The search for a perpetual motion machine has been the chupacabra of physics for centuries. Multiple designs have been made, tested and, ultimately, found lacking. Perpetual motion machines are supposed to be able to move, forever, without any energy being used. They sound impossible, because, well, they are. Whether it's an unbalanced wheel, a capillary bowl or some other contraption, there just isn't a machine or device that can move freely, forever, without any energy input.
Why is that? Well, the laws of physics just don't allow for it. Friction will always be part of motion and gravity will always impact any device. Nothing will ever move without energy applied to it. Some point to the classic drinking bird toy, which endlessly dips its beak into a bowl of water. However, the force to make that happen is present in the ambient heat in the air around the bird. A fundamental law of physics is the conservation of energy. Energy cannot just appear, out of nowhere, it must be created somehow. Just like the adage that there is no such thing as a free lunch, there is no such thing as a perpetual motion machine, because energy will always be required to make motion happen and energy is never free.
