The following is an extract from our Lost in Space-Time newsletter. Each month, we dive into fascinating ideas from around the universe. You can sign up for Lost in Space-Time.
You can blame my youngest child for the existential crisis that I’m about to drag you into. When he gazed up with his innocent wide eyes to ask, “Mum, do you think we could be living inside a computer game?”, little did I know that my search for an answer would require a three-year journey of discovery! Could this all in fact be a computer simulation of a virtual reality so perfect that it appears to be real in every sense?
Day one of my quest started with an epic internal battle between the part of me that wears my Astronomer Royal for Scotland hat, and the other part of me who is still a toddler.
Advertisement
Astronomer Royal: “If a scientific question cannot be directly tested, it is, by definition, worthless. Move on.”
Inner toddler: “Why? How? What? Who? Are you real? Am I real? What is real?”
It took a week before I settled on a position. The ability to simulate reality hinges on the question of whether everything in our universe is mathematical – maths is the only language that computers speak – and the Astronomer Royal could certainly interrogate that.
Let’s start by celebrating the particle physicists who revolutionised our understanding of the building blocks of reality with their “shut up and calculate” prescription for quantum mechanics, (an approach that handily evades all the problematic philosophical questions that arise when you zoom into the quantum realm). In the 1970s, they gave birth to a single algebraic equation, the so-called standard model, that predicts the number of subatomic particles, their properties and how they interact with each other. Using this mathematical model, they predicted what should be observed when two protons smash into each other at close to the speed of light and break apart to reveal their innards. To carry out this challenging particle-smashing experiment, they built CERN, a 27-kilometre ring of superconducting magnets buried 100 metres under the France-Switzerland border. The perfect accuracy of the theorists’ predictions compared with the precision of CERN’s experimental measurements is breathtaking. The resulting discovery of the long-searched-for Higgs boson affirms our hypothesis that the universe is very mathematical.
But then the astronomers came along, throwing several spanners in the works. For example, particles called neutrinos change their personality – switching from one so-called flavour to another – in the eight and a half minutes it takes them to travel from the sun’s core to our detectors. This is an impossible feat according to the standard model. And, as a scientist who has made her name using giant telescopes to map invisible dark matter and dark energy across the cosmos, I find it deeply disappointing that the standard model also has nothing to say about these mysterious dark entities.
And what about gravity? Albert Einstein’s theory of general relativity concludes that our experience of gravity arises from the way clumps of matter warp the entirety of space and time, an exceptionally well-tested theory that appears to be true whenever astronomers look out into the universe. But how can this mass-bending-space-time version of gravity work when we zoom into the quantum world? Here, particles can essentially be anywhere and everywhere all at once, until the moment we observe them. Our “shut up and calculate” prescription for quantum physics doesn’t have an answer for that. If the universe is wholly mathematical, it’s clear that we have yet to uncover the full story.
That shouldn’t prevent us from looking to the future though. If you are willing to assume that a mathematical theory of everything is just around the corner, with advanced quantum computing available to run the calculations, what are the chances that our observable universe, and everything in it, is a digital by-product of such a simulation? In 2016, tech billionaire Elon Musk answered that question by blithely stating “there is a one-in-billions chance that this is base reality”: a one-in-billions chance that you are living in the real world that will, at some point in the future, develop the technology and scientific know-how to simulate perfect virtual worlds. The argument goes that, once simulators develop this skill, they won’t create just one virtual world, but billions of realisations played like computer games, over and over again throughout cosmic space-time. The total number of virtual humans would then dramatically outnumber the real-world humans in the “base reality”, creating the tiniest probability that you are one of the few that physically exist.
If our universe is truly mathematical, then it is possible that the quarks and all the subatomic particles we believe we are made from are in fact qubits, quantum bits of data that are currently encoding your reality within a futuristic quantum computing data centre. Let me reassure you, however, that contrary to the opinion of the world’s richest man, the probability of this is vanishingly low. Looking carefully at the practicalities of simulating a perfect virtual world, you’ll find that any futuristic software engineer would require an incredible amount of energy to succeed. Step aside Darth Vader, with your puny planet-killing Death Star! Meet my Galaxy Annihilator, which will harness the energy of the entire Galactic Empire to simulate our virtual universe: highly, highly implausible.
Does this mean that I can now confidently answer my son that we cannot be living inside a computer simulation, because creating our world would require far too much energy? Unfortunately, no. Take a moment to assess your experience of reality at this precise moment. Can you see the four walls of your room? Perhaps a cat is purring on your lap? Your experience, right here, right now, knows nothing of the goings-on in the far reaches of the universe, let alone what is happening in, say, Buckingham Palace. If you are living in a virtual reality, it does not need to be a perfect replica of everything that we can see when we look out into the cosmos, nor a complete simulation of all the 8 billion individuals who inhabit planet Earth. What if an energy-intensive, full-quarks-and-all simulation exists, but it features only you? AI is already sufficiently advanced to create realistic faces, places and conversations to paint in for everyone and everything around you. Could you be the centrepiece of a scientific experiment run by, say, a futuristic neuroscientist interested in studying your consciousness? It’s not impossible, but again it’s unlikely, as scientists are fairly efficient when conducting their experiments: the total number of simulations like this would be small.
On the off chance that your computational overlord has sent you this article to spark your curiosity, however, you might like to give them a little wave. But do not despair. The techno-philosopher David Chalmers has said that a virtual reality where you feel free will, love and laughter is as genuine a reality as any real world, and I agree with him. At the end of the day, it doesn’t really matter whether we are real, so long as we feel real.
Catherine Heymans is Scotland’s Astronomer Royal, and professor of observational cosmology at the University of Edinburgh, UK. Read about her three-year-long journey to find an answer for her son in her new book How to Design a Universe: The science of real and virtual worlds, .
