The Moon goes through its cycle of phases each month, as it has since the Creation. Everyone in the world can see the Moon, even from light-polluted urban areas where few stars can be seen, if any. There is a very simple order to the Moon's cycle, easily learned by diligent observation. And it can be a simple joy to follow the changing phases from night to night.
We got a nice email recently from Sharie from Kentucky who wrote:
"Last year I asked my son (8 yrs old) to chart the moon's phases for our homeschool lessons. He excitedly drew the approximate crescent shape of the moon each night, for about 4 or 5 nights, then it just seemed to disappear for quite a while. How long, I don't remember, but long enough that we lost interest and gave up, but I've often wondered where it went and how we could have missed it. Could you explain when a good time would be to chart the moon through its phases? (and any "how to" would be helpful too!)"
Sharie, you and your son made a very important observation of the Moon's cycle -- that the Moon is sometimes visible in the evenings after sunset, and other times is not. In those times when the Moon cannot be seen in the evening after sunset, it can be seen in the morning sky, around sunrise. The fact is, for most of the lunar month, the Moon can also be seen during the day! This is because the Moon rises and sets, just like the Sun and stars. And for most of the month, it rises and sets in daylight.
The Waxing and Waning of the Moon
The phases of the Moon are shown on most every wall calendar. The "New Moon" occurs when the Moon is aligned with the Sun, and therefore cannot be seen in the Sun's bright glare. After the New Moon, the Moon is said to be "increasing" or "waxing," and the waxing phases of the Moon are visible in the evening sky after sunset. The young waxing Moon starts out as a skinny crescent. Each night, it grows thicker in phase as it moves farther across the sky from the sunset.
After two weeks, the Moon has increased to a Full Moon. After that, the Moon begins to decrease again in phase, as the Moon's orbit carries it back to toward alignment with the Sun. These are the "waning" or decreasing phases. A waning Moon can't be seen in the evening, but it can be seen in the morning around sunrise. So Sharie, it sounds like your son's problem was that he was only looking in the evening sky. He was able to follow the Moon in its waxing phases, but after it was waning, it seemed to disappear.
The Rising and Setting of the Moon
In order to better grasp these ideas, consider this: due to the Earth's rotation, the Moon also rises and sets each day, just like the Sun and stars. The phases of the Moon can also be seen by rising and setting times of the Moon, which are different each day.
The quarter phases of the Moon are shown on most every wall calendar. The New Moon is usually shown as a solid black circle. When the Moon is New, it is very near the Sun in the sky. So the New Moon rises and sets close to the same time as the Sun, and can't be seen in the sky, since it is lost in the Sun's bright glare.
But as the Moon moves in its orbit around the Earth, it will move progessively toward the East, away from the Sun in the days after the New. On the day after the New Moon, the Moon will rise about 48 minutes after the Sun. On the next day, it will rise about 48 minutes after that. And each day thereafter, it will rise about another 48 minutes later than the day before.
About three days after the New Moon, the Moon is far enough away from the Sun to be easily seen in evening sky after sunset. But the Moon actually rises in the blue skies of morning, about 2 1/2 hours after the Sun. If you had a cloudless sky, a sharp eye, and knew where to look, you could easily spot the crescent Moon in the daytime. You could see the slim crescent rising in the East in the morning and crossing the blue sky over the span of the day. And after crossing the sky all day, the waxing crescent Moon arrives in the western sky by the evening twilight, only to set two and half hours after the Sun.
Each following day, the Moon rises 48 minutes later than the day before. And as the Moon moves farther away from the Sun, it increases or "waxes" in phase. After about a week, the Moon is at "First Quarter." The Moon is now a half-moon, and is usually shown on wall calendars as a little circle, white on the right side and black on the left side. This is how the Moon looks from northern hemisphere, but it looks just the opposite from the southern hemisphere!
By the First Quarter, the Moon is a half-moon and rises about six hours after the Sun. So if the Sun rises at 6:00 AM, the First Quarter Moon rises around Noon. During the afternoon, you can see the half-moon climbing higher in the eastern part of the sky. And the Moon reaches its own "noon" at its highest part of the sky around the time when the Sun sets. The First Quarter Moon goes down in darkness and finally sets around Midnight.
(Nota Bene -- These rising and setting times as stated here only represent seasonal and global averages. Actual times can vary considerably with the date of the of the year and your location on the Earth's globe. But the weather section of your local paper should have your local rising and setting times for at least the Sun and Moon, and maybe also the planets.)
After the First Quarter, the Moon is in its "gibbous" phases, looking fatter than a half-moon but not yet full. On these nights, the Moon rises later and later. Before the sunset, we can often easily see the waxing gibbous Moon coming up in the eastern sky.
Finally, two weeks after the New Moon, it is the night of the Full Moon. The Full Moon is shown on wall calendars as a solid white circle. At the Full Moon, the lunar month is now half over. The Moon now rises on the opposite end of the sky from the setting Sun, about 12 hours after the Sun. The Full Moon reaches its "noon" in the sky around midnight, and can be seen going down in the morning twilight before the sunrise.
But here's the tricky part -- on the next night after the full, the Moon rises about 48 minutes *after* the sunset! And the next night, the Moon rises another 48 minutes later, and so on each night. After only a few days after the Full Moon, the waning Moon doesn't rise until after most kid's bedtimes! But it can be an awesome sight to see a huge, orange, waning gibbous Moon rising large in the nighttime hours.
The waning Moon rises after the Sun sets, and so it crosses the sky over the span of the night, but it still has not set by morning. So if your family is up early around the time of sunrise (unlike us!) you can still see the waning Moon in the western sky before it sets. And since it rises later and later after sunset each night, it's higher and higher in the morning sky each passing day, and sets later and later after the Sun has risen.
The Last Quarter Moon, which is a waning half-moon, is shown on wall calendars as a circle, black on the right and white on the left. The Moon reaches this phase after three weeks, and the lunar month is now three-fourths over. Again, this is how it appears from the northern hemisphere, but this sight is actually reversed in the southern hemisphere. In either hemisphere, the Last Quarter Moon rises around Midnight, about 18 hours after the Sun. And it is at mid-sky by sunrise, and sets around Noon.
In the following week, the Moon is a waning crescent. Since it is now more than three weeks into lunar month, the Moon is now an "old moon," rising in the wee hours before sunrise. So the waning crescent Moon can be seen over the eastern horizon in the morning twilight, a couple hours after rising. If you can pick a waning crescent out of the daytime sky, you might see it setting in the late afternoon before the sunset.
The old waning Moon drops closer to the sunrise each morning, until finally, it is the next New Moon. The Moon catches up to the Sun to complete the cycle of its orbit, and rises and sets once again with the Sun.
" Praise ye the LORD, Praise ye the LORD from the heavens: praise him in the heights.... Praise ye him, sun and moon: praise him all ye stars of light."
-- Psalm 148: 1,3
Friends, I try to write this stuff clearly. But you can read about this stuff over and over til the cows come home, but it really only starts to make sense when you go out and observe for yourself. If your family makes a determined effort to observe the Moon on each clear night or morning for a month straight, you can begin to see the pattern of the Moon's cycle, and it starts to make sense. And after a couple months, the cycle becomes more and more clear.
The best part is, once you really understand the Moon's cycle, you'll never forget it. Following the Moon will become a part of life, just as it was with the farmers, sailors and other common folk down through history, in the glory days of Classical Astronomy.
For a different look at this topic, here is another web page discussing the Moon's phases posted at the Classical Astronomy site.
To observe how the Moon's phases relate to its rising and setting times, consult the weather section of your local paper, where you should be able to find your local rising and setting times for the Sun and Moon. Have your homeschool scholars read the weather page each day for a month and keep a journal tracking the rising and setting times for the Sun and Moon. If you don't get the paper, you can use the Almanac on the home page at http://skyandtelescope.com .
In your family dictionary, look up the words "waxing" and "waning." Have your homeschool scholars copy these definitions into their journals. Have them explain the best times of day for sighting the Moon when it is in these phases.
Following Sharie's suggestion, have your scholars draw pictures of the Moon's phases in their journals as seen on each clear night. To get a nice, uniform circle, feel free to draw circles with a template, and just draw the curve of the Moon's shadow edge each night, and color in the dark side of the Moon.
For each picture, write the date and record the rising and setting times from the newspaper. Indicate the phase of the Moon, i.e. waxing or waning, crescent, half-moon, gibbous or full. Also, indicate the nights of the Moon's quarters -- New Moon, First Quarter, Full Moon, Last Quarter. If you don't have a wall calendar handy, check out the Current Moon Phase graphic each day at the Classical Astronomy home page -- http://web.archive.org/web/20040810020328/http://www.classicalastronomy.com/ .
And most importantly, have fun with this! Don't do all these activities if it looks like too much work for your scholars! Or maybe do some this month and some others next month. But don't wait too long since we hope to expand on this theme in a future Update!
In any case, please do try to at least observe the Moon's changing phases each night, and sketch the phases. In our homeschooling, we are firm believers in having the kids draw pictures of natural objects, such as animals and maps and other natural objects.
I've observed in my own illustrating that drawing forces you to look closely at an object, and observe the proportions and relationships of the various parts in a whole. In fact, the essence of being a good illustrator includes properly depicting perspective and anatomy. And it was by drawing that I taught myself Classical Astronomy many years ago.
Galileo's revolutionary works included his sketches of the Moon's face, the shape of Saturn and the moons of Jupiter. Our young scholars can learn much about their world by imitating Galileo and other "Renaissance Men" such as Leonardo.
* Moon Phase Challenge -- Addendum *
" And it shall come to pass, that from one New Moon to another, and from one Sabbath to another, shall all flesh come to worship before me, saith the LORD." -- Isaiah 66:23
We received an email from Tammy P. in California who wrote:
" We took up your challenge at the new moon last month and have been keeping a journal of rising and setting of the moon. We (myself and 2 daughters) wonder why the moon did not "set" on April 24 and did not "rise" on May 8? We have been enjoying searching for the moon and watching its path in the sky."
Thanks to Tammy and everyone else who "took the Moon Phase Challenge" this past month! We hope these observations have helped your family understand and appreciate the Moon's cycle. Tammy has made an excellent observation about the risings and settings of the Moon. It never occurred to me to alert everyone to this, so many thanks for pointing it out!
Since the Moon rises and sets at different times each day, there are going to be times when it rises and sets close to Midnight. And around these times, it can happen than the Moon rises on one particular day, and sets after Midnight on the next day. That's what happened on these dates, at that particular location. But since these times vary with location, it's impossible to give specific days that would apply to everyone.
According to my SkyGlobe software program, in Los Angeles, California, USA, on April 24, the Moon rose at about 9:28 AM. The Moon set after Midnight at 12:33 AM on April 25. And on May 7, the Moon rose at 11:40 PM, before Midnight, and set at about 9:10 AM on the morning of May 8. So the Moon didn't "set" on April 24, nor did it "rise" on May 8.
So even though the calendar dates might be different, each of these risings and settings represent a "lunar day," that is, one complete interval of the Moon above the horizon. But the papers publish only the rising and setting times of the Moon that occur on that particular date. This is misleading from the standpoint of reckoning the "lunar day" since the "moonset" of the previous "lunar day" can be shown earlier than the "moonrise" of the next "lunar day."
So here's how to interpret the data -- for a given date, if the setting of the Moon is earlier in the day than the rising, that particular moonset accompanies the moonrise of the previous date. And for the rising of the Moon later in the day, find the setting for that "lunar day" in the next day's paper.
Sorry that I didn't realize to tell you that when I was writing the Update. This might make the "Moon Phase Challenge" a bit more complicated. But these things do take time and repeated observation to fully grasp. As your family begins to observe the Moon's cycle, this will make more sense and be easier to understand. It sure gave me fits when I was first learning this stuff! But learning the natural, God-given techniques of celestial timekeeping has made me realize how arbitrary and artificial our "clock time" is compared with the cycles of the natural timekeepers that the LORD has placed in the sky.
more information about topics from Classical Astronomy,
please check out Signs & Seasons,
a homeschool astronomy curriculum!