Nowadays when people discuss the concept of a simulated universe, they generally discuss the argument presented by Nick Bostrom. Bostrom's argument has got an amazing amount of attention, considering the fact that it is very weak. Bostrom reasoned that there may be super-advanced extraterrestrial civilizations that could build super-sophisticated gigantic computers, perhaps as large as planets. He claimed that such computers would be capable of simulating all of human experience. He argued that if a super-civilization was interested in simulating human experiences, it might run a gigantic number of “ancestor simulations” simulating the experience of creatures such as us. There might be so many such computer-generated “ancestor simulations” that it might be more likely that we are living in such a simulation than that we are regular beings living in a regular material reality.
There are several reasons why this argument is not very convincing. One is that it relies on a reductionist theory of the human mind, the idea that the human mind is just some by-product of material effects. There are very good reasons for believing that such a theory is wrong, and that something like human consciousness could never be produced by any computer. Among such reasons are psychic experiences suggesting that there is a lot more to human consciousness than brain activity, and also the fact that some humans have had pretty normal human consciousness even though very much or most of their brain was lost to disease (as documented by the physician John Lorber). Another reason (discussed here) is that while super-advanced civilizations might try their hands at running ancestor simulations, we have no reason to think that they would keep running such simulations for thousands of years (particularly since such super-advanced civilizations would have a trillion other fascinating projects they might busy themselves with). The chance of being part of some “ancestor simulation” that might be run during only a thousandth of the history of a very old super-advanced civilization seems very low. Then there is the fact that if we try to argue from a likelihood of extraterrestrial civilizations to a likelihood of a simulated universe, then once we reach the idea of a simulated universe we reach an “all bets are off” stage, in which we no longer have a basis for believing in the likelihood of extraterrestrial civilizations (since such a likelihood involves assuming the physical reality of external planets, something you can no longer count on if the universe is simulated). It is not logically valid to start with a premise and then use that premise to reach a conclusion that undermines the very premise you started off with.
So Bostrom's argument about a simulated universe is weak. But is there a stronger case we can make for such a concept? There may be. Below is a general argument for a universe that is simulated in the sense of not having the age and material reality that we normally suppose. Although the argument mentions a simulated universe, it is not explicitly referring to a universe that is a computer simulation.
Here is a short version of the argument:
- If the universe is in some sense simulated, we would expect that it would have various artificiality indications, which might include things such as indications of inexplicable sudden beginnings, internal self-contradictions, or regularities that are incredibly unlikely to exist by chance.
- Our universe seems to have quite a few such artificiality indications.
- So there is a good chance our universe is in some sense a simulation – perhaps something that exists as a matrix or substrate for conscious experience rather than something that exists as a physical reality independent of consciousness.
To explain the concept of an artificiality indication, let me discuss my favorite episode of the classic TV series The Twilight Zone. The episode is called “Stopover in a Quiet Town,” and begins as a man and a woman find themselves waking up in a deserted town. Their memories are scattered, because they were drinking too much the previous night. The couple doesn't know how they got in this town. Searching around in the town, the couple finds strange things – for example, a refrigerator has only plastic food, and there is a stuffed squirrel in a fake tree. Finally the couple notices a giant body above them. We see a giant girl pick up the couple in their hands. We then hear the girl's mother say the wonderful line, “Be careful with your pets, dear – your father brought them all the way from Earth.” Evidently the couple has been abducted by extraterrestrials, and put in a simulated human environment. The plastic food and the stuffed squirrel were artificiality indications – clues that their environment was an artificial construction.
The question is: do we have any such artificial indications in our own universe? Perhaps we do.
One type of artificiality indication you can imagine is an inexplicable sudden beginning. For example, in the “Stopover in a Quiet Town” scenario, the couple might have woken up with a dark sky outside, and then suddenly it might have been light (as the giant girl turned on the lights above them). Are there any inexplicable sudden beginnings that we know of in our universe? Quite a few, apparently. You can start with the Big Bang, the mother-of-all inexplicable sudden beginnings. Then there's the almost equally inexplicable origin of life believed to have occurred billions of years ago. Then there's the quite sudden Cambrian Explosion, in which a large fraction of the animal phyla appear suddenly in the fossil record about 550 million years ago. Then there's the apparently rather sudden origin of modern consciousness about 90,000 years ago.
We actually see little evidence of transitional fossils in the fossil record. It's almost as if someone had made a rather half-hearted attempt to simulate a natural past history of life on our planet, without doing all the work needed to leave behind a fully believable story in the fossil record. This may be a little like the fake food in the refrigerator in “Stopover in a Quiet Town.”
Another type of artificiality indication is an inconsistency. For example, suppose the couple in “Stopover in a Quiet Town” had found that the post office sign said “Pleasantville Post Office,” but the sign at the town's front said, “Welcome to Sunnyville.” This inconsistency would be a clue that the town was an artificial simulation.
Can we find such inconsistencies in our universe? Perhaps we can. Quantum field theory predicts that the vacuum should be incredibly dense, far denser than steel. But we see in outer space a vacuum that is almost empty. Quantum mechanics is actually inconsistent with general relativity, but both make predictions that have been very well verified. Are such inconsistencies signs of a universe that is artificial or simulated?
Conversely, when things are too consistent and unvarying, that can be an artificiality indication. So suppose that our “Stopover in a Quiet Town” couple had started to examine the rocks in the small town they woke up in, and found that all of the rocks were of two sizes: pebbles exactly one inch in length, and larger rocks exactly five inches in length. And suppose that all of the pebbles looked exactly the same, and all of the larger rocks looked exactly the same. That would be a strong artificiality indication. Is there anything like that in our universe?
Perhaps there is. When we get to the subatomic level, we find that all protons have exactly the same mass and charge, that all neutrons have exactly the same mass and no charge, and that all electrons have exactly the same mass and charge. Is this an artificiality indication?
It could be that these things I have mentioned are artificiality indications, clues that our universe is something like an artificial or simulated universe. The fact that the universe seems to be 13 billion years old is no proof that it is. It could be that things such as the cosmic background radiation and dinosaur fossils are just part of a kind of “backstory” plugged into our universe to “flesh out the simulation.”
Going back to the “Stopover in a Quiet Town” scenario, imagine the perplexed couple wandering around the town comes across a plaque in the town that looks like this:
Would this sign prove that the town was actually founded in 1745, burnt in the War of 1812, and visited by Abraham Lincoln? No, in this scenario the sign is just a bit of “backstory” provided to flesh out the simulation. Similarly, some things that our scientists take so seriously such as the cosmic background radiation or dinosaur fossils may be just things thrown into an artificial universe to “flesh out the simulation” by providing some “backstory” suggesting a past of a certain type.
If our universe is in some sense artificial or simulated, then we cannot tell how old it is, cannot tell how much matter it has, and cannot even tell whether it even has matter. The universe could mainly just be a substrate or kind of arena for the experiences of creatures such as us, and may have no reality outside of our minds.
Our scientists have such faith in their calculations of the universe's age, but this may be unwarranted overconfidence. Let's imagine an interesting scenario. Let's imagine that in the year 2500 some power (extraterrestrial or supernatural) creates an artificial zoo-like environment for humans (enclosed by a ring of high cliffs), and that such a power then creates some adult humans and puts them in this environment. We might imagine that the humans, the trees, and the grass were created either through some miracle or through some fancy genetic technology.
We can then imagine that these newly created humans might try to calculate how old their environment is. They might take some seeds from a high tree, plant the seeds, watch how fast the newly planted tree grows, and do a projection, which might lead them to believe their environment is at least 100 years old (based on the high trees they observe). They might also bear a child, and project from the child's growth rate that they must be at least 20 years old. The humans might then confidently proclaim (in the year 2503) that they had scientifically double-proven that they must be living in an environment at least 20 years old. But this would not be accurate, since their environment would actually have been created only 3 years ago, in 2500. The point of this thought experiment is: age calculations cannot be reliably done in an environment that is artificial or simulated. The possibility of an artificial or simulated universe means we cannot really be very confident that our universe has been around for 13 billion years. We can merely say that we have a method of calculating the universe's age that suggests such a conclusion.
People nowadays often ask, “Is the universe a computer simulation?” But that is too narrow a question to be asking. A computer-simulated universe is only one type of artificial universe, and there are many other types of artificial universes we can imagine. The broader question we should be asking is: is our universe something artificial that reflects the purpose of some higher intelligence?