Differenza bejn ir-reviżjonijiet ta' "Fażijiet lunari"

 
Il-qamar jagħmel dawra sħiħa madwar id-dinja f'27 jum, 7 sigħat, 43 minuta u 11-il sekonda (xhar siderali). Waqt li x-xhar lunari jew sinodiku (jiġifieri l-perjodu bejn żewġ qmura mitlufin) idum 29 jum, 12-il siegħa, 44 minuta u 3 sekondi. Id-differenza ġejja mill-fatt li sistema Dinja-Qamar qiegħda torbita madwar ix-xemx fl-istess ħin li l-Qamar qiegħed jorbita madwar id-Dinja.
 
Iż-żmien bejn żewġ fażijiet hu varjabbli ħafna billi l-orbita tal-Qamar hi elittika u suġġetta għal bosta perturbazzjonijiet perjodiċi, li jbiddlu l-veloċità tal-Qamar. Meta l-Qamar ikun iżjed qrib lejn id-Dinja, jiġri iżjed; meta jkun iżjed 'l bogħod, jimxi iżjed bilmod. L-orbita tad-Dinja madwar ix-Xemx hi wkoll elittika, u għalhekk il-veloċità tad-Dinja tvarja wkoll u jaffettwa wkoll il-fażijiet tal-Qamar.
 
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The actual time between two syzygies or two phases is quite variable because the orbit of the Moon is elliptic and subject to various periodic perturbations, which change the velocity of the Moon. When the moon is closer to the earth, it moves faster; when it is farther, it moves slower. The orbit of the Earth around the Sun is also elliptic, so the speed of the Earth also varies, which also affects the phases of the Moon.
 
It might be 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 one might expect the Earth's shadow to fall on the Moon, causing a lunar eclipse. Solar and lunar eclipses are not observed every month because the plane of the Moon's orbit around the Earth is tilted by about five degrees with respect to the plane of Earth's orbit around the Sun (the plane of the ecliptic). 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 very near 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 four and seven eclipses in a calendar year. Most of these are quite insignificant; major eclipses of the Moon or Sun are rare.