the world averred that lunatics bloomed in the light of the full moon.

I sometimes wonder how modern children can get by with no knowledge of the moon and its phases. This knowledge isn't taught today but,then, it wasn't taught in the days of my youth either. Back then it was absorbed from the universal knowledge of our elders. People in those old days needed to know the ways of the moon to properly direct their own lives so children picked up the knowledge by simple association.

Our moon was used as a device to keep track of the calendar; it was used as a way to forecast the weather and the full moon was synonymous with romance and lunacy. Dare I say that those two conditions are sometimes difficult to differentiate.

There are special terms for different phases of the moon. Our next lunar cycle begins tomorrow, Sunday, 9/13/15, with a new moon and transitions through the waxing crescent (first seen in the west just as the sun goes below the horizon), the first quarter, the waxing gibbous, the full moon, the waning gibbous, the last quarter (third quarter), the waning crescent (visible in the eastern sky just before the sun rises) and back to the new moon for the subsequent cycle.

Along the way during our next lunar cycle we'll have a total lunar eclipse on September 27th starting just before moonrise for us (6:55 PM) and ending at 9:27 PM. If our sky is clear it will be a spectacular sight here in the Seattle area. What we might call prime time lunar viewing.

In Asia, even today, the moon is viewed with respect. In times past the Japanese built special viewing platforms or gathered on boats to watch the full moon (especially the autumn moon) while reciting poetry and eating "moon cakes" (tsukimi dango), a kind of rice cake. My wife, Ikuko, fondly remembers those evenings of watching the full moon rising over Hakata while eating tsukimi dango.

We are nearing the end of the current moon cycle with only a day left before the new moon. This morning I went up on my roof (the flat part) to see if I could catch a glimpse of the last of the waning crescent. Moonrise was at 6:09 this morning so I would have only fifteen or twenty minutes to catch that glimpse before the sky became too light to see the tiny sliver of lighted moon on its last day before changing over to the new moon.

Hoping to get some photographs I took my camera, as well as my phone, up on the roof but I'm sorry to say there was no sighting this morning. The eastern horizon and lower atmosphere was obscured by the smoke from the many wildfires still burning in our state making it impossible to see through that red haze before the sky became too light to see the moon. Our "morning star" the planet Venus was the brightest light in the sky as it was well above the smoke and haze.

The new moon is invisible to the naked eye because it comes between us and the sun. Even with specialized equipment if you see the moon in this phase it is dark because the sun is shining on the side away from the earth. We often refer to that side as the dark side of the moon but when the moon is dark on the side facing us (new moon) it is a full moon on the back side of the moon which is facing the sun. It would be an amazing sight to an observer in a spacecraft between our moon and the sun since the view would be a full moon in front of a full (fully lighted) earth.

So, how does the moon work so that we see the various phases month after month? Why is it that sometimes the moon is lower in the southern sky and sometimes it's high overhead? Why is the moon's perceived size sometimes larger or smaller than normal? And perhaps most important, is the moon really made of green (unripened, not the color) cheese as so many people have believed over thousands of years?

Before we can think about the rest of those questions we need to figure out how the moon orbits the earth.

There are several things about the moon's orbit around the earth that are necessary to know before we can explain its appearance. The most important of these is the time of the orbit which is approximately 28.5 days. It's also important to know that that orbit isn't a true circle but is a little egg shaped with an eccentricity of about 5.5 per cent.  We need to know the plane of that orbit is offset from center by a little over five degrees. The moon's rotation (locked in by tidal influences) is the same as the time of its orbit so we always see the same side. Actually we see a little more than half because when the moon is high in the sky we see a little more of its southern portion and when it's low in the sky we see a little more of its northern portion. Finally, we need to remember that our earth is tilted on its axis about 23.5 degrees. (Interestingly, this tilt changes from about 22 to 24.5 degrees and back over a 41,000 year cycle.)

Now that we have these facts at our fingertips we can see how the appearance of the moon is shaped by the various factors.

First let's figure out how we see the various phases.

During a new moon the moon is in front of the sun (usually not directly or we would see a solar eclipse) so we don't see any portion of the moon lighted by reflected sunlight. The following night we can see (if we have a clear sky and look closely) the first tiny sliver of the waxing crescent in the western sky just after the sun disappears below the horizon. On the second day after the new moon we see a larger slice of the waxing crescent a little higher in the sky and for the next five nights it grows larger and higher in the sky until on the seventh night we see the first quarter.

Note that the waxing moon grows from the right side since that is the side lighted by the sun and after reaching full the moon wanes with the lighted side on the left, again because that is the side lighted by the sun.

Now we must qualify this sequence because we are looking from the northern hemisphere. If we were in South America or New Zealand everything would be reversed and the waxing crescent (and the rest of the phases) would grow from the left side until full and then wane toward the right side. I know it sounds confusing but it's the same moon it's just that we are looking at it toward the south in the northern hemisphere and we look toward the north while in the southern hemisphere. Is that clear? I knew you'd understand.

Now, this entry is long enough and it doesn't have any photos or even drawings so I'm going to post this and continue in a few days, Maybe I'll be able to catch the early waxing crescent, or at least, the first quarter, and post some photos next time.

Meanwhile, if you have a view of the sky watch for the waxing crescent beginning Monday night. Here in Seattle we always have a battle with the clouds beginning about this time of year so you might have to watch for the moon playing hide and seek through the clouds but it will be there as dependable as can be. It's our duty to find it and it will be right where it's supposed to be if the clouds allow us to see it.