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Transcript of Fizeau (1859)-Hypotheses on Luminous Ether and on an

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    NASA TECHNICAL TRANSLATION NASA F-13,423

    HYPOTHESES ON LUMINOUS ETHER AND ON AN EXPERIMENTTHAT APPEARS TO DEMONSTRATE THAT THE MOTION OF BODIES CHANGES

    THJ3 VELOCITY WITH WHICH LIGHT PROPAGATES IN THEIR INTERIOR

    H . F i z e a u

    T r a n s l a t i o n of "Sur les h y p o t h e s e s relatives al'ether lumiaeux", Annales de Chemie e t d e P h y s i q u e ,3rd Series, Vol. 57 , December 18 59 , pp. 3 85-404.

    386(THRU)L? -J

    Y (PAGES,5 -__- L/s ( N A S A CR OR IMX OR AD NUMBER) (CATEGORY)

    NATIONAL AERONAUTICS AND SPACE ADMINISTRATIONWASHINGTON, D. C . 20546 APRIL 1 9 7 1

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    HYPOTHESES ON LUMINOUS ETHER-4ND ON AN EXPERIMENT THAT APPEARS TO DEMONSTRATE THAT

    THE MOTION OF BODIES CHANGES THE VELOCITY WITHWHICH LIGHT PWPAGATES I N THEIR INTERIOR

    I.izeau

    ABSTRACT. The author d iscusses F resnel 's hypothesist o e x pl a in l i g h t a b be r at i on and l i g h t waves.t o de termine the poss ib l e changes in t he speed of l i gh tt ravel ing through t ransparent bodies is discussed , as w e l las the a pparatus used fo r such experiments. The authorpresents c a lcul a t io ns and d iscusses re su l t s and poss i b lesou rces of e r ro r .

    An experiment

    Several theor ies on w a v e systems have been proposed t o attempt t o expl ainthe abbera t ion of l i g h t . F i r s t , F r e sn e l a nd , m re recently, Doppler, Stokes,Cha l l i s and sever a l o the rs have publ ished papers on th is subject, but i t doesnot seem th a t any of the theor ies so f a r proposed have been able t o completelys a t i s f y t h e p h y s i c i s t s .p rope r t i e s of the luminous ether and i t s re la t ionsh ip t o ponde rable matter,i t has been nec essa ry t o i ntr oduc e hypotheses, amoag which are those whichare more o r less probable, b ut none t ha t can be considered as proven.

    Because of a lack of de fi ni te knowledge about the

    These can be reduced t o th re e main hypotheses, a l l of which refer t o t h es ta te i n which the e the r in s ide a tran spar ent body should be considered:

    ~ ~ ~- ~ ~*Numbers i n the margin ind ica te the pag ina tion i n the o r ig i na l fo re ign tex t .1

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    The ethe r adheres, o r i s fix ed, to th e molecules of the body, and,consequently, sha res i n the motion th at may be imposed on the body;

    O r , the e the r is fr ee and independent, and is not ca rri ed along by th ebody i n i t s motion;

    O r , f i n a l l y , a t hi r d hypoth esi s which borrows from each of t he two above,/386n which onl y a port ion of t he e t he r would be f ree , while th e o ther por t ion -

    ould be fixed t o th e molecules of th e body and would so le ly shar e i n i t smotion.

    This last hypothesis , po stu la ted by Fresnel , w a s conceived i n o r d er t os a t i s f y a t t h e same time th e phenomenon of a bbe ra ti on, and a famous experimentby Arago, i n which he had shown th a t the motion of the Ear th d id not have anye f f ec t upon the re f rac t ion va lue of s t a r l i g h t in a prism.could be explained through Fres nel 's hypothes is wit h admirable prec isio n.However, Fresnel's hypothesis is not regarded today as abso lu te t ru th , and therel ati ons hip s between eth er and ponderable matter are s t i l l genera l ly consi-dered as uncer ta in and hard t o unders tand. This i s because Fresnel's mechac.--c a l conception seems too unusual t o be accepted without d ir ec t proof , orperhaps because i t seemed equal ly po ssi ble t o sa t i s f y th e observed phenomenaw i t h e i t h e r of t he two other hypotheses . Perhaps , f i na l l y , as o the r phys ic i s t shave thought , c er ta i n results from th i s theory seemed contrar y t o experience.

    These two phenomena

    The following considerations have led me t o t r y an experiment, th e rest l tsof which, I b e l i ev e , s ho ul d c l a r i f y t h i s matter.

    I t is poss ib le in th e thr ee hypotheses enumerated above th at , i f the bodyis in motion, the vel oci ty a t which light w i l l go through i t w i l l be d if ferent :from tha t observed i f the body were a t rest.th e motion of t he body would have a d i f f e r e n t e f f e c t u pon t h e l i g h t v e lo c i t y.

    For each of these hypotheses,

    Thus, i f e t h e r is supposed be fixe d t o t he body Curing the l a t t e r ' smotion, t h e v e lo c i t y of l i g h t w i l l be augmented by t h a t of the body, i f t he2

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    dir ec t ion of t he l i gh t ray and of th e motion are t h e same.

    I f t h e e t h e r is supposed to be f re e , the ve loc i t y of l i g h t w i l l notchange.

    F i n a ll y , i f o n l y p a r t of t h e e t h e r is at tached t o the body, the ve loc i tyo f l i g h t w i l l be augmented only by a f ra c t i on of t he ve loci ty of the body,and not by th e t o t a l amount as i n t h e f i r s t h yp ot he si s.as evident as in t he f i r s t two hypotheses, but Fresnel has made i t clear t h a ti t may be upheld by very cr ed ib le mechanical consid eration s.

    This result i s notI 387-

    I t i s supposed tha t th e speed or l i g h t i n a body a t rest o r i n motion maybe determined exactly.corresponding t o t he s ta te of rest incre ases by the t o t a l speed of motion ofthe body, t h i s w i l l conform with t he f i r s t hypothesis .

    I f th e body is i n motion, and i f the speed of l i gh t

    I f the speed o f l i gh t i s the same in both cases (body a t rest o r i nmotion), th e second hypothes is w i l l b e s a t i s f i e d .

    I f , on the o ther hand, the speed of l i gh t corresponding to the s t a t e ofrest i s augmented by a f rac t ion o f t he speed o f the body, the re su l t w i l l b ei n agreement with the th ir d hypothesis .

    It is t r u e t h a t l i g h t t ravels a t such a gr ea t spee d -when compared t othe speeds tha t w e may impart to th e bodies- hat the change in the speedof l i g h t i s too s m a l l t o be observable. Nonetheless, by choosing the mostfavorable circumstances, it ha s seemed t o me poss ib le to submi t two media, air andand water, t o a dec is ive test.th ei r components o r molecules, can be acc eler ated t o gre at speeds.

    These two media, because of th e mob ili ty of

    W owe t o Arago a method of observation, based on interference, whichreveals the smallest v a r i a ti o n s i n t h e r e f r a c t i v e i n d i ce s of bodies. Aragoan d Fresnel have demons trated th e ex t rao rd ina ry se ns i t iv i t y of th i s

    3

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    procedure through sev era l d e l i ca t e observat ions , such as t h e d i f f e r e n c e i nrefraction between dry and humid air.

    I t has seemed to me t h a t a mode of observation based on t h i s p r i n c i p l e i sthe only one th at reve als the changes i n speed due t o motion.producing in terference f r inges with tw o l i gh t r ays , a f t e r they have passedthrough two paral le l tubes i n which air and water may f l o a t a t grezt speedsand i n opposi te d irec t ion s .needed several innovations, which I w i l l ind ica te .

    I t c o n s i st s i n

    The special goa l t h a t I ha ve t r i e d t o a t t a i n ha s

    Great d i f f i c u l t i e s were encountered relat ive t o t h e l i g h t i n t e ns i t y. Thetubes, with an i n t e r i o r d i a m e t e r of 5.3 mm, had t o be t r ave rsed by the l ig h tnea r th e i r cen te r and no t nea r the i r s ides .more e longated than usual , and , consequent ly, t he l i gh t in t ens i t y a t thepo in t of o r i g in of the f r inges w a s very l ow.

    Thus, th e tw o s l i t s had t o be

    This inconvenience w a s overcome by placing a convergent l ens behind thes l i t s .t h e l i g h t i n t e n s i t y i s f a i r l y g r e a t .

    Then the fringes were observed a t the point of th e beam junctio n where

    Since the length of th e tubes w a s f a i r l y l a r g e , 1. 487 m , i t was fearedtha t any d if feren ce i n temperature or pressure between t he tw o tubes wouldi n i t i a t e a considerable d isp lacement of the f r i nge s , which i n tu rn couldccmq-letely mask the displacement due to motion.

    This d if f ic ul t y has been obviated by means of a telescope having amirror a t i t s fo ca l point. This way each beam is fo rced to t r ave rse the twotubes success ive ly , so th at both beams covered exac tly th e same d js tance , bu t i nopposi te d i rec t ion . The ef fe ct s produced by pressure o r temperature ar e thuscompensated. I have sa t i s f ie d myself , through several experiments, that t h ecompensation is complete, and regardless of any changes i n den sity o r tempera-tu re intr oduced upon th e medium i n one of th e tubes, th e fri nge s keep th ei rsame exact posi t ion . In th i s type of a rrangement, th e f r inges should be

    I 3 8 8-

    /389-4

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    observed a t t h e same poin t of depart ure of the beams; su nl ig ht i s ac-s i t iedla te ra l l y , and d