title: Free energy
text: # Free energy
  
  Free energy may refer to:
  
  ## Science
  
  * Free energy perturbation, a method based on statistical mechanics used in computational chemistry
  * Free energy principle, a variational formulation of self-organisation in biological systems, applied in particular to neuroscience
  * Free-energy relationship, a relationship in physical organic chemistry
  * Principle of minimum energy, a thermodynamic formulation based on the second law
  * Thermodynamic free energy, the energy in a physical system that can be converted to do work, including:
     * Gibbs free energy
     * Landau free energy (also known as grand potential)
     * Helmholtz free energy
  * Variational free energy, a construct from information theory that is used in variational Bayesian methods
  
  ## Pseudoscience
  
  * Free energy device, a hypothetical perpetual motion device that is supposedly capable of drawing energy from a hidden free energy field, which is unknown in science
  * Free energy suppression conspiracy theory, in which advanced energy technologies are suppressed by governments or special interest groups
  * History of perpetual motion machines, history of devices supposedly capable of drawing unlimited energy
  
  ## Other uses
  
  * In economics, energy from sources that do not require an input which has to be paid for (usually a sub-set of renewable energy)
  * Free Energy (band), a 5-piece rock band on DFA Records
  