Conservation of energy isn’t just a good idea: It is the law. In particular, it is the first law of thermodynamics. But, apparently, a lot of people don’t really get that because history is replete with inventions that purport to run forever or produce more energy than they consume. Sometimes these are hoaxes, and sometimes they are frauds. We expect sometimes they are also simple misunderstandings.
This is a companion discussion topic for the original entry at https://hackaday.com/2024/07/01/a-brief-history-of-perpetual-motion/