As far as theory and practice are concerned, physics at the beginning of our 21st century is very much to be admired. However, mathematically speaking, when theory is pursued to its ultimate consequences, divergences show up relative to computation. As regards phenomena, theory is unable to respond in an unequivocal way to all of the questions raised by progress in observation of the Cosmos. Therefore, one tries to pursue simultaneously observation, experimentation, and conceiving new mathematical theories.