Since we found out about energy, right up until the point we found out it violated the laws of physics, people have dreamed of creating a perpetual motion machine. Perpetual motion machines are devices that, once started, could theoretically remain in motion forever without adding any additional energy to them. 

Many people have strived to create such a machine, all with zero success. Early designs for such a device include the Perpetuum Mobile of Villard de Honnecourt. This device, proposed between 1225 and 1235, was supposed to sustain the motion of a wheel by attaching weights to it 

"For a long time the masters have been discussing how to make the wheel turn on its own," Villard wrote. "Here’s how the thing can be done by a fixed number of mallets or with quicksilver."

The problem was, of course, that the amount of force required to lift the mallets to the top of the arc is more than the wheel gains from those mallets dropping down on the other side. This video demonstrates how it works in practice.

As you can see, rather than delivering free energy forever, it just sort of stops immediately without additional energy (a big push) being put into the system.

Such machines were dismissed instinctively as absurd long before Newton's pesky laws ruled them out.

"Oh, ye seekers after perpetual motion, how many vain chimeras have you pursued?" Leonardo da Vinci supposedly said of those attempting to make such devices. "Go and take your place with the alchemists".

Da Vinci could be accused of playing both sides, as his notebook contained designs for several different perpetual motion machines (though it's unlikely he thought they would work), including a slightly different version of a spinning wheel with weights. It works pretty well, albeit with the constant energy input of a finger.

Perpetual motion machines do not work because they would violate the first and second laws of thermodynamics. The first law – that energy cannot be created or destroyed, only changed in form – means that you cannot get out more energy than you put in, rendering this pursuit useless to anyone hoping to use a perpetual motion machine to generate energy.

If you wanted a device to spin by itself forever, you are also out of luck courtesy of that second law, which states that the entropy of an isolated system increases over time, and that heat always flows "downhill" from hotter to colder regions. In practical terms, it tells us that as energy is transferred and transformed, some of that energy is spread out and "wasted", e.g. through heat loss via friction. As the machine goes around, the system will lose energy as heat and through friction, making even the most well-designed "perpetual motion machine" stop eventually, if not immediately as above.

That doesn't mean that people haven't pretended to have invented machines through the years, with the result that patent offices do not accept claims of perpetual motion machines anymore. 

One fun example of a "perpetual motion machine" housed in the Royal Society was created by scientist David Jones under the pseudonym "Daedalus".

The wheel has moved around for decades, though it does require undisclosed adjustments now and then. The machine, made for fun by Jones, of course does violate the laws of physics. Some hidden mechanism, likely concealed within the black boxes on the wheel's spokes or the pipes and boxes beneath it, must provide additional energy to keep the wheel moving. However, the real method is kept secret, and won't be revealed for three decades.

"Many have tried to discern the disguised workings of Daedalus’s perpetual motion machines," Virginia Mills of the Royal Society, which houses the device, wrote of it in 2018. "But I’ve heard that only one person ever suggested the right answer to its creator."

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.