Bertram Russell produced a handy definition of philosophy, Philosophy is that discipline where ideas can be discussed that are not scientifically provable. Well there's a theme that fits that category and science fiction fans are all too familiar with it, the concept of the universe as a simulation.
Fred Pohl's story, The Tunnel Under The World, which you can read here, Pohl, Tunnel was probably my first encounter with the idea. Most likely I found it in one of those yellow jacketed collections of science fiction short stories produced by publisher, Victor Gollanz. I probably got it after school from the village library and read it instead of doing my homework. This, of course, was long before Hollywood discovered 'proper' science fiction. The movie franchise, The Matrix, is a better known expression of the concept of the universe as a simulation.
But it was not until 2003 that the topic became worthy of the attention of philosophers. Nick Bostrom published a paper in the Philosophical Quarterly, ARE YOU LIVING IN A COMPUTER SIMULATION? And it's produced considerable discussion. You can read that paper here http://www.simulation-argument.com/simulation.pdf.
The premise is, that with a sufficiently advanced technology, it would be possible to simulate our world, and all the people in it, on a sufficiently powerful supercomputer. The workings of all the brains of billions of sentient beings, the environmental effects, all the weather systems, the changes in atmosphere chemistry, even the motion of the tectonic plates would be modelled. But not perhaps what happens in deep space. Perhaps beyond our solar system the rest of the universe could be faked with a few simulations just good enough to fool the telescopes.
But why go to all the trouble of simulating something that has a real existence? Well, who wouldn't want to examine the past? Without the possibility of a time machine an Ancestor Simulation might be the next best thing. In fact, a simulation permits such tricks as replaying history after changing a small thing. How would things have turned out if JFK had not been shot? Would we still have landed on the moon? You could find out by pausing the simulation and concocting a clue to cause the police to search that book depository in Dallas. The simulation need not run in real time, the conscious entities being simulated, we humans, would not be aware of it being stopped.
There is a base level physical universe where the human population had advanced to what Bostrom calls Post Human level and these are the people who can harness sufficient resources to build the computer to run an Ancestor Simulation. But, and this is the main point, the probability of us being part of this one physical universe, rather than part of one of the simulations, is minuscule. This is because the one real, physical universe could host numerous simulated universes, and a simulated universe could itself host a further simulated universe when its technology was sufficiently developed. So, the probability of our existence as being part of a simulation is much higher than of our being part of the one physical universe.
The notion that we are actually part of a simulation has been proposed as an answer to the Fermi Paradox. The Fermi Paradox asks why, in such a large universe, have we yet to encounter aliens? Perhaps the original, physical manifestation of the human race, did encounter aliens but the simulation hardware cannot manage to simulate the alien solar system too. So the simulated universe, our universe, excludes aliens because there just isn't enough computer power to model them. This may even be why the base universe is bothering to run Ancestor Simulations - to find out how humans might have turned out had they not had their culture corrupted by an alien encounter.
A simulated universe has also been suggested as an explanation for one of the more far out aspects of particle physics, quantum uncertainty. This is where either the position of a sub-atomic particle or its momentum can be known with accuracy, but not both together. At this level of granularity, it is suggested, the simulation models particle behaviour only sufficiently well to support one or other measurement but not both simultaneously.
And so, if we all are part of a simulation, what then? If we behave badly we cause and possibly experience pain. It just happens to be that that the ultimate nature of our universe will forever be unknown to us. So how should we behave? Here is an interesting answer. www.vox.com simulation-problem
But what if we are not part of a simulation but part of the real universe? Well somebody has to be part of that initial physical universe. In fact that's a very scary thought. Let's consider how we might have beaten the odds?
If humanity should inevitably advance to the point of being capable of running numerous Ancestor Simulations and has not (or if you prefer will not) then something has gone very wrong. The likelihood is then, in our future, the human race becomes extinct before such Ancestor Simulations are technically possible. As a result we are part of a physical universe because that's the only one available, all those simulations will never be created so we are left with the only option possible, the physical universe.
So our condition, as part of the physical universe or as part of a simulation, is determined by an event in the future, by whether or not the human race survives!
We may not like it but if we are not part of a simulation the most likely case is that the human race will get wiped out.