Are We Living in a Simulation?

Can we trust what we perceive?

How can you tell whether anything is genuinely real?

You can observe some things for yourself, such as your fingers. To see others, including your chin, you need a mirror or camera. Then there are things you cannot see at all, yet accept because a parent or teacher told you about them, or because you encountered them in a book.

As a physicist, I rely on highly sensitive scientific equipment and complex mathematics to distinguish what is real from what is not. Yet none of these information sources is completely dependable: scientific readings may be inaccurate, my calculations may contain mistakes, and even your vision can mislead you - as with the dress that went viral online because no one could agree on its colours.

Since every source of knowledge, including teachers, can mislead us at times, people have long questioned whether any information can truly be trusted.

If nothing is trustworthy, can you be certain that you are awake? Thousands of years ago, the Chinese philosopher Zhuangzi dreamt that he was a butterfly, then recognised that he could instead be a butterfly dreaming that he was human.

Plato considered whether everything we see might merely be shadows cast by real objects. Perhaps the world we inhabit throughout our lives is not the genuine one at all; perhaps it is closer to an enormous video game, or the film "The Matrix."

The simulation hypothesis

The simulation hypothesis is a contemporary effort to use logical reasoning and observations about technology to answer these questions at last, arguing that we are probably living in something resembling a vast video game.

Twenty years ago, philosopher Nick Bostrom set out this kind of argument, drawing on the rapid advances being made in video games, virtual reality and artificial intelligence.

That progress has carried on, meaning that people today can enter immersive virtual-reality experiences or speak with artificial beings that appear conscious.

Bostrom extended these technological developments into the future, envisaging a world where trillions of human beings could be simulated realistically. He further argued that if somebody could make a simulation of you that appeared identical to you from the outside, it would feel identical from within too, including all your thoughts and emotions.

Assume that is correct. Imagine that, perhaps in the 31st century, humanity can simulate anything it wishes. Some people will probably be enthusiasts of the 21st century and operate numerous simulations of our world, either to study us or simply for entertainment.

Bostrom's startling logical case is this: if planet Earth in the 21st century existed only once, but is eventually simulated trillions of times, and if those simulations are sufficiently convincing that their inhabitants feel like real people, then you are probably living in one of those trillions of simulated Earths rather than on the single original Earth.

The argument would seem still stronger if powerful simulations could already be run today. However, provided you believe people will create such simulations in the future, logic says you should probably believe you are living in one now.

Signs we're living in a simulation … or not

If we do inhabit a simulation, would that account for anything? Perhaps the simulation contains glitches, explaining why your phone was not where you were certain you left it, why you knew an event would happen before it did, or why that internet dress appeared so strange.

Our world resembles a simulation in more basic respects too. There is a specific distance, far smaller than an atom, below which physicists' theories of the Universe cease to work.

We also cannot see beyond roughly 50 billion light-years, because light has not had enough time to arrive since the Big Bang. That is rather like a computer game in which you cannot see anything smaller than a pixel or beyond the edge of the display.

Naturally, every one of these observations has other possible explanations. After all, you may simply have remembered incorrectly where you left your phone.

Yet Bostrom's argument needs no scientific evidence. It remains logically valid so long as you truly expect many powerful simulations to exist in the future. This is why prominent scientists such as Neil deGrasse Tyson and technology leaders including Elon Musk have accepted it, although Tyson now gives the possibility even odds, at 50-50.

The limits of future simulations

Some of us remain more doubtful. The technology needed to operate simulations this vast and realistic would be so powerful that Bostrom calls their creators godlike, while acknowledging that humanity may never become so capable at simulation.

Although it remains far from settled, the simulation hypothesis is a striking philosophical and logical argument. It has questioned our most basic ideas of reality and fired the imagination of millions.

Zeb Rocklin, Associate Professor of Physics, Georgia Institute of Technology

This article is republished from The Conversation under a Creative Commons licence. Read the original article.