Do We Live in a Simulation? Chances Are about 50–50

Living in a Simulated Universe

John D. Barrow

Once you take seriously that all possible universes can (or do) exist then a slippery
slope opens up before you. It has long been recognised that technical civilisations, only a
little more advanced than ourselves, will have the capability to simulate universes in
which self-conscious entities can emerge and communicate with one another2. They
would have computer power that differed from ours by a vast factor. Instead of merely
simulating their weather or the formation of galaxies, like we do, they would be able to
go further and watch the appearance of stars and planetary systems. Then, having coupled
the rules of biochemistry into their astronomical simulations they would be able to watch
the evolution of life and consciousness (all speeded up to occur on whatever timescale
was convenient for them). Just as we watch the life cycles of fruit flies they would be
able to follow the evolution of life, watch civilisations grow and communicate with each
other, argue about whether there existed a Great Programmer in the Sky who created their
Universe and who could intervene at will in defiance of the laws of Nature they
habitually observed.

Faced with these perplexities do we have any chance of winnowing fake realities from
true? What we might expect to see if we made scientific observations from within a
simulated reality?

We might also expect that simulated realities would possess a similar level of
maximum computational complexity across the board. The simulated creatures should
have a similar complexity to the most complex simulated non-living structures—
something that Stephen Wolfram8 (for quite different reasons, nothing to do with
simulated realities) has coined the Principle of Computational Equivalence.