So a reaction can be spontaneous, it can have a negative delta G value, but it can take place very, very slowly. And if a reaction takes place very slowly, what that means is it has a very high activation energy. So activation energy is not the same thing as Gibbs free energy. GIBS free energy basically describes the difference between the energy of the reactants and the products. But activation energy describes how quickly a reaction actually takes place. So Gibbs free energy talks about where that equilibrium will be achieved while Activation energy talks about how quickly that equilibrium will actually be achieved.