PRETSESSIYa

PRETSESSIYa (az lotini praccessio — peshopesh meravam), harakati mehvari charkhzanii jismi sakht, az chumla giroskopro guyand, ki hangomi on sathi doiravii mahdud kashida meshavad. Dar ayni zamon mehvari mazkur dar Lappishi nutatsioni (nig. Nutatsiya) buda metavonad.

Dar astronomiya Pretsessiya gufta, harakati susti mehvari charkhzanii Zaminro az rui konusi doiravi menomand. Dar natijai harakati hamvorii ekvator nuqtahoi etidol qad-qadi khati ekliptika az tarafi sharq ba sui garb, yane ba muqobili harakati zohirii solonai Oftob so­le ba andozai 50,3″ mekuchad. Az in sabab soli tropiki (fosilae, ki Oftob dar muddati on az nuqtai etidoli bahori du marotiba pay dar pay meguzarad), ki bo tagyir yoftani faslhoi sol dar Za­min aloqamand ast, az soli sitoravi (fosilae, ki dar muddati on Zamin atrofi Oftobro purra davr mezanad) 20 daqiqa 24 soniya kutoh meboshad.

Zimin Pretsessiya koordinatahoi eklipti­ki va ekvatori tagyir meyobad (nig. Koordinatahoi osmoni). Tulhoi sitoragon, ki nisbat ba nuqtai etidoli bahori hisob karda meshavand, sole ba andozai 50,3″ meafzoyand, vale arzho dar in muddat chandon ziyod tagyir nameyoband. Tului mustaqim va mayli sitoragon az rui qonuniyathoi murakkabtar tagyir meyoband. Dar natijai Pretsessiya manzarai davrzanii shaboruzii oson sust tagiir meyobad: 4600 sol qabl az in qutbi dunyo dar nazdikii sitorai Tuban (a Tinnin) voqe bud, holo on dar nazdikii Si­torai Qutb (a Dubbi Akbar) joygir ast. Bad az 12000 sol sitorai Nasri Voqe (a Sanj) «sitorai qutb» khohad shud.

Agar Zamin khud kurai muntazam mebudu dar hamai mavzehoyash zichii yakkhela medosht, quvvai kashishi Oftob va Moh dar har yak nuqtai on niz yakkhela mebud va dar natija, charkhzanii Zamin hej tagyir nameyoft. Dar asl kurai Zamin dar qutbho nisbat ba ekvator pachaq ast. Az in sabab ham quvvai kashishi Of­tob va Moh dar ekvator nisbat ba qutbho ziyodtar meboshad. Tasiri quvvai kashishi Moh bo charkhzanii Zamin yakjoya shuda, hodisai Pretsessiyaro ba amal meovarad. Pretsessiyae, ki dar natijai lagzishi nuqtahoi etidoli az tasiri quvvahoi kashishi Oftobu Moh ba amal meoyand, Pretsessiyai Shamsivu Qamari nom dorad. Qad-qadi ekvator az garb ba sharq joy ivaz kardani nuqtahoi etidoli bahori, ki dar natijai Pretsessiya ba amal meoyad, Pretsessiyai sayyoraho nomida mesha­vad. Harakati jamuljami nuqtai tobu Moh ba amal meoyand, Pretsessiyai Shamsivu Qamari va Pretsessiyai sayyoraho tash­kil yoftaand, Pretsessiyai umumi nom dorad.

Hodisai Pretsessiyaro dar asri 2 to melod Gip­parkh kashf kard. Vay ziji 1022 sitoraro bo ziji Tikhomaris, ki 150 sol pesh az u tartib doda shuda bud, muqoisa karda, ziyod shudani tuli hamai sitoragonro oshkor kard va in hodisaro Pretsessiya nomid. Pretsessiyaro bori avval I. Nyuton az nuqtai nazari ilmi mekhanika sharh dod (1686). Nazariyai ilmii Pretsessiyaro dar asri 18 J. Dalamber, P. Laplas va L. Eyler ba vujud ovardand.            N. Abdullaev.