Résumé. — Quelques remarques non scientifiques mais importantes. Notion de brisure spontanée

de symétrie ; premier exemple reconnu (Jacobi 1834) et ses relations actuelles avec l'astronomie.

On donne deux critères servant à déterminer sur quels sous-groupes du groupe de symétrie peut se

briser spontanément une symétrie ; illustration dans les cristaux liquides et les particules élémentaires.

Pour ces derniers, après un survol des nombreuses découvertes des années récentes la théorie

de GUrsey est brièvement exposée.

Abstract. — After some non-scientific non-irrelevant remarks, the concept of broken symmetry is explained and illustrated by the first historical example (Jacobi ellipsoid 1834) still useful in astronomy. Two criteria are given for finding on which subgroups of the symmetry group a symmetry can be broken ; examples in liquid crystals and elementary particles. A brief survey of the recent progress in the latter domain and of the Gilrsey theory.]]>

I have also made a couter-experiment to verify this theory. In Tokyo I found an equal probability for cars to be driven on the left side or the right side of the streets and I did observe that identical texts were placed symmetrically on buses and trucks : the first character is near the front part on both sides so the same text must be read from left to right on one side and from right to left on the other side.

Since I have never been yet in a car undergoing a spontaneous CP transformation, I will be able to give you today my report on CP, T and CPT invariance.]]>