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U N I V E R S I T É L I B R E D E B R U X E L L E S

DIGITHÈQUE

Université libre de Bruxelles

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Institut international de physique Solvay (1958). La structure et l'évolution de l'univers:

onzième Conseil de physique tenu à l'Université de Bruxelles du 9 au 13 juin 1958.

Bruxelles: R. Stoops.

Disponible à / Available at permalink :

_____________ ______________ (English version below)

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LA STRUCTURE

ET

L'ÉVOLUTION DE L'UNIVERS

INSTITUT INTERNATIONAL DE PHYSIQUE SOLVAY

ONZIÈME CONSEIL DE PHYSIQUE

tenu à l'Université de Bruxelles du 9 au 13 juin 1958 lA STRUCTURE ET

L'ÉVOlUTIOA DE TUNIVERS

RAPPORTS ET DISCUSSIONS

publiés sous les auspices du Comité Scientifique de l'Institut

R. STÔOPS

Editeur

76-78, COUDENBERG, BRUXELLES, BELGIQUE

1958

INTRODUCTION

LE ONZIÈME CONSEIL DE PHYSIQUE SOLVAY

Le XI® Conseil de Physique Solvay s'est tenu à Bruxelles, dans les locaux de l'Université, du lundi 9 au vendredi 13 juin 1958, suivant les dispositions arrêtées par la Commission Administrative, composée comme suit :

Président :

M. Jules BORDET, prix Nobel.

Membres :

MM. Ernest-J. SOLVAY, Paul DE GROOTE, Ilya PRIGOGINE.

Secrétaire

M. Frans-H. van den DUNGEN.

Le Comité Scientifique qui avait arrêté le programme des rapports

était formé de :

Président :

Sir W. Lawrence BRAGG, prix Nobel.

Membres :

Prof. C.J. GORTER, Prof. C. M0LLER, Prof. J.R. OPPEN HEIMER, Prof. W. PAULI, prix Nobel, Prof. Fr. PERRIN. Le septième membre, M. MOTT, avait fait part de son regret de ne pouvoir être présent. Les membres rapporteurs du Conseil étaient :

MM. V. A. AMBARTSUMIAN, Academy of Sciences of

Armenia.

W.

BAADE, Mt Wilson and Palomar Observatories.

F. HOYLE, St. John's College.

O.B. KLEIN, Stockholm University.

G. LEMAITRE, Université de Louvain.

A.C.B. LOVELL, Jodrell Bank Experimental Station.

J.H. OORT, Sterrewacht te Leiden.

A.T. SANDAGE, Mt Wilson and Palomar Observatories.

H. C. VAN DE HULST, Sterrewacht te Leiden.

VII Les communications de M. A. T. SANDAGE et M. W. BAADE

étaient orales.

Les membres invités étaient :

MM. M. FIERZ, LFniversity of Basle.

T. GOLD, Harvard University.

O. HECKMANN, Observatory of Hamburg.

B.V. KUKARKIN, Sternberg Institute of Moscow.

P. LEDOUX, Université de Liège.

W.H. Mac CREA, Royal Holloway College.

W.W. MORGAN, Yerkes Observatory.

L. ROSENFELD, Manchester University.

E. SCHATZMAN, Faculté des Sciences de Paris.

H. SHAPLEY, Harvard University.

P. SWINGS, Université de Liège.

J.A. WHEELER, University of Princeton.

H. ZANSTRA, University of Amsterdam.

H. BONDI, King's College, London (Secretary)

Les membres auditeurs, membres du corps professoral de l'Uni versité de Bruxelles étaient ;

MM. J. COX, R. DEBEVER, M. DEMEUR, J. GEHENIAU.

MM.

GOLD, HECKMANN, MORGAN et WHEELER ont

présenté des notes écrites. Le Prof. ROSSLAND. de l'Université d'Oslo, n'a pu se joindre aux invités. Le secrétaire a été aidé dans sa tâche par les secrétaires adjoints: Mmes R. PANKOWSKI-FERN, A. PEETERS-SPITAELS, M^e A. HULEUX, MM. Ch. LAFLEUR, J. HOUGARDY, R. VAN GEEN, membres du personnel scientifique de l'Université. Le Conseil Scientifique a chargé le Prof. J. GEHENIAU de diriger l'édition du volume contenant les rapports et discussions; il a été aidé dans cette tâche par M. R. VAN GEEN, assistant à l'Université de Bruxelles. Les Autorités de l'Université ont reçu les membres du Conseil le lundi 9 à 17 heures dans la salle du Conseil. Le jeudi 12, à 21 heures, un dîner a réuni les participants au Resturant de l'Atomium dans le cadre de l'Exposition Universelle de Bruxelles 1958. VIll

ACKNOWLEDGEMENT.

At the end of the general discussion of Friday, June 13, Dr. Harlow

SHAPLEY made this speech :

Mr. Chairman, may I hâve a moment for a bénédiction? I desire to assure you and your colleagues on the Solvay Committee that we, your guests, are indeed grateful for the opportunity of convening and conferring. We hâve, of course nothing but enthusiasm for the magical chemistry of Solvay cuisine - enthusiasm for the processing of potables and comestibles. We enjoyed the high living - especially last nights' high feeding in the uppermost bail of the Atomium. Our thanks are also due to Professor F. H. van den Dungen and his assistants for the organisation of the Congress. In particular, our thanks go to you. Sir Lawrence for your sympatheiic management, and for your skill in genially presiding over these sessions. You hâve maintained a neutral - I might say a neutron - pose during the turbulence, during the négative and positive charges and counter- charges, the explosions and implosions of gas and argument. We wish you. Sir Lawrence, you and your colleagues, many more pleasant and useful Solvay Conférences- IX

RAPPORTS

ET

DISCUSSIONS

I. GENERAL STATEMENT

OF

COSMOLOGICAL THEORY

iI àA

The Primaeval Atom Hypothesis

and the problem of the Clusters of Galaxies by G. LEMAITRE

This report is divided in three parts.

In the first one, we discuss the general aspects of cosmology and point ont their relations with Geometry, quantum theory and even with their inévitable philosophical background. This is donc without any intention to polemize against other points of view than the one which we hâve adopted, but, simply to make clear what are our own assumptions. The second part is an exposition of the successive processes which arise in our cosmology and lead, in the order stated, from cosmic rays to gaseous clouds and then to proto-galaxies, with stars forma tion within them, and, finally, to the arrangement of the galaxies in clusters, with large peculiar velocities of their individual galaxies. This makes possible to define what we call the problem of the clusters of galaxies and the third part reports on some results which point towards its solution.

1. GENERAL ASPECTS

Space.

Cosmology is essentially related to Geometry, and, in fact geo metry in its deeper foundations : topology. We may therefore begin with its topogical aspects, both in space and in space-time. 1 The question is : Is physical space a " compact » ? Can it be covered by a finite number of "neighbourhoods » ? One of these neighbourhoods would be the 10® light year accessible to astronomi- cal observation. How can we infer that, beyond this observed neighbourhood there are other ones with similar properties and how can we know if these neighbourhoods are in finite number and so form a finite compact or closed space? One possible attitude of mind, in regard to this problem, is to rely on some " Cosmological Principle » which is dogmatically asserted and adhered to. Such principle would déclaré that any observer, at any place in the universe, would hâve essentially the same image of the universe around him. An opposite way of approaching the problem would be to infer the content of the invisible neighbourhoods, which presumably surround our own one, from indirect conséquences of observed facts. Matter is connected with curvature of space-time. Therefore any evidence that matter exists farther than what we directly know, results in producing the geometrical properties of our neighbour hood to larger régions and possibly far enough to close the whole space of finite and not too large radius inferred from the density in our neighbourhood. Some indirect observation of this kind may corne from the cosmic rays or from radio-waves coming from régions inaccessible to our télescopes. As far as I see, the inclination to rely on an a priori principle is related to Leibnitz philosophical attitude which made him to believe that there is some esthetical design in the Universe or even that the Universe is determined as being the best possible one. Of couse, this attitude would not necessary degenerate into mere idealism, with no contact with observation. Conséquences of the principle should be deduced with the hope that they may corne in agreement with observed facts, or, at least, not to be in contradic tion with them. But, nevertheless, as a conséquence of this philosophi cal attitude of mind, the a priori probability would be maintained for the principle. 2 It might be thought that the différence between these two points of view is not, in fact, very great. The one who relies on a cosmo- logical principle would surely allow for local lack of homogenity which will relax the too strong rigidity of the principle. This would refer only to some kind of a " substratum ». Finally his position would not be essentially different from the récognition, by empirical déduction, of a large scale uniformity in the distribution of matter and therefore in the related geometry.

In fact, the différence is very great.

It can be seen in the attitude of some cosmologists who affect to consider on the same footing models with hyperbolic geometry as those with elliptical geometry. It is just a matter of a change of sign in a formula. Now, if we rely on a cosmological principle there are in fact no essential différences in adopting one sign or the other for the para- meter which déterminés hyperbolic or elliptical space. On the contrary, if we rely on inference from observation the déterminant element of judgment is the relative size of the observed sample and that of the whole space which is inferred from it. When space is open, with an infinité volume, the poor 10^ light- years observed are a négligeable trifle and nothing can be inferred from that. On the contrary, for a compact finite elliptic space of a radius somewhat ten times the dimension of the région surveyed, the extrapolation may be found not to be too risky. It is true that locally hyperbolic space is not necessarily open. It is possible to construct with such space polytrops, i.e. Klein's forms of finite volume. This is true even for euclidean space. In fact, gravitational équations relate material properties to the local properties of space. Even for compact homogeneous space, it is well known that it is impossible to décidé, from relativistic considérations, if space is spherical or simply elliptical. A similar situation, more artificial in some aspects, does exists for hyperbolic geometry. It remains that, if space is found to be locally elliptical, and if it can be inferred that material distribution is not too different fartherquotesdbs_dbs46.pdfusesText_46

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