This is a repost from the original version of this blog–now, rewritten somewhat.
There are plenty of things to lie awake at night worrying about.
What if I lose my job?
What if I can’t pay my mortgage?
What if all my teeth fall out?
Some of these worries are sensible, as worries go (did I turn the oven off before I went to bed?) and some are less so (what if I just somehow don’t die of old age, so when the sun turns into a red giant and eats the planet, I’m still on it?). But be reassured that one thing you don’t to worry about is the possibility that we are all being held in bondage to intelligent machines, as the The Matrix movies.
Don’t get me wrong; if intelligent machines do take over the world, I wouldn’t trust them not to put us in bondage, but the thing of it is human beings make terrible batteries.
(If you have not seen “The Matrix” and want the first twenty minutes to be a surprise, don’t read any further. Go see the movie, then come back.
In that trilogy, it turns out that what we know as reality is actually a virtual-reality program used to keep human minds busy while their bodies are used as a power source for intelligent computers. It seems that war has broken out between humans and the machines, and that because the machines were, at the time, solar-powered, humans “scorched the skies,” blotting out the sun somehow with permanent thunder-clouds. To survive, the machines plugged humanity into their power-grid, raising whole generations in little pink tanks, harvesting the heat and electrical power of millions of bodies. The living, we are told, are fed on the dead, a gruesome, unwitting, cannibalism.
The reason we don’t need to worry about this is the Second Law of Thermodynamics, which states that energy cannot be recycled. Every time energy changes form, some of it is lost. For example, say you make electricity by burning fuel to run a steam turbine and then use all of that electricity to boil water, you’re never going to be able to boil as much water as the original power plant did.
In other words, this
Won’t work (as the author of the comic well knows).
This is why perpetual motion machines don’t work; all systems need fresh influxes of energy or they wind down, inevitably. It’s also why a gas stove has a smaller ecological footprint than an electric stove, if the electricity is derived by burning gas.
Most people have heard of the Second Law of Thermodynamics, since it comes up in some high school or college science classes, and occasionally in discussions of creationism as well. It isn’t an obscure concept, but somehow we aren’t used to thinking of it as part of our own lives. Perhaps we’re so used to thinking of “energy” in a metaphoric or metaphysical sense that we forget energy is literal, too.
Just the be clear on this, feeding a human population on their own dead indefinitely is impossible because each time one human ate another, most of the energy in the body would be lost. A 150 pound human needs to eat more than 150 pounds of food over a lifetime. Without sunlight (which the world of The Matrix no longer gets) the entire biosphere would lose its influx of energy and grind to a halt. No energy for the machines to harvest, and no food for the few human freedom-fighters.
Obviously, The Matrix Trilogy wasn’t intended as a physics treatise, but for all fiction must obey an internally consistent set of rules or the plot gets hard to follow. If a movie has talking animals or flying people, that’s fine, but if these elements appear with no warning in the middle of an otherwise realistic movie, it’s jarring at best. That the unexplained violation of the laws of physics it The Matrix does not seem to have distracted many people is worrisome.
The Second Law of Thermodynamics is central to many conservation issues. For example, an apex predator living on the meat of smaller predators needs a huge amount of land—enough land to grow enough plant matter that after five steps of energy loss there is still enough fuel left to support a breeding population of active animals. Without a visceral understanding of energy flow, it’s hard to think clearly about how much land really needs to be set aside for large predators.
Humans are also large animals, and we need a certain amount of land to maintain ourselves. We not only consume energy by eating, but also for heating, transportation, and everything else. Although as humans we can get very creative with what we use energy for and where we use it, our activities are limited by the total amount of energy coming into the planet as sunlight, and also by the energy needs of the other components of the biosphere; if we use more energy than our ecosystem can spare, the ecosystem begins to collapse, becoming less stable and less complex. The reason that the Industrial Revolution saw such a dramatic increase in the power at our disposal was not that humans suddenly got smarter, but that we began borrowing energy from the past.
Fossil energy is exactly that; energy that fell on our planet’s surface and was harvested by plants millions of years ago. Using more energy than the sun gives us per year is only possible when we take energy that the sun gave us in the past. Except that energy is already doing something; that ancient sunlight is busy sequestering carbon. Appropriating that energy to drive to the grocery store inevitably changes the atmosphere. There is no avoiding the fact that the kind of energy use we have become accustomed to is warping our planet and is temporary. Environmental sustainability means using less energy, period.
But, at least you don’t have to worry about “The Matrix” anymore.