"If real is what you can feel, smell, taste and see, then 'real' is simply electrical signals interpreted by your brain."
This is a quote by Morpheus from the 1999 hit sci-fi film The Matrix. The movie is about simulated realities - the theory that humanity is unknowingly trapped inside a simulated reality, which is called The Matrix.
The simulated reality hypothesis states that reality, at least what we believe to be real, could in fact be simulated. If a civilization is developed enough, then it would theoretically have enough computing power to simulate entire universes artificially.
Think of it like you are in a video game. The world around you has a certain set of rules, and you can interact with the environment following those rules.
The catch is, you don't know that you are in a game and none of it is real. To you, that simulated world made by lines of code is reality.
A version of the simulation hypothesis was first put forward by René Descartes, a renowned French mathematician and philosopher from the 17th century. However, the idea of simulations can be traced back to ancient civilizations like the Maya and Ancient Greece.
This idea can also be found in Plato's "Allegory of the Cave" from Republic VII. The allegory hypothesizes that some people are chained inside a cave from birth.
They are kept facing the cave wall with a fire lit behind them. They cannot turn around and see the fire or the outside world. They can only see shadows on the cave wall when people pass by the fire behind them.
As that is all they have seen for their whole life, they think the shadows are real entities, not just a mere reflection. To them, those shadows are the reality.
Even if they were released and saw the real world, they would not believe it and simply reject it. To them, ignorance is bliss. People accept the reality of the world with which they are presented.
Nick Bostrom, a Swedish-born philosopher and a professor at Oxford University revived this theory in 2001. He argued that there is a chance that we are living inside a simulation in his 2003 book "Are you living in a computer simulation?"
According to our current understanding of physics, we cannot simulate trillions and trillions of objects. But we don't need to anyway. We just need enough to make the subject believe it's real.
Maybe the wall in front of you is actually hollow. The bricks and sand don't exist until you break the wall apart. Maybe you yourself are hollow and the organs inside you don't exist until a surgeon cuts you open.
Still, it's not easy to simulate reality. There are some important criteria to fulfill, according to Bostrom.
The first criterion is that the human consciousness can be simulated. The subjects of the simulation need to think that it is real, emphasizing on the thought.
The problem is, no one knows what consciousness is. It may be more than just our physical brain.
But for the sake of argument, let's say that we can generate consciousness by simulating a brain.
Even that is difficult, as our brain performs 1 x 1017, or one hundred million billion operations per second.
Let's say we wanted to simulate two hundred billion humans with an average lifespan of 50 years throughout our history. In that case, we need a computer able to handle 3e+40, or one million, trillion, trillion, trillion operations per second.
This is more than the number of stars in the observable universe. A computer of this scale is impossible. Or is it?
This is where the second criterion comes in. If technology develops at the same rate and there is no limit for it, then maybe sometime in the future, a supercomputer with such power can be built. This is assuming that advanced civilizations don't destroy themselves.
We, humans, have a slight little flaw of being able to completely obliterate ourselves. There is nuclear war, famines, asteroids, and good ol' climate change.
Basically, we are inherently self-destructive, so no big deal.
The third criterion is that a civilization needs to exist to achieve that level of technological development.
The fourth criterion is whether a posthuman civilization wants to make such a simulation. To think that we would know what advanced civilizations would want is pretty arrogant. It would be like an ant trying to understand Moonlight Sonata.
This is might be an incredibly stupid idea to them.
But, if these criteria are met, then it is possible that we may be inside a simulation. And if posthuman civilizations have that level of computing power, then they can probably run billions of such simulations at a time.
In that case, the possibility of you existing in the real world instead of a simulation is one in a billion chance, which is pretty low.
The simulation theory blurs the line between what's real and what's not.
As the Chinese philosopher Zhuangzi said, "Once I dreamt, I was a butterfly. I was conscious that I was a butterfly, unaware that I was a man. Soon I woke up. Now I do not know whether I was a man dreaming I was a butterfly, or I am now a butterfly dreaming I am a man."
The fact is, you don't need to care about all this. You wouldn't know if you lived in a simulation anyway.
So, believe what you want. Because for all we know, we might be living in a simulation made by dinosaurs to see how the world would turn out without them.
Finally, I am sorry for being the cause of your next 3 am existential crisis. Sleep tight!