In The Matrix the machines "grow" humans to provide a source of power. Is this really feasible from the perspective of power generation (never mind all the business of growing/feeding people)? Wouldn't the machines just use nuclear power?
Edit: For what it's worth, in the movie Morpheus explains that the human power is "combined with a form of fusion."
Yeah, this isn't feasible. Humans produce heat and radiate heat, but not so much that you could really harness it for power. It wouldn't be at all efficient given the necessary inputs of food and water. The nuclear power would be far more practical.
So, no, the machines wouldn't use humans for power. It makes no sense.
For those who require more explanation: humans produce their energy from food, primarily glucose. However, the majority of that energy produced does not go to releasing heat. The heat is an afterthought, part of maintaining homeostasis to allow for the most efficient biological reactions. Most of the energy goes into powering our cells so that they reproduce, make proteins, power our brain, etc.
Attempting power generation by harvesting human heat is ridiculously inefficient. You'd be infinitely better off just burning the glucose.
And this isn't taking into account all the other foods and nutrients we need to stay healthy that have nothing to do with us generating heat.
By Eliezer Yudkowsky, author of Harry Potter and the Methods of Rationality
MORPHEUS: For the longest time, I wouldn't believe it. But then I saw the fields with my own eyes, watched them liquefy the dead so they could be fed intravenously to the living -
NEO (politely): Excuse me, please.
MORPHEUS: Yes, Neo?
NEO: I've kept quiet for as long as I could, but I feel a certain need to speak up at this point. The human body is the most inefficient source of energy you could possibly imagine. The efficiency of a power plant at converting thermal energy into electricity decreases as you run the turbines at lower temperatures. If you had any sort of food humans could eat, it would be more efficient to burn it in a furnace than feed it to humans. And now you're telling me that their food is the bodies of the dead, fed to the living? Haven't you ever heard of the laws of thermodynamics?
MORPHEUS: Where did you hear about the laws of thermodynamics, Neo?
NEO: Anyone who's made it past one science class in high school ought to know about the laws of thermodynamics!
MORPHEUS: Where did you go to high school, Neo?
(Pause.)
NEO: ...in the Matrix.
MORPHEUS: The machines tell elegant lies.
(Pause.)
NEO (in a small voice): Could I please have a real physics textbook?
MORPHEUS: There is no such thing, Neo. The universe doesn't run on math.
No, the laws of thermodynamics (specifically, that entropy in a closed system will always increase) state quite clearly that if you have a food source capable of feeding a human body, it will produce more power to use that food source as fuel than to pass it through a human body.
The human body spends significant amounts of energy maintaining its own body temperature, powering organs, pumping blood, and thinking. All the electrical activity in the brains and neurons isn't free, and it takes energy to process air into a fuel source.
Literally everything the human body does is an energy sink, and the waste energy we give off that the machines are purported to use (body heat, I believe) is a miniscule fraction of what we require to function. Even if you could reclaim only 50% of the calories in a food source by burning them in a furnace, it would be a vastly superior compared to 'feed it to people and eat their body heat'.
This was a big issue with The Matrix, but in light of The Animatrix, I have an alternate theory: The machines don't really want to eliminate humans, just to be safe from them. This is consistent with their creation of the machine nation (which humanity destroyed) and their actions in the movies.
They want humans to exist, but they want to exist as well. Since it's been demonstrated that coexistence fails, they logically decided that imprisoning humanity was the most efficient way to allow the humans to live without threatening the machines.
My guess would be that the immense power generation setup was part of a double-blind: they knew some humans would be free of the matrix (as the architect explains) but they needed some visible reason to keep humans around (reasonable enough that the humans would not search for other reasons). So they likely try to use the human batteries as the primary power source for the matrix (supplementing it with their standard power sources, as it would be insufficient by itself).
In short, the machines did it in part to reduce the cost of keeping humans alive, and to prevent the inevitable freed humans from railing against the machine's primary civilization and culture.
It is surely pointless. Much more energy could be harvested by simply burning the nutrients that are fed to the humans - actually even more energy could be harvested by not producing the nutrients and using the energy saved elsewhere.
In fact, humans only radiate heat as a byproduct - because they keep their temperature constant - and so they are really inefficient heat engines.
Also, in the movie, humans are kept alive in a soup. Now, what is the temperature of that soup? Does it need to be heated in order to keep the humans alive? Well, the energy cost of keeping the soup warm is actually way more than you could extract from the humans!
There already are several devices that can derive power from external sources. (Energy Harvesting methods) The ones that could possibly be used to extract energy from humans held in pods are mainly :
Thermoelectrics : Which are currently able output about 40µW.
Bio Fuel Cells : Capable of producing 100µW.
These technologies still have a lot of room for improvement, but for arguments sake let's assume 50µW and 100µW respectively.
Let's say the outfit each individual with 10 of these Energy Harvesters.
Resulting in 1500µW per person.
Assuming there are 5 billion people being kept at all times. [4]
This would result in a power output of 7.5 Mega Watts, while not nearly enough this is just using today's technology which presumably will be a lot more developed in the future.
So even though there are definitely more efficient ways of producing energy, it might be feasible if the technology is sufficiently mature.
EDIT:
An average person needs about 2000 Calories a day (Food Energy), which translates to roughly 100 Watt.
As much as I enjoyed The Matrix, this was the most silly premise of the movie. As stated before, I could understand using humans as an organic computation source, but there's just not that much energy outputted from a human body, especially when there's much better sources that we see in the film... lightning, winds, and even their drilling tech could have been used for geothermal energy.
A few alternatives they could have used that would make sense:
Raise a tower to space for a) solar power, b) harness sky voltage, c)harness energy from lighting discharge, d) harness energy from layer of electrostatic interference surrounding the earth
Dig down to the core for geothermal energy
The Second law of thermodynamics states any system will run to entropy over time, i.e unless there is some new input of heat or information at a very fundamental level to sustain the system and restore order. For the matrix films, the assumption is made that the human are acting as a power source, where the output is greater than the input. That breaks the second law. Also the assumption is made (implicitly I think, It's not really discussed at any length) that humans are essentially a derivation of a know fallacy, namely perpetual motion machines. These have never proven to exist, or can exist, because they would break the second law.
But hey, it's a cool film. Enjoy. And today, Keanu Reeves announced 4 and 5 are in development.
It is not reasonable. Neither is sending people back in time to kill them. Dreaming inside a dream making your brain run 10x faster for each level is also not reasonable. I think the 'reason' part is that the story writer hoped it would freak movie goers out to think of the human race as a power supply for machines. It's along the same lines as zombies needing to eat brains. Freak-out factor +100, real-world physics -100.
Humans could not possibly be a viable fuel source. The sugar, proteins, and lipids that would be required to raise a human to adulthood like in the movie would need to come originally from plants. Plants use light energy from the sun to produce sugar through photosynthesis. The idea that the machines would convert heat and electricity from fusion into light to produce sugar to feed humans to harness heat and electricity is absurd.
The idea of using the human brains as nodes in a giant matrix is interesting. I believe there is more than enough processing power there to support the virtual reality and expand on the machines processing power. Even more interesting to me is the parallel between this story and Isaac Asimov's rules of robotics. Perhaps the machines never eliminated the humans because they can't. Perhaps they believe they are in fact doing the humans a favor. Keeping us safe from ourselves.
As a scientist, I am deeply bothered by the notion of an entire movie being based on such an absurd premise. We must all remember, however, that if the future machine overlords do in fact eradicate human kind (as they certainly would) then movies like the matrix and terminator don't get made in the first place. These movies are compelling but why? Because at the heart of them is the notion that faced with an overwhelming common enemy we would stop fighting ourselves and work together.
I have read a theory that machines are using "unused part of human brain" to control nuclear fusion -- the second part seems reasonable, but first of all, there is no such thing as "unused part of the brain" and probably the computational power required to run matrix itself is way higher than this needed to control fusion.
The other option is that machines are using human intuition or clairvoyance skills, but this is also a fantasy.
Morpheus makes it clear that it's not just the BTUs and electricity produced by the human occupants but also a novel form of fusion that produces the power that the machines need.
Combined with a form of fusion, the machines have found all the energy they would ever need.
There's actually a little more info about this in an earlier version of the script, dated 1996.
MORPHEUS: They discovered a new form of fusion. All that was required to initiate the reaction was a small electric charge. Throughout human history we have been dependent on machines to survive. Fate, it seems, is not without a sense of irony.
[We return to the power plant that Neo escaped from where we see human beings looking almost blissful in their gelatin cocoons.]
MORPHEUS: The human body generates more bio-electricity than a 120-volt battery and over 25,000 B.T.U.'s of body heat.
[Outside, spreading all around the power plant, beneath a breathing greenhouse, are the growing fields.]
MORPHEUS: We are, as an energy source, easily renewable and completely recyclable, the dead liquified and fed intravenously to the living.
The short story "Goliath" included on the Matrix website and in the Matrix Comics (Volume 1) indicates that in addition to using humans as batteries, they're also being using people's brains as secondary computer processors and memory storage.
""What's going on?" I asked. "Do you know?"
"Enemy missile took out a central processing unit," he [the Agent] said. "Two hundred thousand people, hooked up in parallel, blown to dead meat ... You're just free-floating here for a couple of nanoseconds, while we get London processing again."
A full text can be found here.
It seems far-fetched that human body heat would be worth the machines' time in comparison to other sources of energy. Nuclear is the obvious choice, but geothermal might work as well. Wind might be a good choice considering the surface is in a state of perpetual storm. You could even put solar panels on balloons to get above the clouds. All of these are far more practical than feeding humans and capturing their waste heat.
However, it's not completely impossible for the human pod setup to be a net energy gain for the machines. Consider that Morpheus is certainly wrong about his dates in the first movie. The Architect tells Neo about 6 full cycles of Zion growing from a handful of people to a teeming city, but Morpheus thinks that the war only happened a hundred years ago. Human civilization might be much older than Morpheus believes. Maybe at humanity's collapse, the Earth had a population of trillions. That's a lot of bodies lying around. Yes it would be smarter to burn them as fuel, but they could be used to keep a smaller population of humans alive for a very long time. It might occur to a machine that, since they're keeping people alive anyway, they might as well capture the waste heat and use it.
Why keep that population of humans alive though? Maybe the machines in charge have something like the First Law of Robotics, and they're incapable of completely wiping out the human race.
Many people in the comments have also pointed out that there's little reason to believe that humans are kept for their waste heat anyway. Morpheus thinks it's true, but he's not right about much of anything, is he? We might be used for our processing power instead. Or, if the Architect is lying about him needing humanity, humanity might just be pets, or somehow convenient to a player in AI politics.
As, it is clear from @M.K.'s answer, power generation is not possible from human body. However, I think there are other questions raised by your question that need to be addressed:
Why would machines leave humans alive? is there any other reason apart from being a power source why humans would be left alive by machines?
Ans. The machines are not so Idiotic as to ignore creatures as ours selves that have the capabilities of learning, sensing and creating, just by killing them. They would certainly invest a lot of their resources in understanding us and how we function. They might be looking for processing power too from human brains as suggested by @RoguePlanetoid in his comment. No matter how you look at it, Human race would be much more valuable to the machines alive, than dead.
It would be for a short time, if the machines did their work efficiently enough.
They'd have to have minimal (negligible) costs for Liquifying, Growing, Transporting, Simulating the Matrix for human beings.
The machines are perfect computers, so maybe they could do that. Then you'd be left with a very rapidly declining population, as energy is wasted in humans by radiating heat, moving (and thinking) and the inefficiency of digestion.
As the machines are perfect computers, yes they might have found they could extract energy this way for a couple of years. Someone do the math to find out how long precisely.
The machines would somehow have to have a reason for not being more efficient about all this biomatter, as surely the overhead is not better than having a customized biomachine do the processing.
I base this answer on nothing more than the thoughts I had while I watched The Matrix for the very first time.
As many previous answers mentioned, the idea of the human body providing machine energy is ludicrous (you can get a rough feel for the efficiency of an energy source by how hot it gets - aka thermal efficiency). I always assumed this was the machines spreading disinformation and that we'd eventually discover that the answer was a lie.
But consider that in The Matrix movie we observe that at some point humans did create AI. Suppose that AI wished to reproduce and discovered it did not know the secrets that humans used to create the AIs.
Why then it might make sense for that AI to plug humans (who did eventually solve the problem) into an environment that simulates the environment in which they originally solved that particular problem. Since this time the machines are watching, then they will discover how humans solve the problem of creating new AIs when they create a new one in the matrix.
My solution provides a very neat and scientifically interesting plot twist to the original The Matrix movie but it blows the sequels out of the water :(
but I never liked those anyway...
Alright we know it's less efficient than other sources but in the machine world the sky has been blocked out so natural food sources don't exist and you need energy to produce more. When the uprising began, it was a way to control and use the humans at the same time en masse since there were probably 10 million or more in this future and the life span of the human in this condition provides a stable source of power. I'm sure a machine by logic would choose to put them to use for what little power they could, rather than to just kill. How do we know they did not have other resources at hand?
Morpheus declares that a "human body generates more bio-electricity than a 120 Volt battery and over 25,000 BTUs of body heat". This is a nonsensical statement as voltage is a measure of electrical potential, not power; voltage, by itself, says nothing about the actual capacity to do work. As for the heat claim, there are tables which show that a person produces somewhere between 340 and 1400 BTU/hr, depending on level of activity. The number used by Morpheus might be a nominal value for a day, but as a "fact", it is inaccurate and/or incomplete.
To be confirmed, but apparently the original concept was use of humans as components of a biological computer - some sort of hive mind. Likely, the concept got dumbed down by either a studio exec or an uninformed writer, and mixed up with the true fact that an average adult human at rest produces about 100 Watts of heat (true fact used in air conditioning load calculations). In North America, incandescent light bulbs for household use have been commonly available in 120V 100W ratings, inviting comparison, but it probably sounded better in scripting to draw a comparison to a battery (energy source) than a light bulb (energy consumer). One might imagine a chain of logically flawed and/or misunderstood connections leading from true fact to an absurd line of dialog.
Apart from the impracticality of harvesting heat from people as an energy source (why not use cattle instead? - they have less propensity to rebel), there is the question of what you feed these people (or cattle) on when the solar energy needed to grow crops has been blocked ("scorched the sky"). Morpheus' exposition is really rather absurd on several levels. Best to just go with it and enjoy Neo's journey without asking too many questions.
The other answers are good but do not take into account a certain striking highly legitimate/relevant scientific angle, have long noted the following but never seen anyone else point it out.
Thermodynamics and physics are certainly relevant/useful/compelling concepts to analyze this question (and the robotics in the movie tends to steer thinking/interpretations in this direction), but in some ways is misleading. There is a key concept from biology that is highly relevant:
In other words, in stark specifics, to mix biological and technological metaphors [but exactly as the movie does], a model for the movie is that its a bizarre robotic-human parasite interface, where the human race is the host and the robotic race is the parasite "species". This interface sounds weird but it is also the basis of the theory of "cybernetics" aka termed by one "the marriage of man and machine" (and related to the origins of the word cyberspace).
A relatively new book on this subject by Zimmer, Parasite Rex,[1] documents how there has recently been a real/total Kuhnian paradigm shift (mass/systematized rethinking) in biology on this subject. parasites are now known to alter the behavior of their host in key ways. the parasite extracts energy from its host but not in so much an obvious way but in an indirect way (eg parasite feeding off host blood, which houses stored energy). also up to a staggering 3/5ths of all species on earth have parasitic aspects, that is, it is the basic mechanism (of life/energy extraction) employed by the majority of life on earth.
So far it is not thought that many parasites are "designed/optimized" (evolved) to focus primarily on human hosts [ie we believe we are at the "top of the food chain" as the saying goes], but one certainly wonders! A semi scientifically plausible candidate is as follows! the parasite Toxoplasma gondii is estimated to infect up to ~30% of the entire human population. (and how much does this ~2.5B host count compare to its other hosts, cats and rats?)
It cannot reproduce sexually in the human host but it can reproduce asexuallly in humans! toxoplasma can be transmitted vertically from pregnant mother to child! T. gondii is thought to be mostly dormant in the human, although it is now documented to alter human behavior. it is implicated as a linked factor in schizophrenia. scientists admit that there is much unknown about T.gondii & overall study of it is in many ways still in early stages.
Another striking example/video of a parasite controlling the behavior of a insect host, the fungus parasite in rain forests, and thereby extracting energy almost as if the host is its battery.[2]
Yet another key element that no other answers point out: human slavery has existed for countless millenia, probably as long as humanity has, and slavery persists to this day around the world. The most simple analogy is that the robotic species has enslaved the human race. Slavery is once again an indirect harnessing of energy of one individual by another. Of course there are also strong parallels between parasites and slavery such that parasites are said to enslave their hosts in almost all senses of the word.
Even in western civilization slavery is thought to be banished, but a more subtle but very similar form of wage slavery is extremely widespread and at record levels as revealed through statistics on economic inequality. These are somewhat more abstract analogies, but the economic system is an energy system and slavery is a harnessing/extraction of energy through the economic realm.
[1] Parasite Rex: Inside the bizarre world of nature's most dangerous creatures
[2] Absurd Creature of the Week: The Zombie Ant and the Fungus That Controls Its Mind
Humans weren't originally supposed to be batteries. In the original script, the humans' brains were supposed to be all wired together (kind of like the Borg collective) and the collective thoughts of all the humans acted like the internet, thus creating the Matrix. There was no central or "mainframe" computer running it. This is why too many humans couldn't be unplugged, it would disrupt/destroy the Matrix. The production company felt it would be to confusing for movie goers, and forced the Wachowskis to change it. That's how they came up with the battery concept, which as others have pointed out, wouldn't work. In The Animatrix, it showed that the whole reason behind the creation of the Matrix was a deal that was struck between the human and machine leaders, after humans lost the war. The humans surrendered, and the machines agreed to construct the Matrix so humanity would not be extinct.
Wow, what a lot of answers already! Anyway, no, what we see in the movie flat-out wouldn't work. Our brains don't produce THAT much electricity, and if they were siphoning it off to run stuff, then our brains wouldn't function properly, or at all. IOW, take some of our electricity, and the whole brain stops working.
As a person that loves movies, I know that movies will often get some details wrong either intentionally (artistic license) or accidentally. Some of those details can be very significant. Therefore, for each movie or movie series, I grant the story its own pocket universe with little concern as to how close to reality that universe is. If the movie (or series) is at least internally consistent, then I don't mind if the creator took liberties or made errors. I think that you are making an error in trying to match up a sci-fi/fantasy movie with the laws of physics as we know them.
You might as well be asking if it is reasonable for the time machine in Back to the Future to be capable of compensating for Earth's rotation, Earth's orbit of the Sun, starsystem drift, galaxy drift, and so on. Of course it's not reasonable. But without it, the whole story falls apart. Therefore, the story is granted its own pocket universe in which to exist, and we all enjoy the story.
Long story short, I reject the premise of the question. You're trying to apply the rules of reality onto a pocket universe that may not bother with a fair number of such rules, so I'd personally say the question doesn't have a leg to stand on. Now, if you'd asked the question on Physics SE, that'd be a different case...
The factual answer is absolutely!
E=mc^2
For a 70 kilogram adult, you're talking 6.3 × 1018 joules by E=mc2.
That's 6×1015 btu, or 1.7×1012 kilowatt-hours.
That is enough energy to power the entire US for 16 years (which is way more efficient that nuclear power. The problem with this is that we currently have no way of accessing or harnessing this power. It is not unreasonable to assume that machines sophisticated enough to create the matrix in the 1st place would have solved this energy access problem.
Considering that the original question is,"Is the basic premise of of humans as a power source in The Matrix reasonable?" Not asking how or why the machines used humans as a power source. The answer is yes, every form matter in the universe contains energy which can be converted into power.
