Fażijiet lunari: Differenza bejn il-verżjonijiet
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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. |
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. |
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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. |
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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. |
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. |
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Reviżjoni ta' 16:49, 18 Jannar 2013
Il-fażijiet lunari jew fażijiet qamrin jiddeskrivu kif jidher il-Qamar matul il-moviment tiegħu. Kif jidher jiddependi mill-orjentament tiegħu relattiv għax-Xemx. Il-fażijiet lunari jirrepetu ruħhom f'intervall ta' żmien imsejjaħ "xhar sinodiku", ta' madwar 29 jum u nofs. Ix-xhar tal-kalendarju tagħna ġej minnu. Il-fażijiet lunari ġejjin mit-tidwir tal-Qamar u t-tibdil ċikliku li jiġi minnu tal-pożizzjoni relattiva għad-Dinja u x-Xemx.
Il-qmura
Il-qmura jew fażijiet jirrappreżentaw il-parti tal-Qamar imdawla mix-Xemx.
Hemm erba' pożizzjonijiet fundamentali, rappreżentati fil-figura ta' taħt bit-titli ta' fuq, u erba' intermedji:
- Qamar mitluf
- Qamar ġdid
- L-ewwel kwart
- Qamar mużqaq
- Qamar kwinta jew Qamar mimli
- Qamar muqsar
- L-aħħar kwart
- Qamar xiħ
It-terminu "kwart" jirreferi għall-pożizzjoni tal-Qamar fl-orbita madwar id-Dinja. Meta jkun f'waħda minn dawn iż-żewġ pożizzjonijiet mid-dinja jidher biss nofs emisferu.
It-tlugħ u l-inżul tal-qamar
- Meta jkun hemm Qamar mitluf, il-Qamar ikun qiegħed bejn id-Dinja u x-Xemx: jitla' filgħodu u jinżel fil-għaxija.
- Fil-kwarti (l-ewwel kwart u t-tieni kwart), il-linji li jgħaqqdu d-Dinja mal-Qamar u l-Qamar max-Xemx jagħmlu angolu ta' 90°. Fl-ewwel kwart il-Qamar jitla' f'nofsinhar u jinżel f'nofsillejl, fl-aħħar kwart jitla' f'mofsillejl u jinżel f'nofsinhar.
- Meta l-Qamar ikun mimli id-Dinja tkun bejn ix-Xemx u l-Qamar.
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.