Chuong 3 Vu Tru Trong Vo Hat de - Smith.N Studio

8/3/2019 Chuong 3 Vu Tru Trong Vo Hat de - Smith.N Studio

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CHNG 3V TR TRONG MT V HT

V tr c nhiu lch s, mi mt lch s c xc nh bng mt ht t hon.

Smith Nguyen Studio.


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V T R T R O N G M T V H T

Trang 68 Ngi dch: [email protected]; http://datrach.blogspot.com



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Trang 69Ngi dch: [email protected]; http://datrach.blogspot.com

Hamlet mun ni rng, v mt vt l, loi ngi chng ta bgii hn, nhng tr c ca chng ta t do khm ph ton bv tr v to bo i n nhng ni m ngay c Star Trekcng s khng dm t chn ni m ch c php n trongnhng cn c mng.

V tr l v tn hay ch l rt ln? V v tr l vnh cu hay ch ltrng th? Lm th no m tr c hu hn ca chng ta c th hiu

mt v tr v hn? C phi chng ta qu liu lnh khi th tr li cccu hi ? Chng ta s khng may ging Prometheus, ngi lycp la ca thn Zeus cho con ngi s dng v b trng pht v sliu lnh bng mt si dy xch tri vo ni mt con ibng n l gan ca mnh hay khng?

Mc d c cu chuyn cnh bo trn, ti vn tin chng ta c th vnn c gng hiu v tr ny. Loi ngi c nhng bc tin bng k trong vic nhn thc v tr, c bit l ch trong mt vinm qua. Chng ta vn cha c mt bc tranh hon chnh, nhng

chng ta tin rt gn n n.iu r rng nht v khng gian l chng lin tc v lin tc. iuny c khng nh bng cc dng c rt hin i nh l knhthin vn Hubble, cho php chng ta thm d nhng ni su thmca khng gian. Nhng iu m chng ta nhn thy l hng t t ccthin h vi nhng hnh dng v kch thc khc nhau (hnh 3.1),mi thin h gm nhiu t ngi sao, trong , rt nhiu ngi sao ccc hnh tinh quay xung quanh. Chng ta ang sng trn mt hnhtinh ang quay xung quanh mt ngi sao nm trn mt cnh tay bn

(Hnh trn) Prometheus:hnh v trn mt chic bnhEtruscan vo th k th sutrc cng nguyn.

(Hnh trang trc) Mt phithuyn con thoi ang nngcp ng knh v gngca i thin vn v trHubble. Pha di l lca c.

Ta c th ti b giam trong mt v htV t coi mnh l cha t ca khong khng v tn...

- Shakespeare,Hamlet, hi 2, cnh 2

(nguyn vn:I could be bounded in a nutshell

And count myself a king of infinitive space...)



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(Hnh 3.1) Khi chng ta nhn su vo trong v tr, chng ta s thy hng t t thin h.Cc thin h c th c hnh dng v kch thc khc nhau; chng c th c hnh e-lp hoc hnh xoy c gingnh di ngn h ca chng ta.

Thin h xoy c NGC 4414 Thin h thang xoy 4314 Thin h e-lp NGC 147



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ngoi ca di Ngn h hnh xon c. Bi trong cc cnh tay xonc gii hn tm nhn ca chng ta vo vng v tr nm trong mtphng ca thin h. Nhng chng ta c th nhn rt r vng khnggian nm trong mt nn c trc vung gc vi mt phng . V tac th v s v tr ca cc thin h xa xi (hnh 3.2). Ta thy rngcc thin h phn b tng i ng nht trong khng gian vi mts ni c mt dy c hn v c cc khong khng trng rng.Mt cc thin h gim i nhng khong cch ln, ta thy chngc v nh th v cc thin h qu xa v qu yu n ni chng takhng th nhn ra chng. Vi tm quan st ca con ngi by gi,ta c th ni v tr l v tn trong khng gian (hnh 3.3).

Mc d ti mi v tr trong khng gian, v tr c v nh khng thayi, nhng chc chn n thay i theo thi gian. iu ny ch cbit vo nhng nm u ca th k 20. Trc , ngi ta cho rngv tr khng thay i theo thi gian. V tr c th tn ti trongmt thi gian v hn, nhng iu s dn n cc kt lun v l.Nu cc ngi sao bc x trong mt thi gian v tn th chng snung nng v tr cho n nhit ca chng. Thm ch ngay c

(Hnh 3.2)

Tri t ca chng ta (E) quayxung quanh mt tri, mt trinm trong mt cnh tay ngoi raca di ngn h. Bi sao ca cnhtay cn tr tm nhn ca chngta theo mt phng ca ngn hnhng khng cn tr tm nhn vhai pha ca mt phng .



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ban m, ton b bu tri ca chng ta cng s sng nh mt tribi v mi mt ng ngm s i n mt ngi sao hay mt mmy bi b cc ngi sao nung nng cho n bng nhit ca ccngi sao (hnh 3.4).

Vic chng ta thy ban m bu tri ti l rt quan trng. iu cho thy rng v tr khng th tn ti mi mi trng thi m chngta thy ngy hm nay. Phi c ci g xy ra trong qu kh cc ngi sao ta sng ch trong mt thi gian hu hn trc y.iu ny ni rng nh sng t cc ngi sao rt xa xi vn cha kpn ch chng ta. N s gii thch ti sao bu tri ban m khngsng theo tt c cc hng.

(Hnh 3.3)

Ngoi tr mt s ni c mt cao, chng ta thy rng cc thin

h c phn b kh ng nhttrong khng gian.



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Nu t trc n nay cc ngi sao vn v tr th ti sao cchy vi t nm chng li t nhin ta sng? ng h no ni vichng rng n lc cn chiu sng? Nh chng ta thy, iuny lm cc nh trit hc nh Immanuel Kant bi ri v ng tin rngv tr tn ti mi mi. Nhng vi phn ng mi ngi, tngcho rng v tr c sng to ging nh ngy nay ch cch y vingn nm l hp l.

Tuy vy, vo thp nin 20 ca th k 20, cc tng khc n tcc quan st ca Vesto Slipher v Edwin Hubble bt u xut hin.Nm 1923, Hubble pht hin ra rng thc ra rt nhiu vng sngc gi l tinh vn (nebulae) chnh l cc thin h, mt tp hpkhng l cc ngi sao nh mt tri nhng khong cch rt xa.

(Hnh 3.4)

Nu v tr l tnh ti v v hntheo tt c cc hng, mi mt

ng ngm s kt thc mtngi sao, iu ny lm bu trim s sng nh mt tri.



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HIU NG DOPPLER

Hiu ng Doppler ni ln mi quanh gia tc v bc sng, mt kinhnghim ta thy hng ngy.Hy lng nghe mt chic my bay ingang qua u chng ta; khi n tin lign chng ta ta nghe thy ting ng cchi tai hn, cn khi n i ra xa chngta th ting ng s trm hn.Ting ng chi tai tng ng vi bc

sng (khong cch gia hai nh sngk tip nhau) ngn hn v tn s (ssng trong mt giy) cao hn. l do khi my bay tin li gn chngta th khong cch gia hai nh sngm do my bay pht i n chng ta sgn nhau hn.Ngc li, khi my bay i ra xa cc bcsng s tng ln v m tn s thp i.



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chng xut hin rt nh v yu th khong cch cn phi ln n ninh sng t phi mt hng triu thm ch hng t nm mi nc chng ta. iu ch ra rng im bt u ca v tr khngth ch vi ngn nm trc y.

Nhng iu th hai m Hubble quan st c cn quan trng hn.Bng vic phn tch nh sng t cc thin h khc, cc nh thin vnc th bit cc thin h ang tin li gn chng ta hay i ra xa chngta (hnh 3.5). H cc k ngc nhin khi pht hin ra rng gn nhhu ht cc thin h ang i ra xa chng ta. Chnh Hubble nhnthy hm y kch tnh ca pht hin ny: ti cc khong cch ln,mi thin h iu chuyn ng ra xa khi cc thin h khc. V trang gin n (hnh 3.6).

(Hnh 3.5)Hiu ng Doppler cng ng ivi sng nh sng. Nu khongcch t mt thin h ti tri tm khng i th cc vch ctrng trong quang ph s xuthin ti v tr bnh thng hay cngi l v tr chun. Tuy nhin nuthin h ang chuyn ng raxa chng ta th cch sng s b kodi ra v vch c trng s b dchchuyn v pha (phi). Nuthin h ang chuyn ng lign chng ta th cc bc sng sb p li v cc vch s b dch vpha xanh (tri).



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Pht hin v s gin n ca v tr l mt trong nhng cch mng

tr tu v i nht ca th k 20. Tt c mi ngi rt ngc nhin vpht hin ny v n thay i hon ton tranh ci v ngun gc cav tr. Nu cc thin h chuyn ng ra xa nhau th trong qu khchng cn phi gn nhau hn. T tc gin n hin thi, chngta c th c on rng cc thin h cn phi rt gn nhau cc ymi n mi lm t nm. Nh ni trong chng trc, RogerPenrose v ti c th chng minh rng thuyt tng i rng caEinstein cho bit v tr v bn thn thi gian c sinh ra trong mtv n d di. chnh l li gii thch cho cu hi ti sao ban mbu tri li ti: khng mt ngi sao no c th pht sng lu hn

nh chp thin h lngging Andromeda do Hub-ble v Slipher chp.

CC KHM PH CASLIPHER V HUBBLE VONHNG NM 1910 1930

1912 Slipher o nh sng tbn tinh vn v thy rng ba tinhvn b dch v pha cn An-dromeda b dch v pha xanh.ng gii thch rng Andromedaang chuyn ng li gn chngta cn ba tinh vn kia th chuynng ra xa chng ta.1912-1914 Slipher o 12 tinhvn. Tt c tr mt tinh vn udch v pha .1914 Slipher bo co phthin ca ng trc Hi thinvn Hoa K. Hubble nghe boco ny.1918 Hubble bt u nghincu cc tinh vn.1923 Hubble xc nh cc tinhvn c hnh xoy c l cc thinh.1914-1925 Slipher v nhngngi khc tip tc o dchchuyn Doppler. Nm 1925, h

ghi nhn c 43 dch chuyn v 2 dch chuyn xanh.1929 Hubble v Milton Hu-mason sau khi tip tc o dchchuyn Doppler v thy rng tm v m cc thin h ang lira xa nhau cng b khm phca h v v tr ang gin n.



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(Hnh 3.6)NH LUT HUBBLE

T phn tch tia sng t ccthin h khc, vo nhng nm1920, Edwin Hubble pht hinra rng hu ht cc thin hang chuyn ng ra xa khichng ta vi vn tc V t l vikhong cch R t chng ntri t, do V = H*R.nh lut ny c gi l nhlut Hubble, n cho thy v tr

ang gin n vi hng s Hub-ble H xc nh tc gin n. th bn di th hin ccquan st rt mi v dch chuyn ca cc thin h khng nhnh lut Hubble ng vikhong cch rt xa chng ta.S cong ln vng c khongcch rt ln trn th cho thyrng s gin n ang c tngtc, iu ny c th do nnglng chn khng.

Khongccht

ccthinhtichngta

Vn tc m cc thin h chuyn ng ra xa chng ta

Edwin Hubble trn i thin vn Mount Wilson 100 inch

nm 1930.



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V N LN NNG BNG

Gi s thuyt tng i rng ng, th v tr skhi u vi mt v nhit v hn caim k d v n ln. V v tr ang gin n lnnhit ca bc x b gim i. Khong mt phn

trm giy sau v n ln, nhit vo khong 100t v v tr ch yu gm cc photon, in t vneutrino (nhng ht cc nh) v cc phn ht cachng cng vi mt s proton v neutron. Ba giytip theo, v tr lnh xung cn 1 t , proton,neutron bt u kt hp to ra ht nhn nguyn thelium, hydro v cc nguyn t nh khc.Hng trm ngn nm sau, nhit xung cn vingn , cc in t chuyn ng chm dn v ht

nhn cc nguyn t nh bt in t to thnhnguyn t. Tuy nhin, cc nguyn t nng to nnchng ta nh carbon v oxygen ch c hnhthnh hng t nm sau t vic t helium tmcc ngi sao.Bc tranh v trng thi c nng vo thi k s

khai ca v tr c nh khoa hc George Gamowa ra vo nm 1948 trong mt bi bo ng vitcng vi Ralph Alpher. Bi bo a ra mt tinon quan trng l bc x t giai on s khainng bng vn cn tn ti cho n ngy nay.Tin on ca h c nh vt l Arno Penzias vRobert Wilson kim chng vo nm 1965 da voquan st bc x phng vi sng.

K d v n lnK nguyn Plank,cc nh lut vtl khng th pdng

10-43 s 10-35 s 10-10 s 1 s 3 pht 0.3 triu nm 1 t nm 15 t nm

K nguynca Lthuyt thngnht ln(GUT). Vtcht nhiuhn phnvt cht

Thi k inyu thngtr bi ccquark v

phn quark

K nguynlepton vhadron. Ccquark tothnh pro-ton, neutron,meson v

baryon

Proton vneutronkt hpto thnhhydromhellium,lithium vdeuterium

Vt chtv bc xkt hp vinhau hnhthnh htnhn bnu tin

Vt chtv bc xtch ri. Vquang hc,v tr mc tr nntrong suti vi bcx phngv tr

Cc m vtcht hnhthnh ccquasar, ngisao v tinthin h. Ccngi sao btu tng hpcc ht nhnnng hn

Cc thinh mi hnhthnh cng cch mt tri cc quanh ccngi sao. Ccnguyn t kthp to nncc phn t

phc tp cho

s sng



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mi n mi lm t nm, khong thi gian tnh t v n ln.

Chng ta quen thuc vi quan nim cho rng cc s kin l hqu ca cc s kin trc , v n lt cc s kin trc lil h qu ca cc s kin trc na. C mt chui nhn qu kodi mi v qu kh. Nhng by gi hy gi s rng chui nhn qu c mt im khi u. Hy gi s rng c mt s kin u tin.Ci g gy ra n? y khng phi l mt cu hi m nhiu nh

khoa hc mun cp. H c gng trnh cu hi bng cch chorng v tr khng c im khi u nh ngi X Vit hoc nuko rng ngun gc ca v tr khng nm trong a ht ca khoahc m thuc v siu hnh hc (metaphysics) hoc tn gio. Theoti, mt nh khoa hc chn chnh s khng lm nh th. Nu ccnh lut khoa hc khng ng ti thi im bt u ca v tr thchng c th khng ng ti cc thi im khc hay khng? Mtnh lut s khng l mt nh lut nu thnh thong n mi ng.Chng ta cn phi c gng hiu im khi u ca v tr da trnc s khoa hc. C th n vt qua kh nng ca chng ta, nhng

t nht chng ta nn c gng th lm iu .

Mc d cc nh l do Penrose v ti chng minh cho thy rng vtr phi c im bt u, nhng chng khng cho bit nhiu thngtin v bn cht ca s khi u . Chng ch ra rng v tr bt ubng mt v n ln, mt im m ton b v tr v tt c mith trong b nn vo mt im c mt v hn. Ti im ny,thuyt tng i rng ca Einstein khng cn ng, do , khngth dng n tin on v tr bt u nh th no. Con ngi vncha hiu ngun gc ca v tr v hin nhin l n nm ngoi phm

vi ca khoa hc.

Cc nh khoa hc khng hi lng vi kt lun ny. Nh chng 1v chng 2 ch r, l do thuyt tng i khng ng ti gn vn ln l do n khng tch hp vi nguyn l bt nh, yu t ngunhin ca thuyt lng t m Einstein phn i da trn Chakhng chi tr xc xc. Tuy vy tt c cc bng chng u chothy Cha l mt tay chi bc. Ngi ta c th ngh v v tr nhmt sng bc khng l vi cc con xc xc c gieo v cc vng



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s c quay mi khi c dp (hnh 3.7). Bn c th ngh rng iukhin mt sng bc nh vy l mt v lm n rt may ri bi bn rt

c kh nng mt ht tin khi xc xc gieo hay vng s quay. Nhngvi mt s ln cc v nh cc, s ln thng v thua trung bnh cth on c, mc d kt qu ca mt ln c th khng on trcc (hnh 3.8). Nhng ch sng bc bit chc t l trung bnh cli cho h. iu gii thch ti sao ch sng bc rt giu. C hiduy nht bn c th thng h l c cc tt c s tin ca bnvo mt s t ln gieo xc xc hoc quay s.

V tr cng ging nh vy. Khi v tr ln nh ngy nay, c mt sln ln gieo xc xc, v kt qu trung bnh c th on trc c.

V th cc nh lut c in ng i vi cc h ln. Nhng khi vtr rt nh, ging nh gn thi im v n ln, ch c mt s t lngieo xc xc, v nguyn l bt nh tr ln quan trng.

V v tr c gieo xc xc hoi xem ci g s xy ra nn v trkhng c mt lch s duy nht nh ngi ta c th ngh. Thay vo, v tr c tt c cc lch s kh d, mi mt lch s c mt xcxut ca ring n. Phi c mt lch s v tr trong Belize thuy chng vng ti cc k Olympic mc d xc xut ca v tr thp.

tng v v tr c nhiu lch s nghe c v nh chuyn khoa hcvin tng, nhng ngy nay khoa hc chp nhn n. tng c mt nh vt l v i, mt ngi y c tnh l RichardFeynman xut.

By gi chng ta kt hp thuyt tng i rng ca Einstein v tng v tr c nhiu lch s ca Feynman thnh mt l thuytthng nht hon ton m t mi th xy ra trong v tr. L thuytthng nht ny s cho php ta tnh c v tr s pht trin thno nu ta bit cc lch s bt u nh th no. Nhng bn thn lthuyt khng ni cho chng ta bit v tr bt u th no haytrng thi ban u ca v tr l g. bit c iu chng tacn mt ci gi l iu kin bin hay l quy tc bin. Cc iu kinbin ni cho chng ta bit ci g xy ra ra ca v tr, bin cakhng thi gian.

Nu ra ca v tr ch l nhng im bnh thng ca khng thigian, chng ta c th i qua n v tuyn b lnh th bn ngoi ra vtr l mt phn ca v tr. Mt khc, nu bin ca v tr nm trn

(Hnh 3.7 v hnh 3.8, trang k)

Nu mt ngi chi bc t cc cho rt nhiu ln quay th tac th on kh chnh xc kt qucho anh ta v kt qu ca cc lnquay s c ly trung bnh. Ngc li, ta khng th onc kt qu ca bt k ln nhcc no.



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1 ln t cc 10 ln t cc

100 ln t cc

kt qukt qu

kt qu



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mt ng lm chm trong khng thi gian m khng thigian b cun li v mt ln v cng th s rt kh xc nh cciu kin bin c ngha.

Tuy vy, mt ng nghip ca ti l Jim Hartle v ti nhn rarng c mt kh nng th ba. V tr c th khng c bin trongkhng thi gian. Thot nhn, iu ny c v mu thun trc tipvi cc nh l m Perose v ti chng minh, chng cho thy vtr cn phi c mt im khi u, mt ci bin thi gian. Tuy vy,nh c gii thch trong chng 2, c mt loi thi gian c gil thi gian o vung gc vi thi gian thc bnh thng m chngta ang tri nghim. Lch s v tr theo thi gian thc s xc nhlch s ca n theo thi gian o v ngc li, nhng hai loi lch sny c th rt khc nhau. c bit l v tr cn c khi u v kt

Nu bin ca v tr l mt imca khng thi gian, chng ta cth gi cho bin gin ra.



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Chic bng en ti Caltech khi Feynman mt nm 1988 Richard Feynman

CU CHUYN V FEYNMAN

Sinh ra ti Brooklyn, New York nm 1918, Rich-ard Feynman bo v tin s ti i hc Princetondi s hng dn ca John Wheeler vo nm1942. Ngay sau , ng b li ko v d n Ma-hattan. , ng ni ting v tnh cch ci mv hi hc ti phng th nghim Los Alamos,ng rt thch ph cc h thng bo mt v tr thnh mt nh vt l khc thng: ng trthnh ngi ng gp ch yu cho l thuyt bomnguyn t. Thi quen lin tc tm ti khm phca Feynman v th gii chnh l gc r ca conngi ng. N khng ch l ci my lm nn ccthnh cng khoa hc m cn dt ng n rt nhiukhm ph k th v nh gii m nhng ch tnghnh ca ngi Maya.Vo nhng nm sau th chin hai, Feynmantm ra mt phng php mi rt hiu qu trongvic nhn thc c hc lng t. V chnh iu mang gii Nobel nm 1965 n vi ng. ngthch thc gi thuyt c in c bn l mi ht c

mt lch s c bit. Thay vo , ng cho rngcc ht di chuyn t ni ny n ni khc theo ttc cc l trnh kh d trong khng thi gian. Vimi l trnh Feynman lin h vi hai con s, cons th nht l kch thc bin ca sng vcon s th hai l pha cho bit l nh hochm sng. Xc sut ca mt ht i t A n B chobi tng cc sng lin quan n l trnh kh d iqua A v B.Tuy vy trong cuc sng hng ngy, chng ta thydng nh cc vt th i theo mt l trnh duynht t im u n im cui. iu ny phhp vi tng a lch s (hoc tng theo cclch s), v i vi cc vt th ln th qui tc cang v gn cc con s cho mi l trnh m bott c cc l trnh (tr mt l trnh duy nht) phitrit tiu ln nhau khi ng gp ca chng ckt hp li. Ch c mt trong s v hn cc ltrnh c ngha i vi chuyn ng ca cc vtth v m l c xem xt v chnh l l trnhc c t cc nh lut chuyn ng c in caNewton.

thc trong thi gian o. Thi gian o hnh x nh ging ht mttrc khc ca khng gian. Cho nn cc lch s ca v tr trong thigian o c th c coi nh cc mt cong ging nh mt qu bng,mt mt phng, hoc mt hnh yn nga nhng c bn chiu thay

v hai chiu (hnh 3.9).

Nu lch s ca v tr tin n v hn ging nh hnh yn nga haymt phng th ngi ta gp vn trong vic ch r cc iu kinbin v hn l g. Nhng ngi ta c th trnh khng cn ch ra iukin bin nu cc lch s ca v tr nm trong thi gian o l ccmt ng, ging nh b mt tri t. B mt tri t khng c binhoc ra. Khng c bo co ng tin no v vic con ngi b ri rakhi tri t!

Trong tch phn l trnh Feyn-man, mt ht c th ly tt c ccl trnh kh d



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(Hnh 3.9) CC LCH S CA V TRNu cc lch s ca v tr tin n v hn nh hnh chic yn nga, ta s gp kh khn trong vic tm iu kinbin v lc n l v hn. Nu cc lch s ca v tr trong thi gian o l cc mt ng ging nh b mt trit th ta cng khng th ch ra iu kin bin c.

CC NH LUT TIN HA V

CC IU KIN BAN U

Cc nh lut vt l bt buc mttrng thi ban u phi tin hatheo thi gian. V d, nu ta nmmt hn vo trong khng khth cc nh lut hp dn s quytnh chnh xc chuyn ng sau ca hn . Nhng chng ta khng th onc hn s ri chnh xc ti

u t cc nh lut . lmc iu chng ta cn phibit tc v hng ban u khihn ri khi tay chng ta. Nicch khc l chng ta cn phi bitiu kin ban u hay iu kin bin ca chuyn ng ca hn.

V tr hc cng c gng m t tin

ha ca ton b v tr bng ccnh lut vt l. Do , chng tacn phi hi iu kin ban u cav tr l g p dng n vo ccnh lut trn.Trng thi ban u c th c nhhng rt quan trng ln cc cim ca v tr, c l quan trngnh tnh cht ca cc ht v lc cbn i vi cuc sng sinh vt.C mt xut v iu kin khng

bin, xut ny cho rng khnggian v thi gian l hu hn, tothnh mt mt ng nhng khngc bin, n ging nh b mt trit l hu hn nhng khng c bin. Gi thit khng bin datrn tng ly tng theo cc lchs ca Feynman nhng lch s ca

ht trong tng Feynman c thay

bng ton b khng thi gian biudin cho lch s ca ton b v tr.Ni mt cch chnh xc, iu kinkhng bin l s hn ch cc lchs kh d ca v tr vo cc khngthi gian khng c bin trong thigian o. Hay ni cch khc, iukin khng bin ca v tr l vtr khng c bin.Hin nay cc nh v tr hc angnghin cu cc cu hnh ban u

cu hnh c c t gi thitiu kin khng bin, v c thcng vi nguyn l v nhn yu(xem nguyn l v nhn trang86 - ND) lm cho v tr tin han trng thi ging nh ta quanst hin nay.



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Nu cc lch s ca v tr trong thi gian o thc s l cc mtng nh Hartle v ti xut th iu c ngha quan trngv trit hc v hnh dung ca chng ta v ni chng ta sinh ra. V

tr l hon ton t thn (self-contained); n khng cn bt k ci gbn ngoi ln giy ct cho ng h v tr v lm cho n hotng. Thay vo , tt c mi th trong v tru c xc nh bng cc nh lutkhoa hc v bng cc ln gieo xc xctrong v tr. iu ny nghe c v xa xnhng l iu m ti v nhiu nh khoahc khc tin.

Hn na, nu v tr khng c cc

iu kin bin nh th th v tr skhng c mt lch s duy nht. V tr s c nhiu lch s nhFeynman xut. S c mt lch s trong thi gian o tng ngvi mi mt ng kh d, v mi lch s trong thi gian o s xcnh mt lch s trong thi gian thc. Vy nn chng ta c rt nhiutrng thi kh d cho v tr. Ci g chn mt v tr c bit mchng ta ang sng ra khi ra khi mt tp hp tt c cc v tr khd? Mt im m chng ta cn ch l rt nhiu lch s kh d cav tr s khng tri qua mt chuis kin hnh thnh cc thin h vcc v sao, trong khi chui s kin li rt quan trng i vi s pht trinca ring chng ta. Trong khi cc sinh vtc tr tu c v nh kh c th tin hanu khng c cc thin h v cc ngith vic chng ta tn ti nh l mtsinh vt c kh nng t cu hi Tisao v tr li nh ngy nay? l mt giihn ca lch s ca chng ta. iu ng

v tr ny l mt trong mt thiu s cclch s bao gm cc thin h v v

sao. y l v d ca mt nguyn l gi l nguynl v nhn (anthropic principle). Nguyn l v

nhn ni rng v tr cn phi gn ging nhchng ta thy v nu v tr ny khc i ths khng c ai y quan st n (hnh3.10). Rt nhiu nh khoa hc khng thch

nguyn l v nhn v n c v m h vhnh nh khng c nhiu kh nng tin on.

Nhng nguyn l v nhn c th c rt ra t

B mt tri t khng c binhoc ra. Cc bo co v chuync ngi b ri ra khi tri t chl s khuych i.



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Kch thc gin nThigian

NGUYN L V NHN

Ni mt cch nm na, nguyn l v nhn chorng chng ta thy v tr, hoc ch t mt phnca v tr, nh ngy nay l bi v chng ta tnti. C mt vin cnh l v tr hon ton tringc vi mt gic m v mt l thuyt thngnht v c th d on chnh xc, trong , ccnh lut ca t nhin l hon thin v th gii lnh vy v n khng th khc i c. C nhiuphin bn ca nguyn l v nhn: t nguyn lrt yu (v tr khng lin quan n con ngi)cho n rt mnh (s lin h ca con ngi viv tr mnh n mc v l). Mc d mt s ccnh khoa hc min cng chp nhn nguynl v nhn mnh th mt s ngi li tranh civ tnh thit thc trong mt s quan im canguyn l v nhn yu.Chung qui l nguyn l v nhn yu gii thchv cc thi k hoc cc phn v tr kh d khcnhau m chng ta c th sng c. V d, ldo ti sao v n ln li xy ra cch y khong

mi t nm l v tr cn phi tn ti lu mt s ngi sao kt thc qu trnh tin ha to racc nguyn t nh l oxygen hoc carbon, khngc chng, con ngi khng th c mt c, vtui v tr cng phi ngn mt s ngisao vn tip tc cung cp nng lng duy tr ssng.Trn c s iu kin khng bin, chng ta c ths dng qui tc ca Feynman xc nh cccon s cho mi lch s v tr nhm tm ra tnhcht c th c ca cc v tr. Trong bi cnhny, ta c th dng nguyn l v nhn nh l mti hi cho cc lch s c cuc sng tr tu. Ttnhin l vi nguyn l v nhn, con ngi s cmthy hnh phc hn nu con ngi c th chngminh rng mt s cc cu hnh ban u cho vtr c v nh l s tin ha c mt v trging nh chng ta ang quan st. iu ny ng rng trng thi ban u ca phn v tr chngta ang sng khng nht thit phi c chnmt cch k lng.



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(Hnh 3.10, trang trc)

Hnh tn cng pha tri (a) minhha cc v tr ang co li, trthnh cc v tr ng. Hnh tncng pha phi (b) l cc v trm tip tc gin n mi mi.Cc v tr ti hn cn bng giavic co li v gin n (c1) hocv tr lm pht hai ln (c2) c thc sinh vt c tr tu. V tr cachng ta (d) hin nay ang thtip tc gin n. Lm pht nhanh kp s khng

to ra cuc sng tr tu

Hin nay lm pht ca v tr ca

chng ta vn tip tc gin n

mt cng thc chnh xc v dng nh n rt quan trng khi giiquyt vn ngun gc v tr. Nh ni chng 2, thuyt-Mcho php mt s ln cc lch s kh d ca v tr. Phn ln trongs khng ph hp cho s pht trin ca i sng tr tu; chnghoc l trng rng, tn ti trong mt thi gian ngn v b un congqu nhiu hoc khng n v mt s kha cnh no . ng nhtheo tng ca Feynman v v tr c nhiu lch s, xc sut cacc lch s khng c s hin din ca sinh vt tr tu c th rtcao (xem trang 84).

Thc ra vic c bao nhiu lch s m khng c s c mt ca sinhvt c tr tu khng quan trng. Chng ta ch quan tm n mtnhm cc lch s c cuc sng c tr tu pht trin. Cuc sng trtu ny khng nht thit phi c ci g ging nh con ngi.Chng c th l cc sinh vt l mu xanh nh b. Thc ra chngcn thng minh hn con ngi. Loi ngi khng phi lsinh vt tr tu nht trong v tr.

Mt v d v sc mnh ca nguyn l v nhn khi xts chiu trong khng gian. Kinh nghim chung cho thychng ta ang trong mt khng gian ba chiu. iu mun ni rng chng ta biu din v tr ca mt imtrong khng gian bng ba con s, v d, v , kinh v cao trn mc nc bin. Nhng ti sao li l mt khnggian ba chiu? Ti sao khng phi l hai chiu, bn chiu haymt s chiu khc nh khoa hc vin tng? Trong thuyt-M,



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(Hnh 3.11)

Nhn t xa, mt ng ung ncging nh mt ng mt chiu.

khng gian c chn hoc mi chiu, nhng ngi ta cho rng csu hoc by chiu b cun li rt nh, ch cn li ba chiu ln vgn nh phng m thi (hnh 3.11).

Ti sao chng ta khng sng trong mt lch s trong tm chiub cun nh li ch li hai chiu ln cho chng ta nhn bit? Mtsinh vt hai chiu s rt kh c th tiu ha thc n. Nu n c mt

ci rut chy sut c th chng th ci rut s chia sinh vt lmi v hai mnh s ri khi nhau. Do , hai chiu phng khng cho bt k sinh vt phc tp nh cuc sng c tr tu. Mt khcnu s chiu gn phng nhiu hn ba th lc hp dn gia hai vtth tng rt nhanh khi chng tin n gn nhau. iu ny c nghal cc hnh tinh s khng c qu o bn vng quanh mt tri. Cchnh tinh hoc l s ri vo mt tri (hnh 3.12A), hoc l s thotvo khong khng ti tm v lnh lo (hnh 3.12B).

Tng t nh vy, cc qu o ca in t cng s khng bn, v vt



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(Hnh 3.12A)

(Hnh 3.12B)



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Lch s thi gian o Lch s thi gian thc

cht nh chng ta bit s khng tn ti. Vy nn, tng v tr cnhiu lch s cho php bt k s chiu gn phng, nhng ch c cclch s vi ba chiu phng mi c sinh vt c tr tu. Ch c trongcc lch s nh vy th cu hi Ti sao khng gian c ba chiu?mi c t ra.

Lch s n gin nht ca v tr trong thi gian o l mt hnhcu, ging nh b mt ca tri t, nhng c nhiu hn hai chiu

(hnh 3.13). N xc nh lch s ca v tr trong thi gian thc mchng ta ang tri nghim, trong v tr l nh nhau theo ccim trong khng gian v gin n theo thi gian. Theo cc khacnh ny, n ging nh v tr chng ta ang sng. Nhng tc gin n rt nhanh, v n vn cn gin n nhanh hn na. Vic giatc s gin n nh vy c gi l lm pht (inflation), v n gingnh vic gi c leo thang vi mt tc cha tng thy.

Ni chung s lm pht gi c b coi l khng tt, nhng trong trng

(Hnh 3.13)

Lch s thi gian o khng binn gin nht l mt hnh cu.Lch s trong thi gian o ny xcnh lch s trong thi gian thc(gin n theo kiu lm pht).



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hp ca v tr th lm pht li c li. Lm pht lm trn bt k chtri st no c th xut hin trong thi gian u ca v tr. V vtr gin n, nn v tr s vay mn nng lng t trng hp dn to thm vt cht. Nng lng vt cht dng s c cn bngmt cch chnh xc vi nng lng hp dn m, do , nng lngton phn bng khng. Khi kch thc ca v tr tng gp i, nng

lng vt cht v nng lng hp dn cng tng gp i nhnghai ln khng vn l khng. Gi m gii ngn hng cng n ginnh th nh (hnh 3.14)!

Nu lch s v tr trong thi gian o l mt hnh cu hon ho thlch s tng ng trong thi gian thc s l mt v tr tip tc ginn mi mi theo kiu lm pht. Khi v tr ang lm pht th vtcht khng th ri vo nhau hnh thnh cc thin h v cc vsao, v cuc sng, ch cha ni n cuc sng tr tu nh chng

(Hnh 3.14) Nng lng vt cht Nng lng hp dn



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Thi gian thcThi gian thcKchthcvtr

Kchthcvtr

(Hnh 3.15) V TR LM PHT

Trong m hnh v n ln nng bng, vo nhnggiai on s khai, v tr khng c thi gian nhit truyn t ni ny n ni khc. D vy,chng ta quan st thy rng nhit ca bc xphng vi sng l nh nhau theo cc hng. iuny c ngha l trng thi ban u ca v tr c

nhit nh nhau ti mi ni. tm c mt m hnh, trong , rt nhiucu hnh ban u khc nhau c th tin ha nmt ci g ging nh v tr hin nay, ngita gi thit rng vo giai on s khai, v tr triqua mt thi k gin n rt nhanh. S gin nny c gi l lm pht, tc l n xy ra vi

mt tc cha tng c sau gim tc ginn n nh ngy nay. Mt pha lm pht nh vyc th gii thch cu hi ti sao v tr li gingnhau theo tt c cc hng v c thi gian nh sng truyn t vng ny n vng khctrong v tr s khai.Lch s tng ng trong thi gian o ca mt vtr tip tc gin n theo kiu lm pht mi mi

l mt hnh cu hon ho. Nhng vi v tr cachng ta, qu trnh gin n lm pht b chmli sau mt phn nh ca mt giy v do ccthin h c th c hnh thnh. Trong thi giano, iu c ngha l v tr tr ca chng ta lmt hnh cu b bt cc nam.



27/34



CH S GI C - LM PHT V SIU LM PHT

Thng 7 nm 1914 1,0

Thng 1 nm 1919 2,6

Thng 7 nm 1919 3,4

Thng 1 nm 1920 12,6

Thng 1 nm 1921 14,4

Thng 7 nm 1921 14,3

Thng 1 nm 1922 36,7

Thng 7 nm 1922 100,6

Thng 1 nm 1923 2 785.0

Thng 7 nm 1923 194 000.0

Thng 11 nm 1923 726 000 000 000,0

Mt mc c nm 1914

Mi ngn mc c nm 1914

Hai triu mc c nm 1914

Mi triu mc c nm 1914

Mt t mc c nm 1914

ta, khng th pht trin. Do , mc d gi thit v v tr c nhiulch s dn n cc lch s ca v tr trong thi gian o l cc hnhcu hon ho, nhng khng c g th v c. Tuy nhin, cc lch strong thi gian o l cc hnh cu c cc nam hi bt th thch nghn (hnh 3.15).

Trong trng hp ny, lch s tng ng trong thi gian thc s

gin n trc tin theo kiu c gia tc v lm pht. Nhng sau qu trnh gin n s chm dn v cc thin h c th c hnhthnh. cuc sng tr tu c th pht trin th bt cc namphi rt nh. iu ni rng ban u v tr gin n rt nhanh.Mc k lc v lm pht tin t xut hin c gia hai cuc ichin th gii, khi gi c tng n hng t ln nhng mc lm pht xut hin trong v tr t nht l mt t t t ln hn th(hnh 3.16).

Do nguyn l bt nh nn s khng ch c mt lch s v tr c

(Hnh 3.16) LM PHT CTH L MT QUI LUT CAT NHINLm pht c tng sau habnh cho n thng 2 nm 1920,gi c lc cao hn nm 1918nm ln. Sau thng 7 nm 1922,thi k siu lm pht bt u. Tt

c nim tin vo gi tr ng tinbin mt v ch s gi c tng ccnhanh trong mi lm thng, giatng tc in tin ht cng sutv s mt gi cng nhanh nhth. Vo cui nm 1923, 300 nhmy giy lm vic ht tc v150 cng ty n lot vi 2000 myin lm vic sut ngy m intin.



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(Hnh 3.17) CC LCH S KHD V KHNG KH D

Cc lch s trn nhn ging hnh(a) l nhng lch s kh d nht,nhng ch c mt s cc lch snh th.Mc d cc lch s hi bt bnhthng (b) v (c) km kh d hn,nhng c rt nhiu cc lch sging nh vy, khc bit so vilch s trn nhn cht t.

cuc sng c tr tu. Thay vo , cc lch s trong thi gian o sl mt h gm nhng hnh cu hi bin dng, mi hnh cu s tngng vi mt lch s trong thi gian thc m , v tr lm phttrong mt thi gian di nhng khng phi l v hn. Chng ta cth hi vy th lch s no l lch s kh d nht trong cc lch sc php. Ha ra l cc lch s kh d nht hon ton khng trntru m c nhng ni hi tri st (hnh 3.17). S gn sng cc lchs kh d nht rt nh, so vi lch s trn tru, s gn sng ny chbng vi phn trm ngn. Tuy chng rt nh nhng chng ta c th

o c chng. Chng l nhng thng ging nh trong min vi sngti chng ta t cc hng trong khng gian. V tinh thm d phngv tr (Cosmic Background Explorer) COBE c phng vonm 1989 v lp c bn bc x vi sng ca v tr.

Trn bn vi sng v tr, cc mu khc nhau cho bit cc nhitkhc nhau, nhng ton b di nhit t mu n mu xanh chc gi tr bng mt phn vn K. Cui cng th s thay i giacc vng khc nhau ca v tr s khai cng lc ht do hp

(a) (b) (c)



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dn b sung trong cc vng v tr c hn lm cho vng ngnggin n v suy sp di lc hp dn ca bn thn chng hnhthnh cc thin h v cc v sao. Do , v nguyn l, t nht bn bc x vi sng v tr c mu xanh cho ton b cu trc ca v tr.

Tnh cht ca cc lch s kh d nht ca v tr m thch hp chos xut hin ca cc sinh vt c tr tu s nh th no? Xem ra crt nhiu kh nng ph thuc vo lng vt cht ca v tr. Nu vtcht trong v tr ln hn mt lng ti hn th lc ht hp dn gia

cc thin h s lm chm cc thin h v thm ch cn dng khngcho chng bay ra xa nhau. Sau cc thin h s bt u ri vonhau v tt c s cng i ti mt v co ln (big crunch). V co lns kt thc lch s ca v tr trong thi gian thc (hnh 3.18).

Nu mt v tr thp hn gi tr ti hn, lc hp dn qu yu ngn cn cc thin h ri xa nhau mi mi. Tt c cc ngi sao st chy ht nhin liu, v dn dn v tr s tr ln long v lnhhn. Cho nn, mt ln na, mi s s n hi kt nhng theo mt

Bn ton b bu tri dov tinh COBE chp chothy cc np nhn theo thigian.



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cch km kch tnh hn. Nhng d kt cc th no th v tr cngs tn ti thm vi t nm na (hnh 3.19).

V tr c th c mt th ging nh vt cht c gi l nng lngchn khng (vacuum energy), nng lng chn khng hin dinngay c trong khng gian trng rng. T phng trnh ni ting caEinstein, E=mc2, nng lng chn khng ny c mt khi lng.

iu ni rng nng lng chn khng gy ra mt hiu ng hpdn ln s gin n ca v tr. Nhng iu ng ni l hiu ng hpdn do nng lng chn khng gy ra li ngc li vi hiu ng hpdn do vt cht gy ra. Vt cht lm qu trnh gin n chm li vc th lm dng v o ngc qu trnh . Ngc li, nng lngchn khng li gia tc qu trnh gin n ging nh trong giai onlm pht. Thc ra, nng lng chn khng c tc ng nh hng sv tr c nhc n chng 1 m Einstein b sung vo ccphng trnh ca ng vo nm 1917 khi ng nhn thy cc phngtrnh ny khng a n mt nghim biu din cho mt v tr tnh.

(Hnh 3.18)

Tt c vt cht s b nut vo mtci ging hp dn mnh khngkhip trong mt v co ln, cth l mt trong nhng kt ccca v tr.

(Hnh 3.19, trang k)

Mt v tr lnh lo v trng tritrong tt c mi th u kitsc v cc ngi sao cui cngcng ang chp chn trc khitt v cn kit nhin liu.



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Sau khi Hubble pht hin v tr gin n, ngi ta khng thy cnphi a hng s v tr vo cc phng trnh na, v Einstein cngcho rng hng s v tr l mt sai lm.

Tuy vy, hng s v tr li hon ton khng phi l mt sai lm. Nh ni trong chng 2, ngy nay chng ta nhn thy rng l thuytlng t ni rng khng thi gian c lp y bi cc thng ging

lng t. Trong l thuyt siu i xng, cc nng lng dng vm v hn ca cc thng ging trng thi c bn ny trit tiu giacc ht c spin khc nhau. Nhng chng ta khng trng i ccnng lng m v dng ny trit tiu hon ton n ni khng cnst li mt nng lng chn khng nh b, hu hn no, bi v vtr khng nm trong mt trng thi siu i xng. iu ngc nhinduy nht l nng lng chn khng nh n ni cch y t lungi ta mi nhn ra n. C th y l mt v d na ca nguyn lv nhn. Mt lch s c nng lng chn khng ln s khng hnh

CNGLHNGS VTRLSAILMLN

NHTTRONGITI?

Albert Einstein



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MT VT CHT

Sao siu mi

Phng vi sng

Gii hn nguyn l v nhnCc thin h khng thhnh thnh t vng ny

NNGLNGCHN

KHNG

thnh cc thin h, do , s khng c cc sinh vt c th hi cuhi Ti sao nng lng chn khng li c gi tr bng gi tr mchng ta ang thy?

Chng ta c gng th xc nh lng vt cht v nng lng chnkhng trong v tr t cc quan st khc nhau. Ta c th biu dincc kt qu trong mt gin c trc honh l mt nng lng vtrc tung l nng lng chn khng. ng chm l bin gii cavng m trong sinh vt tr tu c th pht trin (hnh 3.20).

Mi quan st v sao siu mi, cc m thin h v phng bc xvi sng u vch ra gii hn trn gin ny. May mn thay, c ba

(Hnh 3.20)

Kt hp cc quan st t cc v n

siu sao xa xi vi bc x phngvi sng v phn b vt cht trongv tr, ta c th c on cnng lng chn khng v mt vt cht trong v tr.



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vng ny c mt khu vc giao nhau. Nu mt vt cht v nnglng chn khng nm trong khu vc giao nhau ny th qu trnhgin n ca v tr s ban u s rt nhanh v sau chm dn. Hnhnh l lm pht l mt qui lut ca t nhin.

Trong chng ny, chng ta thy qu trnh tm hiu tnh cht ca

v tr rng ln bng khi nim lch s ca v tr trong thi gian odin ra nh th no. Ci v tr trong thi gian o l mt hnh cunh b v hi bt, n ging nh ci v ht ca Hamlet, tuy nhin, ciht ny li gii m c tt c mi th xy ra trong thi gian thc.Do vy, Hamlet hon ton ng. Chng ta b gii hn trong mt vht nhng vn coi mnh l cha t ca khong khng v tn.

Ta c th ti b giam trong mt v htV t coi mnh l cha t ca khong khng v tn...

- Shakespeare,Hamlet, hi 2, cnh 2



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