Why don't perpetual motion machines ever work? - Netta Schramm

TED-Ed
5 Jun 201705:31
EducationalLearning
32 Likes 10 Comments

TLDRThe video script explores the concept of perpetual motion machines, devices that could operate indefinitely without an external energy source. It begins with Bhaskara the Learned's 1159 A.D. design of a wheel with mercury reservoirs, which was one of the earliest attempts at such a machine. The script explains why these machines are impossible due to the laws of thermodynamics, particularly the first law which states that energy cannot be created or destroyed, and the second law which details the spread of energy through friction. Despite numerous inventive attempts, including variations on Bhaskara's wheel, Robert Boyle's self-watering pot, and magnetic ramp systems, all have failed to overcome these fundamental physical limitations. The video acknowledges the ongoing search for perpetual motion, suggesting that while our current understanding of physics precludes its existence, the future may hold new discoveries that challenge our understanding of energy and matter.

Takeaways
  • 📚 Around 1159 A.D., Bhaskara the Learned conceptualized a perpetual motion machine with a wheel and mercury reservoirs.
  • 🌀 The idea was based on the principle that the mercury's flow to the bottom of the reservoirs would create an imbalance, keeping the wheel in perpetual motion.
  • 🛠️ Perpetual motion machines are devices designed to do work indefinitely without an external energy source, captivating inventors' imaginations for centuries.
  • 💡 The concept of a perpetual motion machine could revolutionize our energy use, such as sustaining life indefinitely if integrated with human systems.
  • 🚫 However, perpetual motion machines are impossible as they violate the fundamental laws of thermodynamics.
  • 🔄 The first law of thermodynamics states that energy cannot be created or destroyed, which means no machine can produce more energy than it consumes.
  • 🤔 Inventors have proposed various designs for perpetual motion, including variations on Bhaskara's wheel with different weights and mechanisms.
  • 🔧 Robert Boyle's self-watering pot idea in the 17th century was based on capillary action, but it too was flawed due to the same energy conservation principle.
  • 🧲 Magnetic perpetual motion machines also fail because the magnetic force would prevent the cycle from continuing, holding the moving parts in place.
  • 🔥 Even if a machine could overcome the first law, the second law of thermodynamics, which involves energy dispersion through friction, would still cause it to stop.
  • 🔍 Despite the impossibility proven by thermodynamics, the search for perpetual motion continues, driven by the potential for new discoveries in the universe and quantum physics.
Q & A

  • Who was Bhaskara the Learned and what did he design around 1159 A.D.?

    -Bhaskara the Learned was a mathematician who, around 1159 A.D., sketched a design for a wheel containing curved reservoirs of mercury. He theorized that the wheel would perpetually spin due to the mercury flowing to the bottom of each reservoir, creating an imbalance that would keep the wheel turning.

  • What is a perpetual motion machine and why are they captivating to inventors?

    -A perpetual motion machine is a hypothetical device that can do work indefinitely without any external energy source. They are captivating to inventors because they could transform our relationship with energy, potentially sustaining life or providing endless power without the need for external energy inputs.

  • What is the fundamental issue with the concept of perpetual motion machines?

    -The fundamental issue with perpetual motion machines is that they violate one or more laws of thermodynamics, which describe the relationship between different forms of energy. These laws make it impossible for such a machine to function as they require more energy output than input, which is not feasible.

  • What does the first law of thermodynamics state and why does it rule out useful perpetual motion machines?

    -The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed. This means you can't get out more energy than you put in, ruling out useful perpetual motion machines because they could only ever produce as much energy as they consumed, with no surplus for other uses.

  • Can you explain why Bhaskara's over-balanced wheel and similar designs do not work?

    -Bhaskara's over-balanced wheel and similar designs do not work because the moving parts that make one side of the wheel heavier also shift its center of mass downward below the axle. With a low center of mass, the wheel would swing back and forth like a pendulum and then stop, failing to achieve perpetual motion.

  • What was Robert Boyle's idea for a self-watering pot in the 17th century?

    -In the 17th century, Robert Boyle theorized a self-watering pot that used capillary action—the attraction between liquids and surfaces that pulls water through thin tubes—to keep the water cycling around the bowl. However, this idea was flawed because if the capillary action was strong enough to draw the water up, it would also prevent it from falling back into the bowl.

  • Why do perpetual motion machines involving magnets not work?

    -Perpetual motion machines involving magnets do not work because the magnet would simply hold the ball at the top, preventing it from falling back down through the hole and repeating the cycle. Even if it did keep moving, the magnet's strength would degrade over time, eventually stopping the machine.

  • What is the second law of thermodynamics and how does it relate to perpetual motion machines?

    -The second law of thermodynamics states that energy tends to spread out through processes like friction. Any real machine would have moving parts or interactions with air or liquid molecules that would generate friction and heat, causing energy to escape as heat. This energy loss would reduce the energy available to move the system, eventually causing the machine to stop.

  • Why have all attempts at creating perpetual motion machines failed?

    -All attempts at creating perpetual motion machines have failed because they either violate the first law of thermodynamics by trying to produce more energy than they consume, or they are subject to the second law, which causes energy loss through friction and heat, inevitably leading to the machine's stoppage.

  • Is it possible that we might discover a perpetual motion machine in the future?

    -While it's hard to conclusively say we'll never discover a perpetual motion machine, current understanding of the laws of thermodynamics suggests it is highly unlikely. However, the possibility of new exotic forms of matter or quantum phenomena could potentially challenge our current understanding and open new avenues for exploration.

  • What can be said about humanity's ongoing pursuit of perpetual motion?

    -It can be reasonably sure that humanity's pursuit of perpetual motion will continue, driven by curiosity and the quest for new forms of energy. While the laws of thermodynamics currently stifle the realization of such machines, the search itself represents a perpetual quest for knowledge and innovation.

Outlines
00:00
🔄 Perpetual Motion Machine: An Enduring Myth

In 1159 A.D., Bhaskara the Learned conceptualized a perpetual motion machine involving a wheel with mercury-filled reservoirs, theorizing that the imbalance created would keep the wheel in perpetual motion. This idea represents one of the earliest designs for a machine that could perform work indefinitely without external energy, a concept that has fascinated inventors due to its potential to revolutionize energy use. However, such machines violate the fundamental laws of thermodynamics. The first law states that energy cannot be created or destroyed, implying that a machine could only produce as much energy as it consumes, with no surplus for other uses. Despite this, inventors have continued to propose various designs, such as Bhaskara's over-balanced wheel and Robert Boyle's self-watering pot, all of which fail due to the laws of physics. The second law of thermodynamics, which dictates that energy spreads out through processes like friction, further ensures that no machine can operate perpetually without external energy input. While the search for perpetual motion continues, it remains an elusive goal constrained by our current understanding of physics.

Mindmap
Keywords
💡Bhaskara the Learned
Bhaskara the Learned was a mathematician from around 1159 A.D. who is mentioned in the script for his early design of a perpetual motion machine. His concept involved a wheel with curved reservoirs of mercury, which he believed would create an imbalance that would keep the wheel turning indefinitely. This example illustrates the historical fascination with the idea of perpetual motion and serves as a starting point for the video's exploration of the concept.
💡Perpetual Motion Machine
A perpetual motion machine is a theoretical device that can do work indefinitely without an external energy source. The concept is central to the video's theme as it discusses various attempts throughout history to create such a machine. The script uses the metaphor of a windmill that produces its own breeze or a lightbulb that powers itself with its glow to explain the allure and the impracticality of perpetual motion machines.
💡Thermodynamics
Thermodynamics is the branch of physics that describes the relationships between different forms of energy. The script highlights how the fundamental laws of thermodynamics contradict the possibility of perpetual motion machines. It is essential to understanding why these machines cannot work, as they would violate the principles that govern energy transformation and conservation.
💡First Law of Thermodynamics
The first law of thermodynamics, also known as the law of conservation of energy, states that energy cannot be created or destroyed, only converted from one form to another. In the context of the video, it is mentioned to explain why a perpetual motion machine cannot produce more energy than it consumes, thus making it impossible to create a useful perpetual motion machine.
💡Center of Mass
The center of mass is the point where the total weight of an object appears to act. The script discusses how the moving parts of a proposed perpetual motion machine, such as Bhaskara's wheel, would shift its center of mass downward, causing the wheel to behave like a pendulum and eventually stop. This concept is crucial for understanding why certain designs for perpetual motion fail.
💡Capillary Action
Capillary action refers to the attraction between a liquid and a surface, which can pull the liquid through narrow spaces against gravity. The script mentions Robert Boyle's 17th-century idea of a self-watering pot that relied on capillary action. However, the video explains that if capillary action were strong enough to draw water up, it would also prevent the water from falling back, illustrating the impracticality of this approach.
💡Magnet
Magnetism is the force of attraction or repulsion that arises between materials, which can be used to propose designs for perpetual motion machines, as mentioned in the script. One such design involves a set of ramps with a magnet pulling a ball upwards, which is supposed to fall back down and repeat the cycle. However, the video explains that the magnet would simply hold the ball at the top, and even if it did move, the magnet's strength would degrade over time, violating the first law of thermodynamics.
💡Friction
Friction is the resistance that one surface or object encounters when moving over another. The script uses friction as an example of a process that spreads out energy, such as through heat generation, which would inevitably stop a perpetual motion machine. It highlights how even in a vacuum, friction and heat would cause energy to escape, reducing the energy available to keep the machine moving.
💡Second Law of Thermodynamics
The second law of thermodynamics states that energy tends to disperse and that systems tend to progress from order to disorder. In the script, this law is discussed to explain why perpetual motion machines are impossible in the real world. It emphasizes that any real machine would generate friction and heat, causing energy to escape and the machine to eventually stop.
💡Quantum Scales
Quantum scales refer to the extremely small dimensions at which quantum mechanics governs the behavior of particles. The script speculates that there might be perpetual motion on tiny quantum scales, suggesting that our current understanding of physics might be incomplete and that new discoveries could potentially challenge our understanding of thermodynamics.
💡Search for Knowledge
The search for knowledge is a recurring theme in the script, which emphasizes the human desire to explore and understand the universe. It suggests that while we may not have found a perpetual motion machine yet, our quest for knowledge and understanding will continue. This theme is encapsulated in the statement that 'the one thing that seems truly perpetual is our search', highlighting the undying human spirit of inquiry.
Highlights

Around 1159 A.D., Bhaskara the Learned designed a perpetual motion machine with a wheel containing curved reservoirs of mercury.

Bhaskara's design aimed to create a perpetually spinning wheel by exploiting the imbalance caused by the flow of mercury to the bottom of each reservoir.

Perpetual motion machines are devices that can do work indefinitely without any external energy source.

The concept of perpetual motion machines has the potential to transform our relationship with energy.

Perpetual motion machines cannot work as they violate the fundamental laws of thermodynamics.

The first law of thermodynamics states that energy cannot be created or destroyed, which contradicts the idea of a perpetual motion machine.

Inventors have proposed various designs for perpetual motion machines, including variations on Bhaskara's over-balanced wheel.

Robert Boyle's self-watering pot idea in the 17th century utilized the concept of capillary action.

Capillary action, while capable of drawing water upwards, would also prevent it from falling back, making the self-watering pot impractical.

Magnetic perpetual motion machines, such as a set of ramps with a magnet, also fail due to the magnetic force holding the ball at the top.

Any perpetual motion machine would require extra energy to overcome its stopping point, violating the first law of thermodynamics.

Machines that appear to keep moving are actually drawing energy from an external source.

The second law of thermodynamics states that energy tends to spread out through processes like friction.

Friction and heat generation in any real machine would cause energy to escape, eventually leading to the machine's stoppage.

Despite the impossibility proven by thermodynamics, the search for perpetual motion machines continues due to our limited understanding of the universe.

The possibility of discovering new forms of matter or quantum scale perpetual motion remains open, though unlikely.

The perpetual search for a perpetual motion machine reflects human curiosity and the pursuit of perfectly efficient energy generation.

Transcripts

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Perpetual MotionThermodynamicsBhaskaraEnergy EfficiencyInvention HistoryScience MythsMechanical FailureRobert BoyleCapillary ActionMagnetismQuantum MechanicsInnovation Quest