Is it possible to build a perpetual motion machine?
Theories have four stages of acceptance:
(i) This is worthless nonsense
(ii) This is interesting but perverse
(iii) This is true but quite unimportant
(iv) I always said so.
- J.B.S. Haldane
Perpetual - never ending or changing.
Motion - the action or process of moving or being moved.
Machine - a mechanically, electrically, or electronically operated device for performing a task
Perpetual Motion Machine (PMM) is a device that, once set in motion, would continue in motion forever, with no additional energy required to maintain it.
In the coming years, when industries would gradually exhaust energy resources we will have to look for alternatives: an abundant, cheap yet efficient new source of energy. Is an infinite energy source truly impossible, or do we need to revise our understanding of the laws of physics?
History
The earliest claim to achieve perpetual motion dates back to the eighth century in Bavaria. Known as the “Magic Wheel”, the machine consisted of a spinning wheel that was powered by small magnets. Beneath the wheel was a much bigger magnet which attracted and then repelled the small magnets as they passed over it. This created a perpetual motion. However, it was not possible to overcome the frictional forces and hence the machine would not run forever.
In 1150, Indian philosopher Bhaskara claimed to have built a PMM. It was based on the principle that weights that are not equidistant from a wheel’s axis of rotation, in effect would take advantage of the imbalance of torque and keep the wheel running forever. Again, since the axis is not frictionless, the motion would eventually cease.
In 1635 the first patent was granted for a PMM in the UK. By 1712, Johann Bessler had experimented with about 300 different perpetual motion models before claiming to have developed his own working models. Leonardo da Vinci also became interested in PMMs.
Hoaxes And Frauds
PMMs might be a distant, blurry dream of scientists but they have been widely used by scam artists in history. Here I name some of the most famous attempts to build PMMs which upon investigation were discovered as mere hoaxes. You can uncover these stories at the given links.
1760s - James Cox: Mr. Cox’s Perpetual Motion • A Mechanical and Philosophical Time Piece • So Capital a Performance
1812 - Charles Redheffer: The Perpetual Motion Machine: Did Charles Redheffer Defy Physics?
1872 - John Ernst Worrell Keely: A Successful Story of Faking It Until You Make it: John Keely and the Keely Motor
1881 - John Gamgee: How John Gamgee’s perpetual motion machine fooled a president
Three laws Of Thermodynamics
Thermodynamics is a branch of physics that deals with heat, work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation.
PMMs are based on the three laws of thermodynamics (there is also a Zeroth law of thermodynamics but is irrelevant to this topic):
First Law - The total amount of matter and energy cannot be created or destroyed.
Second Law - The total amount of entropy (disorder) always increases. Heat flows spontaneously only from hotter to colder places.
Third Law - Theoretically, the lowest possible temperature is absolute zero (0 K) which can never be reached in practice.
Classification
Depending upon which law of thermodynamics is violated, PMMs are classified into three kinds:
First Kind
They violate the law of conservation of energy (first law): they produce more energy than they consume. All such PMMs rely on hidden, external sources of energy.
Robert Fludd’s closed-cycle water mill is an example of PMM of the first kind. Source Second Kind
They violate the Second Law of Thermodynamics: exhibit 100 % efficiency. But achieving absolute conversion of heat into work is impossible, some waste heat is always produced, which raises the entropy of the universe.
John Gamgee’s zeromotor is an example of PMM of the second kind. Source Third Kind
They have completely eliminated all forms of dissipation due to which they continue in motion forever. They can be approximated but not entirely achievable because some energy is always dissipated in some form like friction.
Symmetries
Are laws of thermodynamics so intricately woven into the framework of the universe that it is impossible to break them? Can we find loopholes in the laws?
In 1918, German mathematician Emmy Noether discovered one of the fundamental principles of physics:
Noether’s First Theorem states that whenever a system possesses symmetry, there exists a corresponding conservation law.
The laws of the universe possess spatial and temporal symmetries i.e. they are the same in all directions and have never changed over time. The result is that energy is conserved. Could this symmetry be broken in rare, unusual circumstances? We are yet to grasp what happens inside black holes and wormholes. So maybe these are the locations where the known laws of thermodynamics could break.
According to Michio Kaku, the conservation of energy arises from deep, cosmological reasons. Any violation of these laws would necessarily mean a profound shift in our understanding of the evolution of the universe.
He classifies PMMs as a Class III impossibility; that is, either they are truly impossible, or we would need to fundamentally change our understanding of fundamental physics on a cosmological scale in order to make such a machine possible.
Sources:
Ch 14 - Perpetual Motion Machines, Physics of the Impossible, Michio Kaku
Perpetual Motion - David Darling
Debunking Perpetual Motion - Joshua Yoon, Stanford
History of perpetual motion machines - Wikipedia
Thermodynamics - Wikipedia
