[MUSIC] This episode is supported by LegalZoom®. As our video games become more and more lifelike it's becoming clear that at some point perhaps soon our simulations will be indistinguishable from reality. If that's true, how do we know it didn't already happen? Could we be in a simulation... ...now? [THEME] Before I get into details, I want to share with you a conversation I recently had about this idea with my colleague at the Hayden Planetarium in New York City. In fact with it's director: Neil deGrasse Tyson along with comedian Eugene Mirman as part of Neil's Star Talk radio show. [EUGENE:] Leo zua... ...zusa? uhh on Instagram: "How about the recent articles about the possibility of us being part of a simulation and the Big Bang being just the seeding event of such a simulation?" "Thanks!" [NEIL:] I'm tottaly there. I'm diggin' it, every minute of it. [MATT:] Yeah? Alright. I wanna hear your... I wanna hear this [MATT:] Yeah? Alright. I wanna hear your opinion... I wanna hear this
[NEIL:] I'm lovin' it, I'm lovin' it. [NEIL:] I'm lovin' it. [NEIL:] I'm lovin' it.
[MATT:] Well, [MATT:] So who made this simulation? [NEIL:] Some- some snot nosed kid in their parent's basement of an alien civilization [EUGENE:] Well I Mean...
[NEIL:] Who's bored and they're more advanced than we are and have way more computing power than we are- than we do. [NEIL:] Who's bored and they're more advanced than we are and have way more computing power than we are- than we do. [NEIL:] Who's bored and they're more advanced than we are and have way more computing power than we are- than we do.
[MATT:] Right so there's this, like, little handheld nintendo [MATT:] Right so there's this, like, little handheld nintendo you can use... [NEIL:] Exactly so they program in enough detail to completely simulate every molecule in this universe
and we here for their entertainment. [NEIL:] Exactly so they program in enough detail to completely simulate every molecule in this universe
and we here for their entertainment. How else can you explain, when things are going along just fine in the world, that all of a sudden there's a complete disruption? [MATT:] The snot nosed kid. [NEIL:] Culturally, politically, economically a complete disruption I think that they throw it in for entertainment, that's what I think. [MATT:] Okay I'm- I'm gonna say I have two things to say firstly: I predict that you don't believe that; that's my first prediction I predict that you don't believe that; that's my first prediction
[NEIL:] Okay [laughs] [NEIL:] Okay [laughs]
[MATT:] I'm not gonna- I don't wanna put thoughts in your head. Uhh... [MATT:] I'm not gonna- I don't wanna put thoughts in your head. Uhh... [MATT:] I'm not gonna- I don't wanna put thoughts in your head. Uhh...
[NEIL:] There's an argument for why that's more likely than any other scenario I'll tell you that in a minute [NEIL:] There's an argument for why that's more likely than any other scenario, I'll tell you that in a minute, but go on. [MATT:] The numbers game okay so the idea that if you need to produce one universe capable of producing universe simulation [MATT:] The numbers game okay so the idea that if you need to produce one universe capable of producing universe simulation
[NEIL:] And that's all you need. [MATT:] And if that universe produces billions of universe simulations, then any universe that you happen to find yourself in... [NEIL:] ...is more likely to be simulated than the one universe that started it all. [EUGENE:] The way that, like, virtual reality now exits and, you know, video games have advanced it is likely that in, say, 1000 years whatever our virtual reality would be it is likely that in, say, 1000 years whatever our virtual reality would be
[NEIL:] Or 30 years. [EUGENE:] 30 years, but I was being generous
[laughter] [EUGENE:] 30 years, but I was being generous
[NEIL:] 1000 or 30. [EUGENE:] Well 30 years, whatever it was would potentially be physical like you could- you would be able to feel it. and it would...
[MATT:] Okay so... [MATT:] Okay so...
[NEIL:] No, no, no. It doesn't even require that. It just requires that what you program in there in your nintendo whatever it is has enough complexity that in the mind of the characters in that game they think they're real... [MATT:] Right, so
[NEIL:] ...that they have free will. [MATT:] It can't simulate the whole universe because to simulate the universe perfectly you need a computer the size of the universe. [NEIL:] Do you? [EUGENE:] Do you? [MATT:] Yes. [EUGENE:] I don't know. [EUGENE:] I don't know.
[MATT:] Because, I mean assuming it's a perfect... [NEIL:] Ah- da- da- da- [MATT:] The conversation goes in lots of fun directions. You can check out more on Star Talk radio link in the discription. Now, Neil uses an entertaining example of us being a sims game for hyper advanced alien basement dwellers. That's a hilarious image, but he's illustrating a very serious point. That under certain assumptions, virtual minds should vastly outnumber real minds in our universe. If so, shouldn't we be virtual minds? Let's dive deeper into this rabbit hole and decide if this actually makes sense. But before we do so, we should be clear about what type of simulation we're talking about here. Let's avoid the idea that the entire universe is simulated right down to every atom, electron or vibrating quantum field. That is a much deeper rabbit hole. One we'll need the Holographic Principle to explore. It's a whole big thing and we'll get back to it. Instead, today I want to talk about the idea that it's our experience of the universe that is simulated. That we are simulated minds in a virtual universe that has just enough detail to convince us of its reality I'm talking about so-called ancestor simulations. An idea proposed by Oxford University's Nick Bostrom. It goes like this: Bostrom argues that in the future, it will be possible to simulate the action of all the neurons of the human brain and to simulate the sensory input to that brain with enough fidelity to convince the simulation that it's a real person. Now, that's not too much of a stretch. There's a good chance we'll be able to do that within a generation or two. However, Bostrom crunches the numbers to show that a super advanced civilization could do this on such a scale that these sorts of virtual minds vastly outnumber real minds. Why would they bother? For science! He proposes that an advanced civilization may want to run simulations of its own history; to study the behavior of the types of minds that lived that history He calls these: 'ancestor simulations'. Let's look at the numbers. The human brain has 100 billion neurons and will over 100 trillion synapses. It's been estimated that the entire operation of a single brain could be simulated with somewhere between 100 trillion to a hundred quadrillion binary operations for every second of time that the brain experiences. Bostrom argues that it doesn't take anywhere near that much computing power to then simulate an external environment with the fidelity needed to fool the virtual brain at its environment is real. That's debatable because the environment needs to be perfectly consistent with respectable measurements made by all brains in that environment. But whatever. Let's go with Bostrom's assumption. A full ancestor simulation would simulate all humans that ever lived going back say 50,000 years. It's estimated that around a hundred billion people have lived and died. An average thirty year lifespan gives each of them a billion seconds And each of those seconds requires 10 to the power of 14 to 10 to the power of 17 operations multiply those numbers together and you get 10^34 - 10^37 binary operations to simulate all of human history. Bostrom says 10^33 to 36 but potato/potah-to, you can mess with any of those numbers and still remain within those few factors of 10. So how long would that take to compute for a super advanced civilization? Well Bostrom uses Robert Bradbury's estimate that a computer the size of a large planet a so-called Jupiter brain would be capable of performing 10 to the power of 42 operations per second. In other words it will be capable of simulating the entire mental lives of all humans in history a million times over every single second. Just one such computer would generate an insanely large number of lifelong mental experiences that are indistinguishable from the type of mental experience that you and I are having right now. That's true even if you scale back, say, to a computer the size of the moon or if you assume several more orders of magnitude in the computing power needed to run the simulation. Bostrom claims the following, which he calls the simulation argument: If ancestor simulations are something that even some civilizations end up creating so if they advance far enough and decide it's a good idea then most of the self-aware minds that ever come into existence will be simulated ones. therefore we are ancestor simulation. This sort of existential angst about disembodied brains being more common than real ones didn't start with Bostrom. The thought experiment is similar to that of the Boltzmann brain. the idea is that in an infinite multiverse it should be vastly more common for particles to randomly assemble into a brain that is having exactly your current experience of the world than for particles to randomly produce Big Bangs. We talked about that in our last episode. But both ancestor simulations and Boltzmann brains require us to invoke something like the Copernican principle. It tells us that we aren't in a special place in the universe. We're on a typical planet, around a typical star, In a typical galaxy, with one exception: our place in the universe must have been able to produce and sustain us. So we're somewhere habitable. That last addendum is an application of the anthropic principle. We must observe a universe, or a part thereof, that can have observers. Copernican reasoning with the dash of the entropic principle tells us that we should be the most typical, the most common, type of observer that could possibly be having our current experience. So if the virtual minds of an ancestor simulation are vastly more common than the minds of the original living creatures that made the simulation. and if the simulated experience is completely consistent with our own experience then it's more likely that we are those more typical observers. I should note that Bostrom is on record as placing the odds at less than 50% that we're a simulation. Why? Because he thinks it just is likely that either all civilizations die out before being able to make vast scale ancestor simulations or essentially no super advanced civilizations choose to make them. The ancestor simulation idea suffers from some of the same issues as the Boltzmann brain idea . We already talked about Sean Carroll's argument against concluding that we are Boltzmann brains. As soon as we do so, we must also conclude that we probably don't have the capacity to have carried out that line of reasoning in the first place. A Boltzmann brain is as delusional about the consistency of its mental faculties as it is about its existence before that instant. Similarly in the case of ancestor simulations upon deciding that we are simulated we acknowledge that there is no experiment that we can do to prove that we are not. The hypothesis is unfalsifiable. Bostrom himself points out that upon being found out by one of its resident minds the simulation can be instantly edited or rewound. In fact this editability is a necessity. These simulations can only cover a tiny fraction of the universe so they are prone to inconsistencies. It's far more computationally economical to edit out the discovery of these inconsistencies Than it is to simulate enough of the universe so that inconsistencies don't happen. Another big issue is just the potential for spectacular over-reach in using these Copernican and anthropic arguments. Bostrom himself even weighs in on this with regards to Boltzmann brains. He posits the type of Bayesian reasoning. So assessing the probability of a hypothesis being true by taking into account prior probabilities. Imagine a philosopher telling a cosmologist: that we must surely live in a universe capable of producing the most brains because that universe would give the maximum probability of our own existence which is the one thing we know for sure is true. Therefore scientists should come up with cosmologies that generate the most minds. The universe that has the most minds must be the one we're in. Bostrom labels this the 'presumptuous philosopher problem' and warns against such reasoning. But I wonder if he needs to reject his own answers to simulation idea on the same grounds. Highly specific scenarios like ancestor simulations or Boltzmann brains generate impossibly large numbers of minds that are identical to our own But where do you stop? With a little imagination yet more mind-factory universes can be conceived and simulated usses [people] multiply exponentially. Which type of fake you are you? Just for now I strongly recommend that we proceed as though we are real-life observers part of the original space-time. If you want to see more of my chat with Neil deGrasse Tyson head over to Star Talk Radio' Cosmic Queries. Link below. There we talk about how confident we can really be in our understanding of the galaxy and the universe and of scientific knowledge in general. It gets pretty philosophical and mind-bending as is much of star talk radio. very highly recommended. And once again a big thank you to all of our Patreon supporters. You make SpaceTime possible. And an extra huge thanks to Avan and Kayan Griggs, for supporting us at the quasar level. As special thanks we wanted to assure you two in particular that you are not simulations. We can't speak for everyone else. Last week we skipped comments because I was traveling so today we're going to talk about both the Oh My God particle and Boltzmann brains. So 0xFFFF1 wants to know what would happen to the unlucky sap struck in the head by an OMG particle. Well these particles are usually single atomic nuclei probably nothing would be noticed The particle may pass straight through your body only depositing a bit of ultraviolet Cherenkov radiation. If that happens inside your eye you'd see a flash however the particle might also hit a molecule. In that case it would damage or destroy that molecule. This is a problem if that molecule happens to be your DNA. In that case the damage to your genetic code can result in cancer. In fact this is why high radioactivity results in high cancer risk. KohuGaly made the argument that the Boltzmann brain thought experiment fails because it assumes random particle motion and that particle motion is actually deterministic. While particle motion may be purely deterministic the truth of that statement depends on which interpretation of quantum mechanics you wanna go with. However even in a perfectly deterministic universe there's a pseudo randomness that arises due to massive complexity, say in a room full of 10 to the power of 28 molecules. Unless there's a pretty powerful emergent force then even the pseudo random assembly of a Boltzmann brain is vastly more probable than the pseudo random assembly of a Big Bang. Henry School follows with a very good point on these emergent forces it's true that particles all converging on one spot in a room is resisted by more than just the improbability of the directions of their motion happening to point to that spot. Pressure builds up as density increases and that resists this convergence. But it's important to remember that the laws of physics are time reversible. Particles can start out in a high density configuration say in the corner of a room and then expand. In principle if you were to take such an expanded cloud of particles and exactly reverse their velocities then they would all end up back in their original configuration. that perfect time reversal would include the reverse of every particle interaction that happened in the original expansion. Now it's those same particle interactions that gives rise to pressure. That pressure is statistical in nature. Interactions can drive particles either outwards or inwards. Because particles can be pushed beyond the edge of the cloud there end up being somewhat more interactions driving particles outwards and inwards. As a result the net pressure is positive outward pushing. But pressure is as much a statistical emergent phenomenon as entropy. You can have spontaneous increases in pressure. In principle a perfect set of particle positions and velocities could be found such that the subsequent series of interactions leads to a large increase in pressure. An example of that would be the perfect time reversal of an expansion. It's also possible to imagine this happening randomly albeit with stunningly low probability. exurb1a says: "Amazing as always, you bloody brown coats". That means a lot coming from you, noble turtle.
