Perpetual motion machine

'Perpetual motion machine' usually refers to a hypothetical machine that either keeps on going forever, or outputs more energy than it consumes. It is considered impossible by the laws of physics as we know it.

Usage in hoaxes It is not uncommon for people to claim to have a perpetual motion machine which one could generate free energy from. Theese people are usually very secretive about their work and needs sponsors while claiming the secrecy is to protect them from dangerous movements afraid of free energy (like big oil companies).

Patent system Since the patent system was put in place it has received a number of patent requests for perpetual motion machines. The US patent office now requires a working prototype in order to grant a patent for a perpetual motion machine.