Do we live in a "Dirac-Milne" universe?

The LCDM standard model, although an excellent parametrization of the present cosmological data, requires two as yet unobserved components, Dark Matter and Dark Energy, for more than 95% of the Universe, and a high level of fine-tuning. Faced to this unsatisfactory situation, we study an unconventional cosmology, the Dirac-Milne universe, a matter-antimatter symmetric cosmology, in which antimatter is supposed to present a negative active gravitational mass. We show that this universe remarkably satisfies the cosmological tests for the age of the Universe, Big-Bang Nucleosynthesis, and Type Ia Supernovae data. Most surprisingly, it also provides the degree scale for the first acoustic peak of the Cosmological Microwave Background. This simple model, without any adjustable parameter or need for Dark Matter or Dark Energy, is a reminder that we should look for simpler and more motivated cosmological models than the present LCDM standard model.