I'd heard about the "Maybe we're living in a Simulation" argument before but I had never read the details.
If I understand correctly it's basically a "follow the logic" idea.
Simulations get better all the time and as such eventually there will be universe simulators that can simulate an entire universe. Once you can do that there lots of people will run them therefore at any one time there will be millions X more simulated people than real people QED: Odds are we're simulated
This reminds me of the 1/2 way problem.
Before you can get somewhere you have to get 1/2 way there Once you reach the 1/2 point you have to get to 1/2 the remaining point (in other words, go to step 1) QED: You can never reach your destination because there's always 1/2 remaining
The logic seems to work and yet we get to our destinations all the time. Clearly there's a flaw somewhere. I think the same is true for the "We're living in a simulation" logic.
Here's where I think that flaw is. I think it's impossible to build a universe simulator. Currently it takes more than 1 atom to simulate an atom. It seems like a universe simulator would need to simulate all atoms therefore since you can't simulate all atoms without using more than all atoms you can't make a universe simulator.
Now you may say, like a video game, we don't need to simulate all of it, we only need to simulate the parts people look at. I think that's false for a universe simulator though. Video games don't actually try to simulate the real universe, they're fake, stories, they take huge shortcuts, they use "game" physics, etc. A real universe simulator though can't take those short cuts. Even if it only has to deal with observed portions of the universe those observed portions need to match real physics. That means even if no one is looking at someone part of this simulated universe, the moment they do look at it the simulator would have to compute all the physics for every atom for all of time since that part of universe was last observed until this moment so that it looks like time has passed correctly in that part of the universe. In other words the universal simulator can't take shortcuts like a video game. It has to simulate every atom, at which point we're back to it an impossible task because as pointed out above it would take more atoms to simulate atoms.
And so the flaw is clear. It's the original assumption that a universal simulator could actually exist. It can't.
Does that mean you can't have a holodeck? No, we could have holodecks, but like video games they'll take shortcuts. They won't simulate the entire universe. Take a typical video game that supports foot prints or skid marks or mud tracks, they always fade out over time, usually fairly quickly because keeping around the tracks of the player forever is just too much to compute. The same will be true of holodecks. They'll simulate some small portion of reality but not every detail and plenty of those details will be temporary. That's all great and it will be fun when we get there but it doesn't follow that from that we'll be able to simulate entire universes and all the causality needed to make them consistent which is what we'd need to simulate the universe we're in.
QED: We're not in a simulation