In physics, free energy is a mathematical function that quantifies the work performed by a closed thermodynamic system during a reversible transformation at constant temperature. That is, in any case, the definition that you can find in a textbook of physics. On the web, though, the term free energy refers most often to a new source of energy that is largely ignored by the scientific community but on which the future of humanity depends in the current context of energy and environmental crisis. Is it reality or Internet myth?
Based on what the Internet says, it would seem that this free energy abounds around us and that “the evidence of this free energy source is demonstrated by tens or even hundreds of people” (Wikistrike 2015). It would be available for free and occupy the “vacuum” that surrounds us. To implement it, no one needs to be an engineer or physicist, as you just have to apply what is described in one of the available books dealing with how to design a machine that will “transform something that we do not know how to detect into something usable” (Newman 2011). But as Aristotle stated, “the definition makes known what is the thing.” So, what is that thing?