Chuong 1 Vu Tru Trong Vo Hat de - Smith.N Studio

8/3/2019 Chuong 1 Vu Tru Trong Vo Hat de - Smith.N Studio

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C hc lng t

Thuyt tng i rng

Mng 10 chiu

Cc siu dy

H enSiu hp dn 11 chiu

Cc mng-p

Thuyt-M

Smith Nguyen Studio.


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Trang 3

CHNG 1LC S V THUYT TNG I

Einstein thit lp hai l thuyt cn bn ca th k hai mi:L thuyt tng i rng v l thuyt lng t nh th no?



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

Trang 4 Ngi dch: [email protected]; http://datrach.blogspot.com

Albert Einstein, cha ca thuyt tng i hp v thuyttng i rng sinh ra Ulm, c vo nm 1879. Mt nmsau gia nh ng chuyn n Munich, ti , cha ng

Herman v cu ng Jacob khi s kinh doanh v in nhngkhng my thnh cng. Einstein khng phi l thn ng nhng cngi cho rng ng l mt hc sinh c bit ph thng th li lmt s cng iu. Nm 1894 cng vic lm n ca cha ng b b nn gia nh chuyn n Milan. Gia nh quyt nh ng nn li hon thnh bc hc ph thng, nhng ng khng thch ch

ngha c on ca trng hc nn ch sau my thng ng ont vi gia nh . Sau ng tt nghip ph thng Zurich vtt nghip i hc trng Bch khoa lin bang vo nm 1900. Bntnh hay tranh lun v v c cm vi quyn lc khng mang chong mt chn gio s trng Bch khoa lin bang v khng mtgio s no ca trng mi ng lm tr ging, m thi by gi l con ng bnh thng theo ui s nghip khoa hc. Cuicng th hai nm sau ng cng xoay s c mt vic Vn phngsng ch Bern. ng lm vic ti trong thi gian ng vit ba bibo, trong hai bi a ng tr thnh nh khoa hc hng u

th gii v bt u hai cuc cch mng v t tng lm thay ihiu bit ca chng ta v khng gian, thi gian v bn thn thc tivo nm 1905.

Gn cui th k th 19, cc nh khoa hc tin rng h gn nh mt v tr mt cch ton vn. H cho rng khng gian c lp ybi mt loi vt cht lin tc gi l -te (ether). nh sng v cctn hiu v tuyn l cc sng lan truyn trong -te ging nh sngm lan truyn trong khng kh. V tt c cc iu cn lm cho mtl thuyt hon thin l php o chnh xc xc nh tnh n hica -te. Thc ra cc php o nh th c xy dng hon chnhti phng th nghim Jefferson trng i hc Harvard m khngdng n mt ci inh st no trnh lm nhiu cc php o ttrng yu. Tuy vy nhng ngi xy dng h o qun rng ccvin gch nu xy nn phng th nghim v phn ln cc ta nh Harvard u cha mt lng ln st. Ngy nay cc ta nh vn c s dng, nhng h vn khng chc l nu khng c ccinh st th sn th vin ca trng c th nng c sc nngl bao nhiu.



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L C S V T H U Y T T N G I

Trang 5Ngi dch: [email protected]; http://datrach.blogspot.com

Albert Einstein nm 1920



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Vo cui th k 19, cc tng tri ngc nhau v s c mt ca-te bt u xut hin. Ngi ta tin rng nh sng chuyn ng vimt tc xc nh so vi -te v nu bn chuyn ng cng hngvi nh sng trong -te th bn s thy nh sng chuyn ng chmhn, v nu bn chuyn ng ngc hng vi nh sng th bn sthy nh sng di chuyn nhanh hn (hnh 1.1).

V mt lot cc th nghim chng minh iu tht bi.Albert Michelson v Edward Morley ca trng khoa hc ng dng Cleveland, bang Ohio thc hin cc th nghim cn thn vchnh xc nht vo nm 1887. H so snh tc nh sng ca haichm sng vung gc vi nhau. V tri t t quay quanh mnh vquay quanh mt tri nn dng c th nghim s di chuyn trong -tevi tc v hng thay i. Nhng Michelson v Morley cho thyrng khng c s khc bit gia hai chm sng . Hnh nh l nhsng truyn vi tc nh nhau i vi ngi quan st, khng phthuc vo tc v hng ca ngi chuyn ng (hnh 1.3).

Da trn th nghim Michelson-Morley, mt nh vt l ngi Ai-lentn l George Fitzgerald v nh vt l ngi H Lan tn l HendrikLorentz gi thit rng cc vt th chuyn ng trong -te s co liv thi gian s b chm i. S co v s chm li ca ng h lmcho tt c mi ngi s o c mt tc nh sng nh nhaukhng ph thuc vo vic h chuyn ng nh th no i vi -te (George Fitzgerald v Hendrik Lorentz vn coi -te l mt loivt cht c thc). Tuy vy, nm 1905, Einstein vit mt bi boch ra rng nu ngi ta khng th bit c ngi ta chuyn ng

(Hnh 1.1, pha trn)L THUYT -TE C NH

Nu nh sng l sng trong mtloi vt cht n hi c gil -te th vn tc ca nh sngi vi ngi trn tu v trchuyn ng ngc hng nh

sng (a) s nhanh hn vn tcca nh sng i vi ngi trongcon tu chuyn ng cng hngvi nh sng (b).

(Hnh 1.2, trang k) Ngi ta khng thy s khcbit v vn tc nh sng theo cchng trong mt phng qu oca tri t v hng vung gcvi mt phng qu o .

nh sng chuyn ng trong -te



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Tri t quay t ty sang ng nh sng vung gc vi quo ca tri t quanh mt tri

Cc tia sng vung gc vinhau v i theo chiu quay catri t cng khng th hin skhc nhau v vn tc



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(HNH 1.3) O VN TC NH SNG

Trong giao thoa k Michenson-Morley, nhsng t ngun sng c tch thnh hai chmbng mt gng bn m. Hai chm sng itheo hai hng vung gc vi nhau sau li kt hp thnh mt chm sng sau khi p

vo gng bn m mt ln na. S sai khcv tc nh sng ca hai chm sng i theohai hng c th lm cho cc nh sng cachm sng ny trng vi y sng ca chmsng kia v chng trit tiu nhau.

Hnh phi: s th nghim c v li t s c in trn tp ch Scientific Americannm 1887.



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trong khng gian hay khng th khi nim -te khng cn cn thitna. Thay vo , ng bt u bng mt gi thuyt rng cc nhlut khoa hc xut hin nh nhau i vi tt c nhng ngi quan

st chuyn ng t do. c bit l h s o c tc nh snhnh nhau khng ph thuc vo tc chuyn ng ca h. Tc ca nh sng c lp vi chuyn ng ca ngi quan st v nhnhau theo tt c cc hng.

tng ny i hi phi t b ngh cho rng tn ti mt i lngph qut c gi l thi gian c th o c bng tt c cc ngh. Thay vo , mi ngi c mt thi gian ring ca h. Thigian ca hai ngi s ging nhau nu hai ngi ng yn tngi vi nhau, nhng thi gian s khc nhau nu hai ngi chuynng tng i vi nhau.

Gi thuyt ny c khng nh bng rt nhiu th nghim, trong c mt th nghim gm hai ng h chnh xc bay theo hngngc nhau vng quanh tri t v quay li cho thy thi gian c sailch cht t. Gi thuyt gi rng nu ai mun sng lu hn thngi nn bay v hng ng v nh th th tc ca tri ts b sung vo tc ca my bay. Tuy vy, cc ba n trn mybay s rt ngn cuc sng ca bn gp nhiu ln mt phn nh cagiy m bn c c.

Bay t ty sang ng

Bay t ng sang ty

(Hnh 1.4)Mt phin bn v nghch l anhem sinh i (hnh 1.5) ckim tra bng thc nghim t

hai chic ng h chnh xc bayngc chiu nhau vng quanhtri t.Khi chng gp nhau th ng h bay v hng ng ghi lithi gian ngn hn cht t.

ng h trn phi c bayv hng ty ghi nhn mtkhong thi gian lu hnngi anh sinh i ca n

bay v hng ngc li

Thi gian ca cc hnh khchtrn phi c bay v hngng s ngn hn thi gianca nhng hnh khch trnphi c bay v hng ty



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Gi thuyt ca Einstein cho rng cc nh lut khoa hc xut hinnh nhau i vi tt c cc ngi quan st chuyn ng t do l cs ca thuyt tng i. Gi nh vy v n ng rng ch c chuynng tng i l quan trng. V p v s n gin ca gi thuytny thuyt phc rt nhiu cc nh t tng, tuy nhin, vn c rtnhiu cc kin tri ngc. Einstein vt b hai khi nim tuyti ca khoa hc th k 19: ng yn tuyt i i din l -te vthi gian tuyt i v ph qut m tt c cc ng h o c. Rtnhiu ngi thy rng y l mt khi nim khng bnh thng. Hhi, gi thuyt ng rng tt c mi thu tng i, rng khngc mt tiu chun o c tuyt i? S bt rt ny tip din trongsut nhng nm 20 v 30 ca th k 20. Khi Einstein c trao giiNobel vo nm 1921 v mt cng trnh km quan trng hn cngc ng cho ra i vo nm 1905. Lc , thuyt tng i khngc nhc n v n vn cn gy nhiu tranh ci (n by gi tivn nhn c vi ba bc th hng tun ni rng Einstein sai).Tuy vy, hin nay, cc nh vt l hon ton chp nhn thuyt tngi, v cc tin on ca n c kim chng trong v vn ngdng.

(Hnh 1.7)

(Hnh 1.5, trang trc) NGHCH L ANH EM SINH

ITrong thuyt tng i, mingi quan st s o thi giankhc nhau. iu ny c th dnn nghch l anh em sinh i(twin paradox).Mt ngi trong cp anh em sinhi (a) trong mt phi thuyn thmhim khng gian chuyn ngvi vn tc gn bng vn tc nhsng (c) trong khi ngi anh em

ca anh ta (b) vn trn mt t.V thi gian ca (a) trong phithuyn chm hn thi gian ca(b) trn tri t. Nn khi ngi(a) tr v (a2) anh ta s thyngi anh em ca anh ta trn trit (b2) gi hn anh ta.Mc d n c v chng li cmnhn chung ca chng ta, rtnhiu th nghim chng minhrng trong kch bn ny, ngidu hnh v tr s tr hn ngicn li.

(Hnh 1.6, hnh bn)Mt phi thuyn i ngang qua trit t tri sang phi vi vn tcbng bn phn nm vn tc nhsng. Mt xung nh sng pht rat cabin v phn x li u kia(a).Ngi trn tri t nhn nh sngtrn phi thuyn. V phi thuynchuyn ng nn hai ngi squan st khong cch m nhsng i c khi phn x likhng bng nhau(b).V vi h thi gian m nh sngdng truyn cng khng bngnhau, v theo gi thuyt ca Ein-stein, tc nh sng l nh nhaui vi tt c cc ngi quan stchuyn ng t do.



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Mt h qu quan trng ca thuyt tng i l h thc gia khilng v nng lng. Gi thit ca Einstein v tc ca nh sngl nh nhau i vi tt c cc ngi quan st ng rng khng cg c th chuyn ng nhanh hn nh sng. Nu ta dng nng lng gia tc mt vt no , d l mt ht hay mt tu v tr, th khilng ca vt s gia tng cng vi tc v do s kh c thgia tc thm c na. Ta khng th gia tc mt ht n tc nhsng v ta cn mt nng lng ln v cng lm iu . Khilng v nng lng l tng ng v iu c tng kt trong

mt phng trnh ni ting E = mc2

(hnh 1.7). C l y l phngtrnh vt l duy nht m chng ta c th nhn thy n c vit trnng ph. Mt trong s cc h qu ca phng trnh trn l htnhn ca nguyn t Uranium phn r thnh 2 ht nhn nh hn ctng khi lng nh hn khi lng ca ht nhn ban u, vic nys gii ta mt nng lng v cng ln (hnh 1.8).

Vo nm 1939, khi m kh nng mt cuc chin tranh th gii naang l m xut hin, mt nhm cc nh khoa hc nhn ra tm



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quan trng v thuyt phc Einstein vt qua s lng l ca bnthn in tn ca ng vo mt bc th gi Tng thng Rooseveltnhm thc gic Hoa K khi ng chng trnh nghin cu htnhn.

Vic ny dn n d n Manhattan v kt qu ca n l 2 qu bomnguyn t c nm xung Hiroshima v Nagasaki vo nm 1945.Mt s ngi ti cho Einstein v bom nguyn t bi v ng khm ph ra mi lin h gia khi lng v nng lng; nhng

iu ny ging nh l ti cho Newton gy ra cc v tai nnmy bay v pht hin ra nh lut hp dn.

Sau cc bi bo gy chn ng vo nm 1905, Einstein tr ln nitin trn th gii. Nhng n tn nm 1909 ng mi c mi volm vic ti trng i hc Zurich v do , ng c th t b cngvic vn phng sng ch Thy S. Hai nm sau, ng chuyn sangi hc c Prague, nhng ng quay tr li Zurich vo nm 1912,nhng ln ny ng v trng Bch khoa lin bang. Mc d ch

Bc th tin onca Einstein gitng thng Roos-evelt nm 1939

Trong thi gianbn thng qua,thng qua cc cngtrnh ca Joliot Php cng nhFermi v Szilard Hoa K, chng tac th xy dngmt phn ng ht

nhn vi mt khilng ln Urani-um, nh m sinhra mt ngun nnglng ln. Bygi, chng ta cth lm iu nytrong mt tnglai gn.Mc d cha chc

chn, nhng hintng mi ny ckh nng dn nvic to ra ccqu bom c sccng ph cc ln.



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ngha bi Do thi (anti-semitism) ang ph bin chu u, ngayc trong cc trng i hc, nhng ng vn l mt ti sn quca trng i hc. C nhiu ngh lm vic n t Vienna vUtrecht, nhng ng chp nhn mt v tr Vin hn lm khoa

hc Prussian Berlin v ng khng phi m nhim cng vicging dy. ng chuyn n Berlin vo thng 4 nm 1914 v sau t lu v v hai con ca ng cng chuyn n vi ng. Cuchn nhn ca ng gp nhiu sng gi, do vy, v v cc con ngnhanh chng tr li Zurich. Mc du thnh thong ng vn tr lithm h nhng cui cng cuc hn nhn ca h cng tan v. Sau Einstein ly mt ngi em h tn l Elsa sng Berlin. Trongnhng nm chin tranh ng sng c thn v khng c rng bucv gia nh, c l chnh v th y l thi k thng hoa nht ca ngv mt khoa hc.

Mc du thuyt tng i rt ph hp vi cc nh lut in v tnhng n li khng tng hp vi nh lut hp dn ca Newton.nh lut ca Newton ni rng nu mt lng vt cht trong mtvng ca khng gian b thay i th trng hp dn m n to ratrong ton v tr cng thay i ngay lp tc. iu ny c ngha lngi ta c th gi cc tn hiu nhanh hn nh sng (mu thun vithuyt tng i); hiu tc thi c ngha l g, ngi ta li cnn khi nim thi gian tuyt i v ph qut, chnh iu ny liloi b thi gian c nhn.

Uranium (U-235)

Neutron (n) bn ph ht nhn

Uranium (U-236)

(U-235) Ht nhnt hp dao ngv bt n nh

(Ba-144) Ht nhnt hp dao ng v

bt n nh

Tia gamma

(n)

(Hnh 1.8) NNG LNG LIN KTHT NHN

Ht nhn c to thnh tproton v neutron lin kt vinhau nh lc ht nhn mnh. Nhng khi lng ca htnhn lun nh hn tng khilng ca cc proton v neu-tron ring l to nn chng. Skhc nhau chnh l mt php onng lng lin kt ht nhnm gi ht nhn li vi nhau.Nng lng lin kt ny c thc tnh t h thc Einstein:nng lng lin kt ht nhn =mc2 trong m l s khcnhau gia khi lng ht nhnv tng cc thnh phn.

N gii thot mt lng nnglng to nn mt sccng ph khng l.

(n)



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(Kr-89) Ht nhnt hp dao ngv bt n nh

Tia gamma

(n)

Tnh trung bnh, phn rthu c 2,4 neutron vnng lng 215 MeV

Neutron (n) c th khing mt phn ng dytruyn

Phng trnh Einstein gianng lng (E), khi lng(m), v vn tc nh sng (c)

cho thy mt lng nh khilng tng ng vi mtnng lng khng l: E=mc2

Neutron lin kt

Proton

Neutron t do

PHN NG DY TRUYNMt neutron t phn r U-235 ban u sbn ph cc ht nhn khc. Qu trnh nyto ra mt phn r ht nhn khc v mtphn ng dy truyn gm cc va chmtip theo bt uNu phn ng ny t duy tr th n cgi l ti hn v khi lng U-235c gi l khi lng ti hn.



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Nm 1907, Einstein nhn ra kh khn ny khi ng cn lm vic vn phng sng ch Bern, nhng phi n khi ng Prague

vo nm 1911 ng mi suy ngh v vn ny mt cch nghimtc. ng nhn ra rng c mt mi lin h mt thit gia gia tc vtrng hp dn. Mt ngi no trong mt ci hp ng kn nhl trong mt ci thang my chng hn khng th nhn bit c cihp ang ng yn trong trng hp dn ca tri t hay ang bgia tc bi mt tn la trong khng gian (tt nhin lc ny l trck nguyn ca Star Trek, v Einstein ngh v nhng ngi ngtrong thang my hn l v nhng con tu v tr). Nhng ngi takhng th gia tc hoc ri t do lu c trong ci thang my trckhi tai nn xy ra! (hnh 1.9)

(Hnh 1.9)

Mt ngi quan st ng trongmt ci hp khng th nhn ras khc nhau khi ng trong mtchic thang my tnh trn tri t(a) hoc b gia tc bi mt tn latrong khng gian t do (b).Nu ngi ta tt ng c ca tnla (c) cm gic s ging nhtrong mt chic thang my ri tdo xung t.



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Nu tri t phng th ta c th ni rng qu to ri xung uNewton l do hp dn hoc Newton v b mt tri t b gia tc ln

trn, hai cch ni trn l tng ng (hnh 1.10). S tng nggia gia tc v hp dn khng s cn ng khi tri t l hnh cu,tuy vy- ngi mt kia tri t c th b gia tc theo cc chiungc li nhng vn ng nhng khong cch khng i vinhau (hnh 1.11).

Nhng khi ng quay li Zurich vo nm 1912, ng c mt bct ph khi nhn ra rng s tng ng l ng nu hnh dng cakhng thi gian b b cong ch khng thng nh ngi ta vn nghcho ti thi im y. tng ca ng l khi lng v nng lng

Hnh (1.10)

Hnh (1.11)

(Hnh 1.12) CONG CAKHNG THI GIAN

Gia tc v hp dn ch c thtng ng vi nhau nu mtvt th c khi lng ln b congkhng thi gian, do b congc l trnh ca cc vt th xungquanh n.



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Nu tri t phng (hnh 1.10)th ngi ta c th gii thch bng mt trong hai cch tngng sau: qu to ri xung u

Newton do lc hp dn hoc doNewton gia tc ln pha trn. Stng ng ny khng cn ngkhi tri t hnh cu (hnh 1.11)v nhng ngi mt kia ca trit s ri xa nhau. Einstein gii quyt bi ton ny bng vicgi thit khng gian v thi gianb cong.

lm cong khng thi gian theo mt cch c th xc nh c.Cc vt th nh l qu to hoc l hnh tinh s c gng chuyn ngthng trong khng thi gian, nhng qu o ca chng s b b congbi mt trng hp dn do khng thi gian b cong (hnh 1.12).

Vi s gip ca Marcel Grossmann, Einstein nghin cu lthuyt khng gian v mt phng cong do Georg Friedrich Riemannpht trin trc . Tuy vy, Riemann ngh rng ch c khng gianb b cong. iu lm cho Einstein ngh rng khng thi giancng b b cong. Einstein v Grossmann vit chung mt bi bovo nm 1913, trong h y tng m chng ta ngh v lchp dn ch l nhng biu hin ca s cong ca khng thi gian.Tuy vy, v mt sai lm do Einstein gy ra (Einstein cng rt con



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ngi v c th nhm ln), h khng th tm ra cc phng trnhlin h cong ca khng gian vi khi lng v nng lng trong. Einstein vn tip tc nghin cu vn ny Berlin, khng

b nh hng bi cc vn gia nh v ch yu l khng b nhhng bi chin tranh, cho n khi ng tm thy cc phng trnh vo thng 11 nm 1915. ng trao i cc tng ca ngvi nh ton hc David Hilbert trong chuyn thm trng i hcGottingen vo ma h nm 1915, v Hilbert cng tm ra cc phngtrnh tng t mt cch c lp trc Einstein vi ngy. Tuy nhin,ngay c bn thn Hilbert cng tha nhn, tc quyn ca l thuytmi l thuc v Einstein. tng lin h hp dn vi cong cakhng thi gian chnh l ca ng. y cng l mt li khen chonc c vo thi im khi cc cuc trao i v tho lun khoa

hc c th din ra m khng b nh hng bi chin tranh. iu nyhon ton tri ngc vi k nguyn c quc x (Nazi) 20 nmsau .

L thuyt mi v s cong ca khng thi gian c gi l thuyttng i rng phn bit vi l thuyt ban u khng c lc hpdn c mi ngi bit n vi ci tn l thuyt tng i hp. Lthuyt ny c khng nh trong mt th nghim rt n tng vonm 1919, trong mt cuc thm him ca cc nh khoa hc ngiAnh v pha Ty chu Phi quan st c lch rt nh ca nh



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(Hnh 1.13) NH SNG B B CONG

nh sng t cc ngi sao i n gn mt tri lch hng do khi lng ca mt tri lm cong khng thi gian(a). iu ny lm dch chuyn v tr biu kin ca ngi sao khi nhn t tri t (b). Hin tng ny c th quanst khi nht thc.



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sng n t mt ngi sao i gn mt tri trong qu trnh nht thc(hnh 1.13). y l mt bng chng trc tip cho thy rng khngthi gian b b cong, v n khch l s thay i ln nht ca conngi trong nhn thc ca chng ta v v tr m chng ta ang sngt khi Euclid vit cun sch Hnh hc c svo khong 300 nmtrc Cng nguyn.

Thuyt tng i rng ca Einstein bin khng thi gian t vaitr l mt khung nn th ng trong cc hin tng xy ra trthnh mt tc nhn ch ng trong chuyn ng ca v tr. iu dn ti mt bi ton rt ln v l mi quan tm hng u ca vtl th k 20. V tr trn y vt cht v vt cht b cong khngthi gian theo mt cch lm cho cc vt th ri vo nhau. Einsteinthy rng cc phng trnh ca ng khng c nghim m t mt vtr tnh ti v khng thay i theo thi gian. Thay v vic t b mtv tr vnh cu m ng v phn ln nhng ngi khc tin, ng thm vo mt s hng gi l hng s v tr mt cch khin cng.

Hng s ny lm cong khng thi gian theo hng ngc li, do, cc vt th s chuyn ng ra xa nhau. Hiu ng y ca hngs v tr c th cn bng vi hiu ng ht ca vt cht, cho phpng thu c mt v tr tnh ti. y l mt trong nhng c mayb mt ng tic nht trong vt l thuyt. Nu Einstein dng li cc phng trnh ban u ca ng, ng c th tin on rng vtr s gin n hoc co li. Kh nng v tr thay i theo thi gianch c xem xt mt cch nghim tc cho n khi c c nhngquan st thu c t knh thin vn 2,5 m t trn nh Wilson vonhng nm 1920.

Nhng quan st ny cho thy rng cc thin h cng xa nhauth chuyn ng ra xa nhau cng nhanh. V tr ang gin n vikhong cch gia 2 thin h tng dn theo thi gian (hnh 1.14).Pht hin ny loi b s c mt ca hng s v tr c cmt v tr tnh. Sau ny Einstein ni rng hng s v tr l sai lmln nht ca i ng. Tuy vy, ngy nay, ngi ta thy rng hng sv tr hon ton khng phi l mt sai lm: nhng quan st gn ys c m t trong chng 3 gi rng thc ra l c mt hng sv tr c gi tr rt nh.



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Thuyt tng i rng thay i hon ton vic bn lun ngungc v s phn ca v tr. Mt v tr tnh ti c th tn ti mi mihoc c th c to ra vi hnh dng hin nay ca n ti mt thiim trong qu kh. Tuy vy, nu by gi cc thin h ang ri xanhau, iu c ngha l trong qu kh chng tng rt gn nhau.Khong 15 t nm trc y, chng tng chp li vi nhau vmt rt ln. Trng thi ny c mt linh mc Cng gio tn lGeorges Lemaitre, ngi u tin nghin cu v ngun gc ca v

tr gi l nguyn t nguyn thy m ngy nay chng ta gi l vn ln.

Dng nh Einstein cha bao gi nghin cu v n ln mt cchnghim tc. R rng l ng ngh rng m hnh n gin v v trgin n ng nht s khng ng nu ngi ta theo di chuynng ca cc thin h trong qu kh v rng cc vn tc bin cacc thin h c th lm cho chng khng chm vo nhau. ng nghrng trc v tr pha co li v trt qua nhau chuyn sangpha dn n hin nay vi mt mt trung bnh. Tuy vy, by gi

(Hnh 1.14)

Quan st v cc thin h ch rarng v tr ang gin n: khongcch gia hu ht cc cp thinh ang gia tng.



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chng ta bit rng cho cc phn ng ht nhn trong v tr banu to ra mt lng ln cc nguyn t nh m chng ta quan stc xung quanh, th mt cn phi ln hn 0,64 tn/cm3 v nhit phi trn mt t . Hn na cc quan st v phng vi sng chra rng c th mt t n 1026 tn/cm3. Ngy nay chng ta bitrng thuyt tng i rng cua Einstein khng cho php v tr trtqua nhau n pha dn n hin ti. Nh s c tho lun trongchng 2, Roger Pensose v ti c th ch ra rng thuyt tng

i rng tin on v tr bt u bng mt v n ln. Do , lthuyt ca Einstein tin on rng thi gian, c s khi u mc dng khng thch tng ny cho lm.

Thm ch Einstein cn min cng hn tha nhn rng thuyt tngi rng tin on thi gian s kt thc i vi cc ngi sao nngkhi chng giai on cui ca cuc i v khi chng khng cn nhit lng cn bng vi lc hp dn ca bn thn chng. Lchp dn ny ang c lm chng nh i. Einstein ngh rng, cc ngisao nh vy s kt thc cuc i mt trng thi cui cng, nhng

Knh vin vng 100-inch ti iquan st Mount Wilson.



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ngy nay chng ta bit rng s khng c trng thi cui cng chocc ngi sao c khi lng ln hn hai ln khi lng mt tri. Ccngi sao nh vy s tip tc co li cho n khi chng tr thnh cch en, nhng vng m khng thi gian b b cong n ni nh sngkhng th thot ra khi c (hnh 1.15).

Penrose v ti cho thy rng thuyt tng i rng tin on thigian s kt thc trong mt h en, i vi bn thn ngi sao vi vi mt nh du hnh v tr khng may b ri vo n. Nhng

c im khi u v kt thc ca thi gian l nhng ni m ccphng trnh ca thuyt tng i rng khng th c xc nh.Do , l thuyt khng tin on c ci g tham gia v n ln.Mt s ngi thy rng y l biu hin cho t do ca Cha sngto th gii theo bt k cch no m ngi mun, nhng nhng ngikhc (trong c ti) cm thy rng s khi u ca v tr cngc iu khin bi cc nh lut khoa hc m iu khin v trti cc thi im sau khi v tr hnh thnh. Chng ta t cmt s tin b trong vn ny, nh s c m t trong chng 3,nhng chng ta vn cha hiu hon ton ngun gc ca v tr.

L do m thuyt tng i khng cn ng ti thi im v n lnl thuyt tng i khng tng hp c vi l thuyt lng t,mt cuc cch mng khc v t tng vo thi im u th k 20.Bc u tin ti thuyt lng t c thc hin vo nm 1900, khiMax Plank Berlin khm ph ra rng bc x pht ra t cc vt thnng c th c gii thch nu nh sng ch c th c phtra hoc b hp th theo nhng lng ri rc c gi l cc lngt (quanta). Mt trong s cc bi bo cch mng ca ng c vitnm 1905, khi ng cn lm vic vn phng sng ch, Einstein chng minh rng gi thuyt lng t ca Plank c th gii thch mthiu ng gi l hiu ng quang in, trong hiu ng ny, cc kimloi s pht ra cc in t khi b nh sng chiu vo. Hiu ng l lc s ca cc u thu nh sng v v tuyn, v cng nh cng trnhny Einstein c trao gii Nobel vt l.

Einstein tip tc nghin cu l thuyt lng t cho n nhng nm1920, nhng ng rt bn khon v cng trnh ca Heisenberg Copenhagen, Paul Dirac Cambridge v Erwin Schrodinger Zurich, l nhng ngi pht trin mt bc tranh mi v thc

(Hnh 1.15, trang k)

Mt ngi sao ln cn kitnguyn liu ht nhn s mt inhit lng v co li. congca khng gian s tr ln ln nmc to ra mt h en m nhsng khng th thot ra c.Thi gian kt thc trong lng hen.



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1)Ngi sao ang t chy nhinliu ht nhn lm cong khngthi gian xung quanh n.

2)Khi ngi sao co lith cong tng ln

3)Thi gian s kt thctrong mt h en.



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ti c gi l c hc lng t. Nhng ht t hon khng cn c vtr v tc chnh xc na. Thay vo , nu ngi ta xc nh v trca ht cng chnh xc bao nhiu th ngi ta cng kh xc nh vntc ca n by nhiu v ngc li. Einstein rt kh chu v nhngyu t ngu nhin, bt nh trong cc nh lut c bn v ng chabao gi chp nhn hon ton c hc lng t. Suy ngh ca ngc th hin trong cu chm ngn Cha khng chi tr xc sc.Tuy vy, phn ln cc nh khoa hc chp nhn tnh ng n cal thuyt lng t mi ny bi v chng gii thch c mt lot

cc hin tng kh hiu trc v rt ph hp vi cc quan st.Cc quy lut lng t l c s cho s pht trin ca ha hc, sinhhc phn t, v in t hin i v l c s cho nn cng ngh thay i th gii trong 50 nm qua.

Thng 12 nm 1932, nhn thy c quc x v Hitler sp ln nmquyn, Einstein ri nc c v 4 thng sau ng t b quyncng dn ginh trn 20 nm cuc i cn li ca mnh cho Vinnghin cu cp cao Princeton, bang New Jersey.

c, ng Quc x tin hnh mt chin dch chng li khoahc Do thi v v rt nhiu cc nh khoa hc c l ngi Do thi,nn y cng l mt nguyn nhn lm cho ngi c khng chto c bom nguyn t. Einstein v thuyt tng i ca ng li tng chnh ca chin dch ny. Khi c hi v mt cun schc xut bn vi tiu 100 tc gi chng li Einsteinth ng trli: Ti sao li mt trm? Nu ti sai th mt cng . Sau thchin hai, ng thc gic cc nc ng minh thit lp mt t chcquc t kim sot bom nguyn t. Nm 1948, ng c mi lmtng thng ca nh nc Israel non tr nhng ng t chi. Mtln ng ni: Chnh tr l nht thi, ch c cc phng trnh mi lvnh cu. Cc phng trnh thuyt tng i ca Einstein l tmbia ghi nhn cng lao ca ng. Chng s tn ti mi mi cng vtr.

Trong vi trm nm qua, th gii thay i nhiu hn bt k thk no trc . Nguyn nhn khng phi l cc thnh tu v kinht hay chnh tr m l s pht trin vt bc v cng ngh c xydng trn nn khoa hc c bn. Vy th ai xng ng l biu tngcho s tin b hn Einstein?

Albert Einstein cng con ri m phng chnh ng ngay sau khin Hoa K nh c lu di.



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