World on a Wire: Are we living inside a simulated reality?

World on a Wire (1973) movie poster

It sounds like the plot of a science-fiction movie: the world we live in may not really exist, but might only be simulated by a sophisticated cluster of computers — and we ourselves are part of this gigantic simulation, which encompasses the entire universe as we know it. What has long been only a philosophical thought experiment, is now being investigated by physicists and computer scientists with scientific scrutiny.

Jörn Müller-Quade

Jörn Müller-Quade, professor of Computer Science at the Karlsruhe Institute of Technology and head of the research group Cryptography and IT Security, agreed to discuss these highly speculative and mind-bending ideas.

Professor, first off: what kind of emotions do these ideas evoke in your mind; the entire universe as a “World on a Wire”, with all of reality controlled by programmers outside of our perception?

This might change over the course of our conversation, but my first reaction to that is somewhat dismissive — I think the laws of nature are much too harmonious und coherent for them to be a simulation, at least in the sense that things are only “faked” to our brains.

You have to differentiate: it could either be a simulation like in a video game, where light reflections and other phenomena are specifically faked to fool the player. Or, it might be a “true” physical simulation, which could in the end be indistinguishable from an actual universe.

Let’s assume the simulation hypothesis is true; we actually live in a simulated world, and don’t know about it. How would a simulated world like this look from the outside? Like a data center? Or maybe more like a giant net of "pods", like in The Matrix or Avatar?

It would probably look like a data center of the future, and how those are going to look, nobody knows for sure. If we are, in fact, a simulation embedded within a world “above” us, then there’s two options: either, the technology of the hyperworld might be very similar to ours, because they are trying to simulate a universe similar to theirs. In that case, we at least get an impression of how their world looks and behaves. On the other hand, it could be something entirely different; it’s possible that we are just one iteration of some form of genetic algorithm, where different variants of conditions are tried out until, randomly, something like our current conditions emerge. If that’s true, then we’re probably running on computation technology that we can’t even imagine; maybe even with entirely different physical laws.

Empirically, Moore’s Law has correctly predicted the doubling of computational power every 18 months (to simplify its predictions a bit). Already today, entire motion pictures can be rendered digitally, instead of actually filming them, even though this process is still somewhat cumbersome. Skipping ahead 20-30 years, will we have a simulation that is accurate enough to much smaller scales, for example on the level of atoms? Or do we at some point encounter fundamental limits of computation?

One insight that seems philosophical, but is actually founded by Computer Science, is: simulating a sufficiently complex physical process is likely to take as many computational steps as the process itself. What this means is: I don’t think it will be possible, within our limited universe, to accurately simulate another universe at the same scale of ours. However, if we manage to advance computational power, through Moore’s Law or otherwise, it might reasonably be possible to accurately simulate single people or smaller communities of people and study their interactions. The Human Brain Project, for example, is trying exactly that: to simulate a human brain on the neuron level. They are trying this even though we haven’t exactly figured out what exactly is happening at the neuron level. However, it's plausible to imagine that the successor of the successor of the Human Brain Project will manage to significantly improve this understanding. When that happens, we'll have to spend some thought on to what extent such a simulated brain can be considered a sentient organism of its own and how it might perceive pain and suffering.

Going from simulated brains to simulated universes — does the simulation of an organism or part of an organism differ from the simulation of all of physical reality?

I don’t know that for sure, of course. But my speculation is that conscience and thought activity are created when something sufficiently complex and adhering to the correct rules is simulated. For that to happen, you might not even have to descend to the physical level of quarks and quantum chromodynamics. A much simpler model, containing for example quantum information theory, could suffice. Actually, Penrose even speculates1 that quantum effects are a necessary precondition to achieve conscience; this would mean that only quantum computers will allow us to accurately simulate a level of thought activity that we would describe as sentient.

Scientists in Washington and Bonn have investigated2 how well a simulation of our universe at a physical level could work, no matter what kind of computer they use. In particular, they looked for numerical inaccuracies that would look like the “Glitches in the Matrix” for skeptics to find to detect the simulation. Sadly, they came to the conclusion that it’s likely easier to “fix” the simulation from the outside than for us, on the inside, could detect such glitches. Does that mean that we don’t even stand a chance to prove that we don’t live in a simulation?

If these glitches are very rare, we would likely always interpret them as measurement errors. Since our priors are biased against a simulation, we would believe a hypothesis like this only if we had enormous amounts of reproducible data from a controlled lab setting. Therefore, the only possibility for us to find out that we live in a simulation might be that the ones who are simulating us consider us mature enough to actually tell us directly.

What kind of advice would you give to the creators of our simulation? What should be the goalpost of their work?

I think that the world right now has too much suffering and pain for humans. If this is really a simulation, I would question whether that is really necessary, or if it can be avoided. On the other hand, I'd take this as an indicator that our world is not a cruel simulation, but a harsh reality that we'll have to work on ourselves to make it a better place.

Interview conducted in German and edited by Jonas Schneider for Radio KIT. Download the original audio (MP3, 06:11).

  1. “Reply to criticism of the ‘Orch OR qubit’ – ‘Orchestrated objective reduction’ is scientifically justified”. Stuart Hameroff and Roger Penrose. Physics of Life Reviews (Elsevier) 11 (1): pp. 94–100, 2013. Available online. 

  2. “Constraints on the Universe as a Numerical Simulation”. Silas Beaneand, Davoudi Zohreh, Martin J. Savage. INT-PUB-12-046 (Cornell University Library), 2012. On arXiv.