With our current meagre computing abilities, we may not be able to simulate whole universes, but some say that if technology keeps progressing, one day it might become feasible.
But maybe it's already happened and we're all just a plaything for an advanced alien civilisation, says the latest video by Kurzgesagt - In a Nutshell. So, which one is it and how do we know?
The Universe may seem pretty vast, and stars pretty innumerable, but that alone does not preclude the possibility that what we're actually looking at, our entire existence, is just a computer simulation.
Theoretical physicists working in the quantum mechanics realm say that's all stuff and nonsense, but consider this.
"If our current understanding of physics is correct, then it's impossible to simulate the whole universe with its trillions and trillions of things - but we don't actually need to, anyway," explains the video.
"We only need enough of the universe to fool the inhabitants of our simulation into thinking that they're real."
According to the team at Kurzgesagt and their collaborator Jake Roper from Vsauce3, we could only have enough matter simulated around us for what we're actually interacting with.
For example, the chair you're sitting on might only have enough simulated atoms to form the outer shell, and is empty inside until you decide to break off a leg, only to see more simulated material inside at that point - but it was not there before.
Maybe your body is empty too, until you draw some blood, or open it up to find squishy simulated contents. In which case, all you need for feeling like you truly exist is just a consciousness.
But that's also where this mind-boggling philosophical approach to reality starts fraying at the edges, since there are a bunch of assumptions we have to make if we're to speculate that this world is just a fancy version of some galactic species' idea of the Sims 4.
The first of those assumptions: it's possible to simulate consciousness. That's a pretty massive hurdle to overcome, since we don't even know what consciousness is and what it's made of.
Even if it's enough to just have a disembodied brain to make consciousness happen, the brain is still the most complex structure we know of, with an insane amount of connections to be modelled.
Multiply that by the number of people that exist, and you have on your hands (or alien tentacles) the need for insanely huge computational power that may or may not be technologically possible.
Which brings us to the second assumption - that technological progress will actually advance to the point where such computers are possible, even if they have to be the size of an entire planet.
And even if we have tackled these first two assumptions, there are more considerations. Can a civilisation advance to such a technological point without killing itself, and if yes, would it even want to run such a simulation with Earth and its little people?
We'll leave it to the Kurzgesagt video below to explain the rest of the argument, but here's the worst part: whatever the case, there is no way for us to know whether we are real or simulated.
So while it's fun to think about these problems and bend our minds just a little, we might as well just live our best lives anyway. Simulated or not, ours is the only reality we have.