  An attempt is made here to extend to the microscopic domain the scale
invariant character of gravitation - which amounts to consider expansion as
applying to any physical scale. Surprisingly, this hypothesis does not prevent
the redshift from being obtained. It leads to strong restrictions concerning
the choice between the presently available cosmological models and to new
considerations about the notion of time. Moreover, there is no horizon problem
and resorting to inflation is not necessary.
