[Please enjoy this guest article by Ben Adams! —Ed.]
Science fiction blockbusters have a history of questioning reality. Total Recall, The Matrix, Inception and countless others show us a world where technology can create dream worlds indistinguishable from reality, raising the question that consumed the mind of Mal in Inception: What if your world is not real?
The existence of that technology would have profound implications for our understanding of the mind and of reality. The different implementations of that technology, though, can drastically change what these movies have to say about the mind and reality.
In The Matrix and Total Recall, the technology behind the dream world is industrial and direct – the machine is powered by banks of computers tended by skilled operators and the computer can interact directly with the brain. The implication is that the computer creates a perfect model of the brain and figures out how to manipulate the inputs to the brain to fool it.
Neo sees the Lady in Red because the Matrix calculated what his brain would see in the real world, and sends the appropriate electrical signals through the plug in his neck. Creating those signals and the world they come from takes computation—when Neo shoots his gun at Agent Smith, the Matrix has to do a calculation to decide if he hit anything. Just like in a computer game, every object requires constant computation to exist and every person requires constant attention to maintain the illusion – which is why the Matrix requires so much hardware to support it.
In stark contrast, Inception’s dream technology is minimalist. It fits in a briefcase, can be operated by a 14-year old kid on a moving train and is connected to the subjects via a tiny IV plugged into the arm. The filmmakers even posted a manual online, in which it’s apparent that the machine doesn’t do anything except distribute drugs, and has no power, cooling or electronic components. This strongly suggests that the computational heavy lifting is done outside the machine—and inside the brains of the participants. This is actually an efficient way of doing business—after all, the 7 billion most powerful supercomputers on Earth are walking around right now, eating Buffalo wings and watching Jersey Shore. Instead of creating the world from whole cloth and injecting it into your brain, Inception’s machine must modulate the natural dreaming process, and let the brain do most of the work.
But if the mind just is a meat-computer, it must be subject to all the same limits on time and energy that govern any electronic computer. The functional elements of a computing device need energy to change states, and can only change states so many times a second. Neurons use up energy when they fire and are chemically limited to firing at a certain speed. This presents no problem in The Matrix or Total Recall—the Rekall device just writes over the parts of memory it wants to encode and The Matrix runs at a 1:1 ratio with reality, so the brain functions at normal speed. Inception, though, allows for both nested dreams and time dilation—meaning it must work in a different way than the other two.
Yusef, the chemist, states explicitly that the sedative used for the Fisher job accelerates brain function to “20 times normal.” But this means the growth in activity is exponential—in the hotel, the brain is working 400 times normal. In the fortress, 8000 times faster. Yusef establishes this exponential ratio when he explains how the kick will work: 10 hours of flight time equals ten years at the third level (there are 8760 hours in a year). For whatever time they spend at that level, their rate of thought will have to sped up 8,000 times: in 1 second of flight time, their brain needs to be able to compute 8,000 seconds of information at the third level. This becomes even more problematic in the “limbo world,” since the precise ratio of time dilation in limbo is left somewhat murky, but the implication is that the time dilation there is even greater than it is on the other levels. Even assuming the ratio is only 20:1, the implication is that the brain is working 160,000 times normal rate while the subjects are in limbo.
That’s not just unlikely; it’s impossible. You can’t make neurons fire or chemical signals travel 160,000 times faster than normal. If it takes a single calorie per minute to dream under normal circumstances, that means the brain would have to consume 160,000 calories per minute in limbo. Sources differ, but most seem to agree that the brain working at normal speeds consumes about 20W of energy. Even assuming that the dreaming process is a small portion of that (say 1W of energy), that means that the brain in limbo would require 160 kilowatts of energy, and produce the corresponding amount of heat equivalent. The combination of nested dreams and time dilation makes the “brain as computer” description of the mind impossible.
All of this though, assumes that the brain is a conventional computer. In conventional computation, rigid limits are imposed by the need for a bit to be either a zero or one, and for an array of bits to have just a single state. If you have an array of 8 bits and you want to run a calculation on all possible combinations of those bits, you have to run each calculation separately – (0000000, 00000001, 00000010, etc., all the way up to 11111111, for a total of 256. Worse, each added bit doubles the number of calculations you have to run – quickly outpacing the capabilities of a conventional computer.
A theoretical quantum computer isn’t subject to this restriction. In the world of quantum physics, it’s possible for a quantum bit or qubit to be both zero and one at the same time, in what’s called a superposition. An array of qubits can be entangled with one another in such a way that they are all in a single superposition—8 qubits can represent all possible arrays of 8 bits, from 00000000 to 11111111 and everything in between. If a quantum computer executes an operation on that array of qubits, it is in effect running that operation on all 256 possible inputs at once. A theoretical quantum computer could scale exponentially, solving problems a conventional computer never could.
If the brain could make use of quantum computing effects, the normal limits on computation would not necessarily apply, and it’s possible that our brains could generate and keep up with a reality moving exponentially faster than our own. This is the quantum theory of mind, which argues that quantum effects are at the root of the brain’s incredible power, and may be the cause of consciousness itself. This solution is hinted at by the unstable nature of Inception’s dream worlds—once the dreamer becomes aware of or “observes” the dream, it collapses.
The brain-as-quantum-computer idea solves the problem of creating the dream world, but doesn’t solve the problem of sharing it: there’s still only a tiny IV line connecting the participants. Quantum brains could theoretically handle the calculations needed to create a universe 160,000 times faster than our own, but the result of those calculations has to be distributed through the dream machine at 160,000 times the normal speed of brain activity, running into the same problem as before. For a solution to this dilemma, we have to dig deeper into the different interpretations of quantum theory.