How long does each phase of the moon last?

Question

How long do each of the 8 phases individually last?

Answer 1

Now that you have a thorough understanding of the Earth-Moon system it is time to introduce the Sun.
The phases of the Moon are caused by the positions of the Earth, Moon and Sun. The tides are affected by these positions too.

You'll recall that the Earth revolves around the Sun taking an entire year to complete one revolution. We have our daily night and day because the Earth rotates - one rotation taking 24 hours. We see the night sky when our part of the Earth faces away from the Sun.
Now, let's add the Moon into this. The Moon produces no light of its own. It merely reflects the sunlight. Therefore, at any one time the Moon (like the Earth) has a night side and a day side that depends upon the position of the Sun. We can see the Moon only from the Earth (assuming you are not a space traveler ) and as the Moon orbits the Earth its position with respect to the Sun changes. That is what causes the various phases of the Moon.



Let's look at the phases in some detail. In the drawings below assume that the Sun is shining from "above" (the top of your screen) as indicated by the yellow rays of light. Note that the Moon orbits the earth counterclockwise (anticlockwise). That's also the same direction as the Earth's spin and the same direction as the Earth's orbit.

As you study these images, imagine how the Moon would look from some point on Earth. Would it be visible at all? If it was visible, what parts of it would be sunlit? How would the Moon appear to move through the sky from hour to hour or from day to day? These are not trivial questions. Take your time and think about these questions as we go through this section.

The New Moon occurs when the Moon is directly on the Sun side of the Earth, or to put that another way, the Moon is "new" when it is between the Earth and the Sun.
The New Moon rises and sets along with the Sun at about the same time. Since the New Moon has its shadowed face to us we don't see the New Moon very well and for all practical purposes the New Moon is "invisible". It is interesting to note that the New Moon's far side (the "dark side") is fully in the sunlight!

Refer to the link for further reading

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Hi! Thanks for calling Dr. Marc at The Space Place to hear what I'm thinking about this March. Our friends at the Virginia Living Museum in Newport News, Virginia, ask "how long does each phase of the Moon last?"
Well, first let's think about why it is the Moon has phases.


What people sometimes call "moonlight" is really sunlight reflecting off the Moon's surface. The Moon itself puts out no light at all. It takes about four weeks for the Moon to orbit once around Earth. During this time, the Moon's position relative to Earth and the Sun is constantly changing. During part of its journey, the Moon is between Earth and the Sun. Then, a few days later, it is off to one side. Still later, the Moon moves around so that Earth is between it and the Sun. And so on.
Try this little demonstration. You will need a lamp and a small ball (like a tennis ball or a softball). If the lamp has a shade, take it off. Pretend the lamp is the Sun, the ball is the Moon, and your head is Earth. Darken the room except for the lamp.

Now, hold the ball straight out in front of you. Stand facing the lamp. The ball will appear dark because the lighted side of the ball is facing away from you. This position represents the New Moon, dark and about to be born. Now, turn just a little tiny bit to your left, still holding the ball straight out. You will see only a thin lighted crescent on the right side of the ball. Now turn to the left a little more until the light is on your right. You will see half the lighted side of the ball. This position represents the First Quarter phase of the Moon. Now turn to the left again, so the lamp is behind you. (If the ball is directly in the shadow of your head, raise the ball up a little higher.) You will see the entire lighted side of the ball. Now you are looking at the Full Moon. Now turn again so the lamp is on your left. Now you are looking at the Last Quarter phase.
The Moon's orbit actually dips a little bit above and below an imaginary line drawn between Earth and the Sun. That is why Earth seldom blocks the Sunlight from reflecting off the full Moon. Once in a while, though, Earth does get directly in the way, and we have the exciting event called a lunar eclipse.

This month, go outside each day or evening and observe the Moon moving through its phases. At night, look carefully, especially when the Moon is just a crescent, and find the dark part of the Moon. We can see the dark part because it reflects Earth light-that is, Sunlight reflected from Earth.

So, how long does each phase of the Moon last? Well, the phases are just names we give to certain points along the Moon's smooth path around Earth. Technically, each phase, just like the one called a New Moon, when the Moon is exactly between Earth and the Sun, lasts only a brief instant. But to our eyes, a New Moon can last for a few days, representing the time that the Moon appears in the sky too near the Sun's position for us to see it at all. The time it takes the Moon to go through all its phases is about a month, and that was so important to our ancestors that they created the period of time we call a month. Maybe you've even noticed that the word month is like the word moon.

It isn't just the Moon that appears to have phases. The planets also have phases. For example, the orbit of Venus is inside the orbit of Earth. When Venus is in the part of its orbit between Earth and the Sun, we can't even see it, because its sunlit side will be away from us. This position is similar to the New Moon phase. As Venus progresses around the Sun, more and more of its illuminated side is visible to us on Earth. When Venus is on the far side of the Sun, we will see its Full Phase. At this time, we will see Venus only around sunset or sunrise, when the sky is just dark enough to see it even though Venus appears in the sky near the Sun.

Refer to the link for further reading

Answer 2

That can't really be answered because phases are exactly that. They gradually change from one to another. There are certain points which are significant in our perception of the moon's synodic period: new moon, first quarter moon, full moon, and last quarter moon. But each of these occurs at a particular point in time, not over a period. It's like asking how long noon lasts, or midnight. See? Now if you are wondering if the full moon lasts long enough to include certain events that you, or someone, believes are attributable to the full moon, then forget about it. The period over which one would call the moon full is arbitrary, as it is only *mostly* full for all but one fraction of a second. Also, the moon has no effect on us. Of note: some of the early "research" in the seventies which supposedly showed a connection between the full moon and human affairs actually counted data from as far as five days away from the full moon on either side. This is more than 1/3 of the lunar cycle, but we are to believe the data was taken from only 1/28th of the cycle. This created false correlations.

Answer 3

Contrary to the answers that suggest dividing the number of phases into the number of days to complete the cycle, they are different.

Technically speaking full moon, new moon, first quarter and last quarter are very short, lasting only an instant each. Full moon is when the Moon is exactly 12hrs of right ascension from the sun in the sky, and therefore the full disc appears illuminated from Earth. New Moon is when the moon is exactly 0hrs of right ascension, hence the illuminated side is turned away from us. First and last quarter are 6 and 18hrs of right ascension respectively, with the terminator appearing as a straight line dividing the disc in half.

(In visual terms, however, it is often easier to consider these phases lasting one day or night each, as the unaided eye won't detect much difference between a rising and setting full Moon or quarter phase, and the new Moon is invisible because the illuminated side faces away from us.)

The waxing crescent phase lasts between new Moon and first quarter, the waxing gibbous phase lasts between first quarter and full Moon, the waning gibbous between full Moon and last quarter, and the waning crescent between last quarter and new Moon.

In very rough terms, then, the crescent and gibbous phases last about a week, while the new, full and quarter phases occur at specific times.

Answer 4

There are normally considered to be four phases
New, First Quarter, Full, Last Quarter,
each of which lasts a week. It is where we get the week from (yes it existed at the time the Bible was created and 7 days were assigned to the Creation)
If you use these terms
New Moon
Waxing Crescent
First Quarter
Waxing Gibbous
Full Moon
Waning Gibbous
Last Quarter
Waning
from this site
http://www.calculatorcat.com/moon_phases/moon_phases.phtml
Then obviously each one lasts 3.5 days.

Answer 5

The phases of the moon are a continuum. That means that the phases smoothly transition. From new to full moon, it is said to be waxing (increasing), and from full to new moon it is said to be waning(decreasing). There is no distinct boundary from one phase to the next. It takes about 29 days for one complete cycle.

Answer 6

28 days divided by 8 is....

Get a calculator.

Answer 7

is that the waxing .. something like that???... if thats what youre talking about.. well i think last 2 days...