Right
at this very moment, scientists are working on realistic simulations of our
universe. What if, at some point, a simulation gets so good that it gives rise
to our solar system, our planet, and our species? Even more interesting, what
if that's already happened and we're living in that very simulation? Many
popular figures think this isn't just possible, but likely, while others say
it's next to impossible. Who's right?
The
most popular argument for what's known as the simulation hypothesis came from
University of Oxford philosopher Nick Bostrom. In a 2003 paper, he put it this
way: "If there were a substantial chance that our civilization will ever
get to the posthuman stage and run many ancestor‐simulations,
then how come you are not living in such a simulation?" He followed that
up with a Fermi-paradox-esque formula laying out the likely number of all
"observers with human-type experiences" — people like you and me —
based on the number of civilizations that survive to reach a
"posthuman" stage, the number of simulations those civilizations
would run, and the number of actual people that lived in one of those
civilizations.
Proponents
say that it's more than just a matter of probability. The laws of physics don't
seem that different from code in a program, according to some, and it's likely
that with enough time, a sufficiently advanced civilization could crunch the
numbers and produce a simulation that mimics the existence and behavior of
every particle in our universe.
MIT
cosmologist Max Tegmark is one of those proponents. "If you look at how
these quarks move around, the rules are entirely mathematical as far as we can
tell," he said at the 2016 Isaac Asimov Memorial Debate on the topic.
"If I were a character in a computer game ... I would also discover
eventually that the rules seemed completely rigid and mathematical. I would
just be discovering the computer program in which it was written. So, that kind
of begs the question: How can I be sure that this mathematical reality isn't
actually some kind of game or simulation?"
Sim
Shady
But
others are staunchly against the idea — theoretical physicist Sabine
Hossenfelder, for one. In March of 2017, she published a post on her blog
Backreaction plainly titled, "No, we probably don't live in a computer
simulation." "Among physicists, the simulation hypothesis is not
popular and that's for a good reason — we know that it is difficult to find
consistent explanations for our observations," she wrote. "After all,
finding consistent explanations is what we get paid to do."
Once
you start digging into the details, Hossenfelder says, the hypothesis falls
apart. If the universe is a computer simulation, then it must be made of bits
like any computer program. But what kind of bits? Classical physics (the
physics of the big) and quantum mechanics (the physics of the small) don't play
well together in our universe. If you use bits that work on classical physics,
they won't produce quantum effects. You'd have to use quantum bits, or qubits.
In fact, Perimeter Institute physicist Xiao-Gang Wen has tried doing that exact
thing to model the universe, but his models don't jibe with Einstein's theory
of relativity.
"Our
presently best theories are the standard model and general relativity, and
whatever other explanation you have for our observations must first be able to
reproduce these theories' achievements," Hossenfelder concludes.
"'The programmer did it' isn't science. It's not even pseudoscience. It's
just words."
That
might be the biggest problem with the simulation hypothesis: it's not actually
possible to prove it wrong, and that puts it outside of the realm of science.
"We're certainly not going to get conclusive experimental proof that
you're not in a simulation," NYU philosophy professor David Chalmers said
at the 2016 debate. "Because any evidence that we could ever get could be
simulated."
Even
some who disagree with Hossenfelder agree on this point. "...I agree with
Sabine insofar as she argues that the simulation hypothesis is lazy,"
theoretical computer scientist Scott Aaronson wrote on his blog at the time.
"...it doesn't pay its rent by doing real explanatory work, doesn't even
engage much with any of the deep things we've learned about the physical world."
But Aaronson still thinks it's possible. "Blame it for being unfalsifiable
rather than for being falsified!" he wrote.
If
this is all starting to sound a bit more like religion than science, you're
onto something. In that case, perhaps Tegmark's simulated version of Pascal's
Wager will have some appeal. In the 1600s, French philosopher Blaise Pascal
pointed out that it's in our best interest to behave as if God exists, since if
he doesn't exist and you behave as if he does, you don't lose much — but you
lose everything with the alternative. Tegmark said something similar in 2016:
"My advice to you is go out there and live really interesting lives and do
unexpected things so the simulators don't shut you down." There are
certainly worse ways to live.
To
read more from the man who popularized the simulation hypothesis, check out
"Superintelligence: Paths, Dangers, Strategies" by Nick Bostrom,
which is all about what might happen when the robots surpass us in
intelligence. We handpick reading recommendations we think you may like. If you
choose to make a purchase, Curiosity will get a share of the sale.
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