month

1. one of the twelve divisions (calendar months) of the calendar year

2. the period of time (tropical month) taken by the moon to return to the same longitude after one complete revolution around the earth; 27.321 58 days (approximately 27 days, 7 hours, 43 minutes, 4.5 seconds)

3. the period of time (sidereal month) taken by the moon to make one complete revolution around the earth, measured between two successive conjunctions with a distant star; 27.321 66 days (approximately 27 days, 7 hours, 43 minutes, 11 seconds)

4. the period of time (lunar or synodic month) taken by the moon to make one complete revolution around the earth, measured between two successive new moons; 29.530 59 days (approximately 29 days, 12 hours, 44 minutes, 3 seconds)

Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005

Month

month

The period of the Moon's revolution around the Earth with reference to some specified point in the sky (see table). The differences in the monthly periods result from the complicated motion of the moon.

Collins Dictionary of Astronomy © Market House Books Ltd, 2006

month

[mənth]

(astronomy)

The period of the revolution of the moon around the earth (sidereal month).

The period of the phases of the moon (synodic month).

The month of the calendar (calendar month).

The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.

Month

an interval of time nearly equal to the period of revolution of the moon about the earth. Different types of months are distinguished (see Table 1 and Figure 1). These include (1) the synodic month, which is the period of the sequence of the lunar phases (it serves as the basis for lunar calendars);

Table 1. Length of various types of months
Type of month	Mean solar days	Mean solar time
Synodic .....	29.530588	29 days	12 hr	44 min	3 sec
Sidereal .....	27.321661	27 days	7 hr	43 min	12 sec
Tropical .....	27.321582	27 days	7 hr	43 min	4 sec
Anomalistic .....	27.554550	27 days	13 hr	18 min	33 sec
Nodical .....	27.212220	27 days	5 hr	5 min	36 sec

(2) the sidereal month, during which the moon performs a complete revolution about the earth and returns to its original position relative to the stars; (3) the tropical month, which is the period during which the moon returns to a given longitude; (4) the anomalistic month, which is the interval of time between successive passages of the moon through the perigee; and (5) the nodical month, which is the period of time between successive passages of the moon through the same node of its orbit (this concept is important for the theory of eclipses). In the Gregorian calendar, the year is divided into 12 months, each month containing from 28 to 31 days; this calendar does not agree with the lunar phases.

Figure 1. Difference between synodic and sidereal months. (1) and (3) are the relative posiositions of the sun, earth, and moon at which a full moonon occurs (a time interval of oneone synodic month); (2) is the position of the moon after a complete revolution about the earth (a time interval of one siderealreal month).

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References in classic literature

He regained Tripoli toward the close of August, 1855, and arrived in London on the 6th of September, the only survivor of his party.

In 1859, in the month of August, the young traveller, Roscher, from Hamburg, set out with a caravan of Arab merchants, reached Lake Nyassa, and was there assassinated while he slept.

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About the beginning of August, as I said, I had finished my bower, and began to enjoy myself.

In this season I was much surprised with the increase of my family; I had been concerned for the loss of one of my cats, who ran away from me, or, as I thought, had been dead, and I heard no more tidings of her till, to my astonishment, she came home about the end of August with three kittens.

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In the course of his march, therefore, he secretly detached a small party of trappers, to make their way to those hunting grounds, while he continued on with the main body; appointing a rendezvous, at the next full moon, about the 28th of August, at a place called the Medicine Lodge.

On reaching the second chain, called the Bighorn Mountains, where the river forced its impetuous way through a precipitous defile, with cascades and rapids, the travellers were obliged to leave its banks, and traverse the mountains by a rugged and frightful route, emphatically called the "Bad Pass." Descending the opposite side, they again made for the river banks; and about the middle of August, reached the point below the rapids where the river becomes navigable for boats.

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9 August.--The sequel to the strange arrival of the derelict in the storm last night is almost more startling than the thing itself.

1 August.--Two days of fog, and not a sail sighted.

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M'Kenzie on the 17th of August, the height of which rendered it a landmark over a vast extent of country.

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"On the 11th of August he sold a pair of the fine horses-- said he'd often thought a pair was better than four, to go over the rough mountain roads with where a body had to be careful about his driving--and there wasn't so much of his claim but he could lug the money home with a pair easy enough.

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Anne spent a fortnight of halcyon days at Echo Lodge in the golden prime of August. While there she incidentally contrived to hurry Ludovic Speed in his leisurely courting of Theodora Dix, as related duly in another chronicle of her history.[1] Arnold Sherman, an elderly friend of the Irvings, was there at the same time, and added not a little to the general pleasantness of life.

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On the twenty-eighth of August, at the hour of midnight, and if the moon is shining--the moon must be shining--a spirit that has haunted these shores for ages rises up from the Gulf.

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