Since always. All known processes try to achieve stable state of minimal energy by either competition (in biology and economics in specific) or by adjusting the rate of change in the system to fade with time (thermodynamics, chemistry) by means of equal distribution. It can oscillate around equilibrium, but as long as it does that it tries to achieve the state of diminishing change via dissipation (losing energy externally) and/or negligible local<->global direction of change (dynamical system at stable minimal energy). You can read more about types of equilibria or read-up on Lagrangian and Hamiltonian mechanics. They will be invaluable to pursue the amazing world of statistical mechanics that opens the door to both quantum many-body physics and cosmology and almost every subdivision of physics in-between. I do recommend Road to Reality by Roger Penrose to get a general gist of all that and more. am_Unition - would you mind doing a bit of a fact-check for me here? Sorry for bothering you, yet again.since when does the universe operate in equals and balance?