ulka

aakaash ke ek bhaag mein ulka girne ka drushya; yeh drushya eksojar samay kabadhaakar liya gaya hai

aakaash mein kabhi-kabhi ek or se doosari or atyant veg se jaate hue athva pruthvi par girte hue jo pind dikhaai dete hain unhein ulka (meteor) aur saadhaaran bolachaal mein 'tootate hue taare' athva 'looka' kehte hain. ulkaaon ka jo ansh vaayumandal mein jalne se bachakar pruthvi tak pahuainchata hai use ulkaapind (meteorite) kehte hain. praay: pratyek raatri ko ulkaaeain anginat sankhya mein dekhi ja sakti hain, kintu inmein se pruthvi par girnevaale pindon ki sankhya atyant alp hoti hai. vaigyaanik drushti se inka mahatva bahut adhik hai kyonki ek to ye ati durlabh hote hain, doosare aakaash mein vichrate hue vibhinn grahon ityaadi ke sangathan aur sanrachana (strakchar) ke gyaan ke pratyaksh srot keval ye hi pind hain. inke adhyayan se hamein yeh bhi bodh hota hai ki bhoomandaleeya vaataavaran mein aakaash se aae hue padaarth par kya-kya pratikriyaaeain hoti hain. is prakaar ye pind brahmaandavidya aur bhoovijnyaaan ke beech sampark sthaapit karte hain.

anukram

sankshipt itihaas

yadyapi manushya in tootate hue taaron se atyant praacheen samay se parichit tha, tathaapi aadhunik vigyaan ke vikaasayug mein manushya ko yeh vishvaas karne mein bahut samay laga ki bhootal par paae gaye ye pind pruthvi par aakaash se aae hain. 18veen shataabdi ke uttaraardh mein di. trauyali naamak daarshanik ne Italy mein albaareto sthaan par gire hue ulkaapind ka varnan karte hue yeh vichaar prakat kiya ki vah khamandal se tootate hue taare ke roop mein aaya hoga, kintu kisi ne bhi ispar dhyaan naheen diya. san 1768 E. mein father baasile ne France mein loos naamak sthaan par ek ulkaapind ko pruthvi par aate hue svat: dekha. agale varsh usane peris ki vigyaan ki raayal academy ke adhiveshan mein is vruttaant par ek lekh padha. academy ne vruttaant par vishvaas na karte hue ghatna ki jaaainch karne ke liye ek aayog niyukt kiya jiske prativedan mein father baasile ke vruttaant ko bhramaatmak bataate hue yeh mantavya prakat kiya gaya ki bijli gir jaane se pind ka prushth kuchh is prakaar kaaainch sadrush ho gaya tha jisse baasile ko yeh bhram hua ki yeh pind pruthvi ka ansh naheen hain. tadanantar jarman daarshanik klaadani ne san 1794 E. mein saaibeeriya se praapt ek ulkaapind ka adhyayan karte hue yeh siddhaant prastaavit kiya ki ye pind khamandal ke pratinidhi hote hain. yadyapi is baar bhi yeh vichaar turant sveekaar naheen kiya gaya, fir bhi klaadani ko is prasang par dhyaan aakarshit karne ka shreya mila aur tab se vaigyaanik is vishay par adhik manoyog dene lage. san 1803 E. mein France mein la aigil sthaan par ulkaapindon ki ek bahut badi vrushti hui jismein anginat chhote-bade patthar gire aur unamein se praaya: do-teen hajaar ikatthe bhi kiye ja sake. vigyaan ki fraanseesi academy ne us vrushti ki poori chhaanabeen ki aur ant mein kisi ko bhi yeh sandeh naheen raha ki ulkaapind vastut: khamandal se hi pruthvi par aate hain.

vargeekaran

ulkaapindon ka mukhya vargeekaran unke sangathan ke aadhaar par kiya jaata hai. kuchh pind adhikaanshat: lohe, nikal ya mishradhaatuon se bane hote hain aur kuchh siliket khanijon se bane patthar sadrush hote hain. pehle vargavaalon ko dhaatvik aur doosare vargavaalon ko aashmik ulkaapind kehte hain. iske atirikt kuchh pindon mein dhaatvik aur aashmik padaarth praaya: samaan maatra mein paae jaate hain, unhein dhaatvaashmik ulkaapind kehte hain. vastut: poornataya dhaatvik aur poornataya aashmik ulkapindon ke beech sabhi prakaar ki ant:sth jaatiyon ke ulkaapind paae jaate hain jisse pindon ke varg ka nirnaya karna bahudha kathin ho jaata hai.

sanrachana ke aadhaar par teenon vargo mein upabhed kiye jaate hain. aashmik pindon mein do mukhya upabhed hain jinmein se ek ko kaundraait aur doosare ko akaundraait kehte hain. pehle upavarg ke pindon ka mukhya lakshan yeh hai ki unamein kuchh vishisht vruttaakaar daane, jinhein kaundrayool kehte hain, upasthit rahate hain. jin pindon mein kaundrayool upasthit naheen rahate unhein akaundraait kehte hain.

dhaatvik ulkaapindon mein bhi do mukhya upabhed hain jinhein kramash: ashtaaneek (aaktaaheedraait) aur shashthaaneek (heksaaheedraait) kehte hain. ye naam pindon ki antararachana vyakt karte hain aur jaisa in naamon se vyakt hota hai, pehle vibhed ke pindon mein dhaatvik padaarth ke bandh (plate) ashtaaneek aakaar mein aur doosare mein shashtheeneek aakaar mein vinyast hote hain. is prakaar ki rachana ko vidaamanastetar kehte hain evam yeh pindon ke maarjit prushth par badi sugamata se pahachaani ja sakti hai.

dhaatvaashmik ulkaapindon mein bhi do mukhya upavarg hain jinhein kramaanusaar pailesaait aur ardhadhaatvik (meejosidraait) kehte hain. inmein se pehle upavarg ke pindon ka aashmik ang mukhyat: auleeveen khanij se bana hota hai jiske sfat praaya: vruttaakaar hote hain aur jo lauh-nikal dhaatuon ke ek tantr mein samaavrutt rahate hain. ardhadhaatvik ulkaapindon mein mukhyat: paairaukseen aur alp maatra mein enaurthaait felsapaar vidyamaan hote hain.

sanrachana

poorv prakaran mein yeh ullekh kiya ja chuka hai ki dhaatvik aur aashmik angon ki pradhaanata ke aadhaar par ulkaapind vargeekrut kiye jaate hain. kintu in pindon mein raasaayanik tatvon aur khanijon ke vitran ke sambandh mein koi sunishchit aadhaar prateet naheen hota. ulkaapindon ke teen mukhya vargon ke atirikt anekaanek upavarg hain jinmein se pratyek ka apna pruthak vishesh khanij samudaaya hai. abhi tak praaya: 25 nae vargon ka pata laga hai aur praaya: prati do varsh ek nae upavarg ka pata lagta raha hai. kathinaai is baat ki hai ki adhyayan ke liye upalabdh padaarth atyant alp maatra mein hote hain.

abhi tak ulkaapindon mein keval 52 raasaayanik tatvon ki upasthiti pramaanit hui hai jinke naam nimnalikhit hain:

. okseejan. gandhak. plaitinm. loha

. aargan gailiym. faasforas vang (raaainga)

aarsenik jarameniym beriym vainediym

indiym jirkoniym bereeliym. silikn

. ireediym. taaiteniym. mainganeej seejiym

. aintimni telooriym maiganeeshiym seeriym

. ailyuminiym. taamr maulibdenam sees (seesa)

. kaarban thooliym yashad (jasta). sodiym

kaidamiym. naaitrojan rajat (chaaaindi) skaindiym

. kailsiym. nikal. rutheniym svarn (sona)

. kobalt paarad rubeediym straunshiym

. kromiym. pailediym. rediym. haaidrojan

. kloreen. potaisiym leethiym. heeliym

in 52 tatvon mein se keval aath prachur maatra mein paae jaate hain, jinmein haalon sabse pramukh hai. anya saat mein kramaanusaar oksijn, silikn, mainganeeshiym, gandhak, ailyuminiym, nikal aur kailsiym hain. inke atirikt 20 anya tatv paryaapt maatra mein paae jaate hain tatha unki upasthiti ka pata saadhaaran raasaayanik vishleshan dvaara 1926 se poorv hi lag chuka tha. shesh 24 tatv atyant alp maatra mein vidyamaan hain evam unki upasthiti varnakramadarshaki (spektrograifik) vishleshan se siddh ki gayi hai.

khanij sanrachana ki drushti se ulkaapindon aur pruthvi mein pai gayi shail raashiyon ke lakshanon mein kai antar hote hain. saadhaaranataya bhoomandaleeya shail raashiyon mein svatantr dhaatu roop mein loha tatha nikal atyant durlabh hote hain, kintu ulkaapindon mein dhaatueain shuddh roop mein bahut prachurata se tatha praaya: anivaaryat: pai jaati hain. iske atirikt kai aise khanij hain jo bhoomadaleeya shailon mein naheen paae jaate, par ulkaapindon mein milte hain. inmein se pramukh oldemaait (kailsiym ka salfaaid) aur shraaiberasaait (lohe aur nikal ka fausafaaid) hain. ye donon khanij nami aur aukseejan ki bahulata mein sthaayi naheen hote aur isi kaaran bhoomandaleeya shailon mein naheen milte. inki upasthiti se yeh bodh hota hai ki ulkaapindon ki utpatti aise vaataavaran mein hui jahaaain bhoomandal ki apeksha aaksaaideekaran ki paristhitiyaaain nyoon rahi hongi.

aashmik ulkaapindon mein saadhaaranataya paairokseen aur auleevin ki prachurata evam felsapaar ka abhaav hota hai, jisse unka sangathan bhoomandal ki atibhaasmik (altraabesik) shailon ke sadrush hota hai.

utpatti

ulkaapindon ki utpatti ka vishay bahut hi vivaadaaspad hai. is vishay par anek mat samay samay par prastaavit hue hain, jinmein se kuchh mein inhein pruthvi, chandrama, soorya aur dhoomaketu aadi ka ansh maana gaya hai. ek ati maanya mat ke anusaar inki utpatti ek aise grah se hui jo ab poornataya vinsht ho gaya hai. is vichaar mein yeh kalpana ki jaati hai ki aadi mein praaya: mangal ke aakaar ka ek grah raha hoga jo kisi doosare bade grah ke atyant sameep aa jaane par, athva kisi doosare grah se takaraakar, vinsht ho gaya, jisse arabon ki sankhya mein chhote bade khand bane jo ulka roop mein khamandal mein vichr rahe hain. is mat ke anusaar dhaatvik ulka us kalpit grah ka keindreeya bhaag tatha aashmik ulka oopari prushth niroopit karte hain. yadyapi is upakalpana se ulkaapindon ke anek lakshanon ki vyaakhya ho jaati hai, fir bhi anek baatein anaboojhi paheli rah jaati hain. udaaharanaarth kuchh dhaatvik ulkaapindon mein ashtaaneek rachana hoti hai jo saadhaaranataya 800 degree seinteegred taap par nasht ho jaati hai. aisa vishvaas hai ki us kalpit grah ke vikhandan ke samay avashya hi usamein adhik taap utpann hua hoga. fir bhi yeh samajh mein naheen aata ki yeh ashtaaneek rachana vinsht hone se kaise bachi. isi prakaar yeh shanka bhi bani rahati hai ki akaundraait aashmik ulka mein loha kahaaain se aaya aur kaundraait aashmik ulka mein kaundooyool kaise bane.

ek anya mat mein yeh prastaavit kiya gaya hai ki ulkaapindon ki utpatti grahon ke saath saath ho hui, athva yon kehna chaahiye ki sauramandal evam samast khamandaleeya padaartho ki utpatti ulkaapindon se hi hui. is kalpana ke anusaar aadi vishv ulkaapindon se paripoorn tha ev kaalaantar mein ve pind vibhinn punjon mein ekatrit hote gaye tatha unke adhikaadhik ghaneekaran ke kramaanusaar gaisamaya nohaarika, nakshatr evam grah utpann hue. is kalpana ki ek badi truti yeh prateet hoti hai ki khamandal mein upasthit ulkaapind itni door-door chhitraae hue hain tatha unka paarasparik aakarshan itna ksheen hai ki unke ekatr hokar badi raashi banane mein atyadhik samay lagega. kintu ismein koi sandeh naheen ki ek baar paryaapt bade aakaar ki raashi ban jaane ke baad vah apni satta banaae rakh sakega aur kaalaantar mein aur adhik pindon ko apne mein milaakar apne aakaar ki vruddhi bhi kar sakega. sambhav hai, uparyukt vidhiyon mein anshat: sanshodhan karne se inki utpatti ki vaastavik vidhi nirdhaarit ho sake.

bhaarateeya sangrah

ulkaapindon ka ek bruhat sangrah kalakatte ke bhaarateeya sangrahaalaya (ajaayabaghar) ke bhoovaijnyaaanik vibhaag mein pradarshit hai. iski dekharekh bhaarateeya bhoovaijnyaaanik sarvekshan sanstha ke nireekshan mein hoti hai. prachalit niyamon ke anusaar desh mein kaheen bhi gira hua ulkaapind sarkaari sampatti hota hai. jis kisi ko aisa pind mile usaka kartavya hai ki vah use sthaaneeya jilaadheesh ke paas pahuaincha de jahaaain se vah bhaarateeya bhoovaijnyaaanik sarvekshan vibhaag ko bhej diya jaata hai. is prakaar dheere-dheere yeh sangrah apne dhang ka anokha ho gaya hai. iske atirikt is sangrah mein videshon se bhi praapt namoone rakhe gaye hain. Asia bhar mein yeh sangrah sabse bada hai aur vishv ke anya sangrahon mein bhi iska sthaan atyant ooaincha hai, kyonki ek to ismein anek bhaaainti ke namoone hain aur doosare anek namoone ati durlabh jaatiyon ke hain. sab milaakar ismein 468 vibhinn ulkaapaat niroopit hain, jinmein se 149 dhaatvik aur 319 aashmik varg ke hain.

is sangrahaalaya ki sabse badi bhaarateeya aashmik ulka Allahabad jile ke meduaa sthaan se praapt hui thi (dr. chitrafalak). vah 30 August 1920 ko praat: 11 bajkar 15 minute par giri tha. usaka bhaar praaya: 56,657 gram (4,818tole) hai aur deerghatam lanbaai 12 inch hai. doosra sthaan us pind ka hai jo malaabaar mein kutteepuram gram mein 6 April 1914 ko praat: kaal 7 baje gira tha. iska bhaar 38,437 gram (3,295 tole) hai. is sangrah mein rakhe hue ulkaapindon ka vivran bhaarateeya bhoovaijnyaaanik sarvekshan ke memauyar sankhya 75 mein vistaarapoorvak diya hua hai.

baahari kadiyaaain