,f ,,newton to ,,e9/e9 ,*ang+ ,conceptions ( ,,! ,,univ]se ,,by ,,b5jam9 ,,h>r[1 ,ph4,d4 ,,second ,,edition1 ,,revis$ ,,& ,,enl>g$ ,) ,articles by ,pr(4 ,e9/e91 ,pr(4 ,j4 ,s4 ,ames 7,johns ,hopk9s71 ,sir ,frank ,dyson 7,a/ronom] ,royal71 ,pr(4 ,a4 ,s4 ,edd+ton 7,cambridge7 & ,sir ,j4 ,j4 ,?omson 7,presid5t ( ! ,royal ,society7 ,portraits & ,illu/rations ,,new ,,york ,d4 ,,van ,,no/r& ,,company ,eight ,w>r5 ,/reet #aibj ,,preface ,e9/e9's contributions to our ideas ( "t & space1 & to our k ( ! univ]se 9 g5]al1 are ( s mom5t\s a nature1 t !y easily take _! place among ! two or ?ree greate/ a*ievem5ts ( ! tw5tie? c5tury4 ,?is little book attempts to give1 9 popul> =m1 an acc\nt ( ?is "w4 ,z1 h[ev]1 ,e9/e9's "w is s l>gely dep5d5t ^u ! "w ( ,newton & ,newton's successors1 ! fir/ two *apt]s are devot$ to ! latt]4 ,b4 ,h4 ,,preface ,,to ,,second ,,edition ,! prep>ation ( ?is new edition has made x possible to correct errors1 to fur!r amplify c]ta9 portions ( ! text & to enl>ge ! ev]-increas+ bibliography on ! subject4 ,photographs ( ,pr(essors ,j4 ,j4 ,?omson1 ,mi*elson1 ,m9k[ski & ,lor5tz are also new features 9 ?is edition4 ,! explanatory notes & articles 9 ! ,app5dix w1 ,i believe1 pres5t no difficulties to read]s :o h ma/]$ ! cont5ts ( ! book4 ,!y are 9 fact popul> expositions ( v>i\s phases ( ! ,e9/e9 !ory2 b exp]i5ce has %[n t ev5 popul> expositions ( ! !ory ne$ fur!r popul> introductions4 ,i wi% to take ?is opportunity ( ?ank+ ,pr(4 ,e9/e91 ,pr(4 ,a4 ,a4 ,mi*elson ( ! ,univ]sity ( ,*icago1 ,pr(4 ,j4 ,s4 ,ames ( ,johns ,hopk9s ,univ]sity1 & ,pr(essor ,g4 ,b4 ,pegram ( ,columbia ,univ]sity = help 9 v>i\s ways :i* !y 7 good en\gh to ext5d to me4 ,pr(4 ,j4 ,s4 ,ames & ! editor ( ,sci5ce h be5 k9d en\gh to all[ me to repr9t ! =m]'s excell5t presid5tial address on ,e9/e9's !ory1 deliv]$ be=e ! memb]s ( ! ,am]ican ,physical ,society4 ,b4 ,h4 ,,table ,,( ,,cont5ts ,,page ,i4 ,newton #a ,,ii4 ,! ,e!r & ,its ,consequ5ces #bg ,,iii4 ,e9/e9 #da ,,iv4 ,app5dix #ha ,"t1 ,space & ,gravitation1 by ,pr(4 ,e9/e9 #hh ,e9/e9's ,law ( ,gravitation1 by ,pr(4 ,j4 ,s4 ,ames #ic ,! ,deflection ( light by ,gravitation & ! ,e9/e9 ,!ory ( ,relativity1 by ,sir ,frank ,dyson1 ,pr(4 ,a4 ,s4 ,edd+ton & ,sir ,j4 ,j4 ,?omson #aab ,,newton ,newton 0 ! greate/ g5ius t ev] exi/$4--,lagrange1 "o ( ! greate/ ( ,fr5* ma!maticians4 ,! ef=ts ( ! great philosoph] 7 always sup]human2 ! que/ions :i* he did n solve 7 incapable ( solution 9 8 "t4--,arago1 fam\s ,fr5* a/ronom]4 ,,e9/e9 ,?is is ! mo/ important result obta9$ 9 connection ) ! !ory ( gravitation s9ce ,newton's day4 ,e9/e9's reason+ is ! result ( "o ( ! highe/ a*ievem5ts ( human ?\ght4--,sir ,j4 ,j4 ,?omson1 presid5t ( ! ,briti% ,royal ,society & pr(essor ( physics at ! ,univ]sity ( ,cambridge4 ,x surpasses 9 boldness ev]y?+ previ\sly sugge/$ 9 speculative natural philosophy & ev5 9 ! philosophical !ories ( k4 ,! revolution introduc$ into ! physical conceptions ( ! _w is only to be comp>$ 9 ext5t & dep? ) t br\ght ab\t by ! introduction ( ! ,cop]nican sy/em ( ! univ]se4--,pr(4 ,max ,planck1 pr(essor ( physics at ! ,univ]sity ( ,b]l9 & w9n] ( ! ,nobel ,prize4 ,i ,,newton ,9 speak+ ( ,newton we are tempt$ to p>aphrase a l9e f ! ,scriptures3 ,be=e ,newton ! ,sol> ,sy/em 0 )\t =m1 & void2 !n ,newton came & !re 0 light4 ,to h discov]$ a law n only applicable to matt] on ?is e>?1 b to ! planets & sun & />s beyond1 is a triumph :i* places ,newton among ! sup]-m54 ,:at ,newton's law ( gravitation mu/ h meant to ! p ( 8 day c be pictur$ only if we conceive :at ! effect ^u u w\ld be if someone--say ,m>coni--7 actually to succe$ 9 gett+ into t\* ) be+s on ano!r planet4 ,newton's law increas$ confid5ce 9 ! univ]sality ( e>?ly laws2 & x /r5g!n$ belief 9 ! cosmos z a law-abid+ me*anism4 ,newton's ,law4 ,! attraction betwe5 any two bodies is proportional to _! masses & inv]sely proportional to ! squ>e ( ! di/ance t sep>ates !m4 ,?is is ! conc5trat$ =m ( ,newton's law4 ,if we apply ?is law to two su* bodies z ! sun & ! e>?1 we c /ate t ! sun attracts ! e>?1 & ! e>?1 ! sun4 ,fur!rmore1 ?is attractive p[] w dep5d ^u ! di/ance betwe5 ^! two bodies4 ,newton %[$ t if ! di/ance betwe5 ! sun & ! e>? 7 d\bl$ ! attractive p[] w\ld be r$uc$ n to "o-half1 b to "o-f\r?2 if trebl$1 ! attractive p[] w\ld be r$uc$ to "o-n9?4 ,if1 on ! o!r h&1 ! di/ance 7 halv$1 ! attractive p[] w\ld be n m]ely twice1 b f\r times z great4 ,& :at is true ( ! sun & ! e>? is true ( e body 9 ! firmam5t1 &1 z ,pr(essor ,ru!r=d has rec5tly %[n1 ev5 ( ! bodies :i* make up ! sol> sy/em ( ! almo/ inf9itesimal atom4 ,?is my/]i\s attractive p[] t "o body possesses = ano!r is call$ gravitation1 & ! law :i* regulates ! motion ( bodies :5 "u ! spell ( gravitation is ! law ( gravitation4 ,?is law we owe to ,newton's g5ius4 ,newton's ,pr$ecessors4 ,we c be/ appreciate ,newton's mom5t\s contribution to a/ronomy by ca/+ a rapid glance ov] ! /ate ( ! sci5ce prior to ! sev5te5? c5tury--t is1 prior to ,newton's day4 ,ptolemy's conception ( ! e>? z ! c5t] ( ! univ]se held undisput$ sway ?r\gh\t ! middle ages4 ,9 ^? days ,ptolemy 0 9 a/ronomy :at ,ari/otle 0 9 all o!r k3 !y 7 ! gods :o c\ld n b be "r4 ,did n ,ari/otle say t e>?1 air1 fire & wat] con/itut$ ! f\r elem5ts8 ,did n ,ptolemy say t ! e>? 0 ! c5t] ar\nd :i* ! sun revolv$8 ,:y1 !n1 "q fur!r8 ,que/ion+ 0 a sacrilege4 ,cop]nicus 7#adgc-aedc71 h[ev]1 did "q4 ,he /udi$ mu* & ?\ght mu*4 ,he devot$ 8 :ole life to ! inve/igation ( ! movem5ts ( ! heav5ly bodies4 ,& he came to ! conclusion t ,ptolemy & 8 foll[]s 9 succe$+ ages _h exp\nd$ views :i* 7 diametrically oppos$ to ! tru?4 ,! sun1 said ,cop]nicus1 did n move at all1 b ! e>? did2 & f> f ! e>? be+ ! c5t] ( ! univ]se1 x 0 b "o ( sev]al planets revolv+ ar\nd ! sun4 ,! influ5ce ( ! *ur*1 c\pl$ ) man's incl9ation to exalt 8 own importance1 /rongly t5d$ aga9/ ! acceptance ( su* het]odox views4 ,among ! _m ho/ile critics ( ! ,cop]nican sy/em1 ,ty*o ,brahe 7#aedf-afja7 /&s out pre-em95tly4 ,?is consci5ti\s obs]v] bitt]ly assail$ ,cop]nicus = 8 sugge/ion t ! e>? mov$1 & develop$ a s*eme ( 8 own :i* po/ulat$ t ! planets revolv$ ar\nd ! sun1 & planets & sun 9 turn revolv$ ar\nd ! e>?4 ,! majority applaud$ ,ty*o2 a small1 v small gr\p ( insurg5ts _h fai? 9 ,cop]nicus4 ,! illu/ri\s ,galileo 7#aefd-afdb7 belong$ to ! m9ority4 ,! telescope ( 8 inv5tion unfold$ a view ( ! univ]se :i* beli$ ! ass]tions ( ! _m1 & /r5g!n$ 8 belief 9 ! ,cop]nican !ory4 ,x 7! ,cop]nican !ory7 expla9s to me ! cause ( _m ph5om5a :i* "u ! g5]ally accept$ !ory are q un9telligible4 ,i h collect$ argum5ts = refut+ ! latt]1 b ,i d n v5ture to br+ !m to publication4 ,s wrote ,galileo to 8 fri5d1 ,kepl]4 ,i d n v5ture to br+ !m to publication4 ,h[ significant ( ! times--( any "t1 "o v5tures to add4 ,galileo did ov]come 8 hesitancy & publi%$ 8 views4 ,!y ar\s$ a /orm4 ,look ?r\gh my telescope1 he plead$4 ,b ! pr(essors w\ld n2 nei!r w\ld ! body ( ,inquisitors4 ,! ,inquisition condemn$ him3 ,! proposition t ! sun is 9 ! c5t] ( ! e>? & immovable f its place is absurd1 philosophically false & =mally h]etical2 because x is expressly contr>y to ! ,holy ,scriptures4 ,& poor ,galileo 0 made to utt] words :i* 7 z f> remov$ f 8 ?\ghts z 8 oppressors' ideas 7 f ! tru?3 ,i abjure1 curse & dete/ ! said errors & h]esies4 ,! tru? w out4 ,o!rs arose :o defi$ ! majority & ! p[]ful ,inquisition4 ,mo/ prom95t ( all ( ^! 0 ,galileo's fri5d1 ,kepl]4 ,?\gh a /ud5t ( ,ty*o1 ,kepl] did n hesitate to esp\se ! ,cop]nican sy/em2 b 8 adoption ( x did n mean unqualifi$ approval4 ,kepl]'s criticism 0 p>ticul>ly direct$ aga9/ ! ,cop]nican !ory t ! planets revolve 9 circles4 ,?is 0 boldness 9 ! extreme4 ,ev] s9ce ,ari/otle's disc\rse on ! circle z a p]fect figure1 x 0 tak5 = grant$ t motion 9 space 0 circul>4 ,nature is p]fect2 ! circle is p]fect2 h5ce1 if ! sun revolves1 x revolves 9 circles4 ,s /rongly 7 m5 imbu$ ) ?is p]fection1 t ,cop]nicus himself fell victim4 ,! sun no long] mov$1 b ! e>? & ! planets did1 & !y mov$ 9 a circle4 ,radical z ,cop]nicus 01 a few atoms ( cons]vatism rema9$ ) him /ill4 ,n s ,kepl]4 ,ty*o _h taught him ! importance ( c>eful obs]vation1--to su* good effect1 t ,kepl] came to ! conclusion t ! revolution ( ! e>? ar\nd ! sun takes ! =m ( an ellipse r ?an a circle1 ! sun be+ /ation$ at "o ( ! foci ( ! ellipse4 ,to picture ?is ellipse1 we %all ask ! read] to /ick two p9s a %ort di/ance ap>t into a piece ( c>dbo>d1 & to place ov] ! p9s a loop ( /r+4 ,) ! po9t ( a p5cil draw ! loop taut4 ,z ! p5cil moves ar\nd ! two p9s ! curve s produc$ w be an ellipse4 ,! positions ( ! two p9s repres5t ! two foci4 ,kepl]'s obs]vation ( ! elliptical rotation ( ! planets 0 ! fir/ ( ?ree laws1 quantitatively express$1 :i* pav$ ! way = ,newton's law4 ,:y did ! planets move 9 j ?is way8 ,kepl] tri$ to answ] ?is also1 b fail$4 ,x rema9$ = ,newton to supply ! answ] to ?is "q4 ,newton's ,law ( ,gravitation4 ,! ,great ,plague ( #afff drove ,newton f ,cambridge to 8 home 9 ,l9coln%ire4 ,!re1 accord+ to ! celebrat$ leg5d1 ! philosoph] sitt+ 9 8 little g>d5 "o f9e aft]noon1 fell into a deep rev]ie4 ,?is 0 int]rupt$ by ! fall ( an apple1 & ! ?9k] turn$ 8 att5tion to ! apple & its fall4 ,x mu/ n be suppos$ t ,newton discov]$ gravity4 ,apples _h be5 se5 to fall be=e ,newton's "t1 & ! reason = _! return to e>? 0 correctly attribut$ to ?is my/]i\s =ce ( attraction possess$ by ! e>?1 to :i* ! "n gravity _h be5 giv54 ,newton's great triumph consi/$ 9 %[+ t ?is gravity1 :i* 0 suppos$ to be a peculi> prop]ty resid+ 9 ! e>?1 0 a univ]sal prop]ty ( matt]2 t x appli$ to ! moon & ! sun z well z to ! e>?2 t1 9 fact1 ! motions ( ! moon & ! planets c\ld be expla9$ on ! basis ( gravitation4 ,b 8 supreme triumph 0 to give1 9 "o sublime g5]alization1 quantitative expression to ! motion regulat+ heav5ly bodies4 ,let u foll[ ,newton 9 8 tra9 ( ?\ght4 ,an apple falls f a tree #ej y>ds high4 ,x w\ld fall f a tree #ejj y>ds high4 ,x w\ld fall f ! highe/ m\nta9 top sev]al miles above sea level4 ,x w\ld probably fall f a height mu* above ! m\nta9 top4 ,:y n8 ,probably ! fur!r up y g ! less does ! e>? attract ! apple1 b at :at di/ance does ?is attraction /op entirely8 ,! ne>e/ body 9 space to ! e>? is ! moon1 "s #bdj1jjj miles away4 ,w\ld an apple rea* ! e>? if ?r[n f ! moon8 ,b p]haps ! moon itself has attractive p[]8 ,if s1 s9ce ! apple w\ld be mu* ne>] ! moon ?an ! e>?1 ! probabilities are t ! apple w\ld nev] rea* ! e>?4 ,b hold6 ,! apple is n ! only object t falls to ! gr\nd4 ,:at is true ( ! apple is true ( all o!r bodies--( all matt]1 l>ge & small4 ,n[ !re is ! moon itself1 a v l>ge body4 ,does ! e>? ex]t any gravitational pull on ! moon8 ,to be sure1 ! moon is _m ?\s&s ( miles away1 b ! moon is a v l>ge body1 & p]haps ?is size is 9 "s way relat$ to ! p[] ( attraction8 ,b !n if ! e>? attracts ! moon1 :y does n ! moon fall to ! e>?8 ,a glance at ! accompany+ figure w help to answ] ?is "q4 ,we mu/ rememb] t ! moon is n /ation>y1 b travell+ at trem5d\s spe$--s mu* s1 t x circles ! entire e>? e mon?4 ,n[ if ! e>? 7 abs5t ! pa? ( ! moon w\ld be a /raight l9e1 say ,,mb4 ,if1 h[ev]1 ! e>? ex]ts attraction1 ! moon w\ld be pull$ inw>d4 ,in/ead ( foll[+ ! l9e ,,mb x w\ld foll[ ! curv$ pa? ,,mb'4 ,& aga91 ! moon hav+ arriv$ at ,b'1 is prev5t$ f foll[+ ! l9e ,b',c1 b r ,b',c'4 ,s t ! pa? in/ead ( be+ a /raight l9e t5ds to become curv$4 ,f ,kepl]'s rese>*es ! probabilities 7 t ?is curve w\ld assume ! %ape ( an ellipse r ?an a circle4 ,! only reason1 !n1 :y ! moon does n fall to ! e>? is on acc\nt ( its motion4 ,7 x to /op mov+ ev5 = ! fraction ( a second x w\ld come /raight d[n to u1 & probably few w\ld live to tell ! tale4 ,newton reason$ t :at keeps ! moon revolv+ ar\nd ! e>? is ! gravitational pull ( ! latt]4 ,! next important /ep 0 to discov] ! law regulat+ ?is motion4 ,"h ,kepl]'s obs]vations ( ! movem5ts ( ! planets ar\nd ! sun 0 ( ine/imable value2 = f ^! ,newton d$uc$ ! hypo!sis t attraction v>ies inv]sely z ! squ>e ( ! di/ance4 ,mak+ use ( ?is hypo!sis1 ,newton calculat$ :at ! attractive p[] possess$ by ! e>? mu/ be 9 ord] t ! moon may cont9ue 9 its pa?4 ,he next comp>$ ?is =ce ) ! =ce ex]t$ by ! e>? 9 pull+ ! apple to ! gr\nd1 & f\nd ! =ces to be id5tical6 ,i comp>$1 he writes1 ! =ce necess>y to keep ! moon 9 h] orb ) ! =ce ( gravity at ! surface ( ! e>?1 & f\nd !m answ] pretty ne>ly4 ,"o & ! same =ce pulls ! moon & pulls ! apple--! =ce ( gravity4 ,fur!r1 ! hypo!sis t ! =ce ( gravity v>ies inv]sely z ! squ>e ( ! di/ance _h n[ receiv$ exp]im5tal confirmation4 ,! next /ep 0 p]fectly cle>4 ,if ! moon's motion is controll$ by ! e>?'s gravitational pull1 :y is x n possible t ! e>?'s motion1 9 turn1 is controll$ by ! sun's gravitational pull8 t1 9 fact1 n only ! e>?'s motion1 b ! motion ( all ! planets is regulat$ by ! same means8 ,"h aga9 ,kepl]'s pione] "w 0 a f\ndation comp>able to re9=c$ concrete4 ,kepl]1 z we h se51 _h %[n t ! e>? revolves ar\nd ! sun 9 ! =m ( an ellipse1 "o ( ! foci ( ?is ellipse be+ occupi$ by ! sun4 ,newton n[ prov$ t su* an elliptic pa? 0 possible only if ! int5sity ( ! attractive =ce betwe5 sun & planet v>i$ inv]sely z ! squ>e ( ! di/ance--! v same relation%ip t _h be5 appli$ ) su* success 9 expla9+ ! motion ( ! moon ar\nd ! e>?6 ,newton %[$ t ! moon1 ! sun1 ! planets--e body 9 space con=m$ to ?is law4 ,! e>? attracts ! moon2 b s does ! moon ! e>?4 ,if ! moon revolves ar\nd ! e>? r ?an ! e>? ar\nd ! moon1 x is because ! e>? is a mu* l>g] body1 & h5ce its gravitational pull is /rong]4 ,! same is true ( ! relation%ip exi/+ betwe5 ! e>? & ! sun4 ,fur!r ,developm5ts ( ,newton's ,law ( ,gravitation4 ,:5 we speak ( ! e>? attract+ ! moon1 & ! moon ! e>?1 :at we really mean is t e "o ( ! myriad p>ticles compos+ ! e>? attracts e "o ( ! myriad p>ticles compos+ ! moon1 & vice v]sa4 ,if 9 deal+ ) ! attractive =ces exi/+ betwe5 a planet & its satellite1 or a planet & ! sun1 ! p[] ex]t$ by e "o ( ^! myriad p>ticles w\ld h to be consid]$ sep>ately1 !n ! ma!matical task ( comput+ su* =ces might well appe> hopeless4 ,newton 0 able to pres5t ! problem 9 a v simple =m by po9t+ out t 9 a sph]e su* z ! e>? or ! moon1 ! entire mass might be consid]$ z resid+ 9 ! c5t] ( ! sph]e4 ,= purposes ( computation1 ! e>? c be consid]$ a p>ticle1 ) its entire mass conc5trat$ at ! c5t] ( ! p>ticle4 ,?is viewpo9t enabl$ ,newton to ext5d 8 law ( inv]se squ>es to ! remote/ bodies 9 ! univ]se4 ,if ?is great law ( ,newton's f\nd su* g5]al application beyond our planet1 x s]v$ an equally useful purpose 9 expla9+ a numb] ( puzzl+ features on ?is planet4 ,! ebb & fl[ ( ! tides 0 "o ( ^! puzzles4 ,ev5 9 anci5t times x _h be5 notic$ t a full moon & a high tide w5t h& 9 h&1 & v>i\s my/]i\s p[]s1 7 attribut$ to ! satellite & ! ocean4 ,newton po9t$ out t ! height ( ! wat] 0 a direct consequ5ce ( ! attractive p[] ( ! moon1 &1 to a less] ext5t1 because fur!r away1 ( ! sun4 ,"o ( 8 fir/ explanations1 h[ev]1 dealt ) c]ta9 irregul>ities 9 ! moon's motion ar\nd ! e>?4 ,if ! sol> sy/em w\ld consi/ ( ! e>? & moon alone1 !n ! pa? ( ! moon w\ld be t ( an ellipse1 ) "o ( ! foci ( ?is ellipse occupi$ by ! e>?4 ,un=tunately = ! simplicity ( ! problem1 !re are o!r bodies relatively ne> 9 space1 p>ticul>ly t huge body1 ! sun4 ,! sun n only ex]ts its pull on ! e>? b also on ! moon4 ,h[ev]1 z ! sun is mu* fur!r away f ! moon ?an is ! e>?1 ! e>?'s attraction = its satellite is mu* great]1 despite ! fact t ! sun is mu* hug] & weighs f> m ?an ! e>?4 ,! great] pull ( ! e>? 9 "o direction1 & a less] pull ( ! sun 9 ano!r1 places ! poor moon betwe5 ! devil & ! deep sea4 ,! situation gives rise to a complexity ( =ces1 ! net result ( :i* is t ! moon's orbit is n q t ( an ellipse4 ,newton 0 able to acc\nt = all ! =ces t come into play1 & he prov$ t ! actual pa? ( ! moon 0 a direct consequ5ce ( ! law ( inv]se squ>es 9 actual op]ation4 ,! ,pr9cipia4 ,! law ( gravitation1 embody+ also laws ( motion1 :i* we %all discuss pres5tly1 0 fir/ publi%$ 9 ,newton's immortal ,pr9cipia 7#afhf74 ,a selection f ! preface w disclose ! cont5ts ( ! book1 &1 incid5tally1 ! /yle ( ! au?or3 444 ,we (f] ?is "w z ma!matical pr9ciples ( philosophy2 = all ! difficulty 9 philosophy seems to consi/ 9 ?is--f ! ph5om5a ( motions to inve/igate ! =ces ( nature1 & !n f ^! =ces to demon/rate ! o!r ph5om5a2 & to ?is end ! g5]al propositions 9 ! fir/ & second book are direct$4 ,9 ! ?ird book we give an example ( ?is 9 ! explication ( ! sy/em ( ! _w2 = by ! propositions ma!matically demon/rat$ 9 ! fir/ book1 we !re d]ive f ! cele/ial ph5om5a ! =ces ( gravity ) :i* bodies t5d to ! sun & ! sev]al planets4 ,!n1 f ^! =ces1 by o!r propositions :i* are also ma!matical1 we d$uce ! motions ( ! planets1 ! comets1 ! moon & ! sea4 ,i wi% we c\ld d]ive ! re/ ( ! ph5om5a ( nature by ! same k9d ( reason+ f me*anical pr9ciples2 = ,i am induc$ by _m reasons to suspect t !y may all dep5d ^u c]ta9 =ces by :i* ! p>ticles ( bodies1 by "s causes hi!rto unkn[n1 are ei!r mutually impell$ t[>ds ea* o!r1 & coh]e 9 regul> figures1 or are repell$ & rec$e f ea* o!r4444 ,at ?is po9t we may /ate t nei!r ,newton1 nor any ( ,newton's successors includ+ ,e9/e91 h be5 able to advance ev5 a plausible !ory z to ! nature ( ?is gravitational =ce4 ,we "k t ?is =ce pulls a /one to ! gr\nd2 we "k1 ?anks to ,newton1 ! laws regulat+ ! motions due to gravity2 b :at ?is =ce we call gravity really is we d n "k4 ,! my/]y is z deep z ! my/]y ( ! orig9 ( life4 ,pr(4 ,e9/e91 writes ,pr(4 ,edd+ton1 has s\ght1 & has n rea*$1 any ultimate explanation ( its t is1 gravitation cause4 ,a c]ta9 connection betwe5 ! gravitational field & ! measurem5t ( space has be5 po/ulat$1 b ?is ?r[s light r on ! nature ( our measurem5ts ?an on gravitation itself4 ,! relativity !ory is indiff]5t to hypo!ses z to ! nature ( gravitation1 j z x is indiff]5t to hypo!ses z to ! nature ( light4 ,newton's ,laws ( ,motion4 ,9 8 ,pr9cipia ,newton beg9s ) a s]ies ( simple def9itions deal+ ) matt] & =ce1 & ^! are foll[$ by 8 ?ree fam\s laws ( motion4 ,! nature & am\nt ( ! ef=t requir$ to />t a body mov+1 & ! conditions requir$ to keep a body 9 motion1 are includ$ 9 ^! laws4 ,! ,fundam5tals1 mass1 "t & space1 are exhibit$ 9 _! v>i\s relation%ips4 ,( importance to u p>ticul>ly is t 9 ^! laws1 "t & space are consid]$ z def9ite entities1 & z two di/9ct & widely sep>at$ manife/ations4 ,we %all see t 9 ,e9/e9's h&s a v close relation%ip betwe5 ^! two is br\ght ab\t4 ,bo? ,newton & ,e9/e9 7 l$ to _! !ory ( gravitation by pr(\nd /udies ( ! ma!matics ( motion1 b z ,newton's conception ( motion diff]$ f ,e9/e9's1 & z1 moreov]1 important discov]ies into ! nature ( matt] & ! relation%ip ( motion to matt] 7 made subsequ5t to ,newton's "t1 we ne$ n wond] t ! two !ories %[ div]g5ce2 t1 z we %all see1 ,newton's is probably b an approximation ( ! tru?4 ,if we conf9e our att5tion to our own sol> sy/em1 ! deviation f ,newton's law is1 z a rule1 s small z to be negligible4 ,newton's laws ( motion are really axioms1 l ! axioms ( ,euclid3 !y d n admit ( direct pro(2 b !re is ?is diff]5ce1 t ! axioms ( ,euclid seem m obvi\sly true4 ,= example1 :5 ,euclid in=ms u t ?+s :i* are equal to ! same ?+ are equal to "o ano!r1 we h no hesitation 9 accept+ ?is /atem5t1 = x seems s self-evid5t4 ,:51 h[ev]1 we are told by ,newton t ! alt]ation ( motion is ev] proportional to ! motive =ce impress$1 we are at fir/ some:at bewild]$ ) ! phraseology1 & !n1 ev5 :5 t has be5 ma/]$1 ! read9ess ) :i* we respond w probably dep5d ^u ! am\nt ( sci5tific tra9+ we h receiv$4 ,e body cont9ues 9 its /ate ( re/ or ( uni=m motion 9 a /raight l9e1 unless x is compell$ to *ange t /ate by =ces impress$ !reon4 ,s runs ,newton's fir/ law ( motion4 ,a body does n move unless some?+ causes x to move2 to make ! body move y mu/ ov]come ! in]tia ( ! body4 ,on ! o!r h&1 if a body is mov+1 x t5ds to cont9ue mov+1 z witness our =w>d movem5t :5 ! tra9 is br\ght to a /&/ill4 ,x may be ask$1 :y does n a bullet cont9ue mov+ indef9itely once x has left ! b>rel ( ! gun8 ,because ( ! resi/ance ( ! air :i* x has to ov]come2 & ! pa? ( ! bullet is n /raight because gravity acts on x & t5ds to pull x d[nw>ds4 ,we h no def9ite means ( prov+ t a body once set 9 motion w\ld cont9ue mov+1 = an indef9ite "t1 & along a /raight l9e4 ,:at ,newton meant 0 t a body w\ld cont9ue mov+ provid$ no ext]nal =ce act$ on x2 b 9 actual practise su* a condition is unkn[n4 ,newton's fir/ law def9es =ce z t action necess>y to *ange a /ate ( re/ or ( uni=m motion1 & tells u t =ce alone *anges ! motion ( a body4 ,8 second law deals ) ! relation ( ! =ce appli$ & ! result+ *ange ( motion ( ! body2 t is1 x %[s u h[ =ce may be measur$4 ,! alt]ation ( motion is ev] proportional to ! motive =ce impress$1 & is made 9 ! direction ( ! "r l9e 9 :i* t =ce is impress$4 ,newton's ?ird law runs--,to e action !re is always oppos$ an equal reaction4 ,! v fact t y h to use =ce means t y h to ov]come some?+ ( an opposite nature4 ,! =w>d pull ( a horse t[+ a boat equals ! backw>d pull ( ! t[-rope connect+ boat & horse4 ,_m p1 says ,pr(4 ,watson1 f9d a difficulty 9 accept+ ?is /atem5t 444 s9ce !y ?9k t if ! =ce ex]t$ by ! horse on ! rope 7 n a little great] ?an ! backw>d =ce ex]t$ by ! rope on ! horse1 ! boat w\ld n progress4 ,9 ?is case we mu/1 h[ev]1 rememb] t1 z f> z _! relative positions are conc]n$1 ! horse & ! boat are at re/1 & =m a s+le body1 & ! action & reaction betwe5 !m1 due to ! t5sion on ! rope1 mu/ be equal & opposite1 = o!rwise !re w\ld be relative motion1 "o ) respect to ! o!r4 ,x may well be ask$1 :at be>+ h ^! laws ( ,newton on ! "q ( "t & space8 ,simply ?is1 t to measure =ce ! factors necess>y are ! masses ( ! bodies conc]n$1 ! "t involv$ & ! space cov]$2 & ,newton's equations = measur+ =ces assume "t & space to be q indep5d5t ( "o ano!r4 ,z we %all see1 ?is is 9 /rik+ contra/ to ,e9/e9's view4 ,newton's ,rese>*es on ,light4 ,9 #affe1 :5 b #bc ye>s old1 ,newton inv5t$ ! b9omial !orem & ! inf9itesimal calculus1 two phases ( pure ma!matics :i* h be5 ! cause ( _m a sleepless night to college fre%m54 ,_h ,newton done no?+ else 8 fame w\ld h be5 secure4 ,b we h already glanc$ at 8 law ( inv]se squ>es & ! law ( gravitation4 ,we n[ h to turn to "s ( ,newton's contributions to optics1 because "h m ?an else:]e we %all f9d ! />t+ po9t to a s]ies ( rese>*es :i* h culm9at$ s brilliantly 9 ! "w ( ,e9/e94 ,newton turn$ 8 att5tion to optics 9 #afff :5 he prov$ t ! light f ! sun1 :i* appe>s :ite to u1 is 9 reality a mixture ( all ! colors ( ! ra9b[4 ,?is he %[$ by plac+ a prism betwe5 ! ray ( light & a scre54 ,a spectrum %[+ all ! colors f r$ to violet appe>$ on ! scre54 ,ano!r notable a*ievem5t ( 8 0 ! design ( a telescope :i* br\ght objects to a %>p focus & prev5t$ ! blurr+ effects :i* _h occasion$ s mu* annoyance to ,newton & 8 pr$ecessors 9 all _! a/ronomical obs]vations4 ,^! & o!r discov]ies ( v great int]e/ 7 br\ght toge!r 9 a volume on optics :i* ,newton publi%$ 9 #agjd4 ,our p>ticul> conc]n "h is to exam9e ! views advanc$ by him z to ! nature ( light4 ,t ! nature ( light %\ld h be5 a subject = speculation ev5 to ! anci5ts ne$ n surprise u4 ,if o!r s5ses1 z t\*1 = example1 convey impressions ( objects1 x is true to say t ! s5se ( sight conveys ! mo/ complete impression4 ,our conception ( ! ext]nal _w is l>gely bas$ ^u ! s5se ( sight2 p>ticul>ly s :5 we deal ) objects beyond our rea*4 ,9 a/ronomy1 !re=e1 a /udy ( ! prop]ties ( light is indisp5sable4 #a ,b :at is ?is light8 ,we op5 our eyes & we see2 we close our eyes & we fail to see4 ,at night 9 a d>k room we may h our eyes op5 & yet we d n see2 light1 !n1 mu/ be abs5t4 ,evid5tly1 light does n :olly dep5d ^u :e!r our eyes are op5 or clos$4 ,?is mu* is c]ta93 ! eye functions & some?+ else functions4 ,:at is ?is some?+ else8 ,/rangely en\gh1 ,plato & ,ari/otle reg>d$ light z a prop]ty ( ! eye & ! eye alone4 ,out ( ! eye t5tacles 7 %ot :i* int]cept$ ! object & s illum9at$ x4 ,f :at has already be5 said1 su* a view seems highly unlikely4 ,f> m consi/5t ) _! philosophy 9 o!r directions w\ld h be5 ! !ory t light has its s\rce 9 ! object & n 9 ! eye1 & travels f object to eye r ?an ! rev]se4 ,h[ little sub/ance ! ,ari/otelian contribution possesses is imm$iately se5 :5 we ref] to ! art ( photography4 ,"h light rays produce effects :i* are indep5d5t ( any prop]ty ( ! eye4 ,! bl9d man may click ! cam]a & produce ! impression on ! plate4 ,newton1 ( c\rse1 c\ld h fall5 into no su* error z did ,plato & ,ari/otle4 ,! s\rce ( light to him 0 ! lum9\s body4 ,su* a body _h ! p[] ( emitt+ m9ute p>ticles at great spe$1 & ^! :5 com+ 9 contact ) ! ret9a produce ! s5sation ( sight4 ,?is emission or corpuscul> !ory ( ,newton's 0 combat$ v /rongly by 8 illu/ri\s ,dut* contempor>y1 ,huygh5s1 :o ma9ta9$ t light 0 a wave ph5om5on1 ! di/urbance />t+ at ! lum9\s body & spread+ out 9 all directions4 ,! wave motions ( ! sea (f] a c]ta9 analogy4 ,newton's /ronge/ objection to ,huygh5s' wave !ory 0 t x seem$ to (f] no satisfactory explanation z to :y light travell$ 9 /raight l9es4 ,he says3 ,to me ! fundam5tal supposition itself seems impossible1 namely t ! waves or vibrations ( any fluid c1 l ! rays ( light1 be propagat$ 9 /raight l9es1 )\t a cont9ual & v extravagant b5d+ & spread+ e way into ! quiesc5t m$ium1 :]e !y are t]m9at$ by x4 ,i mi/ake if !re be n bo? exp]im5t & demon/ration to ! contr>y4 ,9 ! corpuscul> !ory ! p>ticles emitt$ by ! lum9\s body 7 suppos$ to travel 9 /raight l9es4 ,9 empty space ! p>ticles travell$ 9 /raight l9es & spread 9 all directions4 ,to expla9 h[ light c\ld trav]se "s types ( matt]--liquids1 = example--,newton suppos$ t ^! light p>ticles travell$ 9 ! spaces betwe5 ! molecules ( ! liquid4 ,newton's objection to ! wave !ory 0 n answ]$ v conv9c+ly by ,huygh5s4 ,today we "k t light waves ( high frequ5cy t5d to travel 9 /raight l9es1 b may be prev5t$ f do+ s by gravitational =ces ( bodies ne> its pa?4 ,b ?is is ,e9/e9's discov]y4 ,a v fam\s exp]im5t by ,f\cault 9 #ahec prov$ beyond ! %ad[ ( a d\bt t ,newton's corpuscul> !ory 0 unt5able4 ,accord+ to ,newton's !ory1 ! velocity ( light mu/ be great] 9 a d5s] m$ium 7su* z wat]7 ?an 9 a light] "o 7su* z air74 ,accord+ to ! wave !ory ! rev]se is true4 ,f\cault %[$ t light does travel m sl[ly 9 wat] ?an 9 air4 ,! facts 7 aga9/ ,newton & 9 favor ( ,huygh5s2 & :]e facts & !ory cla% !re is b "o ?+ to d3 disc>d ! !ory4 ,"s ,facts ab\t ,newton4 ,newton 0 a ,cambridge man1 & ,newton made ,cambridge fam\s z a ma!matical c5t]4 ,s9ce ,newton's day ,cambridge has boa/$ ( a ,cl]k ,maxwell & a ,rayleigh1 & h] ,l>mor1 h] ,j4 ,j4 ,?omson & h] ,ru!r=d are /ill ) u4 ,newton ent]$ ,tr9ity ,college :5 he 0 #ah & soon ?rew himself into high] ma!matics4 ,9 #affi1 :5 b #bg ye>s old1 he became pr(essor ( ma!matics at ,cambridge1 & lat] repres5t$ t seat ( le>n+ 9 ,p>liam5t4 ,:5 8 fri5d ,montague became ,*ancellor ( ! ,ex*equ]1 ,newton 0 (f]$1 & accept$1 ! lucrative position ( ,ma/] ( ! ,m9t4 ,z presid5t ( ! ,royal ,society ,newton 0 occasionally br\ght 9 contact ) ,que5 ,anne4 ,%e held ,newton 9 high e/eem1 & 9 #agje %e conf]r$ ! honor ( knigh?ood on him4 ,he di$ 9 #agbg4 ,i d n "k1 wrote ,newton1 :at ,i may appe> to ! _w1 b1 to myself1 ,i seem to h be5 only l a boy play+ on ! sea%ore1 & direct+ myself 9 n[ & !n f9d+ a smoo!r pebble or a pretti] %ell ?an ord9>y1 :il/ ! great ocean ( tru? lay all undiscov]$ be=e me4 ,su* 0 ! mode/y ( "o :om _m reg>d z ! greate/ intellect ( all ages4 ,,ref]5ces ,an excell5t acc\nt ( ,newton may be f\nd 9 ,sir ,r4 ,s4 ,ball's ,great ,a/ronom]s 7,sir ,isaac ,pitman & ,sons1 ,ltd41 ,london74 ,s$gewick & ,tyl]'s ,a ,%ort ,hi/ory ( ,sci5ce 7,macmillan1 #aiah7 & ,cajori's ,a ,hi/ory ( ,ma!matics 7,macmillan1 #aiag7 may also be consult$ to advantage4 ,! /&>d biography is t by ,brew/]4 ,,ii ,,! ,,e!r ,,& ,,its ,,consequ5ces ,huygh5s' wave !ory ( light1 n[ s g5]ally accept$1 loses its entire significance if a m$ium = ! propagation ( ^! waves is left out ( consid]ation4 ,?is m$ium we call ! e!r4 #b ,huygh5s' reason+ may be illu/rat$ 9 "s su* way z ?is3 ,if a body moves a =ce pu%es or pulls x4 ,t =ce itself is exemplifi$ 9 "s k9d ( matt]--say a horse4 ,! horse 9 pull+ a c>t is atta*$ to ! c>t4 ,! horse 9 pull+ a boat may n be atta*$ to ! boat directly b to a rope1 :i* 9 turn is atta*$ to ! boat4 ,9 common cases :]e "o piece ( matt] affects ano!r1 !re is "s direct contact1 "s g-betwe54 ,b cases are kn[n :]e matt] affects matt] )\t af=d+ u any evid5ce ( contact4 ,take ! case ( a magnet's attraction = a piece ( iron4 ,:]e is ! rope t pulls ! iron t[>ds ! magnet8 ,p]haps y ?9k ! attraction due to ! air 9 betwe5 ! magnet & iron8 ,b remov+ ! air does n /op ! attraction4 ,yet h[ c we conceive ( ! iron be+ drawn to ! magnet unless !re is "s g-betwe58 "s m$ium n readily p]ceptible to ! s5ses p]haps1 & !re=e n /rictly a =m ( matt]8 ,if we c b picture "s su* m$ium we c imag9e our magnet giv+ rise to vibrations 9 ?is m$ium :i* are c>ri$ to ! iron4 ,! magnet may give rise to a di/urbance 9 t portion ( ! m$ium ne>e/ to x2 !n ?is portion h&s ov] ! di/urbance to its neighbor1 ! next portion ( ! m$ium2 & s on1 until ! di/urbance rea*es ! iron4 ,y see1 we are satisfy+ our s5se-p]ception by argu+ 9 favor ( action by actual contact r ?an "s vague action at a di/ance2 ! g-betwe5 in/ead ( be+ a rope is ! m$ium call$ ! e!r4 ,f\cault's exp]im5t completely %att]$ ! corpuscul> !ory ( light1 & = want ( any o!r m plausible alt]native1 we are ?r[n back on ,huygh5s' wave !ory4 ,x w pres5tly appe> t ?is wave !ory has elem5ts 9 x :i* make x an excell5t alt]native4 ,9 ! meantime1 if light is to be consid]$ z a wave motion1 !n ! qu]y imm$iately arises1 :at is ! m$ium ?r\gh :i* ^! waves are propagat$8 ,if wat] is ! m$ium = ! waves ( ! sea1 :at is ! m$ium = ! waves ( light8 ,aga9 we answ]1 ! m$ium is ! e!r4 ,:at ,is ,?is ,e!r8 ,ballooni/s f9d conditions m & m uncom=table ! high] !y asc5d1 = ! d5sity ( ! air 7& !re=e ! am\nt ( oxyg5 9 a giv5 volume ( air7 becomes less & less4 ,meteorologi/s h calculat$ t traces ( ! air we brea! may rea* a height ( "s #bjj miles4 ,b :at is beyond8 ,no?+ b ! e!r1 x is claim$4 ,light f ! sun & />s rea*es u via ! e!r4 ,b :at is ?is e!r8 ,we _c h&le x4 ,we _c see x4 ,x fails to fall )9 ! scope ( any ( our s5ses1 = e attempt to %[ its pres5ce has fail$4 ,x is _s-l 9 ! popul> s5se4 ,x is ,lodge's m$ium = ! s\ls ( ! dep>t$4 ,helmholtz & ,kelv9 tri$ to arrive at "s prop]ties ( ?is hypo!tical sub/ance f a c>eful /udy ( ! mann] 9 :i* waves 7 propagat$ ?r\gh ?is e!r4 ,if1 z ! wave !ory tea*es u1 ! e!r c be set 9 motion1 !n accord+ to laws ( me*anics1 ! e!r has mass4 ,if s x is small] 9 am\nt ?an any?+ :i* c be detect$ ) our mo/ accurate balance4 ,fur!r--& ?is is a difficulty n easily expla9$--if ?is e!r has any mass1 :y does x (f] no detectable resi/ance to ! velocity ( ! planets 9 x8 ,:y is n ! velocity ( ! planets r$uc$ 9 "t1 j z ! velocity ( a rifle bullet decreases ow+ to ! resi/ance ( ! air8 ,lodge1 9 argu+ 9 favor ( an e!r1 holds t its pres5ce _c be detect$ because x p]vades all space & all matt]4 ,8 favorite analogy is to po9t out ! extreme unlikelihood ( a deep-sea fi% discov]+ ! pres5ce ( ! wat] ) :i* x is surr\nd$ on all sides2--all ( :i* tells u no?+ ab\t ! e!r1 b does try to tell u :y we _c detect x4 #c ,9 %ort1 answ]+ ! qu]y at ! head ( ?is p>agraph1 we may say t we d n "k4 ,waves ,set up 9 ,?is ,e!r4 ,! waves are n all ( ! same l5g?4 ,^? t produce ! s5sation ( sight are n ! smalle/ waves kn[n1 yet _! l5g? is s small t x w\ld take any:]e f "o to two million ( !m to cov] a y>d4 ,curi\sly en\gh1 our eye is n s5sitive to wave l5g?s beyond ei!r side ( ^! limits2 yet mu* small]1 & mu* l>g] waves are kn[n4 ,! smalle/ are ! fam\s ,x-rays1 :i* are sc>cely "o t5-?\s&? ! size ( light waves4 ,waves :i* h a p[]ful *emical action--^? :i* act on a photographic plate1 = example--are long] ?an ,x-rays1 yet small] ?an light waves4 ,waves l>g] ?an light waves are ^? :i* produce ! s5sation ( heat1 & ^? us$ 9 wireless telegraphy4 ,! latt] may rea* ! enorm\s l5g? ( #e1jjj y>ds4 ,x-ray1 act9ic1 or *emically active ray1 light ray1 heat ray1 wireless ray--!y diff] 9 size1 yet !y all h ?is 9 common3 !y travel ) ! same spe$ 7#ahf1jjj miles p] second74 ,! ,electromagnetic ,!ory ( ,light4 ,p[]ful support to ! conception t space is p]vad$ by e!r 0 giv5 :5 ,maxwell discov]$ light to be an electromagnetic ph5om5on4 ,f purely !oretical consid]ations ?is gift$ ,engli% physici/ 0 l$ to ! view t waves c\ld be set up z a result ( electrical di/urbances4 ,he prov$ t su* waves w\ld travel ) ! same velocity z light waves4 ,z air is n ne$$ to transmit electrical ph5om5a--= y c pump all air out ( a sy/em & produce a vacuum1 & electrical ph5om5a w cont9ue--,maxwell 0 =c$ to ! conclusion t ! waves set up by electrical di/urbances & transmitt$ ) ! same velocity z light1 7 enabl$ to d s ) ! help ( ! same m$ium z light1 namely1 ! e!r4 ,x 0 n[ b a /ep = ,maxwell to =mulate ! !ory t light itself is no?+ b an electrical ph5om5on1 ! s5sation ( light be+ due to ! passage ( electric waves ?r\gh ! e!r4 ,?is !ory met ) consid]able opposition at fir/4 ,physici/s _h be5 br\ght up 9 a s*ool :i* _h taught t light & electricity 7 two entirely unrelat$ ph5om5a1 & x 0 difficult = !m to loos5 ! %ackles t b\nd !m to ! old] s*ool4 ,b two />tl+ discov]ies help$ to fa/5 att5tion ^u ,maxwell's !ory4 ,"o 0 an exp]im5tal confirmation ( ,maxwell's !oretical d$uction4 ,h]tz1 a pupil ( ,helmholtz1 %[$ h[ ! dis*>ge f a ,leyd5 j> set up oscillations1 :i* 9 turn gave rise to waves 9 ! e!r1 comp>able1 9 s f> z velocity is conc]n$1 to light waves1 b diff]+ f ! latt] 9 wave l5g?1 ! ,h]tzian waves be+ mu* long]4 ,at a lat] date ^! waves 7 fur!r inve/igat$ by ,m>coni1 ) ! result t wireless messages soon began to be fla%$ f "o place to ano!r4 ,j z !re is a close connection betwe5 light & electricity1 s !re is betwe5 light & magnetism4 ,! fir/ to po9t out su* a relation%ip 0 ! illu/ri\s ,mi*ael ,f>aday1 b we owe to ,zeeman ! mo/ ext5sive inve/igations 9 ?is field4 ,if we ?r[ "s common salt into a flame1 &1 ) ! help ( a spectroscope1 exam9e ! spectrum produc$1 we are /ruck by two bright l9es :i* /& out v prom95tly4 ,^! l9es1 yell[ 9 color1 are kn[n z ! ,d-l9es & s]ve to id5tify ev5 m9ute traces ( sodium4 ,:at is true ( sodium is true ( o!r elem5ts3 !y all produce v *>act]i/ic spectra4 ,n[ ,zeeman f\nd t if ! flame is plac$ betwe5 a p[]ful magnet1 & !n "s common salt ?r[n into ! flame1 ! two yell[ l9es give place to t5 yell[ l9es4 ,su* is "o ( ! results ( ! effect ( a magnetic field on light4 ,! ,electron4 ,! ,zeeman effect l$ to sev]al !ories reg>d+ its nature4 ,! mo/ successful ( ^! 0 "o propos$ by ,l>mor & m fully treat$ by ,lor5tz4 ,x has already be5 po9t$ out t ! only diff]5ce betwe5 wireless & light waves is t ! =m] are mu* long]1 &1 we may n[ add1 _! vibrations are mu* sl[]4 ,light & wireless waves be> a relation%ip to "o ano!r comp>able to ! relation%ip born by high & l[-pit*$ s\nds4 ,to produce wireless waves we all[ a *>ge ( electricity to oscillate to & fro4 ,^! oscillations1 or oscillat+ *>ges1 are ! cause ( su* waves4 ,:at *>ges give rise to light waves8 ,lor5tz1 f a /udy ( ! ,zeeman effect1 ascrib$ !m to m9ute p>ticles ( matt]1 small] ?an ! *emical atom1 to :i* ! "n electron 0 giv54 ,! unit ( electricity is ! electron4 ,electrons 9 motion give rise to electricity1 & electrons 9 vibration1 to light4 ,! ,zeeman effect gave ,lor5tz en\gh data to calculate ! mass ( su* electrons4 ,he !n %[$ t ^! electrons 9 a magnetic field w\ld be di/urb$ by precisely ! am\nt to :i* ,zeeman's obs]vations po9t$4 ,9 o!r words1 ! assumption ( ! electron fitt$ 9 mo/ admirably ) ,zeeman's exp]im5ts on magnetism & light4 ,9 ! meantime1 a /udy ( ! dis*>ge ( electricity ?r\gh gases1 &1 lat]1 ! discov]y ( radium1 l$1 among o!r ?+s1 to a /udy ( beta or ca?ode rays--negatively *>g$ p>ticles ( electricity4 ,?r\gh a s]ies ( /rik+ly orig9al exp]im5ts ,j4 ,j4 ,?omson asc]ta9$ ! mass ( su* p>ticles or corpuscles1 & !n ! v /rik+ fact 0 br\ght out t ,?omson's corpuscle weigh$ ! same z ,lor5tz's electron4 ,! electron 0 n m]ely ! unit ( electricity b ! smalle/ p>ticle ( matt]4 ,! ,nature ( ,matt]4 ,all matt] is made up ( "s eighty-odd elem5ts4 ,oxyg51 copp]1 lead are examples ( su* elem5ts4 ,ea* elem5t 9 turn consi/s ( an innum]able numb] ( atoms1 ( a size s small1 t #cjj million ( !m c\ld be plac$ alongside ( "o ano!r )\t _! total l5g? exce$+ "o in*4 ,john ,dalton m ?an a hundr$ ye>s ago po/ulat$ a !ory1 n[ kn[n z ! atomic !ory1 to expla9 "o ( ! fundam5tal laws 9 *emi/ry4 ,?is !ory />t$ out ) an old ,greek assumption t matt] _c be divid$ indef9itely1 b t1 by cont9u$ subdivision1 a po9t w\ld be rea*$ beyond :i* no fur!r break+ up w\ld be possible4 ,! p>ticles at ?is /age ,dalton call$ atoms4 ,dalton's atomic hypo!sis became "o ( ! pill>s ^u :i* ! :ole sup]/ructure ( *emi/ry re/$1 & ?is because x expla9$ a numb] ( p]plex+ difficulties s mu* m satisfactorily ?an any o!r hypo!sis4 ,= ne>ly a c5tury ,dalton /ood z firm z a rock4 ,b e>ly 9 ! n9eties "s epo*-mak+ exp]im5ts on ! dis*>ge ( electricity ?r\gh gases 7 begun by a gr\p ( physici/s1 p>ticul>ly ,crookes1 ,ru!r=d1 ,l5>d1 ,ro5tg51 ,becqu]el1 &1 above all1 ,j4 ,j4 ,?omson1 :i* po9t$ v cle>ly to ! fact t ! atoms are n ! smalle/ p>ticles ( matt] at all2 t1 9 fact1 !y c\ld be brok5 up into electrons1 ( a diamet] "o "o-hundr$-?\s&? t ( an atom4 ,x rema9$ = ! illu/ri\s ,madame ,curie to confirm ?is beyond all d\bt by h] isolation ( radium4 ,"h1 z ,madame ,curie %[$1 0 an elem5t ^: atoms 7 actually break+ up "u "o's v eyes1 s to speak4 ,s f> h we advanc$ s9ce ,dalton's day1 t ,dalton's unit1 ! atom1 is n[ pictur$ z a complex p>ticle patt]n$ aft] our sol> sy/em1 ) a nucleus ( positive electricity 9 ! c5t]1 & p>ticles ( negative electricity1 or electrons1 surr\nd+ ! nucleus4 ,all ?is leads to "o inevitable conclusion3 matt] is electrical 9 nature4 ,b n[ if matt] & light h ! same orig91 & matt] is subject to gravitation1 :y n light also8 ,s reason$ ,e9/e94 ,summ>y4 ,newton's /udies ( matt] 9 motion l$ to 8 !ory ( gravitation1 &1 incid5tally1 to 8 conception ( "t & space z def9ite entities4 ,z we %all see1 ,e9/e9 9 8 !ory ( gravitation bas$ x ^u discov]ies belong+ to ! po/-,newtonian p]iod4 ,"o ( ^! is ,m9k[ski's !ory ( "t & space z "o & insep>able4 ,?is !ory we %all discuss at "s l5g? 9 ! next *apt]4 ,o!r important discov]ies :i* l$ up to ,e9/e9's "w are ! rese>*es :i* culm9at$ 9 ! electron !ory ( matt]4 ,! orig9 ( ?is !ory may be trac$ to /udies deal+ ) ! nature ( light4 ,"h aga9 ,newton appe>s z a pione]4 ,newton's corpuscul> !ory1 h[ev]1 prov$ :olly unt5able :5 ,f\cault %[$ t ! velocity ( light 9 wat] is less ?an 9 air1 :i* is ! v rev]se ( :at ! corpuscul> !ory dem&s1 b :i* does agree ) ,huygh5s' wave !ory4 ,b ,huygh5s' wave !ory po/ulat$ "s m$ium 9 :i* ! waves c act4 ,to ?is m$ium ! "n e!r 0 giv54 ,h[ev]1 all attempts to %[ ! pres5ce ( su* an e!r fail$4 ,naturally en\gh1 "s began to d\bt ! exi/5ce ( an e!r altoge!r4 ,huygh5s' wave !ory receiv$ a new lease ( life ) ,maxwell's discov]y t light is an electromagnetic ph5om5on2 t ! waves set up by a s\rce ( light 7 comp>able to waves set up by an electrical di/urbance4 ,zeeman next %[$ t magnetism 0 also1 closely relat$ to light4 ,a /udy ( ,zeeman's exp]im5ts l$ ,lor5tz to ! conclusion t electrical ph5om5a are due to ! motion ( *>g$ p>ticles call$ electrons1 & t ! vibrations ( ^! electrons give rise to light4 ,! conception ( ! electron z ! v fundam5tal ( matt] 0 arriv$ at 9 an entirely diff]5t way3 f /udies deal+ ) ! dis*>ge ( electricity ?r\gh gases & ! break+ up ( ! atoms ( radium4 ,if matt] & light h ! same orig91 & if matt] is subject to gravitation1 :y n light also8 ,,ref]5ces ,= ! g5]al subject ( light ! read] mu/ be ref]r$ to a r te*nical "w1 b "o ( ! be/ 9 ! ,engli% language3 ,edw9 ,eds]1 ,light = ,/ud5ts 7,macmillan1 #aijg74 ,! nature ( matt] & electricity is excell5tly discuss$ 9 sev]al books ( a popul> v>iety4 ,! v be/ & mo/ complete ( its k9d t has come to ! au?or's att5tion is ,com/ock & ,trol&'s ,! ,nature ( ,matt] & ,electricity 7,d4 ,van ,no/r& ,co41 #aiai74 ,two o!r v readable books are ,soddy's ,matt] & ,en]gy 7,h5ry ,holt & ,co47 & ,crehore's ,! ,my/]y ( ,matt] & ,en]gy 7,d4 ,van ,no/r& ,co41 #aiag74 ,,iii ,,e9/e9 ,?is is ! mo/ important result obta9$ 9 connection ) ! !ory ( gravitation s9ce ,newton's day4 ,e9/e9's reason+ is ! result ( "o ( ! highe/ a*ievem5ts ( human ?\ght4 ,^! words 7 utt]$ by ,sir ,j4 ,j4 ,?omson1 ! presid5t ( ! ,royal ,society1 at a meet+ ( t body held on ,novemb] #f1 #aiai1 to discuss ! results ( ! ,eclipse ,exp$ition4 ,e9/e9 ano!r ,newton--& ?is f ! lips ( ,j4 ,j4 ,?omson1 ,engl&'s mo/ illu/ri\s physici/6 ,if ev] man weigh$ words c>efully x is ?is ,cambridge pr(essor1 ^: own rese>*es h assur$ him immortality = all "t4 ,:at has ?is ,alb]t ,e9/e9 done to m]it su* extraord9>y praise8 ,) ! _w 9 turmoil1 ) classes & races 9 a dea? /ruggle1 ) millions suff]+ & />v+1 :y d we f9d "t to turn our att5tion to ?is ,jew8 ,8 ideas h no be>+ on ,europe's calamity4 ,!y w n add "o bu%el ( :eat to />v+ populations4 ,! answ] is n h>d to f9d4 ,m5 come & m5 g1 b ! my/]y ( ! univ]se rema9s4 ,x is ,e9/e9's glory to h giv5 u a deep] insight into ! univ]se4 ,our sci5ti/s are ,huxley's agno/ics3 !y d n d5y activities beyond our planet2 !y m]ely c5t] _! att5tion on ! kn[able on ?is e>?4 ,our philosoph]s1 on ! o!r h&1 g f> afield4 ,"s ( !m so> s high t1 l "o poet's op9ion ( ,%elley1 ! bubble bur/s4 ,e9/e91 us+ ! tools ( ! sci5ti/--! exp]im5tali/--build$ a skyscrap] :i* ultimately rea*$ ! philosophical s*ool4 ,8 rle is ! rle ( alcohol 9 caus+ wat] & e!r 7! an/hetic7 to mix4 ,e!r & wat] w mix no bett] ?an oil & wat]1 )\t ! pres5ce ( alcohol2 9 its pres5ce a uni=m mixture is obta9$4 ,! ,object ( ! ,eclipse ,exp$ition4 ,e9/e9 prophesi$ t a ray ( light pass+ ne> ! sun w\ld be pull$ out ( its c\rse1 due to ! action ( gravity4 ,he w5t ev5 fur!r4 ,he pr$ict$ h[ mu* out ( its c\rse ! ray w\ld be deflect$4 ,?is pr$iction 0 bas$ on a !ory ( gravitation :i* ,e9/e9 _h develop$ 9 great ma!matical detail4 ,! object ( ! ,briti% ,eclipse ,exp$ition 0 ei!r to prove or disprove ,e9/e9's assumption4 ,! ,result ( ! ,exp$ition4 ,e9/e9's prophecy 0 fulfill$ almo/ to ! lett]4 ,! ,significance ( ! ,result4 ,s9ce ,e9/e9's !ory ( gravitation is intimately associat$ ) c]ta9 revolution>y ideas conc]n+ "t & space1 &1 !re=e1 ) ,fundam5tals ( ! ,univ]se1 ! net result ( ! exp$ition 0 to /r5g!n our belief 9 ! validity ( 8 new view ( ! univ]se4 ,x is our int5tion 9 ! foll[+ pages to discuss ! exp$ition & ! l>g] aspects ( ,e9/e9's !ory t foll[ f x4 ,b be=e we d s we mu/ h a cle> idea ( our sol> sy/em4 ,our ,sol> ,sy/em4 ,9 ! c5t] ( our sy/em is ! sun1 a flam+ mass ( fire1 mu* bigg] ?an our own e>?1 & v1 v f> away4 ,! sun has its family ( eight planets--( :i* ! e>? is "o--:i* travel ar\nd ! sun2 & ar\nd "s ( ! planets !re travel satellites1 or moons4 ,! e>? has su* a satellite1 ! moon4 ,n[ we h good reasons = believ+ t e /> :i* tw9kles 9 ! sky is a sun comp>able to our own1 hav+ also its own planets & its own moons4 ,^! />s1 or suns1 are s mu* fur!r away f u ?an our own sun1 t b a speck ( _! light rea*es u1 & !n only at night1 :51 z ! poets w\ld say1 our sun has gone to its re/+ place4 ,! di/ances betwe5 bodies 9 ! sol> sy/em is s imm5se t1 l ! numb] ( doll>s sp5t 9 ! ,great ,w>1 ! numb] ( miles conveys little1 or no impression4 ,b picture y\rself 9 an express tra9 go+ at ! av]age rate ( #cj miles an h\r4 ,if y />t f ,new ,york & travel cont9u\sly y w\ld rea* ,san ,francisco 9 #d days4 ,if y c\ld cont9ue y\r j\rney ar\nd ! e>? at ! same rate y w\ld complete x 9 #ce days4 ,if n[ y c\ld travel into space & to ! moon1 /ill ) ! same velocity1 y w\ld rea* x 9 #cej days4 ,hav+ rea*$ ! moon1 y c\ld circumscribe x ) ! same express tra9 9 #h days1 z comp>$ to ! #ce days x w\ld take y to circumscribe ! e>?4 ,if in/ead ( travell+ to ! moon y w\ld book y\r passage = ! sun y1 or r y\r desc5dants1 w\ld get !re 9 #cej ye>s1 & x w\ld !n take !m #aj additional ye>s to travel ar\nd ! sun4 ,imm5se z ^! di/ances are1 !y are small z comp>$ to ! di/ances t sep>ate u f ! />s4 ,x takes light :i*1 in/ead ( travell+ #cj miles an h\r1 travels #ahf1jjj miles a second1 ab\t #h m9utes to get to u f ! sun1 & a little ov] #d ye>s to rea* u f ! ne>e/ />4 ,! light f "s ( ! o!r />s d n rea* u = sev]al hundr$ ye>s4 ,! ,eclipse ( ! ,sun4 ,n[ to return to an inf9itesimal "p ( ! univ]se--our sol> sy/em4 ,we h se5 t ! e>? travels ar\nd ! sun1 & ! moon ar\nd ! e>?4 ,at "s "t 9 ! c\rse ( ^! revolutions ! moon mu/ come directly betwe5 ! e>? & ! sun4 ,!n we get ! eclipse ( ! sun4 ,z ! moon is small] ?an ! e>?1 only a portion ( ! e>?'s surface w be cut (f f ! sun's rays4 ,t portion :i* is s cut (f suff]s a total eclipse4 ,?is expla9s :y ! eclipse ( ,may1 #aiai1 :i* 0 a total "o = ,brazil1 0 b a p>tial "o = u4 ,e9/e9's ,ass]tion ,re-/at$4 ,e9/e9 claim$ t a ray ( light f "o ( ! />s1 if pass+ ne> en\gh to ! surface ( ! sun1 w\ld be appreciably deflect$ f its c\rse2 & he calculat$ ! exact am\nt ( ?is deflection4 ,to beg9 )1 :y %\ld ,e9/e9 suppose t ! pa? ( a ray ( light w\ld be affect$ by ! son8 ,newton's law ( gravitation made x cle> t bodies :i* h mass attract "o ano!r4 ,if light has mass--& v rec5t "w t5ds to %[ t x has--!re is no reason :y light %\ld n be attract$ by ! sun1 or any o!r planet>y body4 ,! "q t agitat$ sci5ti/s 0 n s mu* :e!r a ray ( light w\ld be deviat$ f its pa?1 b to :at ext5t ?is deviation w\ld take place4 ,w\ld ,e9/e9's figures be confirm$8 ,( ! bodies )9 our sol> sy/em ! sun is by f> ! l>ge/1 & !re=e x w\ld ex]t a f> great] pull ?an any ( ! planets on light rays com+ f ! />s4 ,"u ord9>y conditions1 h[ev]1 ! sun itself %9es ) su* brilliancy1 t objects ar\nd x1 includ+ rays ( light pass+ ne> its surface1 are :olly dimm$4 ,h5ce ! necessity ( putt+ our !ory to ! te/ only :5 ! moon cov]s up ! sun--:5 !re is a total eclipse ( ! sun4 ,a ,graphical ,repres5tation4 ,imag9e a /> ,a1 s select$ t z its light comes to u ! ray j grazes ! sun4 ,if ! pa? ( ! ray is /raight--if ! sun has no influ5ce on x--!n ! pa? c be repres5t$ by ! l9e ,,ab4 ,if1 h[ev]1 ! sun does ex]t a gravitational pull1 !n its real pa? w be ,,ab'1 & to an obs]v] on ! e>? ! /> w h appe>$ to %ift f ,a to ,a'4 ,:at ! ,eclipse ,exp$ition ,set ,out to ,d4 ,photographs ( />s ar\nd ! sun 7 to be tak5 dur+ ! eclipse1 & ^! photographs comp>$ ) o!rs ( ! same region tak5 at night1 ) ! sun abs5t4 ,any app>5t %ift+ ( ! />s c\ld be det]m9$ by measur+ ! di/ances betwe5 ! />s z %[n on ! photographic plates4 ,?ree ,possibilities ,anticipat$4 ,accord+ to ,newton's assumption1 light consi/s ( corpuscles1 or m9ute p>ticles1 emitt$ f ! s\rce ( light4 ,if ?is be true ^! p>ticles1 hav+ mass1 %\ld be affect$ by ! gravitational pull ( ! sun4 ,if we apply ,newton's !ory ( gravitation & make use ( 8 =mula1 x c be %[n t su* a gravitational pull w\ld displace ! ray ( light by an av]age am\nt equal to #j4ge 7seconds ( angul> di/ance47 #d ,on ! o!r h&1 :]e light is reg>d$ z waves set 9 motion 9 ! e!r ( space 7! wave !ory ( light71 & :]e weight is d5i$ light altoge!r1 no deviation ne$ be expect$4 ,f9ally !re is a ?ird alt]native3 ,e9/e9's4 ,light1 says ,e9/e91 has mass1 & !re=e probably weight4 ,mass is ! matt] light conta9s2 weight repres5ts pull by gravity4 ,light rays w be attract$ by ! sun1 b accord+ to ,e9/e9's !ory ( gravitation ! sun's gravitational pull w displace ! rays by an av]age am\nt equal to #a4ge 7seconds ( angul> di/ance74 ,! ,exp$itions4 ,t sci5ce is highly int]national1 despite _m rec5t examples to ! contr>y1 is evid5c$ by ?is ,briti% ,eclipse ,exp$ition4 ,"h 0 a !ory prop\nd$ by "o :o _h accept$ a *air ( physics 9 ! univ]sity ( ,b]l91 & across ! ,engli% ,*annel 7 ,g]many's mortal enemies mak+ elaborate prep>ations to te/ ! validity ( ! ,b]l9 pr(essor's !ory4 ,! ,briti% ,a/ronomical ,society began to plan ! eclipse exp$ition ev5 be=e ! outbreak ( ! ,great ,w>4 ,dur+ ! ye>s t foll[$1 despite ! de/9ies ( nations :i* hung on ?reads f day to day1 despite ! d>ke/ h\rs 9 ! hi/ory ( ! ,briti% p1 our ,engli% a/ronom]s cont9u$ to give att5tion to ! details ( ! propos$ exp$ition4 ,:5 ! day ( ! eclipse came all 0 9 read9ess4 ,"o exp$ition "u ,dr4 ,crommel9 0 s5t to ,sobral1 ,brazil2 ano!r1 "u ,pr(4 ,edd+ton1 to ,pr9cipe1 an isl& (f ! we/ coa/ ( ,africa4 ,9 bo? ^! places a total eclipse 0 anticipat$4 ,! eclipse occurr$ on ,may #bi1 #aiai4 ,x la/$ = six to eight m9utes4 ,"s #ae photographs1 ) an av]age exposure ( five to six seconds1 7 tak54 ,two mon?s lat] ano!r s]ies ( photographs ( ! same region 7 tak51 b ?is "t ! sun 0 no long] 9 ! mid/ ( ^! />s4 ,! photographs 7 br\ght to ! fam\s ,gre5wi* ,obs]vatory1 ne> ,london1 & ! a/ronom]s & ma!maticians began _! labori\s measurem5ts & calculations4 ,on ,novemb] #f1 at ! meet+ ( ! ,royal ,society1 ! result 0 ann\nc$4 ,! ,sobral exp$ition report$ #a4ih2 ! ,pr9cipe exp$ition #a4fb4 ,! av]age 0 #a4h4 ,e9/e9 _h pr$ict$ #a4ge1 ,newton might h pr$ict$ #j4ge1 & ! or?odox sci5ti/s w\ld h pr$ict$ #j4 ,!re c\ld n[ no long] be any "q z to :i* ( ! ?ree !ories re/$ on a sure f\ndation4 ,to quote ,sir ,frank ,dyson1 ! ,a/ronom] ,royal3 ,aft] a c>eful /udy ( ! plates ,i am prep>$ to say t !re c be no d\bt t !y confirm ,e9/e9's pr$iction4 ,a v def9ite result has be5 obta9$ t light is deflect$ 9 accordance ) ,e9/e9's law ( gravitation4 #e ,:]e ,did ,e9/e9 ,get ,8 ,idea ( ,gravitation8 ,9 #aije ,e9/e9 publi%$ ! fir/ ( a s]ies ( pap]s support+ & ext5d+ a !ory ( "t & space to :i* ! "n ! !ory ( relativity _h be5 giv54 ,^! views z exp\nd$ by ,e9/e9 came into direct conflict ) ,newton's ideas ( "t & space1 & also ) ,newton's law ( gravitation4 ,s9ce ,e9/e9 _h m fai? 9 8 !ory ( relativity ?an 9 ,newton's !ory ( gravitation1 ,e9/e9 s *ang$ ! latt] z to make x h>monize ) ! =m]4 ,m w be said on ?is subject4 ,let n ! read] misund]/&4 ,newton 0 n :olly 9 ! wrong2 he 0 only approximately "r4 ,) ! k exi/+ 9 ,newton's day ,newton c\ld h done no m ?an he did2 no mortal c\ld h done m4 ,b s9ce ,newton's day physics--& sci5ce 9 g5]al--has advanc$ 9 great /rides1 & ,e9/e9 c int]pret pres5t-day k 9 ! same ma/]ful fa%ion t ,newton c\ld 9 8 day4 ,) m facts to build ^u1 ,e9/e9's law ( gravitation is m univ]sal ?an ,newton's2 x really includes ,newton's4 ,b n[ we mu/ turn our att5tion v briefly to ! !ory ( relativity--! !ory t l$ up to ,e9/e9's law ( gravitation4 ,! ,!ory ( ,relativity4 ,! /ory goes t ,e9/e9 0 l$ to 8 ideas by wat*+ a man fall f a ro(4 ,?is /ory be>s a /rik+ simil>ity to ,newton & ! apple4 ,p]haps "o is z true z ! o!r4 #f ,h[ev] t may be1 ! pr9ciple ( relativity is z old z philosophical ?\ght1 = x d5ies ! possibility ( measur+ absolute "t1 or absolute space4 ,all ?+s are relative4 ,we say t x takes a long "t to get f ,new ,york to ,albany2 long z comp>$ to :at8 long1 p]haps1 z comp>$ to ! "t x takes to g f ,new ,york ,city to ,brooklyn4 ,we say ! ,:ite ,h\se is l>ge2 l>ge :5 comp>$ to a room 9 an ap>tm5t4 ,b we c j z well rev]se our ideas ( "t & di/ance4 ,! "t x takes to g f ,new ,york to ,albany is %ort :5 comp>$ to ! "t x takes to g f ,new ,york to ,san ,francisco4 ,! size ( ! ,:ite ,h\se is small :5 comp>$ to ! size ( ! city ( ,wa%+ton4 ,let u take ano!r illu/ration4 ,e "t ! e>? turns on its axis we m>k d[n z a day4 ,) ?is z a basis1 we say t x takes a little ov] #cfe days = ! e>? to complete its revolution ar\nd ! sun1 & our #cfe days we call a ye>4 ,b n[ consid] "s ( our o!r planets4 ,) our "t z a basis1 x takes ,jupit] or ,saturn #aj h\rs to turn on its axis1 z comp>$ to ! #bd h\rs x takes ! e>? to turn4 ,saturn's day is less ?an "o-half our day1 & our day is m ?an twice ,saturn's--t is1 accord+ to ! calculations ( ! inhabitants ( ! e>?4 ,m]cury completes h] circuit ar\nd ! sun 9 #hh days2 ,neptune1 9 #afd ye>s4 ,m]cury's ye> is b "o-f\r? ours1 ,neptune's1 #afd times ours4 ,& obs]v]s at ,m]cury & ,neptune w\ld reg>d u f _! /&>d ( "t1 :i* diff]s f our /&>d4 ,y may say1 :y n take our /&>d ( "t z ! /&>d1 & measure ev]y?+ by x8 ,b :y %\ld y8 ,su* a selection w\ld be q arbitr>y4 ,x w\ld n be bas$ on any?+ absolute1 b w\ld m]ely dep5d on our velocity ar\nd ! sun4 ,^! ideas are old en\gh 9 metaphysics4 ,e9/e9's improvem5t ( !m consi/s n m]ely 9 speculat+ ab\t !m1 b 9 giv+ !m ma!matical =m4 ,! ,orig9 ( ! ,!ory ( ,relativity4 ,a tra9 moves ) ref]5ce to ! e>?4 ,! e>? moves ) ref]5ce to ! sun4 ,we say ! sun is /ation>y & ! e>? moves ar\nd ! sun4 ,b h[ d we "k t ! sun itself does n move ) ref]5ce to "s o!r body8 ,h[ d we "k t our planet>y sy/em1 & ! />s1 & ! cosmos z a :ole is n 9 motion8 ,!re is no way ( answ]+ su* a "q unless we c\ld get a po9t ( ref]5ce :i* is fix$--fix$ absolutely 9 space4 ,we h already allud$ to our view ( ! nature ( light1 kn[n z ! wave !ory ( light4 ,?is !ory po/ulates ! exi/5ce ( an all-p]vad+ e!r 9 space4 ,light sets up wave di/urbances 9 ?is e!r1 & is ?us propagat$4 ,if ! ocean 7 ! e!r1 ! waves ( ! ocean w\ld comp>e ) ! waves set up by ! e!r4 ,b :at is ?is e!r8 ,x _c be se54 ,x defies weight4 ,x p]meates all space4 ,x p]meates all matt]4 ,s say ! expon5ts ( ?is e!r4 ,to ! layman ?is s\nds v mu* l ano!r "n = ! ,deity4 ,to ,sir ,oliv] ,lodge x repres5ts ! spirits ( ! dep>t$4 ,to u1 ( importance is ! conception t ?is e!r is absolutely /ation>y4 ,su* a conception is logical if ! v>i\s developm5ts 9 optics & electricity are consid]$4 ,b if absolutely /ation>y1 !n ! e!r is ! long-s\ght-= po9t ( ref]5ce1 ! guide to det]m9e ! motion ( all bodies 9 ! univ]se4 ,! ,fam\s ,exp]im5t ,p]=m$ by ,pr(4 ,mi*elson4 ,if !re is an e!r1 & a /ation>y e!r1 & if ! e>? moves ) ref]5ce to ?is e!r1 ! e>?1 9 mov+1 mu/ set up e!r curr5ts--j z :5 a tra9 moves x sets up air curr5ts4 ,s reason$ ,mi*elson1 a "y ,annapolis graduate at ! "t4 ,& =?) he devis$ a crucial exp]im5t ! explanation ( :i* we c simplify by ! foll[+ analogy3 ,:i* is ! quick]1 to swim up /ream a c]ta9 l5g?1 say a hundr$ y>ds1 & back aga91 or across /ream ! same l5g? & back aga98 ,! swimm] w answ] t ! up-&-d[n j\rney is long]4 #g ,our riv] is ! e!r4 ,! e>?1 if mov+ 9 ?is e!r1 w set up an e!r /ream1 ! up /ream be+ p>allel to ! e>?'s motion4 ,n[ suppose we s5d a beam ( light a c]ta9 di/ance up ?is e!r /ream & back1 & note ! "t2 & !n turn ! beam ( light at "r angles & s5d x an equal di/ance across ! /ream & back1 & note ! "t4 ,h[ w ! "t tak5 = light to travel 9 ^! two directions comp>e8 ,reason+ by analogy1 ! up-&-d[n /ream %\ld take long]4 ,mi*elson's results did n accord ) analogy4 ,no diff]5ce 9 "t c\ld be detect$ betwe5 ! beam ( light travell+ up-&-d[n1 & across-&-back4 ,b ?is 0 contr>y to all reason if ! po/ulate ( an e!r 0 s\nd4 ,mu/ we !n revise our ideas ( an e!r8 ,p]haps aft] all !re is no e!r4 ,b if no e!r1 h[ are we to expla9 ! propagation ( light 9 space1 & v>i\s electrical ph5om5a connect$ ) x1 su* z ! ,h]tzian1 or wireless waves8 ,!re 0 ano!r alt]native1 "o sugge/$ by ,l>mor 9 ,engl& & ,lor5tz 9 ,holl&1--t matt] is contract$ 9 ! direction ( its motion ?r\gh ! e!r curr5t4 ,to say t bodies are actually %ort5$ 9 ! direction ( _! motion--by an am\nt :i* increases z ! velocity ( ^! bodies approa*es t ( light--is s revolution>y an idea t ,l>mor & ,lor5tz w\ld h>dly h adopt$ su* a viewpo9t b = ! fact t rec5t inve/igations into ! nature ( matt] gave basis = su* belief4 ,matt]1 x has be5 %[n1 is electrical 9 nature4 ,! =ces :i* hold ! p>ticles toge!r are electrical4 ,lor5tz %[$ t ma!matical =mulas = electrical =ces c\ld be develop$ :i* w\ld inevitably lead to ! view t mat]ial bodies contract 9 ! direction ( _! motion4 #h ,b ?is is ridicul\s1 y say2 if ,i am %ort] 9 "o direction ?an 9 ano!r ,i w\ld notice x4 ,y w\ld if "s ?+s 7 %ort5$ & o!rs 7 n4 ,b if all ?+s po9t+ 9 a c]ta9 direction are %ort5$ to an equal ext5t1 h[ are y go+ to notice x8 ,w y apply ! y>d /ick8 ,t has be5 %ort5$4 ,w y pass judgm5t ) ! help ( y\r eyes8 ,b y\r ret9a has also contract$4 ,9 brief1 if all ?+s contract to ! same am\nt x is z if !re 7 no contraction at all4 ,lor5tz's ,plausible ,explanation ,really ,deep5s ! ,my/]y4 ,! />tl+ ideas j outl9$ h op5$ up sev]al new vi/as1 b !y h left unansw]$ ! two problems we set out to solve3 :e!r !re is an e!r1 & if s1 :at is ! velocity ( ! e>? 9 ref]5ce to ?is e!r8 ,lor5tz ma9ta9s t !re is an e!r1 b ! velocities ( bodies relative to x mu/ =ev] rema9 a my/]y4 ,z y *ange y\r position y\r di/ances *ange2 y *ange2 ev]y?+ ab\t y *anges accord+ly2 & all basis = comp>ison is lo/4 ,nature has ent]$ into a conspiracy to keep y ignorant4 ,e9/e9 ,comes ^u ! ,sc5e4 ,e9/e9 />ts ) ! assumption t !re is no possible way ( id5tify+ ?is e!r4 ,suppose we ignore ! e!r altoge!r1 :at !n8 #i ,if we d ignore ! e!r we no long] h any absolute po9t ( ref]5ce2 = if ! e!r is consid]$ /ation>y ! velocity ( all bodies )9 ! e!r may be ref]r$ to x2 any po9t 9 space may be consid]$ a fix$ po9t4 ,if1 h[ev]1 !re is no e!r1 or if we are to ignore x1 h[ are we to get ! velocity ( bodies 9 space8 ,! ,pr9ciple ( ,relativity4 ,if we are to believe 9 ! causal relation%ip betwe5 only su* ?+s z lie )9 ! realm ( obs]vation1 !n obs]vation tea*es u t bodies move only relative to "o ano!r1 & t ! idea ( absolute motion ( a body 9 space is mean+less4 ,e9/e91 !re=e1 po/ulates t !re is no su* ?+ z absolute motion1 & t all we c discuss is ! relative motion ( "o body ) respect to ano!r4 ,?is is j z logical a d$uction f ,mi*elson's exp]im5t z ! attempt to expla9 ,mi*elson's anomal\s results 9 ! light ( an all-p]vad+ e!r4 ,consid] = a mom5t ,newton's s*eme4 ,?is great pione] pictur$ an absolute /&>d ( position 9 space relative to :i* all velocities are measur$4 ,velocities 7 measur$ by not+ ! di/ance cov]$ & divid+ ! result by ! "t tak5 to cov] ! di/ance4 ,space 0 a def9ite entity2 & s 0 "t4 ,"t1 said ,newton1 fl[s ev5ly on1 indep5d5t ( aught else4 ,to ,newton "t & space 7 entirely diff]5t1 9 no way to be conf\nd$4 ,j z ,newton conceiv$ ( absolute space1 s he conceiv$ ( absolute "t4 ,f ! latt] /&>d ( ref]5ce ! idea ( a simultaneity ( ev5ts at diff]5t places arose4 ,b n[ if !re is no /&>d ( ref]5ce1 if ! e!r does n exi/ or does n function1 if two po9ts ,a & ,b _c be ref]r$ to a ?ird1 & fix$ po9t ,c1 h[ c we talk ( simultaneity ( ev5ts at ,a & ,b8 #aj ,9 fact1 ,e9/e9 %[s t if all y c speak ab\t is relative motion1 !n "o ev5t :i* takes say "o m9ute on "o planet w\ld n take "o m9ute on ano!r4 ,= consid] two bodies 9 space1 say ! planets ,v5us & ! e>?1 ) an obs]v] ,b on ,v5us & ano!r ,a on ! e>?4 ,b notes ! "t tak5 = a ray ( light to travel f ,b to ! di/ance ,m4 ,a on ! e>? has means ( obs]v+ ! same ev5t4 ,b records "o m9ute4 ,a is puzzl$1 = 8 wat* records a little m ?an "o m9ute4 ,:at is ! explanation8 ,grant+ t ! two clocks regi/] ! same "t to />t )1 & assum+ fur!r ,e9/e9's hypo!sis t ! velocity ( light is indep5d5t ( its s\rce1 ! diff]5ce 9 "t is due to ! fact t ! planet ,v5us moves ) ref]5ce to ! obs]v] on ! e>?2 s t ,a 9 reality does n measure ! pa? ,,bm & ,,mb1 b ,,bm' & ,m',b'1 :]e ,,bb' repres5ts ! di/ance ,v5us itself has mov$ 9 ! int]val4 ,& if y put y\rself 9 ,b's position on ,v5us ! situation is exactly rev]s$4 ,all ( :i* is simply ano!r way ( say+ t :at is a c]ta9 "t on "o body 9 space is ano!r "t on ano!r body 9 space4 ,!re is no?+ def9ite 9 "t4 ,pr(4 ,coh5's ,illu/ration4 ,fur!r bewild]+ possibilities are cle>ly outl9$ 9 ?is apt illu/ration3 ,if :5 y are go+ away on a long & cont9u\s j\rney y write home at regul> int]vals1 y %\ld n be surpris$ t ) ! be/ possible mail s]vice y\r lett]s w rea* home at progressively long] int]vals1 s9ce ea* lett] w h a great] di/ance to travel ?an its pr$ecessor4 ,if y 7 arm$ ) in/rum5ts to he> ! home clock tick+1 y w\ld f9d t z y\r di/ance f home keeps on increas+1 ! int]vals betwe5 ! successive ticks 7t is1 its seconds7 gr[ long]1 s t if y travell$ ) ! velocity ( s\nd ! home clock w\ld seem to sl[ d[n to a /&/ill--y w\ld nev] he> ! next tick4 ,precisely ! same is true if y sub/itute light rays = s\nd waves4 ,if ) ! nak$ eye or ) a telescope y wat* a clock mov+ away f y1 y w f9d t its m9ute h& takes a long] "t to cov] its five-m9ute int]vals ?an does ! *ronomet] 9 y\r h&1 & if ! clock travell$ ) ! velocity ( light y w\ld =ev] see ! m9ute h& at precisely ! same po9t4 ,t :i* is true ( ! clock is1 ( c\rse1 also true ( all "t int]vals :i* x measures1 s t if y mov$ away f ! e>? ) ! velocity ( light ev]y?+ on x w\ld appe> z /ill z on a pa9t$ canvas4 ,y\r "t has app>5tly come to a /&/ill 9 "o position & is mov+ 9 ano!r6 ,all ?is seems absurd en\gh1 b x does %[ t "t alone has little mean+4 ,m9k[ski's ,conclusion4 ,! relativity !ory requires t we ?or\ghly reorganise our me?od ( measur+ "t4 ,b ?is is intimately associat$ ) our me?od ( measur+ space1 ! di/ance betwe5 two po9ts4 ,z we proce$ we f9d t space )\t "t has little mean+1 & vice v]sa4 ,?is leads ,m9k[ski to ! conclusion t "t by itself & space by itself are m]e %ad[s2 !y are only two aspects ( a s+le & indivisible mann] ( coord9at+ ! facts ( ! physical _w4 ,e9/e9 incorporat$ ?is "t-space idea 9 8 !ory ( relativity4 ,h[ ,we ,measure a ,po9t 9 ,space4 ,suppose ,i say to y t ! *emical laboratory ( ,columbia ,univ]sity faces ,broadway2 w\ld t locate ! laboratory8 ,h>dly1 = any build+ along ,broadway w\ld face ,broadway4 ,b suppose ,i add t x is situat$ at ,broadway & #aag? ,/reet1 s\?-ea/8 !re c\ld be little d\bt !n4 ,b if1 fur!r1 ?is laboratory w\ld occupy b "p ( ! build+1 say ! ?ird floor2 !n ! situation w\ld be specifi$ by nam+ ,broadway1 #aag? ,/reet ,s4 ,e41 ?ird floor4 ,if ,broadway repres5ts l5g?1 #aag? ,/reet wid?1 & ?ird floor height1 we c see :at is meant :5 we say t ?ree dim5sions are requir$ to locate a position 9 space4 ,! ,f\r? ,dim5sion4 ,a po9t on a l9e may be locat$ by "o dim5sion2 a po9t on a wall requires two dim5sions2 a po9t 9 ! room1 l ! *emical laboratory above gr\nd1 ne$s ?ree4 ,! layman _c grasp ! mean+ ( a f\r? dim5sion2 yet ! ma!matician does imag9e x1 & plays ) x 9 ma!matical t]ms4 ,m9k[ski & ,e9/e9 picture "t z ! f\r? dim5sion4 ,to !m "t occupies no m important position ?an l5g?1 bread?1 or ?ickness1 & is z intimately relat$ to ^! ?ree z ! ?ree are to "o ano!r4 ,h4 ,g4 ,wells1 ! noveli/1 has beautifully caught ?is _s :5 9 8 novel1 ,! ,"t ,ma*9e1 he makes 8 h]o travel backw>ds & =w>ds along "t j z a man might g nor? or s\?4 ,:5 ! man ) 8 "t ma*9e goes =w>d he is 9 ! future2 :5 he goes backw>ds he is 9 ! pa/4 ,9 reality1 if we /op to ?9k a m9ute1 !re is no valid reason = ! non-exi/5ce ( a f\r? dim5sion4 ,if "o1 two & ?ree dim5sions1 :y n f\r--& five & six1 = t matt]8 ,!oretically at lea/ !re is no reason :y ! limit %\ld be set at ?ree4 ,h[ev]1 our m9ds become sluggi% :5 we attempt to picture dim5sions beyond ?ree2 j z an extraord9>y ef=t on our "p is ne$$ to foll[ ,e9/e9 :5 he juggles ) space & "t4 ,our difficulty 9 imag9+ f\r dim5sions may be lik5$ to ! difficulty two-dim5sion$ be+s w\ld exp]i5ce 9 imag9+ u1 be+s ( ! conv5tional ?ree dim5sions4 ,suppose ^! two-dim5sional be+s 7 liv+ on ! surface ( ! e>?2 :at c\ld !y see8 ,!y c\ld see no?+ bel[ & no?+ above ! surface4 ,!y w\ld see %ift+ surfaces z we walk$ ab\t1 b be+ s5sitive to l5g? & bread? only1 & n to height1 !y c\ld ga9 no notion :atsoev] ( :at we really look l4 ,x is ?us ) u :5 we attempt to picture f\r-dim5sional space4 ,p]haps ! analogy ( ! motion picture may help u some:at4 ,z ev]ybody kn[s1 ^! motion pictures consi/ ( a s]ies ( photographs :i* are %[n 9 rapid succession on ! scre54 ,ea* photograph by itself conveys a s5sation ( space1 t is1 ( ?ree dim5sions2 b "o photograph rapidly foll[+ ano!r conveys ! s5sation ( space & "t--f\r dim5sions4 ,space & "t are int]l9k$4 ,! ,"t-space ,idea ,fur!r ,develop$4 ,we h already allud$ to ! fact t objects 9 space mov+ ) diff]5t velocities build up diff]5t "t int]vals4 ,?us ! velocity ( ! /> ,arcturus1 if comp>$ ) ref]5ce to ! e>?1 moves at ! rate ( #bjj miles a second4 ,its motion ?r\gh space is diff]5t f ours4 ,objects :i*1 accord+ to ,lor5tz1 contract 9 ! direction ( _! motion to an ext5t proportional to _! velocity1 w contract diff]5tly on ! surface ( ,arcturus ?an on ! e>?4 ,our space is n ,arcturus' space2 nei!r is ,arcturus' "t our "t4 ,& :at is true ( ! discrepancies exi/+ betwe5 ! space & "t conceptions ( ! e>? & ,arcturus is true ( any o!r two bodies 9 space mov+ at diff]5t velocities4 ,b is !re no relation%ip exi/+ betwe5 ! space & "t ( "o body 9 ! univ]se z comp>$ to ! space & "t ( ano!r8 ,c we n f9d some?+ :i* holds good = all bodies 9 ! univ]se8 ,we c4 ,we c express x ma!matically4 ,x is ! concept ( "t & space int]l9k$2 ( "t z ! f\r? dim5sion1 l5g?1 bread? & ?ickness be+ ! o!r ?ree2 ( "t z "o ( f\r co-ord9ates & at "r angles to ! o!r ?ree 7a situation :i* requires a t]rific /ret* ( ! imag9ation to visualize74 ,! f\r dim5sions are suffici5t to co-ord9ate ! "t-space relation%ips ( all bodies 9 ! cosmos1 & h5ce h a univ]sality :i* is totally lack+ :5 "t & space are us$ indep5d5tly ( "o ano!r4 ,! f\r compon5ts ( our "t-space are up-&-d[n1 "r-&-left1 backw>ds-&-=w>ds1 & soon]-&-lat]4 ,/ra9 & ,di/ortion 9 ,space4 ,! f\r-dim5sional unit has be5 giv5 ! "n _w-l9e1 = ! _w-l9e ( any p>ticle 9 space is 9 reality a complete hi/ory ( t p>ticle z x moves ab\t 9 space4 ,p>ticles1 we "k1 attract "o ano!r4 ,if ea* p>ticle is repres5t$ by a _w-l9e ^! _w-l9es w be deflect$ f _! c\rse ow+ to su* attraction4 ,imag9e a bladd] repres5t+ ! univ]se1 ) l9es on x repres5t+ _w-l9es4 ,n[ squeeze ! bladd]4 ,! _w-l9es are b5t 9 v>i\s directions2 !y are di/ort$4 ,?is illu/rates ! influ5ce ( gravity on ^! _w-l9es2 x is ! /ra9 br\ght ab\t due to ! =ce ( attraction4 ,! di/ort$ bladd] illu/rates ev5 m1 = x is a true repres5tation ( ! real _w4 ,h[ ,e9/e9's ,conception ( ,"t & ,space ,l$ to a ,new ,view ( ,gravitation4 ,9 our conv5tional language we speak ( ! sun z ex]t+ a =ce on ! e>?4 ,we h se51 h[ev]1 t ?is =ce br+s ab\t a di/ortion or /ra9 9 _w-l9es2 or1 :at am\nts to ! same ?+1 a di/ortion or /ra9 ( "t & space4 ,! sun's =ce1 ! =ce ( any body 9 space1 is ! =ce due to gravity2 & ^! =ces may n[ be treat$ 9 t]ms ( ! laws ( "t & space4 ,! e>?1 ,pr(4 ,edd+ton tells u1 moves 9 a curv$ orbit1 n because ! sun ex]ts any direct pull1 b because ! e>? is try+ to f9d ! %orte/ way ?r\gh a space & "t :i* h be5 tangl$ up by an influ5ce radiat+ f ! sun4 #aa ,at ?is po9t ,newton's conceptions fail1 = 8 views & 8 laws d n include /ra9s 9 space4 ,newton's law ( gravitation mu/ be supplant$ by "o :i* does include su* di/ortions4 ,x is ,e9/e9's great glory to h suppli$ u ) ?is new law4 ,e9/e9's ,law ( ,gravitation4 ,?is appe>s to be ! only law :i* meets all requirem5ts4 ,x includes ,newton's law1 & _c be di/+ui%$ f x if our exp]im5ts are conf9$ to ! e>? & deal ) relatively small velocities4 ,b :5 we betake ourselves to "s orbits 9 space1 ) a gravitational pull mu* great] ?an ! e>?'s1 & :5 we deal ) velocities comp>able to t ( light1 ! diff]5ces become m>k$4 ,e9/e9's ,!ory ,scores ,its ,fir/ ,great ,victory4 ,9 ! beg9n+ ( ?is *apt] we ref]r$ to ! elaborate eclipse exp$ition s5t by ! ,briti% to te/ ! validity ( ,e9/e9's new !ory ( gravitation4 ,! ,briti% sci5ti/s w\ld h>dly h exp5d$ s mu* "t & en]gy on ?is !ory ( ,e9/e9's b = ! fact t ,e9/e9 _h already scor$ "o great victory4 ,:at 0 x8 ,imag9e b a s+le planet revolv+ ab\t ! sun4 ,accord+ to ,newton's law ( gravitation1 ! planet's pa? w\ld be t ( an ellipse--t is1 oval--& ! planet w\ld travel indef9itely along ?is pa?4 ,accord+ to ,e9/e9 ! pa? w\ld also be elliptical1 b be=e a revolution w\ld be q complet$1 ! planet w\ld />t along a slightly advanc$ l9e1 =m+ a new ellipse slightly 9 advance ( ! fir/4 ,! elliptic orbit sl[ly turns 9 ! direction 9 :i* ! planet is mov+4 ,aft] _m ye>s--c5turies--! orbit w be 9 a diff]5t direction4 ,! rapidity ( ! orbit's *ange ( direction dep5ds on ! velocity ( ! planet4 ,m]cury mov+ at ! rate ( #cj miles a second is ! fa/e/ among ! planets4 ,x has ! fur!r advantage ov] ,v5us or ! e>? 9 t its orbit1 z we h said1 is an ellipse1 :]eas ! orbits ( ,v5us & ! e>? are ne>ly circul>2 & h[ are y go+ to tell 9 :i* direction a circle is po9t+8 ,obs]vation tells u t ! orbit ( ,m]cury is advanc+ at ! rate ( #egd seconds 7( arc7 p] c5tury4 ,we c calculate h[ mu* ( ?is is due to ! gravitational influ5ce ( o!r planets4 ,x am\nts to #ecb seconds p] c5tury4 ,:at ( ! rema9+ #db seconds8 ,y might be incl9$ to attribute ?is %ortcom+ to exp]im5tal error4 ,b :5 all su* possibilities are all[$ = our ma!maticians assure u t ! discrepancy is #cj times great] ?an any possible exp]im5tal error4 ,?is discrepancy betwe5 !ory & obs]vation rema9$ "o ( ! great puzzles 9 a/ronomy until ,e9/e9 cle>$ up ! my/]y4 ,accord+ to ,e9/e9's !ory ! ma!matics ( ! situation is simply ?is3 9 "o revolution ( ! planet ! orbit w advance by a fraction ( a revolution equal to ?ree times ! squ>e ( ! ratio ( ! velocity ( ! planet to ! velocity ( light4 ,:5 we all[ ma!maticians to "w ?is out we get ! figure #dc1 :i* is c]ta9ly close en\gh to #db to be call$ id5tical ) x4 ,/ill ,ano!r ,victory8 ,e9/e9's ?ird pr$iction--! %ift+ ( spectral l9es t[>d ! r$ end ( ! spectrum 9 ! case ( light com+ to u f ! />s ( appreciable mass--seems to h be5 confirm$ rec5tly 7,m>*1 #aibj74 ,! "y physici/s 9 ,bonn1 writes ,pr(4 ,e9/e9 to a fri5d1 h n[ z good z c]ta9ty 7s gut wie si*]7 prov$ ! r$ displacem5t ( ! spectral l9es & h cle>$ up ! gr\nds ( a previ\s disappo9tm5t4 ,summ>y4 ,velocity1 or movem5t 9 space1 is at ! basis ( ,e9/e9's "w1 z x 0 at ! basis ( ,newton's4 ,b "t & space no long] h ! di/9ct mean+s t !y _h :5 exam9$ ) ! help ( ,newton's equations4 ,"t & space are n indep5d5t b int]dep5d5t4 ,!y are mean+less :5 treat$ z sep>ate entities1 giv+ results :i* may hold = "o body 9 ! univ]se b d n hold = any o!r body4 ,to get g5]al laws :i* are applicable to ! cosmos z a :ole ! ,fundam5tals ( ,me*anics mu/ be unit$4 ,e9/e9's great a*ievem5t consi/s 9 apply+ ?is revis$ conception ( space & "t to elucidate cosmical problems4 ,_w-l9es1 repres5t+ ! progress ( p>ticles 9 space1 consi/+ ( space-"t comb9ations 7! f\r dim5sions71 are /ra9$ or di/ort$ 9 space due to ! attraction t bodies exhibit = "o ano!r 7! =ce ( gravitation74 ,on ! o!r h&1 gravitation itself--m univ]sal ?an any?+ else 9 ! univ]se--may be int]pret$ 9 t]ms ( /ra9s on _w-l9es1 or1 :at am\nts to ! same ?+1 /ra9s ( space-"t comb9ations4 ,?is br+s gravitation )9 ! field ( ,e9/e9's conception ( "t & space4 ,t ,e9/e9's conception ( ! univ]se is an improvem5t ^u t ( ,newton's is evid5c$ by ! fact t ,e9/e9's law expla9s all t ,newton's law does1 & also o!r facts :i* ,newton's law is incapable ( expla9+4 ,among ^! may be m5tion$ ! di/ortion ( ! oval orbits ( planets r\nd ! sun 7confirm$ 9 ! case ( ! planet ,m]cury71 & ! deviation ( light rays 9 a gravitational field 7confirm$ by ! ,engli% ,sol> ,eclipse ,exp$ition74 ,e9/e9's ,!ories & ! ,inf]5ces to be ,drawn f ,!m4 ,e9/e9's !ories1 support$ z !y are by v conv9c+ exp]im5ts1 w probably pr(\ndly influ5ce philosophic & p]haps religi\s ?\ght1 b !y c h>dly be said to be ( imm$iate consequ5ce to ! man 9 ! /reet4 ,z ,i h said else:]e1 ,e9/e9's !ories are n go+ to add "o bu%el ( :eat to w>-torn & deva/at$ ,europe1 b 9 _! conception ( a cosmos decid$ly at v>iance ) any?+ yet conceiv$ by any s*ool ( philosophy1 !y w attract ! univ]sal att5tion ( ?9k+ m5 9 all c\ntries4 ,! sci5ti/ is imm$iately /ruck by ! way ,e9/e9 has utiliz$ ! v>i\s a*ievem5ts 9 physics & ma!matics to build up a co-ord9at$ sy/em %[+ connect+ l9ks :]e h]et(ore none 7 p]ceiv$4 ,! philosoph] is equally fasc9at$ ) a !ory1 :i*1 9 detail extremely complex1 %[s a s+ul> beauty ( unity 9 design :5 view$ z a :ole4 ,! revolution>y ideas prop\nd$ reg>d+ "t & space1 ! brilliant way 9 :i* ! mo/ univ]sal prop]ty ( matt]1 gravitation1 is = ! fir/ "t l9k$ up ) o!r prop]ties ( matt]1 &1 above all1 ! exp]im5tal confirmation ( sev]al ( 8 m />tl+ pr$ictions--always ! f9e/ te/ ( sci5tific m]it--/amps ,e9/e9 z "o ( ^? sup]-m5 :o f "t to "t are s5t to u to give u a peep into ! beyond4 ,"s ,facts ab\t ,e9/e9 ,himself4 ,alb]t ,e9/e9 0 born 9 ,g]many "s #de ye>s ago4 ,at fir/ he 0 engag$ at ! ,pat5t ,bureau 9 ,b]ne1 & lat] became pr(essor at ! ,zri* ,polyte*nic4 ,aft] a %ort /ay at ,prague ,univ]sity he accept$ "o ( ^? tempt+ ,akademik] pr(essor%ips at ! univ]sity ( ,b]l9--pr(essor%ips :i* insure a com=table income to ! recipi5t ( "o ( !m1 little univ]sity "w beyond1 p]haps1 "o lecture a week1 & spl5did facilities = rese>*4 ,a simil> inducem5t entic$ ! *emical philosoph]1 ,van 't ,h(f1 to leave 8 ,am/]dam1 & ! ,sw$es came p]il\sly ne> los+ _! mo/ illu/ri\s sci5ti/1 ,arrh5ius4 ,e9/e9 publi%$ 8 fir/ pap] on relativity 9 #aije1 :5 n m ?an #cj ye>s old4 ,( ?is pap] ,planck1 ! ,nobel ,laureate 9 physics ?is ye>1 has (f]$ ?is op9ion3 ,x surpasses 9 boldness ev]y?+ previ\sly sugge/$ 9 speculative natural philosophy & ev5 9 ! philosophical !ories ( k4 ,! revolution introduc$ into ! physical conceptions ( ! _w is only to be comp>$ 9 ext5t & dep? ) t br\ght ab\t by ! introduction ( ! ,cop]nican sy/em ( ! univ]se4 ,e9/e9 publi%$ a full exposition ( ! relativity !ory 9 #aiaf4 ,dur+ ! mom5t\s ye>s ( #aiad-ai1 ,e9/e9 quietly pursu$ 8 labors4 ,!re seems to be "s f\ndation = ! belief t ! ways ( ! ,g]man ,high ,comm& f\nd little favor 9 8 eyes4 ,at any rate1 he 0 n "o ( ! =ty pr(essors :o sign$ ! fam\s manife/o extoll+ ,g]many's aims4 ,we "k = a fact1 writes ,dr4 ,o4 ,a4 ,rank9e1 ( ! ,imp]ial ,college ( ,sci5ce & ,te*nology1 ,london1 t ,e9/e9 nev] 0 employ$ on w> "w4 ,:atev] may h be5 ,g]many's mi/akes 9 o!r directions1 %e left h] m5 ( sci5ce sev]ely alone4 ,9 fact1 !y 7 enc\rag$ to cont9ue 9 _! normal occupations4 ,e9/e9 und\bt$ly receiv$ a l>ge measure ( support f ! ,imp]ial ,gov]nm5t1 ev5 :5 ! ,g]man armies 7 be+ driv5 back across ,belgium4 ,q rec5tly 7,june1 #aibj7 ! ,b>n>d ,m$al ( ,columbia ,univ]sity 0 conf]r$ on him 9 recognition ( 8 highly orig9al & fruitful developm5t ( ! fundam5tal concepts ( physics ?r\gh application ( ma!matics4 ,9 ackn[l$g+ ! honor1 ,pr(4 ,e9/e9 wrote to ,presid5t ,butl] t 444 q ap>t f ! p]sonal satisfaction1 ,i believe ,i may reg>d y\r decision to conf] ! m$al ^u him z a h>b+] ( a bett] "t 9 :i* a s5se ( int]national solid>ity w once m unite s*ol>s ( ! v>i\s c\ntries4 ,,ref]5ces ,= ^? lack+ all a/ronomical k1 an excell5t plan w\ld be to read ! fir/ #dj pages ( ,w4 ,h4 ,snyd]'s ,ev]yday ,sci5ce 7,allyn & ,bacon71 9 :i* may be f\nd a cle> & simple acc\nt ( ! sol> sy/em4 ,?is c\ld be foll[$ ) ,b]tr& ,russell's *apt] on ,! ,nature ( ,matt] 9 8 little volume1 ,! ,problems ( ,philosophy 7,h5ry ,holt & ,co474 ,"h ! read] w be introduc$ to ! purely philosophical side ( ! "q--q a necess>y equipm5t = ! und]/&+ ( ,e9/e9's !ory4 ,( ! non-ma!matical articles :i* h appe>$1 ^? by ,pr(4 ,a4 ,s4 ,edd+ton 7,nature1 volume #aja1 pages #ae & #cd1 #aiah7 & ,pr(4 ,m4 ,r4 ,coh5 7,! ,new ,republic1 ,jan4 #ba1 #aibj7 are ! be/ :i* h come to ! au?or's notice4 ,o!r articles on ,e9/e9's !ory1 "s easily compreh5sible1 o!rs some:at confus+1 & /ill o!rs full ( noise & r empty1 are by ,h4 ,a4 ,lor5tz1 ,! ,new ,york ,times1 ,dec4 #ba1 #aiai 7s9ce repr9t$ 9 book =m by ,br5tano's1 ,new ,york1 #aibj72 ,j4 ,q4 ,/ew>t1 ,sci5tific ,am]ican1 ,jan4 #c1 #aibj2 ,e4 ,cunn+ham1 ,nature1 volume #ajd1 pages #ced & #cgd1 #aiai2 ,f4 ,h4 ,lor+1 ,*emical ,news1 volume #aab1 pages #bbf1 #bcf1 #bdh1 & #bfj1 #aiae2 ,e4 ,b4 ,wilson1 ,sci5tific ,mon?ly1 volume #aj1 page #bag1 #aibj2 ,j4 ,s4 ,ames1 ,sci5ce1 volume #ea1 page #bec1 #aibj #ab2 ,l4 ,a4 ,bau]1 ,sci5ce1 volume #ea1 page #cja 7#aibj71 & volume #ea1 page #eha 7#aibj72 ,sir ,oliv] ,lodge1 ,sci5tific ,mon?ly1 volume #aj1 page #cgh1 #aibj2 ,e4 ,e4 ,slosson1 ,indep5d5t1 ,nov4 #bi1 ,dec4 #ac1 ,dec4 #bj1 ,dec4 #bg1 #aiai 7s9ce collect$ & publi%$ 9 book =m by ,h>c\rt1 ,brace & ,h[e72 ,isabel ,m4 ,lewis1 ,electrical ,exp]im5t]1 ,jan41 #aibj2 ,a4 ,j4 ,lotka1 ,h>p]'s ,magaz9e1 ,m>*1 #aibj1 page #dgg2 & ,r4 ,d4 ,c>mi*ael1 ,new ,york ,times1 ,m>* #bh1 #aibj4 ,e9/e9 himself is responsible = a brief article 9 ,engli% :i* fir/ appe>$ 9 ! ,london ,times1 & 0 lat] repr9t$ 9 ,sci5ce1 volume #ea1 page #h1 #aibj 7see ! ,app5dix74 ,a numb] ( books deal ) ! subject1 & all ( !m are m or less ma!matical4 ,h[ev]1 9 e "o ( ^! volumes c]ta9 *apt]s1 or portions ( *apt]s1 may be read ) pr(it ev5 by ! non-ma!matical read]4 ,"s ( ^! books are3 ,erw9 ,freundli*1 ,! ,f\ndations ( ,e9/e9's ,!ory ( ,gravitation 7,univ]sity ,press1 ,cambridge1 #aibj74 7,a v complete li/ ( ref]5ces--up to ,feb41 #aibj--;is also giv572 ,a4 ,s4 ,edd+ton1 ,report on ! ,relativity ,!ory ( ,gravitation = ! ,physical ,society ( ,london 7,fleetway ,press1 ,ltd41 ,london1 #aibj72 ,r4 ,c4 ,tolman1 ,!ory ( ! ,relativity ( ,motion 7,univ]sity ( ,cali=nia ,press1 #aiag72 ,e4 ,cunn+ham1 ,relativity & ! ,electron ,!ory 7,longmans1 ,gre5 & ,co41 #aiae72 ,r4 ,d4 ,c>mi*ael1 ,! ,!ory ( ,relativity 7,john ,wiley & ,sons1 #aiac72 ,l4 ,silb]/e91 ,! ,!ory ( ,relativity 7,macmillan1 #aiad72 & ,e4 ,cunn+ham1 ,! ,pr9ciple ( ,relativity 7,univ]sity ,press1 ,cambridge1 ,engl&1 #aiad74 ,to ^? famili> ) ! ,g]man language ,e9/e9's book1 b] die spezielle und die allgeme9e ,relativitt/heorie 7,fri$r4 ,vieweg und ,sohn1 ,brauns*weig1 #aibj71 may be recomm5d$4 #ac ,! ma!matical /ud5t may be ref]r$ to a volume incorporat+ ! m important pap]s ( ,e9/e91 ,m9k[ski & ,lor5tz3 ,das ,relativittspr9zip1 7,b4 ,g4 ,teubn]1 ,b]l91 #aiac74 ,e9/e9's pap]s h appe>$ 9 ! ,annal5 d] ,physik1 ,leipzig1 volume #ag1 page #acb1 #aije1 volume #di1 page #gfj1 #aiaf1 & volume #ee1 page #bda1 #aiah4 ,,app5dix ,note #a 7page #ba7 ,on ?is e>? !re is inde$ a t9y corn] ( ! univ]se accessible to o!r s5ses ?an ! s5se ( sight3 b feel+ & ta/e act only at ^? m9ute di/ances :i* sep>ate p>ticles ( matt] :5 '9 contact3' smell ranges ov]1 at ! utmo/1 a mile or two1 & ! greate/ di/ance :i* s\nd is ev] kn[n to h travel$ 7:5 ,krakatoa explod$ 9 #ahhc7 is b a few ?\s& miles--a m]e fraction ( ! e>?'s girdle4--,pr(4 ,h4 ,h4 ,turn] ( ,ox=d4 ,note #b 7page #bg7 ,huygh5s & ,leibniz bo? object$ to ,newton's inv]se squ>e law because x po/ulat$ action at a di/ance1--= example1 ! attractive =ce ( ! sun & ! e>?4 ,?is desire = cont9uity 9 physical laws l$ to ! supposition ( an e!r4 ,we may "h anticipate & /ate t ! reason :i* prompt$ ,huygh5s to object to ,newton's law l$ ,e9/e9 9 our own day to raise objections to ! e!r !ory4 ,9 ! =mulation ( physical laws1 only ^? ?+s 7 to be reg>d$ z be+ 9 causal connection :i* 7 capable ( be+ actually obs]v$4 ,& ! e!r has n be5 actually obs]v$4 ,! idea ( cont9uity implies di/ances betwe5 adjac5t po9ts t are inf9itesimal 9 ext5t2 h5ce ! idea ( cont9uity comes 9 direct opposition ) ! f9ite di/ances ( ,newton4 ,! /atem5t relat+ to causal connection--! refusal to accept an e!r z an absolute base ( ref]5ce--leads to ! pr9ciple ( ! relativity ( motion4 ,note #c 7page #cj7 ,sir ,oliv] ,lodge goes to ! extreme ( p9n+ 8 fai? 9 ! reality ( ?is e!r r ?an 9 t ( matt]4 ,witness ! foll[+ /atem5t he made rec5tly be=e a ,new ,york audi5ce3 ,to my m9d ! e!r ( space is a sub/antial reality ) extraord9>ily p]fect prop]ties1 ) an imm5se am\nt ( en]gy /or$ up 9 x1 ) a con/itution :i* we mu/ discov]1 b a sub/antial reality f> m impressive ?an t ( matt]4 ,empty space1 z we call x1 is full ( e!r1 b x makes no appeal to our s5ses4 ,! appe>ance is z if x 7 no?+4 ,x is ! mo/ important ?+ 9 ! mat]ial univ]se4 ,i believe t matt] is a modification ( e!r1 a v por\s sub/ance1 a ?+ m analog\s to a cobweb or ! ,milky ,way or some?+ v slight & unsub/antial1 z comp>$ to e!r4 ,& aga93 ,! prop]ties ( e!r seem to be p]fect4 ,matt] is less s2 x has friction & ela/icity4 ,no imp]fection has be5 discov]$ 9 ! e!r space4 ,x doesn't we> out2 !re is no dissipation ( en]gy2 !re is no friction4 ,e!r is mat]ial1 yet x is n matt]2 bo? are sub/antial realities 9 physics1 b x is ! e!r ( space t holds ?+s toge!r & acts z a cem5t4 ,my bus9ess is to call att5tion to ! :ole _w ( e!realness ( ?+s1 & ,i h made x a subject ( ?irty ye>s' /udy1 b we mu/ admit t !re is no gett+ hold ( e!r except indirectly4 ,i consid] ! e!r ( space1 says ,lodge1 9 conclusion1 ! "o sub/antial ?+ 9 ! univ]se4 ,& ,lodge is c]ta9ly entitl$ to 8 op9ion4 ,note #d 7page #ea7 ,= ! b5efit ( ^? read]s :o wi% to ga9 a deep] insight into ! relativity pr9ciple1 we %all "h discuss x v briefly4 ,newton & ,galileo _h develop$ a relativity pr9ciple 9 me*anics :i* may be /at$ z foll[s3 ,if "o sy/em ( ref]5ce is 9 uni=m rectil9e> motion ) respect to ano!r sy/em ( ref]5ce1 !n :atev] physical laws are d$uc$ f ! fir/ sy/em hold true = ! second sy/em4 ,! two sy/ems are equival5t4 ,if ! two sy/ems be repres5t$ by xyz & x'y'z'1 & if !y move ) ! velocity ( v along ! x-axis ) respect to "o ano!r1 !n ! two sy/ems are ma!matically relat$ ?us3 x' x - vt1 y' y1 z' z1 t' t1 & ?is imm$iately provides u ) a means ( trans=m+ ! laws ( "o sy/em to ^? ( ano!r4 ,) ! developm5t ( electrodynamics 7:i* we may call electricity 9 motion7 difficulties arose :i* equations 9 me*anics ( type 7#a7 c\ld no long] solve4 ,^! difficulties m]ely increas$ :5 ,maxwell %[$ t light mu/ be reg>d$ z an electromagnetic ph5om5on4 ,= suppose we wi% to inve/igate ! motion ( a s\rce ( light 7:i* may be ! equival5t ( ! motion ( ! e>? ) ref]5ce to ! sun7 ) respect to ! velocity ( ! light x emits--a typical example ( ! /udy ( mov+ sy/ems--h[ are we to coord9ate ! electrodynamical & me*anical elem5ts8 ,or1 aga91 suppose we wi% to inve/igate ! velocity ( electrons %ot out f radium ) a spe$ comp>able to t ( light1 h[ are we to coord9ate ! two bran*es 9 trac+ ! c\rse ( ^! negative p>ticles ( electricity8 ,x 0 difficulties su* z ^! t l$ to ! ,lor5tz-,e9/e9 modifications ( ! ,newton-,galileo relativity equations 7#a74 ,! ,lor5tz-,e9/e9 equations are express$ 9 ! =m3 x' fracx-vtsqrt#a-;fracv#b;c1 y' y1 z' z1 t' fract-fracvc#b;cdot xsqrt#a-;fracv#b;c#b1 c d5ot+ ! velocity ( light 9 vacuo 7:i*1 accord+ to all obs]vations1 is ! same1 irrespective ( ! obs]v]'s /ate ( motion74 ,"h1 y see1 electrodynamical sy/ems 7light & !re=e ray velocities su* z ^? due to electrons7 are br\ght into play4 ,?is gives u ,e9/e9's special !ory ( relativity4 ,f x ,e9/e9 d$uc$ "s />tl+ conceptions ( "t & space4 ,note #e 7page #ee7 ,! velocity 7v7 ( an object 9 "o sy/em w h a diff]5t velocity 7v'7 if ref]r$ to ano!r sy/em 9 uni=m motion relative to ! fir/4 ,x _h be5 suppos$ t only a some?+ end[$ ) inf9ite velocity w\ld %[ ! same velocity 9 all sy/ems1 irrespective ( ! motions ( ! latt]4 ,mi*elson & ,morley's results actually po9t to ! velocity ( light z %[+ ! prop]ties ( ! imag9>y inf9ite velocity4 ,! velocity ( light possesses univ]sal significance2 & ?is is ! basis = mu* ( ,e9/e9's e>li] "w4 ,note #f 7page #ef7 ,euclid assumes t p>allel l9es nev] meet1 :i* !y _c d ( c\rse if !y be def9$ z equidi/ant4 ,b are !re su* l9es8 ,& if n1 :y n assume t all l9es drawn ?r\gh a po9t outside a giv5 l9e w ev5tually int]sect x8 ,su* an assumption leads to a geometry 9 :i* all l9es are conceiv$ z be+ drawn on ! surface ( a sph]e or an ellipse1 & 9 x ! ?ree angles ( a triangle are nev] q equal to two "r angles1 nor ! circumf]5ce ( a circle q pi times its diamet]4 ,b t is precisely :at ! contraction effect due to motion requires4 7,dr4 ,walk]7 ,note #g 7page #eg7 ,e9/e9 _h become tir$ ( assumptions4 ,he _h no p>ticul> objection to ! e!r !ory beyond ! fact t ?is e!r did n come )9 ! range ( our s5ses2 x c\ld n be obs]v$4 ,! consi/5t fulfilm5t ( ! two po/ulates--'action by contact' & causal relation%ip betwe5 only su* ?+s z lie )9 ! realm ( obs]vation see ,note #b comb9$ toge!r is1 ,i believe1 ! ma9spr+ ( ,e9/e9's me?od ( inve/igation4444 7,pr(4 ,freundli*74 ,note #h 7page #ei7 ,t ! conception ( ! simultaneity ( ev5ts is devoid ( mean+ c be d$uc$ f equation 7#b7 see ,note #d4 ,we owe ! pro( to ,e9/e94 ,x is possible to select a suitable "t-coord9ate 9 su* a way t a "t-measurem5t ent]s into physical laws 9 exactly ! same mann] z reg>ds its significance z a space measurem5t 7t is1 !y are fully equival5t symbolically71 & has likewise a def9ite coord9ate direction4444 ,x nev] occurr$ to anyone t ! use ( a light-signal z a means ( connection betwe5 ! mov+-body & ! obs]v]1 :i* is necess>y 9 practice 9 ord] to det]m9e simultaneity1 might affect ! f9al result1 i4e41 ( "t measurem5ts 9 diff]5t sy/ems4 7,freundli*74 ,b t is j :at ,e9/e9 %[s1 because "t-measurem5ts are bas$ on simultaneity ( ev5ts1 & ?is1 z po9t$ out above1 is devoid ( mean+4 ,_h ! old] ma/]s ! occasion to /udy enorm\s velocities1 su* z ! velocity ( light1 r ?an relatively small ones--& ev5 ! velocity ( ! e>? ar\nd ! sun is small z comp>$ to ! velocity ( light--discrepancies betwe5 !ory & exp]im5t w\ld h become app>5t4 ,note #i 7page #fg7 ,h[ ! special !ory ( relativity 7see ,note #d7 l$ to ! g5]al !ory ( relativity 7:i* includ$ gravitation7 may n[ be briefly trac$4 ,:5 we speak ( electrons1 or negative p>ticles ( electricity1 9 motion1 we are speak+ ( en]gy 9 motion4 ,n[ ^! electrons :5 9 motion exhibit prop]ties t are v simil> to matt] 9 motion4 ,:atev] deviations !re are are due to ! enorm\s velocity ( ^! electrons1 & ?is velocity1 z has already be5 po9t$ out1 is comp>able to t ( light2 :]eas be=e ! adv5t ( ! electron1 ! velocity ( no p>ticles comp>able to t ( light _h ev] be5 measur$4 ,accord+ to pres5t views all in]tia ( matt] consi/s only ( ! in]tia ( ! lat5t en]gy 9 x2 444 ev]y?+ t we "k ( ! in]tia ( en]gy holds )\t exception = ! in]tia ( matt]4 ,n[ x is on ! assumption t in]tial mass & gravitational pull are equival5t t ! mass ( a body is det]m9$ by its weight4 ,:at is true ( matt] %\ld be true ( en]gy4 ,! special !ory ( relativity1 h[ev]1 takes into acc\nt only in]tia 7in]tial mass7 b n gravitation 7gravitational pull or weight7 ( en]gy4 ,:5 a body absorbs en]gy equation #b 7see ,note #d7 w record a ga9 9 in]tia b n 9 weight--:i* is contr>y to "o ( ! fundam5tal facts 9 me*anics4 ,?is means t a m g5]al !ory ( relativity is requir$ to include gravitational ph5om5a4 ,h5ce ,e9/e9's ,g5]al ,!ory ( ,relativity4 ,h5ce ! approa* to a new !ory ( gravitation4 ,h5ce ! sett+ up ( a diff]5tial equation :i* comprises ! motion ( a body "u ! influ5ce ( bo? in]tia & gravity1 & :i* symbolically expresses ! relativity ( motions4444 ,! diff]5tial law mu/ always pres]ve ! same =m1 irrespective ( ! sy/em ( coord9ates to :i* x is ref]r$1 s t no sy/em ( coord9ates enjoys a pref]5ce to any o!r4 7,= ! g5]al =m ( ! equation & = an excell5t discussion ( its significance1 see ,freundli*'s monograph1 pages #bg-cc47 ,,"t1 ,,space1 ,,& ,,gravitation #ad ,by ,pr(4 ,alb]t ,e9/e9 ,!re are sev]al k9ds ( !ory 9 physics4 ,mo/ ( !m are con/ructive4 ,^! attempt to build a picture ( complex ph5om5a out ( "s relatively simple proposition4 ,! k9etic !ory ( gases1 = in/ance1 attempts to ref] to molecul> movem5t ! me*anical !rmal1 & diffusional prop]ties ( gases4 ,:5 we say t we und]/& a gr\p ( natural ph5om5a1 we mean t we h f\nd a con/ructive !ory :i* embraces !m4 ,!ories ( ,pr9ciple4--,b 9 addition to ?is mo/ weighty gr\p ( !ories1 !re is ano!r gr\p consi/+ ( :at ,i call !ories ( pr9ciple4 ,^! employ ! analytic1 n ! syn!tic me?od4 ,_! />t+-po9t & f\ndation are n hypo!tical con/itu5ts1 b empirically obs]v$ g5]al prop]ties ( ph5om5a1 pr9ciples f :i* ma!matical =mul are d$uc$ ( su* a k9d t !y apply to e case :i* pres5ts itself4 ,!rmodynamics1 = in/ance1 />t+ f ! fact t p]petual motion nev] occurs 9 ord9>y exp]i5ce1 attempts to d$uce f ?is1 by analytic processes1 a !ory :i* w apply 9 e case4 ,! m]it ( con/ructive !ories is _! compreh5siv5ess1 adaptability1 & cl>ity1 t ( ! !ories ( pr9ciple1 _! logical p]fection1 & ! security ( _! f\ndation4 ,! !ory ( relativity is a !ory ( pr9ciple4 ,to und]/& x1 ! pr9ciples on :i* x re/s mu/ be grasp$4 ,b be=e /at+ ^! x is necess>y to po9t out t ! !ory ( relativity is l a h\se ) two sep>ate /ories1 ! special relativity !ory & ! g5]al !ory ( relativity4 ,s9ce ! "t ( ! anci5t ,greeks x has be5 well kn[n t 9 describ+ ! motion ( a body we mu/ ref] to ano!r body4 ,! motion ( a railway tra9 is describ$ ) ref]5ce to ! gr\nd1 ( a planet ) ref]5ce to ! total assemblage ( visible fix$ />s4 ,9 physics ! bodies to :i* motions are spatially ref]r$ are t]m$ sy/ems ( coord9ates4 ,! laws ( me*anics ( ,galileo & ,newton c be =mulat$ only by us+ a sy/em ( coord9ates4 ,! /ate ( motion ( a sy/em ( coord9ates c n be *os5 arbitr>ily if ! laws ( me*anics are to hold good 7x mu/ be free f twi/+ & f accel]ation74 ,! sy/em ( coord9ates employ$ 9 me*anics is call$ an in]tia-sy/em4 ,! /ate ( motion ( an in]tia-sy/em1 s f> z me*anics are conc]n$1 is n re/rict$ by nature to "o condition4 ,! condition 9 ! foll[+ proposition suffices2 a sy/em ( coord9ates mov+ 9 ! same direction & at ! same rate z a sy/em ( in]tia is itself a sy/em ( in]tia4 ,! special relativity !ory is !re=e ! application ( ! foll[+ proposition to any natural process3 ,e law ( nature :i* holds good ) respect to a coord9ate sy/em ,k mu/ also hold good = any o!r sy/em ,k' provid$ t ,k & ,k' are 9 uni=m movem5t ( translation4 ,! second pr9ciple on :i* ! special relativity !ory re/s is t ( ! con/ancy ( ! velocity ( light 9 a vacuum4 ,light 9 a vacuum has a def9ite & con/ant velocity1 indep5d5t ( ! velocity ( its s\rce4 ,physici/s owe _! confid5ce 9 ?is proposition to ! ,maxwell-,lor5tz !ory ( electro-dynamics4 ,! two pr9ciples :i* ,i h m5tion$ h receiv$ /rong exp]im5tal confirmation1 b d n seem to be logically compatible4 ,! special relativity !ory a*iev$ _! logical reconciliation by mak+ a *ange 9 k9ematics1 t is to say1 9 ! doctr9e ( ! physical laws ( space & "t4 ,x became evid5t t a /atem5t ( ! co9cid5ce ( two ev5ts c\ld h a mean+ only 9 connection ) a sy/em ( coord9ates1 t ! mass ( bodies & ! rate ( movem5t ( clocks mu/ dep5d on _! /ate ( motion ) reg>d to ! coord9ates4 ,! ,old] ,physics4--,b ! old] physics1 includ+ ! laws ( motion ( ,galileo & ,newton1 cla%$ ) ! relativi/ic k9ematics t ,i h indicat$4 ,! latt] gave orig9 to c]ta9 g5]aliz$ ma!matical conditions ) :i* ! laws ( nature w\ld h to con=m if ! two fundam5tal pr9ciples 7 compatible4 ,physics _h to be modifi$4 ,! mo/ notable *ange 0 a new law ( motion = 7v rapidly7 mov+ mass-po9ts1 & ?is soon came to be v]ifi$ 9 ! case ( electrically-lad5 p>ticles4 ,! mo/ important result ( ! special relativity sy/em conc]n$ ! in]t mass ( a mat]ial sy/em4 ,x became evid5t t ! in]tia ( su* a sy/em mu/ dep5d on its en]gy-cont5t1 s t we 7 driv5 to ! conception t in]t mass 0 no?+ else ?an lat5t en]gy4 ,! doctr9e ( ! cons]vation ( mass lo/ its indep5d5ce & became m]g$ 9 ! doctr9e ( cons]vation ( en]gy4 ,! special relativity !ory :i* 0 simply a sy/ematic ext5sion ( ! electro-dynamics ( ,maxwell & ,lor5tz1 _h consequ5ces :i* rea*$ beyond itself4 ,mu/ ! indep5d5ce ( physical laws ) reg>d to a sy/em ( coord9ates be limit$ to sy/ems ( coord9ates 9 uni=m movem5t ( translation ) reg>d to "o ano!r8 ,:at has nature to d ) ! coord9ate sy/ems t we propose & ) _! motions8 ,al?\gh x may be necess>y = our descriptions ( nature to employ sy/ems ( coord9ates t we h select$ arbitr>ily1 ! *oice %\ld n be limit$ 9 any way s f> z _! /ate ( motion is conc]n$4 7,g5]al !ory ( relativity47 ,! application ( ?is g5]al !ory ( relativity 0 f\nd to be 9 conflict ) a well-kn[n exp]im5t1 accord+ to :i* x appe>$ t ! weight & ! in]tia ( a body dep5d$ on ! same con/ants 7id5tity ( in]t & heavy masses74 ,consid] ! case ( a sy/em ( coord9ates :i* is conceiv$ z be+ 9 /able rotation relative to a sy/em ( in]tia 9 ! ,newtonian s5se4 ,! =ces :i*1 relatively to ?is sy/em1 are c5trifugal mu/1 9 ! ,newtonian s5se1 be attribut$ to in]tia4 ,b ^! c5trifugal =ces are1 l gravitation1 proportional to ! mass ( ! bodies4 ,is x n1 !n1 possible to reg>d ! sy/em ( coord9ates z at re/1 & ! c5trifugal =ces z gravitational8 ,! int]pretation seem$ obvi\s1 b classical me*anics =bade x4 ,?is slight sket* indicates h[ a g5]aliz$ !ory ( relativity mu/ include ! laws ( gravitation1 & actual pursuit ( ! conception has ju/ifi$ ! hope4 ,b ! way 0 h>d] ?an 0 expect$1 because x contradict$ ,euclidian geometry4 ,9 o!r words1 ! laws accord+ to :i* mat]ial bodies are arrang$ 9 space d n exactly agree ) ! laws ( space prescrib$ by ! ,euclidian geometry ( solids4 ,?is is :at is meant by ! phrase a w>p 9 space4 ,! fundam5tal concepts /raight1 plane1 etc41 accord+ly lose _! exact mean+ 9 physics4 ,9 ! g5]aliz$ !ory ( relativity1 ! doctr9e ( space & "t1 k9ematics1 is no long] "o ( ! absolute f\ndations ( g5]al physics4 ,! geometrical /ates ( bodies & ! rates ( clocks dep5d 9 ! fir/ place on _! gravitational fields1 :i* aga9 are produc$ by ! mat]ial sy/em conc]n$4 ,?us ! new !ory ( gravitation div]ges widely f t ( ,newton ) respect to its basal pr9ciple4 ,b 9 practical application ! two agree s closely t x has be5 difficult to f9d cases 9 :i* ! actual diff]5ces c\ld be subject$ to obs]vation4 ,z yet only ! foll[+ h be5 sugge/$3 #a4 ,! di/ortion ( ! oval orbits ( planets r\nd ! sun 7confirm$ 9 ! case ( ! planet ,m]cury74 #b4 ,! deviation ( light-rays 9 a gravitational field 7confirm$ by ! ,engli% ,sol> ,eclipse exp$ition74 #c4 ,! %ift+ ( spectral l9es t[>ds ! r$ end ( ! spectrum 9 ! case ( light com+ to u f />s ( appreciable mass 7n yet confirm$74 ,! great attraction ( ! !ory is its logical consi/5cy4 ,if any d$uction f x %\ld prove unt5able1 x mu/ be giv5 up4 ,a modification ( x seems impossible )\t de/ruction ( ! :ole4 ,no "o mu/ ?9k t ,newton's great creation c be ov]?r[n 9 any real s5se by ?is or by any o!r !ory4 ,8 cle> & wide ideas w = ev] reta9 _! significance z ! f\ndation on :i* our mod]n conceptions ( physics h be5 built4 ,,e9/e9',s ,,law ,,( ,,gravitation #ae ,by ,pr(4 ,j4 ,s4 ,ames ,johns ,hopk9s ,univ]sity 444 ,9 ! treatm5t ( ,maxwell's equations ( ! electromagnetic field1 sev]al inve/igators realiz$ ! importance ( d$uc+ ! =m ( ! equations :5 appli$ to a sy/em mov+ ) a uni=m velocity4 ,"o object ( su* an inve/igation w\ld be to det]m9e su* a set ( trans=mation =mul z w\ld leave ! ma!matical =m ( ! equations unalt]$4 ,! necess>y relations betwe5 ! new space-coord9ates1 ^? apply+ to ! mov+ sy/em1 & ! orig9al set 7 ( c\rse obvi\s2 & elem5t>y me?ods l$ to ! d$uction ( a new v>iable :i* %\ld replace ! "t coord9ate4 ,?is /ep 0 tak5 by ,lor5tz & also1 ,i believe1 by ,l>mor & by ,voigt4 ,! ma!matical d$uctions & applications 9 ! h&s ( ^! m5 7 extremely beautiful1 & are probably well kn[n to y all4 ,lor5tz' pap] on ?is subject appe>$ 9 ! ,proce$+s ( ! ,am/]dam ,academy 9 #aijd4 ,9 ! foll[+ ye> !re 0 publi%$ 9 ! ,annal5 d] ,physik a pap] by ,e9/e91 writt5 )\t any k ( ! "w ( ,lor5tz1 9 :i* he arriv$ at ! same trans=mation equations z did ! latt]1 b ) an entirely diff]5t & fundam5tally new int]pretation4 ,e9/e9 call$ att5tion 9 8 pap] to ! lack ( def9it5ess 9 ! concepts ( "t & space1 z ord9>ily /at$ & us$4 ,he analyz$ cle>ly ! def9itions & po/ulates :i* 7 necess>y be=e "o c\ld speak ) exactness ( a l5g? or ( an int]val ( "t4 ,he dispos$ =ev] ( ! propriety ( speak+ ( ! true l5g? ( a rod or ( ! true duration ( "t1 %[+1 9 fact1 t ! num]ical values :i* we atta* to l5g?s or int]vals ( "t dep5d ^u ! def9itions & po/ulates :i* we adopt4 ,! words absolute space or "t int]vals are devoid ( mean+4 ,z an illu/ration ( :at is meant ,e9/e9 discuss$ two possible ways ( measur+ ! l5g? ( a rod :5 x is mov+ 9 ! direction ( its own l5g? ) a uni=m velocity1 t is1 aft] hav+ adopt$ a scale ( l5g?1 two ways ( assign+ a numb] to ! l5g? ( ! rod conc]n$4 ,"o me?od is to imag9e ! obs]v] mov+ ) ! rod1 apply+ along its l5g? ! measur+ scale1 & read+ (f ! positions ( ! ends ( ! rod4 ,ano!r me?od w\ld be to h two obs]v]s at re/ on ! body ) ref]5ce to :i* ! rod has ! uni=m velocity1 s /ation$ along ! l9e ( motion ( ! rod t z ! rod moves pa/ !m !y c note simultane\sly on a /ation>y measur+ scale ! positions ( ! two ends ( ! rod4 ,e9/e9 %[$ t1 accept+ two po/ulates :i* ne$ no def5se at ?is "t1 ! two me?ods ( measurem5ts w\ld lead to diff]5t num]ical values1 &1 fur!r1 t ! div]g5ce ( ! two results w\ld increase z ! velocity ( ! rod 0 increas$4 ,9 assign+ a numb]1 !re=e1 to ! l5g? ( a mov+ rod1 "o mu/ make a *oice ( ! me?od to be us$ 9 measur+ x4 ,obvi\sly ! pref]able me?od is to agree t ! obs]v] %all move ) ! rod1 c>ry+ 8 measur+ in/rum5t ) him4 ,?is disposes ( ! problem ( measur+ space relations4 ,! obs]v$ fact t1 if we measure ! l5g? ( ! rod on diff]5t days1 or :5 ! rod is ly+ 9 diff]5t positions1 we always obta9 ! same value (f]s no in=mation conc]n+ ! real l5g? ( ! rod4 ,x may h *ang$1 or x may n4 ,x mu/ always be rememb]$ t measurem5t ( ! l5g? ( a rod is simply a process ( comp>ison betwe5 x & an arbitr>y /&>d1 e4g41 a met]-rod or y>d-/ick4 ,9 reg>d to ! problem ( assign+ numb]s to int]vals ( "t1 x mu/ be borne 9 m9d t1 /rictly speak+1 we d n measure su* int]vals1 i4e41 t we d n select a unit int]val ( "t & f9d h[ _m times x is conta9$ 9 ! int]val 9 "q4 7,simil>ly1 we d n measure ! pit* ( a s\nd or ! temp]ature ( a room47 ,our practical in/rum5ts = assign+ numb]s to "t-int]vals dep5d 9 ! ma9 ^u our agree+ to believe t a p5dulum sw+s 9 a p]fectly uni=m mann]1 ea* vibration tak+ ! same "t z ! next "o4 ,( c\rse we _c prove t ?is is true1 x is1 /rictly speak+1 a def9ition ( :at we mean by equal int]vals ( "t2 & x is n a p>ticul>ly good def9ition at t4 ,its limitations are suffici5tly obvi\s4 ,! be/ way to proce$ is to consid] ! concept ( uni=m velocity1 & !n1 us+ ! idea ( "s entity hav+ su* a uni=m velocity1 to def9e equal int]vals ( "t z su* int]vals z are requir$ = ! entity to trav]se equal l5g?s4 ,^! la/ we h already def9$4 ,:at is requir$ 9 addition is to adopt "s mov+ entity z giv+ our def9ition ( uni=m velocity4 ,consid]+ our kn[n univ]se x is self-evid5t t we %\ld *oose 9 our def9ition ( uni=m velocity ! velocity ( light1 s9ce ?is selection c\ld be made by an obs]v] any:]e 9 our univ]se4 ,hav+ agre$ !n to illu/rate by ! words uni=m velocity t ( light1 our def9ition ( equal int]vals ( "t is complete4 ,?is implies1 ( c\rse1 t !re is no unc]ta9ty on our "p z to ! fact t ! velocity ( light always has ! same value at any "o po9t 9 ! univ]se to any obs]v]1 q reg>dless ( ! s\rce ( light4 ,9 o!r words1 ! po/ulate t ?is is true und]lies our def9ition4 ,foll[+ ?is me?od ,e9/e9 develop$ a sy/em ( measur+ bo? space & "t int]vals4 ,z a matt] ( fact 8 sy/em is id5tically t :i* we use 9 daily life ) ref]5ce to ev5ts "h on ! e>?4 ,he fur!r %[$ t if a man 7 to measure ! l5g? ( a rod1 = in/ance1 on ! e>? & !n 7 able to c>ry ! rod & 8 measur+ app>atus to ,m>s1 ! sun1 or to ,arcturus he w\ld obta9 ! same num]ical value = ! l5g? 9 all places & at all times4 ,?is doesn't mean t any /atem5t is impli$ z to :e!r ! l5g? ( ! rod has rema9$ un*ang$ or n2 su* words d n h any mean+--rememb] t we c n speak ( true l5g?4 ,x is ?us cle> t an obs]v] liv+ on ! e>? w\ld h a def9ite sy/em ( units 9 t]ms ( :i* to express space & "t int]vals1 i4e41 he w\ld h a def9ite sy/em ( space coord9ates 7x1 y1 z7 & a def9ite "t coord9ate 7t72 & simil>ly an obs]v] liv+ on ,m>s w\ld h 8 sy/em ( coord9ates 7x'1 y'1 z'1 t'74 ,provid$ t "o obs]v] has a def9ite uni=m velocity ) ref]5ce to ! o!r1 x is a comp>atively simple matt] to d$uce ! ma!matical relations betwe5 ! two sets ( coord9ates4 ,:5 ,e9/e9 did ?is1 he arriv$ at ! same trans=mation =mul z ^? us$ by ,lor5tz 9 8 developm5t ( ,maxwell's equations4 ,! latt] _h %[n t1 us+ ^! =mul1 ! =m ( ! laws = all electromagnetic ph5om5a ma9ta9$ ! same =m2 s ,e9/e9's me?od proves t us+ 8 sy/em ( measurem5t an obs]v]1 any:]e 9 ! univ]se1 w\ld z ! result ( 8 own inve/igation ( electromagnetic ph5om5a arrive at ! same ma!matical /atem5t ( !m z any o!r obs]v]1 provid$ only t ! relative-velocity ( ! two obs]v]s 0 uni=m4 ,e9/e9 discuss$ _m o!r mo/ important que/ions at ?is "t2 b x is n necess>y to ref] to !m 9 connection ) ! pres5t subject4 ,s f> z ?is is conc]n$1 ! next important /ep to note is t tak5 9 ! fam\s address ( ,m9k[ski1 9 #aijh1 on ! subject ( ,space & ,"t4 ,x w\ld be difficult to ov]/ate ! importance ( ! concepts advanc$ by ,m9k[ski4 ,!y m>k$ ! beg9n+ ( a new p]iod 9 ! philosophy ( physics4 ,i %all n attempt to expla9 8 ideas 9 detail1 b %all conf9e myself to a few g5]al /atem5ts4 ,8 po9t ( view & 8 l9e ( developm5t ( ! !me are absolutely diff]5t f ^? ( ,lor5tz or ( ,e9/e92 b 9 ! end he makes use ( ! same trans=mation =mul4 ,8 great contribution consi/s 9 giv+ u a new geometrical picture ( _! mean+4 ,x is sc>cely fair to call ,m9k[ski's developm5t a picture2 = to u a picture c nev] h m ?an ?ree dim5sions1 our s5ses limit u2 :ile 8 picture calls = p]ception ( f\r dim5sions4 ,x is ?is fact t r5d]s any ev5 semi-popul> discussion ( ,m9k[ski's "w s impossible4 ,we c all see t = u to describe any ev5t a k ( f\r coord9ates is necess>y1 ?ree = ! space specification & "o = ! "t4 ,a complete picture c\ld be giv5 !n by a po9t 9 f\r dim5sions4 ,all f\r coord9ates are necess>y3 we nev] obs]ve an ev5t except at a c]ta9 "t1 & we nev] obs]ve an in/ant ( "t except ) ref]5ce to space4 ,discuss+ ! laws ( electromagnetic ph5om5a1 ,m9k[ski %[$ h[ 9 a space ( f\r dim5sions1 by a suitable def9ition ( axes1 ! ma!matical trans=mation ( ,lor5tz & ,e9/e9 c\ld be describ$ by a rotation ( ! set ( axes4 ,we are all accu/om$ to a rotation ( our ord9>y c>tesian set ( axes describ+ ! position ( a po9t4 ,we ord9>ily *oose our axes at any location on ! e>? z foll[s3 "o v]tical1 "o ea/ & we/1 "o nor? & s\?4 ,s if we move f any "o laboratory to ano!r1 we *ange our axes2 !y are always or?ogonal1 b 9 mov+ f place to place !re is a rotation4 ,simil>ly1 ,m9k[ski %[$ t if we *oose f\r or?ogonal axes at any po9t on ! e>?1 accord+ to 8 me?od1 to repres5t a space-"t po9t us+ ! me?od ( measur+ space & "t int]vals z outl9$ by ,e9/e92 &1 if an obs]v] on ,arcturus us$ a simil> set ( axes & ! me?od ( measurem5t :i* he naturally w\ld1 ! set ( axes ( ! latt] c\ld be obta9$ f ^? ( ! obs]v] on ! e>? by a pure rotation 7& naturally a transf] ( ! orig974 ,?is is a beautiful geometrical result4 ,to complete my /atem5t ( ! me?od1 ,i mu/ add t in/ead ( us+ z 8 f\r? axis "o along :i* num]ical values ( "t are laid (f1 ,m9k[ski def9$ 8 f\r? coord9ate z ! product ( "t & ! imag9>y con/ant1 ! squ>e root ( m9us "o4 ,?is introduction ( imag9>y quantities might be expect$1 possibly1 to introduce difficulties2 b1 9 reality1 x is ! v ess5ce ( ! simplicity ( ! geometrical description j giv5 ( ! rotation ( ! sets ( axes4 ,x ?us appe>s t diff]5t obs]v]s situat$ at diff]5t po9ts 9 ! univ]se w\ld ea* h _! own set ( axes1 all diff]5t1 yet all connect$ by ! fact t any "o c be rotat$ s z to co9cide ) any o!r4 ,?is means t !re is no "o direction 9 ! f\r-dim5sional space t corresponds to "t = all obs]v]s4 ,j z ) ref]5ce to ! e>? !re is no direction :i* c be call$ v]tical = all obs]v]s liv+ on ! e>?4 ,9 ! s5se ( an absolute mean+ ! words up & d[n1 be=e & aft]1 soon] or lat]1 are entirely mean+less4 ,?is concept ( ,m9k[ski's may be made cle>]1 p]haps1 by ! foll[+ process ( ?\ght4 ,if we take a section ?r\gh our ?ree-dim5sional space1 we h a plane1 i4e41 a two-dim5sional space4 ,simil>ly1 if a section is made ?r\gh a f\r-dim5sional space1 "o ( ?ree dim5sions is obta9$4 ,?us1 = an obs]v] on ! e>? a def9ite section ( ,m9k[ski's f\r-dim5sional space w give u our ord9>y ?ree-dim5sional "o2 s t ?is section w1 z x 71 break up ,m9k[ski's space into our space & give u our ord9>y "t4 ,simil>ly1 a diff]5t section w\ld h to be us$ to ! obs]v] on ,arcturus2 b by a suitable selection he w\ld get 8 own famili> ?ree-dim5sional space & 8 own "t4 ,?us ! space def9$ by ,m9k[ski is completely isotropic 9 ref]5ce to measur$ l5g?s & times1 !re is absolutely no diff]5ce betwe5 any two directions 9 an absolute s5se2 = any p>ticul> obs]v]1 ( c\rse1 a p>ticul> section w cause ! space to fall ap>t s z to suit 8 habits ( measurem5t2 any section1 h[ev]1 tak5 at r&om w d ! same ?+ = "s obs]v] some:]e4 ,f ano!r po9t ( view1 t ( ,lor5tz & ,e9/e91 x is obvi\s t1 s9ce ?is f\r-dim5sional space is isotropic1 ! expression ( ! laws ( electromagnetic ph5om5a take id5tical ma!matical =ms :5 express$ by any obs]v]4 ,! "q ( c\rse mu/ be rais$ z to :at c be said 9 reg>d to ph5om5a :i* s f> z we "k d n h an electromagnetic orig94 ,9 p>ticul> :at c be done ) respect to gravitational ph5om5a8 ,be=e1 h[ev]1 %[+ h[ ?is problem 0 attack$ by ,e9/e92 & ! fact t ! subject ( my address is ,e9/e9's "w on gravitation %[s t ultimately ,i %all expla9 ?is1 ,i mu/ emphasize ano!r feature ( ,m9k[ski's geometry4 ,to describe ! space-"t *>act]i/ics ( any ev5t a po9t1 def9$ by its f\r coord9ates1 is suffici5t2 s1 if "o obs]ves ! life-hi/ory ( any entity1 e4g41 a p>ticle ( matt]1 a light-wave1 etc41 he obs]ves a sequ5ce ( po9ts 9 ! space-"t cont9uum2 t is1 ! life-hi/ory ( any entity is describ$ fully by a l9e 9 ?is space4 ,su* a l9e 0 call$ by ,m9k[ski a _w-l9e4 ,fur!r1 f a diff]5t po9t ( view1 all ( our obs]vations ( nature are 9 reality obs]vations ( co9cid5ces1 e4g41 if "o reads a !rmomet]1 :at he does is to note ! co9cid5ce ( ! end ( ! column ( m]cury ) a c]ta9 scale division on ! !rmomet] tube4 ,9 o!r words1 ?9k+ ( ! _w-l9e ( ! end ( ! m]cury column & ! _w-l9e ( ! scale division1 :at we h obs]v$ 0 ! int]section or cross+ ( ^! l9es4 ,9 a simil> mann] any obs]vation may be analyz$2 & rememb]+ t light rays1 a po9t on ! ret9a ( ! eye1 etc41 all h _! _w-l9es1 x w be recogniz$ t x is a p]fectly accurate /atem5t to say t e obs]vation is ! p]ception ( ! int]section ( _w-l9es4 ,fur!r1 s9ce all we "k ( a _w-l9e is ! result ( obs]vations1 x is evid5t t we d n "k a _w-l9e z a cont9u\s s]ies ( po9ts1 b simply z a s]ies ( discont9u\s po9ts1 ea* po9t be+ :]e ! p>ticul> _w-l9e 9 "q is cross$ by ano!r _w-l9e4 ,x is cle>1 moreov]1 t = ! description ( a _w-l9e we are n limit$ to ! p>ticul> set ( f\r or?ogonal axes adopt$ by ,m9k[ski4 ,we c *oose any set ( f\r-dim5sional axes we wi%4 ,x is fur!r evid5t t ! ma!matical expression = ! co9cid5ce ( two po9ts is absolutely indep5d5t ( our selection ( ref]5ce axes4 ,if we *ange our axes1 we w *ange ! coord9ates ( bo? po9ts simultane\sly1 s t ! "q ( axes ceases to be ( int]e/4 ,b our s-call$ laws ( nature are no?+ b descriptions 9 ma!matical language ( our obs]vations2 we obs]ve only co9cid5ces2 a sequ5ce ( co9cid5ces :5 put 9 ma!matical t]ms takes a =m :i* is indep5d5t ( ! selection ( ref]5ce axes2 !re=e ! ma!matical expression ( our laws ( nature1 ( e "*1 mu/ be su* t _! =m does n *ange if we make a trans=mation ( axes4 ,?is is a simple b f>-rea*+ d$uction4 ,!re is a geometrical me?od ( pictur+ ! effect ( a *ange ( axes ( ref]5ce1 i4e41 ( a ma!matical trans=mation4 ,to a man 9 a railway coa* ! pa? ( a drop ( wat] does n appe> v]tical1 i4e41 x is n p>allel to ! edge ( ! w9d[2 /ill less s does x appe> v]tical to a man p]=m+ manoeuvres 9 an airplane4 ,?is means t :]eas ) ref]5ce to axes fix$ to ! e>? ! pa? ( ! drop is v]tical2 ) ref]5ce to o!r axes1 ! pa? is n4 ,or1 /at+ ! conclusion 9 g5]al language1 *ang+ ! axes ( ref]5ce 7or effect+ a ma!matical trans=mation7 9 g5]al *anges ! %ape ( any l9e4 ,if "o imag9es ! l9e =m+ a "p ( ! space1 x is evid5t t if ! space is de=m$ by compression or expansion ! %ape ( ! l9e is *ang$1 & if suffici5t c>e is tak5 x is cle>ly possible1 by de=m+ ! space1 to make ! l9e take any %ape desir$1 or bett] /at$1 any %ape specifi$ by ! previ\s *ange ( axes4 ,x is ?us possible to picture a ma!matical trans=mation z a de=mation ( space4 ,?us ,i c draw a l9e on a %eet ( pap] or ( rubb] & by b5d+ & /ret*+ ! %eet1 ,i c make ! l9e assume a great v>iety ( %apes2 ea* ( ^! new %apes is a picture ( a suitable trans=mation4 ,n[1 consid] _w-l9es 9 our f\r-dim5sional space4 ,! complete record ( all our k is a s]ies ( sequ5ces ( int]sections ( su* l9es4 ,by analogy ,i c draw 9 ord9>y space a great numb] ( int]sect+ l9es on a %eet ( rubb]2 ,i c !n b5d & de=m ! %eet to please myself2 by s do+ ,i d n introduce any new int]sections nor d ,i alt] 9 ! lea/ ! sequ5ce ( int]sections4 ,s 9 ! space ( our _w-l9es1 ! space may be de=m$ 9 any imag9able mann] )\t introduc+ any new int]sections or *ang+ ! sequ5ce ( ! exi/+ int]sections4 ,x is ?is sequ5ce :i* gives u ! ma!matical expression ( our s-call$ exp]im5tal laws2 a de=mation ( our space is equival5t ma!matically to a trans=mation ( axes1 consequ5tly we see :y x is t ! =m ( our laws mu/ be ! same :5 ref]r$ to any & all sets ( axes1 t is1 mu/ rema9 unalt]$ by any ma!matical trans=mation4 ,n[1 at la/ we come to gravitation4 ,we c n imag9e any _w-l9e simpl] ?an t ( a p>ticle ( matt] left to itself2 we %all !re=e call x a /raight l9e4 ,our exp]i5ce is t two p>ticles ( matt] attract "o ano!r4 ,express$ 9 t]ms ( _w-l9es1 ?is means t1 if ! _w-l9es ( two isolat$ p>ticles come ne> ea* o!r1 ! l9es1 in/ead ( be+ /raight1 w be deflect$ or b5t 9 t[>ds ea* o!r4 ,! _w-l9e ( any "o p>ticle is !re=e de=m$2 & we h j se5 t a de=mation is ! equival5t ( a ma!matical trans=mation4 ,9 o!r words1 = any "o p>ticle x is possible to replace ! effect ( a gravitational field at any in/ant by a ma!matical trans=mation ( axes4 ,! /atem5t t ?is is always possible = any p>ticle at any in/ant is ,e9/e9's fam\s ,pr9ciple ( ,equival5ce4 ,let u re/ = a mom5t1 :ile ,i call att5tion to a mo/ int]e/+ co9cid5ce1 n to be ?\ght ( z an int]section ( _w-l9es4 ,x is said t ,newton's ?\ghts 7 direct$ to ! obs]vation ( gravitational ph5om5a by an apple fall+ on 8 head2 f ?is /rik+ ev5t he pass$ by natural /eps to a consid]ation ( ! univ]sality ( gravitation4 ,e9/e9 9 describ+ 8 m5tal process 9 ! evolution ( 8 law ( gravitation says t 8 att5tion 0 call$ to a new po9t ( view by discuss+ 8 exp]i5ces ) a man ^: fall f a high build+ he _h j witness$4 ,! man =tunately suff]$ no s]i\s injuries & assur$ ,e9/e9 t 9 ! c\rse ( 8 fall he _h n be5 consci\s 9 ! lea/ ( any pull d[nw>d on 8 body4 ,9 ma!matical language1 ) ref]5ce to axes mov+ ) ! man ! =ce ( gravity _h disappe>$4 ,?is is a case :]e by ! transf] ( ! axes f ! e>? itself to ! man1 ! =ce ( ! gravitational field is annull$4 ,! conv]se *ange ( axes f ! fall+ man to a po9t on ! e>? c\ld be consid]$ z introduc+ ! =ce ( gravity into ! equations ( motion4 ,ano!r illu/ration ( ! introduction into our equations ( a =ce by a means ( a *ange ( axes is furni%$ by ! ord9>y treatm5t ( a body 9 uni=m rotation ab\t an axis4 ,= in/ance1 9 ! case ( a s-call$ conical p5dulum1 t is1 ! motion ( a bob susp5d$ f a fix$ po9t by /r+1 :i* is s set 9 motion t ! bob describes a horizontal circle & ! /r+ !re=e describes a circul> cone1 if we transf] our axes f ! e>? & h !m rotate ar\nd ! v]tical l9e ?r\gh ! fix$ po9t ) ! same angul> velocity z ! bob1 x is necess>y to introduce into our equations ( motion a fictiti\s =ce call$ ! c5trifugal =ce4 ,no "o ev] ?9ks ( ?is =ce o!r ?an z a ma!matical quantity introduc$ into ! equations = ! sake ( simplicity ( treatm5t2 no physical mean+ is atta*$ to x4 ,:y %\ld !re be to any o!r s-call$ =ce1 :i* l c5trifugal =ce1 is indep5d5t ( ! nature ( ! matt]8 ,aga91 "h on ! e>? our s5sation ( weight is int]pret$ ma!matically by comb9+ expressions = c5trifugal =ce & gravity2 we h no di/9ct s5sation = ei!r sep>ately4 ,:y !n is !re any diff]5ce 9 ! ess5ce ( ! two8 ,:y n consid] !m bo? z br\ght into our equations by ! ag5cy ( ma!matical trans=mations8 ,?is is ,e9/e9's po9t ( view4 ,grant+1 !n1 ! pr9ciple ( equival5ce1 we c s *oose axes at any po9t at any in/ant t ! gravitational field w disappe>2 ^! axes are !re=e ( :at ,edd+ton calls ! ,galilean type1 ! simple/ possible4 ,consid]1 t is1 an obs]v] 9 a box1 or comp>tm5t1 :i* is fall+ ) ! accel]ation ( ! gravitational field at t po9t4 ,he w\ld n be consci\s ( ! field4 ,if !re 7 a projectile fir$ (f 9 ?is comp>tm5t1 ! obs]v] w\ld describe its pa? z be+ /raight4 ,9 ?is space ! inf9itesimal int]val betwe5 two space-"t po9ts w\ld !n be giv5 by ! =mula ds#b dx#ba dx#bb dx#bc dx#bd1 :]e ds is ! int]val & x#a1 x#b1 x#c1 x#d are coord9ates4 ,if we make a ma!matical trans=mation1 i4e41 use ano!r set ( axes1 ?is int]val w\ld obvi\sly take ! =m ds#b g#aa;dx#bcc g#bb;dx#bb g#cc;dx#bc g#dd;dx#bd #b;g#ab;dx#a;dx#b rmetc41 :]e x#a1 x#b1 x#c & x#d are n[ coord9ates ref]r+ to ! new axes4 ,?is relation involves t5 coeffici5ts1 ! coeffici5ts def9+ ! trans=mation4 ,b ( c\rse a c]ta9 dynamical value is also atta*$ to ! g's1 because by ! transf] ( our axes f ! ,galilean type we h made a *ange :i* is equival5t to ! introduction ( a gravitational field2 & ! g's mu/ specify ! field4 ,t is1 ^! g's are ! expressions ( our exp]i5ces1 & h5ce _! values c n dep5d ^u ! use ( any special axes2 ! values mu/ be ! same = all selections4 ,9 o!r words1 :atev] function ( ! coord9ates any "o g is = "o set ( axes1 if o!r axes are *os51 ?is g mu/ /ill be ! same function ( ! new coord9ates4 ,!re are t5 g's def9$ by diff]5tial equations2 s we h t5 cov>iant equations4 ,e9/e9 %[$ h[ ^! g's c\ld be reg>d$ z g5]aliz$ pot5tials ( ! field4 ,our own exp]im5ts & obs]vations ^u gravitation h giv5 u a c]ta9 k conc]n+ its pot5tial2 t is1 we "k a value = x :i* mu/ be s ne> ! tru? t we c prop]ly call x at lea/ a fir/ approximation4 ,or1 /at$ diff]5tly1 if ,e9/e9 succe$s 9 d$uc+ ! rigid value = ! gravitational pot5tial 9 any field1 x mu/ deg5]ate to ! ,newtonian value = ! great majority ( cases ) :i* we h actual exp]i5ce4 ,e9/e9's me?od1 !n1 0 to inve/igate ! functions 7or equations7 :i* w\ld satisfy ! ma!matical conditions j describ$4 ,a trans=mation f ! axes us$ by ! obs]v] 9 ! foll[+ box may be made s z to introduce into ! equations ! gravitational field recogniz$ by an obs]v] on ! e>? ne> ! box2 b ?is1 obvi\sly1 w\ld n be ! g5]al gravitational field1 because ! field *anges z "o moves ov] ! surface ( ! e>?4 ,a solution f\nd1 !re=e1 z j indicat$1 w\ld n be ! "o s\ght = ! g5]al field2 & ano!r mu/ be f\nd :i* is less /r+5t ?an ! =m] b r$uces to x z a special case4 ,he f\nd himself at lib]ty to make a selection f among sev]al possibilities1 & = sev]al reasons *ose ! simple/ solution4 ,he !n te/$ ?is decision by see+ if 8 =mul w\ld deg5]ate to ,newton's law = ! limit+ case ( velocities small :5 comp>$ ) t ( light1 because ?is condition is satisfi$ 9 ^? cases to :i* ,newton's law applies4 ,8 =mul satisfi$ ?is te/1 & he !re=e 0 able to ann\nce a law ( gravitation1 ( :i* ,newton's 0 a special =m = a simple case4 ,to ! ord9>y s*ol> ! difficulties surm\nt$ by ,e9/e9 9 8 inve/igations appe> /up5d\s4 ,x is n improbable t ! /atem5t :i* he is alleg$ to h made to 8 editor1 t only t5 m5 9 ! _w c\ld und]/& 8 treatm5t ( ! subject1 is true4 ,i am fully prep>$ to believe x1 & wi% to add t ,i c]ta9ly am n "o ( ! t54 ,b ,i c also say t1 aft] a c>eful & s]i\s /udy ( 8 pap]s1 ,i feel confid5t t !re is no?+ 9 !m :i* ,i c n und]/&1 giv5 ! "t to become famili> ) ! special ma!matical processes us$4 ,! m ,i "w ov] ,e9/e9's pap]s1 ! m impress$ ,i am1 n simply by 8 g5ius 9 view+ ! problem1 b also by 8 great te*nical skill4 ,foll[+ ! pa? outl9$1 ,e9/e91 z j said1 arriv$ at c]ta9 ma!matical laws = a gravitational field1 laws :i* r$uc$ to ,newton's =m 9 mo/ cases :]e obs]vations are possible1 b :i* l$ to diff]5t conclusions 9 a few cases1 k conc]n+ :i* we might obta9 by c>eful obs]vations4 ,i %all m5tion a few d$uctions f ,e9/e9's =mul4 #a4 ,if a heavy p>ticle is put at ! c5t] ( a circle1 &1 if ! l5g? ( ! circumf]5ce & ! l5g? ( ! diamet] are measur$1 x w be f\nd t _! ratio is n pi 7#c4adaei74 ,9 o!r words ! geometrical prop]ties ( space 9 su* a gravitational field are n ^? discuss$ by ,euclid2 ! space is1 !n1 non-,euclidean4 ,!re is no way by :i* ?is d$uction c be v]ifi$1 ! diff]5ce betwe5 ! pr$ict$ ratio & pi is too m9ute = u to hope to make our measurem5ts ) suffici5t exactness to det]m9e ! diff]5ce4 #b4 ,all ! l9es 9 ! sol> spectrum %\ld ) ref]5ce to l9es obta9$ by t]re/rial s\rces be displac$ slightly t[>ds long] wave-l5g?s4 ,! am\nt ( displacem5t pr$ict$ = l9es 9 ! blue end ( ! spectrum is ab\t "o-hundr$? ( an ,ang/rom unit1 a quantity well )9 exp]im5tal limits4 ,un=tunately1 z f> z ! te/+ ( ?is pr$iction is conc]n$1 !re are sev]al physical causes :i* are also op]at+ to cause displacem5t ( ! spectrum-l9es2 & s at pres5t a decision c n be r5d]$ z to ! v]ification4 ,/4 ,john & o!r work]s at ! ,m\nt ,wilson ,obs]vatory h ! "q "u inve/igation4 #c4 ,accord+ to ,newton's law an isolat$ planet 9 its motion ar\nd a c5tral sun w\ld describe1 p]iod aft] p]iod1 ! same elliptical orbit2 :]eas ,e9/e9's laws lead to ! pr$iction t ! successive orbits trav]s$ w\ld n be id5tically ! same4 ,ea* revolution w\ld />t ! planet (f on an orbit v approximately elliptical1 b ) ! major axis ( ! ellipse rotat$ slightly 9 ! plane ( ! orbit4 ,:5 calculations 7 made = ! v>i\s planets 9 our sol> sy/em1 x 0 f\nd t ! only "o :i* 0 ( int]e/ f ! /&po9t ( v]ification ( ,e9/e9's =mul 0 ,m]cury4 ,x has be5 kn[n = a long "t t !re 0 actually su* a *ange z j describ$ 9 ! orbit ( ,m]cury1 am\nt+ to #egd'' ( arc p] c5tury2 & x has be5 %[n t ( ?is a rotation ( #ecb'' 0 due to ! direct action ( o!r planets1 ?us leav+ an unexpla9$ rotation ( #db'' p] c5tury4 ,e9/e9's =mul pr$ict$ a rotation ( #dc''1 a /rik+ agreem5t4 #d4 ,9 accordance ) ,e9/e9's =mul a ray ( light pass+ close to a heavy piece ( matt]1 ! sun1 = in/ance1 %\ld exp]i5ce a s5sible deflection 9 t[>ds ! sun4 ,?is might be expect$ f g5]al consid]ation ( en]gy 9 motion2 en]gy & mass are g5]ally consid]$ to be id5tical 9 ! s5se t an am\nt ( en]gy ,e has ! mass ,e#a;c#b :]e c is ! velocity ( light2 & consequ5tly a ray ( light might fall )9 ! prov9ce ( gravitation & ! am\nt ( deflection to be expect$ c\ld be calculat$ by ! ord9>y =mula = gravitation4 ,ano!r po9t ( view is to consid] aga9 ! obs]v] inside ! comp>tm5t fall+ ) ! accel]ation ( ! gravitational field4 ,to him ! pa? ( a projectile & a ray ( light w\ld bo? appe> /raight2 s t1 if ! projectile _h a velocity equal to t ( light1 x & ! light wave w\ld travel side by side4 ,to an obs]v] outside ! comp>tm5t1 e4g41 to "o on ! e>?1 bo? w\ld !n appe> to h ! same deflection ow+ to ! sun4 ,b h[ mu* w\ld ! pa? ( ! projectile be b5t8 ,:at w\ld be ! %ape ( its p>abola8 ,"o might apply ,newton's law2 b1 accord+ to ,e9/e9's =mul1 ,newton's law %\ld be us$ only = small velocities4 ,9 ! case ( a ray pass+ close to ! sun x 0 decid$ t accord+ to ,e9/e9's =mula !re %\ld be a deflection ( #a''4ge :]eas ,newton's law ( gravitation pr$ict$ half ?is am\nt4 ,c>eful plans 7 made by v>i\s a/ronom]s1 to inve/igate ?is "q at ! sol> eclipse la/ ,may1 & ! result ann\nc$ by ,dyson1 ,edd+ton & ,crommel91 ! lead]s ( a/ronomy 9 ,engl&1 0 t !re 0 a deflection ( #a''4i4 ,( c\rse ! detection ( su* a m9ute deflection 0 an extraord9>ily difficult matt]1 s _m corrections _h to be appli$ to ! orig9al obs]vations2 b ! names ( ! m5 :o record ! conclusions are su* z to inspire confid5ce4 ,c]ta9ly any effect ( refraction seems to be exclud$4 ,x is ?us se5 t ! =mul d$uc$ by ,e9/e9 h be5 confirm$ 9 a v>iety ( ways & 9 a mo/ brilliant mann]4 ,9 connection ) ^! =mul "o "q mu/ arise 9 ! m9ds ( ev]yone2 by :at process1 :]e 9 ! c\rse ( ! ma!matical developm5t1 does ! idea ( mass reveal itself8 ,x 0 n 9 ! equations at ! beg9n+ & yet "h x is at ! end4 ,h[ does x appe>8 ,z a matt] ( fact x is fir/ se5 z a con/ant ( integration 9 ! discussion ( ! problem ( ! gravitational field due to a s+le p>ticle2 & ! id5tity ( ?is con/ant ) mass is prov$ :5 "o comp>es ,e9/e9's =mul ) ,newton's law :i* is simply its deg5]at$ =m4 ,?is mass1 ?\gh1 is ! mass ( :i* we become aw>e ?r\gh our exp]i5ces ) weight2 & ,e9/e9 proce$$ to prove t ?is quantity :i* ent]$ z a con/ant ( integration 9 8 ideally simple problem also obey$ ! laws ( cons]vation ( mass & cons]vation ( mom5tum :5 he inve/igat$ ! problems ( two & m p>ticles4 ,!re=e ,e9/e9 d$uc$ f 8 /udy ( gravitational fields ! well-kn[n prop]ties ( matt] :i* =m ! basis ( !oretical me*anics4 ,a fur!r logical consequ5ce ( ,e9/e9's developm5t is to %[ t en]gy has mass1 a concept ) :i* e "o n[adays is famili>4 ,! description ( ,e9/e9's me?od :i* ,i h giv5 s f> is simply ! /ory ( "o success aft] ano!r2 & x is c]ta9ly fair to ask if we h at la/ rea*$ f9ality 9 our inve/igation ( nature1 if we h atta9$ to tru?4 ,are !re no out/&+ difficulties8 ,is !re no possibility ( error8 ,c]ta9ly1 n until all ! pr$ictions made f ,e9/e9's =mul h be5 inve/igat$ c mu* be said2 & fur!r1 x mu/ be se5 :e!r any o!r l9es ( argum5t w lead to ! same conclusions4 ,b )\t wait+ = all ?is !re is at lea/ "o difficulty :i* is app>5t at ?is "t4 ,we h discuss$ ! laws ( nature z indep5d5t 9 _! =m ( ref]5ce axes1 a concept :i* appeals /rongly to our philosophy2 yet x is n at all cle>1 at fir/ sight1 t we c be ju/ifi$ 9 our belief4 ,we c n imag9e any way by :i* we c become consci\s ( ! translation ( ! e>? 9 space2 b by means ( gyroscopes we c le>n a great deal ab\t its rotation on its axis4 ,we c\ld locate ! positions ( its two poles1 & by wat*+ a ,f\cault p5dulum or a gyroscope we c obta9 a numb] :i* we int]pret z ! angul> velocity ( rotation ( axes fix$ 9 ! e>?2 angul> velocity ) ref]5ce to :at8 ,:]e is ! fundam5tal set ( axes8 ,?is is a real difficulty4 ,x c be surm\nt$ 9 sev]al ways4 ,e9/e9 himself has outl9$ a me?od :i* 9 ! end am\nts to assum+ ! exi/5ce on ! conf9es ( space ( va/ quantities ( matt]1 a proposition :i* is n attractive4 de,sitter has sugge/$ a peculi> quality ( ! space to :i* we ref] our space-"t coord9ates4 ,! consequ5ces ( ?is are mo/ int]e/+1 b no decision c z yet be made z to ! ju/ification ( ! hypo!sis4 ,9 any case we c say t ! difficulty rais$ is n "o t de/roys ! real value ( ,e9/e9's "w4 ,9 conclusion ,i wi% to emphasize ! fact1 :i* %\ld be obvi\s1 t ,e9/e9 has n attempt$ any explanation ( gravitation2 he has be5 occupi$ ) ! d$uction ( its laws4 ,^! laws1 toge!r ) ^? ( electromagnetic ph5om5a1 comprise our /ore ( k4 ,!re is n ! slighte/ indication ( a me*anism1 mean+ by t a picture 9 t]ms ( our s5ses4 ,9 fact :at we h le>n$ has be5 to realize t our desire to use su* me*anisms is futile4 ,,! ,,deflection ,,( ,,light ,,by ,,gravitation ,,& ,,! ,,e9/e9 ,,!ory ,,( ,,relativity4 #af ,sir ,frank ,dyson ! ,a/ronom] ,royal ,! purpose ( ! exp$ition 0 to det]m9e :e!r any displacem5t is caus$ to a ray ( light by ! gravitational field ( ! sun1 & if s1 ! am\nt ( ! displacem5t4 ,e9/e9's !ory pr$ict$ a displacem5t v>y+ inv]sely z ! di/ance ( ! ray f ! sun's c5t]1 am\nt+ to #a''4ge = a /> se5 j graz+ ! sun4444 ,a /udy ( ! conditions ( ! #aiai eclipse %[$ t ! sun w\ld be v favorably plac$ among a gr\p ( bright />s--9 fact1 x w\ld be 9 ! mo/ favorable possible position4 ,a /udy ( ! conditions at v>i\s po9ts on ! pa? ( ! eclipse1 9 :i* ,mr4 ,h9ks help$ u1 po9t$ to ,sobral1 9 ,brazil1 & ,pr9cipe1 an isl& (f ! we/ coa/ ( ,africa1 z ! mo/ favorable /ations4444 ,! ,gre5wi* p>ty1 ,dr4 ,crommel9 & ,mr4 ,davidson1 rea*$ ,brazil 9 ample "t to prep>e = ! eclipse1 & ! usual prelim9>y focus+ by photograph+ /ell> fields 0 c>ri$ out4 ,! day ( ! eclipse op5$ cl\dy1 b cle>$ lat]1 & ! obs]vations 7 c>ri$ out ) almo/ complete success4 ,) ! a/rographic telescope ,mr4 ,davidson secur$ #ae out ( #ah photographs %[+ ! requir$ /ell> images4 ,totality la/$ #f m9utes1 & ! av]age exposure ( ! plates 0 #e to #f seconds4 ,dr4 ,crommel9 ) ! o!r l5s _h #g successful plates out ( #h4 ,! unsuccessful plates 7 spoil$ = ?is purpose by ! cl\ds1 b %[ ! rem>kable prom95ce v well4 ,:5 ! plates 7 develop$ ! a/rographic images 7 f\nd to be out ( focus4 ,?is is attribut$ to ! effect ( ! sun's heat on ! coelo/at mirror4 ,! images 7 fuzzy & q diff]5t f ^? on ! *eck-plates secur$ at night be=e & aft] ! eclipse4 ,=tunately ! mirror :i* f$ ! #d-;in* l5s 0 n affect$1 & ! /> images secur$ ) ?is l5s 7 good & simil> to ^? got by ! night-plates4 ,! obs]v]s /ay$ on 9 ,brazil until ,july to secure ! field 9 ! night sky at ! altitude ( ! eclipse epo* & "u id5tical in/rum5tal conditions4 ,! plates 7 measur$ at ,gre5wi* imm$iately aft] ! obs]v]s' return4 ,ea* plate 0 measur$ twice ov] by ,messrs4 ,davidson & ,furn]1 & ,i am satisfi$ t su* faults z lie 9 ! results are 9 ! plates !mselves & n 9 ! measures4 ,! figures obta9$ may be briefly summ>iz$ z foll[s3 ,! a/rographic plates gave #j''4ig = ! displacem5t at ! limb :5 ! scale-value 0 det]m9$ f ! plates !mselves1 & #a''4dj :5 ! scale-value 0 assum$ f ! *eck plates4 ,b ! mu* bett] plates gave = ! displacem5t at ! limb #a''4ih1 ,e9/e9's pr$ict$ value be+ #a''4ge4 ,fur!r1 = ^! plates ! agreem5t 0 all t c\ld be expect$4444 ,aft] a c>eful /udy ( ! plates ,i am prep>$ to say t !re c be no d\bt t !y confirm ,e9/e9's pr$iction4 ,a v def9ite result has be5 obta9$ t light is deflect$ accord+ to ,e9/e9's law ( gravitation4 ,pr(essor ,a4 ,s4 ,edd+ton ,royal ,obs]vatory ,mr4 ,cott+ham & ,i left ! o!r obs]v]s at ,madeira & arriv$ at ,pr9cipe on ,april #bc4444 ,we soon realiz$ t ! prospect ( a cle> sky at ! end ( ,may 0 n v good4 ,n ev5 a heavy ?und]/orm on ! morn+ ( ! eclipse1 ?ree weeks aft] ! end ( ! wet season1 sav$ ! situation4 ,! sky 0 completely cl\dy at fir/ contact1 b ab\t half an h\r be=e totality we began to see glimpses ( ! sun's cresc5t ?r\gh ! cl\ds4 ,we c>ri$ out our program exactly z arrang$1 & ! sky mu/ h be5 cle>] t[>ds ! end ( totality4 ,( ! #af plates tak5 dur+ ! five m9utes ( totality ! fir/ t5 %[$ no />s at all2 ( ! lat] plates two %[$ five />s ea*1 f :i* a result c\ld be obta9$4 ,comp>+ !m ) ! *eck-plates secur$ at ,ox=d be=e we w5t out1 we obta9$ z ! f9al result f ! two plates = ! value ( ! displacem5t ( ! limb #a''4f #j4c4444 ,?is result supports ! figures obta9$ at ,sobral4444 ,i w pass n[ to a few words on ! mean+ ( ! result4 ,x po9ts to ! l>g] ( ! two possible values ( ! deflection4 ,! simple/ int]pretation ( ! b5d+ ( ! ray is to consid] x z an effect ( ! weight ( light4 ,we "k t mom5tum is c>ri$ along on ! pa? ( a beam ( light4 ,gravity 9 act+ creates mom5tum 9 a direction diff]5t f t ( ! pa? ( ! ray & s causes x to b5d4 ,= ! half-effect we h to assume t gravity obeys ,newton's law2 = ! full effect :i* has be5 obta9$ we mu/ assume t gravity obeys ! new law propos$ by ,e9/e94 ,?is is "o ( ! mo/ crucial te/s betwe5 ,newton's law & ! propos$ new law4 ,e9/e9's law _h already indicat$ a p]turbation1 caus+ ! orbit ( ,m]cury to revolve4 ,t confirms x = relatively small velocities4 ,go+ to ! limit1 :]e ! spe$ is t ( light1 ! p]turbation is increas$ 9 su* a way z to d\ble ! curvature ( ! pa?1 & ?is is n[ confirm$4 ,?is effect may be tak5 z prov+ ,e9/e9's law r ?an 8 !ory4 ,x is n affect$ by ! failure to detect ! displacem5t ( ,fraunh(] l9es on ! sun4 ,if ?is latt] failure is confirm$ x w n affect ,e9/e9's law ( gravitation1 b x w affect ! views on :i* ! law 0 arriv$ at4 ,! law is "r1 ?\gh ! fundam5tal ideas und]ly+ x may yet be que/ion$4444 ,"o fur!r po9t mu/ be t\*$ ^u4 ,are we to attribute ! displacem5t to ! gravitational field & n to ! refract+ matt] ar\nd ! sun8 ,! refractive index requir$ to produce ! result at a di/ance ( #ae' f ! sun w\ld be t giv5 by gases at a pressure ( #a_/fj to #a_/bjj ( an atmosph]e4 ,?is is ( too great a d5sity consid]+ ! dep? ?r\gh :i* ! light w\ld h to pass4 ,sir ,j4 ,j4 ,?omson ,presid5t ( ! ,royal ,society 444 ,if ! results obta9$ _h be5 only t light 0 affect$ by gravitation1 x w\ld h be5 ( ! greate/ importance4 ,newton1 did1 9 fact1 sugge/ ?is v po9t 9 8 ,optics1 & 8 sugge/ion w\ld presumably h l$ to ! half-value4 ,b ?is result is n an isolat$ "o2 x is "p ( a :ole cont95t ( sci5tific ideas affect+ ! mo/ fundam5tal concepts ( physics4444 ,?is is ! mo/ important result obta9$ 9 connection ) ! !ory ( gravitation s9ce ,newton's day1 & x is fitt+ t x %\ld be ann\nc$ at a meet+ ( ! society s closely connect$ ) him4 ,! diff]5ce betwe5 ! laws ( gravitation ( ,e9/e9 & ,newton come only 9 special cases4 ,! real int]e/ ( ,e9/e9's !ory lies n s mu* 9 8 results z 9 ! me?od by :i* he gets !m4 ,if 8 !ory is "r1 x makes u take an entirely new view ( gravitation4 ,if x is su/a9$ t ,e9/e9's reason+ holds good--& x has surviv$ two v sev]e te/s 9 connection ) ! p]ihelion ( m]cury & ! pres5t eclipse--!n x is ! result ( "o ( ! highe/ a*ievem5ts ( human ?\ght4 ,! weak po9t 9 ! !ory is ! great difficulty 9 express+ x4 ,x w\ld seem t no "o c und]/& ! new law ( gravitation )\t a ?or\gh k ( ! !ory ( inv>iants & ( ! calculus ( v>iations4 ,"o o!r po9t ( physical int]e/ arises f ! discussion4 ,light is deflect$ 9 pass+ ne> huge bodies ( matt]4 ,?is involves alt]ations 9 ! electric & magnetic field4 ,?is1 aga91 implies ! exi/5ce ( electric & magnetic =ces outside matt]--=ces at pres5t unkn[n1 ?\gh "s idea ( _! nature may be got f ! results ( ?is exp$ition4 ,,notes #a ,see ,note #a at ! end ( ! volume4 #b ,see ,note #b4 #c ,see ,note #c4 #d ,a circle--9 our case ! horizon--is measur$ by divid+ ! circumf]5ce into #cfj p>ts2 ea* "p is call$ a degree4 ,ea* degree is divid$ into #fj m9utes1 & ea* m9ute into #fj seconds4 #e ,see page #aac4 #f ,see ,note #d4 #g ,see ,note #e4 #h ,see ,note #f4 #i ,see ,note #g4 #aj ,see ,note #h4 #aa ,see ,note #i4 #ab ,see page #ic4 #ac ,?is has s9ce be5 translat$ into ,engli% by ,dr4 ,lawson & publi%$ by ,me?u5 7,london74 ,s9ce ! above has be5 writt5 two excell5t books h be5 publi%$4 ,"o is by ,pr(4 ,a4 ,s4 ,edd+ton1 ,space1 ,"t & ,gravitation 7,cambridge ,univ4 ,press1 #aibj74 ,! o!r1 some:at m ( a philosophical "w1 is ,pr(4 ,moritz ,s*lick's ,space & ,"t 9 ,contempor>y ,physics 7,ox=d ,univ4 ,press1 #aibj74 ,?\gh publi%$ z e>ly z #ahig1 ,b]tr& ,russell's ,an ,essay on ! ,f\ndations ( ,geometry 7,cambridge ,univ4 ,press1 #ahig7 conta9s a f9e acc\nt ( non-,euclidean geometry4 #ad ,republi%$ by p]mission f ,sci5ce4 #ae ,presid5tial address deliv]$ at ! ,/4 ,l\is meet+ ( ! ,physical ,society1 ,decemb] #cj1 #aiai4 ,republi%$ by p]mission f ,sci5ce4 #af ,f a report 9 ,! ,obs]vatory1 ( ! ,jo9t ,eclipse ,meet+ ( ! ,royal ,society & ! ,royal ,a/ronomical ,society1 ,novemb] #f1 #aiai4