When I was younger I used to wonder how I could know if the reality I perceived was the same thing that other people perceived. In Philosophy 101 I found out that this is actually a fairly common question – when you see something that’s red, for example, how do I know that it’s making the same impression on your brain that it does on mine (sorry – I remember the question, but I can’t remember the answer the professor gave us)? So – it’s interesting to wonder if my perceptions of the universe are the same as yours, but a recent scientific paper by physicists Silas Beane, Zohreh Davoudi, and Martin Savage takes things a little further and asks if the universe is even real, or if it (and everything in it, including us) might actually be a very sophisticated computer simulation.
On the face of it the question sounds sort of nutty – obviously the world and the universe we see around us are real because we interact with our world and we observe the universe directly. How, for example, can I deny the reality of the keys I am now typing on, or the solidity of the chair I’m sitting on, or the sight and sound of the television program I’m watching. On the other hand….
First, consider that what we consider “solid” objects are mostly empty space – well over 99.9% of the mass in every atom is concentrated in the nucleus, which is surrounded at a relatively great distance by the electrons. The volume of an atom taken up by the nucleus is minuscule – an analogy has been made to a fly buzzing around in the Astrodome. Every bit of “solid” matter with which we interact is almost entirely empty space. And the solidity part is also interesting – when I walk across the floor (or sit in my chair or grab onto a glass) the contact between my fingers and the solid object is actually the electrostatic repulsion between the outmost electrons surrounding the atoms that comprise my fingers and those surrounding the outermost electrons in whatever it is that I’m holding or walking or sitting on. So the reality of the solid objects in our lives is sort of shaky – the apparent solidity is as much illusion as it is reality.
So – solid objects are really mostly empty space and contact with a solid object is really just electrons repelling each other. But beyond that, there is also ample evidence that what our senses tell us is a sort of edited reality – our brain, for example, fills in the gaps in our vision to show us what ought to be there, even if some visual information is missing. Not to mention that our brain helps to filter out extraneous noise – all of our perceptions of the world around us are filtered through our nerves, our central nervous system, and the way that our brains process all of this information. For all we know, we could be living entirely within our heads with our brains simply imagining all of our interactions with the world – a sort of self-contained Matrix-like universe. Having said that, I doubt that this is the case, but on the other hand, I know that I’ve had some pretty realistic dreams – who’s to say how much of what I think I sense is actually illusory. The only way to make sure is to think of a sort of test to help differentiate between the universe we all think we live in versus one that exists only in our minds. Beane, Davoudi, and Savage note (as have others) the dramatic increases in computer capabilities over the last few decades and, projecting these trends forward, have come to the conclusion that the computers of the not-so-distant future are likely to have the capability of simulating an entire universe – including its inhabitants and their thoughts, feelings, and sensory perceptions.
So let’s get back to the paper mentioned at the start of this posting. Going back a decade, philosopher Nick Bostrom published an interesting paper in Philosophical Quarterly in which he offered three suggestions and argued that at least one must be true: that humanity is likely to go extinct before reaching a “posthuman” stage, that posthuman civilizations are unlikely to run computer simulations of their past, or that everything we consider to be our reality is in actuality a massive computer simulation. And of these possibilities, Bostrom suggests there could be a whole series of nested computer simulations (i.e. the “real” species simulates a universe on their computers and virtual beings in that universe write their own simulation, and so forth) and further suggests it is unlikely that we are at the head of this chain. To Bostrom it is more likely that we and the universe we see around us are computer simulations (possibly one level of a long series of simulations) than that we are at the head of the line. Beane, Davoudi, and Savage’s paper posits ways that Bostrom’s suggestion can be tested.
I’ve got to admit that I can’t follow the mathematics or most of the physics employed by Beane and his colleagues – to some extent I’ve got to push the “I believe” button and to assume that their math and science are solid. And the one example that I am familiar with is intriguing – they suggest that some irregularities we have observed in the distribution of energies among the most powerful cosmic rays could be an indication that what we perceive as reality might be a computer simulation.
So we’ve got to ask ourselves – does it matter if we are “real” or if we inhabit a sophisticated computer simulation? I’ve given it a lot of thought and, to a large extent, I’ve concluded that it doesn’t matter much to me. Whether “real” or virtual, the universe I inhabit seems to make sense; it’s all that I know, it seems to work and to make sense, and it seems to be self-consistent. If this is a simulation, I can’t tell the difference between it and reality. If it turns out that Beane and his colleagues are correct then we might someday figure it out – maybe even (as they put it) “for the simulated to discover the simulators.”
On another note, this will be the last ScienceWonk posting of 2012 as I’ll be taking next week off. Happy Holidays, everyone, and thanks for taking the time to log in, read, and to post thoughtful comments!