When’s the last time you felt like you were falling and wouldn’t stop? That infinite feeling of motion is another way of thinking about perpetual motion. In essence, the idea is that you never stop moving.
A perpetual motion machine takes this concept and literally runs with it. With a perpetual motion machine, there is no need to ever stop doing work, because it doesn’t actually do work.
Confused yet? Don’t worry – a perpetual motion machine can’t actually exist according to the laws of science. With that said, there is still potential to harness perpetual motion based on discoveries in the universe.
How Does Perpetual Motion Work?
If you want to get technical, perpetual motion doesn’t actually work. That’s because it clearly rejects one or more laws of thermodynamics. The first one tells us about the law of conservation of energy, and the second one can be described in a few different ways.
Mainly, the idea of the second law is that heat will eventually dissipate to colder places. Because of this, given an isolated system, no one person or object can create new energy. Produced work power divided by input heating power, the formula for thermal efficiency, cannot be greater than one.
The output work power of heat engines is always going to be less than input heating power. On top of this, the efficiency of real heat engines is lower than that of a Carnot heat engine. This results from friction and other irreversibility.
Any machine that directly follows the laws of thermodynamics by taking energy from an unconventional energy source could be referred to as a perpetual motion machine. If a machine has a source of energy that isn’t obvious, you could make the argument that it violates a law of thermodynamics.
What Makes a Perpetual Motion Machine Perpetual?
When a perpetual motion machine is classified due to its violation of a thermodynamics law, it gets placed into one of three different categories.
The first kind of machine produces work with no energy input whatsoever. This is a direct violation of the first law of thermodynamics, which clearly requires the law of conservation of energy.
The second kind of machine will spontaneously convert thermal energy into work of the mechanical kind. If you have thermal energy that equals the amount of work being done, it won’t violate the conservation law, but it does create a problem with the second law, which deals with entropy.
A perpetual motion machine’s signature involves only one heat reservoir. This will be spontaneously cooled with no heat transfer or any second reservoir that does any cooling. According to the second law of thermodynamics, this is impossible without any kind of side effect.
Finally, there is a third type of machine. This will eliminate any sort of friction or other force that would prevent continuous, infinite motion. It would be impossible to make this kind of machine, since dissipation cannot be eliminated inside a mechanical system.
Why Is a Perpetual Motion Machine Impossible?
If you’ve ever heard of the concept of epistemic impossibility, then you know that there is a fine line between impossible and possible. Epistemic refers to the idea that something is impossible given a current, established set of laws. With this idea in mind, the proof of a perpetual motion machine relies on the introduction of new laws.
From a mathematical standpoint, the existing laws of thermodynamics provide almost no wiggle room for interpretation. Noether’s theorem tells us that any conservation law can be taken from the same continuous symmetry of an action inside a physical system. Let’s say the true laws of physics never changed over time. This means that conservation of energy would also remain constant.
However, if someone or something were able to prove the invalidity of a conservation law, it would open the door for new interpretations of laws in physics.
Science has dealt with the potential for variance in physics ever since telescopes were invented. The study of other planets helped to establish whether or not existing celestial bodies resembled those in our own solar system.
By using different measurements in spectroscopy and direct measure of light speed in the past, we understand that physics hasn’t changed that much throughout the years. You could make the argument that it’s virtually identical to anything that has been observed in the existence of humanity.
How Does Thermodynamics Affect Impossibility?
Thermodynamics laws are some of the most powerful and solid in all of science. Anyone who introduces the idea of a perpetual motion machine, flying in the face of thermodynamics, will typically be met with complete resistance from the physics community.
The proof ends up being something of a challenge to other scientists. They don’t become interested in how such a machine will work, but how it won’t work.
The best examples of this was the Brownian ratchet being used as a perpetual motion device. The concept was introduced in 1900, and it was decided in 1912 that it would be impossible to use. Those 12 years were spent discovering how the mechanism would fail in its use of perpetual motion.
Future attempts to create any machine capable of perpetual motion have been met with resistance, and in some cases, outright mockery. With such a firmly established set of laws within the world of physics, it’s not hard to see why these devices are scoffed at within the scientific community.
If you need further proof of how impossible the world thinks this concept is, the United States Patent Office specifically states its refusal to give patents, even pending, for perpetual motion machines.
How Would a Perpetual Machine Work?
Some of the proposals for perpetual motion machines date back by centuries. When magnets were first used, they were considered mysterious and the door was wide open for a new world of discoveries. Using a magnet at the top of a ramp, an early idea used the magnet to pull the metal ball upward. Right near the magnet was a small hole meant to allow the ball to disappear and return to the bottom.
The device wouldn’t work. Using this same formula on a bigger scale, the scenario remains the same, using a series of magnets to attempt to pass the ball from one magnet to another. Nothing has changed.
The use of gravity at a distance and drawing energy out of its field has been an inspiration for people wanting to create perpetual machines for some time. In order to draw energy out of a given field, you still need to put energy in, and you will lose energy in the process.
When moving weights attached to a wheel, perpetual motion would require that they fall further from the center of the wheel for half of a rotation, and closer to the center in the other half. This is known as Bhaskara’s wheel or the overbalanced wheel, a concept that meant to illustrate the idea that a wheel could move forever.
The problem comes with the side with weights further from the center. It has fewer weights and the other side, and this brings balance to the torque, preventing any perpetual motion. The same idea has been attempted with pivoted arms, rolling balls, and even hammers. No advancement has been made in the years since Bhaskara first tried it in the 1100s.
Another potential idea behind perpetual motion involves the concept of buoyancy. There have been machines that tried to ignore that pushing volume of air downward requires the same work as the fluid moving upward.
These machines will use two chambers with pistons, and some kind of mechanism that pushes air out of the top and into the bottom. Of course, the squeezing area cannot perform enough work to move the air downward. This would leave out any extra work that could be extracted. Once again, the idea for a perpetual motion device using an existing scientific concept goes nowhere.
The Future of a Perpetual Motion Machine
While nothing is certain in the world of science, it’s difficult to argue with thousands of years of evidence without any contradictions. Each time someone has conjured a device that could potentially harness perpetual motion, existing laws of thermodynamics and other parts of physics shoot it down.
This isn’t to say that a perpetual motion machine is a scientific impossibility, but science itself would have to change for a device to become a reality. Proving science wrong can be, well, difficult. That’s the beauty of the natural world and all of its elements.
For someone to introduce a perpetual motion device that correctly functions, it would take a fundamental reinterpretation of physical laws. It’s not an easy task to undertake, especially when the scientific community is ready to disprove such a case with thousands of years of evidence.
Of course, there was a time when the entire world thought Earth was at the center of the universe, only for one supposedly crazy person to prove everyone wrong.