Approximately how long does it take to cycle from one new moon to the next new moon?

Answer 1

28 days

Answer 2

Twenty-nine days, 12 hours, 44 minutes, and 2.78 seconds, according to "The 2007 Time Almanac" page 284. The period of rotation of the moon is equal to its period of revolution around the earth, which is 27 day, 7 hours, 43 minutes and 11.47 seconds, the Almanac says, explaining that the delay of two days is because the earth is moving around the sun, so that the moon needs two extra days to reach a spot in its orbit where no part is illuminated by the sun, as seen from earth.

Answer 3

This is called a synodic month. The average length is 29.530588853 + 0.000000002162*y days, where y = (days since noon 1 Jan 2000) / 365.25.

That is the same as 29 d 12 h 44 min 2.8 s, at the epoch J2000, plus 0.019 seconds per century.

The actual time for any particular cycle varies around this average, by about plus or minus 6.72 hours.

Answer 4

Lunar phase refers to the appearance of the illuminated portion of the Moon as seen by an observer, usually on Earth. The lunar phases vary cyclically as the Moon orbits the Earth, according to the changing geometry of the Earth, Moon, and Sun. One half of the lunar surface is always illuminated by the Sun, and is hence bright, but the portion of the illuminated hemisphere that is visible to an observer can vary from 100% (full moon) to 0% (new moon). The boundary between the illuminated and unilluminated hemispheres is called the terminator.




Contents [hide]
1 Overview
2 Names of lunar phases
3 Calendar
4 See also
5 External links



[edit] Overview

The lunar phase depends on the Moon's position in orbit around the Earth, and the Earth's position in orbit around the sun. This diagram looks down on Earth from the north. Earth's rotation and the Moon's orbit are both counter-clockwise here. Sunlight is coming in from the right, as indicated by the yellow arrows. From this diagram, we can see, for example, that the full moon will always rise at sunset, and that the waning crescent moon is high overhead around 9:00 AM local time.Lunar phases are the result of our eyes seeing the illuminated half of the Moon from different viewing geometries: they are not caused by shadows of the Earth on the Moon that occur during a lunar eclipse. The Moon exhibits different phases as the relative geometry of the Sun, Earth and Moon change, appearing as a full moon when the Sun and Moon are on opposite sides of the Earth, and becoming invisible as a new moon (also named dark moon) when they are on the same side. The phases of full moon and new moon are examples of syzygies, which occur when the Earth, Moon and Sun lie (approximately) in a straight line. The time between two full moons (or between successive occurrences of the same phase) is about 29.53 days (29 days, 12 hours, 44 minutes) on average. This synodic month is longer than the time it takes the Moon to make one orbit about the Earth with respect to the fixed stars (the sidereal month), which is about 27.32 days. This difference is caused by the fact that the Earth-Moon system is orbiting about the Sun at the same time the Moon is orbiting about the Earth. The actual time between two syzygies is variable because the orbit of the Moon is elliptic and subject to various periodic perturbations, which change the velocity of the Moon.

It might be naively expected that once every month when the Moon passes between Earth and the Sun during a new moon, its shadow would fall on Earth causing a solar eclipse. Likewise, during every full moon, we might expect the Earth's shadow to fall on the Moon, causing a lunar eclipse. We do not observe a solar and lunar eclipse every month because the plane of the Moon's orbit around the Earth is tilted by about 5 degrees with respect to the plane of Earth's orbit around the Sun. Thus, when new and full moons occur, the Moon usually lies to the north or south of a direct line through the Earth and Sun. Although an eclipse can only occur when the Moon is either new or full, it must also be positioned at (or very nearly at) the intersection of Earth's orbit plane about the Sun and the Moon's orbit plane about the Earth (that is, at one of its nodes). This happens about twice per year, and so there are between 4 and 7 eclipses in a calendar year. Most of these are quite insignificant; major eclipses of the Moon or Sun are rather rare and newsworthy events.


[edit] Names of lunar phases

Phases of the Moon.The phases of the Moon have been given the following names, which are listed in sequential order:

Dark Moon - Not visible
New Moon - Not visible, or traditionally, the first visible crescent of the Moon
Waxing Crescent Moon - Right 1-49% visible
First Quarter Moon - Right 50% visible
Waxing gibbous Moon - Right 51-99% visible
Full Moon - Fully visible
Waning gibbous Moon - Left 51-99% visible
Third Quarter Moon - Left 50% visible
Waning Crescent Moon - Left 1-49% visible
New Moon - Not visible

Gibbous (red) and crescent (blue) shapes.References to left and right are for observers in the northern hemisphere of Earth only; in the southern hemisphere, these should be reversed. For example, a "waxing crescent moon" would have the left portion illuminated in the southern hemisphere.

When the Sun and Moon are aligned on the side of the Earth, the Moon is "new", and is not illuminated by the Sun. As the Moon waxes (the amount of illuminated surface as seen from Earth is increasing), the lunar phases progress from new moon, crescent moon, first-quarter moon, gibbous moon and full moon phases, before returning through the gibbous moon, third-quarter moon, crescent moon and new moon phases. The terms old moon and new moon are interchangeable, although new moon is more common. Half moon is often used to mean the first- and third-quarter moons.


Animation of the Moon as it cycles through its phases. The apparent wobbling of the Moon is known as libration.When a sphere is illuminated on one hemisphere and viewed from a different angle, the portion of the illuminated area that is visible will have a two-dimensional shape defined by the intersection of an ellipse and circle. If the half-ellipse is convex with respect to the half-circle, then the shape will be gibbous (bulging outwards), whereas if the half-ellipse is concave with respect to the half-circle, then the shape will be a crescent.

In the northern hemisphere, if the left side of the Moon is dark then the light part is growing, and the Moon is referred to as waxing (moving towards a full moon). If the right side of the Moon is dark then the light part is shrinking, and the Moon is referred to as waning (moving towards a new moon). Assuming that one is in the northern hemisphere, the right portion of the Moon is the part that is always growing. The acronym mnemonic "DOC" represents this: "D" is the waxing moon; "O" the full moon; and "C" the waning moon. (One phrase that can be used to remember this is "Dog comes; Cat goes".) In the Southern hemisphere, this order is reversed, and the mnemonic is "COD".





[edit] Calendar
Image:Moon phase calendar 2007.pngThe average calendrical month, which is 1/12 of a year, is about 30.4 days, while the Moon's phase (synodic) cycle repeats every 29.53 days. Therefore the timing of the Moon's phases shifts by an average of about one day for each successive month. If you photographed the Moon's phase every day for a month, starting in the evening after sunset, and repeating approximately 25 minutes later each successive day, ending in the morning before sunrise, you could create a composite image like the example calendar below from May 8, 2005 to June 6, 2005. Note that there is no picture on May 20 since a picture would be taken before midnight on May 19, and after midnight on May 21. For a similar reason, if you look at a calendar listing moon rise or set times, there will be days where the moon never rises or sets.

Answer 5

28 days.

Answer 6

Some variance does come into effect, but the average is 29.5 days.

Answer 7

29,5 days. Not approximately. Exactly.

Answer 8

29.53 days