The gradient flow and the determination of alpha_s
Measuring the intensity of the strong force has his inherent problems due to the non-perturbative nature of the interaction. In this talk I will review one of the lattice approaches to the problem of how to measure the intensity of strongly oupled gauge theories and some of its most recent developments. These include the use of the gradient flow, a tool that allows an easy non-perturbative definition of the coupling constant, but with the potential of having other applications beyond the lattice.