The machines are keeping humans alive for their body heat, right? But they also have nuclear fusion reactors, and (while I haven't run the numbers) I'd be willing to bet that a single fusion reactor would generate more net energy in an hour than all the humans on today’s Earth would in a day.

I have one more additional doubt:

Why people, instead of animals that don't need a computer simulation to keep their brains entertained?

Why do the machines keep humans alive if they have nuclear reactors?

  • 15
    Because it would make for a terribly boring movie otherwise?
    – Napoleon Wilson
    May 8, 2013 at 8:05
  • 1
    Related: scifi.stackexchange.com/questions/1263/…
    – Geerten
    May 8, 2013 at 9:10
  • 3
    "Why people, instead of animals that don't need a computer simulation to keep their brains entertained?" - You sure they don't? Or, you sure humans do (well in the movie they do, but in the movie animals could as well need a matrix)? Humans probably don't really need a matrix either, but the movie needs one that replicates the 20th century. So given this rather unlikely premise, it is hard to say how/if it would work with animals and if they might need their own matrix. But then again "it wouldn't make for an interesting movie, man!"
    – Napoleon Wilson
    Sep 4, 2013 at 13:44
  • Because the original reasoning, that humanities brains were to be utilized in some kind of large scale supercomputer for the machines purposes, was turned to energy production due to executive meddling. Sep 2, 2014 at 20:10

8 Answers 8


Well, whatever the reason machines keep humans alive, it is definitely NOT because of humans' excellence in the role of batteries. However it is possible that the machines themselves are spreading that myth. (For example Morpheus would believe anything the Oracle says). That machines don't really need humans for power is revealed in the last part, when the Architect agrees to free all humans from the Matrix.

The actual reasons may be much more complicated, and much more humane. The machines just don't want humans to become extinct, just like we humans are trying to protect Siberian tigers, as well as other endangered species. Even though a tiger may kill a human given the chance.

However protecting humans is much harder than the tigers. You can't put them in a cage, because then their minds will degrade. You can't let them roam free, because they probably won't survive in the new world, or because they will probably keep trying to fight the machines until they kill themselves. Humans aren't very rational, you see.

As a solution, the tandem Matrix - Zion was created. The Matrix is conveniently situated right next to the Zion so that people in Zion can focus the majority of their energy in "freeing" others from the Matrix. Also, quite conveniently, the Matrix lacks any real defense mechanisms.

If there was just Zion without the Matrix, the humans would be trying to develop nuclear weapons or EMP bombs in order to launch the assault on the machines. Obviously they would fail, but they will also kill themselves in the attempt.

If there was just Matrix without Zion, then such system would run a risk of collapsing and destroying the humankind if some unforeseen catastrophe occurs. The machines aren't really good at adapting to sudden changes. And they are vulnerable to other unpredictable factors (such as Agent Smith). The machines know that, but they can't do much about it.

Now why do they need to destroy Zion every now and then? Well, first of all they probably don't see it as much of a big deal -- the population of Zion is comparatively low. Plus they want to keep them from acquiring too dangerous technologies. Plus in most cases the goal is not really destruction, but rather the threat of destruction. For example in the last movie, several EMP charges could have destroyed the majority of attackers. The machines know that, and they probably launched the attack with the goal of failing, but making humans more scared. The machines didn't foresee however that Agent Smith would be able to interfere and stop those EMPs.

So in summary, it's all a well-orchestrated plan to keep humans busy, and alive.

  • 2
    There are several factual inaccuracies here. "The Matrix" isn't near Zion, they need to use ships to get to and from places where they can hack in to the Matrix. The plan for the attack in the last movie was for them to wipe out Zion, the Architect says as much.
    – user209
    May 9, 2013 at 15:58
  • 13
    We don't know the actual distance. But considering that "Machines" had an entire Earth surface at their disposal, Zion is suspiciously close to the Matrix. They use ships primarily because the city itself is deep underground. As for the attack, they chose rather inefficient method if their real goal was wiping humans. A lethal gas, or air-borne virus would have been much quicker, and reliable, and cheaper. You can't really trust everything Architect says, besides he himself might not possess the full information.
    – Pasha
    May 10, 2013 at 0:06
  • 4
    This is one of the best Matrix explanations I've ever read!
    – Liath
    Nov 18, 2014 at 11:51
  • 1
    Great! They should make a film about it! Oh wait.
    – Trollwut
    Jul 10, 2015 at 11:04
  • @user209 Basically all of the actors (that is, key players) are unreliable narrators in the Matrix films. Each have their own agenda and beliefs and don't have the full information. The closest to a source of truth is the Architect, but his only goal is the creation and preservation of the matrix.
    – Stephen
    Dec 9, 2016 at 2:15

It's part of the allegorical elements of the film. By being powered by people, the machines are literally taking the power from the people (i.e. the opposite of 'power to the people'). So the machines are only existing because of the people's power, the people having sort of surrendered it to the machines. This is in addition to the in-Matrix subjugation humans also suffer.


The original storyline had the machines using the humans as a giant networked brain on the premise that the brain's processing power is far ahead of any hardware AI.


Unfortunately the movie bosses considered this concept too highbrow for action / sci-fi audiences of the time. They thought we wouldn't get it, so the motivation of the machines was re-written (i.e. dumbed down) to have them using humans as a power source.

As others point out, this doesn't really stack up to a reality check, but really all they needed was a (vaguely) plausible reason for the matrix to exist. Using humans as batteries (or for the brain's supposed processing power) is a MacGuffin.


After the success of The Matrix, the studio took even more creative control and essentially gutted the sequels of all philosophical content, turning them into highly stylised action films.

  • 4
    Worse than no philosophical content in the sequels was inarticulate content. I remember when the cast and crew of sequels were boasting of "layers" of meaning in the sequels. Which whilst technically true, was also indicative of poor script pacing and dialog balance. Meaning in the first movie unfolded like a flower; meaning in the others was bucket of coleslaw slopped over the characters. Nov 18, 2014 at 13:46
  • 1
    I'll admit I wouldn't mind seeing a "Special Edition" where the explanation is changed back to processing. They could even CGI a CPU over the battery Morpheus holds up. Nov 18, 2014 at 14:42

I think, within the movie's logic, it is because humans reproduce and therefore continually provide energy (ISTR that humans are even fed on human corpses) whereas nuclear reactors use finite energy sources.

  • While not being the downvoter a reason might be that it sounds like humans were an infinite energy source (which as you probably know from biology/physics they can't be).
    – Napoleon Wilson
    Sep 4, 2013 at 13:42
  • The film does come very close to implying this. In the first film they explicitly state that dead humans are recycled as food. The science behind the Matrix film series contains many errors, have a look on the ISMP film review of it.
    – Stefan
    Sep 4, 2013 at 21:04

My interpretation was that the body farms weren't used to generate energy, but to store it. i.e. the duracell battery that Morpheus holds up. If you have pulsed or unpredictable power sources, you need massive storage to match the supply to the demand. The leading fusion power concept today is the tokamak, which is a pulsed machine. Renewable energy sources are generally weather-dependent and hence unpredictable.

On the other hand I can't imagine that humans are very efficient for energy storage, compared to animals or any other inanimate technology. In that respect it seems more like a plot device.


My theory is that the Machines lack one thing that only Humans can have -> "Creativity".

The machines can maintain the status quo, but for any new technology development, they need human brains. Therefore, the machines keep all humans alive, to harvest their brain power for advancing the technology.

  • Yet they wouldn't keep them in the 20th century and rather further their advances to gain actual new ideas. The machine war is probably much in the future and humans already had developed things far beyond what they could think of in the 1999 of the matrix. In fact the machines already use far higher technology than what was current at that time.
    – Napoleon Wilson
    Sep 9, 2013 at 16:28
  • Re:Christian, I'm talking about just brain power, not humans developing technologies in the simulation, but the machines just need human brain to develop new technologies on their own. As you may know, human brains is possibly a billion times faster than the fastest computer.
    – KoKo
    Sep 12, 2013 at 3:52
  • So what is it then what you're saying? That the machines use the brains that are currently occupied by the matrix to think their own stuff for them? Sounds infeasible. What one calls brain power is either the actual electircal power of the brains, whose harvesting wouldn't be any different from the premise of the question and all the other answers, or the conceptual power of the thoughts that can be thought by them (which seems to be what you're after), which isn't really harvestable in any way, especially when those brains are ocupied by a different simulation.
    – Napoleon Wilson
    Sep 12, 2013 at 7:29

The machines creates the reality humans live. In exchange humans create the ultimate reality the machines depend to exist. The machines figured out that their artificial brain have no effect on the wave function and matter can never exist without the effect of wave function collapse caused by human brains. I hope this is the reason the movie creators had in mind. They would come up with a movie explaining how it was before the machines took over and as they exterminated humans the machines noticed that chunks of the material world also would disappear and until they fix this inconvenience they need the humans alive. Hope this is the reason as I would definitely watch the prequel!


Human-computation. The machines delegate problem solving / processing to humans, like micro-work/crowd-sourcing. See related SE question on this. Human-based computation is:

A computer science technique in which a machine performs its function by outsourcing certain steps to humans, usually as microwork. This approach uses differences in abilities and alternative costs between humans and computer agents to achieve symbiotic human-computer interaction.

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .